How ribs angle change wing overall shape? How ribs angle change wing overall shape?

It depends on the rigidity of the upper and lower skins.
As far as large jets go, you see different variations; ribs parallel to the airflow, ribs perpendicular to one of the spars, ribs perpendicular to mean chord.  In the 737 cutaway below, they appear to be more or less perpendicular to the rear spar.
Aerodynamically it's not important on large swept wing aircraft, since the ribs' orientation doesn't impact the outer contour of the airfoil, because the upper and lower skins are very heavy and stiff and are effectively the spar caps (the primary tension and compression members of a box beam), and the "spars" are really just bulkheads closing the box at the front and back, with the ribs supporting the box. So whether you angle the rib this way or that doesn't make much difference and it comes mostly down to ease of manufacture.
On the other hand, if you have a swept fabric covered wing, or a metal wing with thin skins that can bulge between the ribs, then it could be an issue and ideally you'd want the ribs to be parallel to the local air stream (which may vary a bit from the free stream) as much as possible to minimize air flow "across the bulges" so to speak.  But if the upper and lower skins are stiff enough to retain their contour between the ribs, it makes no difference and you can orient the ribs in a way that makes it easiest to build the wing, with the rib contour shaped to accommodate the orientation in achieving the overall airfoil shape.


What minimum radio communication equipment is required in a homebuilt aircraft in India? Let's say I am building a single seat aircraft for flying in one's own country(India). What should be minimum set (Not only from compliance prospective but to have core set of communication for security and safety reasons with ATC or other receivers ) of things I must have on my aircraft?

Background : We are planning to provide this set of Radio systems for Hobby Aircraft builders.

Update : As per the answer, It is cleat that one do not need to have radio system always in the flight.

According to DGCA Rule 63 you need a radio onboard to operate both VFR and IFR

  63. Aircraft for which radio apparatus is obligatory-

  (1). All aircraft registered in India and required to be operated in accordance with VFR/IFR condition shall be provided with communication equipment which
  is capable of conducting two-way communication at all times with those
  aeronautical stations and on those frequencies as prescribed by the
  appropriate authority. The communication equipment so provided shall
  be of a type approved by the airworthiness authority of the country of
  manufacture of aircraft and acceptable to the Director General.

  (2).   An aircraft shall be provided with navigation equipment which will enable it to proceed :

(a)   in accordance with the flight plan; and

(b)   in accordance with the requirement of air traffic services, except
      when, if not so precluded by the appropriate authority, navigation for
      flights under the visual flight rules is accomplished by visual
      reference to landmarks at least every 110 kms (60 Nautical Miles).

DGCA Rule 9 also adds some stipulations to the operation of the radio its self

  9. Radio-telegraph apparatus -

  (1) No person shall operate radio transmitting apparatus in any aircraft registered in India unless he
  holds a licence of the type required by the provisions of Part V in
  respect of aircraft required by these rules to carry radio-telegraph
  or radio-telephone apparatus, as the case may be, and issued in
  accordance with those provisions.

  (2) Radio-transmitting apparatus carried in aircraft shall be operated
  under the conditions defined by the International Tele-communication
  Convention (Madrid, 1932) and the general radio-communication
  regulations annexed thereto as far as these apply and shall be
  operated only during the hours in which such operation is permitted by
  the Central Government.

  (3) Aircraft registered in India and required by these rules to carry
  radio-telegraph apparatus shall be fitted with such apparatus in
  accordance with the provisions of Part VII.

  (4) Nothing in this rule shall exempt any person from those provisions
  of the Indian Telegraph Act, 1885, and the rules made thereunder which
  require that radio-telegraph apparatus shall be licensed.

You can find the rest of the rules here. I went through them briefly and cant find a whole lot on certifying home built aircraft. Or what rules they would actually fly under. There is a short list of things related to actually getting an airworthiness cert here but it does not touch on VFR/IFR classifications related to that.

As for the safety aspect of it, that depends on your countries aviation infrastructure and if carrying a radio benefits you. If no one is listening on the other end then its not going to add much but weight to the aircraft. From a regulatory standpoint you may need it to enter certain airspaces (you may also need a transponder for that as well) I cant find a whole lot on the DGCA website about airspace regulations so its hard to say exactly when you would need one. I can only compare it to places I have flown and here in the US while you don't legally need a radio in uncontrolled airspace its still a good idea to have one and to use it as you should (CTAF announcements, flight following if you like, 121.5 if you need it etc.)


How much does it cost to design a jetliner's wing? The cost of designing a brand new wing for a jetliner, compared to modifying an existing one—with or without the changes to the production line—how is it estimated?
Related questions that come to mind: Are there various methods? Does the cruise speed (wind tunnel cost) and MTOW (size) affect the cost?

Context to prevent an XY problem:
MD-11 uses DC-10 wing to keep unit cost down; subpar initial performance
Speaking to Flight in 1987, Gary Smythe, chief customer engineer for the MD-11/DC-10, talked about the reason behind the minimal changes to the MD-11 wing compared to the DC-10.

To have gone for an all-new wing design "would add $10 million a copy to the price of an MD-11." That course of action would defeat the whole Douglas "low total ownership cost" approach.

Given that they projected 300 sales, that means the design (and manufacturing changes) would have cost \$3 billion (\$6.5 billion in 2017). The MD-11 had subpar performance for the Pacific market early on, and that was one of the reasons attributed to its low sales.
MD-90 uses MD-80 wing; subpar performance; rewing announced too late
The same thing happened with the MD-90 with its MD-80 wing. Because of this and despite having a cleaner wing of same area, same engines (V2500), and about the same seats as the A320, it could not achieve transcontinental range (both for the US and Europe), and it had longer takeoff runs.
An expensive re-wing was announced in Farnborough 1996, but was awaiting to be "sanctioned". There is no mention of the projected cost.

"It would be an all-new wing, not a revised version of the present one," says the president of MDC's Douglas Aircraft division, Mike Sears. The present wing design is a revision of the MD-80 wing. The MD-90's range is limited to intra-continental operations in the USA (Flight, 1996).

Only a few months later Boeing merged with MDC.
(Own work via boeing.com and airbus.com) Comparing the MD-90 and A320 wing and planform. Note that the MD-90 is one seat narrower.

This is what I could find, but perhaps there are other methods as well.

A 2002 MIT research[1] arrived at a correlation between weight and cost based on publicly available figures. The non-recurring (development) cost of a wing is broken down into:

engineering
manufacture engineering (ME)
tool design
tool fabrication
support

The engineering of a wing (clean slate) costs \$7,093 per pound. The total for the wing is \$17,731 (per pound). If it is not a clean slate design, say the DC-10 / MD-11 example, then it's 20% of the engineering, 5% of the tool design/fabrication, and 50% of the ME and support.
Applying to MD-11 and MD-90
The heaviest (OEW) MD-11 weighs 291,120 lb. With the wing 23% of that based on the research, and accounting for inflation (from the year 2000), the total development cost would have been $783 million (in 1987) for the wing if MDC had went with a new design.
MDC spent less than that for the whole "engineering, tools and flight testing," a cool \$700 million. Plus "$2.5 billion in inventory for initial production." (latimes.com, 1990)
Based on this method, the value is $328 million (in 1996 dollars) to redesign the MD-90 wing (full value, not just engineering).

Engineering
ME
Tool Design
Tool Fab
Support
Totals

40.0%
10.0%
10.5%
34.8%
4.7%
100.0%

Wing
\$7,093
\$1,773
\$1,862
\$6,171
\$833
\$17,731

Empennage
\$20,862
\$5,216
\$5,476
\$18,150
\$2,451
\$52,156

Fuselage
\$12,837
\$3,209
\$3,370
\$11,169
\$1,508
\$32,093

Landing Gear
\$999
\$250
\$262
\$869
\$117
\$2,499

Installed Engines
\$3,477
\$869
\$913
\$3,025
\$408
\$8,691

Systems
\$13,723
\$3,431
\$3,602
\$11,939
\$1,612
\$34,307

Payloads
\$4,305
\$1,076
\$1,130
\$3,746
\$506
\$10,763

Seeing how the table above shows how expensive the empennage and systems are, and with the major changes done to those areas on the MD-11, one can see why they went this way.
(Regarding a comment about the weight of composites vs. metals: a composite airliner is generally not lighter.)

1: Markish, Jacob. Valuation techniques for commercial aircraft program design. Diss. Massachusetts Institute of Technology, 2002.


Do motor glider pilots ever "cheat" and use their motors to thermal? Do motor glider pilots ever "cheat" and use their motors to thermal?

I understand there are 2 types of motor gliders:

Self launching: with about 80 hp very similar to an ultralight except a lot more aerodynamic. They can self launch (takeoff) themselves without a tow.
Sustainers: with about 15 hp, they cannot self launch, but can use the motor to sustain flight to get home if they cannot glide all the way home due to lack of thermals, sinking air, etc.

I understand gliders soaring over fields spend about 20% of their time thermalling to get altitude.

Why not just put on the motor to thermal faster and spend more time gliding (assuming you're not a purist)?

Is this ever done?

Do yachtsmen turn on the motor when under sail to increase their speed a little bit just for fun?  Not unless they have to get somewhere in a hurry, or to get somewhere when the wind dies. Kind of defeats the point of sailing.  Soaring is simply sailing turned from a 2 dimensional art to a 3 dimensional art, by rotating the lift vector created by moving air to a vertical axis from a horizontal one.

You have to understand that the whole point of soaring is the "game" you play with the atmosphere.  You're either into the game or you aren't and a motor pollutes the game if you use it while playing, except in specific circumstances.

Most motor gliders use the motor to launch and hunt for initial lift, then once lift is found, the motor goes off and the game starts (if you're are being towed and your tow pilot is any good, he/she is also hunting for lift for you while on tow and will try to get you near or in a thermal when you get to release altitude).

