Switching careers from physics to aviation

It's one of those things about the flying game that the actual details of previous education and experience outside of aviation count for relatively little, other than what they may indicate about someone's personality, worldview and leadership potential going forward.  This is because the knowledge base and skill set are unique to the trade.
I used to know a Capt of a major carrier who was on a selection board, and he told me once that the only real reason airlines expect a university degree is that it provides a higher than average probability that a candidate will be able to handle the firehose flow of information that a pilot has to deal with on an initial type course.  What the degree was actually for was not that important as long it was demanding to some extent (not those "XXX studies" degrees).
If someone is hiring a pilot, they want to know about flying experience, personal attitude, character, and very importantly, leadership potential (since in the long run they are expecting the candidate to be in command of a crew at some point).  Previous non-aviation experience that establishes strong leadership potential (the leadership ideal fostered by Crew Resource Management theory specifically) probably has a stronger effect on your desirability as a candidate that any particular technical background.
Now, if you get into a flying career and at some future point, where you have ample flying experience, you apply for a job posting for, say, a production test pilot with an OEM, or something similar at an airline, which is likely to have a dual engineering/flying function, then the physics/engineering background might count for quite a lot.
But at the start, it mostly indicates to a potential employer that you have an above average ability to absorb information, so it can't hurt, but don't expect much more than that.


On IMA systems e.g. A380 how many people are required to preform regular maintenance checks on this system?

Not any more people than any other system. But your question raises a few key points for consideration.
First of all, maintainers don't actually go anywhere near the aircraft if it is not a requirement. I don't agree that there are usually 1 or 2 engineers on an aircraft at any given moment. If it aint broke, don't fix it. Over-maintenance is a cause of systems breaking more often due to factors such as human error, more cycles that could reduce life, etc. So unless there is a reason to be there, they won't be pushing buttons just to see if something is still working. In fact, your foreman/chief would probably ask you why you were touching that aircraft. Valid reasons to be working on the aircraft are most often that the maintenance is called for in the servicing schedule (scheduled maintenance), or it has broken (unscheduled maintenance). There are other exceptions to this including modifications and special technical instructions. These will have slightly different names depending on the local authority under which the aircraft operates.
Second point is that if you have been granted authority, have the current licence and the company policy allows for it, you may be able to perform maintenance by yourself. However, airliners usually (at least in Australia) have an AME (aircraft maintenance engineer) do the work and sign the first level of certification, followed by a LAME (Licenced Aircraft Maintenance Engineer) who certifies that the work was completed in accordance with the approved procedure and issues a certificate of release. This allows the aircraft to go flying again. In general aviation, it is more common for the LAME to do the work by themselves. In this case, they are kind of supervising themselves.
Third point: The complexity of the aircraft's system does not determine the number of "levels" of certification. If anything, it is how safety critical the system is to airworthiness that determines how many people must sign for the job. In some cases, an IMI (Independent Maintenance Inspection) or QA (Quality Assurance Inspection) is called for, increasing the levels to 3. Systems such as landing gear are pretty important so they may have 3 levels, but this isn't always the case. The levels are 1-AME, 2-LAME, 3-Independant. I don't think I've heard of Integrated Modular Avionics requiring 3 levels. As a training manager, I'd just make sure my people have adequate training and are confident. If they aren't confident, part of getting your LAME licence is knowing when to put your hand up and say you can't do something. Much safer to do that than guess what you are doing is correct. Hundreds of lives are at stake. You need to have the knowledge and maturity to be a good engineer.
Another interesting point worth bringing up: The Royal Australian Navy had a Sea King helicopter crash leading to loss of lives during Operation Sumatra Assist. This was for the 2004 tsunami. The cause was the lack of a split pin that should have been installed on the main rotor hub assembly. Long story short, the Navy increased the levels of inspection of this job (and others similar to it) from 3 to 4. Data showed that after this change was implemented, more mistakes happened, which is a bit counter-intuitive. You would think that by having 4 people look at something that it would be safer. Wrong. Data showed that people became more complacent because they thought that someone else would have their back if they were having a bad day. The Navy reverted back to 3 levels, and incidents reduced again.
IMA systems (I assume you mean Integrated Modular Avionics) aren't any more complex than aircraft without it. For anyone who is wondering what IMA is, it is basically a concept of merging what used to me a bunch of separate computer systems into a reduced number of boxes. That way the systems can share computing power. On the 787 these are called CPIOMs (Central Processing Input Output Modules). They've managed to reduce the physical footprint and weight of the entire avionics package than pre IMA concepts. There's actually a good argument to say that it is now simpler, because there are less boxes to maintain than before. System testing (BITE) is still done via an interface in the cockpit and is as easy as before.


Can I land a helicopter by controlling only power, not angle of attack?

Assuming you mean a manual thrust lever with out a constant speed regulator: yes that is possible but not optimal. Best is to keep the rotor blades at optimum speed and reduce AoA of the blades by lowering collective - if you do that the thrust needs to be adjusted otherwise the rotor overspeeds, but it is still better this way than reducing thrust/rotor speed first.

If rotor speed is slowed down first, the blade speed reduces and with the collective at the same setting, the blade AoA will increase. So the safety margin with stall AoA decreases, at a time when it is required most.

Possible - yes. Recommendable - no.


Could the GPS be used to aid the autopilot with speed?

The main issue is that we can only get groundspeed from GPS data. Winds aloft aren't known exactly at a particular place, so they could be rather inaccurate -- certainly not enough to leave to the hands of the autopilot. The decision to use GPS data to verify airspeed would lie in the hands of the crew. Anyway, they were too preoccupied to go and check that their ground speed was sort of accurate.

It's not uncommon for winds aloft to reach speeds between 180 and 200 knots. While previous weather reports can be useful, winds can change quite frequently -- the chances of the wind changing is much more than the chances of all the sources of airspeed becoming unreliable.

GPS data is also not 100% accurate, so keep that in mind, especially if only some of the sattelites can be reached.

What the crash came down to was mainly a loss of situational awareness, combined with their lack of experience with actual stall recovery, was the main contributing factor to the accident.


Why does a jet's combustion energy propel the engine forwards rather than acting equally in all directions to create zero thrust?

The layperson answer is:
You are making air expand in a contained space but giving it an escape path in a particular direction that is easier to take than making the container blow up.  When I was a kid and it was possible for kids to buy firecrackers from the corner store, I used to like to make rockets out of them to propel balsa gliders.  You rolled the end of the firecracker between your fingers to make the packing fall out so it was open at one end, and taped it to your glider.  When the fuse burned down and the gun powder lit off (just after you threw the glider), the expanding gases went out the open end, making a nice rocket that ran about a second.  Close off the open end, like a normal firecracker, so the gases have nowhere to go, and it blew up (which would occasionally destroy my gliders when I didn't roll out enough of the packing - good thing they only cost a dime in 1967).
So air is being made to expand and you give it somewhere to go.  Since the front end is open as well, why it doesn't go back out the front is simply because the engine is packing in air from that direction faster and harder than the burning air can push back, relative to its fairly easy path out the tail pipe, so it takes the "easy way out" (jet engines can back flow if things go off kilter - you will sometimes see flames coming out the front during "stall/surge" events).
In taking the easy way out, it's still has to accelerate to high velocity to make it through an opening that is constricted, and there's your Newtonian thrust reaction.
The last part is, you put a windmill, a turbine, in the high velocity flow and use the windmill to drive a compressor to keep the air being packed in at the front.  You are extracting some of the energy in the flow going out the turbine section to power air-packing equipment at the other end, to keep the cycle going by itself without any external help.  Basically you are redirecting a part of the energy of the burning fuel air mixture to keep the cycle going instead of making thrust.
In a piston engine, you have a similar energy transfer effect, in a radically different format, to self-sustain the cycle. Air burns in a cylinder's combustion chamber and forces the piston down to drive a propeller, but some of that rotation energy is being used to drive the adjacent piston on its compression stroke, redirecting a part of the energy of the burning fuel air mixture to keep the cycle going instead of making torque at the prop.
The jet engine does the same thing in a linear fashion using aerodynamic forces instead of closed spaces inside cylinders, depending on the inertia and velocity of the flow (like a hallway packed with people running in one direction - forget about trying to run the other way) to channel all of the forces where they need to go to keep the cycle going.


How does the FAA define fuel capacity for ultralights?

FAA Advisory Circular AC 103-7, Paragraph 19 has this to say:

  MAXIMUM FUEL CAPACITY OF A POWERED ULTRALIGHT VEHICLE.

  The maximum fuel capacity for a powered ultralight vehicle is 5 U.S.
  gallons. Any
  powered  ultralight with fuel tank(s) exceeding this capacity is
  ineligible for operation as an ultralight vehicle.

  a. Determination of Fuel Capacity.

  The total volume, including all  available space for
  usable and unusable fuel in the fuel tank or tanks on the  vehicle is
  the mtal fuel capacity. The fuel in the lines, pump, strainer, and
  carburetor is not considered in a calculation of total volume.


Why is this airfoil curved upwards on the bottom part of the airfoil?

Downwash is simply the deflection of air due to airfoil (or wing etc.)

Symmetric airfoils don't produce downwash (or lift) at zero angle of attack.

Source: oppositelock.kinja.com

However, as the angle of attack is increased, the (symmetric) airfoil produces both.

Source: Effect of angle of attack on flow field and body forces by Paul Nathan from youtube.com

Symmetrical airfoils are used in rotary wing applications, vertical tail (and rudder) etc.


What are the guidelines for call signs for aircraft dealing with US ATC?

According to JO 7210.3Y, Air Traffic Organisation Policy, section 4-4-2 there are several requirements from both the FAA and FCC. The FAA requirements are (paraphrased from the JO):

Comply with FCC regulations (remember that the FCC is responsible for radio communication technical regulations, not the FAA)
Get FAA approval "to avoid possible duplication or conflict
with air−ground call signs assigned on a national
basis to other aircraft operators"

The FCC requirements are in 47 CFR 87.107 (not 87.115 as the JO says):

  (a) Aircraft station. Identify by one of the following means:

  (1) Aircraft radio station call sign.

