What are the historical precedents of today's E2 and E4 airspace? (US)

What we now know as Class D and E2 airspaces were once (before 1992) a single type of airspace called a "Control Zone".  "Control Zones" first appeared on charts in the mid-1940's and consisted of a thin dashed circle enclosing an airport-- originally red, later blue. By the time of this 1974 test-prep publication, "Control Zones" had been defined to go up to the overlying "Continental Control Area" at 14,500' MSL.

Originally a "Control Zone" did not indicate a communications requirement for VFR traffic-- many non-towered airports had a Control Zone around them, and a few towered airports lacked them.  Instead, all towered airports were automatically assumed to have an "Airport Traffic Area" around them, 5 miles in radius and 3000' tall, that could not be entered without first establishing radio communications with the tower.  The purpose of a "Control Zone" was simply to impose-- all the way to the surface-- higher VFR cloud clearance and visibility requirements than would exist in "uncontrolled" airspace, for the protection of IFR traffic emerging from clouds.

Around September 1992, changes were made to the markings on the sectional charts in preparation for the upcoming September 1993 "alphabet" airspace reorganization, when the "Airport Traffic Areas" would disappear and the boundary of the communication requirement would be shifted to the edge of Class D airspace.  All "Control Zones" that did not contain a control tower had their depiction changed from a dashed blue line to a dashed magenta line, and were identified on the chart legend as a "Control Zone without communications requirement".  This was the immediate forerunner of today's E2 airspace.  At the same time, to eliminate the future communication burden on VFR traffic (and towers) that would be created in cases where Class D airspace had a projection extending far from a towered airport, some of the projecting portions of Control Zones at towered airports had their borders changed from dashed blue to dashed magenta and were identified on the chart legend as "Control Zone extensions".  These "Control Zone extensions" are the immediate forerunners of today's E4 airspace.  The complete legend on the charts for the new dashed magenta line was "Control Zone at airport without control tower and Control Zone extension without communications requirement".

It is interesting to compare aeronautical sectional charts dating from shortly before the introduction of the dashed magenta markings, to charts effective immediately after the introduction of the dashed magenta markings.  It is interesting to see how the Control Zones at airports with towers changed from their previous shapes. Some were made smaller. On some, any rectangular projections remained part of the blue dashed shape surrounding the airport, while on others, some or all rectangular projections were changed to magenta dashed lines that abutted against the blue dashed shape. The determining factor does NOT appear to simply be how far the projections projected away from the basic inner circular shape.  Clearly, planners were preparing for the communications requirement that would soon be shifted from the old "Airport Traffic Area" boundaries, to the edge of the Class D (or higher) airspace.

Note however that according to the FAR's, the "Airport Traffic Areas" still served as the boundaries of the communications requirement until the September 1993 "alphabet" airspace re-designation.

Therefore it's not clear to me whether or not the distinction between a "Control Zone" and a "Control Zone extension" had any actual practical or regulatory significance in the September 1992 to September 1993 time period.  Could it have simply been a charting convenience to help pilots, chartmakers, and others prepare for the regulatory changes that would go into effect in September 1993?

Certainly FARs 91.155c, 91.157a, 91.303c, 101.33a, and 103.17 continued to simply refer to "Control Zones" with no mention of "extensions" all the way up until the September 1993 airspace re-designation.  Would these FAR's have applied to airspace that was charted as a "Control Zone extension", or only to airspace that was charted as a "Control Zone"?

Diving a little deeper into this question of the significance of the distinction between a "Control Zone" and a "Control Zone extension" prior to September 1993: in the version of the FARs effective Jan 1993, we read "71.1 Applicability The complete listing for all jet airways, area high routes, Federal airways, control areas, control area extensions, area low routes, control zones, transition areas, terminal control areas, airport radar service areas, postive control areas, reporting points, and other controlled airspace can be found in FAA Order 7400.7A, Compilation of Regulations, dated November 2 1992."  Note the lack of the phrase "control zone extension" in this sentence.  Would a careful reading of the November 2, 1992 edition of FAA Order 7400.7A show that the airspace that appeared on the charts as a "Control Zone extension" was still simply considered part of a "Control Zone" from a regulatory standpoint?  Does the phrase "Control Zone extension" appear in this edition of FAA Order 7400.7A at all, or was that airspace simply treated as a completely integral part of the adjoined  "Control Zone"?  So that the distinction between "Control Zone" and "Control Zone extension" essentially existed on the aeronautical charts only, and nowhere in the actual regulatory documents?  I haven't yet been able to obtain a copy of the November 2, 1992 edition of FAA Order 7400.7A, and don't know the answer to these questions.

The actual transition from the "Control Zone"/ "Control Zone extension" terminology to the modern "alphabet" terminology happened in September 1993.  At this time "Airport Traffic Areas" ceased to exist, and all the airspace surrounded by a dashed blue line on the sectional became Class D airspace, and all the airspace surrounded by a dashed magenta line on the sectional became Class E airspace that extended all the way to the surface.  This is when the awkward terminology that we currently find used to describe E2 and E3/E4 airspace in the "Airspace Designations and Reporting Points" document was first applied to what had previously been depicted on the charts as "Control Zones" (around non-towered airports), and what had previously been depicted on the charts as "Control Zone extensions", respectively.  Considering that E4 airspace also goes all the way down to the surface, it's unfortunate that someone didn't come up with a better term than "Designated as Surface Areas" or "Designated as a Surface Area for an airport" to describe the E2 airspace.  September 1993 is also when the language of FARs 91.155c, 91.157a, 91.303c, 101.33a, and 103.17 was changed to its current awkward form.  Regardless of whether or not these FARs had been considered to apply to the airspace of the "Control Zone extensions" during the year or so that they were labelled in that manner on the charts, the language adopted for those FARs in September 1993 clearly matched the E2 airspace description in the "Airspace Designations and Reporting Points" document effective at the time (as well as at the present), and did not match the E3/E4 airspace description.

Addendum--

As a point of related interest, here is a list of activities that require prior authorization (or in the case of aerobatic flight, are prohibited) in E2 airspace but not E3/E4 airspace, along with the relevant FAR or other legislation:

Operating VFR without a SVFR clearance in certain adverse weather conditions -- FAR 91.155c

Ultralight flight-- FAR 103.17

Aerobatic flight-- FAR 91.303c

Operation of an unmanned free balloon below 2000' AGL-- FAR 101.33a

Operation of a small Unmanned Aerial Vehicle (e.g. commercial drone) -- FAR 107.41

Operation of a recreational small Unmanned Aerial Vehicle (e.g. typical hobbyist drone or model airplane) under the "Recreational Exemption" -- language passed by Congress in October 2018

Also, FAR 91.157a allows ATC to grant a SVFR clearance in E2 but not E3/E4

As noted in the links below, the distinction between E2 and E3/E4 airspace is not always observed by ATC in actual practice in relation to the requirement for, and the possibility of granting, a SVFR clearance.

Sources--

Source for FARs as they existed in January 1 1993, also listing the modifications that would become effective September 16 1993

Source for dimensions of "Airport Traffic Area"

Related content on ASE--

What are E2 and E4 airspace?

What are E2 and E4 airspace?

What are E2 and E4 airspace?

Which parts of class E airspace can an ultralight (part 103) fly in without prior ATC authorization?

Does an SVFR clearance extend to Echo surface extensions?

Does an SVFR clearance extend to Echo surface extensions?

Does FAR 91.155c apply to class E surface extensions?

In actual practice, do ARTC Center personnel generally follow the rule that a SVFR clearance may be granted in E2 airspace but not E4 airspace? (US)
In the US, is there much variation among the various ARTC Centers as to where a SVFR clearance may be granted?

How does the distinction between E2 and E3/E4 airspace affect pilots?


What is the FAA definition of "takeoff" and "landing"?

According to the FAA FAA Airplane Flying Handbook, there are three components that make a takeoff:

  Takeoff roll (ground roll) is the portion of the takeoff
  procedure during which the airplane is accelerated
  from a standstill to an airspeed that provides sufficient
  lift for it to become airborne.
  Lift-off is when the wings are lifting the weight of the
  airplane off the surface. In most airplanes, this is the
  result of the pilot rotating the nose up to increase the
  angle of attack (AOA).
  The initial climb begins when the airplane leaves the
  surface and a climb pitch attitude has been established.
  Normally, it is considered complete when the airplane
  has reached a safe maneuvering altitude or an en route
  climb has been established.

So to have a take-off you must have these three components.  That would include a touch and go as well takeoffs from a full stop.

As far as an official definition of landings I didn't see anything official in the FAA documentation but I would say that the airplane touching the ground would count as a landing.


How does the power distribution change for a turbofan engine from being stationary to going at full speed?

Your definitions are correct and your derivations correctly use the law of conservation of energy, so yes, the power distribution change does happen.

The more important question is what does this actually mean. Energy is a rather curious quantity in that while it is conserved in each reference frame (including non-inertial as long as appropriate potential is included), the values of kinetic and potential energy will be different in each!

You can look at all the cases in the reference frame of the aircraft and then the propulsive power will always be zero, because the velocity is—by definition of the reference frame—zero. But the very same situation viewed from the reference frame of the Earth it will be as you describe, and from the reference frame of the air mass it will be similar, but the values will differ slightly as the reference frame move relative to each other at the speed of the wind.

Note that enthalpy does not vary in coordinate transformation, so the sum of the power towards moving the aircraft and towards accelerating the air stream is will be the same in all the reference frames. Most easily calculated in the reference frame of the aircraft from difference in kinetic energy between the intake and the exhaust. This is the output power of the engine itself, and comparing this with the heating value of the fuel will give you the thermodynamic efficiency. Thermodynamic efficiency of turbine engines increases with flight speed due to pressure recovery, i.e. the ram air pressure increasing the effective compression ratio.

