Are both RVR and visibility minimum required for CAT I ILS? Is it required to have both RVR and visibility to be more than minimum for ILS CAT 1 or one of them is acceptable. If both required which one has priority.

If RVR (which is both runway-specific and more precise) is available, then it is controlling. If not then visibility (single value for the airfield) is controlling.
For example, typical Cat I minimums might be 1800 RVR or 1/2 Statute Mile (when the runway has an ALSF-II approach lighting system). If the RVR is near 1800 for one runway, the visibility may be low enough at the sensor for the airport that the prevailing visibility is reported as 1/4 SM -- too low to allow you to fly the approach (Part 121 rules, at least). But with the RVR, since it's measured at your runway (and often, right next to the touchdown zone of your runway), you're legal to fly the approach, since that much visibility "right here" means you have an excellent chance of seeing the approach lights at your DA.
Also, for all ILS approaches below Cat I mins (Special Cat I, Cat II, Cat III), only RVR matters.  The difference between each of those mins (1600 for Special Cat I, 1200 for Cat II, 600 for Cat III) are too fine to be captured by a "prevailing visibility" sensor.


How does British Airways permit a 23 kg bag in hand baggage? The carry-on baggage policy on British Airways states that:

  Maximum weight per bag is up to 23 kg (51lbs).

Two passengers, with bags near the weight limit could easily go well over 40 kg. And then there will be a few smaller laptop bags etc. inevitably stuffed into the overhead compartment, I imagine it can touch 50 kg.

However, the overhead compartments themselves have a stated limit of 32 kg. Isn't this an unsafe practice? If so, how is British Airways permitted to do so, and if not, why do other airlines not follow the same practice?

Easyjet has no firm weight limit and advertises this fact. From the website

  There’s no weight restriction for cabin baggage, as long as you can place and retrieve the cabin bag safely in the overhead lockers without assistance.

They also use vague language like “within reason” or “lift comfortably” but most people probably won't have 20 kg with them. Given the limited size of cabin luggage, you would need to deliberately carry dense, heavy stuff to reach that weight (books maybe? wine bottles and other liquids are off-limits and if you don't want to check in any bag you still need space for your other things).

And then, comes this (from the BA website you mentioned):

  Occasionally we may not have space to stow all hand baggage safely on board and you may be asked to check in some or all of your hand baggage at the boarding gate.

Bottom line: Airlines don't need to rely on a prespecified weight limit at all. They rely on the size restrictions and general common sense to keep things manageable and if it somehow does not work out, they can always gate check a few bags.


How do I distinguish 2 fixes with the same name? I see two fixes in the CIFP file that have the same name PERSN.

Given 2 fixes that have the same name but are located in different regions (defined by ICAO code) how does airplane/pilot distinguish between those 2 when respecting flight plan?
According to FAA Procedures for Handling Airspace Matters

  e. AIM [Aeronautical Information Management]  must  not  duplicate  any  radio  fix, waypoint,  marker  beacons or  compass  locators names.

how come that those fixes have the same name?

The answer is embedded within the question:  The pilot is able to distinguish between the two fixes because they are in different regions.


Boundary Markers of European Airspace As in previous question I am trying to transpose a geospatial data format from within a EUROCONTROL application into something I understand, like decimal lat-lon.

An answer to my previous question Reference Map of EUROCONTROL charging zones got me a long way forward. I now understand that the data references this map:

This is the result of plotting the data in the file directly onto the screen. In the case of EG (UK airspace) I've added little circles to show the coordinates.

What I now need to do is to take some of the points within my file and have the actual coordinates in lat-lon (or indeed any commonly used format).

It seems to me that the boundaries of the map might be set by waypoints (or perhaps vice versa). I grabbed this image from aeroresource.co.uk and annotated it to illustrate my theory.

My assumption

It looks to me like the boundary of north east boundary of EG matches with the line of waypoints indicated by the annotated green line. So the north boundary starts with RATSU to the east and GUNPA to the west.

The easternmost boundary runs from RATSU to the north to NIBOG to the south.

And finally, to my questions

Is that assumption correct? Is the boundary of the various airspace zones delimited by waypoints?

If yes - is there an authoritative source of that information?

If no - is there an authoritative source of whatever points are being used to draw the bounds of the airspace?

No, your assumption is not correct. Airspace boundaries are not defined by waypoints, but by WGS84 lat/lon pairs, which you can probably just use directly without a lot of manual work.

You need to consult the national Aeronautical Information Publication (AIP) for the country in question to get the coordinates for their national airspace, called a Flight Information Region (FIR). Specifically, look in AIP section ENR 2.1 (all AIPs worldwide are structed in the same way). Here is an example for the UK: https://www.aurora.nats.co.uk/htmlAIP/Publications/2020-03-26-AIRAC/html/eAIP/EG-ENR-2.1-en-GB.html#ENR-2.1

I recall having downloaded a global file with FIR coordinates for the entire world somewhere off the web, although I don't remember exactly where. It may well have been published by the ICAO. You might be able to locate it if you look around a bit.


What would cause an abrupt increase in engine noise after takeoff on the Boeing 737-800? I flew last week on a Boeing 737-800, I was in row 7, so just in-front of the wings.

I know from experience that there is a significant difference in engine noise from the front to the rear of the aircraft, up front you get more of the buzz, towards the back you get more "roar" engine exhaust noise.

However on this occasion the thing that struck me was an abrupt change in noise at about 1 minute from takeoff, not sure on altitude, but probably around 2000ft.

The takeoff (EMA) was 100% normal, straight climb no significant turn.

At this (estimated) 1 minute mark, the right-hand engine suddenly got louder, a harsher buzz, but seemingly no change in RPM (no pitch change). I would say inside the aircraft it almost doubled in volume.
There was no obvious added vibration to the airframe.

The flight went on as normal (4 hours to ACE Lanzarote) and the noise subsided as we reached cruise.

What could cause this?
A few things went through my mind: undercarriage retraction(?). Bird strike, blade damage, flame-out, resonance, internal changes in the engine such as guide vane angles, engine working loose!

The buzzsaw sound is usually the fan blades breaking the sound barrier.

Could be the elevation change, temperature, and humidity caused the sound to be more pronounced at that time, or perhaps the pilots increased the thrust on that engine due to cross winds or for some other reason.

Here's a youtube video with a similar noise:


How meaningful is the total number of flight hours? What hours count towards the total number of flight hours?

In a long haul flight, do all the hours of the flight count towards the total? Even if the pilot is resting?

Do 10 short flights of 1 hour (that is, 10 times take-off and 10 times landing) count the same as 1 flight of 10 hours (1 take-off, 1 landing)?

Is it possible that two pilots with 1,000 hour have a totally different real flight experience on their back?

As far as what hours are logged, there are a couple of different ways to do the counting.  On a light aircraft, time on the Hobbes meter is generally used, which equates to "engine running" time.  In the military, it's takeoff to landing, usually plus a small amount for taxi time (which may or may not account for all the time that the pilot is actually operating the aircraft).  In the airlines, it's "block to block" time, so pushing back from the gate until stopping at the gate.

As far as the time all being equal, it isn't.  Not even close.  2000 hours flown from Big Airport A to Big Airport B, 8 hours at a shot, means about 125 takeoffs, approaches, and landings flown, and an equal number monitored.  Almost all of those are radar vectors to an ILS approach -- very standard & predictable.  Five hundred hours as a pilot training instructor probably translates into about 500 landings performed, and many, many more supervised, with a great variety of approaches flown (visual, precision, non-precision, practice emergency patterns, etc)  The "hands on" time on the controls of a military fighter pilot in 500 hours logged is far greater than the hands on time during 2000 hour trans-Atlantic airline flying.

The problem is, "hours" is the currency that we have, and so that's how experience is measured.  Not because it's a great measure, but because anything more granular becomes very complicated and subjective.  Does my 1000 hours flying Lear jets count for more than your 1200 hours flying a King Air?  One's a jet, the other a turboprop.  Did one of us fly 3-hour legs mostly on autopilot on clear days, while the other flew 30 minutes at a time, much by hand, with lots of instrument approaches in bad weather?  Who flew with veteran copilots, and who flew with copilots brand new in the airplane?  Who flew to lots of unfamiliar destinations, and who flew the same canned route(s) day after day?  And how does any of that compare with 3000 hours in a C-5?  Or 800 hours in a crop duster?

All of this to say, that "hours is hours", while it overlooks a LOT of very relevant distinctions between some very diverse types of flying, is still the quick and easy comparison between pilots.  Not because it's wonderfully accurate, but because it's possible (we all log hours, after all), and the more detailed comparisons quickly become hard to objectively make.


Is the callout "minimums" on the 737 used to describe DH on precision approaches So, I have heard that decision height (DH) is used to signify the height on a precision approach which the pilot has to decide whether to continue or not.

But, in the 737, I only hear "approaching minimums" and "minimums". There is no "approaching decision height" and "decision height" callout. Is "minimums" used to describe DH too? Or is there something I'm missing?

DA/DH and MDA/MDH both get a callout of "minimums". The pilot is expected to know (from having briefed the approach earlier) which meaning applies. This is true for every FMS/GPS I've seen, not just the B737. On planes without this feature, one of the pilots will call out "minimums", and even a solo pilot (for smaller planes) should say the word to himself as a reminder.

While all pilots are required to understand English, it is best to assume their vocabulary is limited--especially during stressful situations or for urgent problems. Therefore, like ATC, planes use standard phrases--and as few of them as possible--to limit possible misunderstandings. If one general word can cover multiple situations, then that is preferred over having gratuitously different words for each one.


What happens if Marine One's rotor blades fail? While I was reading news, I came across this image of Marine One:

This is Sikorsky UH-60 Black Hawk

Citation of Image 1

Citation of Image 2

On a closer look, I see there are two big exhausts just under the blades at the top of Marine One. And there is also a big wing at the end of Marine One.

I know I would be wrong, but I am not sure about it: I thought these two things are inter-related to each other in case of rotor failure, i.e if the rotor fails then the exhaust would pump out air backwards like a blast giving it forward thrust, and the wing at the end would help it in direction or upward/downward thrust balance (just like in F1 racing cars). Essentially making it work like a plane for some time until it lands safely.

