How can I check pitot static leak without a test box? More than once on the ramp, I've wished I could check an aeroplane's pitot-static system for leaks, but I didn't have the test box.  I've since seen, in the FAA's handbook for checking  homebuilts, a way of gently pressurizing a pitot system which is great - a length of medical tubing is all you need.

Does anyone know if a similarly simply elegant arrangement exists for the static system?  I've tried a largish hypodermic syringe to check if the port was blocked, but the challenges are:

getting to sit tight on the static port, and
holding suction.

All suggestions welcome.

There are lots of challenges to testing a static system the way you describe.

First, you need something to fit over the static port (not too hard if it's a single fuselage port, slightly more difficult if it's two of them, and if it's on a mast like on some Piper aircraft you just lost a lot of "seal area" and made the task very difficult).
You can get around that with test kits by taking the static line(s) off & screwing the test kit directly to the plumbing, or by using a variety of adapters that come with the kits.

Second, you need to produce a known absolute pressure in the line and hold it for a given duration to check for leaks.
That's most of what those fancy boxes do - they bring the line to a given pressure altitude, and then you watch the altimeter and/or line pressure to see if it leaks air back into the system.

All that said, if you're willing to deal with a really rough test, you can still do this with a syringe and some medical tubing. This RV-12 builder shows you how:

Attach a syringe to some surgical tubing.
Put some air-tight tape over your other static port (if applicable)
Put some modeling clay around the static port.
DON'T get it in the hole - make kind of a cup around the hole.
Put the surgical tubing into the modeling clay and press the clay tight around the tube to seal the chamber over the static port.
Pull on the syringe until you "climb" to a convenient altitude.
Hold or lock the syringe in place and watch the altimeter to see how long it takes for air to leak into the system and lower your altitude.

This is nowhere near as precise as proper calibrated test equipment, but it should help you detect a gross leak in the static system.

just plumb a test port into the static line ---A "T" for instance---  then block the static ports--use soft silicone tubing to fit over the T and suck gently until the altimeter reads about 2k above field elevation put tongue over tube  very scientific    now watch for drop in altitude after VVI goes to zero  no more than 100 feet in a minute is acceptable  see 4313.1B for this technique


Can training for an Instrument Rating be applied towards a commercial pilot certificate? Per 14 CFR 61.129, a person who applies for a commercial pilot certificate for airplanes (both single and multiengine) must log at least ten hours of instrument training.

Assuming a pilot obtains their instrument rating prior to training for their commercial pilot certificate, can the instrument time logged during training for an instrument rating be used to satisfy this requirement (assuming class of aircraft requirements are met)?

Short answer: yes, if the training has been logged with the remark that it meets the requirements of both 61.129 and 61.65.

This topic became confusing because of an FAA interpretation that says:

  [...] are the requirements of 14 C.F.R. §61.129(c)(3)(i)
  [commercial certificate] met by the student getting an instrument
  rating or training for an instrument rating? The answer is no. The
  training giving to satisfy the instrument training aeronautical
  experience of §61.129(c)(3)(i) may also be used to count towards the
  aeronautical experience of §61.65(e) [instrument rating], but the
  opposite is not true. The reason for this is that the training
  required under §61.65(e) is general, while the training under
  §61.129(c)(3)(i) lists very specific operations that must be
  accomplished to satisfy the requirements.

But that interpretation was surprising to many people because it implied that a commercial certificate requires additional instrument training, even if you already hold an instrument rating. So AOPA requested a clarification (more information here); you can read the whole thing, but the key statement from the FAA is this:

  We are merely clarifying the requirement that the applicant for a
  commercial pilot certificate provide evidence that they have met the
  requirements of §61.129. There is not an exact equivalence between the
  training required for an instrument rating under §61.65 and the
  aeronautical experience requirements under §61.129.

Practically speaking (as the AOPA article explains) that means that your CFII should explicitly log the training as covering both requirements:

  [AOPA] urges instrument pilot applicants and flight instructors to be sure
  that instrument training is clearly logged to indicate that the
  training given meets the requirements of 14 CFR 61.65 as well as those
  of 14 CFR 61.129. That would avoid questions about the training’s
  applicability should the pilot one day advance to training for a
  commercial pilot certificate.

Yes.  However, the CFI must log the training as accomplishing the instrument time for the commercial certificate.

See the Theriault interpretation.


What is the FAA definition of solo flight? If I'm a student pilot (for commercial), and I flew for pleasure with friends one night, do I log those hours as solo? Does solo mean, only pilot in the aircraft? Or does it literally mean only person?

According to FAA, it means that the pilot should be the only person in the aircraft. According to 14 CFR § 61.51 - Pilot logbooks,

  (d) Logging of solo flight time. Except for a student pilot performing the duties of pilot in command of an airship requiring more than one pilot flight crewmember, a pilot may log as solo flight time only that flight time when the pilot is the sole occupant of the aircraft.

14 CFR § 61.8761.87 - Solo requirements for student pilots also says pretty much the same thing:

  (a) General. A student pilot may not operate an aircraft in solo flight unless that student has met the requirements of this section. The term “solo flight” as used in this subpart means that flight time during which a student pilot is the sole occupant of the aircraft or that flight time during which the student performs the duties of a pilot in command of a gas balloon or an airship requiring more than one pilot flight crewmember.

I am assuming you have a Private Pilot's certification?
(SEL or MEL etc. does not matter as long as you are type rated and certified to fly the airplane you going to go fly in with your friends)

If so, technically this flight of yours goes in your log book as just another regular flight. Can you count hours towards another certification (towards Commercial)? Yes, since you are still PIC. What you cannot do is be compensated for that flight. Pro-rate based fuel sharing is acceptable.


Why are fuel tanks located in wings? Passenger aircraft have fuel tanks in the wings. Why?
What are the advantages and disadvantages of this location ?

examples of disadvantages I would suspect:

added weight increases the structural load applied to the wings
different gravitational forces and wing-bending between full and empty tanks result in repeating stresses shortening the aircraft life-span
higher risk of catastrophic damage to wings in case of in-flight fuel ignition
higher risk of fire when lightning strikes a wing

Several advantages:

Wing structures are hollow and voluminous in order to provide structural rigidity against flutter and carry flight loads.  This provides the space needed to store fuel.
On a conventional aircraft, placing fuel tanks in the wings places the fuel mass very close to, or on, the center of lift.  This dramatically reduces Cg shift during flight and reduces the size and weight of the tailplane to maintain stable flight.  It also reduces Cg shifts due to sloshing of the fuel inside the tanks, due to the limited constraints of longitudinal travel for the fuel in the tanks.
In the event of a crash landing, having the fuel in the wings keeps it away from the cabin and the occupants, reducing risks of cabin fires.
The weight of the fuel reduces the loading moment on the wing roots, reducing the weight of the structure needed to support the aircraft during flight.
Fuel stored in the wings either partially or completely eliminates fuel storage in the fuselage, leaving more room for passengers and cargo.

Disadvantages:

1) Fuel sloshing with in the tanks laterally as a result of turbulence, or uncoordinated flight, can lead to lateral weight shift and potential lateral instability.   At low quantities of fuel, and in prolonged uncoordinated flight, there is a chance that the engine can suffer fuel starvation simply because the fuel has flowed out of the sumps in the tanks These problems can be alleviated with proper fuel tank baffling and the use of feeder hoppers fed by the main tanks which the engine drinks from.

2)  On aircraft which utilize a siphon feed fuel system such as low wing aircraft, the fuel cannot be evenly siphoned from both tanks at once.   This is a particular problem in single engine aircraft, where separate fuel systems are not dedicated to one engine in particular.   In such cases the engine will feed off either the left wing tank with a right wing tank  and this is controlled by means of a fuel selector valve in the cockpit. On aircraft that do not have automatic fuel management systems, engine fuel feed must be manually selected.  Care must be taken to alternate feed from both tanks periodically to prevent a lateral imbalance and fuel quantity. Additionally this fuel tank switching schedule, if ignored long enough, can potentially lead to fuel starvation of the engine and a forced landing.  This is particularly problematic in the low wing light single engine aircraft such as the Piper PA-28 or Cirrus SR-2X, especially if the pilot has recently transitioned into this airplane after flying high wing aircraft, which use gravity feed fuel systems, and allow the engine to feed from both tanks at once.  Larger single engine aircraft like the TBM have automatic fuel tank switching systems to address this problem.   Large multi engine jet aircraft have dedicated fuel management systems which address these problems.

There is no other reason.
The engine is attached to the wing and They are trying to design a fuel tank to fuel the engine,
There is no space on the torso. So they make a hole in the wings.


What is the difference between a 'live' NLG axle and a 'fixed' NLG axle? What are the advantages / disadvantages of a live and fixed nose landing gear axle and how do they work? Maybe certain aircraft need a particular type fitted?
I can't see the need of a moving axle (assuming that's what 'live' means) unless it is somehow powered by a motor or something similar for push back..

Or..
Maybe on an aircraft a live axle is one where it rotates with the wheel and a fixed one is where the wheel rotates around the axle?

The reason I ask is that I saw in a textbook that nose wheels are either on a fixed or live axle and nose wheel shimmy is prevented by using a twin nose wheel set up attached to a live axle.

I'm now not sure if the terms live and fixed axle are in relation to the vertical component or horizontal component of the nose gear.

A live axle is when the two wheels rotate together. Its function is to reduce shimmying.

The Lockheed JetStar and the Space Shuttle Orbiter have live NLG axles.

References:

Source: Aircraft Landing Gear Design: Principles and Practices

  The nose wheel is a split, forged aluminum alloy design but its bearings are located on a rotating or "live" axle rather than in the hub such as in the main wheel design. Both nose wheels are splined to the "live" nose axle providing a corotating feature which improves stability or reduces the tendency to shimmy.

Source: Orbiter wheel and tire certification, NASA

  Tire friction can also be used to increase the damping in the castor mode. If the gear has two wheels, connecting them by a live axle can have this effect. In the case of a single wheel, it is possible to obtain ‘anti-shimmy’ tires incorporating two contact areas.

Source: Landing Gear (Aircraft), sciencedirect.com

A fix Nose Landing Gear is a landing gear where the vertical axe between the aircraft and the wheel cannot rotate. The wheel can rotate of course on an horizontal axe (it is how it moves on the ground), but it can not rotate on a vertical axis. This mean that if you try to change your direction on the ground, the wheel will remain in the axis of your current direction, and it will drift when you turn.

