Does the pressure at the static ports drop as the aircraft's speed increases? This answer by Tyler Durden explains what static ports are and how they work:

  The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. They are called "static" ports because in general they take in air at the ambient pressure which does not change very much [...]

Currently, the answer has a comment by Zeiss Ikon which states:

  In fact, the pressure at the static ports will drop as the aircraft's speed increases (Bernoulli principle) [...]

Is this true? If I'm flying at a constant altitude, will the pressure at the static ports decrease as I speed up and increase as I slow down?

If so, does the altimeter have a mechanism for compensating for this?

The comment:

  In fact, the pressure at the static ports will drop as the aircraft's
  speed increases (Bernoulli principle)

is not exactly accurate. The aircraft is a complex aerodynamic shape and static pressure distribution across the fuselage is not linear. An example is provided by the following figure from NASA Technical Memorandum 104316:

[Source: NASA]

If you look at the graphical part of the above figure, you'll see areas where the pressure is above (>0) and below (<0) the reference pressure. As the airspeed increases, the tendency will be for the positive values to get bigger and the negative values to get lower (more negative). So along the line between points 2 and 3, and also between 4 and 5 (over the wing), the pressure will drop as speed increases. Between 1 and 2 (the nose), and between 3 and 4 (just in front of the wing), the pressures will rise with speed.

From the same report:

  Zero static pressure error on the fuselage exists at locations 2
  through 5. One of these locations is chosen for the static port. To
  keep pneumatic lag small, the static port is normally located as near
  the airdata instruments as possible (or the other way around). (To
  determine this location precisely, several static ports are made in
  this area. The optimum location is then selected as a result of
  comparing the various ports with a reference source, such as a
  trailing cone.) This pressure distribution changes with flight
  condition, so a calibration over the flight envelope may still be
  necessary.
  ...
  Even with the selection of the best static port position, some
  pressure errors will remain, and these errors must be determined in
  flight. The difference between the locally measured static pressure
  and the ambient static pressure, which is dependent upon angle of
  attack, airspeed, and aircraft configuration, is called position
  error.

Based on the measured position error, a Static Source Error Correction (SSEC) table is developed. The SSEC is loaded into the air data system when it is installed in the aircraft so that it can make the necessary corrections.


Can a wing generate lift in excess of its aircraft's weight? "For a plane or bird to fly, its wings must produce enough lift to equal its weight. "

I got that excerpt from "https://www.sciencelearn.org.nz/resources/300-wings-and-lift".

My questions:
(1) Can an aircraft wing create lift that is greater than the weight of the aircraft?
(2) If the answer to question (1) is yes, then what happens in such a situation?

Yes, otherwise airplanes would be unable to go upwards into the sky.


What indication will appear in case of one of A320 LGCIU is inoperative? What indication and where it will appear in case of one of LGCIU (landing gear control and interface unit) is inoperative?

enter link description here

A320 ECAM "WHEEL" page

The answer:
The LGCIUs (landing gear control and interface unit) receive position information from the landing gear, cargo doors, and landing flap systems and process gear and door position, sequencing, control, and gear lever selection.

When one of two LGCIU is inoperative (№6) amber XXXs in the triangle - indicates that one LGCIU has failed.

...
Source: http://www.a320dp.com/A320_DP/landing-gear/sys-12.2.0.html


Is it possible to calculate the distance to climb to 1000 Ft in Cessna 172S? Is it possible to calculate the ground roll and distance to climb to 1000 ft in a Cessna 172S?

Why?  I live near a small airport with 2 active flight schools.  As part of a new noise abatement procedure the circuit path will be moving from 500 ft altitude to 1000 ft altitude with no turns below 1000 ft weather permitting.  I'd like to be able to calculate some typical scenarios that will result in determining approximately where the end of the departure leg and the start of the crosswind leg of the circuit will happen to understand what the net change will be.  If I can get the ground distances, I can use the scale line drawing tools on a Google Earth satellite image to draw in some eastward and westward ranges for where the crosswind leg might start, for example on a typical sunny early September morning like today.

I'm not a pilot.  I'm a retired computer systems techno-geek who doesn't mind plunking parameters into formulae to crank out numbers.  I'm just having trouble finding the formula or reference chart.

I've downloaded a Cessna 172S Pilot handbook and have the performance info.  I can get current weather conditions for the airport thru their AWOS or from aviationweather.gov.   I have a binder half full of reference material, sample pilot exam questions, definitions and terminology.  I have the current aerodrome chart for the airport.  I'm starting to muddle my way thru calculating the ground roll and distance to clear a 50 ft obstacle using that reference material.

What I can't find is anything that extrapolates that and figures out the distance along the ground to climb to what is essentially a 1000 ft obstacle.

Can anyone help?

The POH published ground roll is 960 feet. (Performance Specifications, cover page)

The rate of climb from Sea Level is 730 Feet Per Minute, which is 82 seconds to climb to 1000 feet. (Section 5-18, Time, Fuel and Distance to Climb)

During that 82 seconds, the plane will have a airspeed of 74 kts, or 85 MPH, or 1.419 miles per minute.

So in 82 seconds, covering 1.419 miles per minute, the plane will cover 1.93 miles.

1.93 miles of climb, + 960 feet of ground roll = 11,200 feet, or 2.12 miles.

The last column of the table in Section 5-18 is "Distance in NM from Sea Level", which says that the distance it takes to climb from Sea Level to 1000 feet is 2 NM.

2 NM is 2.3 statute miles, which is pretty darn close to my calculation of 2.12 miles (difference of 950 feet).  So the answer cross-checks nicely.

From start of takeoff roll to 1000 feet MSL, you can expect about 2.1 - 2.3 miles, not counting headwind and temperature factors.

I re did the calculations, accounting for a 20 kt headwind. (I think that is the maximum that most Cessna students would take off in), and that shortened the distance to 1.5 miles.

  With max headwind: 1.5 miles
  With no wind: 2.3 miles.

I think that covers your range pretty well.


How can pressure pattern navigation be applied to light airplanes? I want to attempt max range flights in a single engine piston airplane using pressure pattern navigation.  My goal is to achieve greater efficiency than what is published in the POH while still using common cruise settings (ex. 65% at a LOP setting or as published in the POH, usually ROP).  I know pressure pattern flying is employed by GA pilots on long range ferry flights (to Hawaii, for example) but I cannot find practical guidance on how to plan such a flight.  There is plenty of theory and anecdotal information online, and I've read most of it, but very little in the way of practical instruction or calculations.

How would one go about applying PP principles to an actual flight?  My objective is to build a front end user interface using live weather data to plan flights using PP principles.

Hypothetical flight:
Tucson, AZ to McCook, NE at or below 12,500' in an unpressurized 155 KTAS single engine plane with a ~700nm range.  I chose cities that were near the hypothetical plane's max range...could be any city pair.

GA - little piston plane
LOP - lean of peak EGT
ROP - rich of peak EGT

Here is an interesting slide show that may be of some help.

The FAA still does (although extremely rarely from my understanding), issue a flight navigator rating. This rating dates back to the early days before avionics were as sophisticated as they are today. The FAA publishes this handbook (for the rating), Chapter 15 covers pressure pattern navigation and may be what you are looking for.

This document on pressure patterns from a weather standpoint may also be of interest.


Can ailerons be used to control yaw and pitch Is it possible for an aileron to be used to control the roll, pitch and yaw of a vtol drone

Depending on the geometry of the vehicle, up to a degree yes. However, with a classic aileron setup and no rudder, it might be impossible to control roll and yaw independently. A split flap (up and down on same wing) would be required to more effectively control yaw, as that can in theory generate drag on one side without much affecting lift. The B2 bomber sports a similar configuration.


What's the difference between a "runaway prop" and a "feathered prop"? My father was a P-51 fighter pilot in WWII. Another P-51 flown by a buddy of his suffered a "runaway prop", and as a result of that, the plane could not maintain its normal high speed, and in the end, the engine overheated and the plane exploded over the English Channel.  Luckily, the pilot, Major Foy of the 357th FG, had noted excessively high engine temperatures, and bailed out just before it exploded.  What would cause a "runaway prop" of the variable prop to create a loss of thrust and a high engine temperature?

A "run away prop" is caused by a failure of the pitch control mechanism of a constant speed propeller.  Feathering turns the prop blade as close to 90 degrees to the wind as possible, minimizing the effects of the airstream.  This obviously reduces drag and is used when an engine is shut down.

A run away condition is created when the propeller malfunction causes the blade to move to the "fine" setting, which is used at slower air speeds.  It is the opposite of being feathered in that now the prop blades are much more angled to the wind as in a windmill.  The force of the airstream literally now turns the engine to excessive rpm.  The prop is at the wrong pitch for its airspeed, much like a truck dropping into low gear at highway speed.  The engine rpm redlines and causes overheating, while the drag of the improperly set prop slows the plane down.

Thankfully, the pilot was aware of the danger and was able to get away.


Has there ever been a plane with reversed flight controls? Has there ever been a plane which at least one of the primary flight controls is reversed?

For example, pulling back on the stick will cause a dive, or full throttle is achieved by moving the levers backwards towards the pilot.

Well into WWII, quite a few French aircraft had the throttle reversed- with full throttle to the rear. The French also customized the imported aircraft in WWII to this effect. From the book American Warplanes of WWII- Fighters, Bombers and Liaison by Col. John. D. Current:

  ... Officially designated Curtiss H75-C1, the aircraft ... had instruments calibrated for the metric system, ... a French style throttle which operated in reverse from U.S. and British aircraft (full throttle was to the rear rather than to the front)...

From joebaugher.com about the same aircraft:

  The Hawk 75A-1 was powered by the Pratt & Whitney R-1830-SC-G engine, with an international rating of 900 hp at 12,000 feet and 950 hp for takeoff.  ... A modified seat was fitted to accommodate the French Lemercier back parachute. The throttle operated in the "French fashion", i.e. in the reverse direction to the throttles of British or US aircraft.

