What's parked in Mil Moscow helicopter plant? This answer has a photo of a Mil Mi-26 that I felt in love with, so I looked in Wikipedia and learned it's the largest production helicopter, second only to Mil V-12 that flew as a prototype.

In turn, Wikipedia's V-12 article gave a link to the exact position where one of the two V-12 produced is placed, so I opened Google Maps and I had a satellite photo of the V-12!

So far so good, but when I zoomed out a little I saw many other helicopters parked around, all clearly helicopters except a cigar shaped beast, with winglets apparently too small for an airplane, in the upper right corner of the screen dump below, marked with an arrow... Remarkably I cannot see the shadows of the blades on the ground.

Could you please identify that object?

Looks like a Mil Mi-6 with the rotor removed (like the adjacent two to the right). Here is the 3-view drawing overlaid:

(Google Earth @ 55°40'04.61" N  37°56'07.62" E)

The tail boom appears to be thicker than it is due to the angle, it'll make sense by taking the satellite's perspective. Note the fatter bottom:

Google Maps measurement; actual aircraft length is 33.18 m (108 ft 10 in).


Why is the empennage design of this Lockheed 1049E so complicated? Photo.

What is the reason for making the empennage of this Lockheed L-1049E Super Constellation's design look so complicated with two vertical horizontal stabilizers? In my understanding, the more components installed, the more the weight of the airplane will be, and as a result will put more load on the engines, especially if there will be more actuators required. Do all the horizontal stabilizers have controllable surfaces? What is the reason for making the horizontal and the vertical cross each other, and not attaching them at their tips (marked with yellow and green circle)?

Edit: I corrected the question on the body from with two additional horizontal stabilizers? to become with two additional vertical stabilizers? as supposed to be as I marked in the picture.

Complicated is a matter of opinion and I wont address that specifically since its somewhat subjective. But the core of the question is "why did the L-1049E have 3 tails" which is a legitimate question for this site.

The design was to allow the aircraft to fit in hangars of the time

  A sleek fuselage, something like an elongated fish with smooth curves,
  featuring a circular cross-section, a snub nose, and a triple-fin
  tail. Triple tailfins were selected because a single tailfin would
  have been too tall to fit into typical hangars.

The L-1049E had tricycle style gear that was quite tall (for the time) and a standard single tail would have made the aircraft too large to fit into the hangars that most fields had.

The above link also discusses that for a particular Military version ("WV-1") of the aircraft the lower section of the tails were extended to compensate for a radome being mounted on the top. This came along only a year into the design and the subsequent builds may have been a hold over.

Weight as a result of the added rudders would not have been as much as you may expect since they were traditional fabric covered style surfaces


Does EASA require airliners to be fitted with autopilots? For EASA OPS requirements, must an airline transport airplane be fitted with an autopilot system?

Indeed EASA requires "autopilot" but they don't state it directly like "every airliner flying in the European airspace must be autopilot equipped". They require it indirectly.
When I first read your post I immediately thought of RVSM. I recall talking to an ATCO (retired now) about automation on board, and he told me that without autopilot you cannot fly in RVSM airspace.
So I had a look in skybrary concerning RVSM and they did the dirty job for us. They mention all 3 EASA regulations  IR-OPS SPA.RVSM.100 and SPA.RVSM.110, EU-OPS 1.241, EU-OPS 1.872 and they have quoted the interesting parts:

Regulatory Requirements[...]
An operator shall ensure that aeroplanes operated in RVSM airspace are equipped with:[...]
An automatic altitude control system

Emphasis is mine.
There might be other regulations requiring other automatic flight components but I am not aware of them although a quick look in the documents reveals references to auto-land systems as well so these documents cover more than RVSM.
The summary is that EASA does not simply specify "you need autopilot if you fly an airliner" but they go into detail, of what they require and for what reason.

Acronyms
RVSM Reduced Vertical Separation Minima
ATCO Air Traffic Control Officer


How to get an accurate time of arrival to the en-route alternate airport during flight planning? I was thinking about accurate criteria of selecting en-route alternate (ERA) weather from ground (planning stage) especially for ERA 3% contingency flight plan.
As we all know we should care about one hour before to one hour after of arrival time into destination hence the main question here how we should know what is the estimate time of arrival into destination i.e. 1400Z.
Personally what I am doing as a airline pilot is crosschecking the nearest waypoint to that "ERA" thence I can tell inaccurate estimate.
Is there any idea how we can get accurate estimate of en-route destination during planning stage (on ground) that can give us exact ETA of destination?

This is very much like the information mandated for EDTO/ETOPS.
Computerised flight planning systems should have the ability to calculate the ETP, equal time  point (aka CP) based upon ERA/ERAs selected. If 2 ERA are required due to the length of flight, depending on the geographical disposition of the ERA you'd get an ETP for each pair, ie ETP1 for DEP Stn/ERA1, then ETP2 for ERA1/ERA2, then ETP3 for ERA2/DEST Stn.
The earliest ETA for ERA1 would be a diversion from ETP1 and the latest would be from ETP2 and you would need to subtract/add the 1 hr buffer.
And so on . . .


RC airplane required engine power I'm going through the process of designing an RC airplane. I know that probably most calculations on scale models might be non-precise ones, but I'm trying to do it as correct as possible (it's a school project). I was trying to check how much shaft power I would need for the aircraft, so I did an excel table and used some pessimist assumptions in order to check if my 46 cubic inches, which deliveries 1,63HP, had enough power.
These are the aircraft parameters:
Chord= 0,3m
Wingspan = 1,8m
Wing Area= 0,54m2
AR=6
W= 3,7kg (assumed)
Cp = 0,048 (assumed)
Propeller efficiency= 0,6 (assumed)
Air density= 1,225 kg/m3 (Sea Level - where I intend to operate)
I used W = 1/2  *  rho  *  S  *  V2  * CL to identify the required CL for level flight at any given airspeed, then   Cdi = CL2 / (pi * AR *  e)  and using Ri =  1/2  * rho  *  S  *  V2  *  Cdi and
Ri =  1/2  * rho  *  S  *  V2  *  Cdi to find out both resistances I summed them up and multiply them by speed to get power, then I divided that power by propeller efficiency to get the needed shaft power.
For my surprise, the maximum speed that I could achieve with that 1,63HP it's between 39 and 40 m/s or 144km/h (89,4775 MPH), it seems like a lot.
Because of these results, I decided to contact a friend who is into RC Planes, he told me that that engine was actually too little for a 1,8m wingspan plane, it looks like I'm doing something wrong, but I don't know what. L/Ds actually make sense.
This is the link for the excel file