Also note that this variance in propulsive power is there for all kinds of propulsion systems, including propellers and wheels of ground vehicles. The propulsive power is always zero at standstill, and how quickly it increases depends on the reactive mass they have available. The more reactive mass, the larger the propulsive efficiency (= propulsive power to output power) will be, and the faster it will increase with velocity. Propellers have some more reaction mass available due to larger diameter, and wheels have whole Earth available, but their thrust is still limited by the surface friction and the maximum torque of the engine (and the friction of the clutch for engines that don't produce torque at zero RPM).


Where does the term 'greased landing' come from?

I've always heard this referred to as a "greased landing" or a "greaser", but never a "greaser landing".

My understanding is that it is referring to a landing that was so good that somebody must have greased the entire runway so that you didn't even feel the airplane touch down.  If you've ever tried to pick something up that has been well greased, then you know what they are referring to.  It's very slippery and slides right out of your hands no matter how hard you try.


Is if safe/legal for an aircraft to return to cruising altitude after passenger oxygen masks have been deployed?

Once the masks have deployed and any of them have been activated, you no longer have an emergency oxygen supply for all the passengers. Not having that, going above FL250 (may vary in jurisdictions besides the FAA) is not allowed. Up to 250, emergency O2 isn't required for the passengers, since you could descend quickly enough to a safe altitude in the event of a depressurization. Above that, though, having the masks available (and no, hanging down doesn't quite count) is required, both for legality and for safety.

To climb back up to a cruise altitude in the 30's is a pretty significant misjudgement, given the facts as they've been presented to date (which may have significant mistakes in the reporting). Up there with depressurizing the aircraft when you meant to turn off the Recirc fan. Or vaping in the cockpit. Or allowing vaping in the cockpit. Or not turning the packs back on immediately when your FO has incorrectly turned them off.

Sometimes you just have a bad day. And then there are some people who need to switch career paths, because they aren't cut out for the one they're in. We all have our own opinions about what the case is here...


Why is Landing Altitude displayed in amber on B777?

The Boeing 777 is a very automated aircraft.  The takeoff altitude, landing altitude, and cabin pressurization altitude are all automatically set when you enter the departure airport and destination airport in the Flight Management Computer.

The EICAS message ALT LDG appears when the FMC is not controlling the landing altitude. This can be caused by one of three different conditions:

1) There is no destination airport entered in the FMC

2) The FMC landing altitude function has failed

3) The LDG ALT knob has been used to set the landing altitude manually

It is also normal to see ALT LDG after landing when the route has been dumped.


What is this abandoned aircraft in Thailand?

Curtiss C-46 Commando
First flight was 26 March 1940. 3,181 were built. The one you have was stored at Don Muang, and ended up in Chonburi, Thailand.
Identifying features are the nose light, the now faded blue/gray cheatline that turns upward behind the cockpit windows, the black antenna under the cockpit, and the white paint under the nose that is gone from the belly:
(airliners.net)
Matching engine:
(wikimedia.org)
Matching front view:
(wikimedia.org)


Why does instability in pitch lower trim drag for an aircraft with a tail?

It might be helpful to look at this article from Boldmethod.

The basic idea is that the farther away the center of gravity is from the center of pressure (or center of lift depending on your terminology) the more lift the horizontal stabilizer will have to generate.  The more lift an airfoil has to generate will result in more induced drag.  Trim drag is specifically the induced drag created by the horizontal stabilizer.  The horizontally stabilizer can actually produce both positive (upward) and negative (downward) lift but the negative lift has the even worse affect of requiring the wings to create more lift to compensate for the downward lift as demonstrated in the Boldmethod article.

Having the center of gravity at the center of pressure also allows the aircraft to be more maneuverable since less force is required from the horizontal stabilizer to initiate a maneuver.  This is why fighter jets tend to be longitudinally unstable and use fly-by-wire to compensate for it.


Did Hamilton Sundstrand Corporation fix this GPWS problem?

EGPWS/TAWS is the fix for this problem...

The original Ground Proximity Warning Systems were indeed quite limited due to their inability to know anything about anything besides what was under the plane at the time.  While one could theoretically use ground-mapping radar techniques similar to military terrain following radar for this, that would be dancing in a minefield of classification and relatively advanced signal processing, making it impractical for use in the civil aviation environment.

Instead, EGPWS (enhanced ground proximity warning system)/TAWS uses the aircraft's idea of its own position (from the onboard navigation systems) along with a database of terrain info to generate forward looking warnings in addition to the more straightforward radio-altimeter warnings generated by GPWS.  This is what is found on basically all aircraft in mainline airline service these days, as well as many more modern business jets and commuter-type aircraft as well.

but even TAWS won't save you if you're getting lied to about where you are!

Nonetheless, it's still possible to have a non-pilot-error CFIT in an EGPWS/TAWS equipped aircraft -- on one fateful day in Ethiopia, a British Mediterranean Airlines A320 nearly became a crater twice over thanks to the ADS VOR/DME providing bad bearing information to anyone who tried to use it as a navaid -- without GPS, the only thing the TAWS had to go on was the VOR-updated IRU position, which was being thrown off by the bad data from the ADS VOR.  Luckily for the passengers, the crew had their wits about them and caught the situation before smashing into the ground, but even with GPS being nearly universal in airliners compared to its prevalence in 2003, interference, spoofing, or jamming of GPS signals is still a threat, as this year's Red Flag exercises are reminding us quite vividly by taking out GPS service across much of the western CONUS.


What if the engines fail? In early airships this happened frequently, and many ships limped home on a reduced number of engines.

Note that all airships were both vertically and laterally unstable. The helmsman had to continuously adjust the rudder angle to keep the ship on course. In NACA TN 204, Frank Rizzo concluded that enlarging the fins would be beneficial, and reducing them would be unwise. They were just as large as needed to control the ship, but not sufficiently large to give it static stability.

Static stability in aircraft means any attitude change creates forces which return the craft to its old attitude. In airships, several types of static stability must be observed:

Buoyancy: If the ship rises or sinks, the rate of cooling of the atmosphere and the gas in the hull might differ. If the cooling rate of the atmosphere (lapse rate) is above the adiabatic rate, the ship is unstable.
Pitch attitude: If the ship pitches up or down, the lifting gas will shift towards the highest point, and the heavier gas in the ballonets will shift to the lower point, creating an unstable pitch condition.
Directional stability: When moving forward, any heading change will cause a side force which is centered at the forward hull and pushes the ship further off course. The fins create a counteracting force, but due to their size this force is too small to turn the ship back. Only by adding rudder the helmsman can keep the ship stable.
Longitudinal stability: In a similar way, pitching the ship up or down while in motion will create a destabilizing force on the forward hull which is mitigated, but not eliminated, by the horizontal fins. Elevator deflection is necessary to keep the ship at the desired pitch angle.
Roll stability: Since the center of gravity is below the center of buoyancy, the mass of the gondola will pull an airship right side up. This is also valid when flying turns: Then the gondola will roll the ship into the turn such that a rudder command into the turn will also cause a nose-down pitching moment. Now all control surfaces need to be coordinated to keep the nose of the airship up.

Note that only the first and last type of static stability are ensured, and the first only for special atmospheric conditions! The other three are lacking!

Zeppelin airships used two helmsmen, one for directional and one for pitch control. Due to the size of the ships any movement was very slow, so the task of keeping them on course was easier than it might sound. However, taking any of the fins away or even reducing their size would had made the ships uncontrollable.


You should have an alternate planned that is forecast VFR, with appropriate fuel reserves in place, before you left.  But if you didn't, you'd call an ATC unit and tell them your predicament.  Maybe they can send you to VFR conditions either reported by PIREP or by calling around to other tower units in range.

Otherwise, you're going to have to do an instrument let down.  If you're in contact with an ATC unit, let them provide you with a location to do let down that gives obstacle clearance, and hope your instrument skills are up to the task. In Canada VFROTT is not allowed unless you've had at least the commercial pilot level of instrument training (there is a special rating if you don't). Up here it would be considered crazy for a VFR pilot with no instrument training to do VFROTT in the first place, even if it was legal.

Say you didn't have contact with ATC for some reason.  Well than I'd locate a decent size body of water with my moving map GPS and let down over that, and stop descending if I see water.

That's another planning factor.  You want the cloud you are going to be flying over to have a decent VFR ceiling under it, so you only have to let down through a layer into nice VFR below.


In short: the 24 bit address is critical on the technical layer of Air Traffic Control, but it is not used in the operational level. For identification of aircraft and association to flight plans, the air traffic controllers and the flight data processing systems rely mostly on the Mode A code and the aircraft ID (call sign) transmitted by the transponder.

The ICAO 24-bit aircraft address is an essential element of the way Mode S radar and TCAS work.

Before Mode-S radar, only modes A and C were used by civil ATC secondary radars.

Mode A and Mode C are unaddressed; every transponder receiving a Mode A or Mode C interrogation will reply*. This causes two problems, garbling and FRUIT.

Garbling is caused by the overlap of replies from multiple transponders. A transponder replies on 1090 MHz in the from of a number of pulses. For Mode A & C, there are at most 12 pulses between a set of framing pulses. When multiple aircraft reply to the same interrogation, these pulses mix up and it becomes difficult to find out which transponder sent which pulse. This leads to false altitudes or false squawk codes.

