Why aren't departures separated by minimum distance rather than minimum time?

For the FAA(all my answers can be looked up, and expanded upon in FAA Order 7110.65W, Chapter 3 mainly, but I'll try to keep it short), most departures from the same runway use distance for separation. The standard is the lead aircraft is clear of the runway, but most of the time can be shorter under most circumstances. The only times it becomes time based, if it's wake turbulence related, or various conditions of non-radar separation needing to be applied.

In general for runways, aircraft are broken into 3 categories for separation(excluding weight class, which add wake turbulence time if necessary). Category I aircraft are light single engine propeller driven aircraft weighing less than 12,500 lbs (and helicopters). Category II aircraft are light twin engine propeller driven aircraft weighing less than 12,500 lbs. Category III is everything else.

I'll mainly discuss same runway departures, since there's many considerations and it gets complex, and the FAA Order 7110.65 does a fairly good job of depicting and showing this separation standard. For the same runway when both aircraft aircraft departing are category I, the min distance between them is 3,000 feet and airborne. This means that the first aircraft has to be 3,000 feet down the runway and airborne, before the next aircraft starts it's takeoff roll. If the trailing aircraft is a Category II and the first aircraft is a Category I or II,  the distance increases to a separation of 4,500 feet between aircraft. If either aircraft is a Category III aircraft, it's 6,000 feet and airborne required.

Now if both aircraft are IFR, there needs to be IFR separation insured after the runway separation. In most environments the minimum radar separation is 3 nautical miles between aircraft. Now, between jets, the runway separation of 6,000 feet and airborne, will often be right at 3nm between aircraft(due to the speed differential mainly). Other options include turning one aircraft off the path of the other by at least 15 degrees and have them diverge apart.

Wake turbulence is one of the few areas that time is applied. If a heavy(300,000 lbs or greater) is departing in front of anything else, the next aircraft can't start their departure roll for 2 minutes when both are departing from the same intersection on the runway, and 3 minutes if departing the runway from different intersections. And a Super(A380/AN225) I believe are 3 minutes, when departing the same intersection, but I've never worked them in the tower. There are a few other times when time is used, intersections, opposite direction.

For arrivals, all except non-radar separation is distance based.


What is the difference between mist and fog?

Quoting from the METAR decoder:

BR Mist (Foggy conditions with visibilities greater than 5/8 statute mile)

FG Fog (visibility 5/8 statute mile or less)

You may ask "Why 5/8th of a statute mile?"  That's because 5/8ths of a mile is 1,006 meters, or about 1 kilometer.


How does an FBO refer to the parking spots on the ramp?

From the airports I've flown into, it's usually, you're just guided into a spot, and most often, there aren't any lines there, mainly since an FBO should be able to generally serve something as small as a Cessna, to a Gulfstream, or bigger. Flight School Ramps might have painted lines and dedicated parking for their fleet, but they know who will be parking there and what type.


Can TODA ever be shorter than TORA, under any circumstance?

No

Takeoff Distance Available (TODA) can never be shorter than Takeoff Run Available (TORA).

AIM 4-3-6

  Takeoff Distance Available (TODA) – The takeoff run available plus the length of any remaining runway or clearway beyond the far end of the takeoff run available.

I had previously downloaded the FAA runway database and determined there is no TODA less than TORA.  The mysterious airport may have incorrect data or the database is incorrect.

FAA Airport Information

The same database shows that approximately 14% of the runways have an ASDA shorter than TORA.  Multi-engine pilots need to be aware of how their aircrafts performance was created and how to apply the correct declared distances.


You would have to ask someone in the engineering dept at Wipline for an actual number info@wipaire.com.

I have enough float time to be willing to stick my neck out and make a somewhat educated guess. I recall from somewhere that the Caravan on wheels with a feathered prop has a really good L/D by single engine airplane standards, somewhere around 12.

Based on personal experience the glide of most seaplanes is pretty brick-like; I would say a good ballpark would be about a 1/3 to 1/2 reduction in L/D from the land plane.  So for a 208 on amphibs I'm guessing it's going to be between 6 and 8.  If you find out hard data from Wipline, let us know the actual number so I can find out how far off I am.

Fortunately, the PT-6 is so reliable the risk of a power off glide from the engine letting you down is pretty tiny.


Is skin friction drag affected by material?

Indirectly, yes. Friction goes up when dirt and smashed bugs accumulate on the wing. A low surface energy coating might well reduce their stickiness, so the wing collects less dirt and has less roughness. This is especially helpful when it helps to delay the transition from laminar to turbulent flow.

Another way to delay that transition would be a soft surface which could help to dampen the characteristic Tollmien-Schlichting oscillations from which the transition of boundary layer flow from laminar to turbulent springs. Accelerated flow is naturally damped (the amplitude decreases relatively to flow speed), so it stays laminar on a smooth wing. Once the damping turns negative (i.e. the oscillation is increasing), the turbulent transition is imminent. When the wing is not only smooth, but also soft and helps to dampen those Tollmien–Schlichting oscillations, even unaccelerated flow might stay laminar for longer, which again reduces friction drag. So far, I am unaware that this effect has been exploited successfully on an aircraft, though.

The friction between gaseous substances and solids is not affected by the surface energy of the solid, so a direct reduction in viscous drag due to a polytetrafluoroethylene coating will not happen.

I trust you know how drag depends on surface roughness. If not, please feel free to post another question.


Helicopter Flight: What is the reason for decrease in Induced drag with increase in speed?

As you mentioned, the main rotor thrust must support the weight of the helicopter in hover, and must also provide a propulsive force to overcome drag in forward flight.  However, the induced drag is also a function of how the air is deflected downward by the rotor.  The velocity of this downward deflection of air at the rotor is often called induced velocity.  This induced velocity is a function of not just thrust, but also the helicopter forward speed, rate of climb, air density, height above ground (when near the ground it decreases, a phenomena known as ground effect), etc.

Relevant to your question is how the induced velocity decreases as the helicopter goes from hover to moderate forward speed (even though thrust increases).  At hover, the rotor is sitting in its wake with a large induced velocity.  With some speed, the helicopter is moving away from it's wake, resulting in a smaller induced velocity.  This smaller induced velocity increases the angle of the incoming air to the blade, and therefore decreases induced drag (and even overall power required).


Can I display the route which I have created with skyvector.com on google maps?

It's not web based, but you can use Google Earth for this — There are overlays for aeronautical charts available, and you can do all your flight planning by entering routes in Google Earth. Then just turn off the sectional and you'll have the Google Earth satellite imagery to work with.

As an added bonus (relating to your comment about mainly using an Android tabled): Google Earth is available as an Android application (and the plugin version of the chart overlay should work in the tablet app — I know it works in the iOS version of Earth)

BIG SCARY IMPORTANT DISCLAIMER

As the folks who publish that collection of charts will tell you, the charts are not always current and thus should not be used for navigational purposes (much like SkyVector).  You can of course replace the chart graphics with current ones (or locate a chart collection that is current) if you want to, but as you're only using this as a pre-flight planning aid and will be doing your real flight planning with current charts and data the ones provided in the Google Earth Library are probably "good enough" for your purposes.


Are the airspace times of operation days of the week in local or Zulu time?

The VFR chart covering this area shows local times instead.

For this restricted area, it is 7 AM to 8 PM Mountain time MON-FRI.


How can an ATC choose the right flight level and heading for airplanes?

During the enroute portion of the flight at cruising altitude, pilots will have filed a cruise altitude and route based on airplane performance and weather. ATC will not need to change this unless the pilots ask to deviate or there would be a separation issue. Separation will depend on the local regulations and type of airspace and aircraft involved. For airliners this is usually 3 miles laterally or 1,000 feet vertically.

Pilots may request deviations from their filed route due to weather or other reasons. ATC will look at other traffic in the area and determine what changes can safely be made. ATC may also need to give altitude changes to keep them clear of other traffic. If two planes are converging at the same altitude, at least one of them would need to climb or descend.

When arriving at the destination, many airports have stardard terminal arrival (STAR) procedures that pilots use in their route and may give route and altitude instructions. ATC will also have standard procedures for routes and altitudes that will allow arriving aircraft to descend without interfering with departures or other airspace in the area.


Based on this fuel flow chart, why isn't it more optimum to remain at an intermediate altitude rather than climbing?

When airplane mass, altitude, N1 (engine spool speed) and Mach number change together, it is very hard to come to a meaningful conclusion what is better for fuel flow. However, you see that the grey boxes tend to show the smallest fuel flow and they sit at the upper altitudes, so altitude seems to help. Going above 90% N1, however, seems to increase fuel flow again.
With increasing altitude, the flight Mach number needs to be increased to keep indicated airspeed constant. I expect that the chart lists trim points at or near the optimum polar point for cruise, at least that is what the almost constant indicated airspeed for each mass suggests. With increasing Mach, drag goes up but so does the distance covered per time, so there is again an optimum where the transsonic drag increase is still tolerable and outweighed by the higher speed over ground.
Therefore, higher flight speed is one reason why airliners like to climb to the tropopause. But there is more:
The thermodynamic efficiency of a heat machine grows with the ratio of temperatures in its thermodynamic cycle. Since the lowest temperature is determined by outside air, and outside air temperature drops with altitude while the top temperature is limited by the engine's materials, flying higher improves the thermodynamic efficiency of the engines.


How to get IATA code for the Airline PSS system?

Try below link, you can type PSS system name and get the code for the same. However, not all PSS are IATA registered.

https://www.iata.org/en/publications/directories/code-search/


What kind of Chinook helicopter/airplane hybrid is this?

It‘s a BV-347 technology demonstrator:

  In 1969, the Army and then-Boeing Vertol entered into a partnership to improve upon their cargo helicopter fleet, and thus the BV-347 was borne from a CH-47A Chinook that was provided by the Army as a technology demonstrator, according to retired CW5 Jim Kale, who now serves as a tour guide for the U.S. Army Aviation Museum.