Looks like the French modified the T-28 Trojans too (though I'm not absolutely sure about this):

  ... the French were looking for a replacement for their ground attack T-6s. ... The French did however acquire 148 A models that were in storage at Davis-Montham. They then changed the engines, (removed the R-1300 and installed the R-1820-76A), reversed the throttle operation, (forward is closed aft is open ?? why do this?) ... These planes were then used by the French in Algeria from the end of 1960 until the end of the war in July of 1962.

Not only the French, the Italians and Japanese also used reversed throttles, which caused quite a few problems in service, as the Wikipedia page on Macchi_C.205 notes:

  In the brief German use, Veltros had at least five losses by accidents, often caused by the inverted throttle used on Italian aircraft (In German and Allied fighters the "open throttle" position was forward, not back, and this was the source of several errors).

The Italians too faced problems with this difference in controls. According to Oddone Colonna, an Italian pilot in 150 Gruppo CT at Gruppo Caccia:

  In the summer of 1943 at Vicenza airport I made my first acquaintance with the "Gustavo", a Messerschmitt fighter of the G-6 version. I was among pilots from 23° and 150° Gruppo Caccia to get first flights in the German plane that had been entering service at the Regia Aeronautica for few months.

  We had two main difficulties on test taxing at the Vicentine airport.

  1)    The gas throttle had an inverted movement compared to Italian vehicles. [The Italians like the French used a reversed throttle in their planes. TNi]

  2)    The Plane had hydraulic pedal brakes instead of pneumatic ones with differential command like on other Italian vehicles.


How does a bearingless rotor work on a helicopter? I have read about some helicopters now using a mechanism referred to as a "bearingless rotor". From what I've seen online, the system involves a flapping hinge.
What I struggle to get my head around is how the rotor spins without a bearing. How is this achieved?

There are still bearings for the spinning part of the rotor mast coming out of the transmission, and for blade pitch in the hub itself.  The bearingless part is that the blade flapping and lead/lag functions are accommodated by "elastomeric" hinges, basically, rubber-type compliant bushings.  It's very similar to the control arm attachments on modern cars where the control arm is attached to the frame with a large rubber bushing, bonded into a sleeve that is bolted to the structure, that accommodates the arm's rotation while isolating the control arm from the car.
Some helicopters also achieve this function by making the root section of the blade into a flexible shaft that is free bend in the flapping and lead/lag direction.
Hingeless rotors have been around since at least the late 70s.


Why was the Graf Zeppelin's endurance when fully fuelled with both fuels less than the sum of its endurances with each fuel separately? The LZ-127 Graf Zeppelin used a unique dual-fuel system, with both a gasoline tank and a set of gas cells filled with blau gas; the airship could be flown using either fuel or both.  The purpose of using blau gas, instead of solely gasoline, was to reduce the amount of hydrogen that had to be valved off for buoyancy-compensation purposes, by reducing the amount by which the airship's buoyancy changed as fuel burned off.1

As might be expected, the airship's endurance was highest when both the gasoline tank and the blau gas cells were fuelled to capacity; however, the figures Wikipedia gives for the LZ-127's endurance using one, the other, or both fuels are somewhat odd, to say the least:

  [...]  Some flights were made using only Blau gas carried in the dozen power gas cells which enabled the airship to cruise for up to 100 hours. Using gasoline alone it was able to cruise for 67 hours, and up to 118 hours using both.  [...]

100 + 67 = ...118?

One would expect that the airship's endurance with both fuel systems filled to capacity would be the sum of the endurance using only blau gas (100 hours) and the endurance using only gasoline (67 hours), which would total 167 hours (100 + 67), or 49 hours greater than what was apparently the actual endurance when using both fuels.

Am I missing something here?

1: Whereas gasoline is much denser than air (and its consumption thus greatly increases the airship's buoyancy), blau gas is only slightly denser than air, and, thus, its consumption alters the airship's buoyancy only slightly.

Graf Zeppelin LZ-127 carried 75,000 cubic meters of hydrogen and 30,000 cubic meters
of Blau gas, which has a similar density to air.  This helped them avoid buoyancy issues when fuel was consumed.

With gasoline, the extra weight had to be compensated with more hydrogen, hence less room for Blau gas.

But I wonder if they could burn some of the hydrogen as fuel instead of venting it when the gasoline was being used up.  This would increase the range considerably.


How are cruise missiles different from ballistic missiles? Cruise missiles and ballistic missiles are used by many nations as offensive and defensive technology. How do cruise missiles and ballistic missiles maneuver, and what are the differences between the basic principles of these maneuvers?

A cruise missile is rocket or jet powered and flies to its target within the atmosphere, using lift to stay up. Most have wings, although a few may use lifting body designs. They maneuver using control surfaces on the wings and tail like an airplane. Mission profiles can include big course changes, to evade air defenses, or to hug terrain to stay hidden. They can be launched from fixed ground positions but most are launched from mobile platforms. They tend to have shorter ranges than ballistic missiles.

A ballistic missile is a rocket that powers its way out of the atmosphere and coasts in an arc, re-entering the atmosphere before hitting its target. They have little maneuvering capability, once the boost phase is done it's all down to physics. Some warheads are able to maneuver a bit in re-entry in order to hit a pinpoint target, others are just rocks at that point. The largest ones are launched from fixed positions like missile silos but smaller ones are mobile.


How do the wings connect to the centre wing box? First of all does the centre wing box form part of the fuselage as it's in the centre of the fuselage? Secondly how does the wing spars connect to this centre wing box to hold everything together?

Transport airplanes, in general, use one-piece wings with no joints between sections. The "wing box" is the central structural element for the entire wing, made up of front and back spar webs, and upper and lower planks, which make the 4 sides of the box.  Leading edges and trailing edges/control surfaces are tacked on to the front and back walls of the box.

The upper and lower planks (machined skins) are the primary structural members in bending, supported by the spar webs to resist shear loads and the wing ribs to support the planks themselves against buckling.  You could say that the entire upper and lower skins or planks are the spar caps.

The "center wing box" is the middle section of the overall wing box, but that just describes the center part of a very long box.  The fuselage will simply sit on top of it, with a square cutout in the bottom to fit over the wing, with fairings all around the connection to make an nice external transition for the air flow.

The fuselage will be integrated into the wing box structurally with some sort of connecting links joining fuselage frames to the box, and may also have fuselage skins attached directly to the wing box.  Sometimes the cutout in the fuselage has its own pressure bulkhead forming a box outside the wing box and you can simply unbolt the fuselage from the wing and lift it off, and sometimes the wing box itself is made part of the pressure hull, requiring lots of rivets to be drilled out to separate them.

If the airplane has wings that attach to each side of the fuselage with big spar fittings and bolts, the center wing box will be an integrated part of the fuselage, what you would call a structural pass-through.


Can a Eurofighter 2000 trainer be converted to a combat capable Eurofighter 2000? It surprises me to see that in some aircraft inventory listings, a rather considerable percentage of combat aircraft are "trainer" versions.

E.g. https://en.wikipedia.org/wiki/Spanish_Air_Force#Current_inventory

For Spain, it is claimed they have 56 Eurofighter 2000, and 12 trainers. Somewhat similar numbers apply to their F-18 variants regarding combat aircraft and trainer aircraft.

I'm curious what the difference is between these Eurofighter 2000 combat vs. trainer aircraft. In particular, how much effort is it to make a trainer EF2000 combat ready? Perhaps they actually are combat ready? Surely there are some differences though, such as having two seats? What else?

From the Wikipedia page on the Eurofighter Typhoon, under Variants:

  The Eurofighter is produced in single-seat and twin-seat variants. The twin-seat variant is not used operationally, but only for training, though it is combat capable.

No source is cited for that claim, but it seems logical enough.


Are the airspace times of operation days of the week in local or Zulu time? The margin of the Enroute High sectional H-4 claims that the times of operation of the airspace R-5107K near El Paso are "1400-0300Z, MON-FRI" (and other times by NOTAM).

If the days of the week are Zulu time then by converting this to local time would yield "0800-2100, MON-THU".

You could argue against this interpretation because usually, we use the days of the week to reference the starting time, which would mean that the airspace is available starting at "1400Z MON-FRI" which is still "0800 MON-FRI" when converted to local.

But that doesn't explain that on the Enroute Low sectional L-5 the OUTLAW MOA is available "0100-0500Z, MON-FRI by NOTAM".

If the days of the week are ZUlu time, converting that starting time to local time would yield "1800-2200, SUN-THU".

Assuming the NOTAM for this airspace is active, do they really mean that the airspace is active "1800-2200, SUN-THU"? or do they mean that it is active "1800-2200, MON-FRI"?

The VFR chart covering this area shows local times instead.

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


What is this plane seen in Mobile, Alabama? This was taken at the USS Alabama in Mobile, Alabama. It is probably a US Navy aircraft.

(Source)
B-52D Stratofortress "Calamity Jane".
It is a long-range, subsonic, strategic bomber operated by the US Air Force (not the Navy) since 1955.

The aircraft you see here was amoung 170 B-52Ds manufactured by Boeing Airplane Company, and was equipped exclusively for long-range bombing missions. "Calamity Jane", as she is called, has been demilitarized, but remains in the high camouflage used during Vietnam operations. (Source)


Why it doesn't matter if tail produce lift or downforce for neutral point position? I am really strugle what neutral point represent and what it depends on..
In this link we can see how neutral point is calculated.Thay use wing and tail areas and distance  between aerodynamic center (L) to determine neutral point position (D).Calculation is set like tail produce lift..(So calculation is the same like you must find fulcrum at see saw..)
What if tail produce downforce(what is often case).If this tail in my example produce downforce,neutral point will move to the left,completly different position.
Does neutral point  dependt at change of aerodynamics forces at wing and tail,for example  when you change tail incidence,etc?

If I put aircraft in vertical position to eliminate torque by gravity,connect with joint so he can rotate, now must find place at plane which will not rotate(moment is zero) when is subject to airflow.
Is this place neutral point?