A live NLG means that the wheel could rotate on a vertical axis, compared to the direction currently held by the fuselage of the plane. Thus, it is easier to turn when rolling on the ground, but when the airplane takes off or lands, it needs an anti-shimmy device (usually, as you said, a twin nose wheel) to perturbations on the landstrip to make the plane turn hard.

An example of such a thing is when you have a supermarket caddie, and the forward wheels are blocked. It is difficult to turn, but you still can if you put enough torque to the center of gravity of the caddie. On an airplane, having motors on the wings gives easily enought torque on the middle axis of the plane.


Does a headwind affect the climb gradient? When studying for my German PPL exam, I came across this question:

For those that do not speak German I'll try to translate the question, but bear with me as it is kinda picky what I'm trying to get across here:

  During flight on a straight track with constant speed

  headwind will increase the gradient of climb
  headwind will decrease the gradient of climb
  headwind will increase the distance needed to descent 50m
  headwind does not affect the gradient of climb at all

As you can see answer 4 is supposed to be the correct one. I disagree, so I started searching for a reason, yet I couldn't find anything useful. Let me explain my train of thoughts:

I didn't really know the "gradient of climb", I always used the two terms "angle of climb" and "rate of climb". Thus I'm trying to figure out which one the gradient of climb is. Common sense makes me think it is the same as the angle of climb (gradient does just sound like an angle). This opinion is supported by SIDs, which have a PDG (Procedure Design Gradient) that is given in percent, just like the gradient of climb.

Assuming the gradient of climb is indeed the same as the angle of climb, the only way for the "correct" answer to be confirmed is by taking the distance traveled during the climb relative to the air, not to the ground (angle of climb is defined as the height gained divided by the horizontal distance traveled in a certain amount of time). This would mean that it is used with IAS, rather than GS, which in my opinion absolutely makes no sense ("Hey look, that mountain is 10NM away, we are climbing with 600 ft/min. and going 100 KIAS and need 3500ft more to go over the top, we're all good!" - Well, add a tailwind of 25kts, the pilot would still think he's good to go but it'd result in CFIT...).

The question I have is: How is answer 4 the correct one?

The gradient of climb is the ratio of the increase of altitude to horizontal distance through the air, not over the ground.
The definition used by the UK CAA in CAP 698 is:

  Climb Gradient

  The ratio, in the same units of measurement, expressed
  as a percentage, as obtained from the formula:
  - $$\text{Gradient} = \frac{\text{Change in Height}}{\text{Horizontal Distance}} \times 100 \% $$

If you have a headwind or a tailwind it makes no difference to your climb gradient because your airplane is moving relative to the air mass.

Climb gradient is not the same as rate of climb, although they are related. Rate of climb is altitude over a period of time, gradient is climb over distance travelled. There is another question which covers the difference in more detail.

Wind adverseley affected to the climb gradient( weight, IAS, Large flap setting and acceleration also). As Climb gradient is a ratio of heigh to the travelled ground distance, wind affcet has a large. As  increasng altitude in steady wind condition with given IAS TAS increasing which same time decrerasing gradient. If climbing in tailwind also climb gradient is decraesing which distanve required to travell increase. With head wind climb gradient increase which decrease ground distance required to travel. Dont confuse it with Rate of Climb. Wind has no affect to ROC as roc is altitude change in unit of time.

Climb out in tailwind sometimes some pilots confuse it by setting large flap setting. But teh lage flap setting the more drag and less gradient. Best choise is (when rw is limited by lenght) use improved climb( high speed to allow creation more excess thrust)


Are planes allowed to fly through a planned professional fireworks display? I was watching 4th of July fireworks tonight, and I noticed a very low plane circling the fireworks display.

I'm wasn't sure of its altitude, but I would estimate around 1000 ft or no higher than 1500 ft.

I'm thinking, "that's pretty low around here", and "it would be cool to be in that plane, with that view."

The plane then turns sharper toward the fireworks, then flies right through the middle of it, as fireworks are going off around the plane.

The plane then circles around again and flies just above display this time.

Is this even allowed?

If not, how would this pilot be held accountable/caught?

If so, how is this safe?

Most fireworks go no higher than 1200 ft and consumer sized stuff is more around 500ft and below. which is fairly low for most regimes of flight for all but general aviation planes and planes taking off/landing. With this in mind your main point of concern would be shooting them off near an airport, or people flying low and slow near your display.

I cant find any regulation explicitly forbidding it although its unwise and it most likely would be considered "careless or reckless operation as per §91.31" if you flew directly (and deliberately) into a display at low altitude, Fireworks are noted in the NOTAM's and it is the pilots responsibility to make themselves aware of all flight risks and en-route information as per § 91.103 Preflight action. You can see a good example here in todays NOTAMs listing various firework displays and their locations.

(source)

Its also the responsibility of the launcher to file the NOTAM in the first place.

I'd imagine it's illegal based on the info found in these articles:

https://www.forbes.com/sites/gregorymcneal/2014/07/04/video-shows-drone-flying-through-fireworks/#6fcc908163c0

https://www.forbes.com/sites/gregorymcneal/2014/07/08/faa-investigating-fireworks-drone-flights/#734d1ef72a96

I know that these articles refer to drones, but an out of control manned aircraft is a bigger threat than a tiny drone.

As for holding the pilot accountable, I'm pretty sure ATC in the area has information on the aircraft which could probably be used to figure who was flying the aircraft at the time.


When did the color orange enter flight test? When did the color orange enter flight test?  As early as the Bell X-1, pictured here, aircraft were painted orange to enhance visibility. Later, in 1959, a study was conducted that suggested the utility of orange markings on aircraft.  In 1968, the Society of Flight Test Engineers adopted a logo with "flight test orange" as its color.

There are, however, few references that explain the following:

When orange flight test equipment (wires, parts, LRUs, etc.) first appeared.  For example, I transcribed a 1977 article from the SFTE's Flight Test News that sets 1949, anecdotally, as the time/event that caused Douglas to use orange wire. But it also references a Mil Spec. (Does anyone know more about the Mil Spec referred to?
When orange flight suits first appeared?
When aircraft (in general) adopted orange paint schemes for flight test aircraft, as seen here?

They were originally used to allow ground spotters to better spot the aircraft from the ground for optical tracking during flight test.  Another use of painting wingtips, tailplanes and tailfins bright colors was to allow observers a better means to determine the aircraft’s orientation and attitude in flight.

Finally if it all went so wrong so fast, hi viz colors made it easier for SAR crews to locate the wreckage....and the remains of the pilot.....quickly.

I know the Navy and the USMC were using orange flight suits as early as the Korean War, not for their test pilots, but for fleet air crews to make it easier for SAR aircraft to locate then in the event of a ditching or bailout over open water.

When aircraft (in general) adopted orange paint schemes for flight test aircraft, as seen here?

Never. Orange was used for a few aircraft only (X-1 is the most famous example), so it was never "generally adopted". In fact I have a hard time finding any other orange aircraft.

This happened right after the X-1:

X-2: white
X-3: white
X-4: white
X-5: white

An image search for "flight test aircraft" shows a sea of white and unpainted metal, with only a couple of orange ones in between.


Why does an aircraft's nose tend to pitch downward at higher bank angles? In the usual aircraft configuration, the center of lift is located behind the CG producing negative pitch moment (the horizontal stabilizer counteracts it by producing downforce - positive pitching moment). If the aircraft rolls to one side the vertical component of lift on the wings would decrease, so by that logic the aircraft should pitch up.

Why does it pitch down? What am I missing?

The answer is that the aircraft doesn't actually pitch down. When banking (or rolling) into a turn, the angle of attack (or the angle between the center of the wing and the flight path of the aircraft) stays the same. Assuming no correction to maintain altitude is made, the aircraft will continue on the same angle of attack, just banked over by some amount. Due to the bank, the lift produced by the wing is no longer vertical, instead, it is directly perpendicular (at least for our purposes) to the wings. Therefore, if the airplane is in a 30 degree bank, then the lift vector will also be 30 degrees from vertical. Doing some vector analysis, then you can determine that if the angle of attack hasn't changed the new vertical component of lift will be about 86% of what it was in level flight. Therefore, the plane would begin losing altitude. This altitude loss is what you see as the airplane pitching down.

Darjan,  first the basics.  An aircraft in straight and level flight has the center of all lifts balanced with the center of gravity.  A plane with the center of gravity set forward of the WING center of lift requires down force on the tail to balance it.

Now roll 45 degrees.  Gravity vector is no longer aligned with elevator trim.  If you roll 90 degrees the rudder is now you "elevator" relative to CG.  Unless you apply opposite rudder, a
forward CG set nose will drop.  This, among other reasons, is why aerobatic planes like their
CG further back.

Agree with @PilotDan that bank will also cause reduced vertical lift, but a forward set CG will also drop the nose.  Many pilots will try to pull harder on the yoke to maintain altitude, adding power seemed to work better for steep turns, as well as reducing bank angle.

Bottom line, forward set CG is not a panacea of safety in all cases.  Published forward CG
limit is best adhered too.


What's the difference between a balked landing and a go-around? Is there a difference between a balked landing and a go-around?

If there is, what exactly is a balked landing?

The only term in the Pilot Controller Glossary is Go Around, so should technically be the only term used, at least when communicating with ATC:

  GO AROUND- Instructions for a pilot to abandon his/her approach to landing. Additional instructions may follow. Unless otherwise advised
  by ATC, a VFR aircraft or an aircraft conducting visual approach
  should overfly the runway while climbing to traffic pattern altitude
  and enter the traffic pattern via the crosswind leg. A pilot on an IFR
  flight plan making an instrument approach should execute the published
  missed approach procedure or proceed as instructed by ATC; e.g., "Go
  around" (additional instructions if required).

  (See LOW APPROACH.)

  (See MISSED APPROACH.)

The ATP PTS also includes a Rejected Landing, which is what our simulator instructors refer to as a Balked Landing, and must be at or below 50 feet AGL.  It has the following note describing it in the PTS:

  NOTE: The maneuver may be combined with instrument, circling,  or missed approach procedures, but instrument conditions  need not be
  simulated below 100 feet above the runway.  This maneuver should be
  initiated approximately 50 feet  above the runway or landing area and
  approximately over  the runway threshold or as recommended by the FSB
  Report.