Resistance is a term used in politics and electric circuits. We here talk of drag.
Your induced drag equation uses speed where the lift coefficient belongs:
$$c_{Di} = \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$$
What is missing now is the zero-lift drag which is the dominant contributor to overall drag at high speed. From your top speed result this seems to be
$$c_{D0}=\frac{2\cdot P\cdot\eta_{Prop}}{v_{max}^3\cdot S_{ref}\cdot\rho} = 0.040$$
assuming a propeller efficiency of 70% and neglecting induced drag. That figure is not unreasonable. Is the landing gear retractable?
Now we can write for the total drag as a function of speed:
$$D = \frac{\rho}{2}\cdot v^2\cdot S_{ref}\cdot\left(c_{D0}+\frac{c_L^2}{\pi\cdot AR\cdot\epsilon}\right)$$
$$D = \frac{\rho}{2}\cdot v^2\cdot S_{ref}\cdot c_{D0} + \frac{2\cdot (m\cdot g)^2}{\rho\cdot v^2\cdot S_{ref}\cdot\pi\cdot AR\cdot\epsilon}$$
When sizing an engine the most reasonable parameter is power loading: How many Kilowatts are available per square meter of wing area and per Kilogram of airplane mass. Wingspan is a poor basis for comparison, since a larger span at the same area means a higher aspect ratio and lower demands for power. When using your figures, your power loading is 1.21 kW for 0.54 m² or 2.25 kW per m² or 0.608 kW per kg. Compare these figures to similar model aircraft to see whether you are on the right track.
Nomenclature:
$P\;\;\;\;\;\;\:$engine power
$v\;\;\;\;\;\;\;$flight speed
$\rho\;\;\;\;\;\;\;$air density
$c_{Di}\;\;\;\;\;$induced drag coefficient
$c_{D0}\;\;\;\;\:$zero lift drag coefficient
$S_{ref}\;\;\;$reference area
$AR\;\;\;\;$aspect ratio (= 6 in your case)
$\epsilon\;\;\;\;\;\;\;$span efficiency, use 0.85 for a rectangular wing
$m\;\;\;\;\;\;$airplane mass
$g\;\;\;\;\;\;\:$gravitational acceleration


Do Federal regulations compel airlines to avoid schedule disruptions? I understand that airlines may classify certain passengers as "must-ride" and, at least as a matter of policy, bump regular passengers in order to accommodate "must-ride" passengers.  I also understand that it is common for airlines to classify crews riding deadhead as "must-ride" based upon whether or not they are urgently needed at their destination.

I was recently informed that federal regulations actually compel airlines to do everything they can to ensure that crew members successfully make it to their destination in order to crew a scheduled flight, but I was not given the specific regulation that applies.

Is there a DOT or FAA regulation that requires airlines to bump standard passengers in order to transport "must-fly" crew members?  Is "must-fly" status just a matter of airline policy, or is it some FAA- or DOT-defined status that airlines make use of?

If not, is there a more general regulation that compels airlines to avoid cascading cancellations at all costs wherever possible?

The Department of Transportation has A Consumer Guide to Air Travel that discusses passenger rights regarding delayed and cancelled flights. Some key points:

Airlines don't guarantee their schedules, and you should realize this when planning your trip.
Overbooking is not illegal, and most airlines overbook their scheduled flights to a certain extent in order to compensate for "no-shows."
Airlines set their own "boarding priorities" -- the order in which they will bump different categories of passengers in an oversale situation.
DOT requires each airline to give all passengers who are bumped involuntarily a written statement describing their rights and explaining how the carrier decides who gets on an oversold flight and who doesn't.

There airline is required to provide various sorts of compensation if they bump you involuntarily and can't get you there within 1 hour of the original flight. This depends on how late you will arrive and what kind of ticket you have.
There is no rule that says airline employees must fly instead of customers, but each airline has their own Contract of Carriage that describes their rules. You can read United's here as an example. Rule 25 describes the process for denied boarding:

If there are not enough volunteers, other Passengers may be denied boarding involuntarily in accordance with UA’s boarding priority:
The priority of all other confirmed passengers may be determined based on a passenger’s fare class, itinerary, status of frequent flyer program membership, and the time in which the passenger presents him/herself for check-in without advanced seat assignment.

Of course IANAL but the way I read it, they "may" use any of those methods but they are free to deny boarding as they wish. Nothing stops them from choosing to bump customers before employees. Delaying or canceling a later flight because they bumped the employees would be more expensive than paying a few customers to be bumped involuntarily. But bumping employees may be less expensive than a PR fiasco.
There is also a program called Essential Air Service, where the DOT subsidizes airline service to smaller markets. Airlines bid to provide this service under certain conditions. Although I wouldn't say they are "compelled" to provide that service, if they don't meet the conditions, which could include not completing enough of the scheduled flights, they may not receive the subsidy.


Where can I get aviation weather information? Where can I get weather information (preferably something similar to what pilots get) for a non-pilot?

I usually use flightradar24 for flight tracking, would love to see weather data as well.

NOAA collects METARs (current weather) from all over the world and publishes them at http://weather.noaa.gov/pub/data/observations/metar/stations/.

They also collect TAFs (forecasts) and publish them at http://weather.noaa.gov/pub/data/forecasts/taf/stations/.

These reports are what the information told to pilots by controllers or broadcast in ATIS is based on, written in shorthand format designed for efficient transmission over teletype. If you look around the directory structure, there are also decoded versions.

The above links are complete, but intended more for machine consumption, being plain text files. You'll find many other sources that look more like normal web pages if you google for some airport code and “METAR” or “TAF”, but different parts of the world will be available at different places. The above links are most comprehensive source.


Is Cessna 150 with incorrectly marked ASI airworthy? I've looked a bit at the CFRs trying to determine this for sure, but haven't found a clear answer..
One of the Cessna 150s that I rent from the local FBO had it's airspeed indicator swapped out four or five months ago..  the new indicator, in addition to having the low end of the speed range super clumped together so it's difficult to see the accurate reading near the stall speed, is clearly MARKED incorrectly for the airplane that it's in.  The most obvious example is the white arc -- on the ASI that they installed, the top of the white arc is at 80mph, when this Cessna 150M should have the top of the white arc up closer to 93mph.
I know it's not a super huge difference, and I feel that I can fly the airplane safely, but it made me wonder whether it's airworthy with such an obviously incorrectly marked ASI in it.
Thanks!

Take a look at the equipment list of the Cessna 150.  There are part numbers for every piece of equipment installed.  If the part numbers do not match, then the airplane does not comply with its type certificate data sheet and is not airworthy.  Take a look in the maintenance manuals and find the part numbers.  If the rental FBO refuses to let you see those manuals find a different FBO to rent from.
Unfortunately, that is not the whole story.  There are also other ways for this to be an airworthy airplane:

PMA part.  If the new airspeed indicator has been approved as a direct replacement parts manufactured approved part, it can go in along with the equipment necessary to make it work.  I doubt this is the case as the part would have to be FAA approved for that airplane.  The most common application of a PMA approved part is the installation of LED bulbs for incandescent bulbs.

STC.  The airplane has a supplemental type certificate that modifies the airplane in such a way the new airspeed indicator markings are required for the STC.


In a tailwheel plane, which design elements affect the propensity for a ground loop? In comparisons between conventional gear vs. tricycle gear aircraft, it is generally explained that the CG location relative to the mains is a necessary condition for ground-looping. But there's very little more explanation than that.
I'd like to know more about the design traits which affect the propensity for a ground-loop. The following is an uninformed list of some things which I could see affecting a taildragger's ground handling, but I wouldn't hazard a guess as to relative importance.

CG location
Gear width
Gear shape
Gear springiness
Tire pressure
Tread traction

CG Fore/Aft Location
The further forward the main wheels are in front of the CG, the greater the propensity for ground looping.
Main wheel separation
The closer together the main wheels, the greater the propensity for ground looping.
Main wheel Toe-in and Toe-out
The following text and images come from the book "Landing Gear Design For Light Aircraft" by Ladislao Pazmany, obtained on-line via this web page on www.vincesrocket.com:

The "toe-in" and "toe-out" of a wheel is measured either in degrees or
in inches as shown in Figure 3-9.

How the "toe-in" or "toe-out" affects the directional stability and
control of an aircraft is a controversial subject.  The author
consulted with a number of aeronautical engineers and landing gear
experts.  The answers were mixed.  Some indicated that with "toed-out"
wheels as shown in Fig 3-10, the wheel on the outside of the turn
tends to run straight and counteract the ground loop.