I tried searching about it, but could not get information about it. I did come across an older Marine One image whose exhaust is too small and is at the side rather than at the back and this does not have a wing at the back:

This is Sikorsky SH-3 Sea King

Citation of Image 3

Citation of Image 4

I have 3 questions:

Why is the exhaust at the back of new Marine One so big now?
Why is there a wing at the back of the new Marine One ?
What would happen if rotor blades of Marine One fail ?

Citations

No helicopter can fly if the blades fail.  The overwhelming majority of the lift produced, required to counter gravity, is from the blades. There is some lift from lots of other parts of the helicopter but all combined, nowhere near enough to keep it flying.  The blades are also required to manoeuvre the helicopter.

It is also most probable, and this what usually happens, that if one blade fails, or is lost, the resulting imbalance in the heavy, fast rotating rotor assembly leads to instant breakup of the aircraft.

The wing at the rear is called an horizontal stabiliser and its job is to push the tail up or down, depending on the load and speed of the helicopter, to keep the fuselage more or less level throughout the operating range of the craft.

Marine One would simply plummet if the blades failed.


Why do some airplanes fly at a very low speed (like this one) at a speed of 433 km/h (234 knots) at a whopping high altitude of 26,500 ft? Okay. So I'am just having a doubt on this flight (BA359) flying from Lyon, France en-route to London Heathrow. It is flying at a way low speed of 433 km/h (234 knots) in which i think is a bit weird. It is quite far from London Heathrow before landing. But come on, the head wind is not way too much. I mean if it is way too much, the airplane will fly at TAS 700 km/h ( GS 950 km/h) corrected for a 250 km/h head wind/jet stream.

Or maybe there is an altitude restriction or instruction to fly at holding speed to finally hold at Biggin or Ockham holding stacks due to heavy inboud traffic? I'am just curious.

433km/h seems really low, but keep in mind that flightradar is far from perfect. It is not uncommon that altitude, speed or position are far off, and sometimes, you see sudden jumps to more correct values when flight radar gets new data.

You can also check other sites like flightaware for particular fligt numbers, where you get a graph of altitude and speed, and can easily play back a given flight.

You didn't post a flight date, but the flights of the last few days have a speed of 600-700km/h at that position. This is below cruise speed, but the aircraft already start to reduce altitude and speed when leaving France.


Backup plane for checkride: Can it be a different model? I'm a student pursuing a US Private Pilot License, and recently scheduled my checkride. I've been training in a 1981 Piper Warrior (PA-28-161), but if its annual goes sour I may have to take my club's 1980 Piper Archer (PA-28-181). I have well over §61.109's 40 hours in the Warrior alone, and only ~10 hours in the Archer. I have a separate club checkout and CFI solo endorsement for each, they're pretty similar anyway—they're even both the same ATC type (P28A)—but they aren't the same model.
Here's the catch: Form 8710, the "Airman Certificate and/or Rating Application", asks specifically for

[II.A.2.] Total time in this make/model and/or approved FFS or FTD (Hrs.)

Furthermore, according to the IACRA FAQ ("I'm a Designated Examiner. I noticed a mistake when reviewing the IACRA application...."):

A mistake in the applicant's information cannot be corrected after it has been signed by the Recommending Instructor.

My prospective DPE explicitly told me that the backup plane was fine, and I can't find any Part 61 regulations that are specific to experience in one make/model aside from adding an experimental aircraft as part §61.63(h)(1), which is what I assume the box is really for. Of course I'd rather test in my more-experienced plane, but I'm asking specifically for regulations here if Plan A falls through.
Are there any regulations or headaches that I would encounter if I need to change the tail number or model number of my checkride plane and listed hours therein, potentially long after IACRA submission?

I came to the same conclusion as you, I don't see anything keeping you from going. You meet the requirements of 61.107 and 61.109, you have recent experience in both aircraft, and as far as make and model, they're both PA-28's. That's like going from a 172B to a 172S: it's the same make and model, Piper just makes it a little less obvious with their nickname and number combinations. If you had trained in a Warrior 160 and an Arrow, it would be a bit different, but only as far as requiring an additional endorsement.


What exactly are these frequency uses mentioned in the FAA's advisory circular on VHF use? The FAA's document AC 90-50, (currently AC 90-50D) sets forth how the aviation communications frequencies (118.000-136.975) are allocated in the United States.  Many of the assignment designations are plain enough, and common to the understanding of pilots, but some designations are outside normal use, for example:

Aviation Support
Domestic VHF
Flight Test Stations
Flight Inspection Use

Is there a document which provides descriptions of what these designations are and what qualifies as legitimate use of those frequencies?

The FCC is the ultimate authority on radio frequency usage in the US. 47 CFR § 87.5 has the definitions of the aviation services.

  Aviation support station. An aeronautical station used to coordinate aviation services with aircraft and to communicate with
  aircraft engaged in unique or specialized activities. (See subpart K)

Subpark K:

  § 87.319 Scope of service.

  Aviation support stations are used for the following types of
  operations:

  (a) Pilot training;
  (b) Coordination of soaring activities between gliders, tow aircraft
  and land stations;
  (c) Coordination of activities between free balloons or
  lighter-than-air aircraft and ground stations;
  (d) Coordination between aircraft and aviation service organizations
  located on an airport concerning the safe and efficient
  portal-to-portal transit of the aircraft, such as the types of fuel
  and ground services available; and
  (e) Promotion of safety of life and property.

Domestic VHF use is described in § 87.263. In general, these frequencies are used for communicating with aircraft, or between ground stations. There are various restrictions on certain frequencies/ranges, and despite the name, some are allowed for use on international routes.

Back to § 87.5:

  Flight test aircraft station. An aircraft station used in the testing
  of aircraft or their major components.

  Flight test land station. An aeronautical station used in the testing
  of aircraft or their major components.

Flight Inspection is not defined in § 87.5, so it may be the FAA setting these aside for their own use, but these frequencies are used by the FAA for ensuring "the integrity of instrument approaches and airway procedures."


Which organizations and individuals are invited for a review before the first flight of a new aircraft? The first flight of a new aircraft is a major aviation milestone for the company and the industry.  What departments or organizations (within a parent organization), and what individuals, are invited to the pre-flight review of a First Flight of a new aircraft?

What kind of stake holders are invited?
How many Technical guys are invited?
Is there any regulation by FAA to include a particular parties?

The level of contribution is your potential contribution to the particular flight test.

There are several levels:

Who gets a place in the aircraft? This should be test pilot(s) and maybe an engineer or two if the aircraft has enough space to carry them.
Who gets a place in the control room? This is the flight test engineer and systems engineers (experts for the engine, the control system, the landing gear and so on), also engineers familiar with the aerodynamics and flight mechanics of the plane. Generally, the number of people in the room should be kept small.
Who gets a place at the ceremony and press conference afterwards? Now only the test pilot is invited, and maybe the flight test engineer and the development project leader, but otherwise you will find mostly board members and PR people at the press conference. The engineers will be busy clearing the buffet at this time, anyway.

The responsibility to select who will get into the control room rests primarily with the flight test engineer and the test pilot. However, the whole aircraft development will already be observed by the FAA. From the FAA and Industry Guide to Aircraft Certification about the implementation of the planned flight test:

  During this Phase the Applicant and FAA work closely in managing, refining, and achieving their agreed PSCP to ensure that all agreed upon product specific certification requirements are met.

PSCP = Project Specific Certification Plan

Normally, FAA engineers are reviewing the planning, but do not get into the details such as who exactly will participate in the first flight. The company developing the aircraft prepares a plan and FAA will approve it without much hassle if the company has a record of conducting flight tests. If the company is a startup, however, closer scrutiny must be expected.


What is the relationship between the code of an Area Control Center (US) and associated Flight Information Region? From the wiki page, what I understand is

  an Area Control Center (ACC), also known as a Center (or in some cases, en-route, as opposed to TRACON control), is a facility responsible for controlling aircraft en route in a particular volume of airspace (a Flight Information Region). In the United States, such a Center is referred to as an Air Route Traffic Control Center (ARTCC).

My question: Is ARTCC code different from the ICAO-FIR code? Or are there anomalies?

For example, here's a NOTAM in the FAA site. AT the bottom, under the headline Other Information, the ARTCC code is given as ZDC. Can I safely assume that the ICAO-FIR code would be KZDC for that NOTAM?

KZDC is the FIR associated with the ZDC ARTCC.  Think of KZDC as the airspace itself (the flight information region), and ZDC as the facility which services it.


Why does rudder cause roll? In the few rudder incidents with the B737, rudder-freeze caused the airplane to roll. From what I know, the rudder causes yaw while the aileron causes roll. Why in the case of these accidents/incidents would the rudder cause a roll?

There are many higher-order effects. For example, yaw causes a slight increase in airspeed over the outer wing of the turn and a decrease in airspeed over the inner wing. As a result, the outer wing will generate more lift than the other, introducing a rolling motion.

Yaw also causes side-slip which triggers several effects. Wings that are swept backwards, as on the B737, contribute to the roll towards the direction of the turn, because the outer wing gets effectively longer (visual explanation) and produces more lift. Further contributing to this roll is the outer wing having a higher angle of attack due to the dihedral effect (visual explanation).

Similar effects apply to other control surfaces. It's not true that rudder only causes yaw and ailerons only cause roll. Those are simplifications, even though aircraft are usually designed for these simplifications to hold fairly well.

There is also a direct effect. The image below didn't show the center of mass; I drew in a guess as a yellow circle. It's clearly below the rudder, which is true for most aircraft. This means applying rudder introduces a rolling torque, roughly equal to the sideways component of the force on the control surface, multiplied by the distance between rudder and the longitudinal axis. The magnitude of this product is visualised as the area of the red rectangle.


Where to find NACA 65-110 Airfoil? I'm working on a research project regarding the Bell XS-1, which used the NACA 65-110 airfoil. I haven't been able to find any data on this airfoil, and I'm wondering if anyone knows where I could?

Google "NACA 65-110" and the first entry is airfoiltools.