  (2) The type of aircraft followed by the characters of the
  registration marking (“N” number) of the aircraft, omitting the prefix
  letter “N.” When communication is initiated by a ground station, an
  aircraft station may use the type of aircraft followed by the last
  three characters of the registration marking. Notwithstanding any
  other provision of this section, an aircraft being moved by
  maintenance personnel from one location in an airport to another
  location in that airport may be identified by a station identification
  consisting of the name of the company owning or operating the
  aircraft, followed by the word “Maintenance” and additional
  alphanumeric characters of the licensee's choosing.

  (3) The FAA assigned radiotelephony designator of the aircraft
  operating organization followed by the flight identification number.

  (4) An aircraft identification approved by the FAA for use by aircraft
  stations participating in an organized flying activity of short
  duration.

In other words, your call sign must be approved in advance by the FAA, otherwise you can't legally use it per FCC regulations. In reality, if you call up ATC as Little Piggy 27 you'll either get a laugh and a "no, seriously?" or - in the worst case - you'll just annoy them.

There are also military call signs in use but I know nothing about them. I do remember being in the pattern while an Air National Guard aircraft out of Memphis, TN was doing touch and goes using the call sign Elvis 1. But I have no idea how that call sign was set up between the ANG and FAA.


What are the specific side step minimums for an approach?

KSFO has sidestep minima for ILS/LOC 28R to 28L but not from ILS/LOC 28L to 28R.  It also has a sidestep from ILS/LOC 19L to 19R but no ILS at all for 19R itself.  The latter is probably the more normal case for sidesteps: giving a second runway (probably one normally only used for departures) lower minima than circling without needing to install and maintain another entire ILS setup that would rarely be used.  Notice that the first two also have (much higher) circling minima.

KDFW has sidestep minima for ILS/LOC 35L to 35C, ILS/LOC 35C to 35L, ILS/LOC 36L to 36R, ILS/LOC 36R to 36L, and all their opposites.  Since all the sidestep targets have an ILS of their own, this seems to be intended only for when one of them is out of service, i.e. not for normal usage.


What is the German / European equivalent of FAA Order 7110.65?

The „handbook“ for ATCOs in Germany (!) is the MO-ATS (Manual of Operations for Air Traffic Services) which is an internal DFS (Deutsche Flugsicherung - the German ANSP) document and therefore not available to public.

However it is based on the German AIP and ICAO DOC 4444 which are both available to public. For the international legislation check Milo Morkus’ answer.

In the German AIP phraseology examples are found in AIP ED GEN 3.4 Communication Services


Are all engines fan blades made out of titanium?

Many, but not all. Rolls-Royce has been working on carbon fibre fan blades for a long time, using the material as far back as 1968 on the RR. Conway. They planned to use carbon fibre (Hyfil) for the RB.211 too, but had to switch to titanium when they couldn't get the Hyfil blades to work reliably during bird ingestion tests.

The GE90 uses carbon fibre fan blades, with titanium leading edges.


What are the pros and cons of having a side-stick versus a centered control stick in a fighter aircraft?

Center mounted sticks are useful for maintaining positive control of the aircraft while operation some cockpit system on the right consoles and flying with your left hand.  It’s also useful in an emergency, say if your right arm was injured by shrapnel, etc and cannot actuate the stick effectively, requiring you to fly with your left hand.

Side sticks do have the advantage of less cockpit clutter.  The stick is mounted off to the right and doesn't directly block critical instruments from the pilot's view or have its range of motion restricted by flight gear, kneeboards, etc.

As far as size and weight are concerned, both center mounted and side sticks are pretty much the same in a fly-by-wire aircraft - just a 4-way transducer LRU with a handgrip attached to it.  In a/c with conventional control systems the center stock was a necessity as it acted as a lever arm allowing the pilot to overcome aerodynamic forces on the control surfaces with muscle power alone and one could force a maneuver using both hands.  In the age of hydraulic flight controls and fly-by-wire, this is irrelevant.

As to ergonomics, it's fairly comfortable to fly a center stick as your wrists will naturally rest on your thighs when seated and your hands naturally float to that position.  Side sticks are also comfortable but require an armrest to operate effectively, particularly when pulling Gs.


In the B737, does an IAN NPA require that the G/P is 3° or can the G/P angle vary?

The G/P can deviate from the typical 3 degrees, but not much.
For any non-precision approach (NPA) flown with VNAV or Integrated Approach Navigation (IAN), the navigation database needs to contain a stored glide path (GP) angle or a suitable waypoint (runway or MAP):

VNAV should be used only for approaches that have one of the following features:

a published GP angle on the LEGS page for the final approach segment
an RWxx waypoint coincident with the approach end of the runway
a missed approach waypoint before the approach end of the runway, (e.g.,
MXxx).

[...]
The FMC
obtains the GP angle displayed on the LEGS page from the navigation database. [...] A GP angle
is coded in the navigation database for nearly all straight-in approach procedures.
[...]
This GP angle is normally defined by the regulatory authority responsible for the
approach procedure and provides a continuous descent at a constant flight path
angle for a final approach path that complies with minimum altitudes at
intermediate step-down fixes. The typical GP angle is approximately 3.00°, but
can vary from 2.75° to 3.77°.

(Boeing 737 NG FCTM 5.45 - Approach and Missed Approach, emphasis mine)
As you can see, the GP angle can vary between 2.75 and 3.77 degrees. For IAN, this G/P information is passed on to the AFDS by the FMC. The list of IAN restrictions does not limit the GP angle:

IAN Requirements and Restrictions

airplanes must be equipped with FMC U10.5 or later and IAN FMA
displays
dual or single engine approaches are authorized
waypoints in the navigation database from the FAF onward may not be
modified
raw data monitoring is required during localizer based approaches.
During FMC based non-ILS approaches, raw data monitoring is
recommended when available in accordance with the techniques
described in the Non-ILS approach section in this chapter
QFE operation is not authorized
cold temperature altitude corrections are not permitted
RNP appropriate for the approach must be used
the autopilot is required until suitable visual reference is established when
performing an approach requiring an RNP of 0.15 or lower.

(Boeing 737 NG FCTM 5.60 - Approach and Missed Approach)
The FCTM does however says the following about when an approach can be flown with IAN:

For FMC based approaches, a proper series of legs/waypoints describing the
approach route including an appropriate vertical path or glide path (GP) angle
must appear on the LEGS page. A GP angle displayed on the LEGS page means
the vertical path complies with final approach step-down altitudes (minimum
altitude constraints). A glide path angle suitable for an IAN approach is one that
approximates 3° and crosses the runway threshold at approximately 50 feet.

(Boeing 737 NG FCTM 5.61 - Approach and Missed Approach, emphasis mine)
It does not say if the full range from 2.75 to 3.77 degrees is considered approximately 3.00°, but it certainly does not have to be exactly 3.


As the elevators rotate to get a negative pitch angle to the horizontal (moving the tip of the elevator upwards), a pressure difference is created causing it to produce a downwards force, and as a result the aircraft pivots around the landing gear, rotating upwards.
As it does so, the wing starts to generate more lift, as can be
seen on the graph below. The higher the angle of attack- the more
lift, since the lift coefficient becomes higher, up to where stall starts.
When the lift exceeds the weight, the aircraft will lift off.

For taildraggers, the tail is normally rotated up at a low speed while the aircraft continues to accelerate, and once a sufficient speed is reached, the tail surface is again lowered, causing the wing to increase the AoA and to lift. Footnote: If I'm not mistaken, this is more of an act to improve control and reduce drag, since at some point the aircraft will lift off on it's own with it's tail-down angle of attack.


How does the cabin pressure controller work in a large commercial airliner?

The System you are referring to is described in ATA chapter 21. I will report here an example for A320

An overview of the system is reported below (from the ATA21 report):

  What is the source of pressure reference?

In flight the outside pressure signal can be come from either:

The Air Data Reference System (ADIRS), for the pressure altitude.
The Flight Management and Guidance Computer (FMGC), for the landing elevation.

If FMGC not available, uses the landing elevation from the ADIRS and the landing elevation

  How the different valves (outflow, relief) and the packs are related to the CPC?

There are two independent safety valves controlled by two independent Cabin Pressure Controllers (CPC) and actuated by three independent motors.
 The pressure in the cabin is controlled only with these valves, while the temperature of the cabin is controlled by mixing the air from the packs with the one of the cabin. In particular the valves are opened and closed to keep the desired pressure profile according to the logic dictated by the different flight phase. .

Different constraint drive the controller:

Cabin pressure at cruise altitudes is limited to an equivalent ISA pressure of 8000ft, due to structural fuselage requirements. By providing higher pressures levels (equivalent to lower ISA equivalent altitudes, e.g.: sea level) the fuselage would overstrain. A (very) simplified example  of this is a balloon in a vacuum chamber.
Maximum descent rate is kept under 750 ft/min for passenger comfort. Otherwise your internal ear starts hurting.
At take-off on ground the cabin is de-pressurized till -0.1 psi with a max rate of 400ft/min to avoid pressure surge at rotation

  When and how is used the manual control of the pressure?

Manual control of the pressure is used when both the CBC controllers fail or when the crew uses the cabin press control panel, that you showed. In case of aircraft ditching the inlets are closed as well with a ditching button (first image, right in the CABIN PRESS panel)


Autogyro blades have a higher airspeed than the aircraft that is carrying them, so they can generate lift even when the aircraft speed is low. They fly as if they had a wing the size of the whole disk, not just the blade area - yet can be stored or transported easily.

They can land (but not take off) almost vertically, which is a useful safety feature in the event of an engine failure.

Having said that, they aren't common because they don't do anything useful significantly better than the other options, except perhaps being 'different and interesting'. Flying slowly isn't terribly useful.


Why would different crossing runways at one airport be on different radio frequencies?

That division is applicable only when the parallels (4's or 22's) are in use, which is the preferential system (see title of chart).

As for rwy 12/30, from the eAIP (PDF; link may die; homepage):

Between 6 AM and 11 PM local:

  RWY 12 and RWY 30 may be used when one or both of the preferential runways cannot be used (...)