In general, you will use the motor mainly to launch and find lift, then only to rescue yourself if you get caught low.  So the motor is mostly to eliminate the tug, and the need for retrieve crews if you land out, or retrieve tows if you land out on a usable airstrip.  High performance motor gliders with retractable motors have to go through a retraction/extension procedure as well, so that is another factor in discouraging motor use until you really need it.  Of course, the other problem is you're more likely to need it, because the ballast of the launch motor hurts your sink rate, like having water ballast you can't get rid of, and it's more of a struggle to stay aloft in weak lift.  But again, this is normally a late in the day gotta-get-back situation.

On the other hand, there are "touring" motorgliders, with medium gliding performance and that are meant to be usable as long-range cross country aircraft in the travelling sense, with engines and props that facilitate starts and stops quickly at any time, as well as pure soaring, and landing gears that make normal power plane airport operations feasible.  You could really call these "hybrid" aircraft.

In these cases you may well indeed use the motor to supplement weak lift if it's to help you get from A to B.  But even there, you're making a lot of noise, and it's so much more pleasant with it off, so you'll avoid running the motor when you can.  This is probably more akin to "motorsailing" yachts that are a hybrid of power boat/sail boat.

With the newest electric motorgliders, you may use the motor more to help with thermaling, but they still make a bit of a racket compared to motor off (fast turning prop) and have limited endurance, so you still would tend to avoid using it unless necessary.


Why do helicopter rotors have constant section and angle of attack? As I understand it helicopter rotor blades keep a constant aerofoil section along their length, and are not twisted. Other rotating aerodynamic devices such as propellors, turbofan fans and wind turbines thicken and get a steeper angle towards the hub due to the lower incident airspeed (in the direction of rotation).

I'd guess it'd have something to do with variation of airspeed on the advancing and retreating sides maybe?

Edit: some are pointing out that this may in fact not be true, and that rotors can in fact have twist, just that it's less visually apparent. The chord at least would still appear to be constant

Edit 2: Since posting this I've taken a module in helicopter aerodynamics at uni, and the question is indeed wrong, blade twist is most definitely a feature of helicopter design.

Helicopter blades do have twist. The relative air speed increases from blade root to blade tip, and therefore on an untwisted blade lift would increase quadratically from root to tip. Or going the other way, lift would reduce quadratically from tip to root. Blade twist fixes this: it recuperates the lift generated on the inboard section of the rotor.

From Ray Prouty, Helicopter Aerodynamics Vol. 1., page 248:

  By twisting the blades to reduce the lift at the tip, the flow pattern can be made more uniform and the hover figure of merit can be improved by up to about 5%. Since this may represent a 20% increase in payload and since twisted blades are about as easy to manufacture as untwisted blades, there is a good reason to use twist - and all modern helicopters do.

Due to the aerodynamic lift equation, ideal blade twist would be non-linear: again, would vary quadratically with blade span. But this ideal twist is only ideal in the hover situation, and definitely not ideal in the factory when the blade needs to be produced.

Pouty's article is very much worth reading, and further mentions:

High twist produces vibrations by the centre of pressure traveling a lot during rotation.
Negative blade twist (tip angle lower) is good for retreating blade stall but bad for autorotation, which would be helped by positive blade twist.
Optimum twist differs for hovering In Ground Effect and Out of Ground Effect.


Do "Civil Aviation Regulations" and "Aeronautics Bulletins" still have any legal authority today? This is a history of the FAA from their site.

In the U.S., we had the original set of aviation laws known as aeronautical bulletins back in the 1920's and 1930's. Later (in 1938) we had the Civil Aviation Regulations (CARs), created by the Civil Aeronautics Authority (CAA), added to them.

I am curious if those laws were actually repealed or simply made redundant by today's regulations and whether or not there were additional laws not seen in the FARs today but which did exist in the CARs and Aeronautical Bulletins.

No, except for a type certification rule.

  Aug 23, 1958:

  President Eisenhower signed the Federal Aviation Act of 1958 (P.L.
  85-726) into law. Treating comprehensively the Federal role in
  fostering and regulating civil aeronautics and air commerce, the new
  statute repealed the Air Commerce Act of 1926, the Civil Aeronautics
  Act of 1938, the Airways Modernization Act of 1957, and those portions
  of the various Presidential reorganization plans dealing with civil
  aviation.

The aviation law slate was wiped clean and started fresh with the FAA, although many of the principles in the aeronautical bulletins and the Civil Aviation Regulations were clearly incorporated into the FARs we know today.


What was the first flight instrument ever used in an airplane? It's not magnetic compass, turn coordinator, stopwatch, wind meter, VVI, and airspeed indicator.
I want to know what is the first flight instrument.

It's the yaw string:

  The yaw string dates from the earliest days of aviation, and actually
  was the first flight instrument.

Picture:

Source


What is this old US Air Force plane? What model of plane is visible in this image?

Based on the unique 6x pusher-prop configuration, this looks like a derivative of the Convair B-36 Peacemaker. Looking up the Wikipedia article for the B-36 and scrolling down to the variants section, this seems like an XC-99 (or, more aptly, the XC-99):

Public domain image via United States Air Force - USAF photo via, Joaobsen, Wagner, Greer (1980), B-36 Peacemaker in action - Aircraft No. 42, Squadron/Signal Publications; 1st edition, ISBN-10: 0897471016

This was to be a passenger variant of the airframe, with a passenger capacity of up to 400 people. Beyond the prototype, it didn't enter service.


What does the “nose-high” product of inertia represent? I am reading this slide:

Source: http://www.stengel.mycpanel.princeton.edu/MAE331Lecture10.pdf

Is Izx always considered small and we can assume it is 0, as many texts assume?

I need to make this clear:
This is the body axis:

I assume that G is the center of mass, GZX is the symmetry plane. So  Iyz = Iyx = 0. But why is Ixz zero? Do they rotate the body coordinate system around Y axis so that Ixz = 0?

The $I_{xz}$ moment of inertia is a measure for how the weight is distributed in the xz plane.
You can obtain it by multiplying a unit of mass $dm$ by its distance in $x$ and $z$ from the center of gravity and taking the negative of it.
For discrete masses (blocks of mass) it looks like this:
$$ I_{xz} = \{-(x_1 \cdot z_1) \cdot m_1\} + \{-(x_2 \cdot z_2) \cdot m_2 \} + \{-(x_3 \cdot z_3) \cdot m_3 \} ... $$
If you look at the plane in question, you can see that it has a nose - which we can consider as one of the blocks - which is

Far in front of the c.o.g. (large value of $x$)
High up from the c.o.g. (large value of $z$)

If we plug this in the formula, we see it leads to large values of $I_{xz}$.
Similarly, there is also a lot of mass in the lower-right corner

Far behind the c.o.g. (large  negative value of $x$)
Low below the c.o.g. (large negative value of $z$)

In essence, everything that is on the x-z line contributes to this value, and as we see from the marked area in the image of the Valkyrie, there is a lot of mass around this line.
If your aircraft is symmetrical around the x or z axis (in terms of as much mass above/below front/aft the axis) you will get a low value of $I_{xz}$.
I guess that is the case for many aircraft, so they make the assumption of $I_{xz}=0$.
More information about the rotational moment of inertia can be found here.


Why did the Mercure fail? The Dassault Mercure was a French regional jet that first flew in 1971 and received its type certificate in February 1974; it resembled an enlarged, shorter-range 737-200, and was designed to serve higher-capacity short-haul routes.  The Mercure was an abysmal failure, with only eleven aircraft ever sold, all to French domestic carrier Air Inter.  Wikipedia states, citing Dassault’s own website, that the killer was its short range, only 2,080 km (1,125 nmi) with a typical payload, and reducing to 1,700 km (920 nmi) at maximum capacity.

Except... that doesn’t actually explain the Mercure’s failure to sell!

Sure, it didn’t have the range for long transcontinental or transoceanic crossings, but you don’t need that much range to be successful as an airliner, as evidenced by the profits made by regional-jet manufacturers.  The Mercure’s Wikipedia article - citing Dassault - admits as much, even as it makes the claim that the aircraft was doomed by its short range:

  This lack of interest was due to several factors, including the devaluation of the dollar and the oil crisis of the 1970s, but mainly because of the Mercure's operating range – suitable for domestic European operations but unable to sustain longer routes; at maximum payload, the aircraft's range was only 1,700 km.  [emphasis added]

1,700 km is plenty of range for European routes, and there are numerous other markets for high-capacity, short-range aircraft.  Japan, land of the 747 regional jet, comes immediately to mind, along with the other dense areas of East, Southeast, and South Asia and the Middle East.  Even infamously-spread-out North America should have been fertile ground, what with the multitudes of short routes (and even not-so-short ones; the Mercure would have had enough range to comfortably fly between New York and Chicago in a typical passenger configuration, although not in all-up sardine mode) in the northeastern and midwestern United States, eastern Canada, parts of the South, the West Coast, and the Caribbean.  As a point of comparison, the earlier Sud Caravelle - the fourth jetliner to enter revenue service,1 and the first-ever regional jet - had an even shorter range (1,700 km was its maximum range), and it was riotously successful, to the tune of 282 aircraft (some of the very last of these, ironically, going to Air Inter at the very same time they were contemplating the Mercure), despite also having a smaller passenger capacity.

What am I missing?  Why wasn’t the Dassault Mercure successful in the short-haul market?

1: Preceded by the Comet, the Tu-104, and the 707, in that order.

Mainly because the short haul market needed to wait for the deregulation of the late 70s into the early 80s that resulted in the creation, by the early 90s, of the hub and spoke concept with small regional jets feeding hubs where the mainliners were.

The CRJ200 was the main pioneer of this market, as an up to date rendition of a smaller regional feeder jet. At the time it was expected to sell maybe a couple hundred units, even within Canadair.


Is this blended wing body trijet airliner real? Is it a commercial plane? Is this a better design in any way than regular engines on the wings?

It is a blended body design. It is a hoax.  See similar photo from Popular Science magazine 2003 on wikipedia page: https://en.wikipedia.org/wiki/Blended_wing_body

By Source (WP:NFCC#4), Fair use, https://en.wikipedia.org/w/index.php?curid=37713174


If airfoils at low speed generate higher coefficient of lift, why is it not reflected in airfoil polars? If airfoils at low speed are able to generate a higher coefficient of lift, why is this not reflected in airfoil polars?