FRUIT (False Replies Unsynchronised to Interrogator Transmission) is caused by replies that are triggered by other radars. When multiple radars operate in an area, transponders can be quite busy and the radar is easily mislead by a reply to another radar. In addition to the timing (range) being wrong, the reply can be Mode A (squawk code) while the radar interrogated Mode C (altitude). There is no way to see what kind (A or C) reply was sent.

To overcome these problems of Mode A/C, Mode S was introduced. Mode S is quite different from Mode A/C and requires a more sophisticated radar and transponder. It uses the 24 bit address to distinguish responses from various aircraft and to interrogate specific aircraft.

Most Mode S interrogations are addressed; the interrogation contains the unique 24 bit address of the aircraft it is interrogating. This reduces the probability of garbling since other aircraft will not reply
Unaddressed Mode S interrogations will solicit replies that contain the address of interrogator (radar). This prevents FRUIT since the radar can verify that the reply is correctly addressed.
Unlike Mode A/C which does not have any error checking, a Mode S reply contains a 24 bit CRC check code.
Mode S Altitude and identity (squawk) replies have their own identifier so they can be distinguished.
Mode S radars can be operated in clusters and coordinate between them who is interrogating which aircraft at which time. This further reduces the message load and garbling / fruit probability.

For TCAS, the Mode S address is used to distinguish replies for various aircraft in the vicinity of the own aircraft. The TCAS transponder interrogates omnidirectionally (in all directions) and get's replies from all direction. Again, this is very susceptible to Garbling and FRUIT. Whilst TCAS can work with Mode A/C, for its reliability and coordination of resolution advisories, the 24-bit address is crucial.


What's the maximum bank angle of a glider?

The bank angle ($\phi$) in a stationary turn is limited by the maximal load factor of the aircraft (or the pilot- whichever is less):
$$\phi_{max}=\arccos(\frac{1}{n_{max}})$$

Utility category gliders ($n_{max}=5.3$) have a maximum bank angle of 79°. Aerobatic gliders with $n_{max}$ between 7 and 10 can fly only slightly steeper turns (82°-84°).

If you're flying with an airspeed slower than design manoeuvring speed $V_A$ the limiting factor is the maximum lift coefficient. In that case, the formula gets
$$\phi_{max}=\arccos(\left(\frac{V_S}{V}\right) ^2)$$
$V_S$ is the stalling speed in the current configuration, $V$ the airspeed of the glider.

(own work)

Then, how do you get the tightest turn radius? With high speed and high bank angle or with low speed and low bank angle? Without the structural limitation the radius could become 0. With it, however, your best option to get a minimal turn radius is to fly with maneuvring speed and maximum load factor.
You can use the following diagram to calculate the minimum turn radius at any speed (just multiply the ordinate with the squared stall speed of your aircraft).

As stated in many comments, during aerobatics/dynamic manuevers you can get any bank angle for a certain (sometimes really short) period of time:

0°/180° bank angle Source

90° bank angle Source


What are the implications to consider when starting a university Flight Club?

What are the implications of starting a student Flight/Aviators Club,
  and what benefits could it provide, outside of meeting new aviation
  friends? (Implications referring to expected safety precautions a
  school might want to impose, any FAA regulations pertinent to a club,
  and associations/partnerships we could create to show legitimacy to
  the school)

I was in college not all that long ago and I can speak to this a bit as I was involved in some clubs that built cars (Formula SAE) while not the same I see a lot of parallels. Generally speaking, and this is very university dependent but I have seen it apply across the board, if a school puts money towards a club the club must abide by the school's rules but more importantly it typically falls under their insurance policy. For something like a poetry club there is not that much risk, but when we were racing cars the university would inspect them all the time and there always had to be a faculty member present when we were running tests. We were lucky in that we had good faculty backing which is key, my advice here is to first find a professor (you are generally going to need an advisor anyway) that flies and get them excited about it and onboard as this will go a long way to help your case.

What gets tricky here is you flying on the university's dime. If you are not looking to buy a plane and you simply want to use the funds for rental that is an interesting predicament. An aviation lawyer may be able to answer better for you, but you need to confirm what the deal is with using club/org/university funding to rent and fly planes. Technically you are not getting compensated to fly but you are also not paying to fly while someone is paying for the aircraft (you are in turn paying 0 which is below your pro-rata share). If the students are splitting the rental costs, renting from a local FBO and are all checked out in the airframe you don't really need to even get the university involved.

There are universities like Embry-Riddle that are very aviation focused and offer training as a part of the curriculum so there are places that do it.

Getting a local flight school or FBO involved may help if you have a place to rent planes from and can guarantee business they may offer a small price break.

I would reach out to the National Intercollegiate Flying Association and see if they can offer any advice or help.

  What would be a good way to find pilots within the University? (I'm
  sure out of 30,000 students there are some)

The airmen registry here in the US is public, you could always run it up against your school directory... I would ask around, post fliers etc. keep in mind that flying is not the cheapest hobby and college kids tend to not be all that cash liquid... I sure couldn't start flying until I had my first job.

  Would this be percieved by the general aviation community as "not my
  place" to start a student flying club, as I am a new pilot?

IMO pilots are very receptive of other pilots. Old pilots love to inspire young pilots and you will most likely find a lot of support from them. GA awareness is never a bad thing either!


What's the best way to get started flying?

I find climbing into the aircraft a good first step ;) Sorry, couldn't resist!

The best way to start is to find and visit a local airfield near where you live.

Most local airfields have some level of training taking place, and if the closest to you does not then another, perhaps slightly farther afield, will do.

Visit one of these flying schools and ask to speak to an instructor, a CFI, or an examiner. They will give you more details such as the aircraft they fly, the typical syllabus and the expected costs.

From there, you might like to start with a "trial flight" - typically 30-45 minute flight where you get to take controls and get a feel for piloting an aircraft.

Good luck.


Does lack of a curved taxi-line indicate a turn is not permitted?

No, lack of a centerline stripe doesn't restrict a controller from assigning that routing, nor does it restrict a pilot from turning there.
The stripe might be omitted because "that" turn wasn't anticipated to be used often, but the stripes (or lack thereof) carry no regulatory authority.


Why is the A380 a double-decker rather than a longer airplane?

That's right, having a longer plane would reduce drag by lowering the cross section (altho there is also drag linked to the surface area of the plane).

There is a few reasons why you don't want to do it:

Cylinders don't scale this way:

Take a cylinder with a radius of 1 and a height of 10.

Volume is ≈31.41

Double the height, volume is ≈62.83

Double the radius, volume is ≈125.66

Increasing the length scale linearly and increasing the volume scales at π * n * n

You will need a stronger structure to support the additional length and surface area of your pressure vessel, oscillations during turbulences, takeoff rotation, ...
All your cables, hydraulics, fuselage, will have to be stretched
Passengers will take forever to reach the back of the plane when boarding
Maneuvering in the airport will be impossible, you will need new airports  (credit apple maps)


How long are the nacelle strakes on a GE-90?

You can measure this on photos.

Find a nice side view that shows the nacelle strake.
Measure the engine diameter on the photo.
Find the engine diameter in the engine specifications.
Calculate the ratio between the two. This gives you a scale factor of the photo.
Measure the strake, multiply by the scale factor to give the size of the strake on the real engine.
Divide by the scale factor of your model to get the size of the strake on your model.

I use a spreadsheet so I can do step 2-6 once. I then create a formula that converts a dimension I measured on the photo to the one I need on the model. Makes it easy to do lots of measurements on a photo.
I usually import the photo into an application that uses SI measurement units (Adobe Illustrator), but you can measure in pixels too (which allows you to use cheap image tools).


Why don't the ATR 42's propellers start/stop rotating simultaneously?

Pilot only starts one engine at a time so the battery doesn't have to spin up both at once. At turnoff, one stop button is pressed before the other.


In the United States, are ultralights legally considered aircraft?

Yes, under FAA regulations, ultralight vehicles are considered to be aircraft.

14 CFR 1.1 states:

  Aircraft means a device that is used or intended to be used for flight in the air.

Ultralights are used or intended to be used for flight in the air, so they are aircraft.

14 CFR Part 103 defines the term "ultralight vehicle" and describes the rules for operating an ultralight vehicle. Although Part 103 avoids using the word "aircraft" to describe ultralight vehicles, nothing in Part 103 (or anywhere else) states that they are not aircraft.

It is true that ultralight vehicles are exempt from nearly all regulations governing aircraft. However, this isn't because ultralights aren't legally considered aircraft; it's because there are regulations which specifically make ultralights exempt from those regulations. For example:

Part 103, Section 7, states that

ultralight vehicles are not required to meet airworthiness standards,
pilots of ultralight vehicles are not required to have any kind of certificate, and
ultralight vehicles are not required to be registered.

Part 61, Section 51(j), states that pilots are only permitted to officially log flight time in aircraft that are registered (as well as military and public aircraft). Ultralights cannot be registered.
Part 91, Section 1(e), states that ultralight vehicles are exempt from Part 91 in its entirety. (If ultralight vehicles were not legally considered aircraft, then this paragraph would not need to exist!)

(Of course, a pilot may make logs of flights performed in ultralights, but the FAA does not recognize this time as "flight time".)

So, the FAA does consider ultralight vehicles to be aircraft. However, they are exempt from most—but not all—regulations which govern aircraft.


Would a chain strip built in the airport taxiways, help airlines in saving money and time during taxi?

Airports already have several ways to move aircraft along taxiways

Aircraft engines (least economical but always available)
Tugs (often used for pushback from terminals)
Aircraft wheel-motors (some makers are at least planning for electric taxi)

A system of fixed chains along a complex network of intersecting taxiways would be expensive to install and maintain and might be unreliable (e.g. icing up in cold weather).