Primary objectives as found in above article:

  The BV-347 was tested for more than two years and flew about 350 hours with the intention to meet five primary goals: improve flying qualities with external loads and instrument flight; im-prove stability, control and maneuverability in hover flight and forward flight with high gross weight; reduce rotor noise; reduce vibration stress; and create a modern cockpit environment with improved instrument and navigation displays.

The wing was intended to provide extra lift (works in forward flight only, of course), but apparently didn’t add net benefit:

  The wings were added as a means to improve lift, and although the addition served its purpose, the added weight canceled out any positive effects it provided [...].


Why don't light-up runway numbers similar to runway lights?

Because it is fairly easy to determine which runway is the correct one by other means.

Runways are numbered based on their compass direction. The runway number will be the compass direction divided by 10 - for example, a runway with a direction of 150 degrees would be numbered 15.
This makes it possible to verify that you are using the correct runway by simply looking at your compass, to make sure the runway is pointing in the right direction. Even during day time in nice weather, this check is routinely performed before taking off by most pilots.

Runway identifiers for parallel runways are suffixed with an 'L' for the left runway and an 'R' for the right runway (from the pilot perspective). At airports with three parallel runways, the identifier of the middle one will be suffixed with 'C' for center.
When approaching an airport at night, the runways will - as you point out - be clearly lit. It is easy for the pilot to spot any parallel runways and make sure they are approaching the correct one, simply by observing the relative position of the runways.

During night or periods with degraded visibility, most traffic will make use of precision instrument approach systems, such as ILS, which will guide the plane precisely to the correct runway, without much risk for confusion.

On the ground, clear airport signage make it nearly impossible to mistake which runway you are on.

In addition, at busy airports with multiple runways, air traffic control service is likely to be provided. Air traffic controllers will monitor all aircraft movements on the maneuvering area and in the vicinity of the aerodrome, and will quickly be able to notify any pilot who is about to use a wrong runway.

Another point is that lighted runway numbers would probably be pretty ineffecient, as the relatively small size of runway numbers would make it impossible to read them from a distance, even if they were lit. A pilot approaching a wrong runway would notice this too late to be able to make corrections, and would have to perform a missed approach. Granted, doing so would in many cases be better than landing on the wrong runway.


Does DO-178C require static code analysis for level A software?

DO-178C is a means of compliance, so it sets out what you need to do to show you are meeting your required safety levels in your design.  It does not give advice on what methods you might use along the way.

I have seen static analysis used as part of the process, often with hardware integration and system testing.

DO-178 tools need to be qualified for DO-178 if you are using them to test your software.  I am not aware of anyone successfully using tools qualified for other standards (e.g. MISRA) in avionics.


Can I fly a quadcopter over 50m above a property I don't own according to the UK's Dronecode?

Take a look at page 2 of the "Dronecode". The illustration makes it quite obvious that the 50 metres refers to both vertical and horizontal distance:


There appears to be no emergency. The flight was diverted at 16:58 EST and landed at Bradley International Airport at 17:03 EST. The same flight on 6th Feb landed at Boston at 16:46 EST. So basically, the flight was in the air only for an extra 15 minutes, compared to the scheduled time.
According to § 121.639 Fuel supply: All domestic operations.:

No person may dispatch or take off an airplane unless it has enough fuel—
(a) To fly to the airport to which it is dispatched;
(b) Thereafter, to fly to and land at the most distant alternate airport (where required) for the airport to which dispatched; and
(c) Thereafter, to fly for 45 minutes at normal cruising fuel consumption

So basically, the pilot diverted because the holding time was another 60 minutes and that would've eaten into fuel reserves.

I think the captain meant that the aircraft had only 10 minutes of fuel till he had to dip into reserves (or fly the alternate- it depends) and diverted because of the 60 minute waiting time. He could've been more clear though.

The pilot would've declared a fuel emergency if there was one. So, I think there was none.

Its quite uncommon for aircraft to land on 10 minutes of reserve fuel, though it has happened. In fact, some aircraft have run out of fuel.

You can find details about the ATC in liveatc's audio archives.


What problems can be encountered if an airplane does not undergo wind tunnel testing?

For decades, there was no wind tunnel testing performed. There will be, of course, more unknowns about performance and flight characteristics, but with modern computer simulation technology those can be greatly reduced.


Which timezone do airspaces that cross a time zone boundary belong to on a VFR sectional?

The times listed on the margin of the VFR Sectional chart are generally local time. In fact, the effective times that the FAA lists are also published in local time. However, in the case of a Special Use Airspace (SUA) that covers multiple time zones, the FAA specifies which time zone is used for local time.

The FAA publishes these details of SUA in the JO 7400.10A "Special Use Airspace".

You ask specifically about the Bronco 3 MOA. In the 7400.10A, the following details are currently published for the Bronco 3:

So, while Fort Worth Center is the controlling agency, the times of use are given in Mountain Time. This makes sense since the using agency is out of Cannon AFB in New Mexico.

Compare this to the nearby Lancer MOA (entirely in Central Time) for which the 7400.10A only lists the time as "local time":


Does ATC provide ILS frequency and course setting for the runway in use?

When nearing their destination, pilots will be checking weather and airport information. This will let them know which runways are being used for landings and what type of approaches are being used. ATC will also tell each aircraft what runway and approach they can expect in advance, as in your example, "Expect ILS approach runway 24 left".

Once the pilots know the runway and approach, they can reference the corresponding chart (like the ones in this question). Pilots are required to have these charts available, traditionally paper copies but more recently being replaced by electronic copies. This will give them all of the information about the procedure, including the localizer frequency. Besides programming the frequency, the crew will also review the other important requirements of the approach and landing.

ATC does have access to this information as well, and can provide it if they feel they need to confirm the pilot has the right frequency, or if the pilot asks.


How should an aviation novice evaluate 'flight experience' or 'flight training' services?

For Laser dogfighting, you linked to SkyCombatAce.
I did the Sky Combat Ace experience in Las Vegas about 4 years ago, and there were no lasers involved.  Rather, the back-seat instructor judged when you were in position for a kill shot, and just radio'd "kill", at which point the other plane activated smoke and started spinning.
Although I enjoyed my experience with them, its worth noting that they'd have 2 major crashes resulting in 4 deaths in about the last two years.   The investigations are still pending, but personally, I don't think it looks good.
In the April 2016 crash, the local weather was announcing thunderstorms in the area, and the 3 planes took off anyway, initially requesting flight directly towards the storms until the Tower Controller suggested they reconsider.  They either seemed oblivious to the local weather, or didn't care about it.  It has not yet been determined if that was a factor in the crash.
On the one hand, I enjoyed my flight.  On the other hand, I now have serious reservations about their operation, and would not consider flying with them again.

As far as the "taking the controls" aspect:  I had my Private Pilot's license at the time I flew with them, so I'm familiar with flying, although not at the performance levels of those planes.  However, "taking the controls" meant the ailerons and elevator only; no throttle and no rudder (controlled by the instructor).  In that sense, it was a lot like a simplistic video game with a joystick.

Update: July, 2018
The Factual Report on the first accident, in Henderson, NV is now available on the NTSB website.  The report took over two years from the incident to come out, which is atypical (6 months to 1 year is more common).
The report had two concerning findings:

First and foremost, the report finds the pilot had detectable levels of THC (marijuana) in his blood and tissue.  The report points out that it is impossible to tell how recently the pilot used it or if he was impaired at all. However, that he had any amount of an illegal substance (marijuana did not become legal in Nevada until several months after the accident) is deeply disturbing.

Secondly, the report calls into question if the flight operation is operated legally by CFR 14.91 and .61 (Instructional Flights), and suggests they may have been legally required to hold a part 119 air carrier / commercial operator certificate and operate under the stricter 121 or 135 rules.

I will reiterate that I enjoyed myself during my flight with SCA.  But after two fatal accidents and this incredibly concerning report, I cannot recommend that anyone fly with them until major legal and operational issues are resolved.

Update: May, 2021
A GoPro camera which captured much of the second crash was found after two years.
The additional information it helped reveal is disturbing.  A detailed article is here.


Is constant air pressure maintained inside the fuselage?

For the purposes of air pressure inside aircraft, they are broken down into two broad categories:

Unpressurized - These aircraft are typically piston powered and can't go very high, so do not even attempt to regulate the air pressure inside the fuselage.
Pressurized - These aircraft do maintain pressurization in the fuselage, but it isn't constant beyond a certain point.

The category determines the answer to your question:

Unpressurized Aircraft

Unpressurized aircraft are not built air-tight for a couple of reasons:

It is very hard to make something as large as an airplane truly air-tight, and keep it that way.  Over time, seals will start to leak, fittings will loosen, etc.
The fuselage would have to be much stronger to withstand the pressure difference between the inside and the outside.  This would make them heavier and more expensive.
There isn't much need.  These airplanes don't fly high enough to really require a pressurized fuselage and a person can breathe more or less normally even though you aren't at sea level.  (Think of people that live on mountains.)

Pressurized Aircraft

Without going into the details of how an aircraft is pressurized (which isn't really relevant to your question), the air pressure inside the fuselage of a pressurized aircraft is usually maintained at sea level pressure up to a certain point.  However, the fuselage is designed to withstand a particular maximum differential air pressure, so in order to protect it (basically keep it from "popping" when the air pressure outside the airplane drops too low), the pressure is allowed to decrease when needed.

In typical jet airplanes, the pressure inside portions of the airplane (typically the passenger compartment, some of the cargo holds, and maybe an avionics bay) at cruising altitude is maintained at a pressure which corresponds to an outside air pressure at an altitude of about 5,000 - 8,000 feet (referred to as "cabin altitude"), depending on the cruising altitude and the design of the airplane.


