Is there an in-flight built-in-test in an airplane? Is there any in-flight built-in-test in the airplanes separate from the in-flight monitoring?

The thing that separates a BIT/BITE (E=Equipment) from continuous fault monitoring is that the continuous fault monitoring simply responds to exceedances of various paramters or values outside of specified limits in real time as they happen (say where an analog voltage signal of a device drops below a minimum of X or exceeds a maximum of Y), whereas a BIT/BITE test is a specific routine where simulated fault signals are injected into a circuit to see if a fault monitor is doing its job.

BIT or BITE tests of electronic controllers can be categorized into three types:

Start Up BIT: Most common.  A test routine automatically run on power up of the controller.
Initiated BIT: Controllers may have a manually initiated BIT/BITE that can be run any time, but this is usually triggered by a button on the controller itself in the avionics compartment, or through a maintenance access portal in the aircraft maintenance diagnostic system, and usually doesn't have a flight crew initiated facility (but may in some cases).  These are normally intended for troubleshooting.
Continuous BIT: A controller may run an internal self test routine on a continuous cycle while powered up, where a controller has fault detection circuits that can't be allowed to have dormant failures, even for the duration of the flight.

Absolutely.  Every flight is a built-in in-flight test.  For example, if you perform a 2-g turn and the wings don't fall off, you've demonstrated that the aircraft can sustain 2 g's without structural failure.


What is the absolute ceiling of a 737-200? We're trying to find the official absolute ceiling for the 737-200 for a school project.  So far have only been able to maximum and service ceilings for this craft. Can anyone point us to the correct information for absolute ceiling?  Thanks!

Find the pertinent  performance charts for Vx (Max climb angle)and Vy (Max climb rate). You may have to extrapolate, but the altitude where Vx and Vy converge is the Absolute ceiling.


Are there any rules requiring hands/feet on the controls at all times? Are there rules that require one of the pilots in a large commercial aircraft to have positive physical control of the yoke/joystick at all times?

And the same question for the rudder actuators, if any (pedals)?

There is nothing I can find in the FARs requiring that a pilot keep their hands and feet on the controls at all times.
Such a requirement would be impractical and dangerous in many situations (such as when writing down a clearance in the air: For most people if you keep your hands on the controls while writing you will have a tendency to push, pull, or twist them, resulting in unintended attitude changes).

The most relevant sections of Part 91 would be 91.3 and 91.13:

14 CFR 91.3 (FAR 91.3) says:

  §91.3   Responsibility and authority of the pilot in command.
  (a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.
  . . . .

and 14 CFR 91.13 (FAR 91.13) says:

  §91.13   Careless or reckless operation.
  (a) Aircraft operations for the purpose of air navigation.
   No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another.

  (b) Aircraft operations other than for the purpose of air navigation.
  No person may operate an aircraft, other than for the purpose of air navigation, on any part of the surface of an airport used by aircraft for air commerce (including areas used by those aircraft for receiving or discharging persons or cargo), in a careless or reckless manner so as to endanger the life or property of another.

So basically it's perfectly legal for a pilot to fly with their arms crossed and their feet flat on the floor, even without an autopilot, as long as the pilot in command remains able to exercise operational control of the aircraft as required to ensure the flight remains safe and legal, and as long as they are not acting in a "careless or reckless manner" (like letting their altitude wander all over the place while sitting with their arms crossed).

Nope. Sometimes they just let go and yell, "Look Ma! No hands!" into the local traffic channel. Just kidding.

There may be a slight disconnect here in how you think about pilots and the law. The average (non-pilot) person imagines that pilots are robotic servants that must obey all kinds of laws and regulations designed to "protect" passengers and slavishly follow orders from (non-pilot) FAA controllers. That is not how it works.

In the sky, the pilots are the bosses. ATC and the laws are there to help the pilots do their job better, not boss them around and force them to them to do things they don't want to do.


When do pilots disconnect the autopilot on an ILS approach? In clear weather, when do pilots disconnect the autopilot, if the plane is flying an ILS approach and the autopilot is in "approach" mode (tracking both localizer and glideslope)?

Would the answer differ significantly in different planes, for example Boeing 777 vs Airbus A320?

The decision to disconnect the autopilot is made by the pilot and can be made at any point as long as the operational limitations of the aircraft are satisfied (according to the type of ILS). The pilot also has to satisfy the applicable regulations and company SOPs (as @Sami already pointed out). Note that this depends on the pilot decision too- the pilot can fly the missed approach in autopilot if he decides so.
Usually, the aircrafts have minimum altitudes below which the autopilot has to be disconnected, which are given in the aircraft operating limitaions. For example, for Airbus A340,

CATEGORY II
If the crew performs an automatic approach without autoland, the autopilot must be disengaged no later than at 80 feet.

For Boeing 777:

Autopilot/Flight Director System
The autopilot must be disengaged before the airplane descends more than 50 feet below the MDA unless it is coupled to an ILS glideslope and localizer or in the go–around mode.
Without LAND 2 or LAND 3 annunciated, the autopilot must be disengaged
below 200 feet AGL.

For Boeing 787:

Autopilot/Flight Director System
Without LAND 2 or LAND 3 annunciated, the autopilot must be disengaged
below 100 feet AGL.

As an example in GA aircraft, for Cessna C172 G1000:

The autopilot must be disengaged below 200 feet AGL during approach operations..

As you can see, there is not much difference.

In calm wind or under 5 knots on a cat 3 then ride that sucker all the way down and it will disengage when the rear wheels hit the runs way, but keep your thumb on the elevator trim in case it doesn't.  In most normal conditions keep it around 50 ft. agl.  In low visibility then keep it on until you see the runway lights and feel safe to disengage and land/glide manually.  If you start to oscillate before touchdown then turn the A/T off reduce to idle and disengage the Auto Pilot and dip your right rear or left (depending on wind direction) and grab that runway letting the plane settle.  If you are cat 2 then disengage no lower than 20 feet agl, so you can adjust your glide and attitude or roll for a softer landing.  If you are cat 1 then approximately 50 feet or until you see the lights on the runway in low visibility. Discretion is key here or course, but trust the glideslope in low visibility as long as possible and make sure you have the correct QNH and be ready to mash that TOGA button if something isn't right.


What do the dashed extended green lines on this PFD mean? The most important source of information for the pilot is the PFD

Those are radials off of the HME navaid, which is tuned in both Nav receivers. The two radials displayed correspond to the courses set in the two course select windows.

Putting a navaid's identifier into the FMC "FIX" page can also generate similar bearing lines, although there would be a green circle around the navaid in that case.

An ILS (also the departure runway in the flightplan) extended centerline shows as white, not green, and appears when that ILS (or any other) approach is active in the route, rather than when the frequency is tuned.

Thise dashed green lines appear to be extended center lines for each runway.  Most likely those are the runways with an ILS.


What is the definition of taxiing? According to Wikipedia the definition of taxiing is:

  the movement of the aircraft on the ground under its own power [however]
  push-back is not considered taxiing

In contrast, Eurocontrol seems to define it as:

  any movement on the ground including push-back

Any other reliable sources to look up for the correct definition?

Definitions always depend on their context, that is why documents often included a list of definitions. It allows authors to define terms in the context of the document. A definition context is not always a document, it could for example be a field of expertise as well.

The Commercial Aviation Safety Team / International Civil Aviation Organization (CAST/ICAO) Common Taxonomy Team (CICTT) taxi is defined as:

  The aircraft is moving on the aerodrome surface under its own power
  prior to takeoff or  after landing

More detail can be found in the phase of flight definition document.
This is definition can be applied in many situations.

The Eurocontrol definition you link to comes from the Air Traffic Flow & Capacity  Management (ATFCM) and Airport Collaborative Decision Making (A-CDM) domains where statistics about gate-to-runway time play an important role for planning purposes.

In that context it is not really interesting to distinguish the time that was spend in pushback from the time spend actually taxiing to the runway. The taxi-out time is hence defined as the time between off-blocks and take-off.

The time you leave the apron (GATE/RAMP position) and arrived at your takeoff strip (Piano key-marked Takeoff zone), the journey in between is well-known as taxiing. I am sure that this is correct because I have experience with runways and aircrafts. It's a common sense that taxii means no ground power/air cart, and also no support. You taxi your way to the takeoff zone. No disupte about this.


What medications may pilots take while flying? We all get sick, suffer from allergies and sometimes chronic issues.  It is not safe to fly while on some medicines or in some cases, for some time after taking the medicine.

How do I know what I can take and still fly?  What resources are out there to check if a specific medicine is compatible with flying (AOPA, FAA, etc)?  Is there a comprehensive list of what I can and cannot take?

AOPA has the best database that I know of, but you have to be a member to view it.  They have some free information on their Medications page though.

There they talk about FAA Policy, and it starts with:

  The Federal Aviation Regulations include no specific references to
  medication usage. FAR 61.53 prohibits acting as pilot-in-command or in
  any other capacity as a required pilot flight crewmember, while that
  person:

  Knows or has reason to know of any medical condition that would make the person unable to meet the requirement for the medical certificate
  necessary for the pilot operation, or:
  Is taking medication or receiving other treatment for a medical condition that results in the person being unable to meet the
  requirements for the medical certificate necessary for the pilot
  operation. Further, FAR 91.17 prohibits the use of "any drug that
  affects the persons faculties in any way contrary to safety."

AMAS (Aviation Medicine Advisory Service) also has a list (which is free) but I don't think that it is organized as well.  They are recommended by ALPA and NBAA though.

The most important thing though, of course, is to self evaluate and make sure that you don't fly if you are having any adverse reactions from the medication, or the underlying condition that you are taking the medicine for.

Any list that you consult has to be used only as a guide though, and not a carte-blanche approval.  Individual people can have reactions even to medications that are considered "safe" and "allowed" by the FAA, and this is why they don't list specific medications that they allow.  The FAA has a brochure called Medications and Flying, and one part of it has a few things to consider before taking any medication:

  First, consider the underlying condition  that you are treating. What
  will be the  consequences if the medication doesn’t work  or if it
  wears off before the ﬂight is over?  A good general rule to follow is
  not to ﬂy  if you must depend on the medication to  keep the ﬂight
  safe. In other words, if the  untreated condition is one that would
  prevent  safe ﬂying, then you shouldn’t ﬂy until the  condition
  improves — whether you take the  medication or not.