See also

Does it make sense towing airplanes to the head of airstrip by external means?


Were planned release dates skipped in 2020 for the VFR sectional charts for Juneau Alaska and Dutch Harbor Alaska?

The FAA has just switched to a 56-day release cycle (double AIRAC cycle) for all VFR sectional charts. In the process of aligning the release cycle, they may have skipped an update. However, the chart of Dutch Harbor was on a cycle of one year before, and would have been due on 25th of February anyway. Juneau was also on a one-year schedule and would have been due on the 25th of March. It is very unlikely that a release would have been skipped.
The story behind the switch to the 56-day release schedule can be found in this FAA briefing. See Milestone #2 below, which may be the reason for skipping a release.

Background/Discussion: The lifecycles of FAA-produced Visual Flight
Rules (VFR) Charts vary from 168 days to two years and at one time
various charts did not update for years longer (Helicopter and Grand
Canyon for example).
Extended and unsynchronized lifecycles create an
undue burden on the NAS and on chart users. The NOTAM System must
carry many facility NOTAMs until consistently charted. As a result,
chart users are burdened with numerous NOTAMS and difficulty arises in
identifying pertinent NOTAMs and correctly applying them. Numerous
changes are alerted in Chart Supplement Chart Bulletins that many
users either do not know exist and/or do not find readily accessible.
Unsynchronized chart dates lead to inconsistent data capture on
overlapping areas, adjacent charts and other chart products.
Producing
56-day VFR Charts will provide significant relief to a number of these
issues. The NAS picture will be consistent with that reflected on
Enroute, Terminal and Supplemental products. NOTAMs will be
significantly reduced as charts will capture changes with every 56-
day AIRAC cycle. Chart Supplement Chart Bulletins will no longer be
necessary.
Planned Actions: Update the VFR Sectional, Terminal Area,
Flyway Planning and Helicopter Route Chart series on the 56-day AIRAC
cycle. Implement this effort across a series of milestones:
Milestone
#1 will synchronize the cutoff for VFR Charts with other aeronautical products. (June 18, 2020)
Milestone #2 will eliminate 28-Day AIRAC
date VFR Charts to align with airspace amendments and will stage
charts for 56-day AIRAC date production. (September 10, 2020)
Milestone #3 will realize full implementation of the 56-day update of
VFR Charts and elimination of supporting Chart Supplement Chart
Bulletins. (February 25, 2021)

And more history can be found here: VFR Chart Print Schedule Realignment and Synchronization


Why use a single engine plane instead of a multi engine one for a long range flight record?

As said in the comments, in a distance record aircraft you want to keep the drag and mass of your aircraft as low as possible. The previous and next record were flown in single engines too and risk assessment was a bit different back then.

Using a single engine for such long distances wasn't the only ANT-25 characteristic you wouldn't see in a normal airplane: the engine was underpowered (only Russian production engine available?) and for record flights the whole aircraft was even lack-stripped in order to weight less.

For emergency landings in the arctic they had skis, tents and other gear stored in the wings.

In the case of having to land on water they would jettison part of the fuel and inflate some kind of balloons which were inside the wings. That way the wings could be used as floating bodies and prevent water from entering. After water-ditching with retracted landing gear the aircraft could apparently stay afloat for a long time.

If you're interested in further details this biography of Pavel Sukhoi describes the project thoroughly in one of the chapters.


Why is an auditory alarm necessary when the autopilot disengages?

Yes, there have been several accidents caused when the autopilot has been inadvertently or automatically disconnected and the flight crew have failed to realise it happened. Even with the audible alert, it's reasonably common, but experiments in controlled conditions demonstrate that alerts provided in only one medium (just visual, or just auditory) are not reliably noticed in times of high workload.

Here's an interesting accident report I remember reading at the time, where the flight crew apparently failed to notice that they had deliberately disconnected the autopilot. For more on inattentional deafness, see the paper Failure to Detect Critical Auditory Alerts in the Cockpit: Evidence for Inattentional Deafness.


Isn't it dangerous for a soldier to sit on the outside of a flying helicopter?

To answer your question of is this dangerous, yes it is. It is very dangerous to be in a job where you voluntarily go into an environment in which you risk your life to combat other individuals who are actively trying to kill you. It would be much safer to never join the uniformed armed services.
On the other hand, in every activity, a certain amount of risk must be accepted while as much risk is eliminated or at least mitigated as possible. After reviewing the original picture from the Wikipedia link in your question, risk mitigation has been performed. The soldier on the outside of the aircraft has been tethered to the aircraft by safety lines attached to at least two points on the aircraft. These are the green high-strength webbing straps attached to two different handholds on the fuselage. These are clearly seen in the higher resolution original picture. You can also clearly see what looks like some type of safety tether deployment bag on his chest while the leg straps of his safety harness are also clearly visible.
Although safety measures have been taken, It is not very likely that the soldier on the outside of the aircraft could not hang on through sheer body strength. During regular maneuvers, his body weight alone should keep him in place.
Case in point, while serving as a paratrooper, I have jumped from UH1s, UH60s, and CH47s. It was quite common to sit on the floor of the aircraft with our feet dangling out of the open door. At other times, we would stand on the skids. Sometimes, the aircraft would be performing combat maneuvers. Only our left hands would be free to hold onto anything available while our right hands were protecting our reserve chute handles. Most likely our left hands were also occupied hanging on to rucksacks or weapons cases. Only a single webbing strap loosely stretched across the door served as our safety line. The load forces induced by gravity and the maneuvers kept us firmly seated during some very extreme banking.
Also, having done civilian skydiving from various Cessnas and Twin Otters, I can attest to the fact that the wind blast/slipstream, on the outside of the fuselage, while not quite pleasant, is not unbearable. It is not very difficult to hang on to the outside of an aircraft at cruise speed.
Although, never having to test a safety harness like this one, I do know that a tether similar to this one should be able to securely tow a fully kitted paratrooper, with a full combat load behind a fixed wing aircraft traveling in excess of 200 knots indicated airspeed. Just as long as his chute does not open. And military transport crew chiefs wear them all the time when moving around on the open tail ramp of an aircraft in flight. Some personnel also had similar harnesses to insert and extract personnel hanging from rigging lines or Fast ropes (SPIES/FRIES). You would literally be hanging under a helicopter in flight with less than the soldier in your picture keeping you alive.
As far as getting sucked into the intake of the turboshaft engine, I don’t think it would happen. It appears that the intake is shrouded enough to decrease or eliminate FOD (human or otherwise). It certainly is not as big and open as a high-bypass turbofan. But, I would have to defer to others with that particular knowledge and expertise.
Edit:
To respond to your edit of your question, there is very little danger that a harness inspected and approved for use would just tear. The webbing used to make the harness has a long and safe history. As I have pointed out above, it has been documented and proven to be able to handle loads many times greater than the weight of a human being in many safety and aviation related fields such as skydiving.
The webbing may be cut. But it would take a deliberate act or a very sharp projection to cut it. A projection like that on the aircraft would be noticed as being dangerous and far more likely to cut the soldier.
A more likely scenario is one where the bindings and buckles on the harness are not properly done when the soldier puts the harness on. The two leg straps and the chest harness gives you three separate failsafes. I would hazard a guess that a safety inspection of the harness, it’s donning and wear are accomplished by a specifically trained senior enlisted soldier like a crew chief, load master, jumpmaster, or rappel master before an operation such as this.


Flight Level Change or Vertical Speed - When to use it?

FLC mode maintains airspeed during a climb or descent, while VS mode maintains a specific vertical speed.

Often air traffic controllers will request that you "maintain 250 knots in the descent" or something to that effect, which is much easier to achieve when using Flight Level Change. As another answer points out, by maintaining airspeed, climbs are made safer as the autopilot will not attempt to maintain a rate of climb regardless of whether or not the airspeed is safe.

FLC mode is typically only available in advanced autopilots, and as far as I know they need to connect to an Air Data Computer to get the necessary information.

How to use FLC would depend on the equipment available to you:

aircraft with auto throttle will maintain speed and an appropriate rate of descent automatically.
for aircraft without auto throttle you'd set your target altitude, enable FLC, adjust your target speed if needed, and set your throttle for climb or descent to maintain the desired altitude change rate.

I'm referencing the Garmin GFC700 as it's the only autopilot I've used with FLC mode, but I imagine the same steps and rules would apply.


How often is QFE set on an altimeter during flight?

You don't use QFE or QNH in an airspace, you use it for a purpose.

QFE is rarely used in the US, other places in the world it's primarily used for landing, although that's personal preference (I use QNH). You set QNH on the ground at your departure airfield using the local setting then update QNH on route, when approaching an airfield for a landing you would use that airfield's QNH setting as given to you over the radio or from an information broadcast.

The only time I could see setting QFE more than once would be in the case of a diversion, if you needed to fly to another airfield you'd need to go back to QNH, then set the local QFE at the other airfield. This is extra workload and could be a forgotten step, which one of the reasons I prefer QNH for landing - it's one less thing to do.


How much energy/prop efficiency does the e-volo copter sacrifice by having a smaller propeller?

What counts is the mass of air which is available for lift/thrust creation. Several smaller props would still offer about the same area for lift creation as a single rotor, so in this respect that design is not at a disadvantage. The smaller props will have to spin faster than a single rotor to have the same average dynamic pressure, and the lift distribution over the whole area covered by propellers will be less asymmetric at forward speed than it is over the disc of a single rotor.