Is a braking rotation immediately after touching down a known maneuver?

There was a bit of a bounce and skip at touchdown along with the nosewheel bouncing due to the uneven ground and aggressive landing.  He was probably doing it to hold the nosewheel off after the bounce, to reduce the main wheel contact force somewhat (the normal soft field landing technique) but it looks to me like he overcontrolled with the pitch a bit.
There will be relatively little braking friction so initially you would get better deceleration with the high pitch attitude, but that benefit declines quickly as you slow down and you quickly become reliant on braking and reversers (If the grass is wet, you have about as much braking as compacted, glazed snow, that is, not much; they would have to makes sure the ground was dry or he would have slid into the next field).
If you're on pavement, you want maximum braking as soon as possible, which means you want the lift dumpers out as soon as possible, so you wouldn't use that sort of technique; it's just get the mains on, then fly the nosewheel on, then hard on the brakes right away.  You'd have a longer landing run on pavement trying to land like that, plus there's too much risk of bouncing the whole thing back in the air just as the lift dumpers are extending or about to extend, which results in follow-on touchdown that will rattle teeth and blow tires.


NACA itself published quite a few papers on their submerged duct design. As a starter have a look at:

Mossman, Emmet A., et al. NACA-RM-A7I30 "An experimental investigation of the design variables for NACA submerged duct entrances", 08. January 1948
Frick, Charles W., et al. NACA-ACR-5I20 "An Experimental Investigation of NACA Submerged-Duct Entrances", 01. October 1945

The NASA Technical Reports Server as well as the UK archive of digitised NACA Reports offer a lot more material for further investigation.


Is flight data recorder erased after every flight?

Flight data recorders have changed over the years and evolved to what they are today. Modern recorders are recording up to 88 parameters. The storage of the recorder is dependent on the range of the aircraft. Early recorders were using a circular tape that ran through the recorder. E.g. loop recording all the data and automatically overwriting the oldest data on the tape.
The recorder of a Boeing 777 is based around modern solid state storage, capable of recording up to 25 hours continuously. Modern flight recorders are still recording continuously, so after the initial 25 hours, the storage is full. It will then start overwriting the oldest datablock stored. This ensures that you will always have the last 25 hours of data before a crash available for research.
The following quote comes from AERO Magazine Issue 02 - Spring 1998:

Flight data recorders were first introduced in the 1950s. Many first-generation FDRs used metal foil as the recording medium, with each single strip of foil capable of recording 200 to 400 hr of data. This metal foil was housed in a crash- survivable box installed in the aft end of an airplane. Beginning in 1965, FDRs (commonly known as "black boxes") were required to be painted bright orange or bright yellow, making them easier to locate at a crash site.
Second-generation FDRs were introduced in the 1970s as the requirement to record more data increased, but they were unable to process the larger amounts of incoming sensor data. The solution was development of the flight data acquisition unit (FDAU).
As shown in figure 2, the FDAU processes sensor data, then digitizes and formats it for transmission to the FDR. The second-generation digital FDR (DFDR) uses tape similar to audio recording tape. The tape is 300 to 500 ft long and can record up to 25 hr of data. It is stored in a cassette device mounted in a crash-protected enclosure.
FAA rule changes in the late 1980s required the first-generation FDRs to be replaced with digital recorders. Many of the older FDRs were replaced with second-generation magnetic tape recorders that can process incoming data without an FDAU. Most of these DFDRs can process up to 18 input parameters (signals). This requirement was based upon an airplane with four engines and a requirement to record 11 operational parameters for up to 25 hours (see "Parameters Explained" below).
Another FAA rule change that took effect October 11, 1991, led to the installation of digital FDAUs (DFDAUs) and DFDRs with solid-state memory on all Boeing airplanes before delivery. This FDR system was required to record a minimum of 34 parameter groups. The DFDAU processes approximately 100 different sensor signals per second for transmission to the DFDR, which uses electronics to accommodate data for a 25-hr period.
Today all Boeing current-production models use DFDR systems, which will store 64 12-bit words per second (wps) over a 25-hr period in electronic memory. At the end of the 25 hours, the DFDR will begin recording the most recent data over the oldest data. No tape removal is required with these systems. Each of these systems on every Boeing model (except the 777) have at least two data frames that are transmitted from the DFDAU to the DFDR (see "What Is a Data Frame?" below).
These separate data frames accommodate the different regulatory agency requirements. A 128-wps DFDR was available for the Boeing 777 and MD-90, allowing the development of one data frame that incorporated all regulatory agency requirements and that required operators to develop only one data frame decode algorithm. "How a FAA Rule Is Changed", below, explains the basis on which the FAA may propose rule changes.

Source


Can a non multi-engine rated pilot get a complex endorsement in a multi-engine aircraft?

If the airplane meets the definition, which almost all multi-engine pistons will, then you can get your complex endorsement. There is even one training center that advertises getting your multi and complex at the same time.

  §61.1   Applicability and definitions.

  Complex airplane means an airplane that has a retractable landing
  gear, flaps, and a controllable pitch propeller, including airplanes
  equipped with an engine control system consisting of a digital
  computer and associated accessories for controlling the engine and
  propeller, such as a full authority digital engine control; or, in the
  case of a seaplane, flaps and a controllable pitch propeller,
  including seaplanes equipped with an engine control system consisting
  of a digital computer and associated accessories for controlling the
  engine and propeller, such as a full authority digital engine control.

  §61.31   Type rating requirements, additional training, and
  authorization requirements.

  (e) Additional training required for operating complex airplanes. (1)
  Except as provided in paragraph (e)(2) of this section, no person may
  act as pilot in command of a complex airplane, unless the person has—

  (i) Received and logged ground and flight training from an authorized
  instructor in a complex airplane, or in a full flight simulator or
  flight training device that is representative of a complex airplane,
  and has been found proficient in the operation and systems of the
  airplane; and

  (ii) Received a one-time endorsement in the pilot's logbook from an
  authorized instructor who certifies the person is proficient to
  operate a complex airplane.

  Complex Airplane Endorsement

  Learn to fly aircraft with retractable landing gear, controllable
  flaps, and a controllable propeller using our Piper Seminole PA-44-180
  airplane. You can earn your complex endorsement, or combine your
  training to earn your complex endorsement and multi-engine rating.*


Can you have an AME also sign off on your FAA BasicMed paperwork?

From the FAA's FAQ:

  Q35: Can my AME provide the medical examinations under BasicMed?

  A:
  All AMEs are state-licensed physicians and may elect to conduct
  physical examinations required under BasicMed. But the FAA does not
  require AMEs to provide medical examinations under BasicMed. It is up
  to the individual AMEs to decide whether to offer BasicMed medical
  examinations based on medical practice considerations

The key words in there are "may elect to". There have been several discussions about this on AOPA's forums (members only) and people's experience so far is that most AMEs won't do BasicMed. The only specific reason I've heard is liability: one explanation I read is that when acting as an AME, the physician is representing the federal government and is therefore more or less immune from liability. But if he does a BasicMed exam he's acting as a regular state physician, and his liability insurance may or may not allow it. So you just have to ask your AME if he'll do BasicMed or not.

As for whether BasicMed affects a third-class medical or vice versa, this is from the same FAQ:

  Q2: How does BasicMed affect FAA medical certificates? Does FAA still
  offer the third class medical?

  A: BasicMed does not affect medical
  certificates at all and did not do away with third-class medical
  certification. In fact, third-class medical certification is still
  required for GA aircraft and flights that do not meet the criteria for
  BasicMed. Nothing about the FAA’s medical certificate program has
  changed with BasicMed, and you can still apply for a first, second, or
  third class medical the way you always have. BasicMed is merely an
  additional qualification you can use to fly, in lieu of holding a
  medical certificate.

And this:

  Q6: Can I exercise BasicMed and hold a medical certificate at the same
  time?

  A: Yes. If you are operating under BasicMed, then you must comply with
  the BasicMed operating limitations (e.g. flying only within the U.S.
  and at or less than 250 knots). When operating under BasicMed, you are
  not exercising the privileges of your medical certificate.

Simply put, there is no link or dependency at all between an FAA medical and BasicMed. Your AME might do one physical exam and sign off both at the same time for the sake of efficiency, but that doesn't change anything about the renewal dates.


Is it always advisable for passengers to wear seat belts when a 747 is on final approach?

Yes, it is always advisable for passengers to wear the provided safety belts in all phases of flight. This is especially true for aircraft on takeoff, landing, in low level flight, or in any other flight regimes that are especially prone to turbulence or other risk exposure.

A large, heavy aircraft—such as a B747—will be less affected by wake or mechanical turbulence than would a smaller aircraft—such as a CRJ200 or a C172. However, even large, heavy aircraft can be subjected to severe turbulence that could result in injury or death if passengers are not restrained by appropriate safety belts.

Additionally, for flights conducted under 14 CFR 121—which I am confident is a majority of the US operated passenger flights involving the B747 (though not, obviously, Air Force One pictured in the question above)—passengers are generally required to:

  occupy an approved seat or berth with a separate safety belt properly secured about him or her during movement on the surface, takeoff, and landing
  Excerpted from 14 CFR 121.311 (b)


Does the dihedral effect happen during coordinated flight?

No.

The dihedral effect depends on a flow asymmetry between left and right wing. Coordinated flight means that both wings have the same flow conditions, and the only asymmetry between both is caused by control deflections.

You do have a flow asymmetry during a turn (coordinated or not) from the speed difference between the inner and the outer wing which grows with the turn rate and wing span. This does indeed cause more lift on the outer wing, but due to the difference in dynamic pressure, not due to dihedral. Since dihedral causes a side force component of lift, you can argue that the outer wing creates more side force which pushes the plane into the turn. But the pilot will compensate the difference in dynamic pressure with the ailerons to stop any rolling motion once the desired turn rate is stabilized. This will also equal the lift on both wings.