Other opinions were that the "toed-in" wheels result in more drag (due
to skidding) in the outside wheel than in the inside wheel, therefore
counteract the ground loop as shown in Fig 3-11.

The recommendations in some Service Manuals are that a very small
amount of "Toe-in" (0 to 1/8 inch) measured at empty weight, is
desirable.  Essentially the wheels should run straight (zero toe-in)
at normal operating weight.  The PL-4A (Figure 1-11) designed by the
author has 0 degree toe angle and exhibits excellent ground handling.
Any tendency to ground loop initiation is easily countered with the
rudder and steerable tail wheel.  The same comments apply to tricycle
gear airplanes.

Here's a post from an on-line discussion forum for rc airplanes where the author describes a particular plane where the landing gear can be quickly removed and re-attached to convert toe-in to toe-out or vice versa.  The author notes that any toe-out seems to greatly increase the difficulty of keeping the aircraft going straight when the aircraft is rolling at high speed on the main wheels with the tail in the air.
The entire thread from which the above post was taken may be of interest-- the opening question is very similar to the question here: "What design aspects affect ground handling?"
Here's another post from another related thread on the same forum where the author-- a very experienced builder and flier of rc planes-- advocates some toe-in.
Camber
Camber is a significant factor.  If the bottoms of the main wheels are closer together than the tops, the wheels have positive camber.  If the tops of the wheels are closer together than the bottoms (like on a Me-109 or Spitfire), the wheels have negative camber.  Note that if a tailwheel aircraft has zero toe-in but positive camber when it is an a fuselage-level attitude, then the camber will automatically create toe-in when the tailwheel is on the ground.  If a tailwheel aircraft has zero toe-in but negative camber when it is in a fuselage-level attitude, then the camber will automatically create toe-out when the tailwheel is on the ground.  This may be part of the reason why negative camber has generally been found to contribute to an increased propensity towards ground looping, and positive camber has generally found to contribute to a decreased propensity toward ground looping.  Note also that when a ground loop begins and the "leading" or outside wheel starts to get more heavily loaded than the "trailing" or inside wheel as the plane starts to tip over toward the outside wingtip, negative camber will make the "leading wheel" tend to "dig in" or experience an increase in traction, exacerbating the process, while positive camber will tend to reduce this tendency.
Tire traction
Tailwheel aircraft show much less propensity towards ground-looping when landing on grass or wet pavement, than when landing on dry pavement.  This might seem to suggest that any tread on the tires of the main wheels--or at any circumferential grooves -- should increase an aircraft's propensity for ground looping, by increasing traction.  However this related ASE answer indicates that tread or circumferential grooves don't actually increase a tire's grip on dry pavement.
It would seem that anything that increases a main wheel's "contact patch" -- which would include decreasing the tire pressure-- would increase the ground-looping tendency on dry pavement.
CG height
A high CG location increases an aircraft's tendency to tip over and drag the outside wingtip during a ground loop.  Even before the wingtip touches, any tipping will load up the "leading" wheel and unload the "trailing" wheel, which will exacerbate the developing ground loop.
Fuselage length
An aircraft with a relatively short fuselage is called "short-coupled", and will experience a greater propensity for ground-looping than an aircraft with a relatively long fuselage.1  If the mass of the aircraft is concentrated near the CG so that the moment of rotational inertia is low, the aircraft will have less tendency to ground loop than if the mass of the aircraft is distributed far from the CG.
Annex
Here is a PDF from a course on landing gear design.  Note however that it doesn't go into a great deal of detail.  Toe-in/out and camber are not discussed.
Footnotes:

This sentence naturally begs the question-- exactly how might we quantify how "short-coupled" an aircraft is?  Probably not by comparing the fuselage length to the width of the landing gear tread, as this would seem to imply that increasing the distance between the main wheels is not helpful.  There may be some room for further refinement of this part of this answer--


How to verify the runway numbers in a systematic way given the high workload during landing? I have never had a runway number verification on my checklists because normally the landing checklist is completed and stowed by the time I am on short final and can clearly see the numbers.

However, after seeing that Harrison Ford just landed on a taxiway and I know commercial jets have done the same thing from time to time, I am considering a checklist item. One issue is not just the taxiways, a lot of larger airports and big airfields like Oshkosh have multiple parallel runways with right/left designations so it can get pretty confusing. The whole problem is that normally when I am on final and swooping in everything is happening fast and I do not have available bandwidth to be looking at a checklist, I have to be laser focused on making the landing and watching for traffic.

Any suggestions how to verify the runway in a systematic way given the constraints?

There are a few common (?) techniques you could use, although how you work them into your actual checklists is up to you. Here are some that I've been taught, there are probably more:

Tune the localizer and/or load an approach

Pros: reliable and accurate (if you set the avionics up right) because it gives you guidance for a specific runway
Cons: can lead to fixation on instruments when you should be looking outside; not every runway has an approach; your aircraft may not have the necessary avionics; may be awkward or distracting to set up and verify

Set the heading bug to runway heading

Pros: many pilots do this for takeoff, so it's a familiar check; works for any runway; convenient if you go around and are told to "fly runway heading"
Cons: doesn't uniquely identify a parallel runway

Write the runway number on your kneeboard

Pros: simple; easy to glance down at quickly
Cons: none that I can think of, unless you don't have a kneeboard

Or use all three techniques together, of course.

ATC could still change your landing clearance, or something else could force a change of plan, but stuff happens and you just have to deal with it. Personally I like the localizer/approach method at night and/or at an unfamiliar airport, otherwise I'll just write down the runway number on my kneeboard.


What should I do after failing the oral portion of my private pilot check ride? What steps should I take after failing the oral portion of the check ride for my PPL?

AOPA has a great article about this, and it basically says:

Since you failed the oral, more studying is probably in order.
You will need to receive training in the area(s) of the checkride that you failed from a flight instructor.
Once the flight instructor feels that you are proficient and able to pass the checkride, they will sign your logbook so that you may take it again.
Schedule your checkride again.  If you take it within 60 days, you will only need to test on the areas that you failed.  After 60 days you have to take the entire checkride over again.
Take your Notice of Disapproval (8060-5) with you to the checkride (you didn't burn it did you??)

Like the article says, it isn't the end of the world!  About 20% of first time applicants fail their checkride, but all you have to do is use it as a learning experience and let it make you an even better pilot.

If you have questions about specific subjects, you can also ask questions here and we will be happy to help you out!


Which Airbus models have exterior LED lights? (Taxi, Landing, Rotating Beacon) I know that the Boeing 737 MAX has LED'S. Which Airbus models also have LED external lighting?

The A320NEO has full LED lighting. Check out the below link.
http://utcaerospacesystems.com/cap/systems/Interiors%20Documents/Lighting%20Systems/06%20Anti-Collision%20Lights/06_0010%20LED%20Anti-Collision%20Lighting%20System%20A320.pdf


Why do many GA aircraft not have a "Both" fuel selector? I've been trying to rack my brain around this and asked a few CFI's who couldn't give me more than "because that is how it was done", but a good number of GA aircraft save for Cessna and maybe a few others only have a Left/Right fuel selector:

Image Credit: Make Time For Flying Blogspot

To me, as an engineer, it makes great sense to have a Left/Right/Both selector such as found in most Cessna's. This lets the pilot focus on flying the aircraft rather than having to switch tanks every 30 minutes to balance fuel out. A Left/Right/Both selector isn't sigificantly more complicated than a Left/Right selector, so that leaves me wondering...

Why do GA manufacturers opt to use just a Left/Right selector valve given that a majority of GA accidents are fuel related and off-airport landings with fuel in a tank is still relatively common? Is there a safety issue I'm not seeing?