Between 11 PM and 6 AM local:

  RWY 12 and RWY 30 are closed for take-off and landing, however, RWY 30 may be used for landings when the crosswind component on the preferential runways exceeds 15 KT or the preferential runways are not available due to disabled aircraft, snow clearance, work on the runways, etc.

Once 12/30 is in use, that chart does not apply. Further:

  During periods with low traffic intensity one or two positions may be responsible for all three area, but apron service will be provided on three separated frequencies simultaneously. The frequencies will be combined by ATC. [emphasis added]


What is the small cylinder on the firewall to the left of the battery?

That is a fuseholder for the optional clock or optional Hobbs meter. The yellow wire probably should be connected to it but you should have a certified mechanic inspect it.


Why are "Follow Me" cars painted yellow and black?

Yellow and black together are highly visible in any light, especially if there are sharp, straight lines between them; our eyes are drawn to that combo and our brains are evolved to recognize it as a danger. Think of bumblebees.

Stationary objects tend to be painted white and red for similar reasons.


Would it be possible to build a "rocket" using a series of ducted fans?

From the link you provided:

  Specification:

  Rotor Diameter: 90mm
  Fan blades:11 blades
  Weight: about 350g
  Working Voltage:6s(22.2V) lipo battery
  Motor:Brushless Motor 3553 1450kv
  No Load Current: 4.1 A
  Load Current: 83A
  No Load Speed:32190 rpm
  Load Speed:16095 rpm
  Thrust: 3300g
  G/A:45.16

Assuming that 16 * 6/4 = 24 18650 cells would be able to deliver full electrical power for the fan, the issue would be indeed be the local angle of attack of the fan blades.

Thrust at full power is listed at 3.3 kg = 32 N. This would be at standstill/hovering conditions at sea level, since measuring at that level provides the highest thrust level for advertisements. Diameter is 0.09m. Net thrust T =

$$ T = \dot{m} \cdot (V_{out} - V_{in}) = \dot{m} \cdot \Delta V \tag{1}$$

$$ \dot{m} = \rho \cdot A \cdot V \tag{2} $$

Combining (1) and (2) for the hover, with $V_{in}$ = 0:

$$ V = \sqrt{\frac{T}{\rho \cdot A}} = \sqrt{\frac{32}{1.225 \cdot \pi/4\cdot0.09^2}} = ~\text{64 m/s}$$

Impulse thrust considerations usually draw a contracting propeller wake for inducted propellers. Ducted fans work a bit differently and we can take the average velocity behind the fan for further Order Of Magnituding. Below figure is from this research paper, and shows the considerations for ducted fan flow; it contains some methods for more detailed computations.

Rotational speed under load is 16095 rpm = 1,684 rad/s, tip speed = 0.045 * 1,684 = 75.8 m/s. A velocity triangle at the blade tip has as angle $ tan^{-1} (64/75.8) = 40 $ deg. The blade needs to be inclined further than that, usually about 6 deg, so tip blade angle of the standard fan would be 46 deg. Purchasing the actual fan for verifying the above would be a good thing!

For the second fan, this same method can be followed: mass stream will remain the same if the hull is closed, in order for the 2nd fan to deliver the same thrust $\Delta V$ = 64 => ${V_{}out} = 64 + 64 = 128 $ m/s. Tip angle velocity triangle = $ tan^{-1} (128/75.8) = 59.4 $ deg, fan blade angle = 59.4 + 6 = 66 deg, etc.

Note that the above is valid for the hover. As soon as the "rocket" picks up speed, the local angle of attack of the fan blades will reduce and therefore thrust will reduce. So one would have to optimise time of thrust (time of amps delivered) with weight, momentary speed, and expected end speed, then average the blade angles out for the speed function.

Note that opening the hull in between the fans allows for extra air to be drawn in, increasing the mass flow. The paper cited above has results for a setup like that as well - if the increased mass flow relates in lower entry velocity, this might be worth considering.


What do you need to know to fly a Cessna?

You're on the right track, but let your instructor guide you along the path of righteousness or you'll end up thinking about all the stuff rattling around in your head instead of listening to what they're telling you while they're trying to show you how to fly. Day 1 is largely just familiarization - you're not going to need to know all that detail. They'll have a syllabus that will include everything you need to know, and they should be able to guide you on what'll be good to focus on for the upcoming lessons.  The private pilot practical test standards are a great preview of what will (eventually) be expected, and if your ground school works you should be through the written and aware of any weak academic areas soon enough to correct any knowledge deficiencies that may bear on your flight training.  Definitely read the POH cover to cover so you know what's in there (but you don't have to memorize it all!), and ask your instructor about anything that doesn't make sense.  Listening to the tower on a handheld or through LiveATC.net may be useful (you'll find they're probably doing the same thing over and over and over) to understand what to expect, and the Aeronautical Information Manual is full of useful information that may go beyond what was specifically covered in ground school or on the written.  ATIS and/or ASOS/AWOS broadcasts are usually available on the phone, so listen to them until you "get" it all.  That should save time in the airplane.

The instructor should also cover checklist procedures, and will know what local examiners expect you to do to pass.


Can a pilot use their GPS/FMS to fly a VOR or NDB approach?

In the US they can (Effective: May 26, 2016).
This change allows for the use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure (IAP) based on a VOR, TACAN, or NDB signal. The underlying NAVAID must be operational and monitored for the final segment course alignment.

Still can’t fly an ILS or localizer approaches.

Update: 2017-04-19 Max Trescott has a good explanation of how to use GPS in conjunction with ground-based navaids on ILS and VOR approaches.

  AIM Section 2. Performance−Based Navigation (PBN) and Area Navigation
  (RNAV)

  1−2−3. Use of Suitable Area Navigation (RNAV) Systems on Conventional
  Procedures and Routes

  Use of a suitable RNAV system as an Alternate Means of Navigation when a VOR, DME, VORTAC, VOR/DME, TACAN, NDB, or compass locator
  facility including locator outer marker and locator middle marker is
  operational and the respective aircraft is equipped with operational
  navigation equipment that is compatible with conventional navaids. For
  example, if equipped with a suitable RNAV system, a pilot may fly a
  procedure or route based on operational VOR using that RNAV system
  without monitoring the VOR.

  NOTE−
  4. The navigation database should be current for the duration of the flight.

  c. Uses of Suitable RNAV Systems. Subject to the operating
  requirements, operators may use a suitable RNAV system in the
  following ways.
    1. Determine aircraft position relative to, or distance from a VOR (“VOR” includes VOR, VOR/DME, and VORTAC facilities and “compass
  locator” includes locator outer marker and locator middle marker.),
  TACAN, NDB, compass locator, DME fix; or a named fix defined by a VOR
  radial, TACAN course, NDB bearing, or compass locator bearing
  intersecting a VOR or localizer course.

  Navigate to or from a VOR, TACAN, NDB, or compass locator.
  Hold over a VOR, TACAN, NDB, compass locator, or DME fix.
  Fly an arc based upon DME.

None of the substitutions mentioned above include the localizer portion of an ILS. So you may not substitute GPS/WAAS for and ILS or localizer approach, but you may still use it for situational awareness.

You need to dig into the AIM to find out what they mean by “suitable RNAV system” but basically both certified GPS or WAAS count.


The three competing supersonic designs are discussed in this video – The Forgotten American Concordes. Two competing designs from the USA were proposed to the US government, which was going to fund 75% of the development cost: one from Lockheed, and the B2707 from Boeing which was the winning design.

The B2707 was meant to be bigger and faster than Concorde, and this was one of the three issues that eventually saw the project being cancelled:

Concorde flew at Mach 2, heating up the nose to 127 °C and the wing leading edges to 100 °C. The whole plane was considerably longer at cruise than it was on the runway due to heating up from the supersonic flow, but at this speed aluminium could still be used as the main construction material for most of aeroplane. The B2707 would be heating up much more, ruling out aluminium and having to use titanium, skyrocketing the construction price per aeroplane.
The oil crisis of the early 70s raised fuel prices a lot, with unfavourable consequences for the operating costs. It was thought that since the travel time is shorter there could be more daily flights, but:
protests about supersonic booms prohibited supersonic flights over most land, meaning that the only viable market was the US east coast to the European west coast.

  If so, what was the problem with the design? By problems, I don't mean it being financially feasible or sustainable, I mean technical limitations and restrictions imposed by physics. Could this sort of aircraft ever have achieved a sustained mach 2.7, and carry 277 passengers?

Image source

It might have, there were military aeroplanes flying at M 2.7 or faster at the time like the XB-70 Valkyrie built out of stainless steel, but the technology was still immature. Passenger transport implies high reliability and long testing times to verify if the safety requirements can be met, and this was a major issue to be crossed out at the time of cancellation.

So the question: "Could this sort of aircraft ever have achieved a sustained mach 2.7" at the required reliability rate was never tested.


Where is this VFR reporting point ("Water Tank" near Thousand Oaks, CA) in real life?

The tank is west of Oak Park (Oak Park Canyon), but there is some conflicting information about the exact coordinates of VPLWT.

From FAA JO 7350.8P:

  34-10-49.0000N 118-46-16.0000W.

Converted into decimal degrees: 34.18028°N 118.7711°W

Google Maps

Obviously no tank here!

As @ymb pointed out, this document has been cancelled, and in the current version (JO 7350.9N), the coordinates have changed:

  34-11-01.0000N 118-46-41.0000W.

Converted into decimal degrees: 34.18361°N 118.7781°W

Google Maps

An underground tank, well visible from the sky. The tank itself is likely similar to this (it may be it, but not sure):

"Local officials recently toured and inspected the new Oak Canyon water tank under construction in Oak Park", source

Other tanks

There are also two external tanks in the neighborhood, but none corresponds to FAA coordinates, e.g. this one:

Google Maps

which is a bit north of the underground tank. Overall picture:

Google Maps

It seems FAA has not done a good job about this waypoint identification. While the current source identifies a tank, it should be mentioned this tank is underground, as this makes a difference.


Why does one of the Boeing 777's spoilers deploy differently from the rest?

Roll control is provided by 2 flaperons, 2 ailerons, and 14 spoilers.