What prevents Low Cost Carriers (LCCs) from cutting cost that compromise safety? I was reading an article about LCCs and here is an excerpt that got me thinking.

  While budget airlines cut other corners to keep fares low, they do not
  — actually cannot — compromise the safety of their passengers in the
  process.

What prevents low-cost carriers from cutting corners that might compromise the safety of their passengers?

There are two main factors.

The law

One, as other answers have mentioned, is the law. There are strict regulations that cover everything in aviation, from the way people speak to the training they must have and the specifications and audit trails of almost every piece of equipment they use.

Now it's true that people, especially unscrupulous ones who are keen to save money and might be willing to take a few risks in order to do that, don't always obey they law or follow regulations to the letter. And after all, there are laws against murder with much more significant penalties than for (for example) flying with a bit less fuel than the regulations say you should, and yet people persist in murdering.

The culture

However, the other factor is the culture. A low-cost airline exists in the culture of aviation, not independently, and the culture puts safety first.

Each person working for the airline will have trained and may have worked outside the airline, and will already have acquired attitudes and ways of thinking that prioritise safety and adherence to regulation.

Each person working for the airline will be working with and encountering aviation industry individuals from outside the airline, on a daily basis - if they didn't share similar attitudes and ways of thinking, they'd stand out a mile, and so would a corporate culture that similarly failed to embrace the industry's culture of safety.


Why does camouflage make some planes fly slower? Why does camouflage decrease some airplanes' speed? I have noticed that some planes fly slower with camouflage than without it. For example, when the RAF applied camo on the P-51 Mustang, they noticed that it was 8 mph (About 12.87 km) slower than without it. This is why the Mustang usually had no camouflage on. My question is why did the camouflage make it go slower? Did/does this apply to other planes too?

Same reason gliders keep their wings waxed.  It wasn't the camo per se, it was the dull matte field-applied paint finish that included all sorts of imperfections, and to a small degree, the weight of the paint vs natural finish.  At a microscopic level, the surface of the matte finish was much rougher than a gloss or unpainted metal surface.  The microscopically rougher surface would have a stronger ability to inhibit air molecules flowing right against the surface (skin friction).  Add to that the surface imperfections introduced by the typical wartime spray-and-get-it-out-the-door process, vs smooth bare aluminum.

Think of the inhibiting effect on wind velocity close to the ground of a forested area vs a grassy plain, and shrink it down to the micro level.  The effect is most pronounced where the flow is relatively smooth, or laminar against the surface, which is most areas there the cross section is getting fatter (leading edges of wings and control surfaces, the nose, etc).

The Mustang would suffer a bit more than others from this with flat paint because of its (somewhat) laminar wing that had a maximum thickness well aft, which means it would have more surface area that is sensitive to skin friction, than a non-laminar wing aircraft like a Spitfire or Typhoon.  So if the Mustang was penalized 5kt with flat paint, a Spitfire might have only been penalized 3kt because it had less surface area that was (relatively) laminar in the first place.


Why are no recent small aircraft designed to be "characteristically incapable of spinning" as the Ercoupe was? I'm a student pilot at a flight school that primarily flies RV-12s as a trainer. We had one day that through a booking error meant that all the RV-12s were booked so we had to use their Ercoupe 415-C instead.

I was surprised at how easy the plane was to fly and asked my CFI about the "characteristically incapable of spinning" placard on the front panel. He explained that the rudder pedals weren't necessary because the plane maintains coordinated flight by connecting the ailerons to the rear rudder.

I think this is an amazing innovation for the Ercoupe and I'm surprised it's not a design that I can find on any modern small aircraft designs.

Maintaining coordinated flight with rudder pedals isn't a complicated task for a trained pilot but it is another task that the pilot needs to perform. It seems like removing flight tasks from the pilot would make for a safer aircraft so why do manufacturers not include designs similar to Ercoupe's models?

Is it a weight/cost/drag issue, or are spins not as huge of a killer as they were in the 40s-60s?

The coupling between the ailerons and rudder are designed such that they avoid uncoordinated turns as you described.  However, this occurred at the expense of control in other flight conditions.

In fact, there are situations where you need to deflect the rudder without roll input, you need to deflect the rudder more than the preset coupling, or in a manner that is opposite to the preset configuration.

For example, if you turn right, the system will add right rudder to keep the airplane coordinated. But if you want to do a forward slip, you may perform a left hand roll, but with rudder all the way to the right. The system would be incapable of performing this maneuver, meaning you can't fly in high winds with the system installed. This is fine if you live in an imaginary place where the winds are always favourable.

As a result, a common modification on the Ercoupe is to disconnect the coupling between the rudder and ailerons...

Edit: I also wanted to add that spins are recoverable, within reason, by a trained pilot. For some planes, you are simply forbidden to intentionally enter a spin as a remedy to its inability to recover from a spin!


How much torque can a Boeing 747 apply when pitching? I know this is a weird way of thinking about / quantifying this, but I'm trying to figure out how much torque a 747 can apply to itself when it pitches upwards (turning about an axis from wing to wing, with the nose moving upwards). I figure it's equal to the lift times the distance between where lift is applied to the wings and the axis of rotation, but I haven't been able to find this data.

The pitching force is coming from the horizontal tail's downforce resisting the airplane's net nose down pitching forces, so the real question is how much downforce is being applied and how far away is the tail's downforce from the lifting forces holding the plane up.

For a given set of parameters, you need to know the All Up Weight, the Center of Gravity location, and the Neutral Point, which is the location of the (gaseous) fulcrum the tail has to work about.  The NP is defined as the longitudinal point at which pitching moments are zero, the "effective" balance point in other words, taking into account the center of lift plus/minus the effects of various pitching moments (airfoil pitching moment, fuselage lift, nacelle lift, thrust effects, flaps and gear hanging down, etc.) which result in the actual net downforce the horizontal tail has to produce to "hold the nose up" in a given steady state flight condition.

If you know the CG location and the all up weight, then the "torque" acting on the fuselage at the Neutral Point is simply all up weight times the distance between the CG and NP.

So if the plane weighed 700,000 lbs, and the CG was 20 feet forward of the NP (just a wild guess; I have no idea the actual number), the "torque" value, the nose-down pitching force acting at the NP, is 14 million foot pounds.  If the aerodynamic center of the tail was 120 ft aft of the NP (another wild guess), that works out to 116666 lbs of downforce required for stable level flight back at the tail.  Of course if you now pull pitch to raise the nose, you are accelerating the mass about the lateral axis now, so those forces go up temporarily.

The values will change with changes in configuration, weight, speed, etc.  Make a change that moves the Neutral Point forward, like adding thrust, and the torque value and downforce required goes down; airplane pitches up from the thrust application because the existing tail downforce is excessive. Drop the gear, which moves the Neutral Point aft, and the torque value and downforce required to counter it goes up; airplane pitches down from the drag of the gear because the existing tail downforce is insufficient.

As far as finding out what is a typical Neutral Point on a 747, good luck with that...


What is this aircraft and the Air Force it belongs to? Hi,
Could someone identify the fighter jet type and the Air Force it operates in? Thanks

Panavia Tornado, Royal Air Force (UK), 13 Squadron.

The aircraft in the question is identified as belonging to No. 13 Squadron by the distinctive green, yellow and black 'Squadron flash' painted on the aircraft side  below the front part of the cockpit.

Royal Air Force roundel

13 Squadron flash

Above: a Tornado of No. 13 Squadron as seen at the 2007 CIAF air show in the Czech Republic. The squadron flew Tornado GR.1A aircraft from 1990, and later the GR.4 and GR.4A variants.

Here is ZA401 (a GR.4) at RAF Leuchars in 2005 with the 13 Sqn flash painted on the tail as well as the normal place, as part of the Squadron's 90th anniversary celebrations:

No. 13 Squadron RAF (Wikipedia)


Under what conditions does the FWC give the PITCH PITCH aural call-out on the A320? I wanted to find more detailed information about the PITCH PITCH aural call-out that the FWC gives out on the A320. However it is not listed in the FCOM. It would help alot to understand about this feature.

It would be really helpful for an official reference also.

The "PITCH, PITCH" synthetic voice is called out when

  "The aircraft pitch attitude is becoming excessive during flare an
  landing."

This is an optional feature which airlines can install to avoid tail strike.

Source: ECAM Description, Indicating/Recording Systems, Aircraft Systems, A320 FCOM


Is a 61.31 solo endorsement a one-time thing, or does it need to be repeated? The FAR 61.31(d)(2) reads that a person can act as pilot in command if they:

  Have received training required by this part that is appropriate to
  the pilot certification level, aircraft category, class, and type
  rating (if a class or type rating is required) for the aircraft to be
  flown, and have received an endorsement for solo flight in that
  aircraft from an authorized instructor.

Is this endorsement a one-time thing, or does it need to be "renewed"? I met an glider instructor who claimed that my glider solo endorsement is no longer valid because my power license lapsed.

You didn't say which certificates and ratings you hold, but since you mention 61.31 I assume you're already a certificated pilot in a non-glider category/class (ASEL?) and you're receiving glider training.

The short answer is that a 61.31 solo endorsement expires only if the instructor added an expiration date as a limitation. Including an expiration date is optional, not required; see the Bennett interpretation:

  The regulations of 14 C.F.R., however, do not prohibit an instructor
  from placing limitations, including an expiration date, in a §
  61.31(d) solo endorsement. See 14 CFR § 61.195(d) (prescribing flight instructor limitations on endorsements).

AC 61-65 is the reference for endorsements, and it has this language for a 61.31 solo endorsement (note the "optional" limitations section at the end):

  A.71 To act as pilot in command of an aircraft in solo operations when the pilot does not hold an appropriate category/class rating: §
  61.31(d)(2).

  I certify that [First name, MI, Last name] has received the training
  as required by § 61.31(d)(2) to serve as a pilot in command in a
  [specific category and class of aircraft]. I have determined that [he
  or she] is prepared to solo that [M/M] aircraft. Limitations:
  [optional].

Therefore, whether your 61.31 solo endorsement expires or not is determined by the wording of the endorsement itself. But as always, even if your endorsement is valid from the FAA's point of view, the glider school/club and their insurance company may have their own, additional requirements before letting you solo.