Another asymmetry is caused by the location of the vertical tail aft of the center of gravity. Essentially, the tail swings around during the turn, which causes a sideslip condition at the vertical tail. The result is a side force which grows with turn rate and tail lever arm, and due to the high location of most vertical tails also causes a small rolling moment. But again the wing's dihedral has nothing to do with that.

Dihedral only comes into play if you build up a sideslip, and then the turn is not coordinated any longer. @Zeus is right with his point that dihedral stabilizes the aircraft and makes it easier to keep the turn a coordinated one. Now we can split hairs all day if flying in turbulence makes a perfectly coordinated turn impossible. When it comes to dynamic stability, a moderate dihedral effect is highly recommended.


At KOAK, how can I get a passenger from the GA terminal to the commercial terminal?

This is a specific question but I think my advice applies to most FBOs.
I fly out of OAK and your best bet is to try signature. Buy some fuel, ask nicely and if they aren't too busy they might be able to accommodate you.
They have given me rides on the ramp before when my usual gate was closed due to a power outage.

If not, then call a rideshare/cab


Does an rc plane tail also have airfoil or is it just flat material?

A flat piece of wood with rounded edges will work fine.

The tail's job of producing downforce doesn't require the lift coefficients or angle of attack range required of the main wing, so the actual airfoil shape is not that important especially at low speeds, even more so under the low Reynolds numbers ("thick" air) that RC airplanes work at.

In fact most fabric light aircraft get by with what is effectively a flat surface wind deflector, like this Super Cub.


Where can a realtime map showing all flights and all dangerous areas be found?

Actually what constitutes a "perilous zone" is arbitrarily decided by countries or airlines . Ergo, there are no zones that have been defined by the International Civil Aviation Organization as perilous .

http://www.icao.int/Pages/default.aspx

For example as on this date British Airways and Qantas  have demarcated Ukrainian airspace as dangerous and is therefore avoiding it .

As far as a realtime map of flights are concerned who may take a look at Flightradar24

http://www.flightradar24.com/20,77/7


Selecting radials for radial interception

This is a terminology problem - and I think you're actually both right but you need to learn the terminology. Radials always radiate out from the VOR.
You should absolutely always set the needle to the heading you intend to fly in order to avoid reverse sensing.
However, if you're intending to "fly inbound on the 240 radial" then you're actually on the reciprocal heading of 060 - which is what should be set on your OBS. The flag should indicate "TO".
If you're flying outbound on 180 then you should set 180 on the OBS and the flag should indicate "FROM".


Which CPUs and programming languages are used in new airliner flight control systems?

Note: I focused more on changes in aviation hardware and software than what's currently used since the question linked about programming languages is still current for "new" aircraft.  I do not wish to duplicate that question or its answers.  In my opinion C++, C#, and Ada will probably be the dominant programming languages for avionics for the next decade at least.

First, you've got to understand the life cycle of aircraft.  Many aircraft are in service for more than 30 years.  The avionics do get updates (whether adding new features, fixing bugs, or adding in compliance to meet mandates). However, the bulk of the work is done during initial development of the software and hardware.  The configuration is then mostly fixed until that generation of avionics is replaced by the manufacturer or retrofitted by another manufacturer.

So What's Changed in Practice?

If the avionics goes through a generational update (like CRT's to LCD screens), anything changed has to be worth the cost, so usually not much is changed.  Maybe the CPU, but definitely not the programming language. For example, the G1000 was out for 12 years before releasing another generation of hardware (although in the meantime they published numerous software updates for hardware compatibility and synthetic vision and such).

Similarly, Avidyne Entegra was out for five years and continuously adding major features like data link weather and LPV approach before it finally upgraded the hardware in release 9 in 2009.  Falcon jets like the Falcon 900 had a software and hardware update to their avionics in 2011, but that upgrade was based on Primus Epic family of hardware and software, whose first generation was already 9 years old.  I believe all the 900's were still running the old 1996 hardware before the 2011 upgrade.  On the other end of the spectrum from these slow upgrades, the military's JSF system is designed to be upgraded easily every few years (but they don't say just how often).

Why Not Make More Frequent Upgrades?

What drives value in avionics isn't usually exotic new features and definitely not computing performance.  Value is driven by reliability, compliance to mandates, and safety-compliance.  This requires features that are simple enough for the engineer and the pilot to understand and are robust enough to have hundreds of lives depend on it. So the new features being added generally require little extra performance, and there's little incentive for cutting-edge technology or the latest programming paradigms like cloud computing, machine learning, or object orientation.

An engineer at Rockwell Collins stated something that applies to all avionics "In the past, we struggled to fit everything we needed to do into the size of processor and speeds we had and how to get all those bits over the interfaces we had. With the processors we have now and fiber interfaces, that is no longer a concern... Now the problem is how to manage and design good, trouble-free software and test all the lines of code involved. So now that we have all the processing and bandwidth we need, we have to make sure we can use it and not design ourselves into a corner."

Verification is one of the biggest driving factors (and costs) in processor and programming language usage.  All hardware and software must have a safety level attached to it, with the most critical functions (like avionics for autoland) considered "Level A" meaning such a failure of the avionics could be catastrophic.  In order to achieve the stringent safety requirements for Level A software (which is often one such failure per 10^9 flight hours), the software and hardware need to be exhaustively tested to ensure nothing will ever go wrong.  That includes covering every condition on every line of code.  Most tools developed to work with your programming language and software architecture needs to be formally verified (usually called "qualified") as well. On top of that all, costly flight testing needs to be done to evaluate any changes.  This creates a lot of inertia and means a complete overhaul of an existing product or starting from scratch for a new product just to get a "faster system" is often not cost-effective.

What about support for new CPU features?

Virtualization (allowing different OS's to act like they're running by themselves but are actually running with a layer between themselves and the bare hardware) and multi-core processing is now supported by some real-time OS's for commercial off-the-shelf processors. These have to follow the standards in DO-332 and other materials.  According to my 2013 text, this is still in the investigatory phase and no avionics with these features have been certified.  The main issue is that multi-core processors don't just have more features, but they have more features that are not comprehensively documented or testable. For more information on issues with use of multi-core see the FAA's CAST 32 and this presentation.


What airspace are ultralight pilots allowed to use?

Ultralights are regulated under 14 CFR 103. There are very few regulations that apply to them, but there are specific rules on airspace in 103.17:

  §103.17   Operations in certain airspace.

  No person may operate an ultralight vehicle within Class A, Class B,
  Class C, or Class D airspace or within the lateral boundaries of the
  surface area of Class E airspace designated for an airport unless that
  person has prior authorization from the ATC facility having
  jurisdiction over that airspace.

That means, you can fly in (most) class E airspace and all class G airspace. You can find more information about those airspace classes in this question.

As for your other questions:

A flight plan isn't required even for aircraft, and ultralights aren't subject to the regulations that would require them anyway
Ultralights aren't required to have radios or talk to anyone; you usually fly so low that you aren't in anyone's way
It's not at all the same as flying a Cessna; in fact, you don't even need a pilot's license to fly an ultralight
See this question for information about launching from national parks; state parks would be subject to state law instead but the principles are probably the same

You might want to look through all our ultralight questions for more information.


Mapping starts with basemaps, with topos (DEMs or digital elevation models) and geographic features.  Then cultural overlays are added.

The charts in US utilize a national spatial reference system. Today this is done with GIS/Mapping software. Then overlays for aviation data, such as man made obstructions, and air navigation data is added.

The (old) process has been the topic of many articles in pilot journals. The newer process is rapidly evolving, as the government transitions to AWS / cloud based applications.

To address your questions, the DEMs may have been created with RADAR and integrated with topo data, but today LIDAR is the norm.  LIDAR data helps with man made structures as well, while not as good as SAR RADAR, it can still show catenary and power line structures.  Those metallic structures show up very well in SAR due to their conductivity.


Why would the Pakistan airspace closure cancel flights not headed to Pakistan itself?

To give an example of how flights can be affected by this in ways to make them impossible, Iranian airspace is closed from sunset to sunrise (unless things have changed recently).
Any aircraft that due to the closure of Pakistani airspace would need to cross Iranian airspace and be unable to do so because of that closure now needs to be cancelled or rescheduled.

Also, if the diversion around Pakistani airspace would stretch the endurance of an aircraft beyond what fuel it can carry, it cannot fly the route.

Or the diversion would cause such a delay in the schedule that it causes too much problems with the overall scheduling of the airline. Such things tend to have a ripple effect. One flight gets delayed by several hours, dozens of others get delayed as a direct result, hundreds more can suffer delays in the end.

Also, some airports only operate during daylight hours. A diversion around Pakistan might mean the flight can't make it to one such airports before sunset and thus can't land at its intended destination. Now the airline has 2 options, divert to another airport, arrange for bus or train transport for all the passengers, and in the morning yet another hop to the intended destination to pick up the new passengers, or cancel the flight.


The AFDS and A/T do not control to a speed which is less than minimum speed for the current flap configuration?

It means you cannot make Autopilot/Flight Director System and Autothrottle fly a target speed below your minimum speed for the configuration. If you were trying to set e.g. 50kts as your speed target, it would be ignored and replaced with the appropriate minimum speed.


Are there different symbols or graphics to identify different types of GA fuels?

As Walker notes in his answer AvGas is typically noted by color when talking about telling it apart. In terms of aircraft markings for fuel this is governed by FAA FAR 23.1557 Miscellaneous markings and placards. and some more notes in this AC,

  (c)Fuel, oil, and coolant filler openings. The following apply:

(1) Fuel filler openings must be marked at or near the filler cover with-

  (i) For reciprocating engine-powered airplanes -

    (A) The word “Avgas”; and

    (B) The minimum fuel grade.