I understand airfoils generate a higher coefficient of lift at low Re numbers.

So I entered the NACA2312 airfoil in javafoil and generated a lift polar for the airfoil from Re 5,000 to 10 million. There was no increase in lift at lower Re numbers...

Why not?

No, they don't.

The Reynolds number is the ratio of inertial to viscous forces in a fluid. That means viscosity has proportionally more effect at lower Reynolds numbers. The boundary layer is proportionally thicker, friction steals more energy from the flow and lift is lower.

This answer contains a graph with a collection of empirical data, as does this answer. Here is another answer which covers both attached and separated flow. As you can see, Reynolds number effects mainly affect attached flow, and in a way that reduces lift for the same angle of attack; the more so, the closer you come to the stall angle of attack.

Just to save you from following all the links: See below for a plot of the venerable NACA 4412 from Abbott and Doenhoffs collection of airfoil data (picture source):

Note that the lift coefficient is plotted for Reynolds numbers R of 3, 6 and 9 million.


Is LHV or HHV used for calculating the thrust of a jet engine? Lower and Higher Heat Values (LHV or HHV) seem to have multiple definitions based on things I can't figure out.

What I want to know is, which one is appropriate to use for calculating the thrust from a jet engine? I'm thinking of large commercial turbofan engines like on the 747 or A380.

Also, since water vapor seems to have something to do with it, what about jet engines that run on hydrogen like the experimental Tu-155? Should we use LHV or HHV to calculate thrust in those engines?

The difference between both values is the energy set free when the water created by the combustion process condenses. Use the lower heat value for jet engine calculations. The water in a jet engine leaves it as vapor, and the vaporisation heat is lost for propulsion.


What is the difference between "sensitive" and "non-sensitive" altimeters? In this answer reference was made to "sensitive" and "non-sensitive" altimeters.

What is the definition of each, what are the differences, and why would one be used in preference to the other?

And why isn't it called an "insensitive" altimeter?

All altimeters are "sensitive" to some extent (an "insensitive" altimeter would be one where the internal pressure-sensing mechanism has failed: the pointer wouldn't ever move).

What the FAA calls a "sensitive altimeter" is simply more sensitive than a regular (now often called non-sensitive) one:

Non-Sensitive altimeters have a 1000-foot scale (200-foot tick marks) as their most precise display.
Sensitive altimeters have a 100-foot scale (20-foot tick marks) as their most precise display.

The sensitive altimeter in "glass cockpit" displays go even further, often having 1-foot resolution on a digital read-out.

Let's look at some (analog) examples:

Non-Sensitive Altimeter, not adjustable for barometric pressure

This altimeter is similar to what you'd find on an old Piper Cub: The scale is marked in thousands of feet, with ticks every 200 feet.

This altimeter is not adjustable for "barometric pressure", but it is adjustable: The little knob on the bottom rotates the face of the altimeter. Put field elevation under the needle before you take off and it should be a reasonable approximation of your current altitude for the duration & distance of a typical Piper Cub flight.
These altimeters can only be "set" on the ground, because you need to know your elevation to set the position of the face or needle.

Non-Sensitive Altimeter, adjustable for barometric pressure

These show up from time to time: It's a non-sensitive altimeter (same scale markings we saw above), but it's adjustable for barometric pressure. The Kollsman window on this one is marked in inches of mercury.
When you turn the knob on this altimeter the needle moves and the barometric pressure that corresponds to "zero feet" shows up in the Kollsman window. This makes it easier to read than the previous example, and easier to reset in flight based on radio information: You can set the local barometric pressure (QNH) in the Kollsman window and get your current altitude without having to be on the ground at a known elevation.

Sensitive altimeter, not adjustable for barometric pressure

In this sensitive altimeter you can see that there is a 100 foot scale (large pointer), and a 1000-foot scale (small pointer).

This is a bit of an unusual example: It's a sensitive altimeter that is NOT adjustable for barometric pressure (the knob simply adjusts the position of the pointers, and you set it to field elevation like you would with our first example. It can't be easily reset in flight as you need to know your current altitude to reset the altimeter correctly.

Sensitive Altimeter, adjustable for barometric pressure

This the altimeter most pilots are used to seeing in a "steam gauge" panel: It is a sensitive altimeter (note the 100-foot scale pointer), and it is adjustable for barometric pressure (note the Kollsman window, marked in millibars in this example). This is the type of altimeter required for IFR flight.
This one happens to include 3 pointers (100-foot, 1,000-foot, and 10,000 foot), because it's calibrated to 20,000 feet.

As with most aviation products there is a Technical Standard Order (TSO) behind altimeters which would get into all the specific details of the differences.
For sensitive altimeters it's TSO C10 (I believe C10b is current).
I'm not sure if there's one for a non-sensitive altimeter.


Am I required to have my Radiotelephone Operator's Restricted Certificate (Aeronautical) on-board the aircraft with me? Is there a Canadian law or regulation which requires me to have my Radiotelephone Operator's Restricted Certificate (Aeronautical) on-board the aircraft with me?

This is what I've found so far:

Canada requires you to hold the certificate (Radiocommunications regulations, Part V, Section 33):

  A person may operate radio apparatus in the aeronautical service, maritime service or amateur radio service only where the person holds an appropriate radio operator certificate [...]

However, I can't find a regulation saying I need the piece of paper with me.

An example of the wording Canada uses in its regulations to say that you need to actually have the document with you is at CARS 401.03 (1)(d) (regarding pilot licences):

  the person can produce the permit, licence or rating, and the certificate, when exercising those privileges.

I can't find that wording or anything like it relating to my radio operator's certificate in the CARS, the Radiocommunications Regulations, the Aeronautics Act, or the Radiocommunications Act.

There is no requirement to have the certificate with you on board during flight.

  The holder of a radio authorization shall, at the request of an inspector appointed pursuant to the Act, show the radio authorization or a copy thereof to the inspector within 48 hours after the request.

Source:Radiocommunication Regulations, s 38


How can I keep the data on a KLN89b GPS up to date? I'm looking at a Mooney M20C with a pretty dated panel, but it's airworthy and could be a great opportunity to build some retrac time. The KLN89b GPS is IFR Certified, but is positively ancient.

There seems to be a convoluted process to keep it up to date. I don't know if the present owner has the cable or the proprietary card reader. I've found some on eBay that seem to be for the KLN94 so I'm not sure if they will work with the KLN89b.

In my club we have a C172 with a GNS430 that has a fairly straightforward update process. I'm hoping the KLN89b is pretty similar if I get the card reader. I certainly don't want to take the entire GPS out of the aircraft and load it into a docking station every month.

If anyone can share their experience with this unit that would be great.

Thanks Guys. I've contacted the manufacturer and they said that there is an approved cable, only sold by avionics shops, that will connect an old fashioned serial port to the data port on the panel. If I get a USB to serial computer, I may be able to use Windows 10 to install the update. Maybe I'll have to downgrade to Win7.

I asked if there was a published end-of-service date for the unit and they stated that there was not. I also asked if there was a guarantee of future database availability for any period into the future and she said that there was no guarantee, but no plans that she knew of to phase the unit out.


What is this aircraft that has flown over my house all day? I mainly joined to ask this question. I would not have been so curious had it not flown directly over my house at least 5 times in about a half-hour. Every time my house started rumbling, I’d rush outside to snap some pictures before it was too far gone. Any help would be appreciated - especially if anyone knows why it came across so frequently.

Looks to me like a Boeing C-17, if you live near a military base or airport that may explain it.


How many active large commercial airplanes are there? For example, the 747 Wikipedia page says that 1500 747s were produced (that number seems quite low!).

Any indication of how many large, commercial aircraft there are, and what the breakdown between passenger and cargo is?

As mentioned this question is hard to answer very accurately without better access to data. It also depends on your definition of "large, commercial aircraft." Including all wide-body aircraft would be a large number of planes, and the totals are constantly changing as aircraft are delivered and retired.

This site will probably be the best resource for this kind of question. The data is probably not 100% accurate but it seems to be close. Other information is also available here.

I looked at the widebody models on the first linked site, sorting by status to find how many are in "Active" service. This does not include "Stored" aircraft which will be either put into service or not.

The models below total: 1026 cargo, 3825 passenger. This means about 21% of the 4851 widebodies are cargo aircraft, and widebodies constitute about 24% of the worldwide commercial aircraft fleet of 20000 aircraft.

747

There are 652 aircraft in service of 1500 delivered to date. Of these, about 289 are cargo aircraft. Excluding 28 aircraft operated by militaries or other organizations, this leaves about 335 passenger aircraft.

DC-10

There are 69 aircraft in service of 446 delivered. This does not include aircraft in military or firefighting services, or the aircraft used by Orbis.

A300

There are 255 active of 561 delivered. Excluding 6 in military or other service, this leaves 178 in cargo service and 71 in passenger service.

767

There are about 821 767 aircraft in service of 1062 delivered. About 165 are cargo versions, and excluding 16 in military or other service, this leaves 640 in passenger service.

A310

There are 105 active of 255 delivered. Excluding 17 in military or other service, this leaves 14 in cargo service and 74 in passenger service.

MD-11

There are 153 aircraft in service of 200 delivered. Only 3 of these are passenger aircraft. These are operated by KLM, and the last scheduled flight is October 25, 2014.

A330

There are 1069 active of 1112 delivered. Excluding 22 in military or other service, this leaves 27 in cargo service and 1020 in passenger service.

A340

There are 289 active of 377 delivered. Excluding 11 in military or other service, this leaves 278 aircraft in passenger service. If there are any versions used only for cargo, there aren't many.

777

There are about 1216 777 aircraft in service of 1230 delivered. About 134 are cargo versions, leaving about 1082 in passenger service.

A380

There are 139 delivered. There are no cargo variants and none out of service.

787

There are 183 delivered. There are no cargo variants and none out of service.