  Second, you must consider your reaction to  the medication. There
  are two broad categories  of medication reactions. One is a unique
  reaction  based on an individual’s biological make-up.  Most people
  don’t have such reactions but  anyone can, given the right medication.
  Because  of this, you should NEVER ﬂy after taking any  medication
  that you have not taken before. It  is not until after you have taken
  the medication  that you will ﬁnd out whether you have this  uncommon
  and unexpected reaction to the  medication.

  Third, consider the potential for adverse  reactions, or side
  effects — unwanted reactions  to medications. This type of reaction is
  quite common, and the manufacturer of the  medication lists these on
  the label. You MUST  carefully read all labeling. If you don’t have
  access to the label, then don’t ﬂy while using the  medication.

  Look for such key words as lightheadedness,  dizziness, drowsiness, or
  visual disturbance. If  these side effects are listed or if the label
  contains  any warning about operating motor vehicles or  machinery,
  then you should not ﬂy while using  the medication.

  Side effects can occur at any time, so even if  you’ve taken the same
  medication in the past  without experiencing side effects, they could
  still  occur the next time. For this reason, you must  never ﬂy after
  taking a medication with any of  the above-noted side effects.

Calling an AME is the official word.  You can get a pretty good idea of what he's likely to tell you from this page at LeftSeat.com -- so if that page says that X isn't approved but Y typically is, that's probably a good starting point for where to start the discussion with a "real" doctor if you're about to be given a prescription.  (Not knocking AME's, but many pilots have the doctor they see when they're sick, separate from their AME.)

That said, nothing on the internet carries as much weight as what your AME tells you, so consider this advice worth what you paid for it!


How can aircraft land on choppy water? What plane can land the slowest on the water? What plane can land on the choppiest water? Is there a way to land between the waves?

Depends on how bad is the sea state, but the general technique for seaplanes is to land parallel to the swell, preferably on top of a wave:

  When landing on a swell system with large, widely
  spaced crests more than four times the length of the
  floats, the best landing heading parallels the crests and
  has the most favorable headwind component. In this
  situation, it makes little difference whether touchdown
  is on top of the crest or in the trough.

If forced to land against the swell, it is recommended to land on the backside of the wave:

  If crosswind limits would be exceeded by landing parallel to the swell, landing perpendicular to the swell
  might be the only option. Landing in closely spaced
  swells less than four times the length of the floats
  should be considered an emergency procedure only,
  since damage or loss of the seaplane can be expected.
  If the distance between crests is less than half the length
  of the floats, the touchdown may be smooth, since the
  floats will always be supported by at least two waves,
  but expect severe motion and forces as the seaplane
  slows.
  A downswell landing on the back of the swell is preferred.

How high are the waves? Timing into the wind, proper flare and try not to capsized I reckon. Never sideways to the waves.


Are pilots generally trained for crosswind landings? A YouTube footage of a KLM Boeing 777 landing at Schiphol airport in the Netherlands is certainly scary as the plane bumps and weaves and rolls from side to side.

Are pilots generally trained to handle such eventualities (or are such landings common in certain regions of the world?) or was everyone involved including the pilot taking a risk in this case without diverting the aircraft to a nearby safe location?

Of course yes.

Crosswind landings, like the one in the video you linked, are very common. In fact, landings with no wind or only headwind are rare.

There are several techniques pilots are taught during their extensive training to land aircraft when there is crosswind. The Wikipedia article I referenced above lists them. Since your question isn't about them, we won't discuss them.

Certainly, extreme weather situation are not very common. Some parts of the world experience extreme weather more than other areas. Diverting to other airports is not always an option and in some cases, once an airplane is on the approach, going around becomes impossible.

In steady winds, even when strong or very strong, there is no excuse for bumping around like crazy. You have the "concept" of a "stabilized approach", and only turb is a valid reason to destroy a stabilized approach. In turb that's a different story, but then you still would have to explain why you even attempted the landing. If turb is too strong, it's a good reason to divert. The famous Lufthansa case made the media (and YouTube footage) several years ago where they even had a wing strike on the left side, when tons of other aircraft had cancelled. These two pilots pressed on, seemingly suffering from the eponymous get-home-itis, and you see the result. So ... even turb is not always a valid excuse, because diverting is a safer option (assuming you don't HAVE to land because of low fuel or similar -- but then you'd even have less excuses, because you shouldnt' fly into turb with low fuel, etc.).


How can I avoid flight simulator software reinforcing bad habits? While looking into getting into flying I've seen in several sources that using flight simulator software typically creates and reinforces bad habits. Most articles say that it reinforces "instrument" flying which is not practical.

Is there some other action I should incorporate into learning to fly that would maybe help me avoid focusing too much on the instruments? Or would the simple introduction of things like pedals, flight sticks, etc be enough help to avoid this issue?

I posted this answer on FB a while back:
I’m a commercial pilot as well as a flight sim fan with somewhere in the neighborhood of 7000 hours logged on Flight Simulator and Falcon 4.0 games.  I disagree with the assertion that the sims are so different from the real thing.  While it is true that the kinesthetics of being in a real airplane are different from the sim, the handling and behavior of the sim is so close to the real thing that the same mistakes I make in the sim I make in the real thing.  They are also very effective platforms for practicing instrument flying and approaches.  It’s not surprising that Redbird makes use of a proprietary version of FSX for its flight simulators.
That being said there are several notable areas where the entertainment sims can be off from the real thing:

Avionics may be simulated poorly or unrealistically.  Alabeo payware is a major offender here.

Games do not adequately simulate weather hazards.  Flying into a thunderstorm in FSX is a benign experience.  This can kill you in real life.

ATC interaction is appallingly unrealistic, akin to having an adult conversation with a talking Barbie doll.  Probably the worst offender is XPlane’s default “ATC” which is absolutely nothing like the real thing.

Airport and navigation databases are terribly out of date and cannot be updated.  This appears to be changing with the advent of Flight Simulator 2020 which periodically updates its airport and nav databases, but FSX and XPlane are horrible.  This dramatically affects realism when flight planning IFR flight and shooting practice approaches, as, at least in the case of FSX, the default approaches are now 14 years out of date!

Terminal departure and arrival procedures are often not modeled properly or absent altogether, making operations from major airports unrealistic, especially for jet flying.

Considerable errors exist in the default terrain as well as airports. Some of the worst instances I’ve found were in FSX and include an airport in the middle of a 1000ft deep pit.  Ft Worth Meecham Intl. has the peculiar obstacle hazard of floating houses along the glidepath to runway 35.  Gustaf III / St Bart’s and Courchevel are wretched as well.

Some sims (FSX) suffer from control lag ie a delay time between control input and movement of the control surfaces, creating an unrealistic control response which makes it difficult to fly demanding maneuvers eg aerobatics accurately.

Some sims are developed around certain types of aircraft and do not replicate other aircraft or systems well.  FSX turbine and jet engine simulation is a great example of this.

Edge of the envelop flight characteristics such as spins and aerobatics are often modeled poorly or completely absent in these games.

Ground handling and and takeoff and landing characteristics are unrealistic compared to the real thing.  This is really apparent when flying tailwheel airplanes, particularly in XPlane.

There are fixes to some of these problems.  Some payware aircraft are extremely realistic - VRS’s F-18E and RealAir’s BE60 Duke and Lancair Legacy quickly come to mind as does PDMG’s 737NG and 777 aircraft.  Additional addons for weather as well as cockpit avionics like Flight1’s GNS430/530 and GTN650/750 GNSS heads are great examples as they use the Garmin trainers as their core. ATC add-ons and Live ATC in multiplayer games alleviate the controller flaws in the default software.
If  you do intend to use a desktop flight simulator software to train on, I suggest that it be used as a means to augment actual training in an aircraft following the instructions of a CFI.   This allows you to accomplish a lot of training on basic airmanship and a fraction of the total cost compared to actually going out flying in the real airplane. While it diminishes the principle of effect during learning, It can accomplish a great deal of goals in terms of rote procedures and psychomotor practice.   Again a good flight training syllabus should be followed under the direct supervision of a certified flight instructor combined with actual flight training in an airplane.  When that’s done desktop flight simulators can be extremely useful to a budding airman. I learned how to do crosswind landings using FSX  and have always been very good at them ever since.   If training is done solely by means of a desktop simulator and self-didiaction,  this can lead to negative outcomes, such as incorrect use of the flight controls.  I remember one point early on in my flight training, there was another student working with a flight instructor who had logged in a lot of hours in desktop flight simulators by himself prior  to beginning flight training.   He had developed the undesirable habit of using elevator trim in order to maintain altitude during cruise flight wile playing sims and it took a great deal of work from his flight instructors to break him of this habit and install the correct use of trim in order to neutralize control pressures when in cruise.

First of all my advice,

Start using X-Plane it ACTUALLY simulates aerodynamics. Instead of using same set of weather download weather from the internet. If you wont do that simply use random weather generation.

Don't fly the same route. Did I ever tell you the definition of insanity is? Insanity is flying the exact same route over and over again exact same way and expecting this time it will be a different flight that will improve you. Over and over again with exact same techniques.

Do winter flights it will give you habit of turning pitot heat on. Don't underestimate what night flights can do to you


What licenses/endorsements or type ratings do you need to fly a fighter jet? As the title says, what endorsements and licenses do I need to obtain before I can legally fly a decommissioned single seater fighter jet or trainer jet (like a L-39 Albatros or even a F22 when the time comes)

Simply assume I could afford everything the jet needs and the jet itself, I am aware that a lot of jets (mostly newer) will never see civilian pilots.

I am mostly asking for the Netherlands / EU, but I am interested in American laws as well, if there are big differences.

