How do electric carbon monoxide detectors work? How does the electric carbon monoxide detector in cabin or cockpit on aircraft work?

There are three major types of carbon monoxide senors.

Biomimetic: A gel changes color when it absorbs carbon
monoxide.
Metal oxide semiconductor: When the chip's circuit detects
carbon monoxide, electrical resistance decreases, and this
triggers an alarm.
Electrochemical: Electrodes immersed in a chemical solution
sense changes in current when they come into contact with carbon
monoxide, and this change triggers the alarm.


Instrument approach DME VS instrument approch ILS DME what is the diffrence of Instrument Approach DME and Instrument Approach ILS DME?
Is it same as LOC DME APCH and ILS DME APCH?

The name for each approach indicates what equipment is required, so DME, ILS/DME and LOC/DME would all be different--and some aircraft may be able to fly one but not another.  Generally, the better (i.e. more precise) the equipment available, the lower the minimums can be because the obstacle clearance area will be smaller.


Is there a button that pilots push to transmit on the radio? Is there any button which needs to be pressed when the pilot or co-pilot wishes to talk to ATC?

Normally in videos on YouTube they don't seem to be doing anything special other than speaking, but I believe that there's more to it. Probably the push buttons (like on a walkie-talkie) are located very close to their hands?

I'm generally asking about all aircraft that communicate with ATC, not any specific airliner.

Please note that I know the handshake stuff and the frequencies and the radio part of it. My question is only about whether they do or they don't have a push button when they have to send a message. It doesn't seem to be an always on thing because obviously that would clutter up the channel and ATC guys don't need to listen to what the pilots are talking in the cockpit routinely.

There is a push to talk (PTT) button located at the yoke or sidestick, in small and large aircraft likewise. When the PTT button is not triggered, all communication is routed through the intercom and not broadcasted on the frequency. Once the button is triggered, communication is broadcasted on the active frequency.

In the below picture of a glider, it is located on top of the middle stick.
On the second picture is it behind the yoke, to be used with the index finger.

(Image Source: WikiPedia)

(Image Source: Private Blog)


What is boundary layer tripping? I came across the term "Boundary layer tripping" but I can't really underastand it. After searching on internet I cannot find any video or an image explaining that concept. Could you please explain what is "Boundary Layer tripping" with some figures/illustrations if possible?

I appreciate your help.

Tripping the boundary layer refers to the action of artificially transitioning a laminar boundary layer into a turbulent one. It can happen intentionally (via turbulator) or unintentionally (via imperfect aero-smoothness, such as rivets, bolts, counter-sinks). At the point of boundary layer tripping, the surface protrusion destabilizes the laminar boundary layer and causes the transition to occur earlier than via natural Tollmien-Schlichting instability.

The following is an example of a turbulator tape. It is attached spanwise along the surface of the wing (facing flat against the surface) at the desired chord-wise location where the laminar-turbulent transition is to take place:

Since turbulent boundary layer has higher skin-friction drag than a laminar one of the same Reynolds number, unintentional boundary layer tripping is undesired. That's why wing surfaces must be made flush and smooth. At the same time, since a turbulent boundary layer is much better at resisting flow separation than a laminar boundary layer, tripping the boundary layer can be used to improve stability & control at high angle of attack at the expense of increased skin-friction drag.


Why didn't planes land from the sea in the old Kai Tak Hong Kong airport? Reading up on the old Hong Kong airport Kai Tak, I'm left with the question as to why the planes didn't land from the sea?

I know that takeoff was done towards the sea, but is there any reason that you couldn't land from the same direction you take off? Or is this less feasible due to traffic?

It otherwise seems to me that largely congested airport areas could (have) benefitted from bi-directional use of the runways. And I don't think wind direction could have made much of an impact for Kowloon, given the mountains and skyscrapers everywhere.

This question seem to suggest that landing and takeoff in/from the same direction is not standard in aviation, but with very limited details.

Reading up on the old Hong Kong airport Kai Tak, I'm left with the question as to why the planes didn't land from the sea?

It's a small point, but Kai Tak was not next to the open sea but rather alongside Victoria Harbor. Most of the rwy 31 final approach was over the harbor but with mountainous terrain on either side. The rwy 13 final approach was over Hong Kong island, then Victoria Harbor, then Kowloon.

Both rwy 13 and rwy 31 were used for takeoffs and landings depending on the wind, and winds in Hong Kong were often strong right down to ground/water level. Generally the prevailing winds favored rwy 13. By that I mean that when tracking the runway just before touchdown or when taking off you would have a headwind component. However, because most of the time there was a crosswind, it often meant that when approaching for landing but before you made the 47 degree right turn from the IGS course to short final, you had a tailwind component.

Both runways could be very turbulent. If ceiling and visibility were poor, that always meant a rwy 13 approach, at least that was my experience. The worst turbulence, though, was in severe clear conditions to rwy 31 when the wind was coming off the Chinese mainland.

I have a blog item about operating into Kai Tak on my website. You can look at it here.


How can a sUAS operator contact ATC/identify themselves when contacting ATC? In a comment, abelenky offered some words of wisdom which I personally agree with regarding sUAS ops near a surface Class C:

  When in doubt or close, call Tower and state your intentions. They'll approve you, and if you cross into their airspace you will be legal. If you stay outside their airspace, you asked approval for no reason, but no harm done.

However, how should a sUAS operator contact an ATC entity that has jurisdiction over surface airspace (such as Tucson or Davis-Monathan Tower, in the querent's example)?  Should they place a phone call to the Tower phone number? Call the Tower on frequency with a handheld airband radio?

Further, is it even legal for a sUAS operator to use an airband radio in the US (i.e. does a commercial sUAS certificate count as a FCC aeronautical-mobile license the same way a regular PPL/... does)?  And if they were to call the Tower on the radio, how should they ID themselves/what callsign should they use, as I am not sure if a sUAS registration number is a valid radiotelephone callsign?

First, you should NOT transmit on air bands as a UAS pilot.  You do not have a ground station license and it would be a violation of both FCC and FAA rules, contact with the tower, when necessary, should be done via the phone.  It is fine (and I'd even encourage) to monitor the air bands relevant to the location you are flying in to be aware of on-going traffic.

How to approach contacting the tower depends on what you are flying your sUAS as.  LAANC (Low Altitude Authorization and Notification Capability) is now active almost everywhere, though some particular airports still do not use it.  LAANC should be used whenever available, however the traditional approach will still need to be used for any particular airports not yet participating in LAANC.

LAANC

If you are flying near an airport where LAANC is available, then you can simply use an app from your mobile phone to request flight authorization/notification.  You simply enter the area or flight plan you will be flying and hit the button to request approval and then wait for the notification it's granted.

This can be done regardless of if you are a part 107 pilot or a recreational pilot.  As long as you are flying below the maximum altitudes defined in the UAS Facilities Maps, you should receive near immediate approval in most cases.  If you are flying above these limits, you will need to be a 107 pilot and go through the traditional waiver process.

You can find a listing of apps that currently support LAANC listed on the FAA's website here.

Traditional Notification/Waiver

If the airport you are flying near does not support LAANC, then if you are flying for purely recreational purposes, you must provide notification to the airport operator and ATC prior to your flight.  You should use the telephone contact information to do this.  As long as they do not specifically deny your flight, you only have to provide notification.

If you are flying under part 107 (FAA certified remote pilot), you will need either an airspace authorization (easier to get and may be requested up to 6 months) or an airspace waiver (harder to get and may be requested for up to 2 years).  You should check the UAS Facilities Maps to find the maximum easily allowable altitude for your flight and submit the airspace authorization request online through DroneZone.

It is currently taking around a week or two for authorizations that fall within the UAS Facility Maps guidelines and longer if additional research is needed to get approval.  Authorizations are ONLY offered for airports not currently supporting LAANC as LAANC is the preferred means of processing.

One of the conditions of getting either a waiver or an airspace authorization is to provide details on how you intend to handle contact with ATC.  Contacting the tower via phone is the most general approach.  Some also monitor ATC frequencies so that ATC can more rapidly get ahold of them if needed.


What will create a "traffic puck" on the UAT band? I know that for ADS-B in the US to receive TIS-B information you need to be a participating aircraft (ie ADSB-Out).  My question is more specifically, if you are flying an aircraft with a 1090ES transponder and have a stratux or similar ADSB-In device for your phone or tablet, will the system create the traffic puck around your aircraft and send TIS-B information for you?

The answer is "yes" if

a) you configure your 1090 out system to request ADS-B uplink at 978 MHZ (this feature was added to the message structure in DO-260B)
b) your 1090 ADS-B out message is confirming certain minimum "quality" standards related to both the quality of the position information (GPS Integrity or "NIC") and the quality of the avionics (SDA or system design assurance)and the quality of the install or SIL  The specifics of what quality message triggers the system is under review by the FAA, but if you equipment is certified (TSO'd) and the install is in accordance with AC-20/165B you will be fine.

Note, if you have a UAT ADS-B you can specify which uplink frequency you want in the same way.

Further note - almost all ADS-B system are single band transmitters (ADS-B Out) and dual band receivers (ADS-B In).

Nuance - the uplink is broadcast to the quadrant (relative to the ground station) where you are flying.  This can lead to aircraft with no or "below quality" ADS-B out receiving traffic intended for another aircraft.  Depending on geometry this can create a partial traffic picture which can be quite misleading and potentially dangerous


Is this a wing-tip device on the A-10 "Warthog"? Source: Flickr courtesy of: U.S. Air Forces Central Public Affairs, photo by Master Sgt. William Greer

Notice at the side edges, the wing peels down and back around towards the fuselage. (The airplane is upside-down in this photo.)

Never noticed this before. Is this a wing-tip device producing more lift? If so, what kind is it? I would like to read more about it.