The neutral point is the lengthwise location of the moment reference point where the pitching moment will not change with a change in angle of attack. It can be defined for a wing alone or for the whole airplane.
Of course will a change in the incidence of the tail also change the pitching moment around the neutral point. But that is besides the point: The special characteristic of the neutral point is its neutrality regarding to changes in angle of attack.
Mathematically speaking: If the slope of the pitching moment over angle of attack is zero, the reference point for this moment is the neutral point. If you pick a different point ahead of the neutral point, the slope will become negative (which characterizes a stable configuration) and vice versa. The neutral point depends on the derivative of the pitching moment over angle of attack, so the absolute value of it doesn't matter. It's the change with angle of attack that counts.
If the center of gravity coincides with the neutral point, the airplane has neutral longitudinal stability. Hence the name.
This all is valid only in the range of attached flow. If there is massive separation, all bets are off.


Is there a service to review prior flight plans? I was wondering if there is anyone that offers on-line searching of prior flight plans.

Lockheed Martin Flight Services (LMFS) provides a history of filed flight plans on their web site under Flight Planning & Briefing | History. The path to the particular page is: https://www.1800wxbrief.com/Website/showPilotHistory.

Unfortunately, only the last 15 days are available. So if your flight plan is older, it won't be displayed. Additionally, if you're filing your flight plans through a service provider that doesn't provide full LMFS integration (e.g., ForeFlight) it won't be displayed even if within 15 days. In this case, you'll need to refer to your service provider's interface.


What restrictions apply in international airspace? What restrictions are there on a flight in international airspace? For example, if you fly into the Pacific Ocean more than 12 miles (or whatever the distance is) offshore, are you free to fly any speed (such as faster than sound), at any altitude, or in any weather? Are FAA regulations in effect?

Is anybody really "in charge" of this airspace? If not, how do airliners keep organized on intercontinental flights?

When a US registered pilot is operating in international airspace, he is bound by both the US aviation regulations (14 CFR) and ICAO Annex 2, as required by 14 CFR 91.703.  It also requires compliance with MNPS and RVSM airspace rules where appropriate.

  Sec. 91.703 - Operations of civil aircraft of U.S. registry outside of the United States.

  (a) Each person operating a civil aircraft of U.S. registry outside of
  the United States shall--
  (1) When over the high seas, comply with
  annex 2 (Rules of the Air) to the Convention on International Civil
  Aviation and with Secs. 91.117(c), 91.127, 91.129, and 91.131;
  (2) When within a foreign country, comply with the regulations relating to
  the flight and maneuver of aircraft there in force;
  [(3) Except for
  Sec. Sec. 91.117(a), 91.307(b), 91.309, 91.323, and 91.711, comply
  with this part so far as it is not inconsistent with applicable
  regulations of the foreign country where the aircraft is operated or
  annex 2 of the Convention on International Civil Aviation; and]
  (4) When operating within airspace designated as Minimum Navigation
  Performance Specifications (MNPS) airspace, comply with Sec. 91.705.
  When operating within airspace designated as Reduced Vertical
  Separation Minimum (RVSM) airspace, comply with Sec. 91.706.

  (b) Annex
  2 to the Convention on International Civil Aviation, Ninth
  Edition--July 1990, with Amendments through Amendment 32 effective
  February 19, 1996, to which reference is made in this part, is
  incorporated into this part and made a part hereof as provided in 5
  U.S.C. Sec. 552 and pursuant to 1 CFR part 51. Annex 2 (including a
  complete historic file of changes thereto) is available for public
  inspection at the Rules Docket, AGC-200, Federal Aviation
  Administration, 800 Independence Avenue SW., Washington, DC 20591; or
  at the Office of the Federal Register, 800 North Capitol Street, NW.,
  Suite 700, Washington, DC. In addition, Annex 2 may be purchased from
  the International Civil Aviation Organization (Attention: Distribution
  Officer), P.O. Box 400, Succursale, Place de L'Aviation
  Internationale, 1000 Sherbrooke Street West, Montreal, Quebec, Canada
  H3A 2R2.

Another unrelated FAA document explains it in plain language:

  International Civil Aviation Organization (ICAO)

  ICAO is an agency of the United Nations that originated from the
  signing of the Convention on International Civil Aviation in December
  1944 (referred to as the Chicago Convention). This organization was
  formed to promote the safe and orderly development of international
  civil aviation. The Chicago Convention produced International
  Standards and Recommended Practices (SARP) aimed at standardizing
  international civil aviation operational practices and services.
  Currently, these SARP's are contained in 18 annexes to the Chicago
  Convention. In particular, Annex 2, Rules of the Air, and Annex 11,
  Air Traffic Services, are pertinent to this paper as they relate to
  civil aircraft operations, the establishment of airspace, and air
  traffic control (ATC) services in international airspace. Although not
  addressed in this paper, it should be noted that the SARP's are
  augmented by various ICAO documents containing Procedures for Air
  Navigation Services (PANS) that amplify the basic principles in the
  SARP's. Further, to supplement the worldwide procedures contained in
  the annexes and PANS, ICAO develops Regional Supplementary Procedures,
  which are part of the Air Navigation Plans agreed upon to meet the
  needs of specific geographical areas.

  Two articles of the Chicago Convention also have a bearing on the
  subject of this paper:

  Article 3:

  Exempts state-owned aircraft (which includes military aircraft) from
  the provisions of Annex 11 and its Standards and Recommended
  Practices. (Note: As an ICAO Contracting State, the U.S. has agreed
  that its state aircraft will be operated in international airspace
  with due regard for the safety of civil aircraft.)

  Article 12:

  Obligates each ICAO Contracting State to adopt measures to insure that
  persons operating an aircraft within its territory shall comply with
  that state's air traffic rules; or with Annex 2, Rules of the Air,
  when operating over the high seas. The U.S. satisfied this
  responsibility through Title 14, Code of Federal Regulations (CFR)
  Part 91 which requires that operators of aircraft comply with U.S.
  operating rules when in the U.S., and that U.S.-registered aircraft
  comply with Annex 2 when over the high seas (see section 91.703).
  However, section 91.703 applies only to civil aircraft, and state
  aircraft operating outside the U.S. are only subject to the "due
  regard" provisions of Article 3 of the Convention.

  Under ICAO agreements, the SARP's in Annex 11 apply to airspace under
  the jurisdiction of a contracting state which has accepted the
  responsibility of providing air traffic services over the high seas,
  or in airspace of undetermined sovereignty.


Why would the front edge of an aileron fold outward? I was just enjoying a movie of one Svetlana Kapanina flying her EA300. One camera looks out of the cockpit over the left wing. In a couple of scenes, the aileron of the wing can be seen quite clearly. The picture (see 1) shows it deflected downward, except for the red "end" deflecting upward. Other scenes show that when the aileron deflects upward, the red "end" turns downwards.

What is the reason to have this red "end" tilting in opposite direction to the aileron?

NB, you can enjoy the whole movie here:

That is an enclosure for a counterweight, either made from steel or lead to balance the aileron and/or reduce control flutter in various flight regimes. The extension provides an additional lever arm to alter the moment of inertia about the aileron’s axis of rotation.  These are usually added or refined during flight testing to remove undesirable flutter or other qualities inherent in the design.  Counterweights are usually installed at the factory with the airplane but custom made counterweights can be used on a specific aircraft to provide a specific feel to the controls to meet customer requirements.  Many high performance experimental category acro aircraft do this on aircraft custom built for a master aerobatic flyer.

The comment above about this providing an aerodynamic counterbalance is incorrect.  Such devices for this purpose do exist but in the form or one or more ‘shovels’ or ‘spades’ on the underside of the control surface.


Is induced drag caused because of the tilt of the wing backwards? In this question:
Why is induced drag less on a high span wing?

In the answer it was stated that wing tip vortices do not cause induced drag. If this is the case then what causes the induced drag.

Thinks about this for 10 minutes

What if the Induced drag occurs because of the tilt backwards of the wing. Do the vortices just make the induced drag worse but, not cause it.

So basically I am asking if the backwards tilt of the wing causes induced drag and how do the wingtip vortices affect the induced drag

This may sound like a duplicate of:

Is induced drag not caused by tip vortices?

but, It is not because I am asking if the induced drag is causes by the tilt of the wing. I am not asking if induced drag is caused by wing-tip vortices or not.

Although your explanation isn't entirely wrong, It isn't necessarily the backward tilt of the wing, but the backward tilt of the aerodynamic force.

I look at it from two different perspectives. The airfoil is designed to accelerate air thus creating the pressure differentials that make the plane fly. The higher pressure areas will try to push the wing toward the lower pressure areas. The overall sum of these forces is called the resultant force.

That resultant force will have an amplitude and a direction or vector associated with it. The goal of designing an airfoil is to orient those forces upward to counteract gravity. So the designer will make the low pressure areas on top of the wing and the high pressure areas on the bottom to make the vector point upward. A perfect airfoil would create a vector pointing directly upward, 180° from the ground and 90° from the direction of travel. In reality, nothing is perfect, so that vector is always pointed backward to some degree. So we break that resultant force into two components. The part we're trying to accomplish, which is 90° from the direction of travel is called lift and the remaining part which is 180° from the direction of travel is called the induced drag since it is induced by the creation of lift. Even a wing producing lift at a 0° angle of attack will still produce a certain amount of induced drag.

Now we come back to your explanation. Although any time a wing is producing lift it will also produce some induced drag, as you increase the angle of attack the vector of the resultant force tilts back with it. Not necessarily at exactly the same rate, but usually not far off. Since we are still defining lift as 90° from the direction of travel and drag as 180° from it, the ratio between the two changes. For every bit of lift produced there is a lot more drag the further you tilt the wing back.

The second way of looking at it is from the inertia point of view. The intent of the wing is to accelerate air downward. Once again, a perfect airfoil would accelerate the air straight down, but in reality it will always accelerate it slightly forward also. And as you tilt the wing backwards you will produce more forward movement and less downward.


On a large transport aircraft where exactly is the Forward pressure bulkhead? Is the Forward pressure bulkhead in front of the pilots.. I.e when you lift the Radome for maintenance is that the Forward pressure bulkhead you can see? Some images or a diagram would be great.