What is the purpose of a USB port in the cockpit? I'm definitely new to the site so apologies if this question is naive but google turned up no answers for me:

I was reading this article and read the following paragraph:

  As an example, Hypponen said he had recently spoken to a European aircraft maker that said it cleans the cockpits of its planes every week of malware designed for Android phones. The malware spread to the planes only because factory employees were charging their phones with the USB port in the cockpit.

The question that immediately sprung to my mind was:

  What is the intended purpose of USB port(s) in the plane cockpit?

Was it really intended for charging devices like phones? That seems naively insecure.

Some Flight Management System databases are updated via USB stick and require a USB port. Since navigational databases are updated frequently and require a simple way to make an update, USB (or memory card slots) are generally used to allow for rapid and easy updates without having to remove any panels. In some cases the port may be in the avionics bay however that is usually easily accessed as well. It should be noted that a recent change in regulation now allows pilots to update nav data, this question covers it well.

  Was it really intended for charging devices like phones? That seems
  naively insecure.

Generally these ports are not for charging but the basic design of a USB port more or less always allows you to charge from it because of the nature of the port. The security on the ports is more about cockpit security. In most cases the security lies in making it difficult to get into the cockpit in the first place. It is often assumed now that if you are in the cockpit you should be there. There is of course many questions this opens up some of which have been answered here or would be good to ask about.

As iPads become more common in the cockpit for navigation and the such USB ports are becoming more commonplace on panels for charging but this seems to be more common in GA planes currently.


Can some planes turn using just the rudder or without banking? I know you use the rudder when banking to keep the plane in the correct orientation, but is it possible, when making a slight turn with say a small private cessna, could you just use the rudder to turn?

Yes it is possible to turn without ailerons. It is not recommended though.
I have tried it on Cessna 172 as practice many times. I started practicing this maneuver some years ago after I witnessed a disabled Cessna with its ailerons jammed at an angle keeping it in perpetual turn was safely flown back to Van Nuys airport by an experienced instructor on the right seat. when you apply say left rudder the plane will bank left and turn left but you have to control the turn rate by power and rudder. The rate at which one applies the rudder is important; also you should be aware and anticipate potential risk of rolling.
Again it is not recommended but in case of emergency it could save the day!


Why is the center of pressure of a rocket at its centroid? From thin airfoil theory, at subsonic speeds, the center of pressure of any uncambered airfoil is at quarter chord. For sounding rockets, however, the center of pressure is generally assumed to be located at the centroid of the projected area. Note that model sounding rockets generally stay subsonic.

What is the theoretical derivation for this? For this question, one can ignore the effect of fins and restrict to the axisymmetric slender bodies.

This answer may not be what you are looking for, but I think the issue is we aren't really talking about the rocket as a "wing" here since these rockets fly ballistically.   I think the term CP in the NASA article would be better expressed as "neutral point", the point at which aerodynamic moments are in balance when the rocket is not aligned with the airflow, taking into account the body and all of its appendages.

So this would include the fins as part of the total lateral area subject to lateral air loads when the rocket yaws while flying ballistically, and to be stable, the rocket's center of mass needs to be forward of the neutral point, so that when it yaws, the corrective moment, acting at the aerodynamic neutral point, is created about the center of mass to bring it back into alignment with the airflow.

The term CP suggests that the rocket is flying like a lifting body wing, with a constant angle of attack and lift being generated to support its weight.  But as a ballistic object, its AOA is always ideally 0 and what lateral aerodynamic forces are being created are strictly to keep the rocket's tail lined up behind its nose as it travels its ballistic path.


How can I continue my flying career in the USA? I'd like some guidance for my career. I completed my basic CPL from South Africa in 2009 and got a job in January 2015 flying a C208B in Nepal. Now I'm in the USA for more than a year and I'm thinking about continuing my flying here. I have less than 300 hours.

So what do I do now? What is the process to convert my license to an FAA one? What would be a good flying school to join in New York?

There are a few things you will need to do to convert it over. You can find a lot of the information on the FAA's website here. This is pertaining to FAA FAR 61.75

Get your foreign license verified by the FAA. This takes 45-90 days and you cant make any moves until this is complete.
Find a local flight school. Once your license has been verified you can start your US training. Assuming you are not a resident you are going to need to get TSA approval to train.
Once you are TSA approved to train you can start to train here. While your hours will count from your previous experience you will still need to pass the FAA written exams and practical exams. As such you will need to learn a bit about general operations here specifically in the US.
Once you have done your training and are prepared to pass the tests and check rides you can schedule them. Your instructor will help you with this.

You will still need to progress through the US certifications PPL->Instrument Rating->CPL and complete all required flight time and tasks to do so. There is no minimum time between check rides so if you have completed all the exams and tasks you can do them all one after another.


Problem with right crosswind landing but not left The prevailing winds where I'm training are almost always straight down the runway or from the left. I have no problem landing on (and staying on) centerline in either case.

However, when the crosswind is from the right, I tend to land on the centerline and then skip leftward.

I thought it was just me being inconsistent about my crosswind correction. However, during a recent lesson with wind 090, I was nailing every landing on 18, but when tower turned the airport around, I botched every landing on 36, so that seems to rule out coincidentally having a bad day every time there happens to be a right crosswind.

My CFI can't explain why I'm only having a problem with one side, much less how to fix it, and seems to be blowing it off since (now that the winds are back to normal) the problem has "gone away" again, but I'm not satisfied with that.

What could be causing this, and how do I practice for right crosswinds specifically when they are relatively rare here?

In my opinion it's because of your left of centerline vantage point and the sight picture burned into your brain by the always left side crosswind aspect, and in your particular case the transition to an opposite aspect is confusing your eye/brain/hands-feet processing more than other people. Everybody has their learning quirks.

The sight picture you are used to from your seating position, which includes the azimuth aspect (heading relative to center line) and bank angle from side slip, is a much bigger deal than a lot of people think.  When pilots start flight instructor training, one of the first airborne activities is learning to fly a trainer from the right side.  Some adjust right away, and for some it's like learning to land all over again.  In your case it seems you are having a similar problem with the left crab/right crab change in sight picture from the left side.

You just need to practice right side crosswind landings until that sight picture starts to sink in and responses become automated, and then you will wonder what all the fuss is about.

I second Carlo's suggestion to use a home computer flight sim for this sort of thing, which are perfect for this sort of "sight picture" learning (use Track-IR as well because this provides much more realistic sight picture movement).  Should help a lot.  But, be careful that when you practice things at home you are practicing correct procedures, not reinforcing wrong ones; that's the one big pitfall of using home sims for practice/proficiency.


D.B Cooper incident - What caused the tail to move after a jump? In the Wiki page on "D.B Cooper", the presumed moment he jumped out of the aircraft is described:

  At approximately 8:13 p.m., the aircraft's tail section sustained a sudden upward movement, significant enough to require trimming to bring the plane back to level flight.

This was replicated in a test:

  In an experimental re-creation, Scott piloted the aircraft used in the hijacking in the same flight configuration. FBI agents, pushing a 200-pound (91 kg) sled out of the open airstair, were able to reproduce the upward motion of the tail section described by the flight crew at 8:13 p.m

What was the likely cause of this? My initial thought was it was his body striking the tail, but that isn't mentioned and doesn't seem to be what happened in the test.

The "sudden upward tail movement" requires nothing more than a sudden unloading of the tail by removing that 90+ kg of man, parachute, and money.

Even with an aircraft as large as a 727, suddenly removing 90+ kg from the tailcone airstair would result in a pretty noticeable shift in trim requirement, with additional tail downforce required to restore level flight.  This is especially true when flying at the low speed Cooper had demanded (to allow a more-or-less safe jump).


What type of supersonic intake does the Dassault Rafale fighter jet have? What type of supersonic intake does the Dassault Rafale use? Is it a Pitot Intake? It cannot be a Ramp Intake, nor can it be a Spike Intake / Cone Intake, and it does not seem as a Diverterless Supersonic Inlet either.
Are there any explanations for the half-circular shape of the two intakes?

Sources for supersonic intake types: NASA Website, Aviation.SE Answers 1 and 2, Lockheed Martin CODE ONE Magazine

The semi-ventral pitot air intakes is a compromise between Ventral and Side Mounting where the intakes and their ducts are placed on the lower corner of the fuselage. In order to prevent interaction in case of single engine failure Rafale uses two semi-circular air intakes on the windward side, separated by the body.

Intakes are separated from the fuselage so as to avoid capturing the fuselage boundary layer (layer of air where air slows from high velocity relative to aircraft at its edge to standstill at the surface itself) as boundary layer, if enters engine, impairs pressure recovery and increases distortion, thus lowering intake performance; space between intake and fuselage is called external boundary layer bleed. This space is repartitioned, and expansion waves from it energize canard root vortex. Engine cooling duct is also located in this layer. In case the Rafale is equipped with stronger engine, intakes can be enlarged.

The architecture of the air intakes along with the nose and main undercarriages gives the capability for a large store to be carried under the fuselage, which is essential to achieve certain Air-to-Ground missions


In turbojet engines, does the fan play a key role in the air intake to the inlet? In turbojet engines, does the fan play a key role in the air intake to the inlet?

In turbojet there is no fan. Very simply, turbofan means turbojet + fan in front connected to the LP shaft.


Are there any problems opening a helipad close to an airport? I am looking at the possibility of installing a helipad at my house which is within 1.5 miles of a Class D airport. The location is not in the approach to any of the runways, however.

I am not a rotorcraft guy, so I am wondering if having a helipad this close to an airport will cause any issues?

(note that the whole area is Class B airspace, so it will always require a clearance to take off)

In the US, normally it is not a problem.  I would talk with the tower supervisor, to see if a planner could be consulted before you go too far down the road and start paving or something like that.

A good place to start would be a memorandum of understanding, where you and the FAA would work out the operations out of the field, and discuss arrival and departure coordination.

I could come up with a list of twenty heliports within 1.5 miles of Class C or D airports. Funny how hospitals end up near airports. Ditto for police facilities.