What should reduce the efficiency, however, is the smaller Reynolds number of the blades. Even if the blade airfoil is carefully optimized for their small Reynolds number, I would expect that at least 10% more energy is needed for the same lift compared to a conventional helicopter. The smaller inertia of the blades, however, is a big advantage in control, because the smaller propellers can be spun up or down faster, avoiding the more complex rotor head of conventional helicopters. With a modern FCS the e-volo should be controllable by individually adjusting prop speed alone. The electric motors most likely are capable of short-term torque bursts which far exceed their continuous performance, so control responsiveness should be adequate.

The smaller moment of inertia of the propellers becomes a liability in an emergency, because the e-volo arrangement is less capable of an autorotation landing in case the energy supply fails. That is probably the reason why the e-volo carries a full aircraft parachute. On the other hand, many small engines and propellers certainly improve redundancy over conventional helicopters.

I also have to wonder about the mass of the massive framework which is used to mount the rotors. It is in the way of the propeller flow and should contribute a substantial fraction to the empty mass of the e-volo. I expect the designers use it to store the battery cells, but I could not find much about this on the website - which offers, however, a funny movie which nicely sums up the projected capabilities. Just don't get distracted while the e-volo waits for you in hover mode: The claimed flight time is currently only 20 minutes.

My verdict: It is less efficient than a comparable helicopter, but not by much. The two problems are the lower blade chord, which translates into more viscous friction, and the high mass and drag of the framework.


Does distributed propulsion create unwanted lift at cruise speeds, requiring a negative angle of attack?

The fundamental way distributed propulsion adds extra lift is by blowing additional air over the wings. This is a direct thrust-to-lift conversion.

If you produce less thrust, you produce less lift with this arrangement.

So, no, you don't go to a negative AoA to counteract the excess lift produced by running all of your motors at full power. You never produce that excess lift in the first place. This involves running your wing propulsors at reduced power, and if you have lift-assist propulsors, such as blown flaps, turning them off altogether.


What is the aircraft model used in the film "American Made"?

If you are talking about the one prevalent in this trailer its an Piper Aerostar 600. The tail number is legitimate and the full registration details for 164HH can be found here.

Some of the movie may also have utilized a Beech Queen Air Model 88


Can a general aviation aircraft be forced to land when crossing the airspace of a country?

So in order to take your plane for a flight, you have to file a flight plan

Usually incorrect. Flight plans are only needed for international and for IFR flights. But there are some countries where a FPLN is required for every flight, but not Italy, Austria or Germany.

  when you are flying you have to, using the radio, let them know that you are on your way

Only if you've filed a Flight Plan. If you haven't, then there's no need to announce your flight.

  Can the Austrians ask me to land in their country for any reason

They can, it's their country. But unless you're a criminal or a terrorist, there's probably no reason for them to actually do this.

  Will they shoot me down if I don’t comply with them and land in Austria?

If they ask you to land (see above) and you don't, then they could shoot you down. It's their country and they're trying to protect it. But it hasn't happened yet.


What is this extension/device on top of the wing of this ultralight?

Those are wing fences and they prevent airflow perpendicular to the direction of travel. This isolates the portions of the wing and allows the inner wing to stall independently of the outer wing.

Since the wing uses flaps, the inner portion will create more lift and stall (separation of airflow on the upper wing leading to loss of lift) at a lower angle of attack. Wing fences prevent this stall from extending over the outer part with the ailerons, so the airplane will stay controllable in a stall and will not suddenly drop one wing.


Why does my Surface Analysis chart indicates radar returns / rain when none exist?

Fog and other low-altitude moisture often shows as very light precipitation radar returns. I look at the multi-image radar loops for an area, and if I see that I call a "sparkling" radar return in the looping image, it's a pretty good bet for ground fog. The California central valley area (around Modesto and Stockton) is known for its winter tule fog: watch the radar returns from that area in the wintertime.

You can correlate the radar observations with ground visibility observations (airport METARs, the regular and special airport weather observations, include visibility and ceiling—cloud height and coverage—information), along with satellite visible and infrared images to view cloud presence and cloud top heights. When the visible satellite shows clouds and the infrared satellite shows very low cloud tops, that's a good bet for fog or a low-level stratus layer: both have low cloud tops, typically 400'-1,000' above ground level.


How much weight does removing a vacuum system really save?

I removed the vacuum system in my VariEze a couple of years ago and saved 12 lb including the artificial horizon and heading indicator.  Probably about half of that was the instruments, the rest being in the pump/hose/regulator/filter/fittings.


How many US airman's certificates are revoked, roughly, per year?

FAA Order 2150.3B, Appendix B lists violations and the civil penalties (fines) and certificate actions which are to be imposed by the FAA. The rest of the document also discusses how investigations of certain violations are undertaken and thresholds. That order gives much more detail than you'd ever want to know.

A common theme is revocation is called for when the action is intentional.

These are what are the FAA initially charges you with, so they are higher than what actually happens. A certificate action is either negotiated as a settlement, or if it can't, it goes before an administrative law judge, then appealed to the NTSB, then appealed to the Federal court system.


Why can't lifting line model be applied to yawed/skewed/oblique straight wing (low M)

Lifting Line analysis is not suitable for low aspect ratio wing, highly swept wing or a wing undergoing large sideslip, because each of these would have significant spanwise flow gradient.
To see why, it's worth revisiting the central equation of the Lifting Line, applicable to a planar wing:
$$c_l(y)=a_0 \left[ \alpha - \frac{w(y)}{V_\infty} - \alpha_{L=0} + \theta_t(y) \right]= \frac{2}{V^2_\infty c(y)} \lVert \vec{V}_\infty \times \vec{\Gamma}(y) \rVert$$
where $y$ is the spanwise coordinate of the section, $c_l$ is the 2D airfoil lift coefficient, $a_0$ is the 2D airfoil lift slope, $\alpha$ is the free-stream angle of attack against the wing, $w$ is the downwash generated by the trailing vortices1, $\alpha_{L=0}$ is the 2D airfoil zero-lift angle of attack (or aerodynamic twist), $\theta_t$ is the geometric twist of the section, $c$ is the section chord length, $\vec{V}_\infty$ and $V_\infty$ are the vector and magnitude of the free-stream air velocity against the wing, and $\vec{\Gamma}$ is the bound vortex strength at the section2.
The left hand side of the central equation is the 2D airfoil lift and the right hand side is the lift we expect from the circulation generated by the bound vortex. Assuming the 2D characteristics are known in advance (i.e. the 2D lift slope, zero lift AOA, etc), and the wing geometry is known (chord length at every section), then we should be able to calculate the unknown, $\Gamma$, at every section.
To put it crudely, Lifting Line is cheating: it relies on you knowing the 2D airfoil characteristics apriori, in order to calculate the 3D lift and drag (which is its biggest advantage). The downside is that it inherently assumes the 2D data tells the whole story; all influences from the neighbouring sections are lumped into a single downwash (induced AOA), which remains 2D. In a highly swept or sideslip'ed wing, this assumption breaks down.

1 $w$ can be calculated using Biot-Savart from the trailing vortices (which have constant strength, $d{\Gamma}/dy$, along the filament), but will need to be slightly modified from the typical result shown for the Classical Lifting Line (which is only applicable for straight tapered wing), since the trailing legs are parallel to the freestream, not the bound vortex.
2 Note that I've used the vectorized version of the Kutta-Joukowski Theorem since in a swept or sideslip'ed wing the bound vortex and freestream aren't perpendicular.


Why is it rare for small aircraft to have winglets?

I've talked to a couple of aerodynamicists, and for small aircraft when you run the numbers the improvement offered by winglets is often less than the drag penalty caused by their weight (which also reduces allowable payload). For larger aircraft that fly long distances, the proportion of the aircraft's weight that is due to the winglets is much smaller than it is for small aircraft, so they don't have this problem and that makes winglets a viable strategy.


Was smoking banned because of passenger safety or occupational safety?

If you look at the part of the Federal code (49 U.S. Code § 41706) that actually instantiates this :

  (a) Smoking Prohibition in Interstate and Intrastate Air
  Transportation.— An individual may not smoke— (1) in an aircraft in
  scheduled passenger interstate or intrastate air transportation; or
  (2) in an aircraft in nonscheduled passenger interstate or intrastate
  air transportation, if a flight attendant is a required crewmember on
  the aircraft (as determined by the Administrator of the Federal
  Aviation Administration). (b) Smoking Prohibition in Foreign Air
  Transportation.— The Secretary of Transportation shall require all air
  carriers and foreign air carriers to prohibit smoking— (1) in an
  aircraft in scheduled passenger foreign air transportation; and (2) in
  an aircraft in nonscheduled passenger foreign air transportation, if a
  flight attendant is a required crewmember on the aircraft (as
  determined by the Administrator or a foreign government).

It is the presence of a flight attendant that triggers the non-smoking requirement. Thus, one can safely assume that it is an occupational safety concern (sidestream smoke) that forced the regulation change.


Could a Dyson fan displace more air without increasing the fan size?

Thrust is small amounts of air at high speed correct me if I'm wrong.

No, more air at lower speed is more efficient. Thrust is derivative of momentum added to the air, while power is derivative of kinetic energy added to it. Since momentum grows with velocity, but energy with square of velocity, accelerating more air by less creates the same thrust with less power.

Dyson fan works by blowing a thin stream of high velocity air along the ring, which then pulls in more air to create a very smooth air flow through the ring. To create this high velocity flow, you have to provide a lot of energy, which will then dissipate as heat when the streams mix, but you have no way to recover any of it as it happens already behind the fan. So it is very inefficient and while adding power will make it generate more thrust, it will only further reduce the efficiency as the flow speed increases.