It's located  in the aircrafts radome (nose) where the weather radar is located. It's to keep the pressurized air from exiting the fuselage.


What are the limits of ground effect over water on an airliner plane at cruising speeds? What height over a fixed plain (such as water) can a plane begin to take advantage of the ground effect or when air is compressed between the wing and ground near cruizing speed? Could an airliner type plane fly above the water for an added lift for range in an emergency where a plane may lack the power to climb?

Ground effect only comes into play within about 1 wingspan’s height above a surface and it is largely unnoticeable until approx 1/4 to 1/10 of a wingspan above the surface.

While it is true that ground effect greatly increases the lift to drag ratio of the wings, it does not reduce parasite drag nor does it account for the fact that it is more efficient to fly at higher altitudes where the atmosphere is much thinner for greater speeds per unit of fuel consumed.  Flying low to the ground is dangerous as there is less margin for error if something goes wrong and would limits operations to day VFR conditions.

Transport airplanes have been test flown and certain flight profiles have already been determined to offer the greatest range.  These occur at altitude and on reduced power settings.

Heavy sea transports which to use wing in ground effect for lift  have been proposed in the past, but been found to be in efficient compared to existing jetliner designs. WIG craft have been used for short transport missions like island hopping, where that kind of a craft would be faster than a ship, and more efficient than a light airplane.


How do instructors simulate instrument failure in basic training aircraft with glass cockpits? While working towards my private pilot's license in the United States in 2004-2005 (in a steam gauge only airplane), I very much remember my instructor covering one or more instruments to simulate failure and recovery techniques.  He used covers which are commonly available in pilot shops:

I don't remember the examiner asking me fly under such conditions, but this type of failure is covered in the FAA PTS both for private and commercial.

Now that more and more pilots are training with glass cockpits, I was wondering how covering instruments the same way would work.  For reference, let's take the Garmin 1000, standard in the Cessna 172 Skyhawk, which I have to guess is one of the most common civil aviation trainers:

I am, of course, assuming it would be much more difficult to cover the altitude indicator, airspeed indicator, artificial horizon, etc. on a glass cockpit display, not to mention being a questionable practice on a multi-thousand dollar LCD screen.

Then it occurred to me that perhaps the glass cockpit manufacturer would just provide the ability to temporarily disable specific instruments.  But (at least for the G1000) I did not find this feature in the manual.

To summarize, my question is, how do flight instructors/examiners simulate the loss of one of the "six pack" flight instruments in an airplane with a glass cockpit?

For conventional instrument gauges, I recommend the disks above for blanking out the attitude indicator or the DG/HSI.  Post-It notes are also a common way to blank out instruments to be used.

For partial panel work in glass cockpits, manufacturers and pilot supply shops sell soft stickers custom made for this purpose.


Will control surfaces on a plane be less efficient at a higher altitude? I may be wrong but I learned that control surfaces depends on the air flow to work properly, and that airliners have a higher cruise altitude because of the less dense atmosphere, improving the fuel efficiency.

But that got me thinking:

Will control surfaces on a plane be less effective at a higher altitude because of the less dense air?
Do modern airliners have a workaround to solve this problem?

Please let me assume that you wonder about control surface effectiveness rather than their efficiency. Both are closely related, but I prefer to address their effectiveness - doing what the pilot demands them to do.

The aerodynamic forces are proportional to the dynamic pressure $q$ of the flow, which is density times velocity squared, as in
$$q = \frac{\rho}{2}\cdot v^2$$

To create the same amount of lift at a higher altitude, the airplane has to fly faster, so in effect the forces can stay the same. Only the true air speed will be different, which helps to get where you want faster. The control surface effectivity remains unchanged.

If we dig a little deeper, the atmosphere cools down with increasing altitude until you reach the Tropopause. This cooling makes the engines more efficient but also reduces the Reynolds number of the flow around the aircraft. A lower Reynolds number translates into a thicker boundary layer, which will reduce the effectiveness of control surfaces a tiny bit and will reduce the range of their best effectivity. But this effect is so small that it has no practical consequence.

Airliners fly at transsonic speeds at altitude, so now sonic effects become more pronounced. For the control surfaces this means that they will lose their effectiveness at higher deflection angles. For small corrections all is very similar to low level, slow flight, but if you need full deflections the control surfaces are indeed less effective at altitude.

Another effect will be rather more pronounced, and this is aerodynamic damping. Damping is the tendency of a system to create additional forces from movements which run against this movement. Take a wing: If the aircraft rolls, the wingtips will move up on one side and down on the other. Both movements will add a small angle of attack, lowering the total angle of attack on the up moving tip and increasing it on the down moving tip. Both tips will see a change in lift which will counteract the rolling motion. If the rolling speed is $\omega_x$, the resulting change in angle of attack $\alpha$ at a wing station $y$ is
$$\Delta\alpha = arctan \left(\frac{\omega_x \cdot y}{v}\right)$$
As you can see, the flight speed is in the denominator, so a higher flight speed will create a smaller angle change for the same roll rate. The same holds true for the other axes of movement, and in consequence the higher-flying aircraft needs either more pilot attention or an artificial damper.

I guess it is the lower damping which made you think that the control surfaces are less effective. They aren't.


In what scenarios would one want to maximize or minimise rate of climb in an aircraft? What are examples of scenarios where a pilot would want to maximise or minimise aircraft rate of climb? What performance metrics should one consider to analyse steady climbing flight?

The scenarios I thought one would maximise rate of climb is military aircraft dog fight and clearance of airspace quickly in airports

Please add your thoughts if you can imagine any

Dogfight is about energy management. You care less about climbing than about being able to turn your nose and weapons into the right direction as quickly as possible without falling out of the sky.

Maximum climb would be required in those scenarios:

Fly as efficiently as possible. Flying higher means flying faster and in colder air, so the engines are more efficient. Note that todays airliners climb as fast or faster than fighter aircraft in WW II.
Evade ground threats. After delivering its ordnance, an attack aircraft would desire to get away from hostile fire as quickly as possible. Sometimes this is achieved by flying with the best climb angle, though.
Break off combat: If you know you can climb faster than your opponent, you can choose whether you fight or get away, a luxury the other guy does not have.
Intercept: If you were ordered to intercept an unknown aircraft flying high above, maximum climb speed is helpful. If you need to be fast as well, your optimum climb profile is that of highest energy gain, though.

I interpret minimum rate of climb as maximum descent rate. Typical scenarios are:

Pressure loss in an airliner, when higher density air should be reached in order to continue the flight safely.
Dropping parachutists: If the aircraft lands ahead of the skydivers, it can fly more often and earn more revenue.
Extreme case: Dive bombing. Actually, most dive bombers employed air brakes to limit the speed in a dive.


Will an axial compressor work with an ideal fluid? Will an axial compressor, like the one described starting on page 275 of Mechanics and Thermodyanmics (PDF link), work if the flow was assumed to be ideal (i.e. incompressible and inviscid)?

Specifically, what mechanism will slow the flow down in the axial direction? It's my understanding that slowing the flow down is the job of the stators, but I fail to see how they accomplish this in the axial direction.  The author states on page 284 that the axial flow velocity through the compressor is made constant by design but never explains how that design is achieved and I'm curious if that design could still be achieved with an incompressible fluid. -Thanks in advance!

First of all, incompressible flow is subsonic, however subsonic flows are not all incompressible. An ideal gas flow may be "incompressible" until it meets the compressor. Even if the vehicle is travelling at supersonic speed, the flow is reduced to subsonic ("incompressible") flow by the intake system before reaching the compressor. At this point the subsonic flow gets compressed. Presumably this is what is meant here.

The compressor stages each reduce the cross-sectional area, while the fans draw the gas backwards to maintain velocity. Thus the gas, ideal or not, must compress to fit the reduced volume available to it. This compression creates heat which raises the gas temperature, further raising its pressure.

Viscosity is necessary to establish a circulatory flow component around each airfoil-shaped blade (the Kutta condition). It is this circulatory component which creates the velocity differentials needed for the Bernoulli principle to create the dynamic pressure differentials which make the blades do their work. Superfluid helium (close to absolute zero) has no viscosity and has been found to exert neither lift nor drag on an immersed body.


Can autothrottle be used without autopilot (and vice versa)? In commercial passenger aircraft:

Can autothrust be used with A/P disabled ?
And can A/P be used without using autothrust?

Citable references very welcome!
If the question depends on a specific aircraft type, then please B777.

They can be used individually, yes. When flight directors (or autopilot) are on then they dictate what auto throttle should do. But it's not a good idea to fly manually, use auto throttle and have flight directors still on and here is why:

When autopilot is off but the flight directors are on and auto throttle is on you can select a vertical mode like flight level change or vnav and then auto throttle will take commands from that selected vertical mode. In flight level change, for example, thrust is either full climb thrust or idle thrust, which means: If you as a pilot flying don't pitch for speed then you just have throttle stuck in either full or idle and you either overspeed or stall. Not a good idea to leave flight directors on and use autothrottle on its own!
When autopilot is on but auto throttle is off then autopilot and you select a vertical mode like vnav or flight level change then you are in command of delivering thrust, so you need to advance throttle to start climbing or you need to retard throttle to descent. And if you use vertical speed mode you are in control of airspeed. So you have to monitor your climbs and descends and airspeed but it's not too bad. In the end there are other aircraft types that have an autopilot but no auto throttle.
When autopilot is not engaged and flight directors are off then auto throttle controls just speed, this is safe. Airbus' landing checklist has an item for this: "auto thrust? - SPEED".

This applies to 777, 747, 737, A320, A380 and probably (have not checked the fcoms) A350, A330, A340, 757, 767


How is crankcase ventilation handled in R-2800? I just finished R-2800: P&W's Dependable Masterpiece and noticed there's no mention of a pump for crankcase ventilation. Is this handled by the oil scavenge pumps?

In a car the combustion gasses that blow past the piston rings are sucked out by a line connecting the crackcase to the intake manifold by a check valve (the PCV valve).  The suction "pump" is from the low pressure in the intake manifold.  Cars before the PCV valve (developed in the 50s) just vented the crankcase gasses overboard through a hose.  Aircraft engines, including the big radials and the Lycoming engine on my own plane, do the same.