I don't understand the second part of your question: "my glider solo endorsement is no longer valid because my power license lapsed". FAA certificates never expire so I have no idea what you mean by "lapsed" (maybe this scenario?). In any case, I suspect that it might be better to ask that as another question; if you do, please tell us exactly which certificates and ratings you have.


Why is the top left corner cut off on the cg location envelope for small airplanes? Why does the PA-28 C.G. envelope have the top left corner cut off rather than allowing higher weights at a forward C.G. like it does at the aft C.G.?

(source)

With "top left corner" you mean the combination of a heavy airplane and a forward cg location.

This is to limit maximum stick forces. Manoeuvring (= flight at a specified load factor ≠ 1)  needs force proportional to the distance between the cg and the neutral point ("static margin") and the mass of the airplane. There are several situations in which certification requires not to exceed specific maximum forces. For example, FAR Part 23.145 says:

  (b) Unless otherwise required, it must be possible to carry out the
  following maneuvers without requiring the application of single-handed
  control forces exceeding those specified in §23.143(c). The trimming
  controls must not be adjusted during the maneuvers:

[...]

  (c) At speeds above VMO/MMO, and up to the maximum speed shown under
  §23.251, a maneuvering capability of 1.5 g must be demonstrated to
  provide a margin to recover from upset or inadvertent speed increase.

Another would be out of trim situations as those in Part 23.255:

  (f) In the out-of-trim condition specified in paragraph (a) of this
  section, it must be possible from an overspeed condition at VDF/MDF to
  produce at least 1.5 g for recovery by applying not more than 125
  pounds of longitudinal control force using either the primary
  longitudinal control alone or the primary longitudinal control and the
  longitudinal trim system.


Can a CIWS engage aerial targets? Can a Phalanx-type Close-In Weapons System (CIWS) engage small aerial targets like drones, UAVs, rotorcraft? Is there any case that Phalanx was used against aerial targets?

Considering that these systems are tested against drones, then the answer is yes. The limitations on what is too small to engage for any particular system are likely classified.


Where is the airspace not covered by primary Radar? Most ATC in the world rely primarily on secondary radar to know where planes are. This requires that the transponder on the plane works correctly.

This means that maintenance and deployment of primary radar is no longer a primary concern for airspace regulation. It becomes at best a secondary backup system before they need to pull out the flight progress strips and airways charts.

Where are the spots that is not covered by primary radar? I understand that some military ships have primary radar and can act as a mobile radar during operations.

There are a few spots not covered by primary radar. Here are a few I can think off:

Afghanistan, not really what you'd expect from flying between Europe and South East Asia. I was told though by the pilots that the Americans were keeping an eye on us. I'd imagine there are a few holes in the CIS countries as well.

Multiple areas in Africa, but this is improving I believe. There's a post on PPrune. Apparently known as the 'dark continent' for spotty coverage and consistency. South Africa has good coverage, and I'd guess the same for much of northern Africa as well.

A few remote areas in South America, then again, improving.

Oceans are not covered.

Determining factors are population density, aircraft density and economic development.

As more you Malaysia map, if there's a radar at Kota Bharu [KBR] airport, here's the map assuming a range of 200 Nm for the radar. It should in theory be well within reach.

(source: gcmap.com)
And an extended version:
SGN Ho Chi Minh City (Saigon) [Tan Son Nhat Intl], VN
KUA Kuantan [Sultan Abmad Shah Airport (Pedang Geroda Airport)], Pahang, MY
KUL Kuala Lumpur (Sepang) [Intl], Selangor, MY
KBR     Kota Bharu [Sultan Ismail Petra], Kelantan, MY

(source: gcmap.com)
Just for the interested, here's a map showing Japanese military radar, just to get an idea of coverage in a country full of people and planes.

Maps from http://www.gcmap.com/


How well does a composite fuselage deal with lightning? The metal fuselage of an aircraft, being highly conductive, protects occupants, interior components and fuel from the effects of lightning by conducting the electricity around them.

Some newer aircraft, such as B787 have a fuselage made entirely out of composite materials. The major portion of the 787 is made from carbon fiber plastic laminate.[1]  Although carbon fiber conducts electricity it has a higher electrical resistance.[2][3] Higher resistance means more heat generated by the material. And carbon fiber makes up only a percentage of the composite.

Has the composite material been found to have enough conductivity to deal with a direct lightning strike without damage to either the material itself or the contents of the plane? Or do designers deal with lightning strikes in some other way?

[1] Boeing 787 Systems Manual.

[2] Department of Physics
University of Illinois at Urbana-Champaign website

[3] Electrical and mechanical properties of electrically conductive polyethersulfone composites. Lin Li and D.D.L. Chung, 1991, State University of New York at Buffalo. [.pdf]

Lightning striking modern aircraft with composite structures

  Composite parts that are in lightning-strike prone areas must have appropriate lightning protection. [...] Composite structures are less conductive than metal, causing higher voltages.
  Lightning protection on airplanes may include wire bundle shields, ground straps, composite structure expanded foils, wire mesh, aluminum flame spray coating, embedded metallic wire, metallic picture frames, diverter strips, metallic foil liners, coated glass fabric, and bonded aluminum foil.
  Lightning can also damage composite airplane structures if protection finish is not applied, properly designed, or adequate. This damage is often in the form of burnt paint, damaged fiber, and composite layer removal.

  Source: "Lightning Strikes: Protection, Inspection, and Repair", Boeing, 2012

New technology improving the lightning protection of modern aircraft

  Traditional methods to protect composite aircraft from lightning strike damage rely on a conductive layer embedded on or within the surface of the aircraft composite skin. This method is effective at preventing major direct effect damage and minimizes indirect effects to aircraft systems from lightning strike attachment, but provides no additional benefit for the added parasitic weight from the conductive layer. [...]
  A new multi-functional lightning strike protection (LSP) method has been developed to provide aircraft lightning strike protection, damage detection and diagnosis for composite aircraft surfaces.
  The method incorporates a SansEC sensor array on the aircraft exterior surfaces forming a "Smart skin" surface for aircraft lightning zones certified to withstand strikes up to 100kA peak current. SansEC sensors are open-circuit devices comprised of conductive trace spiral patterns sans (without) electrical connections. The SansEC sensor is an electromagnetic resonator having specific resonant parameters (frequency, amplitude, bandwidth & phase) which when electromagnetically coupled with a composite substrate will indicate the electrical impedance of the composite through a change in its resonant response. Any measureable shift in the resonant characteristics can be an indication of damage to the composite caused by a lightning strike or from other means. The SansEC sensor method is intended to diagnose damage for both in-situ health monitoring or ground inspections. [...]
  The SansEC sensor smart skin technology provides lightning strike protection, shielding effectiveness, and opportunity to achieve in-situ damage detection and diagnostics for aerospace composite structures along with other potential beneficial functions not available from the standard LSP method.

  Source: Szatkowski, G. N. at al.: "Open Circuit Resonant (SansEC) Sensor Technology for Lightning Mitigation and Damage Detection and Diagnosis for Composite Aircraft Applications", NASA, 2014 - Download Link

Further information can be found on the internet, see for example "Playing with Lightning in the Name of Aircraft Safety", NASA.

See also this similar question.


What are the points 1864 and 1922 on this in-flight map? This was taken in a Emirates flight Dubai-Paris in December 2015.

What are on these 2 locations?
Why these numbers? Are they dates?

The number may stands for the year of the ships sunk.

1864 may correspond to CSS Alabama (Arabic: ألاباما), a Confederate States Navy Screw sloop which was sunk on June 1864 at the Battle of Cherbourg. The wreck is at 49°45′9″N, 1°41′42″W.

1922 may correspond to SS Egypt (Arabic: مصر), a British ocean liner which was sunk after a collision with SS Seine on 20 May 1922. The wreck is located near 48°10′N, 5°29′W.

As @mins mention in comment, there are other wrecks appearing on the map in IFE, including Mary Rose 1545 near Portsmouth and San Pedro de Alcantara 1786 near Peniche.


How does a small aircraft like a Cessna fly at night? What happens when a small aircraft like Cessna is flying in daytime then night hits and its now pitch black with zero visibility? How does he not run into mountains and the like?

Lets attack this from a few different angles.

  then night hits and its now pitch black with zero visibility?

There is plenty of visibility at night, a clear night is just as nice as a clear day. As a matter of fact when the air cools at night and clouds roll out you can some times see farther than you can during the day.

Here's me on a VFR approach (Piper Warrior) in to KLNS at about 10pm one night, you can see the runways are lit up nicely and can usually be spotted from 5 - 10 miles out depending on altitude.

Here is us earlier that night heading away from KABE (those lights are Allentown PA)

(photo credit to my girlfriend who was bravely sitting in the back)

As you can see you can still make out the horizon and plently of land marks. While it may be different during the day you can still fly VFR at night.

  zero visibility?

Zero visibility during the day is the same as zero visibility at night and as mentioned in the comments will require you to fly IFR if you want to fly.,

  How does he not run into mountains and the like?

Not flying into the side of a mountain is a topic of its own. You should check out my answer here to that very question.

From a more general stand point there are lots of ways to navigate in an aircraft. Here is a solid answer that covers most of them. The only thing that is not really feasible in a small single pilot aircraft if you are solo is celestial navigation although it could be done.


What materials are used to make up a combustion chamber? What type of materials are used to make up the different sections such as the linings of the combustion chambers in a gas turbine engine. Do these type of materials vary for the different types of gas turbine Engines such as the multiple-can type, annular and cannular.

If you are asking about combustor liners specifically (as opposed to the hot section in general), the ones I am familiar with are cobalt-based superalloys.


What would happen if an aircraft were to touch down on EMAS? What would happen if a jet (say, a A330) were to touch down on the Engineered Materials Arrestor System (EMAS) just before the runway, instead of on it?

According to the FAA the EMAS is designed to "reliably and predictably crush under the weight of an aircraft". Will an aircraft touching down with its main landing gear crush and sink through this material as it would if it hit the EMAS after trying to stop on the runway or will the plane's momentum carry it on to the main part of the runway unharmed?

will the plane's momentum carry it on to the main part of the runway unharmed?