The wingtip devices used in A-10 Warthogs are called drooped wingtips (also called Hoerner wingtips in some cases), which essentially increase the aspect ratio of the wing by forcing the vortices further out.

Source: zenithair.com

There are a few reasons for having this wingtip device:

The drooped wingtips act in a manner similar to the winglets and reduce the induced drag. As a result, the loiter capability of the aicraft, an important one for Close Air Support (CAS) aircraft, is improved. The A-X competition, that lead to the A-10 develpment, required the aircraft to have Two hour mission loiter time at max mission radius with 9,500 lbs payload
The drooped wingtip increases the local span loading near the wingtip, due to which the aileron response is improved, increasing the manuverability at low altitudes. The A-X competition required the aircraft to be Highly maneuverable below 1,000 ft
The drooped wingtips also improve the takeoff performance, an advantage as the aircraft is expected to be operated from short, forward fields. Infact, drooped wingtips are found in STOL kit of some aircraft, like DC-2 Beaver. One of the requiremens of the A-X competition was that the aircraft should have 4,000 ft takeoff distance at MTOW.

As can be seen, the drooped (down) wingtips wingtips serves these purposes.

There seems to be some confusion regarding the reason for these wingtip devices. One theory (@Peter Kämpf) is that they are there to protect the ailerons from ground contact. However, I think this is unlikely, given the ailerons, when extended, go well beyond the wingtips, as shown below:

Source: scienceforums.net

Dropped down wingtips do serve that purpose (sometimes) in gliders. However, there is no reason to believe that is the case here, considering the height above the ground and the aspect ratio. The drooped wingtips, on the other hand serve to hold the countermeasure system.

Source: rcgroups.net


What prevents a passenger from hijacking a private jet? I was reading another question on this site when I saw this answer.

As you can see in the photo I copied below, this private jet has no cockpit door. On commercial aircraft the bullet-proof cockpit door is seen as the last line of defense against would-be hijackers.

What security measures are in place to prevent unauthorized passenger access to the controls of private jets? Even though they are smaller and carry fewer people, a G650 or BBJ pointed in the wrong place can do a lot of damage.

The same thing that prevents the passengers in your car from hijacking it and using it to run people down or drive it through a mall:  It's your private car and you generally know the people that you let in to it.

The same applies to private aircraft.


Why do the engine nacelles on the P2V Neptune extend so far back? I was studying a picture of a P2V Neptune seen from below, and what struck me was how far back the engine nacelles reach. Unfortunately, I can't find that original photo but this one shows what I'm talking about:

Image source
Unlike all the other piston-powered planes I've seen, the engine nacelles actually extend past (what I presume to be) the flap hinge line, ending behind the trailing edge of the wing. There is a noticeable gap in the nacelle to allow the rear part to rotate with the flap. Since the relatively flat radial engines don't even reach back to the leading edge, and the landing gear are situated far forward from the back of the nacelle, I don't see what advantage these elongated nacelles give. I doubt they help reduce drag, as they add surface area and don't end smoothly.

That shape was adapted after wind-tunnel tests showed the original less-tapered nacelle creating downforce, which meant the rest of the wing had to deal with more upward bending (lift distribution more toward the tips). To solve this problem, the beaver-tail-shaped end was used – reducing the flow separation that caused the downforce. The thrust-axis was also tilted 3 degrees down to reduce the overall bending moment (like how the weight of the fuel does that for big jets, here it's a tiny bit of downward thrust).
Nacelle-extension isn't unique to the P2V; you can find it on the B-25 bomber for example, although not as flat.

Wassall, J. B. "The Development of the Lockheed P2Y Neptune: A Paper by a Senior Engineer of the Lockheed Aircraft Corporation Describing the Evolution of a New Aeroplane." Aircraft Engineering and Aerospace Technology (1950). https://doi.org/10.1108/eb031906


What does a reduction gearbox do in a turbofan engine? I've read that the P&W PW1000G engine has a reduction gearbox. What is it and does it have any relation to the fan or compressor speed? Does it improve fuel efficiency?

The problem is that in bypass engines, the fan blades are much longer than the turbine blades that drive them. Both compressors and turbines should rotate as fast as possible, without shock waves occurring at the tip - so linear tip speed has an upper limit, meaning the compressor with longer blades must turn much slower than the turbine driving it.

This is what the geared turbofan does, reduces the rotational velocity relative to that of the turbine so that both can rotate at their optimum angular velocity. The forces involved and the required reliability make it not an easy design task, as noted in this answer,

  Does it improve fuel efficiency?

It does, when both the fan and the compressor can rotate at their optimum speed, and when the gearbox does not add much friction.


How are electronic systems locked and connected in the electronic bay? On aircraft the electronics bay contains multiple systems, e.g. for the A320:

A320, photo by B-2230, source: JetPhotos
How is the electronic equipment locked (it seems there are two mobile screws) and how are the wires connected? Details will be appreciated: standards, diagrams, images...

The LRUs are attached to trays which house the electrical connectors and the cabling behind them:

source

The hold down mechanisms vary in design, but it appears they generally attach the LRU to the tray at the front, the back likely being held in by the electrical connectors at the back.


Do pressure altimeters take into account differences in temperature? I work as ATC in Korea and recently, I have some question about winter altimeter setting.

In my facility, we use winter altimeter adjustment because the aircraft's pressure altitude is lower than true altitude in winter. I know this is due to air density difference in winter and summer.

My question is, can the altimeter setting (inch or QNH) include this adjustment? I know that the altimeter setting which ATC gives to the pilot changes every time according to the ground QNH condition. If the altimeter setting can include the adjustments, it would be convenient to ATC and pilot.

You can't just adjust the QNH setting to compensate. The temperature adjustment is not linear. The error increases with altitude, so when the altimeter is set for QNH the error at field level is zero. But it increases the higher you go. It's not just everything being X number of feet higher or lower.

In your question you say "the aircraft's pressure altitude is lower than true altitude in winter." That's backwards. The actual altitude is actually lower than what is indicated by the pressure alt. This can run the risk of colliding with terrain if the pilot doesn't adjust. In fact, exceptionally hot weather causes an error also, but in the opposite direction. The reason this doesn't need to be compensated is because the actual altitude will be higher than indicated so it doesn't create a danger of hitting terrain.

From answers to another question an aircraft with an FMS can be set to automatically adjust.

The problem seems to be in who's responsible for making the adjustment (ATC or pilot) and being clear on whether the altitude announced is adjusted or not. According to the answer from wbeard52, in the US the FAA has established a list of airports with cold weather procedures that require the pilot to do the compensation and announce the corrected alt to the controller. According to Sami's answer, in the EU the controller makes the corrections under radar coverage, and the pilot makes the correction without. It would appear from your question that in Korea they have decided to have you make the corrections as controller.


What precautions should I take when flying over a mountain? I would like to go on a photo flight over Mt. St. Helens sometime while I'm in the Portland area.  I am aware of the weather conditions that are caused by mountains - but what precautions should I take to make sure that my flight over the "summit" is as safe as possible.

I think it's worthwhile to mention that there is a wilderness area over Mt. St. Helens, so I will be above 2000ft AGL.

When flying over mountains Pilots will have to encounter unpredictable winds, high density altitude, steeply rising terrain and box canyons, mountain waves, rotor clouds, turbulence, and clouds covering high ground .

http://www.swaviator.com/html/issueAS99/basics.html

It is therefore essential to take the below mentioned factors into consideration :

(1) ROUTE PLANNING : When flying over mountains Route Planning is extremely important because a straight line between two points may not always be the best way to go . Therefore, pick a route that avoids the rugged areas and highest peaks where an emergency landing could not be made. It usually takes very little extra time to bypass the most mountainous areas and follow major roads through more populated areas and lower terrain .

Do not approach a ridge until you have sufficient altitude to cross with a safety margin. If you encounter too much sink, you must have enough altitude to turn away towards lower terrain. To make that turn as easy as possible, its wise to turn your aircraft to a 45-degree angle to the ridge before you cross .

http://www.avweb.com/news/airman/190015-1.html?redirected=1

(2) THE TERRAIN FACTOR : The rising terrain will often out climb non-turbocharged aircraft. If your aircraft has a service ceiling of 14,500 ft., that is based on standard atmospheric temperature which is 59 °F at sea level and decreases an average of 3.5 °F per thousand feet. If the surface temperature at 5000 ft. is 100 degrees, the density altitude on the ground is about 9,000 ft. When you climb to an indicated altitude of 9,500 feet you have reached the service ceiling of you aircraft.

(3) THE WIND FACTOR : In a light aircraft, it is best to stay on the ground if the winds are greater than 35 miles per hour. Due to the venturi effect, winds will be much greater in the vicinity of mountain passes. Cross passes as high as possible, as downdrafts up to 2,000 feet per minute can occur on the leeward side.When strong winds of 40 to 50 miles per hour are blowing perpendicular to a mountain range, expect mountain waves and strong downdrafts for many miles on the leeward side.

(4) THE CLOUD FACTOR : The combination of rising ground and lowering ceiling can be deadly. Mountains disappear not only in clouds, but also at night. You should not fly over high territory after sunset unless you are at the minimum en route IFR altitude which provides a 2,000 ft. clearance along airways. When flying after dark, closely monitor your altitude and when in a turn, your rate of descent.

A mountain checkout flight is all that is required to get started. The checkout will enable you to operate around some pretty impressive terrain :

Flatlander Focus : Two good books on the market are The Mountain Flying Bible by Sparky Imeson, and Flying the Mountains: A Training Manual for Flying Single-Engine Aircraft by Fletcher Fairchild Anderson. Reading either one will give you a solid foundation on which to build your skills.