Positive crankcase ventilation was probably the first pollution control device developed for cars.  Piston aircraft engines have never used pollution control devices.  They still use gasoline with lead in it.


Why was the Yak-9U covered with Bakelite? According to Wikipedia the entire Yak-9U was covered with Bakelite (not sure if it was just that variant, the page isn't clear). What was the reason for this and was Bakelite used as a coating on any other aircraft?

The Bakelite finish was for the wooden parts/variants.

Bakelite back then was a novelty, its usage in airplanes strengthened the wood, made it moisture resistant, and offered a smooth aerodynamic light-weight finish.

It was also highly flammable:

  The LaGG-1 was built with highly flammable delta-drevesina (delta wood), plywood sheathing, and bakelite ply, and burned so easily that the pilots sarcastically joked that LaGG in Russian stood for Lakirovannyi Garantirovannyi Grob (varnished guaranteed coffin).

The LaGG-3 article on Wikipedia offers more details on this method of construction:

  [The] airframe was almost completely made of timber, with the so-called delta-lumber (a wood-plastic composite composed of very thin, 0.35 to 0.55 mm, wood veneer and phenol formaldehyde resin [Bakelite], baked at high temperature and pressure) used for the crucial parts. This novel construction material had tensile strength comparable to that of non-hardened aluminum alloys.

Sources: MOISTURE RESISTANT FINISHES FOR AIRPLANE WOODS (NACA, 1920), and Russian Aviation and Air Power in the Twentieth Century By John Greenwood.


How does the V-22 Osprey share engine power between its rotors? I learned through a comment on this question about multiple engines powering a single propeller that the V-22 Osprey can power both rotors from a single engine, or use both engines to power a single rotor. What are the mechanical systems that make this possible?

It is possible to drive the two rotors of the V-22 Osprey from a single engine using a segmented driveshaft connecting both engine shafts via gearboxes:

The drive shaft is depicted in blue in the left wing. Source

Each engine drives its own rotor and the connecting shaft. If one fails the same rotation speed is maintained, but each rotor receives now half the power of the remaining engine.

A similar mechanism is also used on the CH-47 Chinook family:

Source

This is a CH-47 Chinook green drive shaft:

Source

On aircraft with two distant rotors, it is vital to have both rotating, as if one slows or stops the aircraft is unbalanced to the extend it crashes.


How common is it in current British usage for the angle between the chord line of a wing and the flight path to be called the "angle of incidence"? In American usage, the angle between the chord line of a wing and the flight path is called the "angle of attack".  The angle of attack is also represented by the greek letter "alpha".  However, some British authors, especially in the past, have referred to this angle as the "angle of incidence".  (See one supporting reference here.)

We'll call this the "older British" use of the term "angle of incidence".  How common is this usage now in the British aviation world?  Has it completely fallen by the wayside, or is still common?  Was it ever very common?

Also, what term or terms did authors and speakers following this "older British" usage, use to refer to the angle between the wing chord and the longitudinal axis of the fuselage (or some other similar defined datum line approximating the longitudinal axis of the fuselage?)  Some of the terms that have been used for this angle by writers and speakers following the "older British" usage noted above, appear to include "rigger's angle" and "rigger's angle of incidence".  Are there others?

(In American usage, this latter angle is in fact the angle that is called the "angle of incidence".)

(Bonus extra part: is there one particular greek letter that is normally assigned to this latter angle in engineering texts and papers, much as "alpha" is normally assigned to the angle that is described in the first paragraph of this question?)

From A.C. Kermode; Mechanics of Flight, London, Pitman, 8th Edn, 1972, p.75 (his bold):

"We call the angle between the chord of the aerofoil and the direction of the airflow the angle of attack.
"This angle is often known as the angle of incidence; the term was avoided in early editions of this book because it was apt to be confused with the riggers' angle of incidence, i.e. the angle between the chord of the aerofoil and some fixed datum line in the aeroplane. Now that aircraft are no longer "rigged" (in the old sense) there is no objection to the term angle of incidence; but by the same token there is no objection either to angle of attack, many pilots and others have become accustomed to it; it is almost universally used in America, and so we shall continue to use it in this edition."

And from L.J. Clancy; Aerodynamics, London, Pitman, 1975, p.56:

"The attitude of the aerofoil, as expressed by the angle between the chord line and the free stream velocity vector ... , denoted by $\alpha$, is called the incidence, or angle of attack."

In contrast to Kermode, Clancy goes on to use "incidence" throughout. Note that this contrast appears in technical books from the same publisher, just three years apart. It was, and is, no big deal.
In my experience, anybody with the slightest technical interest in flight is familiar with both usages and they both still get used interchangeably in the UK.
I have not seen a standard symbol for the rigging angle, presumably because it is of irrelevance to the aerodynamicist. It was once, and occasionally still is, alternatively referred to by its French name of décalage.


Why does condensation form on the wing especially during take-off and landing? To start off, yes this question was asked before, yet I don't find the answers satisfying and here is why:

It appears to me that this phenomenon only appears during the approach phase of a flight and during low speed turns, or rather when the angle of attack is rather high. Also, usually the flaps are deployed when it happens, yet I'm not sure if that makes a difference.

Considering this, the answers wouldn't necessarily answer my question. They all talk about how there is a lower pressure above the wing, which causes the dewpoint to drop and thus makes the water condense. But is there a "lower" lower pressure when the angle of attack is higher and therefore making this phenomenon occur more often? Or is the point at which the laminar airflow gets turbulent (which moves forward as the aoa is increased) an important factor here?

Here is a picture to show what condensation I mean:

And a more extreme one:

Yes, speed and flaps do make a difference.

The lift created by the wings is approximately constant over the duration of a flight. With full tanks, it is higher at the beginning of the flight, and when the aircraft banks, it is again higher to create the centripetal force for changing its course. But the difference is small¹.

Lift is caused by a pressure difference between the two sides of the wing. In cruise, this difference is low but extends over much of the wing's chord. At low speed, however, the suction on the top surface has a peak right aft of the leading edge, so the maximum suction is bigger than it is in cruise. Exactly this changed pressure distribution causes the humidity to condense, because it lets the air's relative humidity rise above the condensation point. In cruise, the pressure change is lower and the dew point is not exceeded. Also, since the airplane flies slower when close to the ground, the air has more time for the condensation to develop.

See below for a color-coded plot of the speed distribution over a typical airliner airfoil in the landing configuration. Red symbolizes the lowest speed (highest pressure), while purple stands for the highest speeds with the lowest pressure. Such suction peaks must be avoided in cruise to enable the aircraft to fly at a high cruise Mach number.

Airliner airfoil with high lift devices in landing configuration (picture source)

¹ The fuel fraction of airliners rarely exceeds 40%, and the added lift in a 30° bank is only 15%.


How fast were propeller planes during landing on aircraft carriers during WW2? I have seen reports of up to 90mph but that seems high?

The stall speed of the F4U Corsair may be 89mph, and a safe approach speed might be 95-100mph, but that's airspeed... Measured with reference to the carrier deck, you have to substract 20mph headwind (nothing unusual at sea) and also around 30 mph of the carrier own speed. Hence, that plane touched down at a sedate 45-50 mph, with respect to the carrier deck...


Why are the center tank pumps deactivated when slats are extended on the A320? Why are the center tank pumps deactivated when slats are extended on the A320? I researched about this and all I can see is hints. They say it is because of regulations or certifications.

You're right. But it's not because of the slats. It's because of what the plane is doing when the slats are being used.

The slat position is used in some system logic because it's indicative of a takeoff and approach. For example, on the MD-11 the engine ignition is automatically put into continuous mode when the slats are operated, because that's indicative of slow speed.

The same for the A320, slats extended means a takeoff / climb is about to commence, or the plane is on approach with a potential go-around.

Those conditions require high fuel pressure.

The center tank has 2 pumps, while each wing tank has 2 pumps. If a center tank pump fails, it will be 1 pump supplying 2 engines, compared to 2 pumps for each engine (or 1 for each in a rare double pump failure—one in each wing).

If a pump fails, there is no automatic command that can be sent to the sequence valves to change the sequence, or to engage the crossfeed valves.*

Usually the center pumps overpower the wing pumps, but what is omitted from that explanation is that there are sequence valves. If one center pump fails, the pressure may remain high enough to keep the valves closed on the good side, but not high enough to supply two engines during high demand.

Also note there is no suction (gravity) feeding from the center tank. I attached an A320 fuel schematic below, number 13 is the sequence valve.

RE: Why does not this apply to all aircraft?

The 737 Classic faced issues (see footnote). Other types have more than 2 pumps for the center tank, and/or have more powerful pumps. Another option is to use the center tank to fill the other tanks (like on the MD-11).

The 747-1/200 also required using the wing tanks during takeoff, see this answer by @Terry.

A speculation on my part, is that it was cheaper to certify the plane like that, or problems were found and that was the cheapest solution.

  A fuel tank that is not designed to feed the engines under all flight conditions need
  be tested only for the flight regime for which it is designed to do so (e.g., cruise conditions).

  (FAA Flight Test Guide For Certification
  Of Transport Category Airplanes)

* A fuel imbalance may quickly develop when each engine is consuming +70 kg of fuel per minute (an issue that affects the 737 Classic).

  On the classics, when departing with less than 1,000kg of fuel in the centre tank, an imbalance may occur during the climb. This is because the RH centre tank pump will stop feeding due to the body angle so number 2 engine fuel is drawn from main tank 2, while engine 1 is still drawing fuel from the centre tank. When this “runs dry” the scavenge pump will also transfer any remaining centre tank fuel into main tank 1, thereby exacerbating the imbalance.

(A320 FCOM)


How far can Boeing 777-200LR fly? The diagram shows the B777-200LR Payload/Range for 0.84 Mach Cruise (P.41 of Source)

The maximum payload range is around 7600 nmi, and after that payload have to be reduced in order to increase range. While the Operating empty weight of 777-200LR is 320Klbs, the horizontal-coordinate(range) of the diagram is around 10500nmi at 350Klbs, and there is a gap of 30Klbs.