An aircraft landing on the EMAS must not suffer control problems.

According to an EMASMAX document

  FAA Advisory Circular (AC) 150/5220-22A
  ...

  No adverse aircraft affects in the event of short landing
  ...

The referenced document doesn't state this but does say that EMAS should be set back from the runway end and

  must not cause control  problems  for  aircraft  undershoots  which  touch
  down    in    the    EMAS    bed.

According to RUNWAY SAFETY AREA PROJECT - IGOR I. SIKORSKY MEMORIAL AIRPORT,
there is only a three inch reveal at the transition of EMAS bed to runway. So a landing gear transitioning this part this part would likely not be catastrophic. I imagine crushed EMAS material still has some thickness.


Is an aeroplane's design only functional? Many parts of a car are not obligatory. They are attached or formed to make the car look better.

Are aeroplanes(especially airliners) only designed for function or are there any parts that are purely for aestethical reasons (On the outside of course)?

The question is very broad so I gave a quick overview, please comment and I will elaborate further by editing my answer.
Jet liners are purely designed for function, they are all about transporting x amount of passengers for the lowest cost per mile. That trend started after the oil crisis. The Boeing 747 was originally developed as a cargo airplane such that when we would by flying supersonic they could be converted from pax to cargo. This all went south and supersonic flying was not the future anymore. The 777 program was one of the first jet fully optimized to fit as many pax in it as possible, just look at two seat plans, one for the 747 and one for the 777

Boeing 747

Boeing 777

As can be clearly seen by the picture above is that the 777 has far less space left with no seats thus fitting in more pax per square meter.

In the private jet world design is still functional but there is more freedom to waste some fuel on unnecessary bits if this makes your aircraft stand out. This would result in aircraft like the:
Beachcraft Starship

Piaggio Avanti

They both feature a more complex design involving a Canard configuration which has advantages but also major drawbacks

Moving over to private jets a similar trend as in the civilian market can be seen where designs are more alike due to the simple fact that jets are expensive and you will most probably only see the inside as it is parked in a hangar anyways and you can't drive it over the boulevard so everyone can see it

Honda Jet, interesting looking aircraft but still mostly functional as mounting the engines aft reduces the noise inside the cabin, high mounted engines allows for unpaved runways and reduces the risk of FOD from the runway.


On the Ka-50 coaxial helicopter, why does the bottom rotor flap up on the right side instead of in front during forward flight? In the game DCS World flying the Ka-50, when flying forward at high speeds, the bottom rotor will flap up on the right side of the helicopter (also note that the top rotor is flapping up on the left, though not as much):

But according to this diagram:

while the maximum up-flap velocity is on the right side, the actual max up-flap displacement is in front of the aircraft. Thus, shouldn't the bottom rotor be flapping up in front of the helicopter, instead of on the right? This effect only occurs at high speeds, at lower speeds it's either not there or barely perceptible:

Is this up-flap behavior correct, and if so, what is causing it?

This is does appears to be partially correct behavior for a Ka-50 in forward flight (in the low speed example)--but not because of gyroscopic procession.  It also may be plagued with transient artifacts from the DCS flight mechanics model.
According to DCS, the Ka-50 rotor is modeling using blade-element momentum theory with some inflow model, so the basics of its aerodynamics should be correct.  That said, this shouldn't account for blade/vortex/body interactions or other higher order effects.  Based on the same source, DCS implies that they use a rigid-blade model (that is, a rigid blade rotating on flap/lag hinges) for their rotor blades, which allows them to model blade motion and couple their aerodynamic model with some rotor dynamics.  This is impressive for a sim to have, but remember that they are missing significant interactions between rotors, let alone the body.  They can reproduce the performance from certain phenomena in flight, but they don't go into detail of what else goes into their model, so I cannot comment any further.  However, I can say the following.
Gyroscopic precession does exist, this is true, but it is a much simplified explanation of why helicopter rotor blades exhibit a phase lag that delays a blade's physical response to an applied load.  Rotor blades are not gyroscopes, and, in fact, the phase lag for rotor blades is not always 90$^\circ$ but varies depending on the design of the rotor system.  As for why the FAA and other pilot-oriented groups continue to teach that gyroscopic precession is the reason why it occurs: I have no authoritative answer, but, as with how the FAA incorrectly teaches about lift, teaching the "actual" reason why an aircraft does what it does will not necessarily teach you how to fly the aircraft better (unless you have an extremely well-developed understanding of fluid mechanics).  Getting the explanation "good enough" (so that you have a useful hermeneutic for how the vehicle interacts with the air is sufficient to enable you to use the aircraft safely) seems to be the mantra--which makes some sense.  Else, no one* would be allowed to fly!
Regardless, to the point.  Let's talk about phase lag, how to control a helicopter using a rotor, and how those two come together.
Phase Lag and Helicopter Controls
Phase lag refers to the difference in when a force is applied to a dynamic system in resonance and when its physical effect manifests itself.  This gets a little complicated in a helicopter's rotor system since, in order to control the vehicle, the rotor itself has to be tilted in the desired direction of motion.  Keep in mind that the rotor (I speak in the singular, but I'll apply this to the Ka-50 in a minute) is the primary source of propulsion for the helicopter, so, to move anywhere, the rotor has to be pointed in the direction of motion, as illustrated below.  The purple line is the plane connecting the tips of the rotor blades (or the tip path plane) during hovering flight, and the orange line is the tip path plane in forward flight.

You can also see this in this video of a hovering UH-60 Blackhawk (note the level tip path plane) as compared to this video of a Blackhawk in forward flight (note the tip path plane tilted in the direction of motion--more evident during the first half of the video).  A caveat, though: the rotor on the Blackhawk is actually set at a small angle forward to decrease parasitic drag and decrease the body pitch angle in forward flight.  This is particularly evident in the first video, wherein the helicopter is actually pitched upward when the rotor tip path plane is horizontal.  I'm using the UH-60 as an example, but this is a fairly common practice.
In short, you have a single force vector, and you have to point that force vector in the direction you want to push the helicopter.
DISCLAIMER: if you don't want to learn about phase lag and just want the answer, skip to the last section now.  A digression on phase lag is ahead.
Hence, whether the rotor is articulated or some form of rigid, it is designed such that the blades can flap as needed.  The Ka-50 rotor does have flapping hinges, as you can see in the image below from how the blade is slightly angled relative to the blade grip extending from the rotor hub.

So where does this leave us?  I'll explain phase lag in a minute, but the confluence of phase lag and blade flapping is important to grasp first.  For instance, if I put in a control input to a rotor to make the vehicle move to the left, I would expect the rotor disc to tilt to the left by way of the blades flapping up on the right side of the helicopter and down on the left side.  However, since the physical response and the aerodynamic loads are out of phase, I have to put in the control input prior to when I want the effect to manifest.  If this effect was gyroscopic, I would have to pitch the blades as they passed over my tail or nose (90$^\circ$ prior to the flapping effects I want to see).  However, if we look at a Robinson R-22, it ends up being more like 72$^\circ$ prior instead of 90$^\circ$.  And it's not the only one (though typical values for articulated rotors do end up being closer to 90$^\circ$, if memory serves)!  However, this is because the effect is not due to gyroscopic precession, but is a result of rotor design.
A flapping rotor system is the product of the a variety of forces, including mechanical damping (think of a dashpot, although that particular item is not necessarily the case), stiffness (think of a spring), aerodynamic damping (resistance to motion proportional due to changing aerodynamic forces), aerodynamic forcing (think lift, or what's causing the flapping in the first place), centrifugal or inertial forces (what's trying to keep the blade level), and "coriolis" forces, to name a few.  These interact with a rotor blade that is hinged with some amount of offset from the center of rotor as well, which we can see on the picture of the Ka-50 rotor hub, which also changes how the blade responds to aerodynamic forces.  As a result, we can tune the rotor system we design to respond in a particular way to aerodynamic forcing.  However, it changes the phase lag of the system.
Visualizing the Effect
One way to visualize this (if you like math -- if not, I'll provide a physical example too) is using an Argand diagram, which can be used to show components of a spring/mass/damper system (a rotor system is an example).  This would come from the Fourier transform of an equation having the following form, where $I$ is inertia, $b$ is the damping coefficient (higher the coefficient's magnitude, the more resistance to motion there is), $k$ is the stiffness of the flapping hinge (the "restorative" force in the diagram), $\beta$ is the flapping angle, $\dot{\beta}$ is the flapping velocity, and $\ddot{\beta}$ is the flapping acceleration.  $F(\Psi)$ is the aerodynamic forces that create the blade flapping motion.
$I\ddot{\beta}+b\dot{\beta}+k\beta=F(\Psi)$
For example, the diagram below shows a system where the spring (rotor system: the restoring force which is dependent on actual flap angle) is dominant, making the system's physical response pace closely with the input force.  Conceptually, that makes sense -- if I have a stiff spring, the amount of force I use to compress the spring will match very closely with the spring's compression (in the absence of a damper or much inertia).  I can get that from the Argand diagram from doing vector addition with the 3 components I have plotted.  If I did so, the resultant vector would lie very close to the "restorative" axis, or to the right side of the horizontal axis.

However, what if the damping is much larger and closer in magnitude to the restorative vector?  This more usual for a helicopter with articulated rotor blades.  If so, we get an Argand diagram that looks more like this:

If I do my vector addition here, I see that the resultant vector, and thus the physical manifestation of my input force, is $90^\circ$ out of phase with my input.  A physical analogy would be if I connected a spring to a pneumatic cylinder and then tried to, alternately, compress and extend it.  The amount of force I apply is no longer directly proportional to the compression or extension of the spring, but is out of phase with the spring's physical motion due to the presence of the damper.  If I had a spring with a lot of mass, you could see how that would further complicate the problem.
Putting it all together: what does this mean for the Ka-50?
Right: so, in the pictures provided (copied below), you show the Ka-50 rotor flapping by small amounts during lower speed forward flight (quoted IAS was 60 kph).