In the US, the FAA's requirements for obtaining authorization to fly former ,military aircraft is included in 8900.1 Volume 5, Chapter 9, Section 2.

It is quite lengthy and covers more than just former military aircraft. As others have pointed out, most of these aircraft do not have a Type Certificate. They normally have a Special Airworthiness Certificate in the category Experimental Aircraft  Exhibition. Requirements to fly the aircraft are spelled out in the aircraft's operating limitations which are issued with the Special Airworthiness Certificate.

From 8900.1:

  A.    Background. The FAA requires pilot authorizations to operate
  some aircraft in the experimental category, including some former
  military, all turbojet‑powered (for this section, all turbojet‑powered
  includes all turbofan‑powered), all rocket‑powered, and all large
  (over 12,500 pounds maximum gross takeoff weight (MGTOW)) aircraft,
  and any other aircraft requiring specific pilot skills. Examples of
  such models are the Northrop F‑5, Bell P‑63, MiG‑15, Ju‑52, Mi‑24, and
  the BD‑5J. The FAA also requires authorizations to act as PIC of large
  or turbojet‑powered aircraft undergoing type certification.

  1)    The requirement for an FAA authorization to act as PIC of
  certain experimental aircraft is contained in the FAA‑issued aircraft
  operating limitations. Pilots are required to comply with the
  FAA‑issued operating limitations by 14 CFR part 91, § 91.9(a).

  2)    Because these aircraft are not type certificated (TC), a type
  rating is not available. In the absence of type ratings for these
  aircraft, it is the FAA’s objective to ensure, for the pilots flying
  these aircraft, a level of safety and proficiency similar to what is
  available for an aircraft with a type rating.

The specific pilot requirements are also spelled out in the document:

  A.    Former Military Turbojet/Turboshaft‑Powered Aircraft. To be
  eligible for an authorization to act as PIC of a former military
  turbojet/turboshaft‑powered aircraft, an applicant must:

  1)    Possess at least a U.S. private pilot certificate with an
  appropriate category and class rating for the configuration of the
  aircraft;

  2)    Hold an instrument rating;

  3)    Possess at least a valid U.S. third‑class medical certificate or
  equivalent (U.S. Military Flight Medical or U.S. driver’s license in
  accordance with the FAA BasicMed process (pilots using BasicMed may
  not exceed 250 knots indicated airspeed (KIAS)));

  4)    Have logged a minimum of 500 hours of pilot flight time in the
  aircraft category and have completed the U.S. armed services
  qualification checkout described in this section; or have logged a
  minimum of 1,000 hours pilot flight time, including 500 hours as PIC
  in the aircraft category, and have completed the training requirements
  of this section; and

  5)    If the aircraft is capable of supersonic flight, have a minimum
  of 250 hours of pilot flight time as PIC of a fixed‑wing
  turbojet‑powered aircraft, in a Group V, VI, or VII aircraft (see
  Figure 5‑173), or present proof of completion of a U.S. military
  qualification in a supersonic turbojet‑powered aircraft.

  B.    Former Military Propeller‑Driven Airplane. To be eligible to
  serve as PIC of a former military propeller‑driven airplane that has a
  MGTOW exceeding 12,500 pounds, or which has a horsepower rating of
  more than 800 horsepower and a VNE that exceeds 250 knots, an
  applicant must:

  1)    Possess at least a U.S. private pilot certificate with an
  appropriate category and class rating;

  2)    Possess at least a valid U.S. third‑class medical certificate or
  equivalent (U.S. Military Flight Medical or U.S. driver’s license in
  accordance with the FAA BasicMed process (pilots using BasicMed may
  not operate an aircraft with a MGTOW above 6,000 pounds));

  3)    Have logged a minimum of 500 hours of pilot flight time; and

  4)    Have completed the training requirements of this section.

That last item can be a challenge as it requires finding someone with the proper authorization to provide the training.

More information is available at the FAA Vintage & Experimental Aircraft Program web page.

In the United States:

Legally: A private pilots license, and in the case of the F-22 a multi engine rating (since it has two engines) as well as a type rating  per §61.31 since they are turbo jet aircraft. However interestingly neither of those aircraft are on the FAA's type rating list which may be an issue. There is no legal minimum amount of hours beyond those required to get the prior listed ratings.

Practically: If you want to actually fly it and get it insured... An instrument rating, a whole big chunk of hours at least some in high performance aircraft, a fair bit of multi engine time for the F-22 and prior time in type never looks bad.

Actually owning one is addressed here.


How were large pieces of the A300-600ST and the B747LCF transported? I will present my reflection based on the Airbus A300-600ST Beluga and I suppose the reflection is the same with the Boeing B747LCF Dreamlifter:

The A300-600ST was built because its predecessor (the B377SGT Supper Guppy) was not large enough to transport future aircraft's large pieces. Those pieces are too large to be transported by train or by road.

But the A300-600ST's pieces must have been transported to build the aircraft. Some of the A300-600ST's pieces must be larger than the pieces this aircraft is designed to transport. So I'm puzzled because I cannot figure out how large pieces of this heavy transporter were transported to its assembly site. The same reflection goes with the B747LCF.

The answer may be that parts were transported the same way A380 parts were transported

  The A380’s size means its fuselage and wing sections are shipped via a surface transportation network that includes specially-commissioned roll-on roll-off ships to carry these sections from production sites in France, Germany, Spain and the United Kingdom to the French city of Bordeaux. From there, sections are transported by barge along the Garonne River to the Toulouse final assembly line.

From Airbus - TRANSPORT OF MAJOR AIRCRAFT SECTIONS

According to All about Guppys

  The A300-600ST was built in Toulouse, France.

All the smaller pieces would have fitted into an existing transport aircraft.

The A300-600ST aircraft were built new. The sections were built by companies within the consortium, and probably shipped similarly to other Airbus parts to the final assembly location.

The 747 LCF aircraft were not built new. The aircraft were acquired second hand from airlines, and sent to Taiwan for the modifications. The modified fuselage sections could have been shipped individually and assembled on site. Shipping options are similar to those of other large aerospace parts and include sea, rail, and air.


Is a stall warning horn required to fly? I need an answer in reference to 14 CFR 23.207. I looked there and couldn't say 100% if it was a yes or a no.

No, many aircraft don't have them, like the Cherokee since it uses a gear warning horn. The horn signifies that the gear isn't down and you don't want to confuse that with the stall warning, so they don't have one.

23.207 says that an audible or visual indication is not required as long as the aircraft exhibits a "warning" 5 knots before the stall, in the case of the Piper Comanche the warning that satisfies the requirement is the stall buffet.

The relevant section of 23.207 is part (b):

  (b) The stall warning may be furnished either through the inherent aerodynamic qualities of the airplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual stall warning device that requires the attention of the crew within the cockpit is not acceptable by itself.

So the stall buffet, as long as it is pronounced, is adequate indication of a stall to satisfy 23.207.

The answer above is just flat-out wrong. It makes no difference whether or not certain airplanes have them or not when it comes to airworthiness.
The real answer is it depends...
91.205 does not include a stall horning but that doesn’t mean the Type Certificate Data Sheet for the plane you are piloting contains something different.
For example, a Cessna 172’s TDC (3A12) explicitly states that a stall warning horn is REQUIRED for the plane to be, well, a Cessna 172. Therefore if you are about to take off in a 172, you technically need an operational stall horn to be airworthy.
Generally speaking, you need to consult 91.205, the TDC for the plane, any STCs (supplemental), and then the MEL from the POH and probably in that order.
I highly recommend listening to the Max Trescott’s Aviation News Podcast episode 151 on airworthiness where they go through how to determine if a piece of equipment is required or not (hint: they talk about the stall horn!).


How do stealth aircraft get ATC? I believe that all aircraft must be controlled under ATC's instructions to fly safely especially when take-off and landing. And, most ATC instructions are conducted by ground radar which controllers use.

But I know that the stealth aircraft (including B-2, F-22 etc.) aren't captured on radar display owing to their stealth ability. If so, how does a controller give instructions like radar vectors to stealth aircraft?

I know that there's are primary and secondary target when using radar, and the controller must use primary target to vector aircraft. I guess stealth aircraft can be captured by secondary radar but not primary target.

The concept of ATC is based on primary radar targets, secondary radar targets and radio communication being used to determine the position of aircraft and establish separation.

The concept of stealth aircraft is to reduce production of primary radar targets and being able to turn off transponders to disable secondary radar targets being visible. Stealth aircraft also do not communicate on frequencies during tactical missions, they are designed and meant to reduce radio emission to enable the stealth features.

If they are not on a tactical mission and stealth is not required, they will simply turn on their transponders and communicate with ATC on the required frequencies.

They attach radar reflectors so as to be visible to ATC's primary radar. This is in addition to turning on the transponder (secondary radar).


In Spain, can I land and take off from my own property? I have a property in Spain with a big field; is it legal to take off from and land on your own property in a light aircraft?

It depends on your local and national regulations.  In some jurisdictions, local municipalities can regulate use of land in that way, and in others they can't.  So first check with Spanish national regulations (if separate from EASA) on what constitutes an aerodrome or airport to see if there are any restrictions on use of an unlicensed piece of land as an aerodrome (probably not), then check with local municipal regulations or zoning or use bylaws that may restrict use of your land as an aerodrome (a definite possibility).

No, unless you present a project of the airfield and get it approved by the municipal and aviation authorities. Not impossible, but very slow. Think in two or three years of negotiations before you can even start construction...


Where did the terms QNE, QNH, and QFE come from? In the aviation community (at least outside North America), the terms QNE, QNH, and QFE are used to describe standard pressure, local altimeter, and field elevation, respectively.

But what is the origin of the "Q" code names?

QNE, QNH, and QFE are Q Codes - the Q Codes are designed for telegraph (or radiotelegraph) use where information is transmitted in morse code and brevity is essential (e.g. "QNH KJFK 2992 INS" is much shorter to tap out in morse code than "JFK Altimeter 29.92 inches of mercury")

They are still used in verbal communication (radiotelephone), though much less frequently.
ICAO defines a list of standard Q codes for use in aviation (this site has a list).