Does that mean B777-200LR has theoretical maximum range over 10500 nmi if OEW plus payload is below 350Klbs? And how far can it fly potentially?

The vertical axis starts at 350 Klbs since the Boeing 777 is made to transport payload, not just itself. Any operator will be interested more in the upper part of the diagram, because only then the aircraft will earn money. This explains the gap of 30 Klbs - the people for whom this chart was made are simply not interested in the range without payload.

The range varies with flight parameters, and the upper left corner shows the most important ones, albeit in quite imprecise terms. If the flight speed is reduced, range will become higher until the aircraft flies at optimum range conditions. Airlines like to fly their aircraft faster that that to optimize transport performance (the maximum product of speed and payload relative to operating cost). If power extraction and air condition are run at their bare minimum, again less fuel will be needed per mile of flight. Flown this way, the 777 will easily fly more than 10500 nm with a zero-fuel weight (OEW + payload) of 350,000 lbs.

To eke out the maximum possible range, high-density fuel is used and the aircraft is flown at an optimum altitude and speed for range. The records which have been set this way (11,664 nm for the 777-200ER), however, are of little relevance to everyday operation. The longest commercial flight of that type will be the Dubai-Panama City connection of 7,463 nm which Emirates will begin to serve on February 1, 2016.


Do wingtip vortices cause a decrease in the lift component of aerodynamic force, and do planes need to pull more AoA to compensate? So, from what I know about wingtip vortices, they shift the angle of the relative airflow to where the effective angle of attack of the airfoil is lowered. Since the aerodynamic force is always perpendicular to the relative airflow, the aerodynamic force is also shifted and now has a backwards-facing component to it, which we call induced drag. Now, my question is, just looking at the way the vectors point, the tilting of the aerodynamic force backwards means that, while there is a greater backwards facing component, the upwards facing component (what we call lift) is decreased, right? So we can say that the vortices shift the aerodynamic force in a way so that the induced drag increases, but the lift decreases, right? And, if that is the case, then wouldn't the aircraft then need to pull an even greater AoA to compensate for that lost lift, which in turn would create even more pressure differential, which would then increase vortices even more? Then even more AoA would be needed, and so on... Then this cycle would go on until the aircraft bled all its speed... Obviously, that isn't the case and there isn't a snowball effect in real life? So is my fundamental understanding of vortices and induced drag off?

What you know about wingtip vortices is what can be found all over the Internet, but it is not really true. It is like saying that wet streets cause rain.

Your way of explaining things confuses cause and effect. The vortex is the effect but not the cause of drag-creating flow. And lift-creating flow, by the way. But nobody claims that the tip vortex is the source of lift, which is equally false and uses the exact same logic.

Wingtip vortices are just the tip of a full vortex sheet which leaves the wing. This vortex sheet is the consequence of the wing accelerating air downwards. Now instead of repeating myself all over again, please allow me to point you to the many other answers which explain what is going on:

This answer explains in detail how lift is created and how the downward acceleration of air is accomplished.
This answer goes into the formation of the wake and the wingtip vortices.
This answer shows why more wingspan reduces induced drag. It matters little whether the wingtips are turned up, down or continue straight: A larger wingspan reduces induced drag.

You will find that your picture of a tilted-back lift vector is correct, and indeed will a narrower wing experience larger tilting. Also, to achieve the same lift, a narrower wing needs more angle of attack and will create more induced drag. You are right again here, but instead of an ever increasing snowball effect, drag is just growing with the square of lift when the angle of attack is increased.

Ideally, all aircraft would have infinite wing span. But that would drive wing weight up a lot, so the designers settle for some compromise where the wing creates the least drag for a given net lift (total lift minus the lift needed to carry the wing).

Now to the questions in the comments:

  so the point of a higher AR ratio wing isn't to reduce vortices... It's simply to reduce the required AoA that is needed?

The point of a higher AR (more precise: More span per lift) is to involve more air in the creation of lift. This reduces the strength of the bound vortex, so indirectly it is about vortex reduction. The AoA reduction is not an issue here - in inviscid 2D flow an airfoil produces no drag, regardless of AoA. What does produce drag is the vortex flow field when span is limited.

  the reduction in vortices is simply how we see that it is working, per se?

Yes, reduced bound vortex strength results in reduced wake vortex strength.

  why do [designers] also care about the chord?

For that, allow me to refer you to this answer, and maybe this, too.

  Is it correct to say that we can measure the energy an aircraft loses due to induced drag by measuring the energy in the vortices?

Yes. But measuring the vortex strength is harder than measuring the downwash angle over span, which gives the same result. For viscous losses this is indeed a practical way of measuring drag by use of a wake rake (see the answers to this question for more).


What do these double Class Bravo airspace floor and ceiling limits mean? While browsing SkyVector I came across these double Class B airspace limits within the same section (is that what you call it?). I'm wondering what it means and what the difference is between this and FL145/SFC.

The way SkyVector shows airspace is subtly different than shown on FAA charts. Whereas the FAA shows the combined limits in each area, SkyVector shows the limits once for each layer, even where layers overlap.
So, what you are probably seeing here is one area of FL145/35 on top of another area of 35/SFC, possibly disjoint but the labels for both areas just happened to end up near each other. Or, it may be two areas with the same boundaries but different owners or airspace classes. As a result, it’s often difficult to figure out exactly which area(s) each label applies to.
Note that while SkyVector uses official maps from the FAA in/near the US, the rest of the world is computer-generated and not nearly as useful, especially since other countries often use airspace classes in vastly different ways that can’t be represented well in SkyVector’s pseudo-FAA style. Notably, they use blue for all classes, which often confuses folks used to the FAA’s color scheme.
According to the Spanish AIP, they are indeed two stacked airspaces; TMA SEVILLA AREA 3B and TMA SEVILLA AREA 3C. For example, in 3B (the higher one):

VFR traffic is not allowed, except for State aircraft, helicopters, medical and rescue flights.

Official e-chart here: https://insignia.enaire.es/


Why do sailplanes have such large tails? Since a sailplane is focused on performance - what with tricky laminar flow airfoils and all.
Eo why this

Instead of this

It looks to me like that long tail is needed to balance the cockpit. Buy then why not just put the wings beside the cockpit?
Even if we cannot use a flying wing, why not s least a shortened tail? Why this weight and drag penalty?

Keep in mind that not all sailplanes are designed for extremely light weight.  Decreasing the weight also decreases the minimum sink rate, but doesn't help the still-air glide ratio, and actually hurts the glide ratio against a headwind.
Even in sailplanes that are designed for very light weight, designers have sometimes thought it worthwhile to employ a rather large vertical fin.  A good example of this is the Carbon Dragon.
The basic purpose of a vertical fin is to prevent the aircraft from flying sideways through the air, especially when the pilot makes an aileron input, which tends to create adverse yaw.  Adverse yaw tends to be most pronounced in long-spanned, slow-flying aircraft.
Flying sideways is never efficient.
However, not all sailplane designers have always followed this philosophy.  The Scheibe Bergfalke is an example of a glider with a rather small vertical fin.  (Look closely at photos of this glider and you'll see that more than 75% of what appears to be the "tail" is actually the rudder, not a fixed vertical fin.)  When flown with the pilot's feet off the rudder pedals, it tends to be rather uncooperative in response to aileron inputs, being quite happy to fly sideways through the air rather than actually turning.
Keep in mind also that a given desired "tail volume"-- the product of tail area times moment-arm-- can be achieved with less drag with smaller tail on a long slender boom (rear fuselage), than with a larger tail on a shorter fuselage.  You've really asked two separate questions here-- "Why is the tail boom so long?", and "Why is the vertical fin so large?".  The first question is easier to answer than the second-- the tail boom itself creates relatively little drag, due to its slender cross-section and resulting low "wetted area".  To a first approximation, we can say that the tail boom is long so that the fin and horizontal tail don't need to be larger, to create the desired tail volume and flight characteristics.  In truth, the story is a little more complicated-- when we dive into the details of spiral stability theory, we find that extending the tail boom while keeping the "tail volume" the same actually does produce significant changes in the aircraft's flight characteristics, due to that fact that the airflow and "relative wind" are actually curved whenever the flight path is curved.1  This also means that for a given "tail volume", the drag reduction resulting from extending the tail boom and decreasing the tail area will be less in turning flight than in linear flight.
One reason that modern sailplanes are generally designed with much larger vertical tails than vintage sailplanes--or most single-engine general aviation aircraft-- is that the long slender tail booms used in modern sailplane designs have a very small cross-sectional area and thus contribute very little to the aircraft's yaw stability ("directional stability").  Nearly all of the required "weathervane effect" has to come from the tail itself.
Certainly the purpose of the long tail boom and large vertical fin is not to "balance" the weight of the cockpit.  Rather, the cockpit is placed in the optimum position to balance everything else.
Footnotes--

Re "the airflow and 'relative wind' are actually curved whenever the flight path is curved"-- another way to say this is to note that in curving flight, the aircraft is rotating as well as translating linearly, so at any given instant in time, different parts of the aircraft are moving through the airmass in different directions.  The instantaneous linear velocity at the nose and tail are different, and "tufts" or "telltales" at the nose and tail would not blow in the same direction.  Details of the effects of the curving relative wind are beyond the scope of this answer, but it may be interesting to compare and contrast the designs of competition-level radio-controlled model sailplanes versus "free-flight" model sailplanes.  Both have relatively long fuselages, but the former invariably have much larger vertical tails than the latter.  The latter must be designed to fly in stable circles with no pilot input, while the former are designed for good response to pilot control inputs.  The effects of the curving airflow in turning flight play a role in these dynamics.


Are there certain areas where a pilot can jettison his/her external fuel tanks? When a pilot feels the need to jettison their external fuel tanks, do they have to wait until they are above a certain area, or can they just drop them wherever they please?

This depends where in the world you are, over civilian US territory military planes chose to operate under the FAA FAR's (although they are not explicitly legally required to), as such its pretty cut and dry

  Sec 91.15 Dropping objects.