Note that both rotor discs are flapping up as they pass over the tail.  As said, in order to maintain speed, the Ka-50's rotors need to be tilted in the direction of motion, though this should only be a transient feature as the vehicle pitches into the direction of motion.  If they were not, parasitic drag (and other sources) would slow the vehicle down.  To maintain speed, a force has to be continually applied in the direction of motion.  Hence, the aerodynamic forces are applied earlier in the rotation to induce both rotors to flap up as the pass over the tail of the aircraft.  The 60 kph case is also useful because flapping due to advancing/retreating blade effects are relatively small as compared to the second case, shown below.

In this case, the rotors are obviously tilted left and right, respectively: which is strange.  Judging from the horizon lines in both pictures, it would appear that the helicopter is pitched down more in this higher speed case as well, which makes sense, since the blade flapping angle over the tail seems to be relatively small.  The vehicle also seems to be in a shallow right bank.
As a result, and I'll be perfectly honest, I'm not entirely sure why the rotors are tilted in opposite directions, and this is where I doubt the veracity of their model.  Due to the high speed, which should be leading to some interesting aerodynamics, I'm placing a bet on their modeling starting to break down.  If they are using an inflow model that approximates wake motion, some of the assumptions of that model may be breaking down at this high of an advance ratio, leading to unexpected blade motion.  An Jan Hudec says in the comments, both rotor planes should be parallel to each other.
*If I may perpetuate the legend: no one, that is, except Peter Kämpf.


Pressure distribution on Aircraft wing While conducting a structural analysis FEA for an aircraft wing, I had to import the CFD pressures acting on the wing, lets say at an A.o.A = 10 deg, at 80 m/s and at  sea level, and say the atmospheric pressure is 1 atm. Should the imported pressures from CFD analysis (on the top surface and bottom surface of the wing) be the absolute static pressures or the net pressures? (Assuming the wing surfaces have no slip condition).
If I use the absolute pressures, then the top surface would be experiencing a positive pressure meaning that the pressure is acting onto the top surface (causing it to shrink), and if I use net pressure then that would be negative meaning that the pressure is acting out of the top surface (causing it to expand).
Which one is true? I think that absolute pressures should be used because if, for example, we want to know the structural behavior of the wing top/bottom surface under 1 atm only (assuming wing is symmetric and at an A.o.A = 0 deg), then the net pressures would be zero and we wouldn't have any forces acting on the top or bottom surface of the wing.
Also, does the wing's top surface, in reality when it is flying, deform out (i.e. expands) or deforms in (i.e. shrink)? I think since the absolute pressure is still positive so it must deform in, but some sources say that it instead deforms out. (Assume a static structural condition). A such source I am attaching in the picture.

When applying a FEA loadcase, you should always keep in mind the complete picture of which forces are applied on any surface, and in what situation you consider the wing "undeformed".
If you start out with a solid wing in the vacuum of outer space, and descend into the atmosphere, then indeed the wing will compress under a hydrostatic pressure. But this is an unlikely scenario.
A much more likely scenario is that you want to compare the deformation from standing still to flying. The initial situation is already in the atmosphere, and you would typically say this is the undeformed situation. When you want to calculate the deformation when flying, you would only apply the pressure difference. This is the most common way of doing FEA analysis.
If you're interested, the following explains what happens if you do apply atmospheric pressure. Under the assumption of linearity, we're allowed to split the loadcase into differential pressure and atmospheric pressure. So the question is really what happens if you apply atmospheric pressure. The answer is: very little. Remember that atmospheric pressure also acts on any surface on the inside of the wing. The net result is that the entire wing is under hydrostatic pressure. This adds a measly 0.1MPa to the stress of the wing. Furthermore, most failure criteria for structural materials explicitly remove the hydrostatic stress. For example, in the Von Mises stress, hydrostatic pressure doesn't show up at all. So in effect, very little happens and only pressure differentials are applied in FEA.


Why do privater jets often fly at or above FL 400, but large commercial aircraft are usually in the range of FL 300 to FL 400? With rare exceptions (like the Embraer business jet, which is simply their commercial jet with a different interior), almost all private jets fly in the more rarified air above FL 400.
But, if its more efficient, why don't airliner fly at the same sorts of altitudes on long flights?

FL360 (plus or minus a bit) is the optimal altitude for fuel efficiency, which is the top priority for airlines. And airliners all fly at roughly the same speed (again, for fuel efficiency), so ATC can just line them up in a row and let them follow each other.
The problem is that level is severely congested with all those airliners. You can’t really get out of line or pass someone, which is another reason they’re all flying the same speed—and that has become a vicious cycle because Boeing and Airbus now design their planes to be most efficient at that speed.
Business jets passengers (and thus their operators) value speed over efficiency; if they didn’t, they’d use much cheaper airline flights. However, to avoid the airliner congestion around FL360, they have to climb to FL400 or higher, where they can fly faster and likely get a more direct route.


Are there (ideas for) GNSS based attitude indicators? With upcoming GNSS systems that have better accuracy than GPS, could there be an GNSS based attitude indicator? Does maybe one already exist?

I could imagine having 4 sensors (front, aft, left wingtip, right wingtip) that then calculate the attitude.

I suppose you could but what benefit wound a GNSS based system offer over traditional gyroscopic and AHARS based attitudes systems while offering better redundancy against a system reliant on outside radio sources and risks with system outages, etc?


How does an organization decide to evacuate planes (e.g. in a hurricane)? I recently became aware that Embry Riddle temporarily evacuated Florida to escape an oncoming hurricane, taking dozens of planes with it. How does an organization like this decide that planes are at significant risk of damage and shouldn't just be tied down in a storm?  I would think tying down a plane and especially hangaring it would be good against any storm that isn't hurling debris or knocking down buildings.  How bad does the weather have to be to decide to move all the planes?  Do airlines similarly remove all their airplanes from airports in a hurricane's path?

A line of Embry Riddle's plane's parked at Auburn, taken from Auburn's Facebook page.

This can be dependent on a few things. For larger organizations like airlines resources may not be an issue (they generally have pilots needed to move the planes). For smaller organizations it may come down to a few factors. First off do you have the people needed to move the planes (and how will you get them back home). Do you have anywhere to put the planes provided you do move them, you will need tie downs else where not to mention its going to cost you to store them elsewhere. On that note, can you foot the bill for such a move (not only the planes but the fuel, pilot housing or return trip etc...). If you want to see some of the damage and thought process for smaller planes check out this thread on the recent hurricane.

Often airlines will cancel inbound flights in advance of a hurricane so there will be fewer airplanes turning around at a potentially effected airport anyway. For the planes parked there (for what ever reason) they may they may simply move planes out of the airport,

  Airlines are moving some planes to hangars while flying other planes
  out of the area entirely until the storm is over.

FWIW commercial airframes are fairly transient by nature anyway, so as long as its not the location of a hub city the planes are in and out anyway.

While they have access to way more resources it looks like the Airforce moves planes appropriately.

As to what conditions lead to this decision its hard to say and ultimately up to the operator in question. Generally I would think they would err on the side of caution. But from a purely economical standpoint (potential damage aside) its may be more cost effective to move the planes and use them elsewhere than have them sit on the ground anyway (since the airports will be closed).


What is the problem in the satellite data of MH370 In the Inmarsat data of MH370, there are handshakes (BTO) with time (UTC) at: 19:41, 20:41, 21:41, 22:41, 00:11,00:19. Normally it pinged every hour, but why the 2nd to last happened at 00.11 that was 1.5 hour after the previous one? The last one happened at 00:19 is for what reason?

Also can ping be stopped manually, e.g. by turning off the power, then there will be no ping?

This was explained back in 2014 when the data was released. It is consistent with a loss of power due to fuel exhaustion, followed by battery power restoring communication.


How far could the Airbus A321XLR actually fly commercially? Airbus states

  It will offer even more range – up to 4,700 nm (8,700 km) – in a comfortable 2-class layout

There is an animation which contains this:

And that is 4735 miles. So now I am intensely curious what's actually possible.

Airbus is quoting the ranges in nautical miles (nm) which is typical for aircraft. The Great Circle Mapper you linked is using statute miles, which are shorter. If you switch it to be in nautical miles, you get 4115 nm, which is well within the quoted range.


Can a sonic boom arrive before the source? I'm on the ground, a fast jet flies from very near to the ground, I hear the sonic boom soon, but after the plane passes my point, right?

The real question I'm trying to solve is this:

I just heard an explosion-like sound, and then heard a jet pass. So this means there was an explosion. Am I correct?

One thing I doubt is that the "normal" sounds I heard after could also be "lagged", so it might have confused me about the timing, but I think that wouldn't make a big difference.

Assuming the aircraft you saw was traveling in a straight line, then the sonic boom you heard (assuming it was a sonic boom) could not have been generated from that same aircraft.  This is because the sonic boom is experienced at an angle back from the flight path of the aircraft.

Many aircraft which are capable of generating sonic booms also happen to fly in groups.  Fighter jets are a good example of this.  Fighter jets often train in groups of more than one aircraft.

It's possible you may have heard a sonic boom from another aircraft at a higher altitude which you did not see, then you later saw a new aircraft.  This is actually very likely, because sonic booms are much more common at high altitude.  The atmospheric conditions for creating sonic booms are favorable at high altitude.  This is because the speed of sound is much lower at high altitude compered to the speed of sound at low altitude.  It is difficult to see military aircraft at high altitude against a blue sky background because the military intentionally paints the skin of the aircraft in a grey color to make it difficult to see against a blue sky.  So without a con trail you likely did not see the fighter jet which was flying at high altitude.

Other commenters asserted supersonic flight is not allowed inside the US, but this is not entirely correct.  Many restricted airspaces in the US allow supersonic flight.  The restrictions on supersonic flight are generally put in place to balance the concern of noise pollution for the population.  Some MOA (military operating area) also allow supersonic flight, although usually only at high altitude.  Some areas of the eastern US which allow supersonic flight require the pilots to fill out a log stating supersonic flight occurred.  However, supersonic flight is easy to do accidentally in many fighter aircraft.  The pilot may not realize he was supersonic until reviewing the tapes after the flight.  Most airspaces allowing supersonic flight are over sparsely populated deserts of the western US.