The pilot follows the same procedures for both of them by aborting the landing, cleaning up the airplane, and flying the appropriate procedure afterwards.

balked landing :  is a go-around initiated after touchdown but before thrust reverser selection .
(source: Term from Boeing bulletin)


Are there any runways that aren't labeled reciprocally to each other? Runways are generally labeled by their magnetic azimuth between 01 and 36. This means that runways are normally labeled on each end with a number that is reciprocal to the other by 180 degrees.

Do any runways exist where the approach ends aren't labeled reciprocally to each other?

Elk City, ID has runway 14/35 with about 30 degrees between reciprocal approach paths:

No, but at airports with multiple, parallel runways they will use an adjacent runway heading.

Example: KATL, Hartsfield Jackson Intl, in Atlanta, GA, which has five east-west parallel runways designates them Runways 8L-26R, 8R-26L, 9L-27R, 9R-27R, and 10-28.


Was the Boeing 747 designed to be supersonic? I heard a rumour that the Boeing 747 was originally designed for supersonic cruising.

Is this correct? Are the airframe and wings able to cross the sound barrier without damage?

No. The Boeing 747 was not designed for supersonic flight, though during testing, it was pushed quite close to the sonic speed:

Tom Cole, a spokesman at Boeing Commercial Airplane Co., said original flight tests of 747s conducted in 1969 and 1970 took 747-100 models to speeds of Mach 0.99.

However, the aircraft is not built for sustained supersonic speeds:

... Boeing and the FAA said the 747 is not built for sustained flight at the speed of sound. Its engines aren't powerful enough nor is it designed to deal with a destabilizing shock wave that develops around the speed of sound.

However, it is just possible that the airframe and wings can cope up with the supersonic flight, at least for a little while, though any sustained flight is not possible. There have been cases where the 747 has gone quite near the speed of sound and lived to tell the tale.
China Airlines Flight 006 went into a dive and went near supersonic speeds before the captain could recover it. As a result, large portions of the horizontal stabilizers were ripped off, and the wing was bent permanently upwards.

Damage to China Airlines Flight 006 empennage. By NTSB - China Airlines Boeing 747-SP Accident Report by NTSB, http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/ChinaAir/AAR8603.html, Public Domain, Link
In 1991, a Boeing 747 of Evergreen airlines entered a steep right wing bank and approached sonic speed before recovery was completed. NTSB notes:

... the airplane was in a steep right-wing-down bank. The flight  lost  approximately 10,000 feet of altitude, and the airplane approached supersonic speeds (0.98 Mach) before the recovery could  be  completed.

Later, the Israelis took it close to sonic speed. In these cases, parts of the aircraft certainly experienced local supersonic flow; however, the airframe and wings are not designed for supersonic flow nor are the engines powerful enough. In one case, the aircraft suffered extensive damage (though it was repaired and returned to service).

Absolutely in no way was the 747 intended or designed as a supersonic aircraft; for many technical reasons having to do with structures and aerodynamic/fluid mechanics, a 747, if pushed to the sound barrier breaking speed in the vicinity of 674 MPH, plus or minus with respect to air density in which the big airliner is flying, or beyond this speed, then structural air drag stresses would rip the wings from the fuselage. In comparison, go look at old photos of the Concorde and note the triangular, or delta wing configuration of this aircrafts wings and note that the wings do not flare out in a wide wingspan is in the 747. As well, the running length of attachment of the Concorde delta wings to fuselage is much greater than that longitudinal length of attachment-to-fuselage in the 747. There were of many other material and design differences between these two airliners to allow the Concorde to fly at supersonic speeds, and conversely, disallow these faster than the speed of sound abilities in the 747.


Meaning of XX below Slat FLap Trim on A350 with flap setting 1 What is the meaning of the 'XX' in amber below the 1 (in green) within the Slat Flap Trim section on the A350 PFD when the flaps are set to 1 with the correct speed (below 255kts)?

See picture attached. If the flaps would have failed, it would indicate XX without the 1. So, what else could this XX indicate?

The number below the flap indication is not the position of the flaps/slats, but the position of the flap lever. When the lever is moved, the number becomes cyan indicating that the flaps/slats are in transit and when they have reached the selected position the number becomes green.

Edit: As per FCOM, there is no mention of amber XX indication for flap lever position at all. Checked in a simulator that total computer failure will not cause indication to turn XX.

Thats your landing gear indication. The display unit is not receiving data for it. Normally when the gear is up nothing is shown.


How can an aircraft hover almost vertically? (Source: https://fat.gfycat.com/)
The aircraft in this GIF (although being an RC plane) seems to be flying vertically, just meters above the ground. How is this possible? How is it possible to control it in this scenario? Would this be possible with a real aircraft?

The aircraft in the video is a remote-controlled (rc) airplane. Why it can "hover" is simply:
The thrust generated by a big fan / rc-jet-engine is much higher than the weight of the plane.
If the force generated by the turbine is the same as the downward-force of weight of the airplane, it hovers.
By very carefully adjusting the thrust and placing the aircraft in this "nose-up" position, a skilled rc-pilot can hover the plane until the battery runs out or fuel gets low.

As example:
An aircraft that weights 10,000 kg's produces a downforce:
$$F=m\cdot g=10,000 \cdot  9.81  = 98,100N $$
To make this aircraft hover, you have to create a upward force of at least $98,100 N$. If you manage to do that and you can align the generated thrust / downforce perfectly on the Y-Axis, the aircraft will hover:
$F_{down} - F_{up} = 0N$, the two forces will cancel each other out and you don't have any movement in the Y-Axis.
However, if you have engines that create more thrust than the downforce, the following will happen:
$F_{down} - F_{up} \geq 0N$, that means the aircraft will climb vertically (On the Y-Axis).
The same principle applies to other "real" aircraft, like the Sea-Harrier:

It uses the engine to create a force facing upwards. Because the force is greater than the downward-force created by the aircrafts weight, the Harrier can land / takeoff vertically.
The hovering airctaft is controlled by a trust-vectoring fan / turbine. Controlling the plane with the "normal" surfaces is not possible, because the airflow over the controll-surfaces on the wing is to slow. Therefore, only planes with trust-vectoring capabilities COULD hover like the rc-plane in your question.

Its an rc basically you have more power more thrust and the airplane body is light as paper so u can hover with thrust and control with normal control surfaces.

In real aircraft its hard.


How close is X-Plane experience to real flying? I started using X-Plane and am surprised at the easiness of flying (using a flight controller). Does this simulation software reflect how it is to fly (in any way) in reality?

From using the simulator, I understand that all I need to do is to switch the engines on, turn the brakes off and fly. Are there any additional things apart from a pre-flight checklist that an actual airline pilot has to do?

In addition, I understand that I haven't dove into the details of navigation in X-Plane as I am just wondering if the basics of the simulator software reflect real life conditions.

X-Plane is a much truer simulation of flying than that flight game Microsoft used to make. In fact, when coupled with certified hardware and a CFI, X-Plane can power a sim that you can actually log FTD time in.

Since you ask about airline flying for your comparison, there is a lot more to that than just the flying. An airline pilot is, with few exceptions, always operating under instrument flight rules (IFR). This means flying in the clouds with no reference to anything but instruments, weather as bad as a few hundred feet visibility and strong crosswinds for landing and takeoff are all part of normal ops. You are also operating under ATC, so radio ops are normal. The only comparable computer simulation of ATC to reality is VATSIM (as mentioned in comments), though it doesn't approach the level of busyness that you'll find in some airspace and airports (with the exception of some of their organized fly-ins).

A transport category jet is also a bit more complicated than "turn the engines on, release the brakes and go". The only computer sims that capture the level of detail properly are ones like the A-10 simulator by DCS. Before you can start the engines, you need to first power the aircraft and perform your receiving checklists, and if you are the first flight of the day, additional first-flight checks. These cover:

Thorough pre-flight walkaround inspection
Powering the airplane on batteries
Transition to ground power (GPU) or start the APU for power
Verifying the state of all systems
Fire test
Stall warning test
Anti-ice system test
Checking oxygen levels and masks
Autopilot test
Backup instrumentation checks

Before pushback:

Verifying fuel load
Get load information from flight attendant/gate agent/dispatch/ramp supervisor
Calculate weight and balance, move passengers and/or bags if needed
Get ATC clearance and program FMS
Flight crew and cabin crew briefings
Weather briefing
Start APU and disconnect ground power and ground air conditioning
Get clearance for pushback

During pushback:

"Before engine start" checklist
Set bleeds / packs for engine start
Communicate with ground crew for engine start

Now you can start an engine. Unlike a small airplane where you start the engine by turning a key in an ignition switch, in bigger airplanes its a series of knobs and buttons to press, sometimes dependent on certain events during the start. Engine parameters must also be monitored in case an abort becomes necessary.

At this point you can get a taxi clearance and start moving toward the runway. You'll go through a couple more checklists, "after start/taxi" and "before departure", to prepare the plane for taxi and takeoff. Once you are on the runway, with all checks completed, with more fuel than your minimum dispatch release, and an ATC clearance you may then release the brakes and go flying. One pilot will fly and the other will monitor instruments.

Much of the above is beyond the typical scope of X-Plane, though some can be addressed with specific aircraft add-ons, manuals and software like VATSIM.

hey guys I just read through a whole set of comments posted there, I must say as a student pilot most of the things been said about xplane is not quite true, or further more I should say I don't know what version of xplane they are using or whether they are using a joy stick or the actual yoke and throttle controls be it multi or single and last but not least rudder pedals.
if you are using a joystick to fly just forget it no experience or sorta feel for real flight there.
After spending some time in a real aircraft flying it you gotta have some idea of what to look for when building your sim so you can translate what you see to a feel on your controls and try and get something from there. Also to get around, you gotta take the sim serious as you were or are in the real thing, what I am say is if you mess up there in a flight session, treat it as if you did it in the real thing.
I find xplane 11 very realistic just a few things are missing though, but where flight dynamics are concerned, with some of the default aircraft e.g the Beech Baron, the Cessna 172 and the piper turbo arrow (well that one is payware) they are not the most easy aircraft to fly and land if you don't have some sorta experience.
I think xplane can get you pretty close as to what to sorta expect in the real aircraft. Have you ever notice how the nose gets heavy as you just about setting up your flare and power adjustments as you are over the ground about to touch down? xplane simulates that pretty dam well, I must say I was surprised, it caught me a few times and the landing was really hard all 3 wheels bang on the ground etc in real flight that's problems.
So to the sim pilots or budding future pilots that out there I must say xplanes 11 is a really good way to go with a good set of controls to take you closer to reality


Which engine type requires the shortest take-off run: a turboprop or a turbofan? If two fixed-wing aircraft almost identical except for the engines, one turbofan and one turboprop, which one would need less runway to take off?