  No pilot in command of a civil aircraft may allow any object to be
  dropped from that aircraft in flight that creates a hazard to persons
  or property. However, this section does not prohibit the dropping of
  any object if reasonable precautions are taken to avoid injury or
  damage to persons or property.

Elsewhere in the world the rules may vary. There may also be rules about dropping tanks over open water due to their being residual fuel in the tanks.

This question covers what happens to them after they are dropped.

This thread would indicate that they are actually not dropped all that often.


Are any jet engines used in combat aircraft water cooled? Are any jet engines used in combat aircraft water cooled?

If they are not, and instead are air cooled, how can the engine ensure consistent cooling? Wouldn't the airflow passing through whatever radiator implementation it has be greatly affected by the airspeed? Consider low subsonic numbers with heavy maneuvering in a dogfight, vs. mach 2 sustained flight?

While I can imagine that variable air inlet for the radiator would change the airflow, I really have no idea how this would work.

I'm also aware that certain rocket engines, e.g. the F-1 allow the fuel itself to circle around the thrust chamber to cool it. Perhaps a similar system is used in jet engines.

Jet engines are cooled and temperature managed by the mass air flow itself which is used to surround and limit the boundaries of the flame, keeping it away from the burner can walls, and dilute the heat of the flame as it passes to the turbine (only a minority of the mass airflow's oxygen is actually burned - which is why afterburners work; there's lots of leftover oxygen to work with).

If you're talking about using a closed liquid cooling system with heat exchangers taking heat from the burner can and turbine somehow, well, I've never heard of a water jacketed burner can, and how you could use liquid in a closed system to cool a turbine, who knows.

Liquid cooling was used in the past as supplemental cooling to increase available power by spraying water directly into the mass flow as mentioned here, but in that case the water is a consumable.


Where is the center of gravity on a tiltrotor? From what I understand, the CG of full-sized fixed-wing airplanes need to be forward of the wing's center of lift for stability. But the CG of a helicopter must be directly below the rotors since it doesn't have a horizontal stabilizer to counteract the pitching moment.
So, where is the CG in a tiltrotor airplane (the kind that has its engines on the wings, such as the V-22 or the AW-609)?

The c.g. limits change in forward and hover flight, so loading the aircraft takes special care. On the Bell XV-15, the range of c.g. was around 16 inches. For comparison, the internal cabin was 157 inches long. Based on the fuselage stations below and the image above, the c.g. limits were very close to the rotors in helicopter configuration.
For the control method in-flight, see: How do VTOL aircraft like the V-22 Osprey not tilt?
Commentary: how much forward ballast (see image below) an aircraft like the V-22 has -- I don't know (classified).

Maisel, Martin, D. C. Borgman, and D. D. Few. "Tilt rotor research aircraft familiarization document." NASA TN X-62 407 (1975).


Why does the speed of commercial airliners fluctuate, sometimes as high as 1,060 km/h or as low as 800 km/h? I've noticed that (long-haul) airliners sometimes travel at as high as 1000  km/h (I believe I've even seen 1040 km/h), but usually they fly closer to 800 km/h, for most of the trip.  This seems odd to me.

I would understand this if it was due to wind speed; however, usually those that travel slowly seem to do so for most if not all of the journey, regardless of the direction of travel (e.g. even if they are going up to the north pole and back down, and whether the net direction is west or east). I find it nearly impossible to explain this using wind speed.

Similarly, given that the speed of sound is around 1,060 km/h at 12 km above sea level, I find it equally uncompelling to reason that they need to go at less than mach 0.8 due to the speed of sound. I would understand it if they limited themselves to (say) mach 0.95 (obviously you don't want to do mach 0.99 due to variability etc.), but I routinely see top speeds that are around mach 0.8 for cross-continental flights, and I don't understand why.

So, what's the real reason?

Information displayed to passengers through the entertainment system often gives the aircraft ground speed rather than airspeed.

Wind affects the ground speed, you're right about that.

Few things out of the way first.

Pilots do not use ground speed for flying, instead they use indicated airspeed.
Mach number is not derived from the ground speed, as it is dependent on air temperature, instead it is derived from the true airspeed. Notice we already have two kinds of airspeed. There are more still.
Aircraft type (for example 737 vs. 777) determines "top speed". Not all airliners are the same. Those two types range from Mach 0.77 to Mach 0.85, roughly.

In less words than Wikipedia which I linked:

Indicated airspeed tells the pilot the aerodynamically relevant speed to be used for flying.
True airspeed is the actual speed relative to the surrounding atmosphere.
From the true airspeed, add or subtract tail or headwind, and you get ground speed from that. Typical wind experienced by the regular subsonic airliner is fast (+100 km/h). The tail or headwind component would vary depending on the plane's direction and the wind's direction.
Finally, Mach number is a function of temperature and true airspeed (notice, not ground speed). The higher you are, the colder it is. Also very important, Mach number is a ratio, never a speed. Since the speed of sound varies as the atmosphere changes density and temperature at the different altitudes.

Here's a nice story, a 1200 km/h subsonic flight.

Summary:

Pilots don't use ground speed (for flying), mach number is not a speed.


In G1000, how can I intercept a victor airway with multiple legs? Suppose we are in HDG mode.

Trivially, we may visually judge which leg we on the victor airway and activate that leg.

However, in real-world, I found sometimes the fixes are so close and the airplane is relatively far from the airways. It is difficult to tell exactly which leg I am going to intercept, without "ruler" assistance. Meanwhile, ATC may change HDG assignments, and therefore the intercepted leg may change.

Is there a way to "activate the nearest leg and intercept" in G1000? or how would you solve this problem other ways?

If the airway is too far away to accurately determine which leg you are going to intercept, why would you let the G1000 pick the leg you are going to intercept?

You know best what you want and, as you say, ATC may change your heading anyway.

So you shouldn't intercept automatically until you are fairly sure where you are intercepting. Instead you remain in HDG mode which gives you full control and makes it easy when ATC instructs you to change heading. Then when you are a couple of miles from intercepting you select the leg and let the G1000 do the magic if you want to.

Automation is there to relieve you from difficult or boring tasks. If you find that you spend a lot of time programming your FMS, it may be better to reduce the level of automation and spend the extra time on situational awareness.

I recommend watching this America Airlines training video on automation dependency (a.k.a. "Children of the magenta line"). It addresses the FMS / autoflight dependecies for airline pilots. The video is over 15 years old and by now similar automation systems have entered the cockpits of small aircraft. Although some aspects of the video address a multicrew environment, the main points are equally valid for G1000 equipped single crew / single engine propeller aircraft.


Do I have a good CFI? I'm studying for my PPL and I've accumulated roughly 70 hours towards my PPL and am only now doing my cross country training.  Sometimes life gets in the way.

I am a fan of my CFI but had a situation this past weekend that has made me a bit uncomfortable - he fell asleep on 3 occasions during my first cross-country.  Is this a sign of a bad CFI?  Is it something to be concerned about?

I'm also wondering - is it important to know what you're going to be expected to work on before each lesson and we figure out what we're doing for the lesson during preflight?  Right now most of the agenda is being driven by me and I'm wondering if that's normal.

What's a good/bad CFI?

I'm a CFI/MEI.  I have 700-800 hours teaching private pilot students in the part 61 environment.  That's not an awesome amount but I think it's enough to comment on this question.

This guy is wildly unprofessional, maybe even criminally negligent.  You are paying him to observe you, to provide feedback, and to keep you safe.  He can do none of those things while he is sleeping on the job.

You have a lazy instructor and I'm curious to know in what other ways he is failing to teach you.

It's his job to excercise good judgement and scrub a flight if he's not up for it.  If he's overworked he shouldn't be flying.  That's his problem, not yours.  He has no excuse for his behavior and he's setting a terrible example for you to follow.  DO NOT be like your instructor.  I hope you're not using him as a role model for what a good pilot should be.

He's failing to demonstrate sound judgement and showing you that complacency is OK.
He's not challenging you or looking for teachable moments.
He's exhibiting classic hazardous attitudes...invulnerability and anti-authourity at a minimum.

I'd talk to him first and then fire him if this nonsense continues.  I'd also demand a refund on CFI billing for his nap time.

And, yes, there should be a defined lesson plan with expectations for each lesson.  This goes for pt61 and pt141 schools.  Every CFI should have created plans during their CFI training.  I have no idea how a CFI applicant can pass a CFI practical or oral exam without a comprehensive collection of lesson plans.

No, it's not OK for you to be in charge of what is covered.  You should know what the next lesson will cover so you can prepare.  He needs to give you the training plan and he needs to drive it.  Again, it's his job, it's why you pay him.

I think this guy is milking you for billable hours.  You might just be a cash pinata for him.  Either that or he's just incompetent.


Why does Ryanair always fill its flight plans with the same remark? With my current position, I have access to samples of ATC recordings, including all the flight plans received by a FIR. Parsing these recordings, I noticed that Ryanair always put the following sentence in both ICAO field F18/RMK and ADEXP field -RMK:

  PAX SCHEDULED FLIGHT CONTACT +353 IRISH PHONE NUMBER

Why does Ryanair do that?

Note: the field "flight type" is also filled, and contains the letter S for Scheduled, thus my surprise.
Note2: +353 is country code for Ireland where Ryanair is based.

It's a contact number for their "HQ". Putting it in the remarks ensures they are easy to get on the phone if necessary for any issue/emergency.

Regarding the redundancy of putting "SCHEDULED" in the remarks - I assume it's for the same reason - ease of locating information.


Why do some IAPs lack an Intermediate Fix and/or include other fixes between Final Approach Fix (FAF) and Intermediate Fix (IF)? I have noticed that some Initial Approach Procedures (IAP) do not mention an Intermediate Fix, but they do include at least one fix before the Final Approach Fix. Take, for example, this IAP of the JFK airport. It includes a Final Approach Fix (MATTR) but the one that precedes this (CORVT) is not labeled as Intermediate Fix. Is it always implied that the fix before the FAF is the Intermediate Fix? Another example is this IAP, also of JFK, where JAMCA appears to be the Intermediate Fix but, nevertheless, is not labeled as such.