Spoiler panels 4 and 11 are controlled mechanically rather than electrically. They are driven directly from control wheel deflections via a control cable. In case of compete electrical loss, limited roll control is available until the electrical system is restored.  This probably explains the difference in rigging.

Spoiler panels 4 and 11 are also used as speedbrakes, both in the air and on the ground. The speedbrake function for this spoiler pair only has two positions: stowed and fully extended. The speedbrake commands for spoilers 4 and 11 are electrical in nature, with an ACE (actuator control electronics) giving an extend or retract command to a solenoid operated valve in each of the actuators.

Once that spoiler pair has been deployed by a speedbrake command, there is no control wheel speedbrake command mixing, as there is on all the other fly-by-wire spoiler surfaces.

Boeing B-777: Fly-ByWire
Flight Controls


What was the record for the highest man-made flight before Gagarin's spaceflight?

Joe Walker flew X-15 #2 to 169,600 ft (51.7 km) on 1961-03-30, thirteen days before Vostok-1.
Source: X-15 flight log


A320 procedures for one thrust reverser inoperative; why is the old procedure more efficient?

Does the position of the controls for the second motor really influence the behaviour of the first one?

No, it influences the activation of various other systems like the autothrust, the airbrakes, as well as the thrust reversers.

  how it is more efficient?

Because in the new procedure the engine with non-functioning reverser starts to spool up before the system realizes the reverser did not deploy and cuts it again, so for a moment it produces forward thrust. The old procedure avoids this.


Do wingtip vortices really only form when airplane wheels are separated from the ground?

You are absolutely right. The vortices form whenever the wings produce lift. Even if the lift is not enough to let the aircraft fly.

Of course it is necessary to have a flow across the wing, and with very low speeds (like taxiing) the vortex is likely to be very small.

But,
it seems your textbook is trying to establish a save way to avoid the vortices of previous aircrafts. And since the strength of the vortex is related to the lift which is related to the air-speed and angle-of-attack this rule of thumb is quite practical. Especially since landing is a highly transient process which is very likely to result in a significant reduction of vortex strength.


Why are some engine nacelles thicker than others?

The nacelle contains a lot of equipment for controlling the engine. While this will certainly scale with the size of the engine, there is also some amount of minimum space needed for the components. The volume also increases faster than the surface area, so there is more room to spread things out. You will notice that the general trend in your pictures is relatively thinner nacelles as the engine diameter goes up:

E190 - CF34 - 57 in
B737 - CFM56 - 61 in
A330 - CF6 - 105 in

The difference between the CFM56 and CF34 isn't that great, but I think your image of the 737 isn't the best for comparison. If you look at an image more comparable to the CF34 picture you have, like this one, they appear much more similar.


What is the safe separation for landing a Cessna-172 behind a commercial airline jet?

It depends on the size of the preceding aircraft. ICAO PANS-ATM-Doc 4444 Air Traffic Management has some values.

5.8.2 · Arriving aircraft
5.8.2.1 Except as provided for in 5.8.l.l a) and b), the following separation minima shall be applied.
5.8.2.l.l The following minima shall be applied to aircraft landing behind a HEAVY or a MEDIUM aircraft:
a) MEDIUM aircraft behind HEAVY aircraft- 2 minutes;
b) LIGHT aircraft behind a HEAVY or MEDIUM aircraft- 3 minutes.

Note that in case of A380, it is more- 4 minutes.
In case of distances, the light aircraft are to be landed 5nm after a medium aircraft, 6nm after a heavy and 8nm after A380.
Note: The categorisation of aircraft is done as below:

4.9.1 Wake turbulence categories of aircraft
4.9.1.1 Wake turbulence separation minima shall be based on a grouping of aircraft types into three categories according to the maximum certificated take-off mass as follows:
a) HEAVY (H)- all aircraft types of 136 000 kg or more;
b) MEDIUM (M)- aircraft types less than 136 000 kg but more than 7 000 kg; and
c) LIGHT (L)- aircraft types of 7 000 kg or less.


To add some data to Matthew's answer:
Anti aircraft missiles come in basically 4 types (some others have been tried but aren't in common use).

Active radar homing
Passive radar homing
Infrared homing
Laser guided

Active radar homing has a radar in the missile sending out signals. Those signals can be detected and classified by the target aircraft.
Passive radar homing has a receiver in the missile reacting to specific signals bounced off of the target by the launching system. These too can be detected and classified by the target aircraft.
Infrared missiles are completely passive and can't be detected this way.
Laser guided missiles are like passive radar homing missiles, except they react to reflections of a laser beam rather than a radar signal. These too can of course be detected and classified with appropriate sensors.

There have been some attempts at detecting missiles by their own infrared signature, typically their engine exhaust. But this is problematic because most of that is of course blocked from the missile's target by the missile body, and also many missiles will spend a lot of their flight towards the target in an unpowered glide state, thus not having a hot engine exhaust.

Other systems generally can't be detected by the target either. Think optical guidance using a radio link with the missile (while you might be able to detect the link, you can't readily know what it's doing or that you're the target if you do recognise it as a missile guidance link).

Optical guidance using control wires is not generally used with anti-aircraft missiles, but sometimes anti-tank missiles using these systems are used against slow flying aircraft. These are utterly impossible to detect.


What does it take to enter the Red Bull Air Race?

According to their about page

  New pilots who wish to participate in the World Championship must first fulfil the minimum criteria set by the Red Bull Air Race Committee, which include top achievements in international flying competitions organised by the FAI. They must also be active aerobatic air display pilots. Eligible pilots that prove their skills at the Red Bull Air Race Qualification Camp can achieve the Red Bull Air Race Restricted Superlicence. Once they have the Restricted Superlicence, they then qualify to take part in the Red Bull Air Race World Championship in the Challenger Cup.

So I would suggest if this is something that interests you, you begin with some instruction in aerobatic flying - a discipline which in itself is quite tough. To find the next qualification camp, I would suggest contacting red bull air race directly. It seems they run annual qualifications, most recently held in Texas, USA.

The amount of time it would take is impossible to measure, or even speculate.


Why is the rear seat ejected before the front one?

If the front seat ejected first, the drag would probably bring him too close in the trajectory of the rear seat, thus making a collision of both probable.

Since the rear seat is ejected first, it experiences drag earlier than the front seat and will thus not have an increased probability of hitting it.


How did the B707 and DC-8 fight stress at the windows?

No, the Boeing 707 and the DC-8 used radiused corners on all their windows to avoid the problems of stress concentration factors, plus additional pad ups around the openings in the skins for the Windows themselves.

(Source)


In the Cl vs Cd graph, Why the drag coefficient decreases initially with the small increment in lift coefficient?

Think about it this way.  Assume a cambered airfoil, not a symmetrical airfoil.  Assume the wing has zero twist and zero incidence.  To place the wing at the zero-lift angle-of-attack (zero CL), the fuselage and wing will have to fly at a somewhat nose-down pitch attitude relative to the airflow.  This does not yield the lowest possible drag coefficient, regardless of whether we are looking at the wing, the fuselage, or the whole aircraft.

Bear in mind that in this part of the flight envelope (near the zero-lift angle-of-attack), drag is dominated by profile drag, not induced drag.

Related:  Is drag coefficient lowest at zero angle of attack?

Now imagine using the same data to generate a graph of CD versus airspeed, assuming Lift=Weight.  What would that look like?  Also what would a graph of Drag versus airspeed look like?


Why did the crashed TAM Airlines Flight 3054 veer off the runway only near the end?

Right Engine thrust

The engine takes about 12 seconds to spool up from idle to full thrust.

Auto-throttle had held both engines near idle during the approach to touchdown. The throttle levers should both be retarded from "climb" to "idle" position prior to touchdown. But only in the last two seconds before touchdown, after the aircraft emitted a warning, was the left throttle retarded - but the right throttle lever was not moved from the "climb" position.

When the left throttle lever was retarded, this disengaged auto-throttle, so  the right engine started to spool up to "climb" power setting as commanded on the right throttle lever.

So immediately after landing the right engine wasn't producing any thrust.

The thrust only developed gradually during the following 12 seconds as the aircraft traveled down the runway.

Rudder authority

At landing the aircraft might be travelling at 140 knots. At this speed, deflection of the rudder by the pilot can still have significant effect and can counteract asymmetric engine thrust.

As the aircraft traveled down the runway, airspeed would have reduced and rudder authority gradually diminish at the same time as the right engine was spooling up to CL (climb) power.

The aircraft ran off the runway at about 90 knots.

Nosewheel steering

When using the rudder pedals for nose wheel steering, the steering angle starts to reduce at 40 knots and progressively reduces to zero degrees at 130 knots.

According to the accident report,

  When the accident happened, the volume of precipitation was 0.6 mm.

So a combination of speed and a wet runway may have reduced the effectiveness of nosewheel steering.

I don't know, but I suspect that nosewheel steering may not be able to fully compensate for the yawing effect of left engine at idle and right engine at climb power.

Differential braking

  The FDR also recorded the use of the rudder and the differential braking by the pedals as the aircraft veered to the left (probably in an attempt to maintain the plane on the runway and stop it).

It seems that the crew really needed to shutdown or idle the right engine to complete a landing within the boundary of the runway.


Why we had two empty rows on busy Ryanair flight Boeing 737-800 and no one was allowed to seat there?

Were these emergency exit rows?

Seat pitch on low cost airlines is too small to allow an emergency evacuation within the required 90 seconds with regular seat pitch in the exit rows. Therefore, the seat pitch is larger there, which makes a world of a difference for tall people. Low cost airlines have decided to monetize those few more inches of leg room and charge extra for sitting there.

If no passenger on that flight was willing to pay the extra fee, those airlines which pride themselves on treating their passengers with the utmost contempt keep these emergency exit row seats free even if the plane is fully booked on all other seats.


What is the farthest commercial flight on a B737-800 currently?

I believe this is GOL's Orlando->Brasilia flight at 3,778 miles. Prior to that it was Newburgh to Bergen at 3,456 miles.

Lufthansa has a 737-700 but it is a Boeing Business jet equipped with extra fuel tanks and only 86 seats which makes a Frankfurt to Pune 4,158 mile flight.