Even with similar weight, turboprop and turbofan aircraft will have different design characteristics. A turboprop will fly at lower altitudes and airspeeds, resulting in different aerodynamic designs. A turboprop also burns less fuel per hour, so it will need less fuel capacity.

That being said, we can look at some aircraft to get an idea of what the trends might be. The best example is probably the Dornier 328. It's a turboprop aircraft that seats about 30 passengers. There also happens to be a version of the plane with jet engines. This is probably about as similar as you can get in both weight and aerodynamics. According to Skybrary, the figures are as follows:

Dornier 328
MTOW 13990 kg
Distance 1000 m

Dornier 328JET
MTOW 15200 kg
Distance 1382 m

You can see the the jet derivative is a bit heavier but requires a much longer takeoff distance.

The trend is similar between other aircraft.

Dash 8-300 Turboprop
MTOW 18600 kg
Distance 1085 m

ERJ-135 Jet
MTOW 20000 kg
Distance 1580 m

CRJ-200 Jet
MTOW 21523 kg
Distance 1527 m

For two identical airframes, one turbofan powered and the other powered by prop jets, it's going to be a matter of the total available thrust from each as we as the thrust to weight ratio of each engine installation.  The lighter the engine / propeller and the greater the thrust, the shorter the takeoff roll will be by Newton's Laws

F = m*a

Here, the total force propelling the aircraft forward is the engine thrust force Fe subtracted from the sum of the Aerodynamic drag forces and wheel friction.

F = Fe - Da - Df

So a becomes

a = (Fe - Da - Df)/m

And the time of takeoff roll from standing start using basic kinematics.

Vr = a*t

And the total ground roll as

L = 0.5*a*t^2

In the real world, jets are designed for different cruise and mission profiles than turbopropeller aircraft, which requires the use of different airfoils and wing planforms.  Typically swept wing aircraft have higher stall speeds and consequently higher Vr than do rectangular or tapered planforms usually found on turbopropeller aircraft.

The comm nets made about the section from Aerodynamics for Naval Aviators are interesting.  This effect would be most noticeable on a fixed pitch propeller but minimized with a proper constant speed propeller which can keep propeller efficiency around the theoretical maximum of 85%-88%.

One advantage which a turboprop will have - at least for a tractor configuration - is that the prop wash over the wings creates additional lift, which can reduce Vr.  Propwas over the tailplane can provide additional elevator authority as well, reducing the takeoff roll here.


Is there a preferred turn direction for helicopters? If I have a requirement to fly a helicopter in a circle or racetrack over a point of interest that's stationary or moving relatively slowly, is there any reason to prefer left or right turns?

I'm not concerned about visibility and I'm not asking about turns in a landing pattern: I'm asking if - all other things being equal - there's any mechanical, aerodynamic or procedural reason that pilots would prefer to turn in one direction over the other.

Most helis make CW turns because the pilots sit on the right and it is easier to judge position and drift when you can look out the window directly.  Turning CCW is no problem however but it takes a tad more concentration.

one drawback of CW turns from the right seat is that the ALT and ASI would be out of your field of vision, so you'll have some head turning to peek at them. In a CCW turn, its easy to glance at the instruments in the center console.

I have seen turns in both directions. It probably does not matter anyways which way the turn is going, but if it is a single main-rotor helicopter, going with the counter-rotor spin is probably a little more effective at saving fuel although there is not much overall advantage either way if you are not looking for visibility.


What are design or functional differences between sticks and yokes? I've been flying Cessna 172 & 182's my whole flying life up to this point.  I know that Cirruses (Cirri?) have a "side yoke" and Diamonds, Citabrias and others have control sticks coming up through the seat.

Is this a design difference or are there actual functional differences between airplanes that have control yokes (like Cessna 182's) or sticks (like Diamonds) or side yokes (like Cirrus)?

For example, I realize that with the side yoke offers more legroom perhaps, but are there reasons beyond that - like pull/push force required?

There is some link between the type of control and the design maneuverability of the aircraft.

Consider a yoke.  Imagine twisting it to bank.  You are moving it with a twisting motion of one or both arms and in general, aircraft fitted with such yokes are capable of low to moderate roll rates.  Big displacements are uncommon but small, rapid, alternating changes are common.  Watch a wide body PF making control movements during a landing with any kind of xwind or turbulence.  They are less sensitive and give more visual feedback as to the control positions.

Now consider a stick, central to the pilot flying.  This is moved with a movement of the arm, generally only one, and can be rapidly displaced easily.  This is normally associated with aircraft with high rates of roll, especially in an aircraft designed to rapidly null out or reverse the roll.   It is also physically easier to move a stick than a yoke under high-G as the arm movement gives a longer lever.

A great example of this was the Vulcan which, despite its size, enormous wing area and large fin, was so rollable that it could out-maneuver the interceptors of its day.  It has a control column rather than a yoke and the PF would throw it around at altitude as if it were a fighter.  This would not be easy to do with a yoke.

I'm a bit long in the tooth and haven't flown fixed wing for many years.  I am not familiar with the rationale behind side sticks which are fitted to both low and high performance aircraft.  I am guessing they are fitted more for reasons of ergonomics than for performance.

I think you will not find side yokes (side sticks) on older aircraft that have purely mechanical connections to the control surfaces.  Sometimes they require both pilot and copilot to shove on the controls to get the desired result.  Look at how robust the controls are on a DC-3 for example.

Other than the force required, it is merely a design issue.  Potato, Potatoe.


What is the maximum angle F-16 can turn in x seconds flying at corner speed? How can one calculate the maximum turning angle F-16 can turn in x second flying at corner speed. Is it changed with height or weight?

To calculate this, you need to look at the energy Maneuver diagram for the aircraft. This diagram depicts, for a specified altitude and gross weight, the excess power per unit pound of weight the aircraft would have at full afterburner at any g-Loading and true airspeed. There would be a different chart for each aircraft configuration, gross weight and Density Altitude combination.

Instantaneous Turn rate is depicted on the vertical scale, true airspeed or mach number is depicted on the horizontal scale. The concave curved lines that go from upper left to far right represent flight conditions of constant G-loading, while the straight lines that radiate from the origin represent constant turn radius. The peak of the flight envelope, (at about Mach 0.7, 20 deg/sec turn rate and 8 Gs, is corner velocity. The lines that start at the left boundary or at the bottom, go upwards, curve to the right and then back down again, and are labeled with values 600, 400, 300, 0, -200, etc. are called Ps, (pronounced P-sub-S), lines. They depict the specific power, or actually, specific excess power - a measure of how much power per pound of aircraft weight the aircraft would have left over to climb or accelerate at the depicted point on the diagram.
So at the top of the diagram, at the corner velocity, where the turn rate is near 20 deg/sec, the specific excess power is less than -800. The -800+ Ps curve indicates that the aircraft, if it established flight at those conditions, would be bleeding energy (airspeed or altitude) at a rate in excess of negative 800 ft/sec.

The best performance on the diagram that can be sustained, on the other hand, is the highest point on the zero Ps line, which is at mach 0.8, 7 Gs, and it would produce a sustained turn rate of just over 14 deg/sec.

So, in a level turn, at Mach 0.8, 7 Gs, and 14 deg/sec, the F-16 could turn 180 degrees in about 13 secs.

Of course, if the aircraft performs the turn in a descent, it can make the turn in less time. This is indeed a common training maneuver, to turn 180 degrees in the shortest amount of time possible. It is performed by rolling into 135 degrees of bank at or slightly above corner velocity and pulling at maximum G-load. The maneuver is performed at maximum available G-load, in a constant plane tilted at 45 degrees from the horizontal. Bank angle (starting at 135 degrees), decreases throughout the maneuver, reaching 90 degrees bank after 90 degrees of turn, and 45 degrees bank at the end of the maneuver (after 180 degrees of turn). At 15,000 feet MSL, this will generate almost 20 degrees per second, and can be done in about 10 seconds.

The AOA  is 15 degrees and pulling 9G for making the maximum performance turn in level turns  in F16. ( 22 degrees /sec)


In what way are the Concorde's engines considered efficient? The Concorde is powered by a bunch of Rolls-Royce/Snecma Olympus 593 turbojet engines. Much has been said about how efficient they are at speed, and the fact that they allow long-range cruise at Mach 2 because of how fuel-efficient they are.

If I look at the specifications, one thing immediately obvious is the compression ratio of 15.5 - quite high for a no-bypass turbojet. I'm not sure how this translates into efficiency though.

The thrust-specific fuel consumption, on the other hand, looks dismal. Wikipedia states:

  1.195 lb/(lbf·h) (33.8 g/(kN·s)) cruise / 1.39 lb/(lbf·h) (39 g/(kN·s)) sl

Wait, what? The Tumansky R-25, which powered the MiG-21 and was famously fuel-hungry, had a compression ratio of only 9.5, but had a TSFC of

  98 kg/(h·kN) (0.96 lb/(h·lbf)) at maximum military power

The General Electric YJ93, which powered the XB-70 and was also designed for long-range supersonic efficiency, had a TSFC of

  0.700 lb/(lbf·h) or 19.8 g/(kN·s)

This doesn't seem to make sense: in what way are Concorde's engines any good? Is there something I'm missing?

Finally, I've been attempting to model the Olympus 593 in a flight simulator (Advanced Jet Engine in KSP). With the given compression ratio, though, I couldn't get the fuel efficiency to be this bad: it was around 0.9 SL and 0.85 cruise, and I had to do ridiculous things like using extremely inefficient intakes and nozzles.