These are fairly simple regulations to comply with so there is a wide variety of markings available, but the end results tends to be a decal looking something like this:

(source)

Above ground storage tanks will also have to comply with local state regulations on petroleum storage, here are the New Hampshire regulations as an example. Generally this will require an NFPA style decal but pilots dont really use those to identify anything. The typical signage for 100LL is a red back, white fount, all caps AVGAS 100LL this is common on tanks,

and trucks alike,

(source)

(source)

Its also important that you as the pilot are present for fueling both to verify type and quantity. If there is any doubt about what is in a truck or at a pump some should be pumped into a canister and verified by color before fueling an aircraft.


How do the compressor stages keep spinning after start in a free turbine?

In a C20-250 engine the compressor section is driven by the high pressure turbine (Ng spool, not N1) independent of the power turbine.  The power turbine drives the gearbox and subsequently the output shaft via a concentric driveshaft to the gas core spool.

I believe you’re confusing the configuration of this engine by assuming that all free turbine turboshaft engines are laid out similar to a PWAC PT-6 engine.   While the PT-6 design certainly excels in terms of simplicity as well as modularity for ease of maintenance, it is not necessarily the only configuration for free turbine engine. Plenty of other free turbine turboshafts have other unorthodox layouts but all operate according to the same principles.

A cutaway of the C20-250 engine appears below.  Note the non-axisymmetric air channel carrying air from the last stage of the compressor section to the aftmost part of the engine for introduction into the single can-type combustor.


Is it coincidence that the B-2 and YB-49 flying wings have exactly the same wingspan?

A random guess without any supporting information. (please edit or delete if this turns out to be inaccurate)

I would guess the logistics of manufacturing. It could the space needed for handling the aircraft in and/or out of manufacturing buildings.
The B-2 program was wildly expensive due to the large number of new technologies involved.

So I guess it was a prudent, maybe even progam-saving decision, to use existing manufacturing facilities are far as possible.


Why would Boeing's MCAS be preferable to a modified Feel and Centering Unit?

On the 737 NG, at high angles of attack, the nose of the plane would naturally pitch down, helping to recover from a stall and to increase airspeed.

The larger engine nacelles on the 737 MAX are located forward of the center of gravity, which means that at high angles of attack they are pushing the nose up. MCAS helps to push the nose down in this situation, similar to how the 737 NG would behave.

The added nose down trim has the side effect of requiring more elevator input at high angles of attack, but that was not the primary purpose.

There are several reasons that the Feel and Centering Unit would have a difficult time providing similar functionality:

The airplane should pitch down even the absence of control input, so it could not be done by simply changing the way the elevators respond to pilot input.
MCAS takes input from angle of attack, altitude, flap position, and airspeed. The Feel and Centering Unit currently just senses airspeed, so it would somehow need to get the other inputs.
The Feel and Centering Unit is a mechanical computer, so adding new inputs and changing the behavior could be very complex to design and certify.

Another possibility would be to use the Mach Trim system to adjust the Feel and Centering Unit. The Mach Trim system uses the flight computer to adjust the elevator neutral position to provide stability at higher speeds. While the flight computer should have all of the information needed, stabilizer trim provides much more control authority.


Are there diversion points for southern Pacific great circle route flights?

This particular flight was a Boeing 747 flying from YSSY (Sidney) to SCEL (Santiago).  Because a 747 has more than two engines, they don't have specific time limits on how far from land that they can fly like two engine airplanes do.

That being said, they do have to carry enough fuel to make it to a suitable airport in the event that the airplane depressurizes or it has an engine failure at any point along their route.1.  This doesn't mean that they have to make it all of the way to their destination in the event of a problem though.  They use en-route diversion airports and have predefined points on their flight plan which tell them where to divert to at any given point during the flight.

You will notice on this flight (see the images below) that their planned route is considerably further North than the shorter great circle route.  This is probably so that they can use NTAA (Tahiti) as a diversion airport if they have a problem.  The route is also optimized for the current winds at the cruising altitude, so it may be more fuel efficient to go out of the way in order to have more favorable winds.

In this case, without seeing their actual dispatch paperwork we can't know for sure whether or not they could have even flown the great circle route with the amount of fuel that the airplane can hold, but we'll just assume that they are using NTAA as an ETOPS airport for the purposes of this discussion.  That being said, we will use the following airports as our ETOPS diversion airports:  NZCH, NTAA, and SCEL.  In this case, their diversion plan in the event of an emergency would probably be something like this:

From takeoff (YSSY) until a point a little less than half way to NZCH (New Zealand)2 they would divert back to their point of departure2
From a little less than half way to NZCH until a point around 46W52 they would divert to NZCH.
Between the points that would be around 46W52 and 47W25 they would divert to NTAA.
After 47W25 they would continue on to their destination (SCEL) because it would be faster than turning around and going back to any of the other airports.

Each of the points takes wind into consideration, and as they pass each one they will always know which airport that they can reach in the least amount of time.  The most important thing is that they always have enough fuel to make it somewhere safe in the event of an emergency.

Filed Route

Great Circle Route

1 They also have to carry enough fuel to fly to their alternate airport and additional contingency fuel.  One thing to keep in mind is that a jet burns considerably more fuel at low altitudes than they do at their optimum altitude, so they have to carry a lot of extra fuel to meet this (and other) requirement.

2 If they turned around at the exact halfway point, it would take them longer to return than to continue because of the East winds.

Regulations

For those of you interested in the actual fuel requirements for a flight like this, the US regulations are listed in 14 CFR 121.  I'll use these as an example (other countries will be very similar, but I know these.)

You will notice that almost every line of the regulations listed here will require extra fuel to be on board the airplane. (Look for the ✈ symbol next to each one that I have added.)  Fortunately, it isn't quite as bad as it looks though, because some of the fuel that is pumped into the airplane can be used for more than one purpose.  For instance, a portion of the fuel may be used to divert to an ETOPS airport and used to fly to your destination, because they will only be doing one or the other.  The pertinent regulations are summarized here:

  §121.645 - Fuel supply: Turbine-engine powered airplanes...

  ...

  (b) For any certificate holder conducting flag or supplemental
  operations outside the 48 contiguous United States and the District of
  Columbia, unless authorized by the Administrator in the operations
  specifications, no person may release for flight or takeoff a
  turbine-engine powered airplane (other than a turbo-propeller powered
  airplane) unless, considering wind and other weather conditions
  expected, it has enough fuel—

  ✈ (1) To fly to and land at the airport to which it is released;

  ✈ (2) After that, to fly for a period of 10 percent of the total time
  required to fly from the airport of departure to, and land at, the
  airport to which it was released;

  ✈ (3) After that, to fly to and land at the most distant alternate
  airport specified in the flight release, if an alternate is required;
  and

  ✈ (4) After that, to fly for 30 minutes at holding speed at 1,500 feet
  above the alternate airport (or the destination airport if no
  alternate is required) under standard temperature conditions.

  ...

  §121.646 - En-route fuel supply: flag and supplemental operations.

  (a) No person may dispatch or release for flight a turbine-engine
  powered airplane with more than two engines for a flight more than 90
  minutes (with all engines operating at cruise power) from an Adequate
  Airport unless the following fuel supply requirements are met:

  (1) The airplane has enough fuel to meet the requirements of
  §121.645(b);

  ✈ (2) The airplane has enough fuel to fly to the Adequate Airport—

  ✈ (i) Assuming a rapid decompression at the most critical point;

  ✈ (ii) Assuming a descent to a safe altitude in compliance with the
  oxygen supply requirements of §121.333; and

  ✈ (iii) Considering expected wind and other weather conditions.

  ✈ (3) The airplane has enough fuel to hold for 15 minutes at 1500 feet
  above field elevation and conduct a normal approach and landing.

  (b) No person may dispatch or release for flight an ETOPS flight
  unless, considering wind and other weather conditions expected, it has
  the fuel otherwise required by this part and enough fuel to satisfy
  each of the following requirements:

  ✈ (1) Fuel to fly to an ETOPS Alternate Airport.

  ✈ (i) Fuel to account for rapid decompression and engine failure. The
  airplane must carry the greater of the following amounts of fuel:

  ✈ (A) Fuel sufficient to fly to an ETOPS Alternate Airport assuming a
  rapid decompression at the most critical point followed by descent to
  a safe altitude in compliance with the oxygen supply requirements of
  §121.333 of this chapter;

  ✈ (B) Fuel sufficient to fly to an ETOPS Alternate Airport (at the
  one-engine-inoperative cruise speed) assuming a rapid decompression
  and a simultaneous engine failure at the most critical point followed
  by descent to a safe altitude in compliance with the oxygen
  requirements of §121.333 of this chapter; or

  ✈ (C) Fuel sufficient to fly to an ETOPS Alternate Airport (at the one
  engine inoperative cruise speed) assuming an engine failure at the
  most critical point followed by descent to the one engine inoperative
  cruise altitude.

  ✈ (ii) Fuel to account for errors in wind forecasting. In calculating
  the amount of fuel required by paragraph (b)(1)(i) of this section,
  the certificate holder must increase the actual forecast wind speed by
  5% (resulting in an increase in headwind or a decrease in tailwind) to
  account for any potential errors in wind forecasting. If a certificate
  holder is not using the actual forecast wind based on a wind model
  accepted by the FAA, the airplane must carry additional fuel equal to
  5% of the fuel required for paragraph (b)(1)(i) of this section, as
  reserve fuel to allow for errors in wind data.