Most Importantly - Know Your Aircraft & Its Limitations

http://www.caa.govt.nz/safety_info/GAPs/Mountain_Flying.pdf

(a) What distance over the ground does your
aircraft cover in a rate-one turn?

(b) What’s the distance for a steep turn?

(c) What speed and configuration do you use for reduced
visibility and for a minimum radius turn?

(d) What is the best-angle-of-climb speed?

(e) Do you know the manoeuvring speed (VA) and
understand its application in potentially
turbulent conditions?

(f) How is your aircraft performance and handling affected by
altitude and turbulence?

(g) How is performance affected when operating at
maximum-all-up-weight?

Needless to say recent practice and currency are vitally important.


How is vertical speed managed in Airliners? When an Airplane starts to take off, the Horizontal velocity would generate it the necessary lift, and then Airplane pitches up to further increase the lift. As the Airplane is climbing up, the net vertical force on it should be the difference of lift and its own weight. When there is a resultant force, should not the climb rate be ever increasing? And when the Airplane reaches the desired height, I'm assuming - either the horizontal velocity is decreased or Airplane goes to normal state from Pitch-up position, basically balancing the lift with own weight. At this moment, Airplane has some vertical speed right, So Isn't the Airplane supposed to be climbing up with a constant velocity, even after reaching desired rate, as Objects continue to move in the same velocity when there exists no force on them? How is this managed in Airliners?

Vertical speed is managed, primarily, with controls.

Lift is proportional to square of speed and to angle of attack¹ and angle of attack can be adjusted using the elevators. Pilot, or automation, use those to control the flight path of the aircraft.

As the aircraft accelerates along the runway, at some point the pilot pulls on the control column, which turns the elevators up and the resulting downforce on the tail lifts the nose off the ground². That increases the angle of attack—because the aircraft is still moving horizontally—, lift exceeds weight and the aircraft accelerates upwards.

As it starts to accelerate upwards, the pilot eases the pull on the control column to prevent the aircraft pitching up further. And as the aircraft accelerates upward, the angle between direction it is flying and pitch—that is the angle of attack³—decreases again, until the forces get in balance. Then the aircraft is in steady climb.

When the aircraft reaches the top of climb, the pilot⁴ pushes on the control column. This causes the aircraft to pitch down, which reduces the angle of attack, and thus lift, and the aircraft starts to accelerate downward, that is slow down the climb. At the point the aircraft is moving horizontally, the control column is pushed back to get the forces back in balance.

Now for the details of operating the controls, the longitudinal stability comes into play. Aircraft are normally⁷ designed to be longitudinally stable. That means the aircraft will pitch up as its angle of attack decreases—which increases it again—and pitch down as its angle of attack increases—which decreases it again. Net result is that when the elevators are left alone, the aircraft will maintain specific angle of attack.

As the aircraft climbs, it will tend to slow down unless engine power is increased, because its potential energy increases and it will be taken from kinetic energy if the engines are not providing enough⁸. And as it will slow down, its lift will decrease, so its angle of attack will increase, but that will cause it to pitch down due to stability. The net result is that it will refuse to climb unless enough power is provided.

Similarly when it descends, it will tend to accelerate, because the potential energy will be converted to kinetic⁹ and that will increase lift, which will decrease the angle of attack and the stability will make the plane pitch up. So it will refuse to descent unless power is reduced.

So in the end, vertical speed is actually managed by thrust levers. Which is also much more easily proven from law of conservation of energy.

¹ Up to critical angle of attack, where stall occurs.

² This is called rotation.

³ Angle of attack is properly defined as angle between the relative wind and the chord line of the wing, but aircraft axis is often used in practice. This makes things simpler as you don't have to consider the angle of incidence—angle between the aircraft axis and wing chord—especially since many aircraft have twisted wings where the angle of incidence changes along the span.

⁴ Or more often the autopilot. While take-off is always flown manually, up above FL290⁵ use of autopilot is required as it gets too tiring and unreliable to maintain the altitude by hand with enough precision to ensure separation⁶.

⁵ Flight levels are defined by pressure corresponding to given altitude, in hundreds of feet, on a standard day. So FL290 is 29,000 ft, but more when it is warm and less when it is cold. The reason is that pressure can be measured easily and quite accurately and flying at sufficiently different pressures ensures the altitudes are also different.

⁶ Originally the minimum separation was 2,000 ft above 29,000 ft due to the lower accuracy of altimeters and lower accuracy of flying as the aircraft move faster in the thinner air up there. But because all the aircraft wouldn't fit up there with those separations, 1,000 ft was allowed provided the aircraft is flying on autopilot and has sufficiently accurate altimeter. This is called reduced vertical separation minima

⁷ Some fighters are intentionally designed as unstable, because it allows faster control response. All such aircraft have computerized controls that compensate this, otherwise it would be very tiring to fly.

⁸ Alternatively, consider that the lift vector is tilted aft, and thus has bigger aft component, which is drag. Physics always has multiple ways to analyse a situation.

⁹ The lift vector is tilted forward in descent, so there is some forward component that accelerates the aircraft.


Can we borrow Formula One's ground effect for airplanes? (Source)

Inspired by the now banned late 70's F1 ground effect, I wondered if it can be adopted by airplanes. So, I came up with this:

(Own work)

The system

A belly door that opens at slow speeds and leads to a narrowing cavity—inverted diffuser.

In essence, the same as the F1 image above, but enclosed since there's no ground. And inverted since we need lift, not downforce. An F1 car's ground effect is the opposite of a plane's ground effect. The door is to stop its operation at high speed.

Theory of operation

The narrowing cavity will speed up the air, the air in the cavity thus will lose pressure (potential energy tuned into kinetic), the air outside the plane and underneath the cavity will be higher pressure, forcing the plane up.

There's no mission, just an experimental racing Howard Hughes kind of thing.

The engineering why is higher top speed, and low angle of attack slow flight.

The way I see it at slow speed the center of lift will shift aft, thus lowering the required angle of attack, I'm not sure about the longitudinal control authority and stability though.
Also, there'll be no need for high-lift devices and their associated systems, and possibly shorter wings, thus shedding weight and increasing top speed.

Can it fly? Are the assumptions above correct?

Engine location, nose gear location, etc., are not part of the question, just a pure aerodynamics question if we can make a cavity produce lift.

The reduced pressure on the car not only exerts a downward force on the car, but an equal upward force on the ground. Mythbusters did an episode where they drove an Indy car over a manhole to show that it does lift the manhole cover slightly.

The force on the ground is irrelevant because it doesn't move and is not attached to the car. But in your drawing the same thing is happening. The reduced pressure exerts an upward force on the bottom of the channel and an equal downward force on thing top of it. They cancel each other.


How can two private pilots flying together log time and split costs legally? I'm a new private pilot and I've got a neighbor who would like to do some flying in his personal Cessna 172G.  He is a private pilot as well and I am wondering how the regulations apply.

If he sits at the controls as a pilot (not a passenger) and pays for all of the expenses of the flight is that illegal? Even if I am PIC, do the regulations have be considered under pro rata, even he is not a passenger? I'm confused on how the regulations cover this.

He'll also cover the expenses of me flying with a local CFI to get checked out in his 172G, since I built all my time in Citabrias.  I'm confused about the regulations and don't want to do anything that may jeopardize my license.

As far as the arrangement goes, building time would be the closest thing that I could think of. It's his aircraft and he said he would be willing to pay for everything. This could include just local flights, getting a feel for the 172 and building time. I would think he would allow me to borrow it to fly solo as well, once he feels comfortable with me doing that. If it's the two of us just flying around, does it just become a matter of who is PIC? If we discuss that he's PIC and can take over any time, but lets me fly a lot does pro rata still apply? If he's always PIC, then he has to pay at least his share, but could cover all costs. But how does that leave me for logging any time? I'm unsure on how the regulations consider this, since we're both private pilots at the controls.

Short answer: if your neighbor acts as PIC, then he can pay all the costs and you can both log PIC time for however long you were sole manipulator of the controls. But you have to avoid becoming his personal pilot, because then you're getting into commercial territory.

As background, remember that acting as PIC and logging PIC time are different things. And I'm assuming that you're going to fly VFR only, i.e. there are no IFR and/or safety pilot issues (we have a few questions on that already), and that you're both fully qualified to act as PIC (medical, currency etc.).

First, logging PIC time. 14 CFR 61.51 has the rules, and the key one for your scenario is:

  (e) Logging pilot-in-command flight time. (1) A sport, recreational,
  private, commercial, or airline transport pilot may log pilot in
  command flight time for flights-

  (i) When the pilot is the sole manipulator of the controls of an
  aircraft for which the pilot is rated, or has sport pilot privileges
  for that category and class of aircraft, if the aircraft class rating
  is appropriate;

That means, when you're actually controlling the aircraft then you can log PIC time, regardless of who's acting as PIC. For example, if your neighbor has the controls for 0.5 and then you take them for 0.5, you can each log 0.5 PIC time. But in a single-pilot operation, only one person can log PIC at a time.

Second, sharing costs. Because a C172 is a single-pilot aircraft, if your neighbor is acting as PIC then you're a passenger. Note the wording in 61.113 (emphasis mine):

  (a) Except as provided in paragraphs (b) through (h) of this section,
  no person who holds a private pilot certificate may act as pilot in
  command of an aircraft that is carrying passengers or property for
  compensation or hire

  [...]

  (c) A private pilot may not pay less than the pro rata share of
  the operating expenses of a flight with passengers, provided the
  expenses involve only fuel, oil, airport expenditures, or rental fees.

As you can see, if your neighbor is acting as PIC he must pay at least 50% of those specific costs so he can always pay 100% if he wants; that just comes down to what you agree with him. If you act as PIC then the reverse applies: you must pay at least 50%.