Life is easier if you do not plan on trying to get instrument approaches.


What are the differences between Canadian VNCs and US Sectional charts? I've been looking at Canadian VNCs (VFR Navigation Charts) and they look surprisingly different from US sectionals. A big difference seems to be how the airspace is designed, but there seem to be a lot of other differences in how information is displayed. For example, here is the Denver class B airspace:

You have your basic upside down wedding cake, and a mode C veil.

Now here is the Calgary, Canada class B airspace:

Even though it's not a full picture of the airspace, there are some differences that jump out, like the choice of colors to indicate the airspace boundaries and elevation, and the fact that the airspace is HUGE! There is also no clear indication of a mode C veil, or the bottom/top of the airspace. Another thing I've noticed is the huge number of airspace boundaries, indicated by the lines that looks something like this: -_-_-_-_.

One more thing. There is no information about the Calgary or Springbank airports. Are airspace elevations, airport elevation, and frequencies all things you have to look up separately?

The short answer is the charts are different because they're made by different groups - NAV CANADA has different charting standards than the FAA/NACO uses.

Similarly Jeppesen makes VFR charts for the United States, and they look very different from a FAA/NACO chart:

I have charitably described the Jeppesen VFR+GPS charts as "technicolor puppy vomit" on more than one occasion.

As far as I'm aware there's no comprehensive listing of all the differences between the US VFR Sectional format and the Canadian VNC format, but the NavCanada charts have a legend and there Canada Flight Supplement (CFS) contains a great deal of additional information - it's essentially similar to the US Airport/Facility directory.

Unlike the US charts, Canadian Aeronautical Charts--including the VNC--do not have a specific expiration date. They are revised periodically.


What is the difference between reversible and irreversible controls? What is the difference between reversible and irreversible controls ?

Reversible is when there is a direct linkage from controls to control surfaces. For example the cable linkages in a light aircraft up to an MD-80.

Irreversible is when there is a hydraulic power control unit in the way, it can be mechanical or fly-by-wire. And such controls would sometimes need an artificial feel system to relay how much force is being applied.

It is found in airplanes that cannot be steered by just muscles.

A good way to picture it, is what happens if you move an aileron by hand, would the yoke turn as a result or no. Superman might be needed for a 747's rudder, but still, the rudder pedals won't budge.

More information here and here.

Source: airlinebuzz.com

Photo shows an unpowered rudder that was swung by the wind, in the cockpit the rudder pedals would show the neutral position, hence irreversible.


Is the 777X actually the newest Boeing plane? I don't think the 777X is actually the newest Boeing plane (in april 2020), since it's only a new variant of a previous Boeing plane. So the actual newest plane would belong to the 787, since it's the newest plane. If that makes sense? Can anyone answer why Google says the 777X is the newest Boeing plane?

While the 777X is a derivation from the older 777 Classic family of airplanes, it is, in fact a brand new airplane, similar to the difference between the 747-8 and the 747 Classic line or the F/A-18E/F Super Hornet compared with the F/A-18A-D series. Based on that and the rollout date of the 777X, it would be BCA’s latest airplane.


Was the Buran space shuttle capable of doing a go-around? In several places I've seen reference to the Buran automated landing where it supposedly did a go-around and came in for a second landing attempt.  I was under the impression that the Buran was unpowered and therefore didn't have any ability to fire engines to regain speed (and therefore altitude) for another landing attempt.  Is this go-around an urban legend, or am I mistaken about what Buran was capable of doing on landing?

Unlike Space Shuttle, Buran could cary Saturn AL-31 jet engines. The testing version had four such engines and used to take off and then fly under own power during the tests. Hence it so should have been capable of go-around. The powered landing increased the safety of Buran in comparison to Space Shuttle (source).

Here it is possible to find the description of the jet engine system of Buran. This source names the engines as АЛ-31Ф (Su-33 has the same). It says two engines were foreseen for the space going version, and this would have not been sufficient to take off under own power. Each engine had the maximal thrust of 7770 kgf (afterburners were removed). The two extra engines of the take of - capable prototype were more powerful (12500 kgf).

The source also says jet that engines were not installed during the only space flight 15 November 1988 while there were non-functional engine controls in the cockpit. The engines were not ready yet.

Hence most likely the sources OP references talk about some go-around of the mentioned four - engine testing prototype, not about the go-around of the Buran returning from space.

The space going version of the Buran space shuttle was not capable of go around maneuver.


Where is an EASA PPL valid outside of Europe? I am considering obtaining an EASA PPL in the U.K. I would like to know where exactly in the world the license is recognized with little to no additional paperwork/training outside of Europe. Specifically I would like to know what is needed to fly in the Caribbean, Colombia or Chile with this license.

I am a complete aviation beginner so apologies if this is a silly question.

Yes, the EASA PPL is valid worldwide, but you must check the local laws prior to fly, for example, here in Brazil to fly a Brazilian registrated airplane (PT-***) you shoud have an ANAC PPL license, but if you are flying to Brazil in an UK based Aircraft( reg. G-****), you can fly it with your EASA PPL.

If you intent to Fly a Non-European aircraft for a long period in a same country, you should validate your EASA license within the local Aviation Authority, that ensures that you get the same level of license as you have from EASA.


What is the difference between RNAV and RNP? What is the difference between RNAV and RNP?  I know that RNAV doesn't need monitoring and alerting, but RNP does.

RNP is a superset of RNAV requirements. It applies and communicates a performance specification for RNAV that may vary by location rather than by equipment.

On board performance monitoring in RNP requires an alert when the system cannot guarantee with sufficient integrity that position meets required accuracy. Required accuracy can vary. A tight approach may require 0.1nm accuracy while 5-10nm over oceans might be acceptable. RNP requires communication of a numeric qualifier for accuracy. RNAV has no such mechanism.

Confusion is understandable as the terms are sometimes used interchangeably. ICAO is arguing with FAA and other countries to rename RNAV approaches as RNP approaches. The ICAO position is more clear, the FAA position supports existing equipment and training. Everyone believes a navigation performance spec needs to be communicated to pilots in charts and equipment, but there is no clear answer as to how to do it at this point.


What turbine temp. would result from burning pure stoichiometrically? I've heard that jet engine efficiency is limited by turbine temperatures---that is, the max temp. that the turbine blade alloy can withstand before weakening too much.
So jet engines are run fuel-lean. But they do achieve > 99% combustion of all fuel, so at least that's good. However, if we could burn stoichiometrically, then the engine could be smaller and lighter since it would need less air intake for the core.
So I want to know what is the max temperature that would result if you tried to burn pure stoichiometric?
BTW, to keep it simple, I'm asking about TIT (Turbine Inlet Temperature), which is the temperature of the gas right after combustion, right before it enters the first turbine stage. You can actually do complicated cooling on the blades to keep them less hot than that temperature somehow but I don't wanna get into that aspect.
Note, I'm interested in any typical large jet engine, like the PW6000, running at cruising conditions.
I found an example of actual TIT saying 1600 C: Mitsubishi site link. However, it was a gas turbine not jet engine, so I can't be sure if this is typical for jets too. What I want to know is the theoretical TIT if you could burn pure stoichiometric, to see what the difference is.

One may use the data I found for a previous answer for a PT-6 turboprop:

Ambient: 300K
Compressor discharge: 600K
Turbine inlet: 1200K
Exhaust: 800K

So, the combustor (between the compressor discharge and turbine inlet) adds 600K. Let's assume this happens at $\varphi=0.45%$ fuel equivalence ratio, which is equivalent to about 3% of fuel by mass. Since that's so low, we may also assume that all energy is put into heating the air (both the air used for combustion and the excess air for cooling the flow before the turbine). We start with a $\Delta T_c=1200K-600K = 600K$. Since a combustor is approximately isobaric, we can use the $c_p$ heat capacity for the reaction products, which is (for an ideal gas) not a function of temperature. We can thus simply calculate the stoichiometric temperature increase $$\Delta T_{s} = \frac{\Delta T_c}{\varphi} = \frac{600K}{0.45} = 1333K.$$ So the turbine inlet temperature is then $600K+1333K = 1933K.$ In reality, fuel heating (especially fuel evaporation) will represent a more sizeable chunk near stoichiometry, but I think it's safe to assume it's around the $1900K$ range.
Note however that the theoretical efficiency (ignoring the inevitable viscous losses from handling such a large flow of air) is determined solely by the pressure ratio of the compressor: $$\eta = 1-\left(\frac{P_1}{P_2}\right)^\frac{\gamma-1}{\gamma}.$$ So if TIT were not an issue, by enriching the mixture closer to stoichiometric, we do reduce the mass flow required through the engine (at constant power), so we proportionally reduce the viscous losses in the engine. If on the other hand viscous losses did not exist, for the most efficient design we would increase the compression ratio and lean the mixture even further to the point where the compressor discharge and turbine inlet temperature would be almost equal.


What pitch attitudes are common during an emergency descent for an airliner? What pitch attitudes are common during an emergency descent? I assume it would be a fairly nose-down attitude, but I can't imagine how steep would feel to the passengers.
Suppose a gradual decompression takes place and no structural damage is present nor suspected. What would be the pitch attitude for common airliners like the Airbus A320 or the Boeing 737?

My experience was on the Regional Jets but from sim training I recall that the pitch down once at Vmo with flight spoilers extended was somewhere around 10-15 deg.  The standard procedure for the CRJ was to declare "emergency descent", slam the thrust levers to idle, flight spoilers fully out, dial the Autopilot altitude preselect to 10000 ft, select the Autopilot to Speed Mode, and dial the speed select to Vmo, and just let the airplane do its thing while the two of you went through the QRH.
You will get a small G reduction during the pushover, but the AP would pushover gently enough to avoid making people in the back float around.  If you push over manually, there is a risk of pushing too hard in the stress of the situation and banging heads against the ceiling in the back (it doesn't take much when you're going fast like that).
Any G reduction that occurs is only momentarily during the pushover.  Once up to speed you are back to 1 G more or less. The pitch attitude in the descent would be noticeable to a passenger looking out the window from the slanting horizon, but I don't think it would look like they were diving straight at the ground.  The scarier part would be the rumble from the spoilers being out, and the roar in the cabin from flying at Vmo.