You compare SFCs at different speeds. That is like comparing payloads for differently sized aircraft. SFC goes up with speed and, therefore, must be compared at the same speed. The work performed by an engine is thrust times distance, and higher speed means that the same thrust will perform more work per unit of time when the engine moves faster. The moving engine needs to slow down the airflow for combustion to take place, and then needs to accelerate the air by more than it has been slowed down to have positive thrust. Hence, SFC goes up in parallel with speed.

To have a meaningful comparison, we need to define efficiency. There are several, and two are of major importance for air-breathing aircraft engines: Thermal efficiency and propulsive efficiency.

Thermal efficiency

This describes how efficiently the chemical energy in the fuel $Q$ is converted into an impulse change of the air flowing through the engine. Formulated using the mass flow per unit of time $\dot{m}$, the impulse is $\dot{m}\cdot\dfrac{\Delta v^2}{2}$. Using $v_{\infty}$ for the incoming air speed and $v_{\infty} + \Delta v$ for the exit flow speed, the thermal efficiency is $$\eta_{therm} = \frac{\dot{m}\cdot \left((v_{\infty} + \Delta v)^2 - v_{\infty}^2\right)}{2\cdot Q}$$
To achieve good efficiency at high speed, a high $\Delta v$ is helpful. This explains why efficiency drops more over speed for high-bypass ratio engines and especially propellers.
Since the thermal energy in fuel is the same for all engines in your question, because all run on kerosene, and we can assume a similar efficiency of combustion, we can neglect $Q$ in the comparison.

Propulsive efficiency

This describes how well the conversion is performed. Using the same variables as above, propulsive efficiency is $$\eta_{prop} = \frac{v_{\infty}}{v_{\infty} + \frac{\Delta v}{2}}$$

This equation explains the better efficiency of high-bypass ratio engines and propellers at the same speed, because propulsive efficiency is proportional to the inverse of $\Delta v$.

Overall efficiency

This is the product of thermal and propulsive efficiency, and the equation is $$\eta_{total} = \frac{T\cdot v_{\infty}}{Q}$$
where $T = \dot{m}\cdot\Delta v$ denotes the thrust. Conveniently, $\Delta v$ is eliminated in the product, allowing turbojet engines like the Olympus 593 to look much better in comparison to other engines.

Intake efficiency

This answer would be incomplete without a look at the intake of the Concorde. At cruise, it would lift the pressure of the air at the compressor face by a factor of more than six over ambient by efficiently decelerating the flow. The compressor added a compression ratio of 12, so the pressure in the combustion chamber was 80 times higher than ambient. This high pressure makes the engine so efficient, but is also needed to maintain combustion. Remember, ambient pressure in 18 km is just 76 mbar, so the absolute pressure in the combustion chamber at cruise was only 6 bar.

The full answer would be like this: The combination of intake and Olympus 593 at Mach 2.02 had a very good total efficiency, and comparisons with other engines at static conditions are misleading.

The comparison of results from a test stand on the ground would yield a very different picture, however.

I don't think it was the engines alone that allowed supercruise (supersonic cruise without reheat). On Concorde, the engines engaged reheat in order to accelerate in level flight from subsonic to supersonic. One of the main reasons why Concorde had so much more range than the TU144 (which had to stay in reheat to stay supersonic), is the design of the wing. The Concorde wing evolved into a more complex shape during its development (I think between the first prototype and the production Concordes) specifically for this reason. If you look at the Concorde from the front the wing tips kind of sweep downwards. See http://www.concordesst.com/wing.html for more information. Even the great Kelly Johnson didn't do it this way for the SR-71, which stays in reheat the entire time it is supersonic.


Can a commercial cargo aircraft be converted into a commercial passenger aircraft, and vice versa? Just saw a video in a news, a military cargo plane carrying people stranded in some country. The seats were like in a commercial airliner. This led me to ask the question.

Would it be possible to see some examples where it was done, along with the procedure?

There are such a thing as "Quick Change" aircraft, allowing entire 'pallets' of chairs to be exchanged for cargo.

Image courtesy of canalblog.com

Image courtesy of airliner.net

Nice film to show the process.

Military transport aircraft can also be fitted out with stretchers or seats, or whatever other combo of stuff you want. To the best of my understanding these lock in like any other cargo pallet in the floor. They are less concerned with aesthetics and more with practicality:

Image courtesy the DOD via Wikimedia

Image courtesy of aarcorp.com

Yes. But with any modifications, the airplane will need to get re-certified by the authorities (FAA in the US) and approved, because it would have sustained modification to its structure.


Why do airports have to close in bad weather? Shouldn't aircraft be able to withstand winds of up to 100 mph? When flying the wind is at a much higher speed than that.
Shouldn't they be able to take-off through fog using instruments alone?
Shouldn't they be able to take-off on a slippery runway, since the wheels are not powered.

Wind

The problem with wind is that it can be from any direction, not necessarily the direction of the runway. When the wind is coming from the side instead of straight ahead, it is called a crosswind. This means that landing aircraft have to point into the wind to remain lined up with the runway. The slower they are flying, the further to the side they must point the nose. Airliners are designed to land in these conditions, but it requires more skill to do it well. The control inputs required to compensate for a crosswind affect aircraft on takeoff as well, as then must work harder to stay lined up with the runway and stay level through lifting off. High winds tend to come along with gusts, which makes it even harder to control an aircraft. Aircraft during flight are flying faster, so changes in wind are less problematic. Once they are flying slower, the wind is much larger compared to the aircraft's speed, and control is much more critical during landing. Aircraft have crosswind limits, and even below those limits, aircraft may need to go around from a landing attempt, which introduces delays.

Another issue is wind shear, which is when the direction and/or speed of the wind quickly changes. A change of 40 knots at higher speeds is turbulence. During landing or takeoff, it can cause the aircraft to stall and crash.

Visibility

Aircraft can certainly use systems like ILS that allow them to take off or land in low visibility. However, there are many limitations with these systems. The crew must be trained to use them, the aircraft must be equipped to use them, and the airport must be equipped with them. However, when the pilots are relying on instruments, they no longer are able to see hazards like usual. Because of this, separation requirements are inreased in these conditions, which means an airport can't handle as much traffic.

Water

It's true that aircraft wheels are not directly powered. However, traction is still very important during braking, since aircraft can hydroplane just like a car can. This means aircraft need more distance to stop, and can slide off the runway if they lose traction. Frozen water in the form of ice or snow makes a plane even more difficult to steer or stop.

Combine all of the above (a typical storm that would cause delays at an airport), and you can see why airports delay flights or close when conditions get worse.

All of these questions answer from the point of view of the plane. Can it land, can it take off, can the pilots see, can they control the plane, etc. But there is another aspect not yet mentioned: ground staff.

It's incredibly common for long delays to be caused by thunderstorms because it's not safe for anyone to be outside during active lightning. This means the people who hold the sticks to show the planes where to park, the people who hook up the fuel trucks, the luggage handlers - dozens of people many of whom are handling dangerous equipment, and all of whom have to stay inside until the lightning stops. An airport may stop allowing landings and takeoffs even when the planes would have no trouble landing or taking off because it's not safe for ground crew to be out there.


Can an aircraft be turned without rudder input? Is it possible for pilots to make a right or left turn, using just the ailerons and without rudder input in all airliners? If not why so, for what reason?

It depends on the aspect ratio of the wing and the lift coefficient. Short, stubby wings at low angle of attack will not create much adverse yaw with aileron input, especially when the ailerons have differential linkage (more deflection on the trailing-edge-up side and less on the opposite side). Differential gearing is also beneficial in reducing stick forces, so many small aircraft with manual controls employ it. Therefore, turning with ailerons alone is possible with low aspect ratio wings.

Airliner wings have aspect ratios between 7 and 11, so here it is helpful to reduce the lift coefficient by flying fast and lower than at maximum cruise altitude if you want to turn with the ailerons alone. If you allow rudder movements but just want the pilot to rest his/her feet on the floor: Almost all jets have yaw dampers, that is a device which will deflect the rudder automatically such that yaw is minimized. Therefore, airliners can be flown with the feet off the pedals and still ailerons and rudder will keep the plane in a coordinated turn.

With gliders and their high aspect ratio wings, however, using only ailerons will mostly yaw the aircraft, especially at low speed when the lift coefficient is high. The wing also has high roll damping from its high aspect ratio and low flight altitude, so the roll angle achievable before yaw becomes dominant is small. The yawing condition will now create its own rolling moment due to the dihedral effect of the wing. Unfortunately, this effect counters the intended rolling motion and prevents the aircraft from turning with ailerons alone. If adverse yaw is large enough, the aircraft will not even begin to roll but will only yaw with aileron input.  Some glider pilots even apply cross controls when entering a thermal in order to maximize their rolling speed (rudder into the turn and aileron against to provoke more yaw and let the dihedral effect roll the glider).

If you find yourself in a high-performance glider with a jammed rudder, speed up in order to fly turns with the ailerons (and elevator) only. The lower lift coefficient will reduce adverse yaw so direction can be controlled with ailerons and elevator only.

Of course! Neither the rudder, not the ailerons, actually turn the aircraft. It is LIFT that turns the aircraft. It "turns" the aircraft in the direction that the Lift vector (perpendicular to the wings) is pointed in.
So to turn, you need to point the Lift vector in the direction you wish to turn, (roll into a bank) and apply some Lift (Pull back on the stick/yoke).

To turn up (increase pitch attitude) leave the aircraft in zero bank angle, and pull on the yoke. To turn left , place the aircraft in a left bank, and pull on the yoke, etc.

To roll into a bank in a coordinated manner, you generally need both ailerons and rudder, but if you're not picky about being uncoordinated,  you can roll into a bank with either one.


Would a stationary WWII fighter fall on its nose with full throttle and brakes on? Would a stationary WWII fighter fall on its nose with full throttle and brakes on?

It's a general question, but I am interested in the Republic P-47.

(Wikimedia; arrows and CG icon are my additions) P-47 side drawing.

The thrust has a bigger moment arm around the tires contact points compared to the weight. It won't nose over below a certain RPM (it will be specified in the training). Below that RPM:

The weight will counter the thrust
The propeller downwash will produce downward force on the horizontal stabilizer
Applied brakes will resist the rotation of the wheels (airframe rotating around wheels)

From a training video for the comparable big-engined F6F Hellcat, the narrator says:

  You can't gun this engine to full takeoff RPM and manifold pressure while holding the plane with the brakes, if you exceed 2,000 RPM the tail will lift and you risk nosing over.