Third, whatever arrangement you have with your neighbor, make sure you don't become a de facto personal pilot. If he starts asking you to fly him places he needs to get to, or even to just accompany him on flights because he isn't comfortable alone, then you should be very cautious. In theory, if he always acts as PIC then it's OK because you're just a passenger. But if there's an accident and the FAA has a reason to believe that he wasn't genuinely acting as PIC then you'll both be in trouble. To take an 'extreme' example, let's say he breaks his leg and asks you to fly him somewhere, with him paying all the costs. He couldn't be acting PIC because of his injury (61.53) therefore you would be acting PIC without paying any costs. That's receiving compensation for carrying a passenger and it requires a commercial certificate.

Finally, a couple of practical points to think about:

Two pilots in a single-pilot aircraft can lead to confusion and even accidents. Make sure you have a good pre-flight briefing that includes who is acting as PIC, and in flight always do a clear exchange of controls. And decide up front what happens in case of an emergency, like engine failure: does the person flying keep flying, or does your neighbor always take the controls?
You should have appropriate insurance. Even if he puts you on his policy as a named pilot you might still have to pay thousands of dollars as a deductible in case of an accident. If you don't already have it, it might be worth getting your own non-owned insurance to cover that, but it all depends on the details of the policies. If you're an AOPA member they can probably help you out with that.


What is the missed approach procedure when initiated below MDA/DA/DH? Let's say you continue below the DA/DH on an IAP because you have the APL insight; and of course no lower then 100 ft above TDZE.

Now you arrive and don't see any required visual cues to continue to land.

When would you decide to go missed on an ILS? since you already descended below your DA
If you were to execute a missed procedure below the DA/DH on the same scenario above are you assured obstacle clearance? (my thoughts are no, obstacle clearance is only assured if its executed at the MAP, at or above MDA or DA/DH with a 200ft/nm climb)

When would you go missed if below MDA/DA(H)?

You're only allowed to operate below the MDA/DA(H) if all of the following are true (14 CFR 91.175(c)):

You can land using normal descent rate and maneuvers
You have at least the flight visibility required for the approach
You have at least one visual reference from the list (not just the approach lighting system)

91.175(e) says that you must go missed if those conditions are not met and you're below the MDA, at the MAP, at the DA/DH, or "at any time after that until touchdown", i.e. below MAP/DA(H). Essentially, if any of the conditions in 91.175(c) are no longer true, then you have to go missed immediately. Practically, the most likely issue is seeing the runway environment, but you should also go missed if your approach is unstable, for example.

On an ILS approach specifically, that would most likely mean that you saw the approach lights at DA/DH (or above), followed the glideslope down to 100' above TDZE, but then didn't see any more visual references. That should be very unlikely if you really do have the flight visibility required for the approach but I'm sure it could happen somehow, e.g. there's ground fog in the wrong place at the wrong time. Or something else could go wrong: the runway lighting completely fails because of a power cut, or there's an obstruction on the runway.

Is obstacle clearance assured if going missed below MDA/DA(H)?

No. The Instrument Procedures Handbook (chapter 4) says several times that if you go missed below MDA/DA(H) then you have no guarantees and it gives some general advice on what to do:

  If the aircraft initiates a missed approach at a point other than the
  missed approach point, from below MDA or DA (H), or on a circling
  approach, obstacle clearance is not provided by following the
  published missed approach procedure, nor is separation assured from
  other air traffic in the vicinity.

  [...]

  In the event a balked (rejected) landing occurs at a position other
  than the published missed approach point, the pilot should contact ATC
  as soon as possible to obtain an amended clearance. If unable to
  contact ATC for any reason, the pilot should attempt to re−intercept a
  published segment of the missed approach and comply with route and
  altitude instructions. If unable to contact ATC, and in the pilot’s
  judgment it is no longer appropriate to fly the published missed
  approach procedure, then consider either maintaining visual conditions
  (if possible) and reattempt a landing, or a circle−climb over the
  airport.

This part is directed at pilots using night vision systems, but it looks like good advice for any pilot considering going below MDA/DA(H):

  If a pilot initiates a go-around at a point below DA/DH or after the
  MAP, obstacle clearance is not necessarily provided by following the
  published missed approach procedure. Prior planning is recommended and
  should include contingencies between the published MAP and touchdown
  with reference to obstacle clearance, aircraft performance, and
  alternate escape plans.


Do the compressors and turbine rotate at the same speed? Since the turbine and the compressors are connected to each other via a common shaft, do they both rotate at the same speed. Because I've read that in some jet engines (single spool engines) they don't rotate at the same speed:

  Single spool jet engine. These are those jet engines who have one shaft inside them. The compressors and turbines rotate on a same shaft. The speed of compressors and turbines decreases half way down the compressor stages, that is why they can’t match the local airflow. The various turbines and compressors is forced to rotate at same speed which lead to their inefficiencies.

(quora.com)

Is this true?

That's one badly-worded quote:

  Single spool jet engine. These are those jet engines who have one shaft inside them. The compressors and turbines rotate on a same shaft.

Correct. In a single-spool engine, all of the compressor and turbine stages rotate at the same speed because they're attached rigidly to the shaft.

  The speed of compressors and turbines decreases half way down the compressor stages, that is why they can’t match the local airflow.

No, the speed of the compressors and turbines doesn't change. It's the airflow that changes, and causes a mismatch.


What is the material of snubber brakes? What is the material of snubber brakes that is used for stopping the spin of the nose landing gear? KC-135, Boeing 747, 727 are the aircraft that I saw with these snubbers.

This company provides brake components for the B737,
the snubber brakes being among them:

 (Source)

They are made of what they call "AFT 200" material, which is described as:

  a phenolic treated, brass wire inserted cloth laminated under heat and pressure to a dense, strong composite. AFT 200 provides good fade and wear resistance and may be machined using standard, industry accepted practices. Its high strength makes it suitable for gear and lug driven applications.

I don't know if the snubber brakes in a KC-135 Stratotanker use this material as well, but the following picture shows where they would be installed:

 (Source)


Why does the bottom part of an aircraft nose curve upwards? As you can see in this picture the bottom of the fuselage curves upwards to form the nose.

Having the tip of the nose in the centre gives best combination of aerodynamic performance, weight and internal volume. If you move the tip down, the slope above it will either be steeper, leading to higher drag, or longer, leading to greater length and thus weight; or you don't extend the plane, but then the longer sloped part will provide less internal volume. Only the cockpit windows, which need to be on the sloping part, shift the nose a bit down, to the centre of the cross-section just before cockpit.

Cars are different. For a car you want the bottom surface flat, because you don't want to push and compress air in the gap between the vehicle and the ground. But aircraft has air all around and it is most efficient for it to push air equally to all sides, so a circularly symmetrical shape works best.

Also note that lift is yet another thing. Lift requires a sharp, downward-sloped trailing edge.


What are the differences between third-party base maintenance, line maintenance and component maintainance? These are related to MROs(Maintenance, repair and operations) activities ?

Base maintenance: The maintenance work is done in a hangar, with special tools and equipment. Third-party just means that someone else than the operator of the aircraft is running the shop.

Line maintenance: The work is done on the flight line, basically on the apron out in the open.

Component maintenance: The work is done on some component that had been removed from the aircraft before. Typically, this item had been swapped against a good one in line maintenance and is now looked at in detail in a specialist shop. Items like this are called LRU (line-replaceable unit). Components could also be as large as a whole engine which needs to be serviced in a special shop and is removed during base maintenance.


If a pilot license is revoked by a country's aviation authority, can the pilot still obtain another license? There was a recent new story of a Kuwait Airways pilot that got his license revoked after an investigation into an incident on an international flight where unauthorized persons were allowed on to the flight deck.

You can read more about the actual incident here.

Can this pilot still obtain another license to fly commercially?

It depends on the regulations in force. Usually, depending in the reason for revocation, the pilots can apply for recertification after a set period (usually one year) where they have to go through the whole process again. For example, according to 14 CFR 61.13,

  (d) Application during suspension or revocation.

  ...

  (2) Unless otherwise authorized by the Administrator, a person whose pilot, flight instructor, or ground instructor certificate has been revoked may not apply for any certificate, rating, or authorization for 1 year after the date of revocation.

It appears that these pilots too, can get another certificate after an year. According to Kuwait Civil Aviation Safety Regulations, Part 1,

  1.2.11 Surrender, Suspension or Revocation of License, Certificate or
  Authority

  ...

  3) Unless the order of revocation provides otherwise, a person whose
  License/ authority /certificate is revoked, may not apply for any
  License, certificate or authority before the elapse of one year from
  the date of revocation.


Does wing sweep affect the direction of lift? Given both a straight and swept wing (identical otherwise), exposed to the same airflow, would the direction of lift be the same? Please see below a crudely drawn example of my thinking.

Additionally, as angle of attack is defined as the angle between the airfoil's chord line and the direction of oncoming flow, is there a name given for the angle between the span line and direction of oncoming flow?

The Lift on an aircraft is the vector sum of one component of the aerodynamic forces pressing on the surface of the aircraft as they are distributed over the surface of the aircraft. At each and every point of the aircraft surface (top, bottom, sides, everywhere) the air is pressing on the surface normal, (perpendicular) to the 2-D surface. The vector sum of all these forces is the total aerodynamic force (**one component of which is lift). If the aircraft is laterally symmetrical, then of course the total vector sum will be straight up (as any lateral component from one side of the aircraft should more or less be counteracted by an equal but opposite lateral force from the other side.

The individual forces (acting on each point of the surface, including the wing), if pictured as a distribution of force over the surface, are always normal to or perpendicular to the surface. So if the wing has dihedral, then they are indeed angled in towards the fuselage. But in your "perhaps?" illustration, with a wing with zero dihedral, they would all be pointing straight up.