Why don't airlines place some physical separator between passengers in the planes to prevent the spread of COVID-19? Why don't airlines place some physical separator between passengers in the planes to prevent the spread of COVID-19?
A bit like the following, but adapted for cabins and viruses:

(image source)

Cost. Those would be expensive, and the business is bad already. Now, you might think that just any mesh, fabric or membrane would do, but but to be effective against the sperad of viruses, nope.
Discomfort. Imagine how it would feel to be bagged up like that for hours. Again, despite the membrane being a "breathing" sort, it would still get rather hot and huimid inside that contraption very quickly.
Restrictiveness. Imagine an evacuation situation with people in those. Very dangerous, not gonna work.

Masks are very effective, cheap, and people are quite willing to use them (excluding some mentally challenged cases). The ventilation in planes is also rather safe when considering the spreading of viruses (see this ASE Q&A), especially when combined with the use of masks. Planes usually have very good filtering of recycled air, and much of the air is not even recycled.


How does an aircraft move on the ground? Does an aircraft such as Airbus or Boeing have motors similar to cars, so that they turn the wheels?
or do they move on the ground with their engines, the same way they fly?

For movement on the ground the aircraft uses it own engines, however since the aircraft cannot move backwards on its own, there are pushback trucks on the airport

A pushback truck lifts the front weel of the aircraft, their role in most airports is to move the aircraft away from the parking spot on to the taxiways. Here the truck is removed and when all platform staff is out of the way the engines are started one by one. From here on the aircraft moves on its own power to the runway. In the aircraft you will hear the engine spinning up when power is demanded for acceleration.


Does the Zenith have anything to do with the read-out of an IRU accelerometer? Let's say that I have an accelerometer as part of an inertial reference system. Will the position of the Zenith with-respect-to the current position (in terms of rotation) of my accelerometer, have any impact on the accelerometer readings? Is there any kind of relationship at all?

Or, in other words, do we ever speak of accelerometers as part of an IRU... in terms of relationship with the Zenith?

Good question.

Another name for the "position of the Zenith" would be the gravity vector. Which for an aircraft is always down (shortest distance to reunite with terra firma).

  Note that it is necessary to subtract acceleration due to gravity from the vertical channel before performing the integration.—An introduction to inertial navigation

So the answer is yes, the acceleration due to the gravity vector is corrected.

Check the PDF for a detailed description and equations.


Why don't pushback tugs take the aircraft to the runway? As we know aircrafts have to turn on their engines to taxi the entire way to the runway, if pushback tugs are used, it would save a lot of ATF and overall costs.

Is there any specific regulation by the FAA preventing the pushback tugs from taking the aircraft to the runway, rather than the taxiway?

Image Source: Wikipedia

Way slower, more congested, more damage risk, many more expensive tugs required.  Taxiing under power is much faster and safer than towing in general (towing is a high risk operation and all sorts of bad things happen when tugs move large aircraft). It would be a mess on a taxiway with a line up waiting to take off with trucks and personnel mingling with ready to fly jets.  Generally, when you are flying you want the towing unit disconnected and gone ASAP.

The only reason you have tugs at gates in the first place is because of the need to back up; they're just there for the pushback.  If someone designed a gate with a pass through design that didn't require backing up and allowed for at at least one engine running, you wouldn't have tugs there at all.


What is the purpose of the winglets on the Socata TB-31 Omega vertical stabilizer? Aérospatiale-Socata built a prototype of the TB-31 for the French Air Force, which never went to production:

Source: netAirspace.com, photo by miamiair

What is the purpose of the winglets at the top of the vertical stabilizer?

What you observe here are VHF nav antennas for a VOR receiver.  This antenna design is lower drag than wire whip antennas.

The antenna serves no aerodynamic purpose except to minimize its own drag profile.


Where can I find (online) manuals for refueling A320/B737 for a given destination? Surely, airline crews must have manuals/apps by which they calculate the (minimum) amount of refueling before departure to a given destination. I have been looking online for such sources, with zero hits.

Specifically, I'm intersted in such free manuals/apps for the Airbus A318...A321 and Boeing B737 families.

Very rarely will a manual directly be used by flight crew for calculation of fuel uplift.

Flight crews generally receive an Operational Flight Plan prepared by the operator (the airline), or an agent of the operator, where calculations have been made for how much fuel will be required for the specific flight, and necessary reserves. Flight crew may elect to revise the fuel required to provide additional margin for weather, traffic or other factors.

The calculations made for the Operational Flight Plan are made with flight planning software, which in its turn uses data from performance manuals/data sets, and takes a large amount of parameters into account (routing (duh!), wind, flight altitude, speed, aircraft weight, load distribution (c.g.), alternate airport availability etc).

Flight crew can however make simplified fuel calculations using the FPPM for the aircraft type (Flight Performance and Planning Manual) (Boeing). The flight profile is however generally quite limited to a few climb/cruise/descent schedules, and the data is not what would be used on a normal line day. Distribution of FPPM (and other manuals) is generally restricted. If you however would come across a replica of a FPPM, you could probably make a usable fuel calculation using the instructions within it.


Do fly-by-wire fighter aircraft automatically reverse the direction of control surface deflections during a tailslide? During a tailslide (a flight regime where the relative airflow over the aircraft is from the tail towards the nose; i.e., an attack angle between 90º and 270º; i.e., the airplane is moving tail-first), the airflow over the aircraft’s control surfaces is in the opposite of the usual direction, causing deflections of the aircraft’s flight control surfaces to produce motions opposite those that would be produced in forward flight (for instance, in a tailslide, applying up elevator will cause the nose to pitch down, and left rudder will yaw the nose right).

Given that:

modern fighter aircraft use computerised fly-by-wire control systems instead of the mechanical linkages used in pre-21st-century fighters;
fighters are optimised for extreme maneuverability to the extent that a tailslide would be very easy to enter;
intentional tailslides could easily occur during combat maneuvering, or - even more likely - during an airshow;
and the control reversal inherent in a tailslide, like all types of flight control reversal, could easily kill an unwary pilot;

do modern fighters, during a tailslide, automatically reverse the commanded direction of flight control surface deflections relative to the direction that would be used in normal flight (for instance, applying down elevator rather than up if the pilot pulls back on the yoke in a tailslide)?

While the reversal of flight controls does happen, it is transient in nature, and in virtually all cases if you let the aircraft "fly" itself it will pitch down and recover.

Only aircraft with thrust to weight ratio of at least 1 to 1, and thrust vectoring of some sort if a jet, will be able to maintain the nose high attitude.

Prop aircraft are a different story as they essentially "hang" from the prop if the engine can develop enough power to do that.

Recovering from a tail slide is not like recovering from a stall or spin, you can't really use flight controls for anything until the aircraft develops enough airspeed for them to be effective, and in 100% of the times I have been in one, by that time the relative wind is normal and not reversed.

The exception is in prop aircraft where the prop wash against the rudder and elevator does provide some control effectiveness, but not reversed.


What would be the effects of installing pitot tubes on the engine covers? What are the effects on airspeed measurements, if the pitot tubes were installed right on the engine covers of an aircraft instead of being on the nose.  Would the reading be false? If so, would the reading be underestimated or overestimated and why?

There is a very good reason to install pitot tubes in a place with relatively constant environmental circumstances: calibration.

Image source

When installed at around the nose of the aircraft, the pitot always have a good view of the airflow, at all angles of attack and of sideslip. These parameters do distort the pressure reading, that is why during aircraft development the prototype tows a flying pitot tube and compares measurements. These measurement sets are used for calibration.

If it was installed on the engine covers, not only the aircraft state but also the engine state would have influence on the reading. A nightmare to calibrate, and prone to unforeseen errors for instance if a fan blade breaks off and the wobbling fan causes an airstream situation that was not accounted for.

Best to use the prime location: the nose.


What is the optimal time to get from ASEL to ASES certification? I am currently a ASEL pilot, in process of studying for IR, and will then be proceeding to AMEL. I know that if one holds ASEL & IR, and takes AMEL with instrument maneuvers included in the checkride, at the end I will have IR privileges in both single and multi.

What is the most optimal (time & cost) route to get my ASES? Are there any efficiencies to be had by completing seaplane rating after IR and/or multi? Or if I was to complete ASES before IR, once IR is done, I could exercise IR privileges when operating a seaplane (unlikely scenario, just want to understand the rules). From my understanding, I will, because IR applies to the category of airplane. Is my understanding correct?

The instrument airplane PTS has both maneuvers for single and multi engine airplanes. Obviously, when you first get your IR in an ASEL airplane you cannot complete the maneuvers required for multi-engine airplane.  Hence, if you choose not complete those maneuvers when you take your AMEL checkride, you will be limited to VFR.

There are no specific IR maneuvers in a seaplane so once you complete your IR in a ASEL airplane, you will also have IR privileges in a ASES airplane.

The answer is found in the instrument PTS / ACS book.

If you were to have both ASEL and AMEL ratings and took your initial IR in a AMEL, it would be valid for all aircraft that you are rated in or get rated in later on: ASEL, ASES, AMEL, AMES.


Why does the 737NG EGT drop during take-off? I noticed that the EGT drops a bit when I hit TO/GA for take-off on a 737-800.

Above is takeoff engine data$^1$ and is indicative of the behavior you've mentioned. (FF is fuel flow and TLA is thrust lever angle.) The same behavior can be seen here as well:

A 737-800 takeoff video
An "EICAS cam" video for what I think is a 777
An Embraer E190-E2 video

(The exact timing may depend on how long the engines are left in the stabilization process.)

Note: The 737NG EGT sensors are at the T495 station in the low pressure turbine section. There are 9 thermocouple probes and their average is displayed.

The CFM56 employs variable stator vanes (VSV) in the compressor. In general those vanes close at low engine speed and open at high engine speed (shown below).