Approximately, yes.
Both lift and drag depend on the density of air, so in order to generate enough lift at the same angle of attack in thinner air, an aircraft has to fly faster. Thus the same number of air molecules hit the plane every second and the drag is approximately the same.
This is a bit of a simplification (especially the bit about drag being caused by air molecules hitting the plane) as the change in temperature causes a slight change in viscosity, which affects one type of drag (detailed Peter's linked question). However it's a good enough approximation for most pilots, who use 'Indicated Air Speed' as a air-density-independent guide to aerodynamic speed.


Aerodynamic heating will damage or destroy the composite wing of the F-22, especially around the leading edge where compression heating is highest. See here for the temperatures which supersonic flight causes.

Therefore, the F-22 has been restricted to Mach 1.8 for short duration and Mach 1.6 for prolonged flight. More speed will not be needed, anyway.

The internal weapons storage of the F-22 makes it bulkier than the F-15 which causes more wave drag. Also, the engine intakes were not designed to operate at speeds above Mach 2, so pressure recovery in them drops at higher speed. These two factors will affect the top speed of the F-22 negatively, so I would not be surprised if the F-15 is faster even without restrictions on the F-22 speed.


I need to clean my aircraft's windows - what do I use?

I assume that your aircraft has acrylic windows. This is a very soft material which is easily scratched and cracks under stress. For cleaning, use these steps:

Rinse with lots of water to remove dust.
Wipe with a wet, soft sponge. Don't press on the sponge and move it in the direction of airflow. Moving the sponge sideways will increase the risk of sideways scratches which are caused by the movement of dirt particles over the acrylic surface. Those sideways scratches will impair vision when flying into the direction of a low sun.
Dry the surface with a chamois leather, again moving in flow direction.

Superficial scratches can be removed by polishing the surface with an acrylic or metal polish. Be careful with sandpaper because this could take off more material than necessary, resulting in optical distortions when looking through the polished area at an angle.

Never use alcohol or other organic solvents!


Do nacelles around aircraft engines help in reducing the engine sound?

Take a modern turbofan: The tips of the fan run at approximately Mach 1.5. We know from unducted props that supersonic tips make them very noisy. The same turbofan without the shroud would be extremely noisy, too. Acoustic liners on the inside of the fan shroud have major contribution in suppressing this noise source.

But there is more: The nacelle also makes it possible to put an intake in front of the fan which helps to equalize flow conditions over the cross section of the intake and to accelerate or slow the flow of air to just the right amount for the engine. Without the intake, the engine would suffer from frequent compressor stalls and surges, so the nacelle in effect widens the operating conditions and avoids those noisy incidents, too.

Another important source of noise is the nozzle: Here the hot, fast gas from the engine is ejected into the surrounding flow, and the mixing of both creates most of the engine noise. Note that noise increases with the sixth to eighth power of jet velocity, so the most dramatic noise reduction is possible with higher bypass ratio engines.

Diagram from the Stanford web page linked above. The jet velocity is in ft/s.

By serrating the trailing edge of the nozzle, this mixing process can be slowed down somewhat and the noise level can be reduced.

Without the nacelle the engine would create much less thrust and more drag, and bigger, more powerful engines would be needed. Bigger engines would create more noise, too, so this is also an indirect way how nacelles help to keep noise down.

A last noise reduction contribution to mention here is the capacity of the nacelle to contain the shrapnel from a failed fan blade. Fan blade failure is all but silent, but if the blade fragments would escape at high speed, the noise of what follows next would also be considerable.


It's the same thing, it changes only the point of view, see Newton's third law: for each action there is an equal and opposite reaction, i.e. to create thrust, the engine has to push air backwards. Pushing the air backwards means that the air is pushing you forward and this, in the reference system of the propeller blade, is lift.


What connector standard is used for aviation headsets?

It's for the microphone (the standard sized one is for the head phones). They are different size so the pilot knows to try the other hole if it doesn't fit.

From wikipedia:

  Commercial and general aviation (GA) civil airplane headset plugs are
  similar, but not identical. A standard 1⁄4 in monaural plug, type
  PJ-055, is used for headphones, paired with special tip-ring-sleeve,
  0.206 inch diameter plug, type PJ-068, for the microphone. On the microphone plug the Ring is used for the microphone 'hot' and the
  sleeve is common or microphone 'Lo'.


What is this fighter jet seen at Centennial Airport?

That is a Boeing F/A-18E Super Hornet.  The Super Hornet can be readily identified from legacy F-18s by its larger size, enlarged, hood-like leading edge extensions, larger flaps and flight control surfaces, and the rhombohedral shaped engine intakes to reduce the aircraft’s frontal radar cross section.  It’s tail insignia indicates that it’s a line aircraft with the United States Navy’s VFA-143 “Pukin’ Dogs” strike fighter squadron based out of NAS Oceania, near Norfolk, VA.


Who decides an aircraft's maintenance schedule?

The manufacturer lists all maintenance that should be done, and when. This is the first document you found, from Boeing. Some of this maintenance may be required, other things might be recommended.

The operator can use that plan, while following maintenance laws (e.g. the required annual inspection). Or, they can submit a new rolling maintenance plan to their National Aviation Authority (e.g. FAA) for approval, which is usually done to prevent large downtime events for the aircraft. (This "rolling inspection" is done so that all of the necessary things are inspected at the proper intervals, but not all at the same time.)

There's a bit more, too: the Aviation Authorities can create Airworthiness Directives that can add additional required maintenance that must be done within certain limits (usually hourly, but can be situation dependent) for the aircraft to be airworthy.


Why the number 6 in P6SM in a METAR/TAF?

The METAR format is defined by the World Meteorological Organization's (WMO)  on behalf of ICAO. According to the specification (section 15.6.3), visibility is to be reported in meters. The upper bound for visibility reporting is 9999, which indicates the visibility exceeds 10 kilometers.

In North America, the METARs deviate from the standard format by using non-standard units. Visibility is reported in statue miles. Six statue miles is equivalent to 10 kilometers.

Hence > 6 statue miles is equal to the standard > 10 kilometers.


Technically yes, but I do not know of any simulator which includes this. The water forces can be calculated in the same way as the air forces, so I see no reason why it should't be possible.

Historically, model tests were made to check that a new airplane would behave well when landing on water. The simplest tests would use a catapult and launch the aircraft model into a lake, and more thorough tests use water tanks where the airplane model is pulled along the water surface while being suspended on a rig. This allows to measure forces, while the catapult launch will only show the dynamics of a water landing. Results like these could be used to calibrate the computer model, so you can be sure it behaves like the real thing.


What is the difference between a fix, a waypoint and an intersection?

No, they are not interchangeable and indeed, have well defined meanings.

A fix is an arbitrary point in space used to establish current position calculated by referring to external references.  You take a fix to determine where you are now.  A fix might be permanent, for example a compulsory reporting point, or it might be determined by the pilot in advance in order to fly a non-airways route (e.g. when flying VFR) and then checked along the way using dead reckoning and reference to external systems or features to check that the plan is being flown accurately.  It might also be requested by ATC, e.g. "report when overhead the railroad yard" or calculated to establish where you are, e.g. taking a fix from an astrolabe on a night oceanic crossing.

From FlightGear.

A waypoint is fixed point in 2D space (latitude and longitude) used to define points along a route.  They are named, and are referenced in a plan.  You fly from one waypoint to the next, along a route.  A waypoint is where you are flying to.  It is normally positioned where there is a change of course or altitude.

These are the navigation positions given the 5 letter names you ask about.

From SailTrain.

An intersection is where two airways cross. Here, the Victor airways 15 and 76 cross at the intersection.  In this particular case, the chart symbol further shows that the V76 airway does not use the intersection, in which case the chart will include a note of the intersection usage.

From Jepptech.

Now sorry about this, but having said they are not interchangeable, it's not that simple.  A waypoint is also a fix (a fix is any 2D point).  But you do not call a waypoint a fix.  A fix is a 2D point which is not a waypoint, but is used for navigation.  A fix might be also be a lat and long defining the beginning of an arrival or departure procedure where you leave or enter an airway.

An intersection is also a fix, but it only exists to define where two airways cross (or where any other 2 lines cross, e.g. the 170 degree and 046 degree radial from two NDB beacons) so is called an intersection, not a fix.

In that sense, they are all fixes but the name has meaning.


Can one fly up side down while a glass of water keeps full due to g-forces?

Yes, as long as you continue the loop, and don't fly the plane in the upside-down position.

See, for example: Barrel roll with a glass of water on a glider


Can I check my density altitude with brake tension?

You may be able to get a rough estimate of if your engine is producing sufficient thrust utilizing brake pressure. But, how will you determine how much thrust is being produced? Your brakes are not calibrated so carefully as to adequately determine that. You would only be guessing. You might get a better indication of engine performance by utilizing the sound of the engine.
The best way to tell if your engine is producing enough power with a fixed pitch prop is using your tachometer. One is required for all flight in a powered civil aircraft with a standard category U.S. airworthiness certificate in the US by 14 CFR 91.205. With a constant speed prop, you are required to have a manifold pressure gauge to indicate the power output of the engine.
On the other hand, even if you could judge your engine output without instruments, it still would not account for the effect of density altitude on the lift producing airfoils. Instead, you are better off determining density altitude using the weather data that you should have reviewed during your preflight planning required by 14 CFR 91.103. For that, you need no aircraft instruments.


Is there an API to get real-time FAA flight data?

You can't get real-time data from the FAA without an operational need, and organizations which do receive real-time data cannot legally re-distribute this data publicly, except to other organizations approved by the FAA. An operational need pretty much means you have to be a flight dispatcher for an airline or commercial operator, not just have an interest in tracking flights.