I understand that even with a "Both" selection, fuel may not drain from both tanks equally, but you can always switch to the fuller tank for a little while then back to both in that case.

A quote from the book of regulations, Chapter 14, part 23, verse 951(b):

(b) Each fuel system must be arranged so that—
    (1) No fuel pump can draw fuel from more than one tank at a time; or
    (2) There are means to prevent introducing air into the system.

On a high wing aircraft satisfying #2 on that list is pretty easy: If you connect both tanks to the "top" of the fuel selector as in a Cessna 172 or similar then as long as you have liquid in at least one tank gravity will ensure there will be liquid at the top of the fuel selector to feed through into the engine:

The design of the system provides a passive "means to prevent introducing air" because gravity is always trying to pull fuel downward out of the wings and to the fuel selector.

On a low-wing aircraft like the Piper in your picture we don't have gravity to help us: There's no natural "head pressure" at the fuel selector (or at least much less than in a high-wing with the tanks mounted well above the valve), so we're relying on the fuel pump to draw fuel through the system.
This means we can no longer guarantee item #2 above: If the fuel selector were in the "Both" position and one tank ran dry the fuel pump is going to happily try to suck air through the line from the empty tank, and that could cause the engine to quit.

It's possible to guarantee item #2 in a low-wing fuel system using float valves that seal the tank outlets when the fuel is below a certain level - an active means to prevent introducing air into the system - but that adds complexity and weight.
Since the aircraft already needs to have a fuel selector valve anyway it's easier to just design the valve in such a way to satisfy item #1 on the list: Make sure the fuel pump can only draw from one tank at a time - i.e. "Don't provide a "Both" position on a low-wing aircraft."


If there is a misprint on an instrument plate, is a pilot required to comply with it? This is a snippet from the KESC RNAV 36 approach.  It's a real procedure, I didn't photoshop it except to add highlighting.

Let's say I was in the position that the blue aircraft is in (roughly 10 miles from WOKOL bearing approximately 320), and I had been cleared to WOKOL for the RNAV 36. I am assuming ATC did not explicitly tell me to do a procedure turn.

What am I supposed to do when I get to WOKOL?  The plate says NoPT, which is obviously a mistake.  Do I still fly the course reversal?  Do I whip into a 150 degree left turn over WOKOL as illustrated?

Here are some relevant passages from the AIM:

AIM 5-4-9:

  The procedure turn or hold-in-lieu-of-PT is a required maneuver when it is depicted on the approach chart, unless cleared by ATC for a straight-in approach. Additionally, the procedure turn or hold-in-lieu-of-PT is not permitted when the symbol “No PT” is depicted on the initial segment being used, when a RADAR VECTOR to the final approach course is provided, or when conducting a timed approach from a holding fix.

AIM 5-4-5 (D. 2. b.)

  The published procedure will be annotated to indicate when the course
  reversal is not necessary when flying within a particular TAA area;
  e.g., “NoPT.” Otherwise, the pilot is expected to execute the course
  reversal under the provisions of 14 CFR Section 91.175. The pilot
  may elect to use the course reversal pattern when it is not required by the procedure, but must inform air traffic control and
  receive clearance to do so.

If an instrument plate contains errors, am I still required to comply with them?

The first thing that you should do is check the NOTAM's for the airport (which of course, you should do before you leave on your flight).  Very often, these types of errors have been discovered by someone else and the FAA will have issued a NOTAM to let everyone know.  In this case there is no NOTAM, so we would have had no reason to suspect an issue before we took off.

The main point has already been made.  If you are airborne and there is any reason to suspect that something is wrong, ask ATC for clarification and move on.

If I encountered this situation and couldn't ask for clarification (ie. lost communication) then I would simply select a different approach and fly it.

For the record, the Jeppesen chart has it coded correctly:

Now, aside from the operational considerations, it is very important to notify the FAA when you find discrepancies like this so that they can be fixed.  Here is a quote from the Aeronautical Chart User's Guide:

  REPORTING CHART DISCREPANCIES

  Your experience as a pilot is valuable
  and your feedback is  important. We make every effort to display
  accurate information  on all FAA charts and publications, so we
  appreciate your input.  Please notify us concerning any requests for
  changes, or potential  discrepancies you see while using our charts
  and related products.

  FAA, AeroNav Products
  SSMC4 Sta. 4503
  1305 East-West Highway
  Silver Spring, MD 20910-3281

  Telephone Toll-Free 1-800-626-3677
  E-mail: 9-AMC-Aerochart@faa.gov

  Mark the chart you are using with the suggested
  changes and  include an explanation of the discrepancy. Mail this
  corrected  chart to the address above and we will send you a
  replacement  right away. Suggestions concerning this guide are also
  welcome.

For the record, I have already emailed the plate with the suggested changes to the email address above (on 24 DEC 2013), and hopefully a NOTAM will be issued soon and an amended approach procedure will follow sometime after.

Update (09 JAN 2014)

I received the following response from the FAA:

  Dear Louis:

  Thank you for reporting the problem

  ...

  Control Number 18335 has been assigned to this issue for tracking
  purposes.  This concern has been closed with the following Response:

  Thank You for your inquiry. A P-NOTAM is being assigned to correct the discrepancy.

  Regards,

Note that the NOTAM hasn't been issued as of yet.

Update 2 (17 JAN 2014)

New NOTAM issued to address the error on the instrument approach procedure:

!FDC 4/3036 ESC IAP DELTA COUNTY, ESCANABA, MI.
   RNAV (GPS) RWY 36, ORIG...
     CHANGE TAA TO READ FROM 274/30 CW 094/30 (NOPT) TO WOKOL
     (IF/IAF) AND FROM 094/30 CW 274/30 TO WOKOL (IF/IAF).
   THIS IS RNAV (GPS) RWY 36, ORIG-A.
   1401171859-PERM

Update 3 (06 MAR 2014):

New, corrected chart issued and the NOTAM was cancelled the next day.


What methods exist to detect airframe icing, and how do they work? What are the primary methods used to detect ice on an airframe, and how do they work on at least a high level?

There are a few ways to sense ice on an airframe. The DOT has a document here that outlines the various types of sensors.

First and foremost planes have ice lights that project onto the wings so they can be visually inspected.

There are completely optical sensors that use a variety of methods to detect ice.

There are also some electro mechanical devices, here are a few examples, the rest are outlined in the DOT document.

  Penny and Giles

  The Penny and Giles system uses a probe type sensor that measures ice
  buildup in terms of Liquid Water Content (LWC). This system was
  designed specifically for use on helicopters and is available for all
  turbine-powered helicopters.

  Rosemount

  The sensing probe is driven magnetostrictively to vibrate at its
  resonant frequency of 40,000 Hz. As the ice detector enters an icing
  environment, ice collects on the sensing probe. The added mass of the
  accreted ice causes the frequency of the sensing probe to decrease in
  accordance with the laws of classical mechanics.

  Sunstrand

  The Sunstrand system uses a mounted probe with a sensing surface
  facing the airstream. Beta particles are released from a Strontium 90
  Radiation Source and are collimated by a specially shaped window in
  the probe housing. These particles pass across the sensing surface to
  a Geiger-Muller tube. High voltage is applied to the Geiger-Muller
  tube to enable it to detect the radiation emitted by the Strontium 90
  source. Ice accretion on the probe decreases the beta particles
  detected by the tube. When the particle count drops below a pre-set
  level, a pulse rate discriminating amplifier energizes an icing signal
  visible to the flight crew. At this time a heater inside the probe is
  activated, the ice is removed from the probe, and the probe is ready
  to begin another icing cycle.