Regarding the choice of Q as the prefix for these codes, this is to avoid confusion with station callsigns. The ITU currently will not assign prefixes beginning with Q to any country.
(There may be further historical reasons behind the choice of "Q", but I'm not aware of any.)

One of my PPL textbooks briefly discussed the origins of QNH. Unfortunately I can't for the life of me find the correct passage, so I am unable to reference this properly. But from memory:

It dates back to the early days of navigation when the main communication method was morse code through the radiotelegraph.  The aircraft, wanting the atmospheric  pressure for altimiter calibration, would basically ask the ground station "I have a question - what is the atmospheric pressure at normal height?" The 'normal height' reference over time became the sea level reference that we use today.

So, because this question was so frequently required - and therefore an awful lot to communicate through morse code - it was abbreviated. "I have a question" became Q, "what is the pressure at normal height?" became NH - the message transmitted therefore was simply QNH.

I presume the other Q codes evolved in a similar manner.


What triggers the PTU (Power Transfer Unit)? As highlighted by this answer and by this page the PTU (power transfer unit) is an hydraulic driven pump. It gets energy from one hydraulic system and uses it to pressurize another hydraulic system.

What triggers the functioning of this pump? Is it automatic or manual? Is this pump available even if a leak is detected in the hydraulic system it tries to restore pressurisation to?

(A320 PTU (Vickers), source)

The Power Transfer Unit is well known on Airbus due to its barking-like sound (refresher: Video of a PTU in action). The sound comes from a pump which creates a 3,000 psi pressure being quickly switched ON and OFF.

(Source: Youtube)

The PTU is a safety system to ensure hydraulic pressure is available, specially at takeoff, even if one or two hydraulic circuits have failed.

The PTU can restore pressure in a deficient circuit without actually transferring fluid from the working circuit to the deficient one. This prevents throwing hydraulic fluid from the working circuit overboard if the deficient circuit is leaking.

The PTU is always activated, but is actually triggered based on a pressure differential.

When is it activated?

On Airbus A320 series, the PTU is actually the second source of pressure for the yellow and green hydraulic systems, after the EDP. It's always ON, ready for the pump activation if there is a pressure drop on the yellow or green hydraulic system and the differential pressure is more than 500 psi.

  Airbus A318, A319, A320 and A321 aeroplanes are equipped with three
  hydraulic systems and they can be safely controlled with only one
  system operative. A bi-directional PTU enables the yellow system to
  pressurize the green system, and vice versa, without the transfer of
  fluid from one system to the other.

  In flight, the PTU operates
  automatically if a pressure drop in one of the systems is detected.
  The PTU ensures optimal hydraulic system availability for take-off.
  (Source: EASA safety bulletin)

Automatic inhibition below 1,500 ft in case of leakage

The PTU cannot restore the correct pressure in a circuit with a permanent leak. In this case, the PTU, and possibly the working hydraulic system, eventually overheat. The crew receives a failure amber caution on the ECAM display and, up to recently, had to switch OFF (inhibit) the PTU manually to prevent damage.

  In case of loss of hydraulic fluid of the yellow or green system, the PTU
  cannot pressurize the failed system and must be switched OFF as
  required by ECAM procedure to avoid a PTU overheat which may occur two
  minutes later.
  (Source: EASA safety bulletin)

A320 PTU switch (source: Baltic Aviation Academy which, by the way, has plenty of quality training videos)

To avoid distraction from non-essential warnings during takeoff and landing, the ECAM message is not displayed when airborne below 1,500 ft height. There were several incidents (e.g. G-EZDM) where overheating became harmful before the amber ECAM message appeared at 1,500 ft, causing the temporary loss of a second system. Airbus added logic for automatic PTU inhibition when the aircraft is airborne, but still below 1,500 ft.

The previous quotes are from an EASA bulletin related to this modification (also detailed in Safety First, the Airbus safety magazine), with a failure scenario that had to be prevented:

Principle

A PTU is connected to two independent hydraulic systems: The first to drive an hydraulic motor (or turbine) mechanically connected to a pump. The second hydraulic system is pressurized by the pump.

PTU principle, source

PTU can be reversible (each hydraulic system can drive the motor or be pressurized by the pump) or not (the same system always drive the motor).

(Actual PTU schematics, source)

The A320 has a yellow hydraulic system pressure indication on the ECAM which shows xx =even the press by edp or by yellow elect pump = the press txd replaced -the power to txd measured ok 28 v=xx indication on yellow sys is always with press applied or without.


How does trim work on an A320? In the very interesting answer from Jan Hudec to a question about the various flight control computers on Airbus planes, two different means to trim the aircraft are mentioned: The stabiliser and the elevator.

How does this work in practice? How is the aircraft trimmed in flight, both as seen from the flight deck (i.e., the user interface to the pilots) and as actual input to the control surfaces?

The faster an aircraft is, the wider range of elevator deflections it needs. And so do aircraft with large change of weight (amount of fuel used) during flight. However larger elevator deflection causes higher drag. It is more efficient to move the whole horizontal stabilizer instead. Therefore jet aircraft generally have the forward part of the horizontal stabilizer movable.

Now it would be possible to simply have the whole stabilizer move. And supersonic aircraft generally have just that. It is called stabilators. However having the stabilizer split lends itself to elegant solution for trim.

This takes advantage of the fact, that the aerodynamic forces tend to put the elevator in the position of lowest drag almost straight (slightly bent in direction of less lift) behind the forward part. So when the forward part is moved, the lift changes without changing the force on the elevator. So the elevator is used for the small adjustments where the elevator is intended to return to the neutral position, which the aerodynamic forces help with, and the stabilizer is used to trim for current airspeed.

In aircraft with mechanical controls, the elevator force (or a fraction of it via power drive) acts directly back on the control column and the pilot can feel it, while the horizontal stabilizer is actuated via mechanism that holds selected position (may be electrical with jack-screw like on DC-9 or hydraulic, but with no feedback) and connected to the trim, which is usually pair of large wheels on the sides of the centre console.

Now in Airbus A320 and all newer models the side-stick does not have mechanical link and the pilot does not feel the force on the elevator anyway. In normal law, the ELACs automaically adjust the elevator and stabilizer so that with side-stick in neutral position, the aircraft maintains 1 G vertical acceleration and therefore straight flight (at any flight path angle). Since the trim wheel does have direct mechanical link, it turns as the ELACs (or SECs) adjust trim.

However the distinction between elevator and trim is still useful in case of failure. When the system degrades into direct law, the side-stick position corresponds to the elevator deflection and the trim wheel position corresponds to the stabilizer position. Since the side-stick still returns to neutral position, the distinction of using the elevator for momentary adjustments and trim to balance the aircraft to fly (approximately) straight at current speed holds (just because the side-stick is spring-loaded, the force needed to deflect it does not increase with speed as it does for mechanical controls).

It is fully hydraulic, the active power is the hydraulic even when you act directly on the wheels, that’s why there is no handles to the Wheels, the wheels will control a valve block to drive the screw.

There is no thumb switch to operate the trim, when you move the stick the elevators are operated for short term action to get the desired load factor, followed by the trim which moves automatically to maintain that load factor, and replaces at long run the elevators effect, thus at long run the THS and the elevators are aligned which reduces the drag.


Why is the range of transponder digits 0 to 7 rather than 0 to 9? As a controller on IVAO I sometimes assign codes like 0168 and find out later that the code isn’t valid. For me, the range 0-9 seems more logical. Why do we have to use octal numbers and not decimal?

The four-digit transponder code that is entered by a pilot is an octal number rather than a decimal number, and in the octal numbering system, only the digits 0-7 are valid.

As far as why, internally it's actually a 12-bit binary number and octal works really well since can be used as a "shortcut" for entering groups of three binary digits at a time (000 - 111, which is 0-7 in octal).

If it were designed today, with the additional computing power and software complexity available, it would be possible to use a decimal number even if it is stored as binary internally, just so that it is more familiar.  At the time that the system was created though, changing the dials directly set the code in hardware and doing the conversion would have been much more complex / difficult / expensive.

In short, it was convenient for the engineers and manufacturers, and just an oddity for the end users, so they left it that way.

In computer systems, everything is binary. This is due to the logic circuitry only having 2 states, high and low voltage. Because of this, decimal wouldn't be as simple to convert to binary as octal or hex are.


Does the crew have a professionally mandated responsibility to inform passengers of a potentially fatal emergency? This follows on from the question here on an incident wherein a passenger asked crew about an aberrant situation during a flight.

Gathering from the answers to the question, flight crew's priority is to handle the emergency, and part of that is keeping passengers cooperative and calm, whether by informing them of details or perhaps omitting them in the interest of maintaining decorum.

However, in the case of a potentially fatal emergency, wherein passenger death is probable, despite the interest to maintain calm, does the crew have a professionally mandated responsibility to inform passengers? There are obviously moral and ethical motivations for this, but these might be beyond the scope of the site and as such I am asking how these issues are dealt with.

By "professionally mandated responsibility," it can be by laws in the appropriate jurisdiction, regulations and internal policies by the airline, common practice, or guidelines set by an aviation body.

Would the act of informing passengers they may die be considered "professional" or "a responsibility of the crew"? No.

And if I may argue, it's the opposite: it is unprofessional for trained flight crew (either pilot or cabin crew) to behave this way.

The shortfalls of this action is obvious. Panic would instantly spread among the cabin. Many people would start behaving irrationally when they believe that death is imminent (hey, not everybody is strong psychologically). This could potentially turn a survivable situation into a deadly one.

In dangerous scenarios, anyone assisting needs to give assertive instructions. We don't tell people why they are doing it. We give very simple, but firm instructions such as "push!", "jump!". Fire fighters and other rescue workers also do it this way.

Telling people "uhhhh, I don't think we can make it" works against the goal of ensuring everyone has a best chance of survival, which is a professional responsibility of any crew member on a passenger flight.