** The Lift component is the component of this aerodynamic force which is perpendicular to the flight path of the aircraft, the Drag component is the component parallel to the flight path.


Why do low wing aircraft have higher dihedral than high wing aircraft? I have noticed and read in books that low wing aircraft have higher dihedral than high wing aircraft. Dihedral is design feature for lateral stability so should be needed for both designs. So why is it more pronounced in low wing designs?

There are several sources for a sideslip-induced rolling moment:

The dihedral angle $\nu$ of the wing, which will increase the local angle of attack $\alpha$ on the windward wing according to $\Delta\alpha = \beta\cdot sin\nu$; $\beta$ being the angle of sideslip,
The sweep angle $\varphi$ of the wing, which in a sideslip causes a de-sweeping of the airflow over the windward wing (and an increased sweep effect on the leeward wing). The local change in angle of attack is $\Delta\alpha = (cos(\varphi±\beta)-cos\varphi)\cdot(\alpha-\alpha_0)$ and is proportional to the angle of attack,
The crossflow around the fuselage (see sketch below for illustration, sorry, no simple formula here), and
The location of the vertical tail, or more precisely, the side force created on it by a sideslip angle in relation to the location of the center of gravity. This effect dictated the anhedral of aircraft like the F-104 Starfighter.

Please see this answer for a more complete explanation of effect 3. The sketch below is taken from the linked answer and shows a high and a low wing configuration in sideslip. The thin blue arrows indicate the sideways component of airflow $v_{\infty}\cdot sin\beta$.

In the end, some rolling due to sideslip is good, but too much must be avoided, and dihedral is used to complement the other effects such that the total is just right. A high wing already provides some positive rolling moment due to sideslip (negative $c_{l_{\beta}}$: When you deflect rudder to the left, the resulting sideslip should roll the aircraft to the left, too), so the wing doesn't need to contribute as much (by means of dihedral) as in low wing aircraft.

Dihedral (or for that matter, even a low center of gravity) will not roll the aircraft level: There is no aerodynamic way to achieve that! Dihedral will only give you a rolling moment when the aircraft sideslips.


If an aircraft does not have an FDR, must one be installed to comply with Flight Data Monitoring requirements in EASA countries? Flight Data Monitoring (FDM), which analyzes FDR data to accomplish things like ensuring that pilots are following SOP's, is a requirement for EASA's Third Country Operators (TCO) certification, however certain (older) aircraft do not seem to require an FDR.

Does this effectively change the requirement so that an FDR must be installed in an aircraft in order to accomplish FDM or is there an exception for FDM as well?  I have been unable to find anything specifically addressing this.

For 20 PAX and more, it becomes mandatory.

https://www.lepoint.fr/sport/le-piper-malibu-un-avion-delicat-22-01-2019-2287804_26.php

  Les boîtes noires sont obligatoires sur les appareils de transport public d'au moins vingt sièges.


Do Cargo fly very short routes? Let's say that a package has to travel from point A to point B. These places are not located in the same Country, nor are such Countries adjacent to each other. Example: point A is in Italy, point B is in the United Kingdom.

The package is not delivered directly. From tracking info made available by the Company, you find out the package leaves point A and reaches Rome. Then it reaches Bologna, and later Dusseldorf, Germany. It then reaches Barking, in the United Kingdom. From here, it reaches Tamworth and then gets delivered to point B. These legs are pretty short, if you map them, so my question is:

could the package have traveled by air in any of such legs? or do Cargo companies prefer other means in this situation?

EDIT

I am not referring to the use of wide body aircraft on short-haul. Rather, I want to figure out if contracting out the delivery of goods over short-haul routes is a common practice among Cargo airlines. If this is true, how could a given package remain within the network of the Company?

It's fairly common for cargo, freight, and mail to be carried by aircraft - particularly for high value or priority cargo.

For example Royal Mail (the primary British mail service) uses short haul flights for distances of less than 100 miles (London Stansted to East Midlands Airport), along with around another 10 flights within the UK, every night.

These flights are used for priority (next day) mail, but will be filled with "cheaper" mail if necessary.

It all depends on the value of the cargo and the speed which it needs to travel, and aircraft only tend to be used where it is profitable to do so (ie where the cargo needs to travel fairly quickly and they can charge a high price to justify that).

Generally trucks will be used for shorter distances (<500 miles) for low value cargo, and for longer distances for heavier cargo or cargo which does not need to travel quickly.

http://www.eastmidlandsairport.com/emacargo.nsf/content/customer_royalmail

https://en.wikipedia.org/wiki/Royal_Mail#Fleet


How does downwash change relative wind? I have a question regarding the production mechanism of induced drag.

I understand the downwash aft of the trailing edge (steaming from wingtip vortices) causes the induced drag by changing the relative flow (blue line) into the effective relative airflow (red line), and thus by bending the lift vector rearward (L to Leff).

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

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

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

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

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

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

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

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


Why does elevator input move the turn coordinator ball in steep turns? When practicing steep turns, I'm running into an unusual phenomenon.  If the airplane is losing altitude in coordinated flight and I apply aft stick pressure to pitch up and correct, I notice that the ball swings to the outside of the turn indicating a skidding condition.  Conversely if the airplane is gaining altitude and I release back pressure to the stick to descent, the ball always swings to the inside of the turn, indicating a slip.  This seems counter intuitive as one would think that an increase in AoA to gain altitude would result in increased adverse yaw, requiring more rudder pressure in the direction of the turn and less rudder pressure when the nose is lowered resulting in a lower AoA and adverse yaw.

I suspect the reason here has to do with the direction the nose is being forced in by the elevator input during the turn.  At a steep bank angle the nose is inadvertently being pulled inside the turning flightpath which results in a skidding condition, which should, therefore, be countered by less rudder pressure in the direction of the turn.  Conversely when elevator pressure is reduced, the nose would tend to stray outside of the tangential flightpath, resulting in a slipping condition.  The end byproduct of this would be reduced or even cross control inputs needed to maintain coordinated flight.  Can anyone else confirm this?

In a steep turn you are making power changes, pitch changes and also making constant corrections with aileron to hold the bank angle, without even realizing it.  Once established in the turn some airplanes require a bit of in-turn aileron to hold the bank angle, some hold the bank with neutral aileron, and some require top aileron to keep from overbanking.  The top and down aileron inputs are inducing constantly changing adverse yaw forces which come and go, changing torque effects from the engine with power adjustments are producing changing yaw forces, and gyro precession from the prop from pitch motions are inducing yaw forces which come and go, and there are bumps, and you start running into your own wake.

In other words, you are in a machine pulled along by a big torque producing gyro that is slithering and sliding around in a gas with half a dozen forces and moments interacting on it simultaneously.  With all the subtle forces and inputs happening during a turn, I don't think you can identify and act on a single phenomenon like that.   What you have to do is, well, just do whatever it takes to hold the bank angle, altitude and center the ball and don't overthink it.

If you fly gliders, which use a yaw string that is more sensitive than a ball, even without the torque and gyro effects of an engine, the yaw string drifts this way and that while in a turn, seemingly independent of the aileron position some of the time. You generally make stabs of rudder in concert with aileron, but sometimes the yaw string seems to have a mind of its own and you just do what you have to do with your feet.


Why does the U-2 Dragon Lady not have swept wings? Swept wings increase the critical mach number for aircraft with otherwise identical wings (Source 1). The U-2 Dragon Lady is limited in altitude by its critical mach number, as it needs more speed in order to go higher (Source 2), but going faster would put it into its "coffin corner" (Source 3). However, looking at the following photo of a modern U-2 from Lockheed's website, the wings seem to have little to no significant sweep. The top speed (presumably what is used during the highest-altitude cruising) is only Mach 0.67 (Source 4), while modern aircraft like the Boeing 737 (which do have swept wings) often cruise at speeds between Mach 0.75 and 0.8 (Source 5).

Why does the U-2 not have swept wings?

I know that wing sweep was first developed in Germany during WWII; had the technology not taken hold in the USA by the time the U2 was developed in the 1950s? Or is there a deeper technical reason I'm missing?

Sweeping a wing costs weight, for several reasons. Therefore, if the goal is to fly high and achieve long range, an unswept wing is the better choice. Only when transport performance needs to be maximized will a moderately swept wing look better.

Why is a swept wing heavier?

Sweep reduces aerodynamic efficiency, so a larger wing is needed to create the same amount of lift.
Sweep introduces torsion when a straight wing will mostly see bending only. Adding torsion strength needs more structure.
The stall characteristics of a swept, high aspect ratio wing are extremely unpleasant and require a healthy margin from the stall angle of attack, when flying high requires to fly just at the edge of stall.

In the end, Kelly Johnson decided to cut weight and drag as much as possible but not to pursue maximum speed to achieve the greatest flight altitude. Another reason was that the U-2 begun as a modification of the XF-104 with extremely stretched wings. Adding sweep would had resulted in too many modifications to the U-2 fuselage, which was initially built in the same tooling than that of the XF-104.


What is a "Russian IATA code"? On Wikipedia, a few obscure ex-Soviet airports like Tamchy Airport in Issyk-Kul, Kyrgyzstan list "Russian IATA codes":

  IATA: none (ИКУ), ICAO: UCFL

"ИКУ" being Cyrillic for "IKU", which is not a recognized code according to the official IATA finder.  This Russian site lists "city codes" (Коды городов), but gives no source, and as bonus gives the ICAO code for Иссык-Куль as "UAFR" (which gcmap.com has never heard of).

Where do these codes come from?  And does IATA play any part in maintaining them?

It's a Russian internal city or airport identifier. Many small cities don't have IATA codes, but do have internal Russian codes.