Some of these will work in a static situation while others may require the passage from a non icing environment to an icing situation.


Who decides an aircraft's maintenance schedule? I've found a 737 maintenance planning data document produced by Boeing, which gives a suggested schedule on page 6.

I've also found a British Airways Fact Book document, which on the last page gives a schedule.

So who decides how often an aircraft and its individual components should be inspected? Is it the manufacturer, the airline, or somebody else? Is there a set standard or does this differ between manufacturers/airlines/countries?

The manufacturer lists all maintenance that should be done, and when. This is the first document you found, from Boeing. Some of this maintenance may be required, other things might be recommended.

The operator can use that plan, while following maintenance laws (e.g. the required annual inspection). Or, they can submit a new rolling maintenance plan to their National Aviation Authority (e.g. FAA) for approval, which is usually done to prevent large downtime events for the aircraft. (This "rolling inspection" is done so that all of the necessary things are inspected at the proper intervals, but not all at the same time.)

There's a bit more, too: the Aviation Authorities can create Airworthiness Directives that can add additional required maintenance that must be done within certain limits (usually hourly, but can be situation dependent) for the aircraft to be airworthy.


Why are the aerodynamic characteristics of a finite wing different from the properties of its airfoil section? Why are the aerodynamic characteristics of a finite wing different from the properties of its airfoil section?

Because the wing is finite, while the airfoil is assumed to stretch out sideways indefinitely. The consequence is that on a wing you get spanwise flow outside of the plane of symmetry, while on the airfoil all flow speeds are in the airfoil's plane only.

Spanwise flow is caused by the pressure difference between lower and upper side which can equalise around the wingtips. This lets the pressure difference diminish towards the tips and especially in the rear part of the wingtips. The consequences are:

Lift is smaller on a "real" wing relative to a wing of the same airfoil with no such sideways flow.
The center of pressure of a "real" wing is ahead of the one of the airfoil.
On a swept wing the air transverses the surface differently than it transverses the airfoil. Basically, a sideways speed component is added to the speed around the airfoil.


What are the criteria for conceptual design of thrust reverser in the use of braking? I'm doing a project: Study of aircraft braking and pre-sizing of associated subsystems. We tried to find criteria for the reverser in the braking phase. I read FAR 25, but I did not find it.
Is there a criterion such as how many percent of the braking force must be applied by the reverser in certification documents?

As @John's answer alluded to, the rules for actual landing distance (25.125) and the accelerate-stop distance on dry runway (25.109) effectively prevent a manufacturer from taking credit for thrust reverser (T/R) when demonstrating/calculating for these distances. However, 25.109 does allow a manufacturer to take credit for T/R when dealing with a wet runway. This means that having a (good) T/R gives an operator more flexibility when dealing with adverse weather conditions, and this translates to more money saved (vs sitting on the tarmac).

Therefore, just like any other performance numbers, the performance of T/R is subject to market objectives. There is no regulatory requirement on how powerful the T/R has to be at max reverse.

That being said, this NASA memo has some helpful information on why airlines want thrust reverser at all. The following two graphs are cited from this source, which outline the percentage of work done by the respective braking systems for a typical jetliner on dry and wet runways. You can perhaps back-calculate the thrust of T/R from your design point:

Other factors to consider for design:

Foreign object debris ingestion from T/R deployment, especially at lower speed
Compressor stall from hot reversed gas, especially at low speed
Inadvertent deployment of thrust reverser in-flight. For most airplanes, this would be catastrophic.
Controllability in single T/R deployment on ground
For rear mounted engines, aerodynamic interference with rudder effectiveness


During a takeoff emergency, is it safer to abort or continue the takeoff if either can be done within the available runway? In a multi-engine airplane, if an engine failure occurs at the exact moment that a decision needs to be made to reject or continue the takeoff, and there is plenty of runway available to do either, which one is statistically safer?

A more technical way to ask the same question would be:  When there is sufficient runway available, is it better to artificially increase $V_1$ (via an assumed temperature takeoff or similar approved procedure) in order to stay on the runway longer in case an abort is required, or would it be better to leave $V_1$ at the lower speed and take any problems into the air?

In my experience, admittedly dated (retired 1999) whether it's 'better' or not didn't enter into the consideration. A reduced-power assumed-temperature was always used (unless there was something that prohibited it) because of the cost factor, and the power reduction used was always such that there was the proper amount of runway but not 'plenty' of runway. There was a maximum amount of reduction above which you could not legally go, but that was rarely used in my experience.

All that said, it's the captain's airplane. While I was a 747 f.o., I occasionally saw captains use less than the power reduction called for. More often, but still not a lot, I saw captains simply call for a max power takeoff rather fussing with adjusting the reduced power. Max power takeoffs were always entered into the aircraft maintenance log because it was required to do one every so often. I forget the exact requirement..

When I was a captain, I almost always observed the recommended reduced power. Twice doing this it became a closer thing than I would have liked. The first time was on the reef runway at Honolulu. We were over 800,000 lbs, it was my leg, and we lifted off at the very end. I rotated a couple of knots or so early because the end seemed to be getting very close. I thought a lot about that takeoff and discussed it with a number of people. My view, and I think the consensus view was: beware of high-humidity reduced power takeoffs. Humid air is less dense than dry air, but the performance charts (at least the ones we used) didn't take that into account.

A year or so later at Dhahran, Saudi Arabia, we were bringing a full load of troops back from Desert Storm. Reduced power was called for, the humidity was very high, and it was the f.o.s leg. A little over half way down the runway I didn't like how it was looking, and called for max power. Discussing it later with the f.o. and the f.e., we had all come to the same conclusion at about the same time. I had simply been the first to verbalize.


What is the procedure for an air traffic controller after a major crash or incident occurs on their watch? How will an air traffic controller will be treated right after a major incident?

Most units today will have some sort of CISM procedure.

Critical Incident Stress Management (CISM) is the structured assistance for a normal reaction to an abnormal event.
CISM methods are secondary preventive measures which consist of discussions about the incidents in the form of structured individual and group discussions and help the persons affected regain their ability to apply coping strategies. Most of the time these discussions are performed by colleagues who have qualified in CISM programmes (the so-called CISM peer diffusers or CISM peers) or by Mental Health Professionals (MHPs) who are qualified CISM experts. None of the CISM techniques can, or should be, regarded as psycho-therapeutic measures.

Read more at skybrary: https://www.skybrary.aero/index.php/Critical_Incident_Stress_Management_in_ATM


Why is Schaumberg Airport (06C) in Chicago an uncontrolled field? Schaumburg Airport lies underneath some of the busiest airspace in the world and is 8 miles west of Chicago O'Hare, one of the most active airports in the US. It's not the busiest uncontrolled field in the US, but it gets more traffic than some towered airports. Given the location, airspace complexity, and airport popularity why is Schaumburg an uncontrolled field?

Most likely, the airport was formed in the early-mid part of the 20th century as a small country airport outside of the Chicago metro area.  The city grew around it, similar to Compton-Woodley airport in Los Angeles or Cross Keys or Camden Co. in the Philadelphia metro area.  With the introduction of the modern airspace systems for commercial air travel the Class B shelves covered these airports but did not include them.