Legally, there are no regulations, industry practices, or airline SOP that I'm aware of, that mandates informing passengers about the potentially fatal outcome of their flight.

Realistically, there aren't that many scenarios where this is possible. If it's a small problem such as high oil temperature or failed hydraulic pump, you won't even notice. If it's a stall or loss of control you'd be screaming already. If it's a inflight breakup you'd loss consciousness in less than 30 seconds. If it's a cabin fire you'd see cabin crew fighting it with fire extinguishers.

That leaves scenarios where the aircraft is stable in the air, but may break up upon landing. Examples would include landing gear malfunctions, flap malfunctions (causing very high landing speed) and total engine failure from high altitude. Historically, most of these incidents end up well. Spending the time to educate passengers emergency procedures (such as counting the number of rows to various exits; briefing how to open the emergency door) is more constructive then saying "On behalf of XXX Airlines, it is with sincere regret to inform you that our aircraft suffered a catastrophic failure and this may be the last moments of your life".

That said, I offer the following:

If you've been told to adopt the brace position, you may consider that it is in the opinion of the flight crew that severe injury and/or death is likely.

If there is a catastrophiv failure duch as inflight break up of a wing or a structure and communication is possible..I would say "Brace and lets pray". Not saying anything and knowing death is inevitabpe is also cheating them of their last moments to say or do what they desire..if only to think of their loved ones!


What navigation publications are required when flying from KSNA to KAVX? If I'm flying to Catalina Island (KAVX) from John Wayne Airport (KSNA), which is 30 miles over water, what navigation publications are required to be on board for the route of flight?

You'll need the navigation publications appropriate to your flight.  If you're flying under VFR, then you'll need the appropriate sectional chart, and should have airport diagrams.  You'll need to be aware of the airspace and how to communicate and navigate in it.  You should have taxi diagrams.  For VFR flying, I've always made a practice of having the appropriate terminal charts, sectionals, WAC's, and airport publications.  I have also always carried IFR enroute charts, as these provide useful information about communications enroute, as well as airspeed and navigation information.

These days, a subscription to Foreflight usually covers it, and I've flown all over using little else.

If flying IFR, you'll need appropriate IFR publications.

You should have a copy of the airport information, airport facility directory, or equivalent, etc.  If you don't carry and reference the current data, and end up getting busted, you'll have little to fall back on as an excuse.


Which is longest Oceanic crossing for any commercial flight route? During oceanic crossings, there are limited to no terrestrial radio communications available, so I would think that most flight routes are designed to minimize ocean crossing time.

Which commercial flight route have the longest oceanic crossing?

For the longest  Oceanic Crossing, the following are the top three contenders:

Sydney to Vancouver
Melbourne to Los Angeles
Auckland to Vancouver

Out of this, 1 and 2 pass over a few islands on their way, 3 does not pass over any landmass.

Have a look at this : www.gcmap.com

Image :

(Image Source: www.gcmap.com)

There are also SIN-LAX or SIN-SFO handled by Singapore airlines or United. The flight time is around 17h. Singapore to New York would be even longer, but I am not sure if they fly over Pacific Ocean...


What is the effect of the Load Factor on wing Structures? I am quite confused with the definition of Load factor and how it applies to the wing structures of an aircraft.

For example, you have an Aircraft being subjected to a Load Factor of 2 and whose total mass is 5000kg and wings + fuel mass is 1500kg, and are asked to calculate the Inertia Loading of Said wings.

Would you multiply the weight of the wings by 2? Or does Load factor only affect the lift and not the weight?

https://en.m.wikipedia.org/wiki/Load_factor

As a start for an aircraft the load factor is the ratio of total lift to total Weight

An easy way to imagine this concept is to understand the idea that when the aircraft is flying at high speed during cruise with a small angle of attack the load factor is very close to 1, this corresponds to the first case on the left of the picture here below

Now what is lift, the picture here below is self explanatory, so it is important to understand that the lift is not always an upward vertical force; when the aircraft is under a coordinated bank angle the lift has two components ; horizontal and vertical.

Now to simplify we shall consider the lift to be totally produced by the wings, while in real flight it is the result of the wing, the body, and the tail.

Since the Aircraft is subjected to a load factor of 2 this means the aircraft as a complete body is subjected to a total lift( not vertical) equal to twice the total weight of the Aircraft

The lift produced is therefore: $2\cdot(5000 + 1500)\,\mathrm{kg}\cdot g = 13000\,\mathrm{kg}\cdot g = 128\,\mathrm{kN}$

If we consider we are in the steep banked turn indicated on the right of the picture above:

The weight of the aircraft body without the wings is a downward force on the root of the wings

Also the wings have their own distributed weights, that produces a torque to the root of the wings

Also the distributed fuel in the wings produces a torque to the wings roots

Also each wing is subject to a distributed lift of $\ 6500\,\mathrm{kg}\cdot g = 63.8\,\mathrm{kN}$

The exact computation are difficult because

we don’t know the bare weight of the wing nor the centre of gravity of the wing
we don’t know the distribution of the fuel in the wing, so we don’t know the centre of gravity of the fuel of each wing.

Therefore it is impossible to calculation the shear forces and the torques at the wings roots.

Nevertheless I imagine the main question concerns the relationship between lift and load factor, And here the most important point is to understand that the lift is not always a vertical force

As a start for an aircraft the load factor is the ratio of total lift to total weight

Since the Aircraft is subjected to a load factor of 2 this means the aircraft as a complete body is subjected to a total lift equal to twice the total  weight of the Aircraft

The lift produced is therefore 2x(5000 + 1500)= 13000kg

The downward force that opposes the lift is the total weight of the aircraft that is 6500kg

The net upward force on the wings is 13000-6500=6500kg

To appreciate intuitively what is load factor, please note that when the load factor is equal to « 1 » the aircraft is not subject to any vertical acceleration, it’s vario is constant

An easy way to imagine this concept is to understand the idea that when the aircraft is standing in the runway or parked, it's load factor value is 1.

Note: For completeness please note the answer is dealing with forces therefore all above Kg units refer to kilogram-force, otherwise you may multiply all the results by « g » to obtain Newton’s.

On the other hand the notion of load factor applies too to satellites therefore « g » should be theoretically considered as a variable function of altitude.


Can a commercial airplane overtake another airplane going in the same direction? If there are two commercial airplane flying towards the same destination, on the same flight path, and the second plane is being faster than the first plane, is the second plane allowed to overtake the first airplane?

If so, how close are two planes allowed to fly while overtaking each other?

Faster aircraft often overtake slower on the same routing. This is usually accomplished by flying at higher or lower altitudes. This is called vertical separation. They can also be separated laterally by radar vectors so that they are 3-5 nautical miles apart. The exact distance will depend on the ATC standards for the particular airspace.

Often as they approach the destination ATC will ask one aircraft to speed up and one to slow down slightly. This can sometimes allow the faster aircraft to pass the slower aircraft, but it also insures they have the required separation when they are on approach to land.

Aircraft obviously fly at different speeds which you can see in the Flight tracking app. Aircraft also sometimes fly along the same paths following navigational beacons. When they are not under air traffic control they need to be able to overtake one another. In this event, 14 CFR 91.113(f) specifies that the faster-moving aircraft must overtake on the right-hand side, or starboard side, of the slower aeroplane.


How can I tell if an aircraft is equipped with fly-by-wire or with a FADEC? Can anyone help me with a link or advice on how I can identify whether an aircraft is fly-by-wire (FBW)?

I understood the function of FBW, however if I want to know if a SA227 or smaller type of aircraft has FBW, I am not sure how to identify it? Is there a link or a way to exactly say which type of aircraft have FWB and which don't?

The same applies for FADEC as well.

Only an aircraft model can be fly-by-wire or not, not an individual airframe of the same model.

Designing FAA/EASA certifiable fly-by-wire systems is extremely expensive, so only expensive aircraft, produced in large numbers, are going to have it. All Airbus since the A320 and Boeing 777 and 787 airliners are fly-by-wire, so are high-end Dassault bizjets. Recently the club has been joined by Bombardier, Embraer, Sukhoi, Irkut (Yakovlev) and Mitsubishi.

This doesn't include military aircraft, though you'll largely see the same players there with the addition of Lockheed, Northrop, MiG, BAE and a few other all-military contractors. Air forces have more need for fly-by-wire and are more risk-tolerant than airlines.

The SA227 is not fly-by wire. For the most part, if you have to ask, or if it's affordable below corporate level, it's probably not fly-by-wire.

EEC (of which FADEC is the most advanced subtype) versus hydromechanical engine control choice is specific to the engine and the airframe. It's not readily visible. An airframe will either have cables and hydraulic lines or sensors and wires. The majority of jet airliners currently flying use EEC or FADEC engines.

There are two ways to tell if an aircraft is fly-by-wire. The first is to open the access panels, trace the wires coming from the controls, and see if they lead to a computer or not. The other way is to look it up in the aircraft's documentation.

The same thing is true for FADEC, except that FADECs are specific to the engine, not the plane. It's entirely possible to replace a non-FADEC-equipped engine with a FADEC-equipped one and vice versa. So, if you're going to look up the answer, you first need to identify what engine it has.


Is it correct that a jet fighter can be used as a non-lethal (sonic) weapon? Imagine you have a crowd of people, who want to go to a certain territory (e. g. close to the border). An airplane flies over them such that when it reaches supersonic speed, there is a loud bang. People hear it, it hurts, and for several days they are deaf. That noise scares them off, and after some time most of them recover (i. e. there is no permanent injury to their ears).

I heard this story from a source I don't trust.

Can this be true? Could you, in theory, protect the border of a country from intruding crowds by simply flying over them (provided the crowds can't down the plane)?

Sonic booms from low flying aircraft, while loud, don't seem to cause hearing damage, as this F-14 pilot demonstrates during a Tiger Cruise air wing demonstration.

Now military fighters will sometimes make a 'show of force' in the form of a low altitude, high speed pass against threat forces which don't have a substantial IADS capability in order to motivate them to disperse under threat of employing ordanance on them if they continue belligerence.