This system is called CRT (Center for schedules and tariffs, ЦРТ, Центр Расписаний и Тарифов) named after a department in the organization that manages them (see below). Wikipedia article cited below claims it's also called "Sirena" code (named after Sirena -- a booking system for airline and railway tickets).

Here's a translation of a fragment from Russian Wikipedia:

  The internal city and airport coding system in the former USSR is structured analogous to IATA. [...]

  The airport code in this system consists of 3 letters of the Russian alphabet. As in IATA codes, the 3-letter combination is interpreted as atomic and has no internal structure. As in case with IATA, all 3-letter codes are unique.

  Like IATA, the codes were assigned to cities such that the code has something in common either with the name of the city or with its IATA code [...] Contrary to IATA, the internal codes were changed after cities were renamed in the 1990s: Saint Petersburg's internal code was changed from ЛЕД to СПТ, Samara (formerly Kuibyshev) -- from КУФ to СМШ, Ekaterinburg (formerly Sverdlovsk) -- from СВХ to ЕКБ.

  Many small cities and airports in the former USSR have an internal code only.

  In late 1990s foreign (non-Russian) cities were assigned internal codes because of the popularity of these destinations (e. g. Barcelona -- БЦН).

  As of April 2009, there are about three thousand internal codes that are actively used.

It appears that the codes are maintained by the Transport Clearing House. The section Coding Directories on their page Schedule & Tariffs  says:

  STC maintains the aggregated database of coding directories for the purpose of universal use of codes in information systems for passenger services reservation and sales, publication of timetables and fares, ticketing, settlement and other commercial issues related to passenger services.

  STC maintains the codifiers in pursuance of Provision on Assignment, Maintenance and Use of Internal Codes of Carriers, Organizations, Airports, Cities (points) and Civil Aviation Agencies (№ ДВ-63/и dated 12.05.94) and Directive "On Coding Directories Approval” (№ ДВ-109/и date 14.07.94).

  STC supports the following coding directories:

  Airlines
  Airports
  Cities

In Russian, STC is translated as CRT (ЦРТ) and I've heard people refer to the internal codes as "CRT codes".


Is Auto Pilot capable of performing TCAS resolution advisory? I just watched a near mid-air collision video clip on Youtube. When AP is on and TCAS gives resolution advisory ("climb climb" or "descend descend"), does AP automatically perform the advisory if the pilot doesn't take over in time?

Short answer is no.

First of all it is resolution advisory as you said. Its purpose, is to make the Pilots aware of an imminent danger/conflict. As with 'Terrain, Terrain', 'Pull up!, Pull up!', it is up to the pilots whether or not they will follow the instruction (normally they always do, but there are exceptions).

However when the pilots hear 'Climb, Climb' or 'Descent, Descent', or another TCAS alert, they should immediately initiate the required action. After all, these days there are top-notch ATC and confliction prevention systems, as well as high-tec TCAS systems on most of the commercial aircraft.


What is "settling with power" and how does it differ from vortex ring state? I've always heard these terms used interchangeably. I figured that "settling with power" was what the pilot did to cause the vortex ring state (VRS). But comments on another question indicate that they are two entirely separate aerodynamic phenomena.

I understand VRS, so what is settling with power?

I knew that the debate would start :)  This is probably the most contentious question in helicopter operations.  it's right up there with the "equal transit time" theory of lift generation a few years back.  The only agency I am aware of that defines them as different is Transport Canada.  Instructors, pilots, WikiPedia, training videos, books and blogs all get this wrong often. It seems to be very common in the US for people to refer to vortex ring state as "settling with power".

Tom, I know you said you already know what vortex ring state but I think that the "why are they different" explanation is better when both are contrasted together. Please excuse me for repetition.

They are different.

Vortex ring state (VRS).

VRS ring state is a purely aerodynamic condition. In normal flight, whether climbing, descending or cruising, the relative airflow striking the blades is principally from ahead.  In a developed VRS, the helicopter descends into it's own vortex which is "recirculated" as the helicopter descends faster than the vortex descends and results in the recirculated air being drawn up, then almost vertically down into the rotor.

From HelicopterEMS.com

This causes a critical increase in the angle of attack and a corresponding loss of lift causing the helicopter to descend faster and faster up to rates of 6000 feet per minute.

In order for the helicopter to descend into its own vortex, it must meet three conditions at the same time (typical values for most helicopters):

  less than 30 knots airspeed;
  greater than 300 feet per minute descent;
  power applied to the rotor.

Removing anyone of these gets you out of VRS but there's a catch.  If you try to reduce the rate of descent by increasing collective and therefore power, which would be the instinctive reaction of someone not trained to recognise and get out of the state, you increase the strength of the vortex and the recirculation and make the problem worse.

The only way to stop the rate of descent in VRS is to use the ground, which you really don't want to do at up to 6000 feet per minute and will probably spoil your plans for the weekend.  However, you DO have power.  You can use all of it until you hit the limits and still you won't stop that descent.

To recover, remove power by entering auto-rotation or increase airspeed to fly out of the vortex.  Auto-rotating out of VRS can take a long time and use a lot of height in the recovery so the accepted and taught technique is to fly out of it, any direction will do, which takes a second or two to recover.

Settling With Power (SWP)

SWP is not an aerodynamic effect.

At it's simplest, it occurs when you need x amount of power to stop a descent but, for a lot of variable reasons, you have less than x power available.  Increasing power results either in exceeding the engine or power train limits or stalling the rotor as drag increase exponentially and exceeds the power available to drive the rotor.

The slower a helicopter flies, the more power it requires:

From the AOPA blog.

When you get into the low speed regime, you can see that the power required rises rapidly.

Imagine you are coming into a hover.  You are travelling slowly at about 20 knots but have a low rate of descent, not enough to enter VRS.  If you keep going forward, you will be OK.  But, our imaginary pilot makes a mistake and turns into a 15 knot tailwind. The airspeed drops to about 5 knots so the lift produced drops by the square of the speed change and the power required rises rapidly.

The helicopter will very quickly develop a high rate of descent. The pilot increases collective to compensate but finds that the engine cannot produce enough power to maintain lift and power the tail rotor which is also working harder since you increase the torque by increasing power.  It is possible to simply run out of power.  If the pilot is lucky, they will be unconscious and found with the collective lever buried in their armpit.

SWP nearly always happens close to the ground and once in it, there is no recovery (insert suitably large number like 99% of the time).  You have no spare power to reduce the rate of descent or to increase airspeed to increase lift and fly away.

SWP is normally a result of pilot error (as above), mechanical problem leading to unexpected reduction in power available, wind shear causing unexpected reduction in airspeed or other environmental effects reducing lift available (coming into a hot and high hover for example).

Perhaps the easiest distinction to make is that you are already using all of your available power when you enter SWP. There is nothing left to give!


If the radio fails, can a pilot contact the tower by cell phone? Is it an accepted practice to notify the tower of a radio failure by cell phone, and use the cell phone as a radio, or are there other ways of dealing with radio failure?

As I pointed out in another answer of mine, it is not legal to use a cell phone in flight, and as another answer to the same question says, it really doesn't work very well anyway..
Now, if the pilot has an emergency, they can exercise the emergency authority of the PIC as allowed in 14 CFR 91.3(b) to go ahead and use the cell phone.  If it is just the radio failure though, that isn't usually an emergency since there are other procedures in place for radio failures.
Radio Failure Procedures
AIM 6-4-1 contains the procedures to use in the event of a radio failure.
Basically, if the pilot is in visual conditions (VMC) and can remain that way, they should fly VFR (visually) and land as soon as practical.  If they can't remain in VMC then there are a number of rules which spell out the route and altitude that they should fly, as well as when they should start an instrument approach.
Once they get to an airport they will still need to get clearance to land if it is a towered airport.
AIM 4-3-13 covers that, and basically the tower will communicate with the pilot via light gun signals:


Why Didn't the USSR Build An X-15? In the history of aerospace engineering in the United States, the X-15 is lauded as a critical and necessary step on the path to manned spaceflight. Throttle-able chemical rocket propulsion systems, reaction controls, and pressurized flight suits were all major design features of the X-15 that eventually found their way into future successful spacecraft.

Given the obvious resources the USSR put into the space race and their numerous successful missions, why did they never build a hypersonic space-plane akin to the X-15?

I like the X-15, it was certainly an amazing airplane, but the truth is there were few benefits to the space program from the X-15.  It was far from a critical or necessary step:

The Mercury space suit was a direct derivative of the BF Goodrich Navy Mark IV, which had been in use for years. It wasn't developed for the X-15
The rockets used in the space program were completely different from the X-15. They were orders of magnitude stronger for one thing, used different fuels and completely different designs. Throttle-able rocket propulsion systems weren't new
The X-15 thermal protection system was of no use to the space program, which had to deal with far higher temperatures

There were some benefits:

It was a good source of astronauts: several pilot from the program went on to the NASA programs, including Neil Armstrong
Data from the X-15 missions were used in the X-20 Dyna Soar spaceplane which never flew, but it eventually morphed into the space shuttle

As to why didn't the Soviets make one, they didn't need it. Their manned space program built off of their ICBM development efforts which were successful. If the US hadn't built the X-15 the manned space program would most likely never gone the space shuttle route, but that wouldn't have been any sort of deal breaker.


Is there any regulation that force(or recommend) to change flight number in case of flight delay? I have a question about a flight number of delayed flight.
I think that if the daily flight(e.g. OZ9609) is delayed until the following day, there are two flights with a same flight number.
In this case, I think operating two flights with same flight number could cause confusion to passengers and systems related with operating the airport.
So I want to know there is any regulation that force to change a flight number if situation like this case occurs.

An airline's flight number for commercial purposes is not necessarily the same as the identifier the aircraft uses for air traffic control purposes. For example, British Airways flight may show up on a flight tracking web service as BA### but air traffic control identifies them as "Speedbird ####" where the number may or may not be the same as the airline's commercial flight number.