You can get some real-time data from your local area using an ADS-B receiver. See this  question for more information: Where can I find real-time flight tracking with the least amount of delay?.

If you are okay with the five minute delay, then flightaware has an API you might consider. The direct feed from the FAA is called Aircraft Situation Display to Industry (ASDI) and I believe you can apply for the delayed feed, though I've never gone through the process, and the government's site is very sparse in information. I would suggest contacting them before attempting to apply if it's something you're interested in.


How are fly-by-wire airliners controlled in case of complete electrical failure?

For the complete electrical failure in the aircraft, the following systems have to fail:

The onboard power generation system, usually a synchronous generator has to fail in all the engines.
The APU (Auxiliary Power Unit) has to fail.
The RAT (Ram Air Turbine) should fail to deploy.
The batteries and static inverters should fail (this won't help in controlling the aircraft, just added for sake of completeness).

The probability of this happening is very very low, and can be discounted. It is more probable that some other system (for e.g, hydraulics) fail before this happening. So far, to the best of my knowledge, no complete power loss has been reported in any fly by wire aircraft.

The reason the Airbus aircrafts are controllable in case of electrical failure is due to the fact that the fly-by-wire system has multiple redundancies that offer layered protection:

Normal Law offers all the protections (like stall, load factor etc). This is the system in operation during normal flights.
Alternate Law offers limited protection including stability, load factor and stall protections
Abnormal Alternate Law limits the load factors and offers yaw damping only
Direct Law is the lowest level of fly-by-wire system and directly transmits the pilot inputs to control surfaces, while still giving stall and load factor warnings
In case all these fail, the system reverts to mechanical backup, where pitch control is achieved through the horizontal stabilizer and lateral control is accomplished using the rudder pedals.

In case of mechanical backup, the system will operate as long as hydraulic power is available. In case of electrical failure, as long as hydraulics are OK, the pilot should be able to control the aircraft.

However, usually, if there is no power, there is no hydraulic pressure (except reservoir, maybe) and the control is lost. In case of the Baghdad DHL aircraft, only hydraulics was lost and power was available.

There are some more points to consider in case of total electrical failure.

In case the control surfaces are moved by electric power (like 787), power loss means loss of control.
Power loss implies that the engine thrust cannot be controlled (of course, the engines won't be operational in that case anyway).
Some fly-by-wire aircrafts are unstable by design. In these cases, any power loss will lead to loss of control and crash.
I'm not sure there is any direct mechanical linkage in civil airliners. The amount of force required to operate such a system would be enormous.

Bottom-line is, in case of complete power failure, the aircraft is as good as dead. One example is a Fairchild Swearingen Metroliner (which was not fly-by-wire), that lost complete electrical power due to a lightning strike. The aircraft entered into a uncontrolled flight, which loaded the aircraft beyond limit, resulting in its disintegration.


How does the advancing wing in a flat spin create nose thrust?

A very good question, considering so many people do not draw the thrust vector for gliders.

The wing generates thrust by converting energy from falling to forward motion.  From scratch building gliders (and reading) one comes to realize that a falling parachute (straight down) only uses drag to reach a constant rate of descent.

A glider, with its center or gravity off set from its center of pressure (including tail!!!) will start to move sideways (glidogenesis) and generate lift with its wing.  This motion, known as "thrust" in this example, uses altitude as fuel and falling as its engine.

Notice both wings may be "thrusting" as it corkscrews down, but the outside wing, with its lower AOA, generates more lift/thrust and much less drag, sustaining the spin.

Once yawing is stopped, the wings equalize, and can be unstalled by lowering angle of attack.


Do twin engine airplanes have increased roll stability?

You're imagining the wind coming from the right, pushing the nose to the left. That doesn't happen. In fact, this is much more likely to push the nose to the right, because the vertical stabilizer, being a large panel that's far from the center of mass, creates a larger torque. This phenomenon is called "weathervaning", and is a huge concern for tailwheel planes and seaplanes particularly.
But, to get to the actual question: You are correct in thinking that, if a plane is yawing to the left, the outside wing is going to generate more lift, causing it to roll left. But, no, having multiple engines on an airplane will not stabilize it in either roll or yaw. For all the thrust from the left engine is doing to counter the yaw, the right engine's thrust is balancing it out, so a twin engine will not be any more stable than a single engine, all else being equal.


Why did some Caravelles have a very long dorsal fin?

The dorsal ridge housed avionics and HF antennas. From this document:

  The most noticeable difference are the larger cockpit
  windows and the removal of the dorsal fin (the long fin on top of the
  fuselage), that housed avionics. The 6R's not built for United did
  have the dorsal fin, though.

This is a non metallic radome. It protects the antenna from aerodynamic effects, and from water and ice which damage antenna electromagnetic characteristics. Closer view:

Source

The HF antenna was required when using long range HF navigation (Loran) and HF communications, typically over oceans and large non populated areas.

These features were not useful when flying over populated land, where VHF aids and VHF communication were possible.

There is a list of C/N without the dorsal fin in this forum. When the antenna is not under a radome, it looks like this:

Source (simulator)

See also: What is this wire going from mid-fuselage to the tail on this 737?

Progress in antenna design and receivers with (hugely) increased sensibility allow for smaller antennas, that can afford to be vertical with some signal losses. Today HF antennas tend to be vertical and under a radome at the leading edge of the vertical stabilizer:

Source

Helicopters, civil and military still use long wire antennas as antenna rails when they need HF:

Source

See also: What is this pipe on the tail of this helicopter?


Why do parked planes lock the control surfaces?

In the small planes I fly, it is called a "Gust Lock", and consists of a small metal bar that fixes the yoke in position, so that the yoke cannot move (left/right, or forward/back), and by association, the ailerons and elevator cannot move either.

As the name implies, this is for dealing with Gusts of wind... a sudden bit of wind over an unlocked surface can move the surface to its extreme position until it hits a mechanical stop.  If this happens repeatedly, say, over a stormy night, the repeated banging into a mechanical stop can create wear and tear on the surface, the control cables, or the yoke in the cockpit.


I would want to build in a way for the plane to try and save itself if possible (to save money) by auto-landing

Had the situation allowed saving the airplane the human pilot would definitely have tried that first. The fact that a trained fighter jet pilot decided to eject from an aircraft knowing that the ejection was a last resort and could be deadly, signifies that the plane was not able to be flown safely anymore.

On top of numerous irrecoverable problems at that point, one of the most significant issues is the fact that ejection destabilizes the flight path and the increased drag (because there is no longer a canopy on top) makes it even harder to safely glide that jet, let alone land it somewhere.

There is nothing much autopilot can do at that point.

There have been two famous incidents that are related to your question but afaik neither of them involve Auto Pilot.

1989 Belgian MiG-23 crash
Cornfield Bomber

It's just like saying I know the airplane can be saved but my computer will take care of it, I'm outta here. See you at the Court Martial.

Some commentators have noted that I did not answer one basic question:

  Don't forget to answer the question "If a pilot ejects, what is the autopilot programmed to do?", even if the question seems moot

This question is too broad: there are numerous models of fighter jets all around the world, built by a number of manufactures and internal details of which are closely guarded secrets. You are not going to generally find out a manual on the web listing all the actions that the autopilot software will perform after a bail out. If the OP can narrow down the question to a certain model one can research and try to find something but I don't believe its going to be an easy find. Hence I'm sorry I don't have an answer to that question. I hope someone more knowledgeable goes ahead and posts an answer to that.


Why are you not allowed to use power sockets in the seats during takeoff and landings?

In case of emergencies.
If something unexpected happens during landing, you don't want people to trip over cables, look for their phone or whatever or start packing anything plugged into the socket. This is the same reason you are asked to stow away bags or any other loose items and so on as well.


It was tested at Denver airport by United for a few years ultimately the project was scraped due to jet bridge malfunction that lead to wing damage.

  The deciding factor arose out of an incident where one of the bridges
  malfunctioned and damaged the wing of Boeing 757, as ANN reported in
  March. United removed the section that failed, and stopped using the
  over-the-wing part on the other four bridges.

(source)

Side parked dual jet bridge terminals did exist in the early jet age but don't appear to be a great use of space and I cant find any evidence they allowed faster board speeds back then. Taxi in and out would always require quite a bit of bridge retraction and a careful tight turn.

(source)

In a lot of cases the rear of the aircraft is used to load on the new food and remove old garbage blocking the rear with exiting and entering passengers could get in the way of the operations during fast turn arounds.

(source)

As you note you could always go under the wing and come back up. In areas where inclement weather is common you would need the ability to keep the whole jetway enclosed. This could get in the way of the wing unless it was either very low or underground, you would then need some form of retractable stair on the end. All in all it could be built but thats a lot of complexity to add into an airport ramp. This means down time for the gate and money lost for the airport. Depending on arrangement the tunnel may also need to be strong enough to support what ever is above it (vehicles, aircraft etc).


Why aren't planes loaded from both ends?

The aviation industry is already running at near-peak efficiency, performing crucial tasks simultaneously to ensure quick turn-around.  Trying to speed up the boarding process by allowing entrance from both ends would be doable with a large amount of changes to the existing process, in both operations and infrastructure.  However, the result would be horrendous and time- and resource-consuming at worst and comical at best.

Jetways need to be able to reach all points of ingress/egress, where currently, they only reach the forward doors.  Seeing as aircraft nose-in at the gate, to reach the aft doors would require a jetway that goes around the wing (above the wing is even less practical from a design/physics standpoint), effectively creating an even smaller limit to the size of the aircraft that can fit at the terminal since there is now a jetway that needs to reach the rear doors.  As you can see, the space between aircraft is already tight:  Or, you use a simple stairway at the aft door and allow passengers on the tarmac, an already busy place during aircraft turn-around, and we don't need them touching anything en route.  I highly recommend against the latter.