Source


Can I fly with an airband receiver in the United States?

This is probably more a travel question than an aviation one, but I did some Googling of various aviation and travel sites and the consensus seems to be this:

You can carry the scanner with you, but if you're unlucky and encounter the wrong TSA agent on the wrong day then you may be asked a lot of questions at security (the TSA's "Can I Bring..." tool seems to consider scanners to be generic electronic items)
Using the scanner while sitting in the airport is fine, but if you attract attention to yourself then you may be questioned by the police or airport security
You may not use a two-way radio on board the aircraft, because they're specifically required to be off at all times (this is in every airline's safety instructions that I've seen); that shouldn't apply to a radio that only receives but the cabin crew might ask you to turn it off anyway if they're not sure about it
Even if you did operate the scanner in the air, the reception is terrible and you'll probably hear only the aircraft's crew, not ATC

Note that this information is for the USA only, many other countries are very strict about possession and use of scanners or two-way radios and in the UK (for example) just listening to ATC is actually illegal.


Why was brown chosen to represent the ground side of an attitude indicator?

The answer to the specific question of "why PFD's (glass cockpits) use this standard" is because their old style gauge cockpits used it before them. The glass cockpits of today are made to be similar to the older gauges so as to avoid confusion in their operation when moving from one type of aircraft to the other. This has been shown to be an issue in the past in the difference between American and Russian attitude indicators as such instrument operation strives to be at least somewhat uniform.

Now as for the more general question "why are attitude indicators Blue/Brown?" there are a few reasons. First off some types of color blindness cause issues with the blue/green mix making it a combination to avoid (some info on color blind flying). Second, and perhaps as important is that blue and brown sit basically on opposite sides of the color wheel making them very contrasty while blue and green sit right next to each other on the wheel. This ensures accurate viewing in most lighting situations.

There are also other attitude indicators like those commonly used in military aircraft which have had different colors

(source)

The oldest examples are completely void of any color (you can see why they introduced color)

(source)

For what its worth some modern flight displays now include terrain data and are capable of showing many other colors to outline it as can be seen here on this Garmin unit

(source)


Why does the BAe 146 have higher maintenance costs than other comparable jet aircraft?

higher maintenance cost and higher cost of operations in compare to other jets due to its complexity.

That seems ironic considering what Wikipedia says

According to the BAe 146's chief designer, Bob Grigg, from the very start of the design process, making the aircraft as easy to maintain as possible and keeping operator's running costs as low as possible were considerably high priorities.
Velupillai 1981, pp. 1245-1246, 1253.

Why is it more complex than other jets?

Because it has four engines? I believe short-haul airliners of similar capacity mostly have only two.

Why are the maintenance and operating cost higher?

Wikipedia says of the original Lycoming engines used:

The ALF 502 has experienced multiple issues. Its internal electronics could overheat, triggering an automatic shutdown of an engine with no option of in-flight restart, and certain rare atmospheric conditions could cause a loss of engine thrust due to internal icing.[29] Additionally, the BAe 146 experienced aerotoxic syndrome due to leakage of tricresyl phosphate (TCP) into its bleed air; this has been blamed on problems with leaking engine seals. Exposure to these toxic fumes is a dangerous health risk

Note: the above is speculation, you'd have to ask an airline maintenance manager.
There are interesting maintenance anecdotes / whinges at pprune

High price of spare parts.
Accessibility of some components.
N1 harness that goes through engine fan strut.
Quick release fastners needed on engine core covers.
FADEC harness (RJ) can't be changed without dropping the donk.
Lower engine power cables that freeze full of moisture.
Corrosion issuse with the gear bay longeron strut.
The nose landing gear steering lube leaks out and the internals corrode
Air con pacs are unreliable.
Honeywell apu's are unreliable, Garrets better.
Fuel tanks need proper draining off every day to get rid of moisture.
Tri-wing fasteners often fail on removal.


Is the actual VMC to IMC transition a challenge (for IFR rated pilot/craft etc) if, say, sudden or unexpected?

If you are an IFR pilot hand flying in VMC and suddenly your horizon reference disappears, or becomes untrustworthy (flying over sloping terrain in low visibility, or flying between cloud layers that are sloping), you do have to make a conscious mental transition from external scanning to internal scanning and it will increase the stress level slightly when you're new, but this declines as you get experienced doing it and it eventually becomes a non-event.

This is mainly because if you are flying IFR a lot, especially commercially, you will be doing this all the time on departures in instrument conditions, where you take-off visually, looking outside, and immediately enter cloud, often even before it's time to engage the autopilot (you wouldn't really want to to do a lot of IFR flying without one).  So effectively you have to make that VMC to IMC transition on every departure in IMC weather that you hand fly while entering cloud and you get used to the look-out-to-look-in transition pretty fast.

So I would say the answer is yes to a new pilot, but quickly becomes no, once experienced a bit.  That being said, "grey area" conditions, like I mentioned at the start, where you need to go on the gauges even though there is still a view outside, would be more of a challenge compared to just charging into cloud where the view goes from green to grey instantly and the distraction of a misleading outside view isn't there. That requires a bit more concentration and self discipline to ignore the view outside, and therefore a bit more experience to drop the stress level of the transition.  But still, after doing it a number of times, it should be no big deal.


Can a software "hard freeze" or serious hardware problem completely disable the whole cockpit?

If the power suddenly disappears to any aircraft (ie, a total electrical failure including the batteries), then all the aircraft systems will be failed regardless of whether or not they were glass.  This is highly unlikely because there are several power generation backups that would have to fail, including the batteries themselves, before this ever became a reality.  Unfortunately though, if the aircraft only has electrically controlled, hydraulically actuated control surfaces (fly-by-wire), vice actual mechanical linkages (or backup controls), then a total electrical failure would be 100% fatal if power cannot be restored.  The control surfaces would not be movable.

However, more to the question regarding software bugs, all primary flight instruments are backed up to prevent such disasters from happening.  I have personally lost all the digital displays in my cockpit and flown a no-gyro, surveillance approach in bad weather using nothing but a peanut gyro.  Its possible, but definitely not a good time.

Anything is possible.  However, even though the odds of a total electrical failure, or complete loss of instrumentation (including backups) is nominally greater than 0%, the statistical probably can still probably be rounded to 0.


Those with gear reduction are called geared turbofans (GTFs). In general, you can check the Wikipedia article on any engine, see its classification and specifications, and also check the linked citations.

The GE90 and Trent 1000 are not geared turbofans. Wikipedia lists only 5 geared turbofans, with the biggest (a recent engine; first run 2008; entry into service 2016) powering the A320neo family (narrow-body jetliner) and other regional jets.

Because of the immense torque of large turbofans (thrust >200 kN), it is not yet feasible. It took 20 years to develop the ~100 kN PW1000G.$^1$ It took that long to ensure the new components are maintenance free (apart from oil changes). So for the time being GTFs are outliers, and when a turbofan is one, it would be stated.

Prior to the PW1000G, there is the ALF 502/LF 507 from the 80s that still powers the 146/RJ. The ~30 kN GTF was designed/chosen for its relative quietness for operating from noise-sensitive airports.

Note: the fan blades are not welded, rather connected/attached. You can watch a fan removal here (noisy video).

$^1$ http://large.stanford.edu/courses/2014/ph240/suresh1/docs/pwspecs.pdf


How do I calculate propeller effects on pitching moment?

The propeller causes pitching (and yawing) moments. There are two main reasons for that:

1) flow change around the fuselage (and central wing and tail)
2) thrust change.

Thrust change is simpler to grasp and estimate. The thrust vector will cause a moment, because (90% of the time) it's a bit tilted and does not pass through the CG of the aircraft.

Several model aircraft have intentionally tilted propeller / motors. The perfect amount of tilt is found through flight tests, because its simpler and more accurate to try and feel the effect.

A pusher configuration has quite similar concerns related to thrust vector, however the flow change effect is much less than a tractor configuration. This is because for the pusher configuration the accelerated flow does not effect the air vehicle any more.

Calculation of these effects range from hand calculations (spreadsheets) to CFD and finally to flight tests (where you'd do controlled tests to derive the model parameters).

For RC aircraft I'd suggest following the rule of thumbs that have been established in the RC communities.

Finally, tractor / pusher configuration selection should be based on several other factors and thrust moment is probably not the most important one.


Are Aircraft yokes self centering in non-auto pilot mode?

With respect to "centering", a yoke only "centers" itself in the equilibrium point where forces on both ailerons and on both top and bottom of the elevator/stabilator are equal. That said, I wouldn't want to let the yoke "center and fly itself" as the forces on the control surfaces can be equal even when the aircraft is not straight and level. If not enough power is applied the plane will pitch down and "center" as you say, and if too much power is applied the plane will pitch up and then "center". As for roll, I find that in light aircraft (Cirrus excluded as the side stick has a spring mechanism) you don't usually want to leave the yoke out of hand as slight wind and light wind shear will cause the airplane to roll somewhat. So - short answer is - yes, it will "center" eventually but you might not like the attitude the plane is in when it's done, much of this depending on power setting and gusts/shear aloft/turbulence. As for autopilot, a roll and pitch (2-axis) autopilot actually continually applies force to the controls to keep the airplane level or turning as commanded, and at a constant altitude or climb/descent/airspeed as commanded, so I wouldn't say the controls really "center" when on autopilot either. Cheers!

As a bit more of an explanation, a "nice" airplane (one with positive aerodynamic stability) with the appropriate power setting should re-enter and maintain straight and level flight if the controls are disturbed and the yoke is released (but I've always had to input a little roll to keep the wings level). Check out the following picture from the FAA Pilot's Handbook of Aeronautical Knowledge Page 4-14:

Notice that the orange line eventually gets more and more flat. You can expect that in a Cessna 172 or something of the like... not in a more aggressive plan like aerobatic planes and fighter jets - you'll see something a little more like the green or red line. You can read more in Chapter 4 of the FAA PHAK (link here).


How does a student pilot learn the process of pre-flighting a Robinson R22?

I have never flown the R-22 but I am rated in RH and ASEL. I can answer specifically about the Schweizer (Sikorski) 300C/ CB/ CBi helicopter.