So, to answer your question, there is no FAA regulation that forces the airline to change commercial identifiers. The ATC identifiers are set when the dispatcher files the flight plan, and they must be unique to ATC. The system will reject it if the identifier is in use, or will be during any period of flight.


What is the function of ECS in airplane? What is the function of ECS in airplane?

The ECS system is the Environmental Control System.  It is the system that handles pressurization and thermal control of the aircraft. The FAA has a nice handbook on it here. There is some more information on how it works on the new 747-8 here that may be of interest.


How to calculate ground speed using a map with a known scale and time? If an aircraft flies from point A to B for a distance of 8cm on a chart of 1:1,000,000 in 18 minutes, What’s the ground speed?

It’s a multiple choice question and the possible answers are in ratios.
(#45 in the image)

  A. $1:1,105,550$
  B. $1:1,250,000$
  C. $1:1,740,740$
  D. $1:1,074,740$

I can’t change the question but I can explain how it is related to aviation.  The question is from flight dispatcher module Air Navigation, where by in dispatching the aircraft we must know about places where aerodromes are located passing etc and so we learn about maps and charts.. am not off topic the question is 100% aviation related

If a plane traveled $8\ \mathsf{cm}$ on a map with a scale of $1:1\ \mathsf{million}$, then it traveled $8\ \mathsf{million\ cm}$ in the real-world.

$$8\ \mathsf{million\ cm} = 80,000\ \mathsf{meters} = 80\ \mathsf{km}$$

Convert 80 km in 18 minutes to a speed of kilometers per hour:

$$\frac{80\ \mathsf{km}}{18\ \mathsf{min}} \cdot \frac{60\ \mathsf{min}}{1\ \mathsf{hour}} = 266.6 \frac{\mathsf{km}}{\mathsf{hr}}$$

Groundspeed is traditionally expressed in knots:

$$266.6\ \mathsf{kph} \cdot \frac{0.54\ \mathsf{kts}}{1\ \mathsf{kph}} = 144\ \mathsf{kts}$$

To put this in perspective, 144 kts is a bit fast for a Cessna 172, unless it has a good tailwind, but not at all unreasonable for many small high-performance planes.

The answers to question #44 don't make sense.
The question is "The scale of the chart is...", but the possible answers are all KTS (knots).

The answers to #44 and #45 are clearly reversed.
However, the right answer of 144 kts, is not listed in the possible answers.

In general, I think that test is extremely poor quality.

Question #43 (movement of the earth around the sun) may not even be related to aviation.


How are forward and aft CG limits calculated? I have been tasked to create a POH for my aero engineering coursework and part of this task is to create the CG envelope for the theoretical 65 passenger aircraft. I have figured out weight, moment and cg for all loading scenarios but I am wondering how to create the actual envelope using forward and aft limits, as surely not all these scenarios will be able to fly? TIA

You have done half of the way. Since you have computed the CG variations in all loading scenario, you know approximate limits. This limits are the ideal limit from loading and unloading point-of-view. But in real application, the design of the aircraft does not allow such broad limits.

There are many factors that limits the aircraft aft CG movement:

MLG load: The loads on MLG increases as the aircraft weight is increased or the CG is moved aft. Since in most of cases, the MLG's are designed for touch down loads at maximum landing weight, which is lower that the maximum ramp/take-off weight, the static loads at maximum ramp weight may exceed the dynamics load at touch down. So, a limitation may be imposed on aft CG location regarding this issue.
Take-off Tip-Up: At the take-off conditions, the engines are producing their maximum thrust. If the engines are located below the CG, which is the case for under-wing mounted engines, this thrust produces pitch-up moment. This pitch-up moment reduces the load on the NLG. From the other hand, as the aircraft weight decreases combined with aft cg movements, the load on the NLG will be further decreased. At light enough NLG loads, steering effectiveness is reduced, and eventually, the NLG load can become negative causing the airplane to tip up. So an aft CG limits may be imposed to maintain enough loads on the NLG.
Static Stability: Too far aft CG may cause neutral or negative stability, so a margin (normally 10% of MAC) should be provided between the CG and the aerodynamic center.
Go-Around: At go-around condition, the engines are producing the maximum thrust, and a huge pitch-up moment. Elevator deflection are required to counter this moment with pitch down moment. This moment is proportional to amount of upward acting load on the tail a the arm of this acting load. The distance between the tail and the CG is the arm. As the cg moves aft, if the tail reaches its maximum lift the aircraft can not maintain its path. So a limit may be imposed to prevent pitch-up at go-around.

By combining the above limits, and other limits that may arise from that specific configuration, an aft CG limit can be estimated.


Can all helicopters hover, and how long does it take to "stop"? Following the accident of Kobe Bryant's helicopter N72EX, there are a few things that puzzle me:

While waiting for clearance to fly close to Burbank airport, the helicopter didn't "stay in place", but actually made all sorts of loops and circles over Glendale:

Source: Flightradar

Does this mean that such an helicopter can't actually "hover", and has to move forward to stay up in the air? There are definitely helicopters which seem to be able to stay in the same location (TV helicopters, police helicopters), so I wonder what is the difference (size? load?). Or is it just "cheaper" to make loops rather than hover?

This question and associated answer seem to indicate that there is actually a limit to the "hovering" capability of helicopters "in the air", though I'm not what the consequences are when you go beyond the limit. Is the helicopter just not able to "stay in the air"? Or does it need to move forward to be able to maintain level flight? How does it actually work, shouldn't "tilting" the helicopter forward reduce the "upwards" force?
At the end of this ill-fated flight, the helicopter makes a left turn until it crashes in the mountain.

Current "expert" analysis (pending NTSB's inquiry) point to an issue with the weather that suddenly got very bad (basically the helicopter being sandwiched between very low ceiling and rising terrain) which made the pilot make a manoeuvre that ended up being a very bad choice.

Could the helicopter not just have "stopped" or at least "slowed down" rather than turn? If it should have been able to stop, how long (in time or distance) would it have taken?

As noted in another answer, all helicopters can hover, but a so-called "high hover" (out of ground effect or especially at operational altitude) is a more difficult maneuver, requiring more power than a ground hover, and being harder to maintain (because reference points are much further away).

Helicopters generate more lift for the same power when in forward flight, and transitioning from forward to hover requires a well-controlled combination of adding power, adjusting collective, and maneuvering cyclic (in both axes) and anti-rotation controls -- which is to say it's much harder than simply flying forward at low speed.  In general, once aloft and flying forward, it's much easier to continue forward flight (it's also safer, since in the case of a failure, autorotation works better if you already have some forward speed).

Hovering on instruments is even more difficult than a high hover -- so if visibility is a problem, it's generally far better to continue forward flight than to attempt a high hover.


Current FMS with COMM tunning function capability? I am currently more familiar with GARMIN 1000 systems than with the ones that are used nowadays in airliners.

I know that you can tune a NAV aid from the FMC in an airliner. Actually, modern FMS come with the auto-tune capability for NAV aids (which helps to achieve the desired RNAV or PBN requirements). My question is if there is something similar regarding the COMMS frequencies. Let me elaborate:

With Garmin 1000, you can even select COMMS frequencies from the FMS. You can actually search an aerodrome and, if selected, it will automatically tune the COMM frequency for that aerodrome in the standby freq. Therefore:

Is there any mechanism like this one in the FMS of typical modern airliners? (a320, b737, a380...). If not, could you please give me examples of typical GA aircrafts that come with FMS with that capability?
Is there any way that we can we select comms frequencies from a typical FMS in an A320 or B737, or do we have to use always the nav/comms station to do so?

On Airbus/Boeing airliners, the Comms system is completely separate from the Nav system, so - no.

The 787 has the ability to pre-store lots of Comms frequencies, so that you've already got the numbers in the box. But it doesn't have the modern light aircraft capability to tell you that this frequency is this airport and that facility.


In a pattern, when do you begin your descent from TPA if following another aircraft? I had always been taught to begin a descent from TPA abeam the touchdown point, even if tower tells me to follow another aircraft. Yesterday I flew with an instructor who did not want me to descend from TPA until abeam the aircraft I was following. I understand that I begin my base turn when the aircraft I am following is abeam my wing. I did not know to also wait until then to descend from TPA. It does make more sense to stay at TPA until this point but I can't find anything saying one way or the other.

Every CFI I have ever flown with has a different procedure for when to descend. Its annoying. Think of it as descending to the runway when you are in a position to land. If you are not following another aircraft, then you can begin your descent abeam the threshold. If you are following another aircraft, then you should wait to descend until you are in a position to land as #2, which could be after you've already turned base or (long) final.


How do you indicate whether the supply of power to the gyroscopic instruments is adequate? Is there an instrument to indicate this?

For suction powered gyroscopic instruments there is usually some suction gauge to indicate the quality of the vacuum. See this question for more details in what the instrument shows.


Weather sensors required for ILS approach operations? Was flying into Sullivan County this weekend and had to run the RNAV instead of the ILS. ATC advised there was a NOTAM for the weather sensors (which we had already confirmed.) Does an ILS approach require that the airport have functioning weather or is this just a case of a 2-for-1?

Whether or not an ILS may be conducted without proper weather reporting will depend on the regulations under which the flight is operated.

In simple terms, a flight operated under 14 CFR 91 may perform an ILS without this weather reporting.

This may also be allowed under the eligible-on-demand rules of 14 CFR 135, if all pertinent requirements are met.

Otherwise, a flight operated under 14 CFR 135 or 14 CFR 121 will generally not be approved to conduct an ILS without approved weather reporting.

This answer applies under FAA jurisdiction.