  Source: CFM56-5A manual

The specifics are proprietary, but plausible conclusions can be made. When the engines are stabilized for TO/GA, it could be the ECU (electronic control unit) opening the VSV to provide the ideal compressed air for faster engine acceleration (more air before the fuel would lower the EGT).

Note: The VSV is controlled by the hydromechanical unit (HMU), which receives input (torque motor current) from the ECU (CFM presentation, PDF page 16).

Of course if you have cause for concern, don't use the internet for flight, and check with your airline.

$^1$ Lion Air Max crash report (sadly the only public source of FDR data I can think of is accident reports).


What is the "yaw damper"? Some airplanes have a button for the "yaw damper."

What is the yaw damper?
When is it used?
Is it ever required for certification or operation?
How does it work?

The yaw damper is, in simplest terms, an "autopilot" for yaw. When engaged, it operates the rudder (or whatever yaw control method is available in exotic aircraft, like the B-2 flying wing).

Its primary goal is to counteract the typical Dutch roll aerodynamic mode of many aircraft. It also helps keep turns coordinated by automatically providing the necessary rudder inputs to avoid slipping/skidding in a  turn.

In normal aircraft the yaw damper is part of the automatic flight control system (AFCS) or "autopilot." It can usually be engaged on its own without the rest of the autopilot. On the other hand, most autopilots require the yaw damper to be engaged when the rest of the autopilot is engaged (you can have yaw damper without autopilot, but not autopilot without yaw damper).

For large / transport aircraft, the yaw damper is usually engaged throughout the entire flight profile except for takeoff and landing.

It is required equipment (link is to FAA certification regs but similar regs apply elsewhere) in many (most?) transport aircraft, which tend to suffer Dutch roll instability, but flights can sometimes still be made if the yaw damper is inoperable per the minimum equipment list (MEL), with restrictions. This depends on the exact aircraft type and any extra operator policies (company rules). Note that usually an inoperable yaw damper also precludes the use of the rest of the autopilot.

Modern digital yaw dampers are part of an integrated digital autopilot system. They use accelerometers and rate sensors to determine the aircraft's motion. It then runs the numbers through special algorithms to determine what rudder inputs need to be made in order to damp any Dutch roll and to coordinate a turn. It then provides those rudder commands to a servo or hydraulic system which operates the rudder.


Why RNAV SIDs and STARs are RNAV 1 instead of RNP 1? I am studying for my CFII check-ride and I was wondering to know why SIDs and STARs are not RNP 1 but RNAV 1?
Let's start with the following two definitions
RNP - Required Navigation Performance: It's a PBN navigation method/specification in which the airplane achieves an specified accuracy (RNP 1, RNP 2, etc) the a 95 % of the flight time. It has an onboard monitoring system that alerts the pilot when the integrity is loss. Examples of Equipments that are able to perform RNP 1, RNP2, etc are IFR GPS receivers with RAIM or WAAS (integrity monitor).
RNAV - Area Navigation: As we know, FAA uses RNAV in chart tittles only to determine Area Navigation. But RNAV it is also a PBN method/specification in which the airplane achieves an specified accuracy (RNAV 1, RNAV 2, etc) the a 95 % of the flight time. The only difference is that the aircraft won't alert the pilot when the integrity of the system is loss. I've never used an RNAV system without integrity monitor, I guess that DME/DME/IRU is wan of those. Is an IFR GPS with RAIM capability lost considered an RNAV system without integrity monitor?
The final and most important question is: On SIDs and STARs, Why is it not required to have a system that monitors the integrity of the equipment and alert the pilot if the accuracy can't be determined? Are pilots supposed to monitor the integrity of the systems by themselves? How?
Thanks
Edit
I found the following on AC 90-100A CHG2 8. RNAV SYSTEM APPROVAL PROCESS (b)(1)
"For procedures requiring GPS and/or aircraft approvals requiring GPS, if the navigation system
does not automatically alert the flightcrew of a loss of GPS, the operator must develop procedures to verify correct GPS operation"

First of all, an RNP 1 procedure requires a GPS/ GNSS. And as you have said, it requires an inbuilt navigation monitoring and an alerting system. On the other hand, an RNAV 1 procedure does not. In RNAV 1 you can get navigational aid from the IRS/ VOR/ DME or IRS/ DME/ DME.
The SIDs and STARs can either be RNAV 1 or RNP 1. RNAV 1 is the system introduced at the start of performance based navigation to cater for smaller air spaces (terminal area procedures) and it is a step towards changing over to RNP 1. Many countries these days require an aircraft with RNP 1 capability to fly their SIDs and STARs. They sometimes tend to name it unambiguously on the chart. Like a chart might state, RNAV 1 and then state that you require a GNSS. This essentially makes the procedure an RNP 1 procedure. Others state specifically that you need to be RNP 1 complaint. This means that you need to have a GPS and a monitoring and alerting system. This is mainly seen in China, where most of the airports require the aircraft to be able to fly RNP 1 procedures so that they can pack airplanes together, with minimal ATS surveillance. This is done to accommodate the ever increasing air traffic in the region.
It has been quite a while, since I have not been to Wuhan, China for obvious reasons. Wuhan airport is one those example airports which allow only aircraft that can fly RNP 1 for their SIDs and STARs.

I think the advantage of keeping the charts and procedures RNAV is that it allows operation of older aircraft, which does not comply with RNP operations. This is I believe quite important in a place like the United States where airlines still tend to operate older aircraft and has a big general aviation sector. In other places, airlines tend to have newer aircraft, which easily fits into the current navigation standards. This makes it easy for the regulators to change their procedures to RNP.
For the question regarding losing RAIM (Receiver autonomous integrity monitoring). If you lose RAIM, you probably cannot do a GPS/ RNAV (GNSS)/ RNP approach (same type of approach, just different names). But the aircraft can still be used for RNAV navigation, as RNAV does not require the monitoring and alerting.


Are airfoil profiles patented? If not, why? For something that takes so much research and can effect performance drastically, there seems to be no patents on airfoils.
Too simple in appearance to patent? They appear simple at first but the performance characteristics behind them are quite complex.
I have found patents describing 3D objects such as turbofan blades using a combination of airfoils, twist and sweep combined. There seems to be nothing showing or describing a 2D profile of a wing unless it's flaps.

There certainly are airfoils that are patented. Here is an example. Here is another airfoil by the famous aerodynamicist Richard Whitcomb. I think it is tricky in practice to obtain a patent in that you need to define the airfoil in a way that isn't so narrow as to be useless for protection. Just claiming a series of coordinates would provide very little protection as someone could make minor changes to avoid infringement.


What is this flange on the engine? Flying home from the Denver ComiCon, on a 737, I saw an angled flange on the engine. Could you describe its purpose?

Photos by CGCampbell licensed CC0

This is called a "strake" or "chine" (Aerodynamic fan cowl strake/chine, Nacelle strake/chine).
They allow the aircraft to generate more lift at lower speeds, which entails such positive consequences as lower stall speeds, lower landing speeds, lower take-off speeds and shorter runways.

Strakes should be used if the nacelles are mounted closely under the wing of the aircraft, see also Why don't all aircraft use/need nacelle chines?. Nacelles are usually mounted like that in order to

maximize the distance between the lower nacelle side and the runway, so that the engine/fan cowl/nacelle doesn't hit the ground during violent landings when the wings bend down, and in order to
minimize the risk for runway debris being sucked into the engine.
Source: Flugzeugtriebwerke, Bräunling Willy J.G., VDI-Buch, Springer Vieweg, 2015

From US Patent 20100176249: Engine Nacelle Of An Aircraft Comprising A Vortex Generator Arrangement:

  With an optimal arrangement and at high angles of attack, such vortex generators, which are known as nacelle strakes or chines, generate a powerful vortex that flows over the wing, where on a slat in front of said wing it delays airflow separation until the aircraft flies at greater angles of attack.

The idea dates back to 1971 (US Patent 3744745: Liftvanes):

  in operational conditions wherein high angles of attack are encountered, such as in landing or takeoff, the vanes oppose the strong upwash around the nacelle, reducing the flow separation on its upper areas, and providing a strong downwash marked by marginal trailing vortices

From R.S. Shevell. Aerodynamic Bugs: Can CFD spray them away? 1985

  DC-10 wind tunnel tests showed a significant loss in maximum lift
  coefficient in the flap deflected configurations, with landing slat
  extension, compared to predictions. This resulted in a stall speed
  increase of about 5 knots in the approach configuration. The initial
  wing stall occured behind the nacelles and forward of the inboard
  ailerons. The problem was traced by flow visualization techniques to the
  effects of the nacelle wake at high angles of attack and the absence of
  the slat in the vicinity of the nacelle pylons. The solution was
  developed in the NASA Ames Research Center 12 ft. pressurized tunnel and
  turned out to be a pair of strakes mounted forward on each side of the
  nacelles in planes about 45 degrees above the horizontal. The final
  strake shape was optimized in flight tests. The strakes are simply
  large vortex generators. The vortices mix the nacelle boundary layer air
  with the free stream and reduce the momentum loss in the wake. The
  vortices then pass just over the upper surface of the wing, continuing
  this mixing process. The counterrotating vortices also create a downwash
  over the wing region unprotected by the slat, further reducing the
  premature stall. The effect of the strakes is to reduce the required
  takeoff and landing field lengths by about 6%, a very large effect.


Do small helicopters like the R44 require an FAA type rating? From what I read in 14 CFR 61.31 it never mentions type rating requirements for rotorcraft or helicopters. I Googled online but most of the results showed up for Australia, Canada and the UK.

I am starting to believe that the US does not require a pilot to have a type rating for a Robinson R22 or R44 helicopter.

Am I correct that unless the FAA has made a type certificate for that helicopter it does not require a type rating? Would it just require a checkout from wherever you are going to rent?