  ✈ (iii) Fuel to account for icing. In calculating the amount of fuel
  required by paragraph (b)(1)(i) of this section (after completing the
  wind calculation in paragraph (b)(1)(ii) of this section), the
  certificate holder must ensure that the airplane carries the greater
  of the following amounts of fuel in anticipation of possible icing
  during the diversion:

  ✈ (A) Fuel that would be burned as a result of airframe icing during 10
  percent of the time icing is forecast (including the fuel used by
  engine and wing anti-ice during this period).

  ✈ (B) Fuel that would be used for engine anti-ice, and if appropriate
  wing anti-ice, for the entire time during which icing is forecast.

  ✈ (iv) Fuel to account for engine deterioration. In calculating the
  amount of fuel required by paragraph (b)(1)(i) of this section (after
  completing the wind calculation in paragraph (b)(1)(ii) of this
  section), the airplane also carries fuel equal to 5% of the fuel
  specified above, to account for deterioration in cruise fuel burn
  performance unless the certificate holder has a program to monitor
  airplane in-service deterioration to cruise fuel burn performance.

  ✈ (2) Fuel to account for holding, approach, and landing. In addition to
  the fuel required by paragraph (b)(1) of this section, the airplane
  must carry fuel sufficient to hold at 1500 feet above field elevation
  for 15 minutes upon reaching an ETOPS Alternate Airport and then
  conduct an instrument approach and land.

  ✈ (3) Fuel to account for APU use. If an APU is a required power source,
  the certificate holder must account for its fuel consumption during
  the appropriate phases of flight.

  §121.647 - Factors for computing fuel required.

  Each person computing fuel required for the purposes of this subpart
  shall consider the following:

  ✈ (a) Wind and other weather conditions forecast.

  ✈ (b) Anticipated traffic delays.

  ✈ (c) One instrument approach and possible missed approach at
  destination.

  ✈ (d) Any other conditions that may delay landing of the aircraft.

  For the purposes of this section, required fuel is in addition to
  unusable fuel.


How do civil aircraft flying in formation handle ATC?

As long as the aircraft are in formation, they are controlled as a single aircraft.
From US DoT OrderJO 7110.65T ATC General Control:

2-1-13. FORMATION FLIGHTS
a. Control formation flights as a single aircraft. When individual control is requested, issue advisory information which will assist the pilots in attaining separation. When pilot reports indicate separation has been established, issue control instructions as required.

The decision to break the flight lies with the pilot in command, and the ATC then controls the aircraft individually.

Separation responsibility between aircraft within the formation during transition to individual control rests with the pilots concerned until standard separation has been attained.

Upon break-up of the formation flight, the controller initiating the break-up shall ensure that all aircraft or flights are assigned their proper equipment suffix.


How is the search-and-rescue system for civil aviation over waters agreed and funded?

Search and Rescue is under the ICAO umbrella, but also with the IMO.

Annex 12 to the Convention on International Civil Aviation gives the international standards and recommended practices (SARPS) on Search and Rescue.
The annex is supplemented by the International Aeronautical and Maritime Search and Rescue (IAMSAR) Manual, which is published by the International Maritime Organisation (IMO)

Together the documents describe:

The organisational structure of the worldwide SAR system concept,
including cooperation between states. (ICAO Annex 12, chapter 2, 3 &
4, IAMSAR volume 1)
The operating procedures for organising and coordinating a SAR
mission (ICAO Annex 12, chapter 5, IAMSAR volume 2)
The operating procedures for those carrying participating in the SAR
mission (Appendix to ICAO Annex 12,  IAMSAR volume 3/ ICAO doc. 9731)

The details of implementing the SARPS are left to the states themselves.


Is reverse thrust needed on a long runway

Reverse thrust is never needed.

A reverse thrust is relatively complex thing that can easily fail and for this reason when deciding whether an aircraft can land at some runway, the calculations are done without assuming reverse thrust. And of course the stopping distance for aborted take-off is also without thrust reverser, because if your engine failed, it won't provide any.

The reason to use reverse thrust is to reduce wear of the brakes and tires. The kinetic energy of the aircraft is huge and when it gets converted to heat in the brakes, they can get pretty hot. So if available, pilots always use reverse thrust to ease the brakes.

But it's not a big deal if not available. Thrust reversers are on MEL (minimum equipment list) for most if not all aircraft meaning the aircraft can be dispatched with thrust reversers inoperative. The brake wear will be higher from the more intensive braking, but it is better than having a plane wait for spare parts at some remote location.

Regarding long runways, there is almost always a possibility to turn off the runway earlier, which often saves time for the aircraft (shorter route to taxi) and makes the runway available for next aircraft sooner. So pilots usually still want to use some reasonable braking.


The short and sweet answer to this question:  That kind of thinking is what kills a lot of pilots.

A non-instrument rated pilot may know how to fly and navigate but does not yet have the skill to do so in total reliance upon instruments.  A PPL does require you to have at least 3 hours of simulated instrument flying with an instructor.  That may keep you alive in straight and level flight if you enter instrument conditions inadvertently, but it's not going to be adequate for conducting an entire flight in IMC.

This quickly becomes clear to new students pursuing an instrument rating who go for their first filed IFR flight in hard IMC with an instructor.  Once you enter a cloud, you go into a world of brilliant white (day) or inky black (night) and there is absolutely no visual references to follow.  You must be able to stay on top of that airplane, manage all of its systems, communicate with ATC, fly departure and approach procedures correctly, and handle emergencies, all without the benefit of visual reference.  In addition instrument flight has a nasty habit of inducing sensory illusions and spatial disorientation due to vestibular sensations causing the pilot to incorrectly judge the aircraft's attitude, etc.  You will be surprised the first time that you fly in real IMC just how STRONG the urge is to trust your vestibular senses over cockpit instruments and you can start doing this unconsciously when you start getting saturated and overloaded with cockpit tasks like terminal environment workload, emergencies, and delays and holding.

A number of pilots - good ones too - are now dead because they did not take this seriously.  One notable high profile case was John F Kennedy Jr., who inadvertently entered instrument conditions during a flight from Essex County Airport in NJ to Vineyard Haven, MA.  Even though the entire flight was in VMC, dark night over water provides no visual references for the pilot.  Kennedy became spatially disoriented; his PA-32 Saratoga entered a tight spiral and crashed into the ocean.

When I was prepping for a solo CC with an instructor for my PPL (the flight was scrubbed due to weather that day) I watched a guy take off in a PA-32 Saratoga and kill himself by flying into inclement weather.  The weather for that day had 600 ft ceilings and poor visibility.  He attempted to scud run under the deck, became spatially disoriented and flew into an antenna park near the Arkansas river.  The plane was sliced in half by a guy wire and crashed.  The pilot was not instrument rated but filed an instrument flight plan, departed KRVS with a clearance, then deviated from the flight plan and attempted a scud run.  His desire to fly his family down to Dallas to see a college football game in bad weather without proper training for it killed himself, his wife, his two teenage daughters and a family friend.

It takes a lot of practice to successfully fly in IMC.  The FAA required instrument ratings for pilots to conduct instrument flight due to the high number of accidents associated with inadvertently entering IMC or worsening weather conditions without competence in instrument flight.  Over 80% of these kinds of accidents result in fatalities.

In addition to requirements to becoming rated for instrument flight, per 14 CFR §61.57, the FAA also has currency requirements to maintain instrument proficiency.  You are required to have executed at least 6 instrument approaches, holds and navigation by electronic nav systems within the preceding 6 calendar months.  This currency work must have been done in either real or simulated instrument conditions.  Once that expires, you do have an additional six calendar months to complete this currency work with safety pilot.  If after 12 calendar months you have not maintained this instrument proficiency, you must undergo an instrument proficiency check with a CFII.

UPDATE - in regards to advanced, modern avionics in the cockpit, back 18 years or so ago when I was a young engineering student and the industry was beginning a transition from traditional structural analysis calculations done by hand to using computer aided finite element analysis programs, a college professor of mine once made a comment that always struck me as very applicable to advanced integrated flight decks.  He said that these new FEA programs had the capability to make a good engineer better and a poor engineer dangerous.  I’ve always viewed modern glass cockpits in the same fashion and accident statistics on this seem to bear it out as well.  Glass cockpits and modern avionics can improve your ability to fly an aircraft, reduce pilot workload and fatigue during critical times but they can get you into a lot of trouble as well.  There have been many cases where pilots have run out of fuel and crashed or had a fatal CFIT simply because they did whatever the screen told them without being able to critically think about what information they were receiving and cross checking it to see if it made sense for a given situation.  Autopilots and autothrottles, too, are useful for relieving the routine grunt work of flying, but can result in emaciated stick and rudder skills, which will be needed in critical moments should an AFCS fail.

An instrument rating is nothing more than a journeyman's license to practice instrument flight.  One should always be aware of this and approach the process of planning an instrument flight accordingly.  All it takes is one harrowing incident to really scare you up and make you aware of you own human limits and mortality.  Set personal minimums for flight conditions and approaches well above published minimums and periodically evaluate these as you continue to build experience.  Never fly an approach into an unfamiliar airport or one surrounded by mountains or other hazardous terrain until you have done so in visual conditions and practiced the approach on a day VFR flight.  Be wary of the differences between flying IMC in day or in nighttime.  Be cautious of instrument flight in busy airspace eg the SoCal Class B areas, etc.  These are just a few of the additional challenges and hazards you need to consider before you venture into darkened skies...


What do the various lights in the overhead aisle light cluster of a Bombardier Q400 NextGen represent?

This is the so called "area call panel" and it is indeed used to signal the cabin crew. The colours and their respective meaning is not regulated and depends on the aircraft and aircraft manufacturer.
A selection of colors, manufacturer and type according to airliners:

Boeing / McDonnell Douglas:

Pink - Flight crew to FA call ORFA to FA call
Blue - Call to FA from passenger in seat
Amber - Call to FA from passenger in lavatory
Red (717 only) - Lavatory smoke detector set off
Green (DC-9 only) - Unused, included as a placeholder for an unknown function.