Answer is yes it can happen.

Note: for comparison, the max RPM is 2,700 for the Hellcat.

It depends on what position the elevator is in! As long as there's enough back pressure, there's not going to be an issue. If you were to push FORWARD, then the plane would go over onto its nose. I've got some experience with this in X-Plane, and it's definitely possible. If I was involved in a similar engine run-up, I'd want some sort of tie-down on the tail if the plane was to remain stationary, to avoid the possibility of the pilot bumping the stick and shoving the plane over.


Can an aerodrome in class G airspace be controlled? Can an aerodrome be controlled, even if the only associated airspace is classified G?

E.g. can such an aerodrome have a control tower with the authority to give takeoff and landing clearances and taxi instructions?

I know the opposite is possible (uncontrolled aerodromes in class D airspace for example).

I am not asking about AFIS aerodromes, since AFIS is not an air traffic control service.

Please provide examples and/or references to ICAO SARPs or national regulations.

An airport in class G airspace can have an operating control tower. This is a case of a towered airport in uncontrolled airspace. The airspace is uncontrolled but tower communication must be established within a certain distance and for use of the airports runways.

There are applicable regulations that address this situation. 14 CFR §91.126 (d) requires pilots to establish and maintain communication with a Class G towered airport before entering a 4 NM radius below 2500 AGL.

As of today, Lake City, Florida (KLCQ) is an example of such an airport, although that will change at some point in the future.

No.  By definition, Class G airspace is uncontrolled.  The airport would have to be in a minimum of Class D airspace for it to be controlled.


Can I log instrument flight time for currency purposes in an Advanced Aviation Training Device (AATD)? Advisory Circular AC 61-136 which outlines the approval and limitations of flight training devices seems to contradict 14 CFR 61.57(c).

To what extent can I use an AATD for instrument currency? In addition, to what extent can an AATD be used toward and instrument proficiency check (IPC)?

Edit:

I have located this document from the FAA Office of Aviation Safety that clarifies that AATDs and BATDs are governed by FAR 61.4(c) and are authorized for specific purposes and can be used in the same manner at a Flight Training Device instead of a Aviation Training Device as long as they have an approve Letter of Agreement (LOA) from the administrator.

This leads me to believe that an AATD qualifies for FAR 61.57(c)(2) not FAR 61.57(c)(3).

From what I can tell, the Advisory Circular is outdated. It was issued July 14, 2008, while the most recent update to 14 CFR 61.57 was effective Nov 15, 2013.
When the AC was issued, 61.57(c) did not contain the wording specific to Aviation Training Devices (effective 11/17/2003). That language was added in the version effective 10/20/2009, and the AC apparently has not been revised since that point.
At this point the regulations are more specific (and regulatory) than the Advisory Circular. You should be able to log recent flight instrument experience in a ATD based on 61.57(c)(3), or the subsequent subsections that pertain to mixed currency.

(3) Use of an aviation training device for maintaining instrument experience. Within the 2 calendar months preceding the month of the flight, that person performed and logged at least the following tasks, iterations, and time [emphasis mine] in an aviation training device and has performed the following--

(i) Three hours of instrument experience.
(ii) Holding procedures and tasks.
(iii) Six instrument approaches.
(iv) Two unusual attitude recoveries while in a descending, Vne airspeed condition and two unusual attitude recoveries while in an ascending, stall speed condition.
(v) Interception and tracking courses through the use of navigational electronic systems.

I wrote this back in 2014 following a briefing on a Cardinal accident where two people perished on approach to CYOW (Ottawa). I should have posted it here back then.

At an IFR Club meeting on 27 Feb 2014 involving the accident of C-FEFQ, the issue of improperly logging “instrument time” for IFR recency was highlighted. I believe that commercial pilots, cruising along in VMC in Class A airspace where operations are IFR, log all their flight time as “instrument time” even when they are on autopilot and not actually operating the aircraft.  This is probably why many GA IFR pilots log their IFR time (in VMC) as “instrument time” as well.  Unfortunately, based on the Canadian CARs, GA IFR Pilots cruising along in VMC at 5000’ on an IFR flight plan cannot log their flight time as “instrument time” unless it is either actual flight instrument time, simulated flight instrument time or ground instrument time.  There seems to be a problem of interpretation in logging “instrument time” that no one wants to address. There is even a problem with the term "IFR Time" itself, which isn't your Flight Time. IFR Time really means your time in the IFR system. You could be in VMC for quite awhile before getting your clearance, then have your IFR clearance cancelled well before arriving at your destination. Your IFR Time would be less than your Air Time, an you never even see a cloud!

I believe this issue of logging “instrument time” has been debated for years and years (and years!) with lots of interpretations based on FARs Section §61.51- Pilot logbooks and §61.57- Recent flight experience: Pilot in command, as well as CARs Part IV - Personnel Licensing and Training, Section 401.05(3) - Recency Requirements and Section 401.08- Personal Logs.

Here is how I would recommend logging your “instrument time” for recency. In each situation you must be operating the aircraft or approved simulator solely by reference to the flight instruments:

Actual Flight instrument time

This is your time spent in cloud, smoke, fog, haze, mist or dark night conditions when you don’t have any horizon or lights for visual reference to the ground during an actual flight in non-VFR conditions.
If you are in these non-VFR conditions, you will obviously have to be on an IFR Flight Plan to be legal.
If you are in non-VFR conditions for the entire flight you can only take credit for up to the maximum Air Time ( up – down), not the entire Flight Time. You are not flying solely on instruments while taxiing.

Simulated Flight instrument time

This is your time spent simulating cloud, smoke, fog, haze, mist or dark night without an horizon or without visual reference to the ground during an actual flight and in VFR conditions.
You are expected to have a safety pilot with you and to use a view limiting device or hood in order to get credit for logging this simulated flight instrument time.
The safety pilot will also be your instructor when you are conducting IFR training in order to get credit for logging this simulated flight instrument time. You are allowed to log it, and your instructor (PIC) is also allowed to log it.
You can only take credit for the time that you are simulating instrument conditions. This may be less than the Air Time depending upon when you start and stop flying by sole reference to the flight instruments.

Ground instrument time

This is your time spent simulating non-VFR conditions on a simulated IFR flight in an approved flight simulator.
An instructor is expected to be with you when you are conducting IFR training in order to get credit for this ground instrument time, but if you are an IFR rated pilot you don’t need an instructor. You can be alone or with another pilot.
If you are in non-VFR conditions for the entire flight you can only take credit for up to the maximum simulator Air Time (up – down), not the total simulator Flight Time as the simulator could be paused during the simulated flight.

These are suggested guidelines or best practices for estimating and logging “instrument time” that anyone should be able to follow to meet the 6 hours and 6 approaches in 6 months rule. There are differences between US and Canadian IFR recency requirements also creates more confusion. Even approved training devices are described differently so this discussion could continue endlessly.

My conclusion is that logging “instrument time” is based on your good judgement to determine if the flight was under instrument flight conditions. It is also based on the honour system for reporting your time. Please feel free to disagree with my interpretations and discuss as needed. I hope that a “standard” interpretation will eventually be achieved through consensus.


Forces in a slipping turn I have trouble understanding why the ball (on the turn & slip indicator) falls into the turn e.g. drop to the left when aircraft is rolled left, when in an uncoordinated turn (slipping turn). What are the forces that goes into this?

From reading up online, many sources quote that in a slipping turn, the aircraft is banked too much for the rate of turn. So, the horizontal lift component is greater than centrifugal force. As a result, the ball drops into the turn since there is less g force to "centralise" the ball.

Isn't centrifugal force suppose to be equal and opposite of the horizontal component of lift. How can being in a slipping turn make the centrifugal force lesser? Essentially, what is so special about slipping turn can allow the centrifugal force to change?

Image from: http://avstop.com/ac/flighttrainghandbook/forcesinturns.html

I have trouble understanding why the ball (on the turn & slip indicator) falls into the turn ... in an uncoordinated turn (slipping
  turn). What are the forces that goes into this?

The ball is displaced to one side because the aircraft is being allowed to fly sideways through the air.  The nose is not aligned with the instantaneous direction of the flight path, but rather is yawed to point to the left or right of the instantaneous direction of the flight path.

As a result, the airflow is striking the side of the aircraft and generating an aerodynamic sideforce, which is what causes the ball to displace to the side.

There are many reasons why an aircraft might tend to fly yawed slightly toward the left or the right in a turn.  Most of these reasons tend to promote a slip, rather than a skid.  Other than the most obvious reason of a significant, intentional deflection of the rudder by the pilot, these reasons include the curving nature of the relative wind during turning flight and its effects on tail surfaces (also described as "aerodynamic damping"), and the fact that the outboard wingtip must move faster, and thus tends to generate more drag, than the inboard wingtip.  In an aircraft with a propeller, P-factor can also play a role, tending to promote either a slip or a skid depending on the direction of turn.  The setting of the rudder trim may also be factor.  When the bank angle is changing, adverse yaw from the deflected ailerons and from the rolling motion itself plays a major role, strongly tending to promote a slip when the bank angle is increasing and a skid when the bank angle is decreasing.  In all cases, the cure is for the pilot to use the rudder as needed to compensate for these effects and align the nose of the aircraft with the instantanous direction of the flight path, so the nose is pointing straight into the "relative wind" and the airflow is not hitting the side of the fuselage.

Note that "having too little or too much lift in relation to the bank angle" or "having too little or too much centrifugal force in relation to the bank angle" are not causes of slips or skids.  Rather, they are results of slips or skids.  The causes are the aerodynamic effects listed above, creating a yaw torque that makes the aircraft fly slightly sideways through the air, despite the generally stabilizing effect of the vertical fin.  More on this later.

So why does the slip-skid ball get displaced off center when the aircraft flies sideways through the air?  When the airflow hits the side of the fuselage, this generates an aerodynamic sideforce, acting orthogonal (perpendicular) to the flight path in the direction that is roughly parallel to the wingspan,  This sideforce points toward the high wingtip in a slip, and toward the low wingtip in a skid.  This real aerodynamic force has been completely omitted from the diagram of the slipping turn attached to your question.  This is a major flaw in the diagram.