Picture credit to Wikipedia


Are there some minimum criteria for a field to be registered with the FAA as an airstrip? I spend an unacceptable amount of time 'flying' around the country (U.S.) via Google Earth and I'm always zooming in on airplane symbols to have a look at airfields.  In the western U.S. there are lots of rural strips that have the little aircraft symbol on them which I'm presuming come from the FAA.  Some of these fields appear marginal at best as legitimate airfields, especially the ones that are obviously part of a farm or ranch.

My question is what level of improvement is necessary for a field to be listed by the FAA as an airstrip?  Is there some minimum length, width, slope, etc.?  Is there some inspection that is done before you can get put on the charts and are there any ongoing checks to make sure the field is still there when the charts are updated?  Does the owner of a strip assume some ongoing obligation as a result of their strip showing up on a sectional?

Good question.

14 CFR Part 139 requires FAA to issue airport operating certificates to airports that:

Serve scheduled and unscheduled air carrier aircraft with more than 30 seats;
Serve scheduled air carrier operations in aircraft with more than 9 seats but less than 31 seats.

Also:

  VFR charts depict airport's hard and soft surface runways. Enroute charts depict airports having hard surface runways of at least 3000-foot in length. If your airport meets those criteria, you may contact the local Federal Aviation Administration, Airports District Office or Aeronautical Information Management, AJV-21, at 1-(866) 295-8236 to have your airport charted.

That means for a private airstrip, it's your call as the owner to have it placed on a chart. Pretty cool.

More: https://www.faa.gov/licenses_certificates/airport_certification/


What is the different between an aircraft engine gearbox and an aircraft engine transmission? For an aircraft engine, what is the difference between a gearbox and a transmission?

I was of the understanding that a transmission is a type of gearbox. For example, in a helicopter, a transmission is used in to convert horizontal rotation of the turbo-shaft to a vertical shaft rotation. Is an aircraft engine gearbox and aircraft engine transmission the same thing?

Are there other types of gearboxes used in aircraft engines besides the transmission design?

In aircraft, transmission usually refers to the whole system, that transmits power between two points, say between the MGB and the tail rotor. Gearbox is usually a component of the transmission system (along with shafts, for example) which is used for changing rotational speed.

In a sense, a full transmission system is found only in helicopters, and not in fixed wing aircraft. The closest thing a fixed wing aircraft has to a transmission is the variable pitch propeller, which is analagous to the car transmission.

By nydano - Cut away view of Hamilton Standard Propeller, CC BY-SA 2.0, $3

On the other hand, a number of aircraft have gearboxes, especially the turboprops (and some piston engines), for reducing the engine output speed before turning the propeller. The following image shows the gearbox in a GE turboshaft engine.

Image from mrlarry.org

Turbofan engines do have a gearbox, which is used to run the accessories. The compressor is usually run through a shaft from the turbine, with various turbine stages running various compressor stages, while some turbofans do use gears between turbine and compressor, called geared turbofans.

Aircraft transmissions (whether helicopter or fixed wing) is usually one speed from one point to another, with speed reduction (or direction change) offered by the gearboxes.


What are these criss-cross patterns close to Cambridge Airport (UK)? To the immediate south of the runway at Cambridge airport, there are a large number of possibly-concrete things embedded in the grass.

I'm not sure whether they are have any aviation-related function, but they are mostly either parallel or perpendicular to the runway.

The question is - what are they?

Aerial view here.

In 2017 there was a major archeological dig in the area of Hatherdene Close and Coldhams Lane at the south end of the Cambridge airport.  The "criss-cross patterns" are additional exploratory trenches as part of a "Preliminary Archaeological Investigation".

Welcome
to the public consultation on the emerging development proposals for the creation of a new
neighbourhood at Land North of Cherry Hinton

Anglo-Saxon artefacts unearthed on Cambridge building site

The area is also the subject of a Planning Document. I had a quick read through the document and I found a reference to "Preliminary Archaeological Investigations", which are the trenches seen in the aerial photo.

LAND NORTH OF CHERRY HINTON Planning Document


Which photo more accurately represents Flaps 1 in a 737-800? or  A recent update in a sim craft changed the visuals from what I'm used to, but from my research it looks to be more realistic. This post clearly reflects the more extended option being more realistic - but can anyone confirm that that is how it looks on a flaps 1 setting irl?

Thanks in advance!

On the 737, flaps 1 actually means leading edge slats only and no trailing edge flaps.

Therefore the first photo is definitely wrong, while the second one is probably correct (since the slats cannot be seen).


Lockheed SR-71 take off protocol I'm intrigued by the Lockheed SR-71's take-off procedure, as it seems different to that of civilian aircraft. I would like to know what are the major differences in take-off procedure, and why?

For example, most aircraft begin to take off like the following: engine one on, warming up. Engine two on, warming up, etc. But is this the same for the SR-71 what was its take-off protocol?

If you are referencing the manuals found here the procedures look pretty standard to me. Granted they involve some thing specific to the plane they are generally what one would find. Pages 2-19 through 2-23 seems to cover the start up procedure and it looks pretty standard. Make sure ground unit is connected, check fuel flow, check engine is open, start, check RMP (provides some trouble shooting for RPM issues as well). It also goes on to say left engine first for odd flights and right engine first for even flights to keep the wear some what in line. There are a lot of "Note" sections but you are talking about one of if not the highest performance aircraft ever made so these are to be expected.


How is it possible for the MIG 21 to have full rudder to the left, but the nose wheel move freely to the right and then straight or to the left? How is it possible that the MIG 21 has the rudder to the left, but the nose wheel moves freely to the right, and then straight or to the left on the runway?
See timestamp 1 min 11 sec in this video:

Davidw mentioned the book "Red Eagles".  It has a passage about steering the MiG-17 and says the MiG-21 used exactly the same system.  In the following passage, he is quoting pilot Jose Oberle.
Red Eagles: America's Secret MiGs, Steve Davies, 2011

Taxiing the airplanes was a bit of a trick.  If you wanted to turn
right, you pushed the left [sic][a] rudder bar in and you pulsed this lever on
the control stick.  That dumped the pneumatic pressure to the brake
on the left wheel and transferred it to the right wheel.   You would
get the free-swinging nose wheel to start to turn to the right, and
then as you got ready to come out of that turn you'd have to push the
left rudder bar past neutral and you'd have to start pumping the
little paddle again to get the power back on the left wheel, to get
the nose to straighten out so you could taxi straight!

Per this, the nosewheel is not part of the steering system.
a: most definitely a typo, see for instance the following pilot's experience.
I Was Lucky: I Got to Be a Pilot, Paul "PK" Kimminau, 2017, p. 161

After checking the systems out, I taxied to the runway. That was an
experience in itself!! On US aircraft, the brakes are on the rudder
pedals, that is, you push on the tops which would rotate forward and
apply braking. Also on US aircraft, if you wanted to turn, you pushed
the rudder pedal just as if you were using rudder to fly the aircraft
and power steering would turn the nose wheel. On the MiG-17, the
braking was done with a lever on the control stick. You squeezed it
and applied brakes. If you wanted to turn, you pushed the rudder pedal
in and squeezed the brake lever, and it would apply braking to that
wheel so you turned in that direction.


What is the maximum interception angle for ILS when on radar vectoring? Some time ago when I was designing the approach radar module for the ATC simulator for HCAA, the spec was very clear that the limit had to be placed at 45 degrees. So I took it for granted and I didn't make any research of my own.

But very recently I had a discussion that made me wondering and I couldn't find any online documentation. I found Lnafziger's answer suggesting that

  Controllers may issue a heading or a course direct to a fix between the IF and FAF at intercept angles not greater than 30 degrees for both conventional and RNAV instrument approaches

So I guess this is it for FAA airspace. But I would like to know if there are any EASA regulations or ICAO recommendations that impose 45 degrees in Europe.

45 degrees.

8.9.3.6
Aircraft vectored for final approach should be given a heading or a series of headings calculated to close with the final approach track. The final vector shall enable the aircraft to be established in level flight on the final approach track prior to intercepting the specified or nominal glide path if an MLS, ILS or radar approach is to be made, and should provide an intercept angle with the final approach track of 45 degrees or less.

ICAO Doc 4444 (PANS-ATM)
That said, we very often use a 30 degree intercept angle, even if we are allowed to go up to 45 degrees.


How to fly for the United Nations? I can't find anything online about flying for the United Nations, either helicopter or fixed-wing, and any of their aviation programs, and I'm really interested in this. Can someone point me toward some more information about flying for the UN?

The UN charters aircraft full-time from ICAO-compliant commercial operators (the aircraft are also painted in the UN livery). So you need to be working at one of those airlines/operators the UN chooses, and then it will depend on that employer's internal policy.

To fulfill its mission, UNHAS uses a fleet of more than 90 aircraft, including helicopters, chartered from commercial air operators (...) (UNHAS)

For example, ET-ALJ (shown below) has been with Ethiopian Airlines since 2003, and it is now chartered to the UN since Aug 2020. Another example is VP-BOW, a currently Nordwind Airlines 737-800 that was chartered to the UN 2017–2018, and is now back in regular Nordwind service.

— https://www.jetphotos.com/photo/9937427

See also: Wikipedia: United Nations Humanitarian Air Service


Is it possible to install a bike rack on a Cessna 172? I stumbled upon a nice photo manipulation on aviationhumor.net.

Source

My question is short and concise:

Is it practically possible to do that? Is it okay in terms of aerodynamics, weight, CG?
Bonus Question: If it was possible, would there be any chance it gets certified for use?

Is it practically possible to do that? Is it okay in terms of
  weight, CG?

Bikes (depending on make and model) are not all that heavy and in this picture they are more or less center mass and would most likely fall in the CG range.

  aerodynamics

Again this depends on the bikes and the placement but with proper care you could be ok. Admittedly a bit different these bikes would create no more drag than say a wing walker would and people have been doing that for some time,

(source)

keep in mind bi-planes fly a bit slower than a 172. But on the small vehicle transit front the PBY-Catalina carried a full sized rowboat under its right wing for use when you arrived at your destination. Interestingly it seems to be mounted backwards which I would think is the non aerodynamic way to mount it...