In many instances, during boarding, the rear and/or opposite-side doors are already in use for loading/unloading food and drinks and taking out the trash.  So you'd have to redesign that process.

Humans are generally stupid in large groups.  Southwest notwithstanding, your typical airline assigns seats.  Imagine a passenger entering the rear door with seat 1A.  It doesn't have to be that extreme.  It can be any seat assignment more forward than another passenger coming the opposite direction down the aisle, which has the effect of halting both directions of travel.  Passengers already sit in the wrong seats, or travel with babies, or carry too much luggage (or stow it selfishly).

There have been many studies on efficient boarding methods.  The most efficient algorithm seems to be the Steffen Method, but this method requires someone with an inordinate attention to detail (and willing passengers) to line people up in a specific order.  Taking into account crew resources, the most efficient method is by window-middle-aisle groups, then by random order (i.e. "single-zone"), with typical "zone boarding" least efficient.
EDIT:
There are scenarios where boarding from both ends makes sense and is feasible, e.g. smaller planes with fewer passengers.  On larger aircraft, the problem compounds itself as the number of passengers grows, each "collision" incident affecting that many more people in the queue.  Minimizing collisions requires airlines to throw more resources at the problem, namely personnel to direct traffic.  Ask any CFO - more often than not, human resources is the most significant slice of the operating budget.
In any case, engineering a solution should not entail best-case scenarios; it should be designed for typical-case at best, and more commonly for worst-case.  The human factor is one that cannot be overlooked.  There is no such thing as an idiot-proof system.


Can a runway turnpad be used as a runway holding position?

No, since you must have been cleared to enter the runway to be on the turn pad.  It is part of the runway.

From the point at which an aircraft is cleared to enter the runway, until it reports vacated or departs, the runway is occupied.


Can i create a home built aircraft with this engine?

It's a 100cc engine, and it's in the Radio Control section of that web site. It's an engine for model aircraft.

I suppose, technically, that's a home-built aircraft, but you're not going to sit in it!


How are go-arounds safe with close parallel runways?

The first thing I would point out is that LAX isn't going to be running simultaneous approaches on 24L and 24R or 25L and 25R. They'll select one of each of the parallel sets for the landing runways (typically the outer runways), and one of each for departing runways (typically the inner runways). For example, they might be landing on 25L and 24R and departing 25R and 24L. So, there's quite a bit of distance between those runways, and very little risk in a go around situation.

Here's a diagram illustrating LAX's typical arrival/departure runway usage to make it more visually apparent what I mean:

The second part of your question about an aircraft taking off at the same time as a go-around certainly happens, and when it does, ATC needs to take action to ensure safety and separation. ATC separation requirements can be satisfied by altitude, distance, or divergence (and, in some cases, visual contact). In the situation you described, divergence is the quickest and safest way to achieve separation. I believe the requirement is 30°, so tower would typically order a go-around and order a new heading at least 30° off of runway heading. The geography of the area, layout of the airspace, and the approach patterns would likely dictate the exact procedure used at each airport since their two primary goals, in order, are going to be 1. safety, and 2. getting them back in the approach sequence.

In the LAX example, a go-around on 24R would most likely get a right turn, and 25L would most likely get  left turn (away from the airport) so as not to conflict with other departing or arriving traffic. This is one of a few reasons the outer runways are preferred for landing.


Are centrifugal compressors/turbines less efficient internally, and if so, why?

Internally the big difference is that with axial compressors, it's easy to have a multi-stage compressor to give considerably higher overall compression.
While it is possible to link centrifugal compressors together into a multi-stage engine, it's considerably less common, so most centrifugal compressor engines are limited to the compression they can get from one stage (usually around 4:1).
Axial flow engines get lower compression per stage (usually around 1.2:1), but it's easy to have multiple stages, so engines with 10-15 (or so) stages are fairly common. Given the difference in compression per stage, an axial flow engine typically needs about 8 stages to produce higher overall compression than a single-stage centrifugal compressor.
It is also possible to combine the two. At least to my knowledge, the most common layout in this case is multiple axial-flow stages, followed by a single final stage using a centrifugal compressor.
Here's one paper about using a final centrifugal compression stage, in case you care: https://doi.org/10.2514/6.2019-0944


What is the yellow marking underneath Delta A220 doors?

This is almost certainly an alignment marking for the passenger boarding bridge (jetway). You can find the same markings on other Delta aircraft as well:

(image sources: A320, B737, B767)

The dead giveaway is that these markers are found on the second door on the long haul jets, which are typically boarded through this door instead of the first one:

(image sources: A330, B777)

The jetways used by Delta will have a similar marking on them which aids in properly aligning them with the aircraft door such that the door can still be opened and passengers can safely board and disembark.

See also: What are these markings under the passenger door?


How much is airspeed reduced on an A10-Warthog when firing its cannon?

What acceleration is being applied to the aircraft (In m/s or kt/s)?

From XKCD we know that the gun

  produces almost five tons of recoil force

that is about 50000 newtons (round numbers for simplicity, they won't overly affect the results)

The acceleration is force divided by mass, and the A-10 has an empty mass of 11000 kg, and a MTOW of 23000 kg.

This gives an acceleration between $4.545\ \mathrm{m/s^2}$ and $2.174\ \mathrm{m/s^2}$.

The Wikipedia page about the GAU-8 mentions that

  While this recoil force is significant, in practice a cannon fire burst slows the aircraft only a few miles per hour in level flight.

and gives as a reference a book that I do not own, so I cannot verify.

  If there was infinite ammo and nothing like gun overheat, how long would it take to slow the plane down to stall speed, if initial speed was a usual A-10 speed.

With the additional assumption of thrust balancing only the aerodynamic drag, we can say the following: cruise speed is $155.6\ \mathrm{m/s}$, and stall speed is $61.11\ \mathrm{m/s}$ (see Wikipedia link above), so this means that it would take between ~34 and ~71 seconds to completely stop the aircraft; or between ~20 and ~43 seconds to stall it.

If instead we want to be more realistic, we have to assume that we have infinite fuel, that ammo and fuel do not factor in the weight computation, and that the yawing/pitching moments do not overcome actuator authority.

With all that in mind, we should start from firing the gun at strafe speed, not at cruise speed, since we want to hit a specific target on the ground, so we want to move as slowly as possible, to have the highest chances of hitting it. This means that our starting velocity would be above stall speed but not significantly, leading to a smaller margin of continuous fire before stalling, unless the throttle is opened (if possible) to counteract the extra "drag".

If we ignore the discussion about strafing and hitting the target, and we fire from cruise speed (and this is what is meant by "usual speed"), it is possible that stall is not achieved, since at lower speeds you will have more excess thrust (but we are still assuming that the firing only produces "drag" or a negligible amount of yawing/pitching moments). This means that we could settle at a lower speed, but the determination of the exact speed requires the knowledge of the exact drag and thrust characteristics of the aircraft, in addition to it being a function of the initial speed, see Koyovis' answer for some basic numbers.


Do you have to lubricate the shock strut?

Oleo struts and brakes used on light aircraft use MIL-H-5606H hydraulic fluid (the red stuff) as the internal damping agent/lubricant (be sure to check the manual anyway). It's a normal practice to clean the exposed chrome of the shock strut (it should be done with the tail held down to extend the strut all the way) with a clean cloth, then wiping it with a cloth with a little bit of 5606 to leave just a very light film to help lube the scraper and seals the next time the strut compresses (once that's done there is the film of internal fluid left behind by the seals).

The biggest enemy of oleo struts is silica particles (which are very hard) from outdoor dust which sticks to the chrome surface because of the fluid film left behind by the internal seals.  The silica collects in the seal cartridge and acts like lapping compound, accelerating wear (this is why desert operations are the toughest environment overall on any airplane).

As the strut ages and the seals wear and slowly start to leave behind more fluid each time the strut extends, dust collects faster and the whole process speeds up, so the strut should be kept clean as much as possible depending on how dusty the local environment is.

If it's your own plane, you should learn to do the published procedure yourself, because nobody else is going to do it between annuals.  If you're renting the plane, that's the owner's problem, and you just do your normal walkaround inspection.


This interesting British document on the G loads sustainable by German WW1 fighters pegs the highest G factor for a British fighter at 5.5G for reference, with the SE5. German fighters examined and tested by the British after the war didn't fare quite as well, with max G tending to be in the 2-3 G range, beyond which the rear wing spar would fail.

What is also important to consider is that WW1 aircraft on both sides were not capable of sustaining those G's for very long, due to the low airspeed and rather underpowered engines of that day. An aircraft sustaining very high G's bleeds off quite a bit of speed in the process, due to the increased drag.

A WW2 fighter capable of 300-350 knots with a 1500-2000 hp engine, can pull a lot of g's for a long time, before scrubbing off enough speed to be in danger. A WW1 fighter at 80 knots, with a 150-200 hp engine, would only be able to sustain high G's for a few seconds, before they lost enough airspeed to risk stalling.

The few motion pictures of dogfights of that era, presumably re-enacted, tend to reinforce this: the planes appear to make a series of brief sharp turns interspersed with returns to level or near level flight, sort of a jerky movement as opposed to the long high G turns of WW2 fighters.

Finally, there were techniques some pilots used to avoid blacking out. Major Greg Boyington, who had been a boxer before the war, reported withstanding more G's longer by tightening his neck muscles up.