1) How does one learn the preflight? From your instructor. During each lesson the first part of touching the aircraft should be the preflight. Legally speaking, that is after touching the log books/ registration/ weight and balance/ etc. to make sure that it is potentially airworthy in the first place. First you watch them do the inspection, then you do it under supervision, then they watch you from a distance, then the instructor finishes up whatever they are working on last while you preflight it solo (with the best instructors doing the preflight themselves before you even start).

2) How long does it take? For the Schweizer it took me probably the first 10-12 lessons since I was initially not able to fly frequently enough to remember most of what I learned the last lesson and I was working 80+ hours per week at the time. Going 1-2 months between lessons is very bad for retaining new information. Had I worked less and flown more it probably would have taken half of that for me to get comfortable doing the preflight myself.

The items on the checklist are really not that hard when you understand the function of the parts you are checking. When you check control rod integrity you know what they do. You follow them from the cyclic and collective through the cabin, up the mast, through the mixer arms, and to the swash plate. You check the swash plate. You follow up the mast to the control rods attaching from the swash plate to the rotor blades themselves. Other than the climbing around the aircraft it probably took me longer to type that than to actually do it for a preflight.


For training with a grace month, is it legal to fly in the month after training expires before going to school?

Yes, the FAA issued a Letter of Interpretation from their Chief Counsel in May 2015 which covers Section 61.58 proficiency checks and specifically addresses this issue.

It says that a pilot may continue to act as PIC during the grace month under Parts 91, 121, and 135.  It says (in part, and emphasis added by me):

  Section 61.58(i) states that, if a pilot completes the proficiency
  check in the calendar month before or the calendar month after the
  month it is due, "the pilot is considered to have taken it in the
  month in which it was due for the purpose of computing when the next
  pilot-incommand proficiency check is due."

  You have asked whether the language in paragraph (i) creates a "grace
  month" during which a pilot whose currency has lapsed under paragraph
  (a) may continue to act as pilot in command. The FAA has previously
  stated in a legal interpretation that § 61.58 includes a "grace month"
  for purposes of complying with the 12- and 24-month proficiency check
  requirements. We did not explicitly state, however, that a pilot may
  continue to act as PIC during this grace month. Legal Interpretation
  to Sean Conlin (Feb. 24, 2000). We have indicated, however, that
  similar provisions in parts 121 and 135 create a "grace month" during
  which a pilot may to continue to act as PIC during the month after the
  pilot's currency has lapsed? Legal Interpretation to Gregory S. Winton
  (2006), Legal Interpretation to J. Dennis Vanatta (June 25, 1996).

  The FAA intended the grace month to limit disruptions in operations
  conducted under parts 121 and 135 by accommodating pilots who are
  unable to complete recurrent training requirements in the month they
  are due. At the same time, the FAA did not want operators to use the
  grace month as a means of regularly extending a 12-month proficiency
  check to a 13-month proficiency check. For that reason, a proficiency
  check under part 121 or part 135 that is completed in the grace month
  is considered to be completed in the month it is due. The FAA believes
  that the same approach is appropriate for§ 61.58 proficiency checks.
  As such, a pilot may continue to act as pilot in command during the
  month after a§ 61.58 proficiency check is due. However, when a pilot
  completes a §61.58 proficiency check during this grace month, it is
  considered to have been completed during the month it was due for the
  purpose of calculating the next proficiency check.


When an airship climbs the hydrogen in the ship's cells expand. Does this mean that when the airship descends the empty cells fill with air?

First of all, Zeppelins carried tons of water ballast in order to compensate for hydrogen seeping from the gas cells or being vented when the ship had climbed too high. Before launch, the crew calculated the ballast need based on the planned length of the flight and weather conditions. Also, the ship lost mass continuously by burning off fuel. Below you see the calculation sheet of LZ 40 from May 1915. The ship took 7.5 tons of water, distributed over several tanks along its length.

The top row of the sheet lists fuel (Benzin, 9320 kg in total), then oil (520 kg), then a side view of the ship with its 16 gas cells and below that the water ballast. The crew weighed 334 kg.
On the ground the gas bags were never full. In the later WW I Zeppelin models, only one third of the internal volume was taken up by the gas bags and their hydrogen while the rest of the hull was filled with air. As the airship climbed, the hydrogen in its cells expanded and pushed the air out. On the way down the reverse happened. The gas bags were flexible and sufficiently airtight so no air would enter them.
The photo below is from airships.net and shows the LZ-129 Hindenburg under construction. The gas cell is partially filled and is attached to the circular frames over two thirds of their circumference to distribute the lift of a partially filled cell as evenly as possible. Wire bracing distributed the load over the full frame. In the center of the hull you can see a walkway for inspection; the gas cell had a central tunnel to allow lengthwise movement over the full length of the ship. The vertical funnels for venting leaked hydrogen are not yet installed.

This is only possible with rigid ships; blimps use ballonets for the same purpose but have to pressurize them a bit in order to keep their envelope taut.


Has the construction team of the Northrop Grumann B-2 Spirit made use of the features of the German Horten Ho 229?

If the objective is very similar, good engineers will independently arrive at a very similar solution.
Yes, the Northrop engineers knew of the Go-229 / Ho-IX. But Jack Northrop has also played with flying wings before – witness the YB-35 and YB-49. Unfortunately, those designs "did not fly" with the conservative bureaucracy of the Air Force. While the Ho-IX was a very advanced concept, there was no "secret" in its design, so how a low RCS airplane should look like was quite obvious to the Northrop engineers.
That the B-2 looks more "edgy" is caused by more insights into stealth technology. While the Horten IX tried to minimize frontal area, used wings of wooden construction (which are transparent to radar energy) and Reimar Horten had planned to use radar absorbing charcoal, the B-2 uses edge alignment in order to reflect radar energy at specific angles, besides using radar absorbent material. When Northrop was designing the plane, it had a rhombic inner section with rectangular wings, much like what is now shown of the new B-21 design, but the small chord at the wing root created a structural weakness when the Air Force added a low level flying requirement. That only was overcome after Boeing got involved. Boeing engineers changed the planform to the current shape by adding more chord at the inner wing which resulted in the typical "W"-shaped trailing edge of the B-2.

B-2 design evolution and its Lokheed competitor (picture source)
After the B-2 production run had ended and after Grumman had merged with Northrop, a full-scale RCS model of the Horten jet was fabricated by Grumman engineers with modern techniques to simulate the aircraft as it would appear to electromagnetic energy. It was tested at a RCS test facility, using similar frequencies as those used in WW II. While the design did show a markedly lower RCS than comparable airplanes of the time, this can be fully attributed to its shape and the use of wood.

Horten IX replica on a sting at the RCS test range (picture source)
Reimar Horten was a bit dogmatic about his designs and insisted that they only use a wing and not even a vertical tail, even though this would had benefited its flight stability. As it turns out, a straight vertical tail produces in combination with a wing or the horizontal tail a nearly perfect corner reflector. While this dogmatism helped to reduce the airplane's RCS, it resulted in marginal lateral stability.


What happens if a crew complies but does not read back ATC instructions?

No, ATC would not file a complaint for a single missed read back. In order to file a complaint they'd need to have very good reason to believe that the pilots were willingly breaking communication regulations, and there are so many other valid reasons for why this scenario could happen:

The pilots may have responded but it may not have been received. If two stations talk at the same time the stronger one wins, so they may have read it back but it was lost
The pilots may be dealing with a problem, or have a high workload. Communication is the lowest priority, flying the airplane safely is first, then navigation
The pilots may have a technical problem with the radio
The frequency could be too busy to get a read back in, sometimes the frequency can be so dense with communications you can't get a word in edgewise, so the pilots may comply and eventually just give up

These are just a few reasons from my own personal experience when I haven't read back an instruction or my read back wasn't received. If ATC is worried about it they can always call me back.

EDIT: The readback is a requirement for some instructions and I am in no way saying it's okay not to. My answer is for the specific scenario given, I think that the FAA would and should bust people who fail to readback in certain circumstances.


Any ideas on what caused my engine failure?

The most likely cause of your engine cutout is what's known as a rich cut caused by coarse application of full throttle. Most carburetors have an accelerator pump which jets extra fuel when the throttle is pushed in quickly, this is to make sure the engine has enough fuel and prevent what's known as a lean cut. However, at high density altitude your mixture needs to be leaner than at sea level, so it can in some circumstances do the opposite and give your engine too much fuel to burn.
It's also possible your mixture was too lean, so advancing the throttle caused it to die on you. There's no way to know for certain.
In the future advance the throttle smoothly, it doesn't have to be super slow, just don't jam it in. 2-3 seconds from idle to full is about right (same goes the other way too). If it starts going gluk gluk gluk on you enrich the mixture a couple of turns and see if that resolves it. Don't forget on a touch and go you have the option to abort, don't be afraid to use it if there's issues. Remember that takeoffs are optional, landings are mandatory.
And remember that carb heat! Icing can happen in any conditions.


How often do GA pilots use the Autopilot approach feature while landing?

It's a perfectly acceptable practice, provided you disengage the autopilot upon reaching minimums and hand fly it the rest of the way.  Some manufacturers, like Cirrus, recommend flying a coupled autopilot approach.

I won't sit on the fence about this.  Learning how to fly coupled autopilot approaches are fine, but I insist all my students learn how to hand fly approaches, both as part of their initial instrument training and for all instrument proficiency checks I administer.  If I were an examiner I would insist on seeing instrument applicants demonstrate hand flown approaches on their checkrides as well.

Autopilots are great but their use can begin to atrophy their flying skills and it can come back to bite them, particularly in an emergency.

As to the exact numbers of GA pilots who fly coupled autopilot approaches, that's probably going to depend on the pilot and the equipment in his/her aircraft.  Pilots with autopilots installed are probably going to be much more likely to use them and be more comfortable flying approaches this way.


How does the downwash, that has already passed behind the trailing edge of the airfoil, influence the airflow upstream, causing the entire relative airflow to bend upward as in the picture.

The downwash is behind the trailing edge, but the acceleration of the air downwards happens above and below the wing. The highest acceleration is around the quarter-chord where the centre of pressure is.