What are cloud clearance requirements around scuds? I'm a private pilot (in the U.S.) and I was doing hood instrument training with my instructor under VFR.  I put on the hood and we did an instrument takeoff, and I flew up to 4,500 feet to do some VOR holding pattern practice, all while under the hood.  We were in a Class C airspace.  At 4,500 feet I peeked out from under the hood, and to my astonishment we were surrounded by thin wispy clouds.  I think we even flew through one and couldn't see outside the airplane.  It looked to me that we were obviously in violation of VFR cloud clearance requirements because the clouds were less than 100 feet from the plane and we flew through some of them.  I said this to my instructor, and he insisted that we were still VFR and that I should get back under the hood and
continue the holding procedure.  I insisted again that we were clearly in violation of VFR cloud clearance requirements, and he again insisted that we were fine and we should keep flying.  After three or four times he finally conceded, and we descended and did some practice instrument approaches while clear of clouds.
On the ground after the flight, my instructor said that the clouds were "scuds" or clouds just beginning to form, and that they were see-through.  I'm a little shaken by this because I've worked with this instructor for a year and a half and I haven't seen any reason not to trust him, but I feel a little betrayed by this.  My instructor is probably in his 60s and has been flying and instructing for many years.  If I'm wrong and we were legal to fly through the scuds VFR then I'll admit that, but it seems to go against my education.  Maybe pilots normally fly through scuds with no problem, and if that's common practice for pilots then I guess I'll do that.  But if he let us fly into clouds illegally and then insisted that we keep flying, I'm a little shaken by that because I've worked with him for a long time and he seems to be a good instructor.  I'd like some clarification on this.

From a preponderance of caution, my gauge on clouds is that if you can not see through them to fly by reference to the ground or the natural horizon, it is a cloud. And, a cloud, by any other name (scud, wisp, fog, etc.), is still a cloud. It will obscure visibility.
The question that you have to ask yourself is, “What is the purpose of VFR cloud clearance?” Were you able to see and avoid an aircraft if conflicting traffic was present? Would another aircraft be able to see and avoid you?


Are there left seat qualifications specific to actual handling of the aircraft? The following three posts explain that both yokes and side-sticks require changing the hand that holds the yoke/side-stick when switching seats:

Why are Airbus captain control sticks placed on the left when most people are right-handed?
Are there risks if the side joystick must be handled with a pilot's weaker hand?
Do some right-handed pilots fail to use the left stick of an Airbus?

I can imagine at least some difficulty for a newly promoted captain having to essentially re-learn everything (handling wise) from the left seat after logging thousands of hours from the right seat (regardless of the dominant hand).

So, what are the minimum qualifications for progression from right to left seat when it comes to handling the plane? Is there extra training involved? Does a left seat pilot hold extra qualifications for handling the plane?

Or is this a non-factor?

No, it is a non-factor, although in the Navy there are aircraft you only conduct carrier landings from in the left seat. To be qualified as an instructor in that aircraft, you have to demonstrate the ability to fly the same pattern from the right seat (but not actually land on the carrier).

I'll tell a story about switching hands. I was an LSO (landing signal officer) for E-2s, which had yokes and a central throttle quadrant. You always flew the carrier approaches from the left seat, though.

We had a pilot who had developed bad habits in the landing pattern. To break him of it, I had him fly the landing pattern from the right seat at the field, which just plain felt awkward since you never did it at the boat. This made him break out of the auto-flying and have to think his way around the pattern instead, and he was able to stop what he was doing wrong. He carried the fix back over to the left seat.


On large aircraft, why do flaperons not run the full length? This is a 777 flaperon. It looks rather tiny, compared to the flap.
There have been air disasters where the airplane rolled uncontrollably for one reason or the other. It seems to me that a larger roll control authority could have helped.
Admittedly, flaps are slow, and speed-limited, so less suitable as control surfaces. But at least, could they not be used for trim?

This flaperon is actually the high speed aileron. Using the outer ailerons at high speed will twist the wing, which in turn reduces their effectiveness. For every aileron there exists a speed where it becomes ineffective and above that speed its function will even be reversed. See the flexible wing as a flap in its own and the aileron as its Flettner tab of sorts.
By using those high speed ailerons, Boeing can build the wing lighter with less torsional stiffness. In addition, it creates a gap between the Fowler flaps at the spanwise location of the engine exhaust, so the Fowler flaps will not reach into the very turbulent exhaust stream. The 737 uses an exhaust gate for the same purpose.
Using flaps for trim means you need to be able to finely adjust the position of each flap individually. This fine adjustment is better left to the smaller control surfaces or the even smaller trim tabs.


Do the pilots have to recalculate the balance when 6 passengers show up last minute in a 737? Few years ago me and my mates forgot the checkin time and were late for flight. We were late for check-in counter closure (30 minutes before flight if i'm not wrong) but the staff allowed us to go on. We had no checked luggage. There were 6 of us so at least 400 additional kilograms to be carried. Do the pilot need to recalculate mass and balance or is it within the allowance?

Loadsheets have a section called 'last minute changes'. As the name implies, pilots can record last minute changes here. If the changes are minimal, there is no need to recalculate the mass and balance, and trim settings.

What constitutes 'minimal' depends on many things, principally limits set by the operator or manufacturer. I can't verify this but think 400kg would fall within these limits, unless the aircraft was already at its performance limits.


Is it possible to fly 'in neutral'? Sometimes, when I am driving, I knock the car 'out of gear' or set the stick to the neutral position, to save fuel. This is most easily done when cruising down a hill or when you have some good speed and are approaching a stopping point, i.e an intersection.

Is there a flying equivalent for pilots? I'm wondering if during descent, or even a landing, fuel could (safely) be saved by reducing thrust to zero and gliding.

Much like how a gas pedal controls the fuel input of a car's engine, so do the thrust levers on jet-liners. The coasting equivalent is idle thrust. The engine keeps running, but with minimal fuel flow.

The minimum fuel flow is not fixed as it is a function of altitude, airspeed, and temperature. Nowadays it is typically managed by the FADEC, so the pilot (or auto flight system) can pull the levers all the way to idle and not risk flaming out.

Idle thrust in this answer refers to that minimum thrust setting that would not cause a flame-out.

An ideal descent (and its planning) does just that. Descend from cruise all the way to lining up with the runway using idle thrust.

Hitting unexpected headwind, or being asked to slow the rate of descent, would require higher than idle thrust. In the car/slope analogy, that would be the equivalent of changing the slope to a shallower one (planes, unlike cars, need a minimum forward speed).

Most jet engines also supply air for air conditioning and pressurization – it's called bleed air. On a plane like the Concorde that cruised at almost double the altitude of the common jet-liner where the air is even thinner, idling at 55,000 feet or so was not an option because of the impact it would have on the pressurization. The engines needed to run at higher than idle to provide this bleed air.

(Source: ITVV Concorde) In-flight deployment of the Concorde's reversers. Highlighted is the secondary nozzles position indicators – the nozzles double as reverse buckets.

If the Concorde flight crew wanted to increase the rate of descent, they were allowed to deploy the reversers of the inboard engines (#2 and #3) in-flight – this was done from the flight engineer's panel (shown above). This way the thrust is redirected, but the engines keep running at the required RPM for this bleed air. (According to the Type Certificate, this was limited to 4 minutes. That's about 8,000–12,000 feet of descent.)


Why does Class D overlap class B around SeaTac? ...and other Seattle Bravo airspace strangeness I noticed KBFI's class delta overlaps SeaTac's bravo by 500 to 700 feet. Does anyone know which tower the overlapping airspace belongs to? Does it classify as Bravo airspace and do you need to hear the magic "cleared into the bravo" phrase before entering the overlapping areas?

Bonus question: There is a tiny sliver of class D airspace surrounding the surface B of SeaTac on the western, southern and southeastern parts of the bravo that is surface. Anyone know if this belongs to SeaTac because there is no other field in the center of the area and if so, why on earth does a bravo airport also have a tiny section of class D surrounding it?