Would it be viable to install a screen in front of jet intakes to prevent them from sucking in birds? Why isn't there a protective screen with large diameter holes (approx 2') mounted in front of the jet engine intake to protect the turbine blades? This would  keep larger birds and large ground debris from getting sucked in, which can cause serious internal engine damage.

Modern high-bypass turbofan engines work by pulling in immense volumes of air and accelerating it.  A screen as proposed would make that task far more difficult, which would ruin the efficiency of the engine.  It's also pretty well unnecessary.

Jets worldwide take plenty of birdstrikes every day.  Unless the pilots see it (hitting the windscreen will do that) or hear it (hitting something near the cockpit) or the bird goes into the engine core (which causes the smell of burned bird in the air conditioning), the chance that the crew knows about it before the next walk-around inspection is pretty slight.  The vast majority of birdstrikes are utterly inconsequential.  (Except for the bird -- ruins his day pretty thoroughly!)

Yes, there are a small number of very highly visible events where birds do disable an aircraft -- the "miracle on the Hudson" and the loss of an AWACS in Alaska come to mind, and there are others.  And it's possible for a birdstrike on an engine to cause significant damage IF the bird is large enough AND it goes into the core, but in the big picture, that is actually pretty uncommon.

Thus, the aircraft manufacturers and operators end up accepting the risk of a catastrophic birdstrike, because the alternative of protecting the engine as suggested is too expensive when the effects on the efficiency of the engine are considered.

One other point, bird flesh is pretty easy for an engine to chop up and digest.  If a big bird hits a metal shield at high speed, there would be the risk that the shield could be damaged enough that some of the metal would break apart and go into the engine as well, and THAT would cause far more damage than just the bird.

Fun video of stuff being shot into an engine during testing


How should the crew callout 1,000 ft. prior to assigned altitude? When climbing or descending in a multi-crew cockpit, most SOP's require a verbal callout at 1,000 ft. prior to the assigned altitude.

I typically hear different callouts by different people:

"One to go"
"Six thousand for seven thousand"
"Six thousand climbing seven thousand"
"Six for seven"

Is this just a personal preference kind of thing or is there an actual safety benefit to one or the other?

As Ralgha stated, this kind of callout would be included in the SOP. A couple I found in searching were the NBAA (same in their helicopter procedures by the way) and Angel Flight NE, as well as some generic CRM guides. The FAA Instrument Procedures Handbook also mentions altitude callouts, suggesting something like "two to go" and "one to go" (in thousands).

The NBAA includes this specific phrasing:

  The callout is to include the altitude vacating and the assigned
  altitude i.e. “Six thousand for seven thousand” or “Flight level
  three-zero-zero for two-niner-zero”. After the PF makes this call, the
  PNF will verify and validate the call by stating “check”.

This Flight Safety Digest mentions that USAir used to use the "two to go" and "one to go" phrasing, but opted to change this for the same that the NBAA uses. The new policy has the pilot flying make this call, since they are in control of the climb, and makes it more clear what the final altitude will be.

The Flight Safety Foundation went in to a bit more detail about the "why" behind the callout. They mentioned that in their observations, the callout was sometimes not done due to workload of other more important things going on in approach/descent. They explain the benefit:

  This is not to suggest that the 1,000-ft callout is trivial. On the
  contrary, it ensures that both pilots concur about the altitude
  target, directs the attention of a flying pilot who might be
  distracted back to the impending level-off and draws both pilots’
  attention to what the autopilot is supposed to be doing.

Another resource that suggests the important is a report of an aircraft overshooting its altitude by 600 feet because the callout was missed. This report is in the ASRS database, report number 317750.

I also found it referenced in this book about communication. They didn't really comment on it specifically, but used it as an example of how communication is critical. Specifically, the more exactly the terminology is defined, the more clear the communication will be.


Need communication example departing and arriving uncontrolled airport within class D I'm looking for a communication pattern to depart and arrive an uncontrolled airport within class D airspace VFR. One example can be F69 which is within KADS. This case looks even trickier because this airspace is right under class B. It seems to me it is possible to go under class B especially if going east. Would it be recommended considering how busy class B can be or it is actually a viable option to go from F69 into class D and then class B? It would be great if somebody could post links to videos. I'd like to know exactly what to tell and what to expect in reply for both cases departing and arriving.

I fly out of Addison, McKinney, Mesquite, Denton, Rockwall, Sulphur Springs and Aero Country a lot. I am also friends with the A&P located at Airpark. If you would like a safety pilot who knows the local area, maybe we can hook up.
A few things to remember when operating out of airpark:

The runway is barely maintained. But, it is not perfectly smooth. Treat it like a soft field.
When taxiing anywhere besides the runway, you will be taxiing on turf. Protect your nose wheel.
In the daytime watch out for chickens.
At night, beware of coyotes.
Do not park, walk, or stand under the concrete bikini hangars. They are off-limits due to instability and collapse.
The windsock is in disrepair. Do not trust it. Look for other nearby flags and smoke from local bbq restaurants.
The runway has non-standard markings
The runway is a lot shorter than you think due to displaced thresholds at both ends due to buildings, fences, and trees.
Make all of your radio calls on the CTAF while taxiing. Make a few CTAF radio calls while in the pattern and right before taking the runway for takeoff. All of your other radio calls will be on Addison or Fort Worth frequencies. There is very little traffic at Airpark (1-2 aircraft a day). All of the other traffic in the area will be on Addison or Fort Worth frequencies.
The runway is aligned with the runway at Addison. You will be on a very similar final and departure leg.
Addison is only 3 miles away. You can almost see the Airpark area from the Addison Tower.
Because of Addison Tower’s Proximity to Airpark, contacting them as soon as practicable means
as soon as you start the engine.
Addison Tower does not like hearing from pilots directly as an initial radio call. They prefer pilots to contact Ground first and get transferred to them via a frequency change. At Airpark, it would be best to get Clearance Delivery and/or flight following first through Fort Worth Approach. Then, contact Addison Tower.
Inbound to the Addison Class D, you are required to listen to the ATIS first. There will be a frequency given over ATIS to contact Fort Worth Approach. You must contact Fort Worth Approach before contacting Addison Tower. Period! Trust me when I say Addison Tower will not like it if they are your first point of contact.
Addison is an extremely busy Class D. It caters to jet and turboprop business aviation. If it did not have DFW and Love Field about 10 miles away, it would probably be a Class C or at least a TRSA.
There can be as much as a 15 minute and sometimes up to an hour wait in the run-up area for clearance to takeoff. And, they will sometimes utilize a line up and wait clearance. This can affect your takeoff clearance at Airpark.
Good visual reference points for Airpark are the Dallas North Tollway and the President George Bush Tollway. Airpark is located in their Northwest corner.
The Airpark area is extremely congested. Climb out to a safe altitude as soon as possible. If you have an engine out upon takeoff you have very few options. None of them good. To the North, you have a green space on the East side of the Dallas North Tollway. To the South, you have Addison Airport.
Do not contact the Airpark airport owner, operator, or manager listed as points of contact. They are anti-aviation real estate developers who bought the land as an investment. They will try to steer you clear of Airpark as much as possible. Their acquisition of Airpark is very similar to Meigs Field in Chicago. They bulldozed the operating FBO and fueling area. But, it took a court order to keep them from bulldozing the runway.
Most pilots choose to go North and East to practice maneuvers, to practice instrument approaches, and to beat up the traffic pattern at other airports.
If you have at least a private pilot certificate, do not worry or be intimidated by the Class B. If you are flying to, from, through, or above the Addison airspace, you will need to be in two-way communication with ATC anyway. Just ask for clearance through the Bravo.


Does it make sense to do an emergency landing without nose gear in order to reduce stopping distance? Would a pilot decide to land without the nose gear down to increase friction if for example all the engines have suffered a flame-out and there is only a very short runway available ?

(Source)

That was the case on July 23, 1983 (but not quite).

It was luck the manual gravity-extension didn't lock the nose gear in position. That has been attributed to the shortening of the landing roll/slide.

  Two factors helped avert a potential disaster: the failure of the front landing gear to lock into position during the gravity drop, and the presence of a guardrail that had been installed along the centre of the decommissioned runway to facilitate its use as a racetrack.

However, no commercial aircraft is certified for it, because it can do more harm than good. And depending on the aircraft type, separate controls for each landing gear in manual-extension mode may not exist.

A hard landing without the nose-landing gear may rupture the fuselage, center fuel tank, or hydraulic lines. And with the added sparks from the sliding, that's a recipe for disaster.

Instead, a system such as the engineered materials arrestor system (EMAS) may help:

(Source) EMAS.


How fast can fuel be siphoned out if you leave the cap off? It is a dreaded scenario; forgetting to secure the fuel cap.

I understand the low pressure area generated above the wing will siphon fuel out of wing tanks, how fast would this happen in a smaller GA airplane with wing tanks (something like the Cherokee perhaps) if the fuel cap was to be completely forgotten (rather than just not tightened)? Also, would it be able to suck the tank completely dry or would there be some limit to the amount of fuel that might be lost this way?

I just had X-plane do this to me while doing some IFR practice and it reduced my fuel with about 2 gallons/minute per tank until they were both completely empty and I was wondering if this is realistic.

It can happen very quickly.

I don't have exact numbers, but an acquaintance had this happen in a Cessna 172 and the entire tank was emptied in just a few minutes - the amount of time it took to do one circuit of the pattern and land. The fuel cap was not in the filler neck on departure, and was hanging from the chain, banging against the wing. The moral of that story is: never assume the fuelers put the cap back in.

I've personally flown an older Cherokee 160 that had a loose fuel tank gasket. When doing slow flight, the pressure above the wing was so strong that it would start to ooze fuel from the cap. Fuel would flow in a rather frightening amount back along the wing, and that's with the cap still on.