This aerodynamic sideforce contributes to the net aerodynamic force generated by the aircraft, so that the net aerodynamic force vector is no longer pointing
straight up" in the aircraft's reference frame, i.e. parallel to the vertical fin.

The slip-skid ball always tends to position itself in the curved glass tube at the point in the tube that is exactly perpendicular to the net aerodynamic force vector.  If the ball is positioned at any other point in the tube, it will "feel" an apparent force to the left or right, and will shift position.  If the net aerodynamic force is not pointing "straight up" in the aircraft's reference frame, then the ball will not position itself at the "bottom", i.e. at the center, of the curved glass tube.

Another way to look at the situation is to consider the apparent "load" acting on the ball, due to the combined effect of weight and "centrifugal force".  The ball always tends to position itself in the curved glass tube at the point in the tube that is exactly perpendicular to the "load" vector.  If the "load" vector is not pointing "straight down" in the aircraft's reference frame, then the ball will not position itself at the "bottom", i.e. at the center, of the curved glass tube.

The key thing to understand is that the apparent "load" felt by the aircraft structure and contents, including the pilot and the slip-skid ball, is nothing more than the mirror image of the real aerodynamic force vector generated by the aircraft.  This is explored in more detail in a several answers to the related ASE question "Forces "felt" by pilot, G-meter, inclinometer--are they the aerodynamic forces generated by the aircraft, or the sum of weight+centrifugal force?".

The diagram is misleading because it suggests that some mysterious effect, presumably somehow related to turn rate, yet seemingly unrelated to any real aerodynamic force, is affecting the amount of "centrifugal force" generated by the aircraft or acting on the aircraft.  This is false.  The difference in the magnitude of the "centrifugal force" vector between a "coordinated" turn and a "slipping" turn is due to the way that a sideslip generates a real aerodynamic sideforce vector, as described above.

While it is in fact true that the "load" acting on the ball can be said to be equal to the vector sum of weight and "centrifugal force", this is not a concept that has a lot of explanatory power, unless we understand that the "centrifugal force" is intimately related to the real aerodynamic forces generated by the aircraft.  The "load" vector, which can be said to be the vector sum of weight and "centrifugal force", is nothing more than the mirror image of the real aerodynamic force generated by the aircraft.  The "load" vector is always equal and opposite to the vector representing the real aerodynamic force generated by the aircraft.1

An extreme case of a slipping turn is a forward slip or sideslip (these are actually exactly the same thing, just aimed differently in relation to the target), where the aerodynamic sideforce from the slip is sufficient to bring the turn rate all the way to zero, creating a linear flight path.  Whenever the flight path is linear, the slip-skid ball doubles as bank angle gauge.  The most extreme case of a non-turning (linear) sideslip is vertically-banked sustained knife-edge flight, like we often see at an airshow.  In this case the aerodynamic sideforce vector from the airflow striking the side of the fuselage (plus an additional component due to the engine thrust line being aimed above the horizon) is supporting the entire weight of the aircraft, and the wing's lift vector is zero.  In this case, the "load" vector is simply equal and opposite the aerodynamic sideforce vector from the slip (including the component due the engine thrust), because aerodynamic sideforce vector and the net aerodynamic force vector are one and the same.  The net aerodynamic force vector is equal to the weight of the aircraft but acting in the upward direction, while the "load" vector is equal to weight of the aircraft, acting in the downward direction.

While established in a steady-state turn at a constant turn rate and airspeed, trimmed for hands-off flight, if we then pull aft on the stick to "load up" the wing with "extra" lift to boost the G-load to a higher-than-normal value for the bank angle, or if we push the stick forward to "unload" the wing to decrease the lift vector and drop the G-load to a lower-than-normal value for the bank angle, the turn rate will immediately change, and so will the horizontal component of the "centrifugal force" vector.  The diagram above might tend to lead us to think that the ball will immediately shift off-center.  This is not the case.

In a situation like this, the flight path will curve up or down, introducing a vertical component of "centrifugal force".  The vector sum of weight and centrifugal force will still be "straight down" in the aircraft's reference frame, and the ball will stay centered.

Or to look at it from a much simpler perspective-- when we pull the stick aft or push the stick forward to change the wing's angle-of-attack, we are increasing or decreasing the magnitude of the lift vector, but we aren't introducing any aerodynamic sideforces-- we aren't yawing the fuselage to fly sideways through the air.  Because the net aerodynamic force vector still acts "straight up" in the aircraft's own reference frame-- parallel to the direction that the vertical fin is pointing-- the ball still stays centered.

(For simplicity, we're ignoring the forward or aft components in the net aerodynamic force vector-- the components that wouldn't show up in a head-on view of the aircraft.  The basic explanation here remains the same regardless of whether thrust is exactly in balance with drag, or not.)

Of course, "loading" or "unloading" the wing in this manner during a turn will also drive a change in airspeed, as the flight path curves up or down.  For an aircraft of a given weight at a given bank angle, there is only one value of the lift vector (G-loading) that will yield a steady-state turn at constant airspeed.2

  From reading up online, many sources quote that in a slipping turn, the aircraft is banked too much for the rate of turn.

From the content above, you'll see that this isn't always true.  It can be true given certain constraints, but it is not a concept with a lot of explanatory power.

As noted above, if we are established in a stabilized turn, and then we pull the stick back, or push the stick forward, to boost or decrease the lift vector and G-loading, the turn rate immediately changes, but the ball does not shift off-center.3

The idea that (for a turn at a given airspeed) "in a slipping turn, the aircraft is banked too much for the rate of turn" is only true given the constraint that there is zero upward or downward (skyward or earthward) curvature in the flight path.  And the only way4 that (for a given airspeed) we can have a mismatch between the bank angle and turn rate, while not allowing the flight path to curve up and down, is that we are applying the rudder to expose the side of the fuselage to the airflow and generate an aerodynamic sideforce, or we are failing to apply the rudder as needed to cancel out other aerodynamic torques that are tending to expose the side of the fuselage to the airflow.  If we do this, while adding or subtracting power as needed, we can indeed create the following situations.  Starting from a stabilized coordinated turn at a constant airspeed and altitude, we can--

a) vary the turn rate and turn radius while holding altitude, airspeed, and bank angle constant

b) vary the bank angle and while holding altitude, airspeed, and turn rate and radius constant

The ball will deflect off center in both of these sitations.  It is equally true to say that the ball goes off-center because the centrifugal force vector is no longer correctly matched to the bank angle, or because the load vector (the vector sum of centrifugal force and weight) no longer points straight "down" in the aircraft's reference frame (i.e. parallel to the vertical fin), or because the net aerodynamic force vector no longer points straight "up" in the aircraft's reference frame (parallel to the vertical fin), or because the pilot is using the rudder in a way that exposes the side of the fuselage to the airflow, which generates an aerodynamic sideforce.

The pilot's rudder usage is the key to centering the slip-skid ball, or to intentionally driving it off center.  The sideways force we "feel" in a slip is the real aerodynamic force generated by the air striking the side of the fuselage, which changes the direction of the net aerodynamic force vector, and its mirror image, the "load" vector.  Explanations centered around some sort of "balance" or "imbalance" between bank angle and turn rate, or bank angle and lift force, or bank angle and G-loading, are misleading, and have little explanatory power, and certainly do not apply to aerobatic flight.  These explanations tend to obscure, rather than illuminate, what is really going on.

Some of these sorts of explanations are well suited to a car driving on banked track, or a bobsled going down a banked track, but not to flight, where the trajectory is not constrained to have a specific turn radius, and also is not constrained to have no upward or downward (skyward or earthward) curvature.5

Note that in flight, generally speaking, changing airspeed while holding the bank angle constant creates no tendency toward a slip or skid, though the turn rate and radius will both vary.  As long as the net aerodynamic force vector continues to point "straight up" in the aircraft's reference frame, there will be no slip or skid.  Though again, we can come up with specific contrived situations where varying the airspeed while holding the bank angle constant does cause a slip or skid-- for example if the turn rate and radius are constrained to remain constant as the airspeed is changed.  Again, this can only happen if the pilot applies the rudder to expose the side of the fuselage to the airflow, generating an aerodynamic sideforce.

  I have trouble understanding why

This is not surprising, because you have been provided with faulty explanations, as well as faulty diagrams.  The diagrams attached to your question have omitted the aerodynamic sideforce vector caused by the airflow striking the side of the fuselage.  The diagrams attached to your question give the impression that the net aerodynamic force vector generated by the aircraft is the same in all 3 cases (coordinated flight, slipping flight, and skidding flight), when it actually is not.  The diagrams attached to your question give the impression that the "load" vector can somehow be something other than the mirror image of the net aerodynamic force vector, when it actually cannot be anything other than the mirror image of the net aerodynamic force vector.

To read more about the specific errors in the vector diagrams attached to your question, see the related question What is missing from these diagrams of the forces in slips and skids? and answer What is missing from these diagrams of the forces in slips and skids? .

Other related ASE questions or answers:

(Q) Forces "felt" by pilot, G-meter, inclinometer--are they the aerodynamic forces generated by the aircraft, or the sum of weight+centrifugal force?

(A) Forces "felt" by pilot, G-meter, inclinometer--are they the aerodynamic forces generated by the aircraft, or the sum of weight+centrifugal force?

(Q) What does the balance ball actually indicate?

(A) What does the balance ball actually indicate?

The topic of accuracy of the diagrams illustrated in your question has also been discussed on Physics Stack Exchange.  See--

(Q) Is this vector diagram of the forces at play in turning flight correct?

(A) Is this vector diagram of the forces at play in turning flight correct?

Footnotes

1 -- For simplicity, we're assuming that the slip-skid ball is located near the aircraft's CG, or aircraft's yaw rotational rate is constant, or both.  A change in the yaw rotational rate will create an apparent centrifugal or inertial force that displaces the slip-skid ball to one side if it is located far forward or aft of the CG, and this displacement does not reflect any real aerodynamic force component.  For example, if the yaw rotational rate is increasing toward the left, a slip-skid ball located far in front of the CG would tend to be displaced toward the right, and a slip-skid ball located far aft of the CG would tend to be displaced toward the left.  These second-order effects are beyond the intended scope of this answer, and are also beyond the scope of what pilots are generally able to notice in actual flight.