This is a great question. For those who are unfamiliar, and in areas where airspace is complex, it’s sometimes useful to look at the VFR Flyway Chart. This is the one on the back of FAA Terminal Area Charts.

The dashed blue outlines surround the crazy cutouts that are Seattle’s Class D airspaces.
Why does KBFI stick into the KSEA Class B?
Class D airports, or at least those that don’t exist entirely within more restrictive airspace, will always have a ceiling. This is because there will be sections that are not contained within the Class B (or C) areas. For those areas, we need to know how high the Class D airspace goes.
If there is Class B and Class D airspace in the same place, which is it?
This one is in the AIM, 3-1-3:

Hierarchy of Overlapping Airspace Designations
a. When overlapping airspace designations apply to the same airspace, the operating rules associated with the more restrictive airspace designation apply.

So, if you’re over the I-90 bridge at 1900 feet, you’re in KBFI Class D. If you’re at 2100 feet, you’re in KSEA Class B.
Why does KSEA have weird class D chunks?
This one is easier - because Class B doesn’t always go to the surface (only at the core), but there is still a need to filter out traffic from the immediate airport environs. Because two-way communication is required, pilots will need to talk to the tower before getting too close (~5SM) to the airport.
Another factor is that Class D centers on the airport; Class B is centered on the SEA VOR, and they are not coincident. This is so that the rings could (when it was circular) be defined with DME.


Why do spoilers seem to be slightly activated during take off? In this video (minutes from 10:46 to 11:00), the spoilers seem to be slightly deployed during take off. What's the purpose of this? I've already seen this in other videos too.

I've also read the answers to the question When can spoilers be used on airliners, but they seem to be related to slowing down the aircraft or for descending faster. But what is the point during take off, when it's supposed the pilots want to climb and go faster?

Spoilers lower lift and increase drag on the side where they are deployed. Symmetric spoiler deployment, therefore, is for slowing down. Asymmetric deployment not only creates a (small) rolling moment, but primarily a yawing moment which helps to counteract the adverse yaw created by ailerons, especially at the high lift coefficient at takeoff and early climb.

Spoiler deployment increases pressure ahead of the spoiler due to the slowing of local flow ahead of the obstruction caused by the spoiler, and it creates a local flow separation at and behind the spoiler, which in turn lowers the local pressure. Only the first effect lowers lift, but both create drag. The main effect of a limited spoiler deflection, therefore, is to increase drag.


Where is the inclinometer "ball" in a knife edged turn? Discussion of steep turns has lead to a question about where the inclinometer ball would be
if the plane rolled to 90 degrees.  Also, would there be any difference if the plane simply rolled to 90 degrees, rolled to 90 degrees and maintained altitude in a straight path with rudder, or rolled to 90 degrees and executed a "knife edged turn?

Does the ball become irrelevant at these attitudes?

As it was pointed out in the other thread, the ball just rolls around inside a curved glass tube.  It doesn't know what the angle of bank is, or anything other than what direction gravity, and/or centrifugal force is moving it.  Therefore:

At 90 deg AOB in coordinated flight at positive G, the ball would be centered.  The aircraft in this case would be in a descending spiral.

At 90 deg AOB in a "knife edge" straight pass where altitude is maintained with rudder, gravity will pull the ball towards the earth.  Same thing if you were able to make a knife edge turn holding altitude with rudder.


How can I best prepare for my first lesson on stalls? I am a flight student preparing to practice stalls and stall recovery in a Tecnam P-2002. I have already done spin recovery. On top of that, what preparation techniques have others found useful?

You will impress your instructor most by being eager to learn and learning quickly, and by having done book work beforehand.  Just do some reading on stalls and really get to know the 2002's Operating Manual, especially the numbers and limitations.

Be careful about trying to show that you already know it all.  If a student has taken the time to learn the operating manual and knows all the important numbers and limitations by heart, and can recite emergency drills etc while under stress, the instructor will way more impressed than if a student tries to show they already know how to do the lesson.  That being said, just read up, and really learn the manual.


When receiving a TCAS RA, DESCEND DESCEND, and starting the descent, if a pilot received GPWS warning, TERRAIN, what would they do? The TCAS warning says: " DESCEND, DESCEND" and immediately after the crew receives: "TERRAIN, TERRAIN", what would they do?

TCAS (II) does not give the descend RA below 1200 ft AGL while climbing or below 1000 ft AGL while descending.

Image from FAA Advisory Circular 20-151A Table 2

In case such an unlikely event happens (and is not an equipment malfunction), the best possible maneuver is to climb away from the incoming aircraft i.e. turn and climb to the side of the previous route.


Can aircraft fly without wings? Is it possible that a aircraft can fly without having wings? I am wondering if somehow it can fly then will aircraft will be able to maintain the balance.

Yes, they can, these are called lifting body aircraft.

Source: Wikimedia

They maintain directional stability using the control surfaces near the tail.

If you like retro documentaries, here's one on YouTube about lifting bodies done by NASA.

As for aircraft that normally have wings, they can sometimes fly when losing (most) of one of them:


Why turn off pitot tube heating? I'm merely an amateur simulator (X-Plane) pilot. On a flight yesterday the airspeed indicator stopped working. After the initial panic I remembered reading something about pitot tubes freezing, found the pitot heating switch, and turned it on. The problem was resolved immediately.

This led me to think: Is there a good reason to not turn pitot heating on before take-off, and leave it on for the entire flight?

I'm flying a Sud Aviation SE 210 Caravelle

I'm not sure what kind of airplane that you are flying in the simulator, but the checklists for jets typically do have you turn the pitot heat on just before takeoff and leave it on until after landing, just so that this is less likely to happen.

Update: I found a French checklist for the Caravelle and it says to turn on the pitot heat before takeoff:

  Rechauffage Pitot.....MARCHE


Can I legally taxi a seaplane in a canal or channel? I live on a good sized canal in a subdivision in Florida, USA.

Is it legal for me to taxi down the canal about 100 yards?
Is it legal for me to taxi down a large main channel which is part of the Gulf of Mexico to take off?

Also, when meeting a boat, who has right of way: the boat or the seaplane?

I would advise checking out the FAA's seaplane handbook for more information. In general local ordinances tend to be the issue here and not the FAA's regulations.

You can find the right of way rules in 14 CFR 91.115

  § 91.115 Right-of-way rules: Water operations.

  (a) General. Each
  person operating an aircraft on the water shall, insofar as possible,
  keep clear of all vessels and avoid impeding their navigation, and
  shall give way to any vessel or other aircraft that is given the
  right-of-way by any rule of this section.

  (b) Crossing. When aircraft, or an aircraft and a vessel, are on
  crossing courses, the aircraft or vessel to the other's right has the
  right-of-way.

  (c) Approaching head-on. When aircraft, or an aircraft and a vessel,
  are approaching head-on, or nearly so, each shall alter its course to
  the right to keep well clear.

  (d) Overtaking. Each aircraft or vessel that is being overtaken has
  the right-of-way, and the one overtaking shall alter course to keep
  well clear.

  (e) Special circumstances. When aircraft, or an aircraft and a vessel,
  approach so as to involve risk of collision, each aircraft or vessel
  shall proceed with careful regard to existing circumstances, including
  the limitations of the respective craft.

There is also a note from the hand book,

  Pilots are encouraged to obtain the USCG Navigation Rules,
  International-Inland, M16672.2D, available from the U.S. Government
  Printing Office. These rules apply to all public or private vessels
  navigating upon the high seas and certain inland waters.