Airbus:

Red - Flight crew to FA call OR (some aircraft only) FA to FA
call
Blue - Call to FA from passenger in seat
Amber - Call to FA from passenger in lavatory
Flashing Amber - Lavatory smoke detector set off
Green (some aircraft only) - FA to FA call

Further down you can read, that Bombardier Dash 8 uses solid green for a regular call and flashing amber for emergency call.
A definitive answer can only be found in the respective aircraft or crew manual.


From the manual:

So it appears that this instrument's terminology is a little non-standard.

Additional information:

From the Youtube video, you can see that they are moving at a fair pace:

If you take these numbers and plug it into the equations from this question,

$$Ram~Rise=SAT\times0.2\times{M}^2$$

(remembering that SAT needs to be in degrees Kelvin)

You come up with

$$Ram~Rise=(273-33)\times0.2\times{0.491}^2 \approx 11.6C_{rise}$$

Which is pretty close to what you see in the video.

Additional, additional information:

Here is the conversion chart of OAT to SAT in the POH for that (or similar) airplane.

No other qualification is given, but my assumption is that OAT is not TAT, and would be wrong to label it that... it is just the raw temperature sensor value.


Why is the take off speed and distance reduced by head winds?

You're correct that a headwind will reduce the takeoff roll (takeoff distance). As far as takeoff speed, the airspeed will remain same, but the ground speed will be reduced.

In the simplest sense, an aircraft rotates for takeoff when it generates enough lift (leaving aside other considerations). This is dependent on the airspeed as the lift generated is propotional to the square of airspeed (provided the other factors like wing area and lift coeffecient are kept constant) at a density altitude. As a result, it is the airspeed, not the groundspeed that matters.

If you have some headwind, the effective groundspeed is reduced by the same amount- resulting in reduced takeoff distance. The effect of the wind on landing distance is similar to the takeoff distance. You can see this in the following figure.

Image from avstop.com

As it can be seen, the presence of winds can have a significant effect on the takeoff disantances required (note that the airspeed remains the same in all cases). Due to this, the direction of prevailing winds can have a significant effect on determining the runway headings. From Influences on Airport Layout:

  The weather patterns of an area, especially the prevailing winds, are a major factor in determining runway headings. Prevailing winds are defined as the direction from which the winds blow most frequently. Remember that airplanes take off and land into the wind. Let's say that at a given airport the prevailing winds blow in from the west 65% of the year, while 30% of the year the wind blows in from the east, and the remaining 5% coming from the northwest. It would be best then to orient the runway W (27) and E (9). That would mean that approximately 95% of the year airplanes would be landing and taking off into the wind.


On an IFR Low Altitude Chart what does this symbol mean?

① - ICAO ID

As indicated, will be used for OCONUS airports only (overseas), e.g. Guam has a 4-letter ICAO designator:

② - Symbol with circle: Lighting

  An "L" following the elevation under the airport name means that
  runway lights are on during hours of darkness. A circle around the "L"
  indicates there is Pilot Controlled Lighting. A star beside the "L"
  means the lighting is less than continuous.

(Source)

This is part of the legend, but there is no lead line.

③ - ATIS available part-time

This is not the tower frequency (as your question seems to assume), but the ATIS frequency.

This information is not redundant, the ATIS may be available full time for an airfield open part-time. This is the case for Grand Junction Regional in the snapshot above.


Is special permission required to take off from a field within restricted airspace?

The most obvious point to make here is that KMRH is not in restricted airspace: the sectional shows that it's in uncontrolled class G airspace, with class E at 700' AGL. But having said that, there is indeed a lot of special use airspace nearby:

W-122 is a warning area
R5306A and R-5306D are restricted areas
A-530 is an alert area

You can't enter the restricted areas without permission from the controlling authority, but you can enter the warning and alert areas if you want. More details of each area are on the sectional chart, the FAA's SUA site and JO 7400.8X.

Looking at the sectional, it looks to me like A-530 is a 'gap' in the restricted areas to give access to KMRH and the three private airfields nearby. R-5306 A and D are from the ground to 18,000 MSL (up to but not including FL180, to be precise) and operate continuously. If the A-530 airspace were the same then there would be no way in or out of KMRH (over land, at least) without getting permission every time. Because A-530 is sandwiched between two restricted areas, I guess there's probably a lot of military traffic around and that's why it's an alert area rather than normal class E airspace.


Blending is the process of filing and polishing damaged sections off of the turbine blade. This prevents further damage and extends the life of the engine without having to replace parts, making it a very economical solution. There is a limit however, as modifying the turbine blades leads to a small cost in efficiency that can build up over time.


In what conditions are visible Wingtip vortices created?

You're definitely right about humidity, but from experience I'd say a colder environment works better than a warmer one. Case in point: unstable/rainy autumn weather (as common in Northern Europe) shows (tip) vortices very well, whereas I haven't seen them so much in hotter places (Southern USA, Caribbean). Having ensured visiblity, a larger pressure difference between lower and upper side of the wing (caused by higher speed and higher lift force) increases the tip vortices in size/strength. This explains the fact that (wake vortex) separation minima are largely dependent on aircraft mass (which scales with lift).

Additional (or stronger) vortices can be created artificially using vortex generators. As turbulent flow separates less easily than laminar flow, these are used (on wing leading edges, engine cowlings, tailplanes) to trigger turbulent flow and thereby prevent/postpone separation. This is especially important if there are control surfaces (such as ailerons or a rudder) downstream, which lose their effectiveness in separated flow. In theory, you could use this same principle to increase vortex visibility.

Whether this also works in theory of course depends on safety standards and regulations concerning modification and the size of the vortex generator required. Examples from the world of sports aerodynamics, where surface roughness or 'transition strips' are integrated in suits worn by speed skaters or cyclists. As you can see on the images in the linked article, these are fairly small.


How does the airflow around winglets reduce drag?

This video perfectly explains what happens, except it doesn't use winglets, but different shape of the wings, but the idea is the same:

https://www.youtube.com/watch?v=CnvIf3vFEYA

What the video describes is when wings don't have winglets, air flowing under the tip of the wing escapes to the side of the wing and upwards, creating a vortex which reduces lift. Addition of winglet reduces the vortex and thus increases lift.

In the video however, new type of wing is shows that doesn't require winglets all together.


The stick-free static margin depends a lot on the elevator hinge moment coefficients of the aircraft. Depending on the sign of the hinge moment derivative with angle of attack ($c_{r_\alpha}$), the stick-free stability can be greater than the stick-fixed stability (greater for positive $c_{r_\alpha}$ because then the control surface will deflect into the changed airstream). By how much depends also on the derivative over deflection angle $c_{r_\eta}$, but this one should definitely stay in the negative range, or the stick will be hard to center.

The stick-fixed margin is much easier to calculate. If aspect ratio is reasonably high, the surface-weighted mean of the quarter points of all horizontal surfaces will give a good approximation of the neutral point $x_N$, and the center of gravity depends on the loading of the aircraft. Normally, you would calculate the margin for both the most forward and the most backward cg location $x_S$ for which the aircraft is certified.

With the given planform, the mean aerodynamic chord $l_\mu$ is also easy to calculate, and the stick-fixed margin is (x backwards positive): $$\frac{c_{M\alpha}}{c_{L\alpha}} = \frac{(x_S - x_N)}{l_\mu}$$


Could I receive flight training in my company's jet, while on company business with passengers?

It is an interesting question and needs quite a few FAR's to figure out. Let's start with having other people on board:

If the aircraft is not certified for single-pilot operations, then you cannot based on FAR 61.89(b)

  (b) A student pilot may not act as a required pilot flight crewmember on any aircraft for which more than one pilot is required by the type certificate of the aircraft or regulations under which the flight is conducted, except when receiving flight training from an authorized instructor on board an airship, and no person other than a required flight crewmember is carried on the aircraft.

If it is certified for single-pilot operations, you may be able to receive training as long as you are not PIC and you are not sitting in the left seat (as almost all single-pilot jets that are certified single-pilot usually have a restriction to left seat only).

However the real rub comes in when you consider that you are a private pilot, not a commercial pilot, and the FAA's extremely broad definition of "compensation". On more than one occasion, the FAA has held (and won in court) that getting flight time in furtherance of a certificate is compensation. Technically just receiving your normal compensation (hourly wages) is enough to meet the definition of being compensated for flying.

The only way to get a real good answer to this, because it is a very broad subject and open to legal interpretation, is to engage your local FSDO.

I'm guessing though that the ultimate answer will be no. Aside from the issues with the FAA and FAR's depending on what operations your employer is conducting under (121, 135, 91, etc), your employer will also have to consider aircraft insurance. Many corporate jets are insured only for certain pilots or pilots who meet minimum qualifications and the insurance policy may completely bar primary training of any kind in the aircraft.

So talk to your FSDO, if you get an OK from them, the next step is to talk to the corporate attorney or an aviation lawyer and have them review the insurance documentation to see if you are allowed to sit in one of the seats and manipulate the controls.


Can a pilot initiate an enroute descent to an IAF without ATC 's approval?

You are never allowed to simply vacate an assigned IFR altitude without clearance.  When you were cleared to the IAF your clearance should have included "pilot's discretion down to ..." of "cross IAF at or above..." or similar words.  If you don't get this, just ask.  Never presume that you can just start down on your own though.


Is there currently a measurable shortage of pilots?

Here in the US (because this varies around the world) some sources do say there is a pilot shortage. There are many reasons that have been cited for the decrease in pilots here in the states. But the main points seem to be,

Rising Costs of training
FAA upping the required hours (250 -1500) for a full ATP ticket
Lower conversion from military pilots (there was a time when many of the commercial pilots out there were former service pilots)
Lower Salary Prospects: its no mystery that pilots don't make what they once did nor get the perks they once did.