UPDATE:  I found this story about an F-16 2-ship over Iraq on a CAS patrol mission.  The pilots get a radio call from desperate SOCOM operators pinned down by enemy troops at night.  The pilots cannot get a IR strobe to track for bombing, so the lead Viper uses a sonic boom delivered from a dive to frighten off the combatants.

A sonic boom can shatter windows on any building nearby and cause damage (sometimes irreparable) to any person close enough. It's a shock-wave, but with no ordinance. So, I would say that it MIGHT be non-lethal. and it might also kill the target, or render them deaf for life, or shell-shocked, or concussed, or any other sort of thing you could imagine after being hit with a pressure wave such as that (which is why it's not legal to break the sound barrier over land).


How can I calculate distance based on altitude and glideslope angle? How do I calculate the distance to touchdown when the glideslope angle is different from 3°? For example, you are 670ft AGL on a 3.2° glideslope approach; what do I change in the formula to calculate the distance?

Since the 1 in 60 rule of thumb yields a solution of 300 feet for every NM from the touchdown point for a 3 degree slope, use 320 feet for a 3.2 degree slope.  So 670ft, gives you a nadgers whisker over 2 nm.

To be a little more precise, 2.09375 nm ($\frac{670}{320}$)

Thanks to all for answers. The $\frac{1.97}{96}$ was not correct.

This is how you should do it:

$$3.2=\frac{670ft\times60}{3.2}=12,562ft=2.066NM$$


Does headwind on takeoff affect g force? I'm aware that headwind or tailwind does not affect rate of climb or descent but only the angle. I'm not sure if it affects the g force or not. I'd assume it affects g force because using trignometry, using SIN theta the vertical component increases as the angle increases. However a confirmation would be aappreciated.

In the takeoff run, the acceleration is less with headwind, but once in flight, the airplane flies within the mass of air. The fact that that mass may move in relation with the ground doesn't affect the magnitude of the forces involved in flight, so accelerations are not affected by the wind.

When you are only looking for the static acceleration that the pilot feels in his/her seat then the g-force is only a factor of the pitch attitude (theta). That is if we assume a stationary climb or descent, which by definition has a netto acceleration of zero. So 1g pulling the aircraft towards the ground, the more pitch attitude we have the more of the gravity has to be compensated by engine thrust to maintain an unaccelerated flight. This leaves less a smaller vertical g component. At 90deg pitch up the vertical component (from your pilot view) is going to be zero but the acceleration pushing you into the seat is now 1g (and engine thrust must equal aircraft weight). So in your fighter jet at 90 degrees nose up you will just feel as if you are lying on your back and you don't feel any vertical acceleration anymore, regardless of the wind speed.

Ergo the vertical acceleration felt by the pilot in stationary flight is
cos( theta ) * g, longitudinal acceleration on the pilot is sin(
theta ) * g.


Is there a way to avoid exhaust fumes when landing? I've taken a few hours towards my private pilot's license and each time we land I've smelled this plume of engine exhaust that we seem to fly/roll through just as we're touching down.  I must be sensitive to the fumes because I usually end up with a slight headache after a few minutes.  I haven't asked my instructor yet (because he may think I'm nuts) but is there any way to avoid this short of holding my breath?  I'm flying in a Cessna 152 for my training.

Smelling exhaust in the cockpit is not normal.  Tell your instructor and squawk the problem.  Bonus - turn it into a learning experience by arranging to be with the A&P when he decowls and inspects.  You can learn a lot about the engine that way.

If you are getting a headache from this you may have mild CO poisoning.  This does need to be checked out.

Dear Aspiring Pilot;

By all means; you have stumbled onto the most important issue of being a PIC [Pilot in Command]. You only let that happen ONCE without fully understanding
why it is happening. There are no little issues as a PIC.

Part of your pre-flight check walk around should have included pushing down on the 'nose' of the Cessna and check the condition of the shock on the nose-wheel.
I.E. leaks in hydraulic shaft, tire condition, [nails,glass?]. It also seems when you were checking the wing tanks for water and checking engine oil you would have seen a black 'smudge where the exhaust was leaking.

It is imperative that  walk around is done; It can point out little things like the fact that a '152' DOES NOT have retractable landing gear;


In which direction should a turn-back be made after an engine failure on a multi engined airplane after take off? In case one of the engines fails after taking off (let's suppose the left engine is the one that fails), which direction should we turn to go back to the airport? A left or a right traffic pattern?

That  depends on a lot of factors. Are you declaring an emergency? What altitude are you at what speed are you at when this happens etc?   What kind of aircraft are you flying? Does it have enough power to continue to climb on one engine? Some trainers do not.

For a typical airliner, loss of a single engine is not a big deal. The pilot will simply declare an emergency and get vectors from controllers as to where to go land again. Most airliners have plenty of power with one engine out and they don't have to worry about that. Smaller twin engined GA aircraft are a different story and may not be able to achieve a positive rate of climb on one engine, especially with the gear and flaps extended just after liftoff.  At low altitudes where this performance factor may be the case for the specific airplane you are flying, you may have to execute a forced landing in a clearing either directly ahead or off to your side, as a 180 deg turn to the airfield would be suicide.

As to maneuvering once an engine is lost, there is no requirement for this, save a pre-determined VFR traffic patterns for the departure airport.

If the engine out is an emergency and you cannot comply with either a controller's instructions or uncontrolled procedures, you are authorized as PIC to disregard any regulation as required to deal with the emergency.  This means any kind of maneuvering you feel will safely bring the aircraft back to the ground is acceptable.

I've read a lot of posts and comments amongst pilots about not turning into a dead engine on a twin; this is nonsense with one caveat - you must have sufficient airspeed in order to do this.  It depends on the aircraft in question but a good rule of thumb is that if you are at or above Vyse you can GENTLY turn into a dead engine.  The threat comes in attempting to turn into the dead engine at or near Vmc, minimum controllable airspeed on a single engine, where it may not be possible to arrest the turn due to thrust asymmetry.

You should turn according to your PLAN. In most cases other factors (like wind or the presence of obstacles) will trump any consideration of which particular engine failed. For this reason, the comments on "dead engines" are incorrect. Carlo's answer is more reasonable since he is pointing out that there are many factors involved. When you experience an emergency you don't have time to compute those factors.

Before ANY aircraft takes off, the PIC is supposed to make an emergency plan which includes the course of action based on all factors: altitude, wind, runway geography, traffic, etc.

If you experience an emergency, then you should immediately execute your plan which you made beforehand.

(I find it kind of scary that half a dozen people have responded to this question and none even mentioned an emergency plan. Are you guys not making emergency plans before you take off?)


Which way (if at all) do the ailerons need to be deflected in a full-rudder sideslip in a Cessna 152 or 172? Do you typically have to maintain an aileron deflection in a constant-heading full-rudder sideslip in a Cessna 152 or 172? If so, in which direction?  And why -- what is the source of the roll torque that needs to be countered>

Note that aileron deflection is not the same thing as bank angle.

Yes. If you apply full rudder with no aileron, you initially just get a flat skid, but then differential lift starts to have an effect and the inside wing drops because that wing has slowed down, the fuselage is obstructing some of the flow on that side, and if there is wing dihedral, it creates a geometric angle of attack differential. One or more of these factors generate the rolling torque.  It's called "roll/yaw couple".

Some airplanes roll with rudder-only input stronger than others.  On swept wing airplanes the effect is intensely magnified due to the wing sweep and they roll really hard once the yaw angle exceeds 10 or 20 degrees.  Pilots doing jet type ratings discover this right away on their first V1 cut (engine failure) on take off when they don't correct the yaw from asymmetric thrust fast enough and it's taking full aileron just to keep from flipping over.  Side slips are generally not done in swept wing airplanes except in some extreme circumstance.

So the amount of opposite aileron to maintain a constant heading side slip is a function of how strong the airplane's roll/yaw couple is.  A 172 or 152's roll/yaw couple is moderate and you will need some opposite aileron just to keep the wings level.  Plus, to prevent a skidding turn, the amount of aileron has to be more than the minimum required to keep the wings level because some opposite bank is also required to keep the heading constant or else the skid itself starts to pull the nose around. So you end up with quite a lot of aileron in, maybe one third to one half of the available travel, with the wing banked perhaps 10 to 20 degrees, to keep from turning.

There is a lot of variation from airplane type to airplane type and on some the roll/yaw couple is quite weak and it takes only light aileron inputs to hold heading in a skid.  On any airplane you are flying for the first time, this is something you experiment with to find out how strong the roll/yaw couple is and how much counter aileron is required in a side slip.

This maneuver, with constant heading and increased rate of descent to correct a high glide slope, is known as a "forward slip".

First, before attempting, speak with a qualified instructor familiar with the specific type of plane you are flying.

Second, practice cross controlled stalls at altitude to validate safe approach speed for that maneuver.  The 172 is extremely forgiving, but this must not be done at marginally low approach speeds (if you are high, you will rarely be slow, I did mine at 65 knots).

Thirdly, be mindful that the POH does not recommend trying this at 30 degrees of flaps as a tail pitch oscillation will result, due to flap and slip induced turbulence on your tail.

With the 172, roll coupling with rudder is much less than at cruise speed, so:

You are coming in at 65 knots (trimmed), 20 degrees of flaps, throttle at idle, and looks like it will be past the first 1/3 of the runway, decision:   1.  Go around  2. forward slip

If you are not too high and elect to do a forward slip in a 172, push the rudder all the way over.  This would probably be lethal in a low wing, dihedral aircraft due to roll coupling, but the 172 yaws with much less roll.

You will be seeing your old aiming point moving up on your windscreen.  The aileron is used to hold line with the runway, you just work it back and forth.  Once your (shorter) aiming point is achieved, smoothly center ailerons and rudder first, then use pitch to break glide path and round out for flare and landing.

You should not need to stay cross controlled while applying elevator.

As far as how much aileron is needed in the maneuver,  I do not recall it being close to what was available in either direction.