(source)

It looks like at least one guy has actually managed to pull this off in New Zealand

(source)

  In case you were wondering if it’s legal, the Civil Aviation Authority
  of New Zealand has approved the design.

And he used a Cessna 185. Important to note that these are mounted under the wing which keeps them out of the way of the rudder as Dan mentions but more importantly should anything go wrong the bike would shear away and fall down away from the aircraft instead of back into the rudder.

It looks like this kit plane also offers a similar rack.

  ....If it was possible, would there be any chance it gets certified for use?

In New Zealand yes, in the US under the FAA, depends how good you are at paperwork.


Why are some engine nacelles thicker than others? Why are the engine pods on the Embraer 190 thicker, related to the overall diameter of the engine, than most of the other pods on other jets? Wouldn't this design add more drag and reduce efficiency?

Pictures added for reference.

Embraer 190:

Boeing 737:

Airbus A330

The nacelle contains a lot of equipment for controlling the engine. While this will certainly scale with the size of the engine, there is also some amount of minimum space needed for the components. The volume also increases faster than the surface area, so there is more room to spread things out. You will notice that the general trend in your pictures is relatively thinner nacelles as the engine diameter goes up:

E190 - CF34 - 57 in
B737 - CFM56 - 61 in
A330 - CF6 - 105 in

The difference between the CFM56 and CF34 isn't that great, but I think your image of the 737 isn't the best for comparison. If you look at an image more comparable to the CF34 picture you have, like this one, they appear much more similar.


What alternative methods are there for controlling a plane when flight control surfaces have failed? I saw a TV show once about Japan Airlines flight 123, in which the aft pressure bulkhead ruptured, disabling hydraulics and ripping off the vertical stabiliser. So the flight crashed after some time of flying with up-and-down oscillation.

Since then, I've also heard of two flights in which the aircraft lost control of flight control surfaces, but pilots guided their crippled plane into a landing using engine throttles only:

United Airlines flight 232
2003 Baghdad DHL attempted shootdown incident, in which a cargo plane in Iraq was hit on a wing by a missile

In principle, could such a method have been used in Japan Airlines flight 123?

In principle, would it be possible to control such a plane by use of cooperating passengers moving around in the cabin, e.g. by instruction of a pilot, to shift the weight balance of the aircraft?

As far as I understand, the JAL123 pilots did use thrust manipulation in an attempt to control their crippled aircraft -- however, Japan's largely mountainous terrain conspired against them, as trying to figure out fly-by-thrust-lever requires a massive quantity of airspace, and unfortunately for JAL123, there was a mountain in the way of that effort.  UAL232 and OO-DLL, on the other hand, both happened over relatively flat terrain, which meant that the aircrews could concentrate on working with their crippled airplanes to get them back on the ground as safely as possible, without having to worry about terrain clearance.

Of course, the missing vertical stab didn't help them either, as it meant they had to do much more work to control their airplane.


How can I know the manufacturer of the PFD (Primary Flight Display) of the current mainstream passenger aircraft? I'm developing a computer vision software based on the photos of these PFD (Primary Flight Display). How can I know the manufacturer of these PFD of the current mainstream passenger aircraft: B737. B747, B777, A320, A330, A340?
I have tried to Google and to find documents about these aircraft, for example, I know the device reference of the PFD of B737 is G1000 made by Garmin, but for others, it's really difficult to find out the device reference of their PFD.
Here is an example of the PFD of B737.

The 737 does NOT use a G1000... Many of these devices are made by companies like honeywell or the makers of the airframe themselves although they may very well source the physical screen from another manufacturer.


What is this old biplane? Can anyone identify this aeroplane?

Location is Cordoba, Argentina.

The aircraft is one of many (5 or 6) SAML-Aviatik type "S" and type "A" Italians that flew in Argentina in the '20s. All were for civilian use. Most had Colombo or FIAT engines in line, but the one in the photo (type "A") was the only with a rotary engine (Le Rhone?) that flew in Argentina. It belonged to the Italian pilot Renato Balleri, who together with the American Henry Johnson made public shows of flights, acrobatics, parachute jumping and flight baptisms throughout the country.
Henry Johnson died in an accident one of those events, in the city of Quilmes, in 1934.
The images are of this same plane in the province of San Luis.

Here an Italian SAML-Aviatik A.2...


What additional functionality is provided by the F-14 nose pitot, absent in early models? Early model F-14A had no nose pitot:

... but they seem to have quickly acquired them sometime in the late 1970s. The Iranian F-14s have them, and it's quite hard to find a picture of an F-14 without a nose pitot.

This is the nose pitot that appears on the majority of F-14s:

I believe the nose pitot measures angle of attack, a measurement I would have thought was critical to a big carrier-based aircraft like the F-14 from the outset.

So, why were the nose pitots introduced, and what effect did it have on the nature of piloting an F-14?

The probe on the nose isn't a pitot tube (although it might looks like one).

That's an AoA sensor as explained here: Home of M.A.T.S. - Sensor Probes

Reported from the link above:

  Angle-of-Attack Nose Probe: The Angle-of-Attack (AOA) is an essential dimension since it measures the angle between the aircraft's vertical flight direction and the vertical wind direction. A too high AOA means that at a given speed the wings will fail to produce lift which will result in a loss of controllability and stability. This is especially important during the landing phase where the aircraft is fairly slow approaching the carrier and also during air combat maneuvering where a loss of controllability can be deadly.
   Each AOA probe measures the pressure at several points and then the AOA is calculated. Usually, several AOA probes are installed to measure a correct AOA.
   Note that this probe was not installed on very early F-14As

The same site, on a related page, report what you've alredy found:

  The first fleet Tomcats were not equipped with any nose probe, but todays F-14s carry a small nose probe to gather air pressure data to calculate the angle-of-attack


For find a value of obstacles height below mentioned in intermediate segment why I should take the IAF MOCA instead of FAF MOCA? It is said that we have to think all risk of flight in this segment that's why we have to take the 4420ft because the plane can be situated any point in this interval

I am not sure if I fully understand your question. This may be the answer. If the Intermediate Segment does not have a published MOCA altitude, and there is no crossing altitude for the Intermediate Fix, you should stay at or above the Initial Segment MOCA. You can only descend when you are given published or explicit ATC instructions to do so.


When flying in uncontrolled airspace, which ATC frequency should I contact if I have an emergency? Question 1: If I am flying in uncontrolled airspace and I have an emergency, should I report on 121.5MHz if no ATC is within line of sight communication (which means I cannot hear the ATC and the ATC cannot hear me)?

Question 2:
Which frequency should I use to report the emergency in the following scenario? When the emergency happens, the aircraft is in uncontrolled airspace but near or approaching controlled airspace. There is an ATC station which is in charge of that airspace and the aircraft is within the line of sight of ATC (which means I may hear them), but my onboard radio coverage (the green circle indicated in the picture) cannot reach the ATC station (which means ATC cannot hear me). Should I report on the ATC frequency as maybe some aircraft are flying in the area and can relay the emergency to notify the ATC? Or should I just keep reporting on the common radio frequency like 121.5MHz?

The safest approach is to use 121.5 until someone instructs you to try another frequency.  ATC will monitor 121.5 at all locations it has antennas at. Additionally, military, some airlines, some medvac, and other operations will monitor 121.5  So your coverage will be greatest if you just use 121.5, unless you are already talking to ATC.

Addendum: Really in uncontrolled airspace?    If you are really in uncontrolled airspace, in the CONUS, you are likely flying rather low.  121.5 will be your best best in that case as well.  With enough time, you might work out a relay with higher traffic, perhaps on a center frequency.  But 121.5 remains the go to frequency.


Can any military aircraft (only fighter jets not the military cargo ones) be stopped using Arresting Gear technique? I know in mostly all of the seaborne landings on the Naval warships is done using Arresting Gear and there are some land based airfields also which used arrested gear methodology but do any aircraft specifically military ones (just the fighter jets)can be stopped using this or there is something specific feature in an aircraft which makes it Arresting gear compatible?

In order to engage the usual arresting gear (cables) on an aircraft carrier,
it helps to have a tail hook.

There are other forms of arresting gear that do not require a tail hook.
Presumably the main limitations on an aircraft using them are the size, weight,
and landing speed of the aircraft.
These devices do not seem to be designed for as frequent use as
the arresting cables of a carrier.

Followup: As I found out on looking into this further,
many (most? all?) present-day land-based fighter jets,
not just Navy or Marines jets, have tail hooks as well.
However, at least according to this blog entry,
tail hooks of the types of aircraft used by the US Air Force (and some other
air forces) are not designed to work with aircraft carrier arresting cables
but only with land-based systems (which suspend the cables higher than the
aircraft carrier systems do).

As mentioned in a comment (and in the Wikipedia article on "Arresting gear" linked above), barrier nets can serve as arresting gear.
Various publications (for example the Supplement Alaska, pp. 10–11,
accessed 22-Jan-2015)
list numerous kinds of gear, including cables designed to engage tail hooks, woven straps designed to be torn by tail hooks (one-time use only!), nets designed to engage struts, nets designed to engage wings, nets combined with cables, and engineered material arresting systems (EMAS) that absorb energy as they are crushed under the wheels of the aircraft. I have not yet found any citations of EMAS being used by military aircraft, but its main limitation of seems to be landing speed rather than aircraft weight or size, as an FAA fact sheet on EMAS dated December 12, 2014 credits these systems with stopping nine aircraft that overran runways in separate incidents, including a Boeing 747, an MD-11, and an Airbus A320.


Why do commercial airplanes smell like fuel smoke before take off? Why does the cabin of commercial airplanes always smell like fuel smoke coming out from the internal ventilation a few minutes before taking off, I think when the pilot puts thrust into the engines before going to the runway?

A few days ago I went on a trip and noticed this too, when landing. Is it normal?

What is the reason to have the passengers smoked?

Thanks!!

This is often a result of when the planes push back from the gate or if there is a direct tail wind on the ground. The pressurization system for aircraft uses bleed air from the compression stage of the engine. If the engines are running at push back or idling when a tail wind hits them the brief reversed airflow can cause some vaporous fuel to make its way forward in the engine and come through the air system causing the smell. This page covers it pretty well. Patrick Smith also touches upon it here.