Another factor that effects this once you are in the industry is the fact that "seniority" does not transfer over from airline to airline. Generally this is not an issue if you work for someone like American or Delta who have plenty of jobs and steady routes. But if you are captain at NotSoWellEstablishedAir and they go belly up you will most likely join one of the others lower in the ranks if not at the bottom.

Another thing that is worth mentioning is that it may be more advantageous for a pilot to remain a very senior first officer instead of becoming a very junior captain. You may have more power over your route choice, time off, and general schedule as a senior first officer than as a newly minted captain. For some pilots, like those who may be trying to start a family this may be seen as an advantage.

As for the shortage over seas (outside the US) that stems from different issues. First and foremost many countries have seen great and more importantly fast economic prosperity which has allowed them to get into the aviation game. A game traditionally filled with high costs and heavy regulations. As such many newly wealthy nations have been able to enter the aviation world much faster than their regulations and training programs can keep up with. The FAA is almost 60 years old with aviation regulations dating back to the 30's with the CAA. There are even some american issued pilots licensed signed by the Wrights them selves from the very early days. Other countries simply don't have the history of growing with aviation like the US and similar countries have had. Thus they have all these new planes but no one to fly them and no well established programs and regulations to create the pilots. In turn they are forced to import trained, certified pilots from elsewhere.


Application interview / career as a pilot: is qualifying from First Officer to Captain expected from an applicant?

I would say that an airline will avoid hiring an applicant that is not assessed as eventual "captain material".  It's not the maximum return on the airline's investment.
An applicant would never say in an interview that they only wanted to be a lifelong FO, except under special circumstances like an older hire who is likely to retire before meeting the experience requirements, or someone who has limiting medical conditions at hire (like the Type 1 diabetics who are now flying in some countries) that prevent them from qualifying for PIC.
An FO has to apply to upgrade to captain, so theoretically, someone can continue as an FO indefinitely (in a union operation at least), up to a point, but I think it would be career suicide to say so up front during the interviews.
It does happen though.  An acquaintance of mine some years back was still copilot at a major airline, flying heavies, with somewhere around 25 years in.  He finally upgraded to captain for the last years of his career.  One of his motivations was he'd gotten to the point of being at the top of the seniority ladder for copilots.
He was making way less than he would as captain, but he didn't care about the money so much, and was more interested in the bidding benefits of being top of the heap in his "junior" heap in bidding for pairings, insofar as he got the best routes and the best schedules and the most time off.  Upgrading to capt would mean he had to drop to smaller aircraft and a lower rung on the seniority ladder(back to working over Christmas, etc), and temporarily less money .  He finally upgraded to capt more or less in response to management and peer pressure in his later years (he said at the time).
There are a number of websites that post interview Gouges ("gouge" is a slang word for intel reports on an airline's recruiting/interview practices) like here. These can give a good sense of the kind characteristics they are looking for, and you will never find one that advises people to state that they don't want to progress to captain.


Does Clearance Delivery operate in the same way for airports in Bravo, Charlie and Delta airspace?

All will be pretty similar.  In Bravo, and Charlie and Delta if they are close to the Bravo, you will typically contact Clearance for your departure directions (heading to fly, altitude to climb to or hold at after takeoff (or cleared to climb to 1, and expect clearance to higher after so many minutes, or when reaching some intersection), and Approach frequency to expect) before Ground gives you clearance to taxi from parking towards the active runway and for your runup.  If you filed a Flight Plan, expect to have the clearance (perhaps modified) read to you, which you must read back.
After switching to Gnd for Taxi directions, be ready to read those back as well. Have the Airport Diagram out, and don't be afraid to ask for Progressive Directins.  Things can be busy at a Bravo. When your runup is done, you switch to Tower if Gnd hadn't handed you over already, let them know where you are and that you're ready for takeoff.

If the Charlie and Delta are not near the Bravo, things may be a little more relaxed. You may get your Clearance from the Tower, or Gnd, and Gnd/Tower may be the same guy on the same frequency, or he may be on 2 or more frequencies, switching between Gnd and 1 or more Tower frequencies for different air sectors.  You may stay on the Tower frequency longer before being switched to Approach, or for Delta you may just be asked to advise when you are clear of the Delta airspace.

Don't fly to any Bravos until you are comfortable on the radio.  Limit flights to Delta and Charlie to start until you can follow the lingo.


Why aren't larger airliners such as the A380 more efficient than smaller ones?

The comparison is seriously flawed.
While over the entire duration of the flight the larger aircraft is more efficient per passenger/mile, this is not the case for the flight phases that cause the bulk of the fuel consumption for smaller airliners but only a fraction for larger airliners: takeoff/climb and descent/landing.

A 747 or A380 flying a one hour leg, which is typical for many smaller airliners, would use more fuel per passenger over that leg than does say a 737 or A320, despite being more fuel efficient at cruise altitude (if it can even reach its optimal cruise altitude over that distance).

It is also far less flexible, and requires a higher passenger density than does the smaller airliner, a passenger density that's simply not there on most routes unless you greatly reduce the frequency of flights (in which case you'd best hope all your competitors do the same as passengers are less likely to be happy to wait for your one flight a day at noon when they can get to their destination at 8AM taking another airline's flight).


Headset for both plane and heli: buy for plane, use adapter for heli, or vice versa?

There's no issues with the adapter either way, as long as it's good quality. The helicopter versions are coiled for a good reason: to keep it out of your way, so I would buy the helicopter version. In most fixed wing airplanes the coil will be absolutely fine, if there's not enough reach you can get extenders pretty easily.


How often are aircraft flown by two FO's?

I'd say this is quite common on flights that require at least 3 pilots due to length.  The third pilot is almost assuredly going to be qualified as a first officer and this is the common staffing strategy with the US carriers that I am familiar with.

Three pilots (by US flag rules) are going to be required for 8-12 hour flights and you'll find that US carriers often will staff a third pilot even on the shorter US east coast <-> western Europe flights.  But what must the three pilot composition be?  Lets examine 14 CFR 121.543 the requirement to relieve a PIC (excepted):

  §121.543   Flight crewmembers at controls.
  (a) Except as provided in paragraph (b) of this section, each required flight crewmember on flight deck duty must remain at the assigned duty station with seat belt fastened while the aircraft is taking off or landing, and while it is en route.

  (b) A required flight crewmember may leave the assigned duty station—

  (3) If the crewmember is taking a rest period, and relief is provided—

  (i) In the case of the assigned pilot in command during the en route cruise portion of the flight, by a pilot who holds an airline transport pilot certificate not subject to the limitations in §61.167 of this chapter and an appropriate type rating, is currently qualified as pilot in command or second in command, and is qualified as pilot in command of that aircraft during the en route cruise portion of the flight. A second in command qualified to act as a pilot in command en route need not have completed the following pilot in command requirements: The 6-month recurrent flight training required by §121.433(c)(1)(iii); the operating experience required by §121.434; the takeoffs and landings required by §121.439; the line check required by §121.440; and the 6-month proficiency check or simulator training required by §121.441(a)(1);

The limitations of 61.167 mentioned above mean those under the age of 23 are not eligible to relieve the PIC. What does it mean to be "qualified as pilot in command of that aircraft during the en route cruise portion of the flight?"  The closest I can find to answer that is in 121.436 which says to be act as a PIC you must have an ATP and be at least 23 years old, have a type rating and have at least 1000 hours combined from part 121 SIC, part 91.1053(a)(2)(i) PIC, part 135.243(a)(1) PIC time.

What this means practically, is that a second in command who

holds an ATP,
is at least 23 years old,
is type rated in the airplane,
is qualified as a second in command, and
has at least 1000 hours SIC time with any airline

may relieve a PIC during en-route flight.

This is further reinforced by the remainder of the quoted portion of 121.543 that says an SIC qualified as PIC need not have any of the required checks a PIC must have (line check, 6 month sim check, etc).

At a major airline it is likely that SIC have ATPs and are type rated during initial training and most major new-hires will be older than 23.  It is also likely they have prior airline experience to give them 1000 hours SIC.  Even if they don't have that experience, they'll have it in a 18 months or less after being hired.

This means that pretty much any FO at the airline and surely any FO who has been there for a year or two is going to be qualified to relieve a PIC.  Because an FO can relieve the PIC and can also relieve an SIC, the third pilot need only be an FO.  This means our crew of three will be one captain and two first officers.

Given the economics involved and the behavior of US airlines when it comes to costs, they will staff an FO wherever they can versus staffing a captain.

To bring this full circle, back to our 8-12 hour flights to/from the US by US carriers that require 3 pilots they will almost always be flown by two first officers during the en-route portion of the flight.

I'm not familiar with non-US regs, so this might not apply.  Given that air carrier rules by the FAA are compatible with ICAO though, I'd guess that this is the common case in other jurisdictions as well.


Could a knowledgeable passenger have saved Helios Flight 522?

It's never bad to inform a crew member about anything you think may be abnormal.

In this special situation, as you know that the oxygen masks deploy automatically if the cabin altitude raises to high, you expect the aircraft to descend in order to allow the pax to breathe normally again. If this doesn't happen it would be possible that the crew deployed the masks manually for no reason or the automatism faulty detected a low cabin pressure. In both cases I would expect an announcement that the oxygen masks are not needed and can be put down safely.

If neither of those options happens something is definitely wrong. Either the pilots already suffered hypoxia or they didn't notice the passenger masks drop at all.
In my opinion the cabin crew should be trained to know what's normal procedure if masks drop, but I would definitely tell a flight attendant about my concerns if nothing happens after two minutes or so.

You always have to remember: In high altitudes you become unconscious after less than 30 secs without the mask, and as the masks can only produce a limited amount of oxygen it's a really time critical issue to reach the flight-deck and initiate a descend if the pilots are already out of service!