2 -- For simplicity, we're overlooking the fact that magnitude of the lift vector associated with a steady-state coordinated turn at some particular bank angle and some particular airspeed and angle-of-attack is very slightly different when we are descending or climbing, than when we are maintaining altitude (with respect to the airmass in all cases).  For modest dives and climbs, this is a very minor effect and definitely not something that someone still learning about the basics of slips and skids should concern themselves with, but in the interest of accuracy, this point should not be completely omitted.  To learn more about the "unloading" of the lift vector in a descent or climb, see What produces thrust along the line of flight in a glider? and Does lift equal weight in a climb?

3 -- Surprisingly, Wolfgang Langewiesche's classic flight-mechanics-for-pilots book "Stick and Rudder" (1944), which contains a lot of good material on the physics of turning flight, does make the claim (see pages 205, 219-220, and 223-226) that while excess back pressure on the stick does not cause a slip or skid, too little back pressure on the stick can cause a slip, with the ball deflected to the low side of the turn, which should be corrected by increasing back pressure rather than by applying inside rudder.  This is probably the only faulty idea in the entire book.  The 3rd edition of the book "Modern Airmanship" (1966, edited by Neil Van Sickle, Major General USAF) has similar content on pages 308-309.  By the 8th (1999) edition of "Van Sickle’s Modern Airmanship", edited by John F. Welch, Lewis Bjork, and Linda Bjork, this content had been deleted, while the remaining content on the physics of turning flight had been retained (page 441).  For more, including specific quotes from these books, see https://web.archive.org/web/20180905112047/http://aeroexperiments.org/critiques.shtml .

4 -- Strictly speaking, it's not exactly true that the only way that (for a given airspeed) we can have a mismatch between the bank angle and turn rate, while not allowing the flight path to curve up and down, is to deflect the rudder to the side in a way that exposes the side of the fuselage to the airflow.  But it's a good first approximation.  For a more nuanced view, we have to consider the effect of the sideforce generated by the rudder itself.  For example, we could shut down one engine on a conventional piston twin and apply the rudder just enough to keep the fuselage exactly aligned with the airflow.  Since the sideforce from the rudder itself is not zero, the ball will be slightly deflected (toward the working engine) when the nose of the aircraft is pointing straight into the relative wind.  If we bank into the good engine as needed to cancel all turning tendency, we'll end up flying along in a straight line (zero turn rate) while banked slightly toward the good engine, as discussed in detail elsewhere on ASE, such as here, here, and here (link to be added).

5 -- Speaking of bobslebs on curved tracks, "Hang Gliding Training Manual" and "Performance Flying" by Dennis Pagen both include extensive content-- including an illustration of a bobsled on a track-- purporting to show how, as a pilot enters a turn while flying a hang glider, if he or she doesn't immediately "load up" the wing with an adequate pitch input, the glider will slip sideways through the air, toward the low wingtip.  Also the idea that an intentional reduction of angle-of-attack and lift and G-loading while turning will make the glider slip sideways through the air toward the low wingtip.  See for example pp. 128-129 in "Hang Gliding Training Manual", and page 45 in "Performance Flying".  A similar idea appears on page 70 of Peter Cheney's "Hang Gliding for Beginner Pilots" (3rd edition, 1997).  I've checked these ideas in flight with a yaw string, in hang gliders as well as conventional aircraft, and found no basis for them.  For more on the content in these books, see https://web.archive.org/web/20180905112047/http://aeroexperiments.org/critiques.shtml .

Because of the insufficient speed and pull for the bank angle of the aircraft  .For level  turn  you must pull up not bank  ,but first you need to bank some degrees and have enough speed to maintain the G required for the bank angle .If you pull lower than the needed G's for bank angle your aircraft nose will dive ,if you pull more G's the nose rise above horizontal line.Now there are two types of skidding turns (inside the turn or  drifting outside of  turn)


Can an aircraft owner legally replace an oil quick drain valve? The quick drain valve on our older Mooney has started leaking and making a bit of a mess.  We went to our local shop to asked them to schedule to replace it for us and they told us they are booked out several weeks and turning away any smaller jobs due to being understaffed -_-

I mentioned we do our own oil changes and he suggested that if we were handy enough to handle an oil change we could just remove the quick drain and replace it with an original plug and he was happy to give us one for free.  That would get us to our next oil change and we could get it replaced then.

Part 43 allows owners to do the oil changes and replacing the quick drain valve with a plug looks to be basically identical to the oil change process if you didn't have a quick drain valve in the first place: remove the plug, catch the oil, replace plug, add new oil.  But if I'm going to down that route anyway why not just grab a new quick drain off of aircraft spruce and put that in instead of the plug?

Are we on the right side of owner maintenance if we replace the quick drain with a plug as the A&P suggested?  How about if we replace the quick drain with a new one?  Or should we get a sign off from an A&P

This is what the FAR allows you to do as preventive maintenance if you are not a certified mechanic:

(c) Preventive maintenance. Preventive
maintenance is limited to the following
work, provided it does not involve complex
assembly operations:
(1) Removal, installation, and repair of
landing gear tires.
(2) Replacing elastic shock absorber cords
on landing gear.
(3) Servicing landing gear shock struts by
adding oil, air, or both.
(4) Servicing landing gear wheel bearings,
such as cleaning and greasing.
(5) Replacing defective safety wiring or
cotter keys.
(6) Lubrication not requiring disassembly
other than removal of nonstructural items
such as cover plates, cowlings, and fairings.
(7) Making simple fabric patches not requiring
rib stitching or the removal of structural
parts or control surfaces. In the case of
balloons, the making of small fabric repairs
to envelopes (as defined in, and in accordance
with, the balloon manufacturers’ instructions)
not requiring load tape repair or
replacement.
(8) Replenishing hydraulic fluid in the hydraulic
reservoir.
(9) Refinishing decorative coating of fuselage,
balloon baskets, wings tail group surfaces
(excluding balanced control surfaces),
fairings, cowlings, landing gear, cabin, or
cockpit interior when removal or disassembly
of any primary structure or operating
system is not required.
(10) Applying preservative or protective
material to components where no disassembly
of any primary structure or operating
system is involved and where such
coating is not prohibited or is not contrary
to good practices.
(11) Repairing upholstery and decorative
furnishings of the cabin, cockpit, or balloon
basket interior when the repairing does not
require disassembly of any primary structure
or operating system or interfere with an
operating system or affect the primary
structure of the aircraft.
(12) Making small simple repairs to fairings,
nonstructural cover plates, cowlings,
and small patches and reinforcements not
changing the contour so as to interfere with
proper air flow.
(13) Replacing side windows where that
work does not interfere with the structure or
any operating system such as controls, electrical
equipment, etc.
(14) Replacing safety belts.
(15) Replacing seats or seat parts with replacement
parts approved for the aircraft,
not involving disassembly of any primary
structure or operating system.
(16) Trouble shooting and repairing broken
circuits in landing light wiring circuits.
(17) Replacing bulbs, reflectors, and lenses
of position and landing lights.
(18) Replacing wheels and skis where no
weight and balance computation is involved.
removal of the propeller or disconnection of
flight controls.
(19) ...
(20) Replacing or cleaning spark plugs and
setting of spark plug gap clearance.
(21) Replacing any hose connection except
hydraulic connections.
(22) Replacing prefabricated fuel lines.
(23) Cleaning or replacing fuel and oil
strainers or filter elements.
(24) Replacing and servicing batteries.
(25) Cleaning of balloon burner pilot and
main nozzles in accordance with the balloon
manufacturer’s instructions.
(26) Replacement or adjustment of nonstructural
standard fasteners incidental to
operations.
(27) The interchange of balloon baskets and
burners on envelopes when the basket or
burner is designated as interchangeable in
the balloon type certificate data and the baskets
and burners are specifically designed for
quick removal and installation.
(28) The installations of anti-misfueling devices
to reduce the diameter of fuel tank
filler openings provided the specific device
has been made a part of the aircraft type
certificiate data by the aircraft manufacturer,
the aircraft manufacturer has provided
FAA-approved instructions for installation
of the specific device, and installation
does not involve the disassembly of the existing
tank filler opening.
(29) Removing, checking, and replacing
magnetic chip detectors.
(30) The inspection and maintenance tasks
prescribed and specifically identified as preventive
maintenance in a primary category
aircraft type certificate or supplemental
type certificate holder’s approved special inspection
and preventive maintenance program
when accomplished on a primary category
aircraft provided:
(i) They are performed by the holder of at
least a private pilot certificate issued under
part 61 who is the registered owner (including
co-owners) of the affected aircraft and
who holds a certificate of competency for the
affected aircraft (1) issued by a school approved
under § 147.21(e) of this chapter; (2)
issued by the holder of the production certificate
for that primary category aircraft
that has a special training program approved
under § 21.24 of this subchapter; or (3) issued
by another entity that has a course approved
by the Administrator; and
(ii) The inspections and maintenance tasks
are performed in accordance with instructions
contained by the special inspection and
preventive maintenance program approved
as part of the aircraft’s type design or supplemental
type design.
(31) Removing and replacing self-contained,
front instrument panel-mounted
navigation and communication devices that
employ tray-mounted connectors that connect
the unit when the unit is installed into
the instrument panel, (excluding automatic
flight control systems, transponders, and
microwave frequency distance measuring
equipment (DME)). The approved unit must
be designed to be readily and repeatedly removed
and replaced, and pertinent instructions
must be provided. Prior to the unit’s
intended use, and operational check must be
performed in accordance with the applicable
sections of part 91 of this chapter.
(32) Updating self-contained, front instrument
panel-mounted Air Traffic Control
(ATC) navigational software data bases (excluding
those of automatic flight control
systems, transponders, and microwave frequency
distance measuring equipment
(DME)) provided no disassembly of the unit
is required and pertinent instructions are
provided. Prior to the unit’s intended use, an
operational check must be performed in accordance
with applicable sections of part 91
of this chapter.

Short answer is YES.

Read FAR 43 Appendix A thoroughly and find (23) which says:

  (23) Cleaning or replacing fuel and oil strainers or filter elements.

A quick drain valve is considered an oil strainer.

Create a logbook entry and have a beer.