SFAR 73 is Robinson R-22/R-44 Special Training and Experience Requirements and lists the specific training requirements for that model. Here's one relevant piece:

  (1) No person may act as pilot in command of a Robinson model R-22
  unless that person:

  (i) Has had at least 200 flight hours in helicopters, at least 50
  flight hours of which were in the Robinson R-22; or

  (ii) Has had at least 10 hours dual instruction in the Robinson R-22
  and has received an endorsement from a certified flight instructor
  authorized under paragraph (b)(5) of this section that the individual
  has been given the training required by this paragraph and is
  proficient to act as pilot in command of an R-22. Beginning 12
  calendar months after the date of the endorsement, the individual may
  not act as pilot in command unless the individual has completed a
  flight review in an R-22 within the preceding 12 calendar months and
  obtained an endorsement for that flight review. The dual instruction
  must include at least the following abnormal and emergency procedures
  flight training: [...]

SFAR 108 has similar requirements for operating the Mitsubishi MU-2B.

Finally, note that the type certificate is for the aircraft, and has nothing to do with whether an individual pilot is qualified to fly it or not.


Can an airline reject a passenger for being overweight? I have a Cessna 172S and despite having 4 seats in the cabin, I cannot take 3 more passengers besides myself as the pilot with a full tank of fuel due to safety in weight balance issues.  As the pilot, I'm 100 lbs overweight.  Hypothetically, we can imagine a situation where a small regional carrier using a turboprop can have only one seat left but the length chord from center of gravity for that seat may cause an unsafe weight balance for the aircraft loading if the passenger is very overweight.

In that case, if not other solution can be found, could the airline reject to passenger for the motive of their weight?

Yes.  If carriage of said person on a particular flight would cause the aircraft to be overloaded or outside of its CG envelope, the airline has full right to refuse them passage for safety reasons. It would be illegal under Part 121 and Part 135 to do otherwise.

Practically speaking though, most large commercial aircraft have such great payloads that this would not happen on a frequent basis.  Now the airlines may charge said person for an additional seat costs because of their size and girth.


Does the "bat wing" aircraft paint design have a proper name? I would like to do a web search for different planes that have utilised the "bat wing" paint application noticeable on the wings below?  What keywords should I search for?

Although aeroalias is correct that this is often associated with Gee Bees, I think a more 'generic' term is a scalloped paint scheme, e.g.:

American Champion paint options
C130 paint schemes
Model biplanes


Can someone provide details about airlines dividing crew into personality groups? In this answer about crew bidding/scheduling, it's mentioned that crews may be divided into groups based on personality.

What personality traits may be considered? How are people matched? Is this common around the industry?

I spoke to my friend at the one of the ME3 carriers. She tried to find any information regarding this matter but was not able to find it. However during your recruitment process you have to perform a personality test and based on this test you are placed in one of the total of 7 groups. During the scheduling they combine people from different groups so that there is a balanced and workable crew on board. Say that you're in group 5, then you will for example mostly work with people that are in group 1 and 3.
Questions on this personality test are like:

Would you rather (example: clean a room or work within a group)
Which statements best describes you? (leader, selfish, friendly, etc, etc)

These airlines are run on performance optimization and care less about human values.


What is the reason behind the colors used for different flight categories? In Skyvector, Foreflight and Aviation Weather Center the following colors are used for flight conditions:

LIFR = Magenta
IFR  = Red
MVFR = Blue
VFR = Green

In most contexts, red is used as the color for the most caution/hazard, but LIFR has lower weather conditions than IFR. Why use pink for LIFR?

Somebody may answer: because LIFR is a subcategory of IFR (or MVFR is a subcategory of VFR).  Are there any other IFR subcategories (other than LIFR) to justify branching off that category? It seems like a creating a subcategory branch should have at least two categories.

VFR and IFR existed first. LIFR and MVFR were added later. I don't have a source on why magenta was specifically chosen, but red couldn't be used for LIFR because it was already used for IFR and in aviation we like to avoid obsolescence whenever possible.

I haven't been able to dig up exact timeframes for the implementation of IFR (since VFR was the default.) Although the terms VFR and IFR appear in the history of the FAA in the 50's, some references such as FAA's historical perspective cite the piedmont mid-air of 1967 as the source of the modern culture surrounding ATC including IFR rule enforcement.

For more reading on how flight rules came to exist in the US, I recommend an article on gizmodo.


How to detect landing and takeoff using the value of GND field in ADS-B messages? How to understand that an aircraft is landing or taking off by analyzing MSG messages? According to this article we just need read GND field (22). I also heard that during landing the aircraft is sending MSG.2 with field 22 at 1.

I don't understand whether the aircraft is landing or taking off when the field is 1. It seems it just means the aircraft is on the ground, but there is no information about it's exact state.

How to actually detect that an aircraft is landing or taking off?

There is no field in any of the eight message types that indicates that an aircraft is in the process of either landing or taking off. Field 22, where it is transmitted, is a simple binary status: the aircraft is on the ground, or it is not. If you want to know what an aircraft is doing look at values for field 22 in successive messages. When the state changes you'll know that an aircraft has transitioned from ground to not-on-ground and has taken off (or vice versa)

Depending on how you define it, the actual period for which a 'taking off' status would be valid could be very short. I.e, just the duration of the take-off roll. Before that the aircraft is taxying and on-ground; after that it is flying. The same limitation is true for landing, but in reverse.


How many pilots are licensed in Hong Kong? Title says it all. I don't see this information online anywhere. A breakdown by PPL/CPL would be nice. I have a vague memory of someone telling me 300 but that seems a tad low for a city of 7.5 million.

I reached out to the Hong Kong Civil Aviation Department and asked this question. To my surprise, I got an answer back in less than 12 hours.

As of December 31, 2014, they report:

219 private pilots
951 commercial pilots
4007 ATPL holders
20 MCPL holders

For a total of 5197 pilots licensed in Hong Kong.


Is it possible for a civilian to use a VORTAC station? Suppose you have a Cessna 208 Grand Caravan Amphibian and you want to use VORTAC stations on military bases (or somewhere else). Is it possible? Is it legal?

Totally legal to tune it up & use it. If it is a VORTAC, it will work just like every other VORTAC out there. If it is a TACAN, you may be able to get DME from it, but you won”t get bearing from it without a TACAN receiver.

Many, perhaps most VOR’s out there are in fact VORTAC’s — the TACAN station is colocated with the VOR. It is possible to have a VOR-DME station, which gives a civillian user everything a VORTAC does, but no bearing info to TACAN-only military aircraft. And you can have a VOR station with no associated DME at all.

But you won’t find any rule prohibiting you from tuning up any of the above - doesn’t exist (at least in the U.S., nor anywhere else I’ve ever heard of). If the military wanted a NAVAID they could use that you couldn’t, they could put up a TACAN using a channel that civillian DME receivers can’t pair with (ex ch 16X “pairs” to 135.9 - not a frequency in the range civil VOR receivers can tune to) and not publish it. But realistically, they’d probably just use a GPS coordinate & call it good.

(Edit: as @UnrecognizedFallingObject mentioned, it is not the “Y” TACAN channels that conventional VOR receivers can’t pair with, but there are some channels you can’t get DME from using normal VOR tuning — see this chart.)

Flying over that navaid on a military base may entail issues with the airspace involved, but that is its own issue, unrelated to using or not using the navaid.


Does anyone know what this approach chart symbol is? Does anyone know what the little “shell” like symbol on the taxi diagram is, under the 2239? Also, what do the little “P”s stand for? One is bolded and the other is not.

The 'shell' and the two 'P's are marked with red arrows in this diagram:

http://155.178.201.160/d-tpp/1809/05475R30.PDF

I’ve scoured FAA guides trying to locate what it could be, but so far, no luck.

Any help is appreciated!

What you want is the Frontmatter to the Terminal Procedures Publication, and in particular the pages under "Approach Lighting System" -- these document all the various permutations of visual approach aids found in the US NAS.

As to the symbols you are specifically asking about -- the "shell" is the standard symbol for an ODALS (OmniDirectional Approach Lighting System) that consists of two steady burning lights at each side of the runway threshold and five sequenced flashers leading down the extended runway centerline for 1500'.  The two circled "P"s are also standard symbols, but for PAPI (Precision Approach Path Indicator) lights -- a set of four bicolor (red/white) lights that sit beside the runway and are aimed so that you can see if you're above, on, or below the glidepath based on the combination of red and white lights you see.

As to the symbols being reverse (not boldened)?  That means that those lights are hooked up to a PCL (Pilot Controlled Lighting) box that listens for sequences of microphone clicks on the airport control frequency (UNICOM/CTAF, or tower for a part-time towered airport) and turns on the lights hooked up to it for a set period of time when a suitable sequence is given by a pilot.


Does the pilot in command always sit on the left seat? Are there any rules (i.e. airline-specific) or regulations (laws) that state that the pilot in command (PIC) must sit on the left seat in commercial airliners?

This question specifically asks for rules concerning the PIC who is not neccessarily the highest ranking crew member (as I think that a check captain may sit in the right seat when checking a captain).

No, the PIC does not always sit in the left seat, and there's no regulations about it. Most airplanes are configured so that the primary pilot would sit on the left, however there are military trainers (the Slingsby Firefly comes to mind) which have this on the right so that the pilot has the throttle on the left and stick on the right as single seat military jets have. Helicopters have the pilot on the right, not the left.

In any case the PIC is not necessarily the handling pilot, instructors usually sit on the right and are often the pilot in command.


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

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

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

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

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


What is the purpose of the three small bumps on the switches for landing lights? What is the purpose of the three small bumps on the switches for landing lights and what is the history behind it? You'll see a similar design on Boeing, Airbus, and other aircraft.

Here is a picture of a 777 overhead panel:

The purpose is to make it distinguishable by touch or visual as explained in other answers and comments. And because generally, there are two main landing gear and a nose landing gear, it has been designed to be more like landing gears.

Edited:

There are two main questions about landing light switches in Aviation Regulation as it reads in FAR 23.1301 which is required to get AIRWORTHINESS COMPLIANCE certificate.

  Is the landing light switch located so as to be readily
  accessible to the pilot?

  Is the landing light switch adequately labeled as to operation
  and function performed?