In subsonic flow, the pressure changes do propagate upstream due to how the various flow equations work. The sharp trailing edge is indeed an important feature of efficient wings that affects how the flow behaves around the wing.

  Or is it just an imaginary concept to explain the induced drag?

It isn't. But there are many ways to explain it. I prefer using the conservation of momentum and energy (that I explained here).

Note that for supersonic wing, the mechanism changes to wave drag. The conservation argument still holds and explains why there can't be lift without drag, but now that the pressure changes do not propagate upstream the pressure field looks differently.


In normal cabin seats, the reason not to recline them for takeoff & landing is so the reclined seat won't impede egress for passengers in the row behind yours.  If the seats in question on VA wouldn't do that (ample space between rows, perhaps), then the usual driver for requiring seats to be fully upright is gone.

Presumably whatever "certification" they referred to considered the ability to get out of one's own seat in case of an evacuation.


Is there a public database for annual flights by aircraft type?

Short answer is "no". There is no such thing as a "registered" flight.

In cases where pilots have filed flight plans, you could aggregate that data. It would be a BIG programming project. There are commercial services that analyze flight plan data. They might be willing to help you for a price that would be in the 10's of thousands of dollars.

Flight plan data would only be good for US information. Other countries would require other data collection.

Small planes usually don't file flight plans, but you may not care about this.

Aircraft manufacturers estimate how much their planes fly around. Whether they would be willing to share this data with you, I don't know.


Is a first class medical to be an airline pilot eventually possible?

The section

Decision Considerations - Aerospace Medical Dispositions
Item 47. Psychiatric Conditions

From the FAA's website has a lot of the information for you. This page on SSRI's specifically has even more info to read up on. If you burrow down you will find a lot of worksheets and AME advisory papers most of which ultimately state

  Requires FAA Decision/Submit to FAA for approval

This basically means that the AME can not make the decision and its up to the FAA directly. That being said there is hope and they do make a path pretty clear for you to take.

In any case if you are tapering off a drug it may be best to wait until you are off it completely to go see an AME. The FAA seems to be much more cut and dry on current usage and far more "case by case" on historical usage based on the way the regs are written.

You may also want to take a look at the regulations here


What is this long Bar/Rod on the Boeing MH-47G?

This is the In flight refueling probe, which can be used for refueling while the helicopter is airborne:

(image source: pinterest.com)

It is almost 9 meters long to make sure the rotors do not hit the refueling drogue. You can see it in action in the following picture:

(image source: chinook-helicopter.com)


Is it possible to build an ultralight helicopter with electric motors as its main engines?

From a quick Google search, you can find that Sikorsky Firefly and Tier One R44 are two examples of eHelos, conventional helicopters converted to electric propulsion. They both fly around 20-30 minutes (though the Firefly never flew).
As for building an electric helicopter, I believe off-the-shelf components (such as Tesla motors and batteries, available from parts breakers) have enough performance for an eHelo. The actual configuration of the aircraft (single main, coaxial, multicopter etc.) depends on the manufacturer's expertise on rotor blade hubs and/or distributed electric propulsion. So unless you work for Kamov, a coaxial rotor hub will be prohibitively complex (thus expensive) for a prototype ultralight helicopter.


Why does the Grumman Bat feature inverted winglets?

Without knowing what was going on in the minds of the designers it's difficult to tell exactly, however there are a few reasons as to why the vertical stabilizers are featured both above and below the wing.

In the sUAS market there are a huge amount of products which offer very similar capabilities. It is quite possible that the stabilizer design of above and below rather than in a single direction is to differentiate the product in a crowded market. This is similar to business jet design wingtip design - while it is known drag may be reduced the devices offer aesthetic appeal and different designs stand out to buyers.

The design also allows for the same surface area with a smaller packing footprint. Due to the bulbous shape of the fuselage the potential package size of the bat is smaller with the stabilizers as designed rather than simply above or below.

The stabilizer design is symmetric around the horizontal plane, meaning that in a side gust condition the UAS will feature less tendencety to roll and will instead simply be 'shifted'.

Again in a side gust condition the balancing of forces above and below the attachment point cancels out the moments and therefore may allow for a less strong joint (weight savings).


Why nitrogen generation system is only present in centre tank only?

The inerting system was added to the A320 as a result of a new FAA regulation in 2008:

On 21 July 2008, FAA required
operators and manufacturers
to incorporate a Flammability
Reduction Means (FRM) or Ignition Mitigation Means (IMM)
on fuel tanks having a flammability exposure exceeding certain
thresholds [...]

(Airbus FAST Magazine 44)
Airbus found that only the centre tank was affected by these thresholds required by the FAA:

AIRBUS COMPLIANCE TO THE RULES
Airbus demonstrated that ‘only
the centre tank’ of some of its
existing aircraft has fleet average
flammability exposure exceeding
7% and is affected by the
requirements of the FAR Part 26.
There is no necessity to do any
modification on other tanks.
It concerns the following aircraft:

A320 Family,
A330-200, A340-200,
A340-300, A340-500, A340-600,
A300-600.

(Airbus FAST Magazine 44)
What exactly does fleet average flammability exposure mean? The FAA defines it as follows:

the percentage of the flammability exposure evaluation time
(FEET) each fuel tank ullage is flammable for a fleet of an airplane type operating over
the range of flight lengths in a world-wide range of environmental conditions and fuel
properties as defined in this appendix[, which] means the percent of time each fuel tank ullage is flammable for a
fleet of an airplane type operating over the range of flight lengths.

(FAA Advisory Circular 25.981-2A)
Since the centre tank is usually used first, it will spend more time empty (or almost empty). Fuel vapour is highly combustible (much more than liquid fuel), so the risk is significantly higher for the centre tank.

By the way, the system is not really a nitrogen generation system. It only enriches the nitrogen content of some HEPA filtered bleed air to reduce the oxygen content:

Air Separation Module (ASM) description
It is the core of the Inert Gas Generation
System. The objective is to reduce
the centre wing tank ullage O2
concentration to below 12%
during most conditions. Each ASM
is a semi-permeable hollow fibre
membrane bundle contained in a pressure
containment canister. This canister
is a cylinder with three ports. There is
only one ASM on the A320 Family aircraft,
two on the A330-200 and A340-200/300,
and three on the A340-500/600.

(Airbus FAST Magazine 44)


What does the last 'B' in 'GEnx-2B67B' stand for?

Based on the below (in chronological order), it very much looks like the (or a) difference between GEnx-2B67 and GEnx-2B67B is a booster anti-ice (BAI) air duct. And this suggests that the 'B' stands for 'BAI' or 'booster anti-ice'.

  We propose to adopt a new airworthiness directive (AD) for all General Electric Company (GE) model GEnx-2B67 and GEnx-2B67B turbofan engines with booster anti-ice (BAI) air duct, part number (P/N) 2469M32G01, and support bracket, P/N 2469M46G01, installed.

https://www.federalregister.gov/documents/2013/04/11/2013-08447/airworthiness-directives-general-electric-company-turbofan-engines

  The Boeing Company and GE asked that the GEnx-2B67 turbofan engine be removed from the Applicability section of this AD. The commenters noted that this engine does not have BAI hardware, therefore, inspection and modification of the BAI does not apply.

https://www.federalregister.gov/documents/2013/08/19/2013-20097/airworthiness-directives-general-electric-company-turbofan-engines

NB: Another hypothesis, that the 'B' is some kind of alphabetic numbering, seems refuted by the lack of an 'A' or 'C' model. Google will find very, very few (1 or 2) hits for 'D' and 'E', which could be typos.


Why this P-51 limitations placard for diving?

That's correct.  The limitations are to stay below the critical Mach Number, and altitude is used because it's easier for the pilot to monitor and reference to than temperature.  The numbers are based on the standard atmosphere's temperature profile and I imagine there is some fudge factor or safety margin to allow for normal deviations from ISA.
The chart below is from the P-38 training manual which shows more or less the same thing as your placard in graphic form.  The lines become vertical near the top because at about 36000 feet you are in the stratosphere in the mid latitudes and temperature stops decreasing (The Mustang's placard is a bit odd because you would expect the limit speed at 35000 and 40000 ft to be the nearly the same, but there is a 30 mph difference.  Not sure why that is).
The P-38 suffered from a lower critical Mach Number than the P-51 (.68 vs .7) limiting its dive speed at 30000 ft to 290 indicated vs 325 for the Mustang (a major combat limitation until dive recovery brakes were developed - until then, P-38s couldn't chase aircraft in power dives because of the pitch control problems when going transonic).


Why isn't the airspeed indicator the primary instrument for power during a constant speed climb?

Airspeed indicator is a primary instrument for pitch in that row, so it can't be also primary for power.

The point of constant speed climb is that you select power and maintain speed with pitch, getting whatever climb rate that power can support. Most often the point is selecting "climb" or "maximum continuous" power and climbing as fast as possible without overstressing the engine.

The only difference with variable pitch prop is that it decouples rpm from engine power, so you can't use rpm and are left with manifold pressure only (for piston; I am not sure what the correct reference is for turbine).

Note that two lines lower there is a constant rate climb and there airspeed is primary reference for power, because there you adjust pitch to maintain desired vertical speed and power to maintain airspeed. But since you shouldn't use more power than the recommended climb setting anyway, the constant speed climb gives you better performance.


What portion of an Instrument Proficiency Check must be in the airplane?

This is explained in the Instrument Rating ACS (page A-18):

  Instrument Proficiency Check

  If a person fails to meet the experience requirements of section 61.57(c), a pilot may only
  establish instrument currency through an instrument proficiency check
  as described in section 61.57(d). An FSTD may be used as part of an
  approved curriculum to accomplish all or portions of this check. If
  specified in its LOA, an AATD may be used to complete most of the
  required Tasks. However, the circling approach, the landing Task, and
  the multiengine airplane Tasks must be accomplished in an aircraft or
  FFS (Level B, C, or D).A BATD cannot be used for an instrument
  proficiency check. Please see the Task Table in Appendix 5 for
  additional information. (Appendix 5, Instrument Proficiency Check
  Table).