We want to SAFELY increase our rate of descent. Why full rudder deflection? To maximize drag while maintaining safe speed and AOA. Ailerons are used to counter the drifting and rolling tendency created by side force. This is a FORWARD SLIP. It could also be called a "flat or skid" slip. It works.

Now to consider the SIDE SLIP. Rather than increasing drag, we reduce VERTICAL lift component by rolling with ailerons. This can be done very gently to coax a plane floating in ground effect down to the runway.

Recovery from the forward slip uses the rudder, which is always functional, even when the wing is stalled.


Why force the nose of 737 Max down in the first place? Can someone here explain a pretty basic question that I have had  ever since this controversy came to light? I don't understand why any aircraft manufacturer, engineer, software developer, would make a device that forces the nose of the plane down. You can't land unless you're in control and landing safely is the only reason to go down that I know of. So I just don't get that as an initial thing, but the second part of that is, given the hazards of pointing the nose down, which are obvious even to me, why would you not design the system so that it's a warning, and allow the pilots who are actually sitting there to decide whether going down is a good idea or not? That just fundamentally, as a threshold issue, makes no sense to me at all. So I'm hoping you could help me understand. Thank you.

The main thing to avoid in aeroplane stability & control, is an aerodynamic nose up moment that is not commanded by the pilot. The uncommanded nose-up moment would not auto-stabilise, but rapidly get progressively larger with increasing angle of attack, and run away to a stalled aeroplane.

During certification of a passenger aeroplane, many tests are carried out to check if the airframe does not start to have a mind of its own.

If the pilot does not provide a control input, the airframe must return to the trimmed position.
Forces and inputs to move the aeroplane away from trimmed position must be such that there is an ever increasing force required to achieve an ever increasing nose-up position. The nose-up position must always be commanded by the flight control surfaces, elevator and stabiliser, in a predictable way.

One of the tests to be performed during certification is stick-force-per-g. Bank the aeroplane and start turning while pulling the stick back in order to maintain altitude. Then bank more and pull back more, in ever tightening turns. It must be progressively harder to pull back on the stick to maintain altitude, never easier.

It was during this wind-up turn that due to the engine configuration of the MAX an aerodynamic nose-up moment appeared, which would cause the pitch stick force to suddenly become less than expected. Not as bad as a runaway pitch, but still an undesirable situation when the pilot is still straining to maintain the manoeuvre. This is the situation that MCAS was originally designed for, to auto-compensate for this situation only. The aeroplane should always stabilise itself and manner of control must be predictable and within the reaction times of humans.

More info in the links in this question, very interesting articles which illustrate how MCAS design bloated from the original scope, under time pressure.

I think the issue for Boeing was the risk of falling behind Airbus in sales. So they modifed the 737 using far larger engines which because of limited ground clearance had to be mounted in such a way that increased the risk of stall during take off. So with a plane that is not as aerodynamic as it should be Boeing fitted a system to overcome the aerodynamic flaws, MCAS. It seems strange to knowingly produce a plane which is not as aerodynamic as its predecessor, but in their desperation to keep up with Airbus, Boeing did exactly that.


Do (or can) pilots observe religious fasts when flying? This question is about religious fasts like the Muslim Ramadan and others.

Is there a civil aviation regulation about this? Must a pilot eat and drink by the regulations (or abstain from flying), or is this an issue left to the pilot's personal decision?

Obviously if a flight takes long hours and the pilot can't eat and drink, or abstained from eat and drink for long hours before the flight, this can affect the pilot's performance. I don't know enough to say if it can actually impact safety but it is obvious that the claim would not be far fetched.

How is this issue addressed in airlines? For example in Muslim countries where I would expect a significant number of pilots to be Muslims, if a religious fast is widely observed this could be an issue.

There is no general answer for this question. Do pilots observe religious fasts during flying? Some do, as this article notes:

... although Islam gave permission or leeway to break fast if one found it tiring during the flight, most pilots and cabin crew still chose to fast.
“So, I fasted for 10 hours 50 minutes, compared to 13 hours 42 minutes in Kuala Lumpur and 11 hours 11 minutes in Melbourne. Much shorter time than fasting in Melbourne, isn’t that interesting?
“However, on June 29, 2016, I will be flying to Jeddah. Jeddah residents will be fasting for 14 hours, 54 minutes while KL residents will fast for 13 hours 43 minutes. I will probably have to fast for 17 hours! This is when I have to be really patient. I may break my fast once I have landed.
For the safety of passengers and to ensure a smooth flight, if both pilots are Muslims, they take turns to eat, he said.

However, there is no way to tell for certain how many aircrew observe religious fasting, as this pilot may be talking about that particular airline, for example.
As for Can they observe religious fasting, it depends on the regulation and company policies. Most of the civil aviation authorities don't have anything specifically related to religious fasting, preferring to cover them under fitness for duty, though there is atleast one case where the regulatory authority explicitly forbid fasting.

Indonesia’s Directorate General of Civil Aviation ruled that all safety-sensitive aviation personnel must eat while on duty during Ramadan, the Islamic month of fasting

The first thing that comes to my mind is the IMSAFE checklist; as a Private Pilot who practices intermittent fasting, I don't see why fasting would be an issue, as long as they can safely perform the tasks that they are required to complete, to the standards that the FAA expects.


Are there any examples of sustained human-powered flight above ground effect? Every video of human-powered flight has the plane or helicopter so close to the ground that it benefits from ground-effect. Is there any exception to this rule, i.e. a still-air-level-ground human powered altitude record that is high enough to leave ground effect?

The FAI's photo of Daedalus shows its height above the sea to be considerably more than its wingspan, putting it out of ground effect.
(Wikipedia says that most of the flight was 15 to 30 feet high, well within ground effect because the wingspan was 112 feet.)

I couldn't find any official FAI record for height achieved by a human-powered aircraft, though.

Yes, some of the prizes awarded to pioneering human-powered aircraft had terms stating specifically that the aircraft must rise above ground effect for some given time period.


Why is air accelerating over the wing surface? I know that there are dozens of questions about lift generation here but after reading them I still don't understand everything. My question is: why does air accelerate over the (upper side) wing? I know that it accelerates because there is pressure differential etc. but why wouldn't the air just flow over both sides of the wing with equal speed?

The Abdullah's answer is correct to it's level of approximation, but I'd like to expand on why the pressure is reduced on the leeward side.
As the air encounters the leading edge, it is pushed out of the way. Due to first law of motion, it would like to continue moving outward from the wing and avoid the area just above the wing. But besides inertia, air also has viscosity, which prevents sharp changes in air velocity, so the incoming air trying to pass high above the wing drags the air near the wing along. But when the air just above the wing is pulled out aft, there is shortage of air just over the wing, which means low pressure.
This low pressure causes the air bend around the wing, and since it pulls air from all sides, accelerate as it enters the low pressure region over the leading edge and decelerate again as it leaves it over the trailing edge.
Without viscosity (e.g. in liquid helium) the pressure would not be reduced, because the oncoming fluid would just continue straight over the highest point and the area over the receding part of the upper surface would be filled with stagnant fluid moving with the wing. In fact that's exactly what happens in stall – as the curvature increases (due to higher angle of attack), at some point the viscosity is no longer enough to keep the air moving, the area over the wing gets filled with air just whirling around and not moving away, so there is no longer shortage of air, the sucking of oncoming air stops and the generated lift rapidly decreases – just the lower surface still generates some.

From a layman’s point of view:
As far as lift generation, it is more precise to say that the lower static pressure generated perpendicular to the chord line of the wing is created by an increase in velocity of the air molecules instead of saying that the acceleration is created by the lower pressure. The acceleration of air molecules is greatest on the side (Upper or lower) of the wing with the greatest curvature. Basic aircraft wings are usually curved more on the upper-side of the wing than it is on the lower-side. This curvature creates a greater distance to travel in the same amount of time. Hence, the molecules are accelerated.
Think of it like a marching band or a column of soldiers marching. When soldiers or musicians have to march, they do so at the same speed. Both the cadence and the length of everyone’s steps are identical. When soldiers or musicians have to turn their column to march around an object, the individuals at the outside of the turn will move at a faster pace than the ones on the inside by lengthening their strides. If the turn is very sharp (like a 90° turn), the individuals on the inside of the turn will slow their pace by shortening the their strides. They do this because their is now a difference in the distance they have to travel in the same amount of time. Because there is a greater distance on the outside of the turn, there are fewer individuals per square feet of space on the outside of the turn than the amount of individuals on the inside. But since the column is not stopping, the file of individuals will continue to build up on the inside of the turn while waiting on the individuals on the outside of the turn to catch up. The column viewed from above will look like an accordion or a spring bent in the middle: a lot of material on the inside of the bend; very little material on the outside of the bend.
Let’s transfer this analogy to air molecules that are stationary relative to an airmass. The wing is actually moving through the airmass instead of the airmass moving over the wing. Either way, the side of the wing that makes the molecules move the furthest will temporarily have a lower static pressure and a higher velocity as the same mass of air on the other side of the wing. The lower static pressure creates a vacuum along the curved side of the wing. The molecules that were adjacent to one another at the wings leading edge, before encountering the wing, do not have to necessarily meet at the trailing edge. The average static pressure difference along the wing is enough to create this vacuum. The dynamic pressure of the air mass build up on the other side of the wing will also contribute to lift and increase with angle of attack.


Why are some LNAV/VNAV mins lower than the LPV mins for the same approach? Why are some LNAV/VNAV minimums lower than the LPV minimums for the same approach? See the RNAV (GPS) Rwy 5 approach at Scott Municipal (KSCX).