In addition, there are some IAPs like this which neither include an Intermediate Fix, nor have the last fix (in this case, CEMUG) labeled as FAF. In this particular example, RUSHY, instead of CEMUG, is labeled as FAF.

Is there any rule which I am not aware of and that will help me clarify the above cases?

The rules are quite lengthy -- a 509 page PDF.  They're all spelled out in excruciating detail in the FAA Order 8260.3D, United States Standard for Terminal Instrument Procedures commonly referred to as the TERPS.

It's available for download here.

I would suggest researching your questions there, and returning here if you have a specific question regarding the application of the TERPS.


Can you climb at Vxse when you cannot at Vyse in a multi-engine aircraft? Let's assume that you took off in a seminole and had one engine suddenly failed, say, at 400 feet AGL. You right away pitch for 88 knots (Vyse) to keep climbing, yet you start to descend because the density altitude is too high. In this situation, would pitching up for 82 knots (Vxse) give me a chance to climb back? Or would it only give me a greater descent rate?

I'd recommend reviewing Chart 5-23 from the PA-44 POH - Climb performance one engine operating - gear up for specific numbers based on aircraft weight and atmospherics.

If you're not seeing a positive rate of climb at your best rate of climb, single engine airspeed, then you're not going to see it at the best angle of climb airspeed single engine either.  By definition, Vyse is the best rate of climb that you're going to see on a single engine; any other airspeed, including Vxse, is going to give you a lower rate of climb, or greater rate of descent if a positive rate is not possible.  And attempting to acquire and hold Vxse you're getting close to the reverse side of the power curve, combined with ever decreasing rudder authority, it would be easy to have the aircraft drop below Vmc and depart from controlled flight.


Who decided which airspaces not to fly through and how? I was looking at some flight paths, and I noticed that while some airspaces are ignored by planes for "obvious" reasons, like the Ukraine - Russian border airspace.

For example, this flight seems to purposely ignore the Ukraine airspace.

But on the other hand, I found some flight which are not ignoring airspaces which should probably be ignored. Like planes flying over Syrian airspace or over Yemen. These places too are war zones and might have militant groups capable of repeating something like MH-17.

This made me wonder as to who decides what airspaces to not fly over, and what are the criteria to do so?

One major driving factor is whether a permit is required. Many countries in the world require a permit even for overflight.

(source)

Depending on country to country, airline to country and general relations it may be more advantageous for a carrier to get permits in one country than it would be in a close neighbor. Going a bit out of the way (burning extra fuel ultimately) may be less costly than delays related to permit issues, etc.

In some cases there are also prohibited airspaces within a country. This is simply airspace you cant fly over for regulatory reasons (generally security). While some of these airspaces are small, some areas can be quite large in size.

While increasingly a smaller case not all aircraft are equipped to fly through all airspaces. Different regulating bodies may require different gear on board for a given flight. Aircraft may be prevented from entering a given airspace if not properly equipped or certified.

On any given day routes may be amended for weather or potential weather hazards.

As @mins notes in the comments, this answer covers areas avoided for safety reasons.


Which version of the FAA's Instrument Procedures Handbook is current? I'm looking for the current release of the FAA's Instrument Procedures Handbook. The FAA website for the IPH shows FAA-H-8083-16, but other FAA documentation I've found references FAA-H-8261-1A. I've looked for places to buy the Instrument Procedures Handbook such as Amazon and found that they're offering FAA-H-8261-1A.

Which one is current?

For future reference, how do I found the most recent release of an FAA publication?

8083-16 ,dated 2014, is current version, superseded 8261-1A. It is stated in Summary of Change.

For future reference, the FAA page you linked in the question is best resource available.


Why doesn't the 737 have a fuel dump nozzle? I was watching a documentary on aircraft incidents which mentioned that the 737 does not have the facility to dump fuel. Instead they're required to fly in circles to burn off excess fuel in an emergency.

It strikes me as a little odd, as someone without detailed knowledge of the 737-series' fuel systems, that the world's most popular passenger jet doesn't have this capability.

What was the design consideration/reasoning for this?

TesterMen Tester provided some very good information which I think requires a bit of explanation. The older version of the regulation seems to require fuel dump capability if MTOW is more than 105 percent of MLW. None of the 737 versions have weight limits under this requirement, so based on that regulation, it seems like fuel dump would be required. But as the Boeing info shows, none of the 737 versions have fuel dump capability.

That regulation was amended in 1968 to allow a plane to not have a fuel dump system as long as it can meet certain performance requirements. The current version of the regulation includes this as well.

However, this does not explain why the 737-100/200, which were certified before that amendment, don't have fuel dump capability, when the MTOW listed by the Boeing info above are 108% and 112% of the MLW.

The explanation is that the original versions of the aircraft had lower MTOW, which met the 105% rule. Newer engines allowed the MTOW to be increased, but as rbp mentioned, MLW is based on landing gear and structural limits, so it did not change. The FAA amended the regulation with the required performance option to allow the higher MTOW without requiring fuel dump capability. Also, as explained in answers to this related question, planes can land over MLW, there just may be required inspections.

Note that the similar-sized A320 family does not have fuel dump capability either. Smaller planes usually don't end up with the kind of fuel capacity and takeoff weights that justify a system to dump fuel.


What are the legal requirements for me to purchase an airplane that I will provide instruction in? I'm planning on getting my CFI certificate and I would like to purchase a Cessna 172 to rent to students and provide instruction in.

What are the legal requirements for me to do so?  Are there specific things I need to do beyond 100 hour inspections?

What is the best way to set something like that up to provide personal liability protection?

The requirement for 100 hour inspections is probably the biggest regulatory/legal item you'll come up against.

As for other regulatory items, there's some fuzz on the subject of whether providing the aircraft used in flight instruction and receiving compensation makes that aircraft "for hire" and triggers all the other FARs that come into play when operating an aircraft "for hire" (like the requirement for a working landing light, or the requirement for approved flotation devices if you're beyond power-off gliding distance from shore).

I could argue pretty convincingly either way (and there are some convincing arguments on the internet both ways), but I've not seen anything from the FAA that I would call definitive.
The safe interpretation would be to treat the operation as "for hire" unless you can get something in writing from your local FSDO or the FAA Chief Counsel's office saying that it isn't.
(Honestly the additional regulatory burden is really not that onerous - I mean don't you want a working landing light and life jackets anyway?)

As far as liability goes you're going to want to talk to an aviation insurance broker about at least three kinds of policies:

Insurance for yourself, as a CFI.
Insurance for the aircraft, as a rental aircraft/aircraft used for instruction.
"Renter's Insurance" for your students.

The first two cover you.  The third protects your students in case they damage the aircraft on a solo flight: your insurance company may try to recoup their loss from the student responsible for the damages (subrogation), and a (good) renter's insurance policy would cover such an occurrence, as well as paying for any other things which may have been damaged like airport lighting, parked aircraft, etc.

These insurance policies may also have additional requirements above and beyond those in the FARs.

Depending on your personal assets and the level of risk you're comfortable with an umbrella liability policy - either through your aviation broker or another broker/agent - may also be something worth considering (if you have such a policy written by someone who does not specialize in aviation make certain the policy does not have an aviation exclusion).


Is it true the F-16 has never lost a dogfight? (Source)

I have heard the F-16 has never lost an air-to-air dogfight - is this true?

migflug.com has a page for combat statistics for all the aircraft currently in use, from which:

The F-16 has 76 air kills, 1 air-to-air loss, and 5 losses to ground fire.

The one air-to-air loss (actually two F-16s colliding) was during the Aegean dispute:

  One of the routine interception maneuvers led to a fatal accident on 23 May 2006. Two Turkish F-16s and one reconnaissance F-4 were flying in the international airspace over the southern Aegean at 27,000 feet (8,200 m) without having submitted flight plans to the Greek FIR authorities. They were intercepted by two Greek F-16s off the coast of the Greek island Karpathos. During the ensuing mock dog fight, a Turkish F-16 and a Greek F-16 collided midair and subsequently crashed. The pilot of the Turkish plane survived the crash, but the Greek pilot died.

You may consider it zero since it was a "mock" dogfight.


What is the reason for changing the speed reference (IAS or Mach number) with altitude? Inspired by that question: How is the airspeed-Mach number transition handled in modern airliners?

When pressure and density decrease IAS also decreases. When temperature and pressure/density decrease speed of sound also decreases. As air pressure, density and temperature all decrease with altitude, if one fly a constant IAS or a constant Mach number while constantly climbing or descending, the aircraft actually constantly accelerates or slows relative to the air mass.

But at lower cruise altitude an aircraft will be piloted to maintain a constant IAS, while at upper cruise altitude a constant Mach will be flown.

Machmeter combined with airspeed indicator, source

What is the reason for changing the speed reference (IAS or Mach number)?

Aircraft are limited by both air speed (VMO, affects loads on the structures) and Mach (MMO, formation of shock waves resulting in buffet).

At low altitudes, the speed of sound is high so an aircraft is most limited by indicated airspeed (IAS). At higher altitudes, the speed of sound is lower so the aircraft will be limited by Mach number. Aircraft typically fly towards the upper limit of their speed, so at some point they will have to switch from remaining under the IAS limit to remaining under the Mach limit.

The chart below shows the changes in different speeds as altitude increases, assuming standard atmosphere.

Trend data source, speeds for 737-800

The aircraft climbs at 250 KIAS from sea level. An acceleration from 250 to 300 KIAS is included at 10,000 feet. You can see that as IAS is held constant, TAS (True Airspeed) and Mach both increase.

The switch from 300 KIAS to Mach 0.76 is done at FL280. You can see the Mach speed is approaching its MMO. From this point, both TAS and IAS decrease. After the tropopause, around 35,000 feet, temperature stops decreasing and TAS remains nearly constant.

At FL400 the aircraft levels off and cruises at Mach 0.765, and a step climb to FL410 is included at this speed to show the trends there.

More detailed charts and an explanation of IAS vs. Mach as it relates to climb and aircraft performance can be found here.