To summarize:

If the simulator is an approved FFS, you can do the whole IPC in it
If the simulator is an approved AATD, you can do everything except circling, landing and multi-engine tasks
Otherwise, you need to use an aircraft


When does the FMS in the 737NG switch to approach mode?

If the 737 is like most other FMS installations you will find the approach will activate at the capture fix.  It is typically the waypoint just before the FAF.  If you were flying into KMEM RNAV RWY 36C the capture fix would be NESBT and the FAF would be GINIE.
In the FMS that I use, the capture fix is typically loaded twice into the flightplan.  Once from the enroute structure and once again for the approach after the approach name.

NESBT
** RNAV 36C **
NESBT
GINIE


What are these engineers doing sitting on a large format drawing of B-47s aircraft?

As commented by Anilv, they are examining a factory production layout/plan. They most likely are attempting to resolve a production or supply problem, though as Anilv suggests, they may also be planning the factory layout.

Listed below is an example of the B-17 Flying Fortress Factory Production Layout used by Boeing in WWII. Note the arrows which show the production procession and parts/sub-assembly entry and exit.

Source - Boeing


Why are these windows on some airplanes red?

A red/orange color is typically used to denote flight test instrumentation. Indeed, these windows do contain such instrumentation. Below you can see a similar window on a 747-8I flight test aircraft (note the 7th window from the nose):

And the corresponding inside view:


What is the difference between a Sub-Charter Flight and a Codeshare Flight?

Sub charter is not used nowadays as a word expression. It's now called wet lease or ACMI. An ACMI specialist airline does not fly its own regular schedule, but usually flies for other airlines on shorter/longer notices (couple of flights or whole schedule). When WOW air started in Iceland, its schedule was flown by a Lithuanian ACMI operator. HiFly flies for Condor its service from Munich this winter, because Condor's 767s are undergoing heavy maintenance. Thomas Cook of UK is a permanent wet leaser to Condor (they are in the same holding). They provide aircraft and pilot crew, but Condor does fuel, maintenance and cabin crew. In the HiFly example above, HiFly provides full ACMI (aircraft crew maintenance insurance) for Condor.


How can you explicate the efficiency of a turbofan engine with Carnot's theorem?

The Carnot efficiency is the maximum attainable efficiency in terms of extracting work from a temperature differential, not the actual efficiency in a turbine engine. For the actual efficiency, you should look into the Brayton cycle, which approximates a turbine engine much better.

With that out of the way, let's look at the Carnot cycle. This cycle assumes a heat source that can provide arbitrary amounts of energy at a certain temperature $T_h$, and a heat sink that can sink arbitrary amounts of heat at a temperature $T_c$. These are the isothermal parts of the cycle. To get the working fluid to either temperature, adiabatic compression is used.

These heat sources and sinks do not exist in reality, but by approximation, the atmosphere is an excellent heat sink, and burning fuel is an excellent heat source. The low temperature is thus taken as the atmospheric temperature which can be as low as -50°C (~220 K, remember that Carnot's efficiency is defined in terms of absolute temperature) and the high temperature is the temperature in the combustion chamber.

Sometimes you hear that $T_h$ is the hottest temperature in the cycle, and $T_c$ the coldest temperature. While this is often true in practice, this does not need to be the case for theoretical considerations. The only thing that matters for the Carnot efficiency is the temperature of the heat sinks/sources. You can't get more efficient than the Carnot cycle by hooking your engine up to a fridge. Indeed, the Carnot cycle is just a way to express the Second Law of Thermodynamics, which states that entropy in a closed system can never increase.


What documented practices are there for NOTAM creators and handlers to combat NOTAM spam?

It's a real problem. Probably the worst you could do is read a raw DUATS briefing. If your EFB includes briefing support, those will do a slightly better job formatting and organizing everything. If you're flying VFR most of the time like me, keywords like IAP, ODP & SID following an airport identifier are only relevant to IFR, and not information concerning that flight.

Needless to say, the burden is on the airman right now. Maybe if someone passed these abuse cases to a forward-thinking FSDO, they might have a chance of some relief.


How did shortening the 707 increase its range?

If the fuse was shortened that much (reducing both the weight of the airframe and its cargo-carrying capacity) and the maximum takeoff weight stayed the same, the most natural explanation is that the plane's allowable fuel load at takeoff or the tank's capacity was increased.


What is the FAA's official outlet for informing the public of permanent, systemic changes?

The FAA has multiple email groups you can subscribe to.

https://public.govdelivery.com/accounts/USAFAA/subscriber/new?topic_id=USAFAA

Click the link and you will be brought to a page where you can provide your email address.

You will then be brought to a page where you can select the email groups you want to subscribe to.


How would one perform a more thorough preflight of the engine on a single-engine airplane without easy access to engine compartment?

These issues don't pop up that often that you would need to include them on a preflight check. Those aircraft/engines are reliable enough that any issue can usually be determined by things like:

Excessive oil use
Oil Temperature / Pressure Changes
Rough running or improper behavior during run-up

That is why you do a run-up in these aircraft that checks many systems, so you can spot those kinds of issues. But the reality is that even if there is an oil leak or missing safety wire, those issues are reviewed (in detail) and fixed in the annual inspection. The aircraft is reliable enough to not worry about it between inspection intervals. For rental/hire aircraft this inspection happens more often, every 100 hours.

Some of the issues may be caught during oil changes as well, which happens every 50 hours (depending on manufacturer recommendations).

Let me give you an example...

I was doing some recurrent training and selected a Piper Cherokee. I was doing the preflight and you can open the cowl on those aircraft. I noticed a significant oil leak behind the controllable pitch mechanism which my instructor and I decided not to fly until the mechanic looked at it. When the mechanic did, he said that it probably needs to be rebuilt but to go ahead and fly it anyway, just make sure that the oil was full prior to flight.

On my 177 we had been flying it all year, when it went into annual it was found that the piston controlling the constant speed propeller was way out of spec and that the hub had corrosion. The entire prop had to be replaced. We were flying it and it was behaving just fine, but could have failed at any time.

The point is that the issues that will stop your engine from running or make your prop run away are usually not visible anyway. Keep it topped up with oil and pay attention during run-up and you should be fine. Usually I take a flashlight and peer around in the compartment as best I can to make sure nothing has taken up residence in the engine, but aside from that, there isn't much else to do preflight.


What are the differences between these types of air cycle machines?

Really not sure what you're asking, nor do I know what these terms you've found mean, so let's start with these drawings and see where we end up.

DC-9 Bleed air enters from the engine (or APU) at bottom left of this drawing and enters the primary heat exchanger. Then it enters the compressor in the ACM and then on to the secondary heat exchanger. From here it enters the turbine and this is the point that the heat loss occurs and cold air enters the water separator and then the cabin of the airplane.

Note the anti-ice screen and the pack anti-ice valve which adds a little heat if the air exiting the turbine is too cold and is causing ice.

The water separator is a cone-shaped cage with a heavy cotton bag over it. This collects condensation in the air and dumps it on to the face of the secondary heat exchanger to cool and improve it's efficiency.

Temperature in the cabin is controlled by the temperature control valve on the left side of the drawing.

737 This system is very similar to the DC-9 and really the main difference is that the pack anti-ice valve here is operated electrically, while on the DC-9 it is done mechanically with a pneumatically operated valve.

757/767 This is a much different system, many more electrical sensors and control. The pack cooling fan is an integral part of the ACM, where on the other two systems they are separate components. The water separators are much more advanced and don't require regular maintenance like on the other systems.

As you can see, these three systems are all basically the same with the only real difference being how they are controlled and some of the ancillary components.


This is my personal experience having nearly lost my medical: If you are in the U.S., you will have to check the box on the application stating that your medical has been denied in the past. You will have to check that box every time you apply in the future. Having nearly had my medical denied in the past, my advice is to 1) find the most senior AME in your area and schedule an appointment for consultation. Explain your situation and take his/her advice. 2) Follow through on that advice (I had to see a well-regarded neurologist for a few hours' worth of exams and interrogation). Bring those results/reports with you to your next AME visit and have him/her send them to the FAA with your next medical application. The FAA's medical office in Oklahoma City will review your case and most likely send you a letter. I was able to get a medical issued the day I applied, however, the letter I received from OK City put me on a six month schedule before the age of 40. I strongly urge you to consult with the most senior AME you can find.

tl;dr - If you have been previously denied. You will have to provide documentation to your AME to overturn the denial.

Caveat: I am only familiar with the U.S./FAA system as a pilot.

[ I'll try to tidy this up when I get home later today ]


What causes lift in aerofoil: Bernouli's principle or Newton's third law?

I think it is erroneous to say that lift is solely produced just because of the Bernoulli's or Newton's law.

Sixty Symbols(A youtube channel) explains the best how a wing actually produces lift.

Instead of explaining I thought this video might help you more than my explanation. And also look at "Incorrect Lift theory" by NASA


In a Practice Forced Landing (PFL), what are Low Key and High Key and how are their locations determined?

Practice (or real) forced landings and (SFO) simulated flame out (or actual flame out - engine failure)  maneuvers are done often by the military in the fashion shown in the pictures below. Part of the reason for this type of maneuver is due to the characteristics of the aircraft involved.  For example, high speed fighter jet aircraft need to fly fast and they use this maneuver to dissipate speed and altitude in a relatively short space.

Regarding the SFO or actual Flame Out:

The High Key  position is generally when the aircraft is somewhere over the first third of the runway and is the point at which the pilot will begin his right/left turn and start his descent (if currently level). If it's an actual flame out, then the aircraft may be in a descent prior to reaching High Key but should be attempting to be at or near the altitude that was practiced during a simulated flame out (when training).

The Low Key position is generally abeam the approach end of the runway.

These "Key" positions serve as altitude and configuration reference points in order to ensure that the aircraft will be at the proper position, speed, and altitude over the end of the runway.

The altitudes (which may vary based on aircraft type) utilized for the SFO and forced landing maneuvers are based on above ground level (AGL) and the AGL altitudes won't change based on runway elevation.

The pictures below show how these maneuvers generally are done:

From: laartcc.org/stm/special-military-procedures