From what I could find out, it looks like they're unusual cases produced by the obstacle clearance calculations. There's a lengthy thread on PoA about it and the main points I saw are:

LNAV/VNAV and LPV approaches are designed differently (the specifications are in FAA Order 8260.58)
The Obstacle Clearance Surface (OCS; an imaginary zone that must be free of obstacles) is shaped differently for each approach type
The OCS isn't at a fixed angle: it depends on the designer's choice of glideslope angle (e.g. for terrain clearance) and - in the case of LNAV/VNAV - on the prevailing temperatures at the airport
The two approach types have decision points at different distances from the runway threshold, which also affects the glideslope requirements
The resulting OCS may be at a higher angle for LNAV/VNAV than for LPV

The FAA Order has a lot of formulae to work it all out, but apparently the result is that if the calculations come out in a certain way and there's an obstacle close to the runway, it can penetrate the LPV OCS but not the LNAV/VNAV OCS. That means the LPV DA then has to be made higher.

In the PoA thread, every example of an approach with LPV minimums above LNAV/VNAV has an obstacle close to the runway. But the consensus was that the LPV minimums being higher than LNAV/VNAV is still very unusual overall.

Finally, although this isn't exactly the same scenario, an old FAA article on GPS approaches mentioned that the minimums aren't always what you would expect:

  While [varying the obstacle clearance for an LNAV/VNAV approach] occasionally results in minima higher than the LNAV
  minima, the added safety benefit of a stabilized descent outweighs the
  difference in minimums

(That all refers to altitude, of course. The other part of the minimums is the visibility, but that should increase anyway as the DA and/or category increases. A high, fast aircraft needs to be able to see the runway from further away in order to descend safely.)

I saw an excellent answer here: http://www.askacfi.com/3854/lnav-lower-than-lnavvnav.htm
(when you look at the page look for 'LPV')
and as it looks to me it has to do with the width of the area evaluated for obstacles that is taken into consideration.


What is the typical touchdown vertical speed of a large airliner? What is the vertical speed (range) of a Boeing 787 (or any other large commercial aircraft) that should be achieved just before and during touchdown? I'm not interested in the vertical speed during the approach, my question only targets the last 100 feet before touchdown... this includes the vertical speed after the flare. Obviously a vertical speed of 0 fpm is desired for comfort reasons, but as I understand (see also this question), aiming for 0 fpm makes it difficult for pilots to aim at an optimal touchdown point on the runway.

From an MIT ICAT paper:

  Today's commercial autoland systems utilize the ILS (...) At around 30 ft above the ground, the aircraft enters the flare mode, during which the aircraft pitches up to reduce the vertical speed from its current descent rate to 1-3 ft/s by touchdown.

Which means we're looking at 60-180 FPM touchdown rate.

Kiss landings (near 0 FPM) are undesirable, because they can't be achieved on regular basis without risking long landings. They can also break landing gears (more on that below).

I checked various Boeing/Airbus operating manuals, they do not state the target rate of the flare mode, but from the 747-400 flight crew training manual (page 6.11):

  Do not allow the airplane to float: fly the airplane onto the runway.
  Do not extend the flare by increasing pitch attitude in an attempt to achieve a perfectly smooth touchdown.

Left: a shimmy event "damaged the wheel, tire, and shimmy damper" (Boeing). Right: what a shimmy looks like (YouTube).

  Landing with extremely low sink rates is more likely to experience shimmy than a firmer landing because the torsion links remain in an extended vertical position, where the damper has less mechanical advantage for longer periods of time (Boeing).

Boeing commercial aircraft are designed for 600 FPM landings, with 360 FPM when above the maximum landing weight. Boeing also says pilots are the best evaluators of hard landings, "because of the difficulty in interpreting recorded acceleration values at the CG of the airplane."

Based on pilot reports and data, exceeding 240 FPM is a hard landing, which further confirms the 60-180 FPM to be an ideal firm value whether the landing is flown manually, or with the auto-land (Boeing).

The closer to zero the better! Obviously there has to be something or you'll stay flying forever (run out of runway and have to go around) but the most comfortable for the plane and passengers is to touchdown at near zero vertical speed during the last few seconds of the flare.

EDIT: Based on user mins observation of you stating not wanting the VS on approach you can ignore the last paragraph but essentially during the flare you are going from approach VS of about 750 to a final touchdown of as close to 0fpm as possible.

As for the approach portion before the flare it can be figured out with some math based on the ground speed and the angle of the approach (typically 3 degrees on an ILS approach). I'm not going to go deep into the vector equations but there are some nice Rules of Thumb you can use to figure it out instead. For example multiplying the groundspeed* by 5. I think a 787 does about 150KIAS (Knots Indicated Airspeed*) on approach typically so that would work out to 750fpm.

[*] Of course depending on the headwind or lack thereof it will change the groundspeed and thus the rate needed to maintain the 3 degree (or whatever it is) on approach.


What is the difference between LNAV/VNAV and LPV minimums on an RNAV approach? This approach shows two sets of minimums that both have vertical guidance with a Decision Altitude (DA).  What is the difference between LNAV/VNAV and LPV, and why does LPV have lower minimums?

There's an FAA paper on RNAV approaches that explains the differences between LP, LPV, LNAV and LNAV/RNAV approaches. I made a table for my own reference but since StackExchange doesn't allow tables (AFAIK) here's a summary:

LP: no vertical guidance; WAAS required; MDA for minimums
LPV: vertical guidance; WAAS required; DA for minimums
LNAV: no vertical guidance; WAAS not required; MDA for minimums; requires RAIM integrity if WAAS is not available
LNAV/VNAV: vertical guidance; WAAS or baro-VNAV required; DA for minimums; requires RAIM integrity if WAAS is not available (i.e. if using baro-VNAV); possible temperature restrictions if using baro-VNAV

The difference between LPV and LNAV/VNAV is that although they both have vertical guidance, LPV was intentionally designed to be very similar to an ILS approach with an increasingly sensitive glideslope whereas LNAV/VNAV was not. Other answers have additional comments about LNAV/VNAV having been designed earlier and for different equipment which would certainly make sense.

Read below with a grain of salt, as I'm not a CFII.

From what I understand, there are no "precision" GPS approaches, aside from CAT1,2,3.

LPV is more accurate, uses WAAS, and means LP with vertical guidance.

LNAV/VNAV is an older tech, and was originally designed before WAAS was available. Before WAAS, aircraft with flight management/director systems were equipped to fly LNAV/VNAV. The VNAV portion consisted of Baro-VNAV equipment requirements. Nowadays, you can buy some newer aircraft equipped with Baro-VNAV, or fly those approaches with capable WAAS GPS.

Either way, you should read your aircraft manual and check it's equipment and what approaches it's qualified for.

Here's a link to more info I found.


Why do all commercial aircraft have carpets? When flying I noticed that all the commercial aircraft I have been on use carpets as a floor covering. But why? If you fly in an older aircraft it looks worn out and it is susceptible to stains etc. Why do they not use one of the hard flooring options like linoleum?

helps prevent slips and falls
contains spills (your spilt soda won't ruin your neighbors bag)
more easily removed and replaced
helps reduce cabin noise

Carpet is more pleasant

Aside from the practial reasons Greg already mentioned, most if not all people, will consider a carpet as a more pleasant material than ugly linolum. The fact that you have to replace a carpet after some years, counts also for most the interior in a plane (seats, board-entertainment, cover panels and so on). Furthermore a lot of people take their shoes of during long flights and a carpet feels in this situation a lot more comfortable.
In the good old days TWA rolled out a red carpet for their passengers at the check-in desk :)


What is the minimum separation between two A380's while taxing in-line? If you are tailing another A380 on the taxiway, how much separation do you need from your nose to the A380 that you are tailing?

For a Turbojet @ or < slow taxi power, the min distance behind is 30m

Thanks


What to look for when purchasing a headset I'm currently a student pilot, and I'm starting at an aviation university this fall to major in commercial aviation. Needless to say, I will be flying a lot. I'm looking to upgrade to a nice headset from the pretty basic one I have now, and I'm looking for a bit of guidance. I'm 6'3, so I wouldn't say I have a small head, and I've had problems in the past with headphones feeling cramped on my ears, which I don't want to be the case with my headset. I plan on having this headset for a while, at least all the way through college and hopefully several years after that.

First of all, is noice-cancelling actually that important(in terms of health and comfort)? I know there are a few decent headsets are out there w/o noice cancelling, and they are quite a bit cheaper than noice cancelling headsets.

I've been told about a couple commonly used expensive headsets that are pretty widely used across the industry. However, these headsets are $850+. At this price level, does the price of the headset accurately reflect quality, or is everything more personal preference? What are some of the pros and cons of the more popular headsets, and what should I look for when purchasing one?

I've had problems in the past with headphones feeling cramped on my
  ears, which I don't want to be the case with my headset

Do your best to test them out before you buy. Some pilot shops will let you put them on your head and if you are nice to the people that lurk around the airport they may lend you one for a flight to try out. I find that the Zulu's have bigger ear cups than the Bose but I don't have any hard numbers on size this is personal experience wearing them.

  First of all, is noice-cancelling actually that important(in terms of
  health and comfort)

Yes, just ask any one that flew in the pre-headset days. I personally find that I can comfortably fly for longer times with an ANR headset. Another thing to note is that the ANR head sets tend to not squeeze your head quite like the passive headsets I find this to be the real gain in comfort.

One of the big functional differences is that some of the LightSpeed headsets do not cary a TSO, I belive all of the Bose do. This may impact your ability to use them for commercial purposes in the future. You can find a discussion on it here.

When I got my pilot's license in 1978 my instructor said...

  "If you are going to fly for a living and want to look professional while you
  gas up,
  you should pay the exorbitant price for a pair of Ray Ban sunglasses, a
  David Clark headset, and Jeppesen charts.

  If you want to save \$1500, you can buy a pair of \$2 polarized
  sun glasses, a \$100 FlightCom headset, and use free Govt charts. They will work just as good!"

The one thing that made more difference in my comfort than anything else was using cloth ear protectors. They are more comfortable than any ear cushions I have tried, and allow a constant supply of cool fresh air to breath past your ears.

Cloth ear covers allow fresh air to breath past your ears and prevent sweating.

I have tested ANR and they make a huge difference in eliminating background noise. While they are worth the extra money if you have it, I have other things more important to me for $500 and have never purchased a pair.