Although you should not expect your average boater to understand or even be aware of the FAA regulations on this. As such caution should always be used. Keep in mind that in most if not all states you don't even need a license to operate most personal sized boats (under 65 ft. generally).

You will need to check with your local municipality (who ultimately has jurisdiction over the water way most likely). Unfortunately they may have local ordinances that are more intended for land based aircraft but may incidentally apply to you. Things like noise abatement may also stand in your way, keep in mind a plane is significantly louder than most boats.

This FAQ covers a lot of really good questions about where you can and can't land and other seaplane related topics.

Of interest to you may be Question 2

  2. Where can I keep my seaplane?

  A seaplane can be kept at a certified seaplane base with permission, or at an  airport if it is equipped with
  amphibious floats. If you want to keep your seaplane "off airport",
  however, you will need to explore the issue with your state
  aeronautics office, local government and the owner of the waterway.
  Some specific problems include mooring restrictions imposed by the US
  Army Corps of Engineers, seaplane base licensing requirements imposed
  by state governments and zoning regulations imposed by local
  jurisdictions.

In this kind of situation I would personally seek out a local lawyer that specializes in aviation related matters (a call to your local GA field may get you a name). Unfortunately many local authorities don't always understand the regulations and many don't even know its with in their power to regulate such operations since the cases tend to be few and far between. In other cases older forgotten regulations may have relegated them selves to a dusty file cabinet that no one remembers. Other local sea plane owners may also be of help here.

It is also worth considering if you have the width to actually pull this off. Even the biggest boats I have been on (in and around the 55ft. size) are generally no wider than around 15ft. at the widest point. A Cessna 172 has a 36ft. wingspan which is something worth thinking about.


What are those hatches on the engines of a B-2 that are open during takeoff? I just watched this drool-inducing video of Northrop Grumman B-2 Spirit, And noticed that there are a couple of hatches near each engine, which were open:

I initially thought they were open for some sort of maintenance. But the video features a takeoff roll of the bomber (around 5:00 minute mark), and I again noticed that the hatches were open during the roll. However, they were retracted immediately after the aircraft left the ground (around 5:25 mark):

This makes me wonder if these hatches serve some special purpose. What are they, and why are they open during the takeoff roll?

Edit: Please don't say you don't see an aircraft, because the landing gear doors are down and radar signature is immense due to that. :)

These are secondary intake doors which allow more air to reach the engines. They are opened by the engine control computer when the main intakes are not providing enough air for the power setting of the engine. In order to minimize radar cross section, the engines of the B-2 are buried in the wings and the intake needs to be curved. Also, and for the same reason, the intake lips need to be sharp-edged. Both factors increase the drag of the intake flow and reduce the mass flow of air to the engines. Like on other low-RCS aircraft, secondary intake openings are needed to increase this mass flow.

In automatic mode they will close when the aircraft accelerates above Mach 0.4. Below 43F, they remain closed for taxi and are only opened for take-off. A take-off with closed doors is possible according to this thread, but needs a reduced power setting to 80% for the engines below 50 kt speed.


Why don't the contrails show the curvature of the Earth? When we see contrails in the sky, let's say traveling left/right in your vision, you are seeing across a sky that is easily a couple of hundred miles wide. I mean, we can see one side of space and then another, so we can see across a great distance in the sky depending on the height of an object.  Am I wrong?  I mean, we can see entire cities from a long distance away on the ground, so an unobstructed view of the sky would give us the ability to see something very long, right?

That being said, an airplane is following a curve, and when a plane makes a trail it is essentially tracing out the shape of the earth. Being that this trail is very high up, and following the curve, why don't the trails curve (left/right trail), and we see a giant arch across the sky?  None of the lines in the sky look curved from any direction, they are straight lines, or at least appear to be.

Am I missing something?  Maybe it's a dumb question, but I remain ignorant on the topic because I haven't been able to find the answer from anyone with a clue.  This site seems legit, so I asked it here.  Thanks, in advance.

Some contrails disperse and therefore end up being short to show any curvature.

(contrailscience.com)

Long ones don't stay put because of the wind. They wiggle.

It's for the same reason flying at 30,000 feet the Earth's curvature is not apparent. Earth is huge and it takes higher altitudes for the curvature to become noticeable to our eyes.

(californiacapitalairshow.com)

Flying higher at or above 60,000 feet or so (where the Concorde cruised) the Earth curvature starts to become more noticeable.

To notice it from the ground, you need a very clear day, not the slightest haze on the horizon, calm winds, and the plane to come from the right angle, as the illustration below shows:

(metabunk.org) 5-mile grid at 35,000 feet seen from the surface.
Note that the lines are squashed together the farther they are, so it'll take a very long contrail at a low angle above the horizon (called an altitude in astronomical terms) for that curvature to be easily seen.
RE comments:

The horizontal lines aren't as curved:

That's a property of one-point perspective, you see more depth than breadth.

The contrails are at least a few hundred miles long:

Not when viewed moving side-to-side. Jetliners cruise at around 550 MPH. The grid above shows what 5 miles are like. A 250-mile long contrail would take a plane 30 minutes to draw. You can time the next plane you see for proof on how long it takes to pass side-to-side in your field of vision. A lot less than 30 minutes. Example below is from a time lapse video:

Click image to open the GIF.
The GIF duration is 1.29 seconds and the video is shot at 5-second intervals at 24 fps. The contrail moved right to left in ~2.5 minutes, or roughly 25 miles (5 squares).


Does the cockpit have an alarm to warn about fuel leakage? Is there any indication to the crew of the aircraft about any potential leakage of fuel from any part of the plane?

In a typical trainer aircraft (in this case, a C172), you have an annunciator panel that includes a "Low Fuel" light:

These lights only come on when fuel is low if the lights are functioning properly. This panel is located prominently, and is easy to notice. This is only one aircraft, but when you consider it is an entry level aircraft that is less sophisticated, it gives a baseline idea of what you could expect to see.
Also, there are fuel gauges displayed with all engine instruments that will indicate accordingly. While this isn't a leak detector, pilots are trained to monitor all instruments regularly and cross check the values - which is how a leak is identified in aircraft with low amounts of technology.
It is worth noting that checking the "LOW FUEL" annunciator is off is a regular checklist item that occurs before you start your actual flight.
As GdD mentions in the comments - you are taught not to rely on any one instrument indication, and panel lights are no exception.


Is/why isn't the Antonov 124 to 225 wing upgrade method common? I'm told that wing redesigns (edit: for tapered, swept wings) are difficult, so variants of a model often do with a common wing optimized for the middle member.
But then I read the following:

Based on Antonov's earlier An-124, the An-225 has fuselage barrel extensions added fore and aft of the wings. The wings also received root extensions to increase span.

That doesn't look so difficult. Of course, the wing root would be a new design, but we still get to keep the rest of the wing. Perhaps the flutter modes are less favorable......but wouldn't that be more or less inherent to higher spans?
So: Is/why isn't this method used to design variants or derivatives of large airliners?

With straight wings the root extension method is very common. Airplanes that come to mind are

Me-109 H (high altitude version with increased span)
Beech Twin Bonanza and Model 65 Queen Air (used the Bonanza wing from the engines out)
SB-10 (uses SB-9 wings stuck to a new carbon-epoxy center wing).

This is impractical with swept wings because of the strong twist and airfoil changes which are needed at the wing root to keep the isobars straight on the swept wings. The only way to increase an existing wing's size was used for the A340-500/600 by inserting a triangular section at mid-chord into the A340-200/300 wing which also allowed to increase its wingspan.

Source: Evolvability and design reuse in civil jet transport aircraft


What are ARTCC, RCO and FSS and what are differences? I am confusing what ARTCC, RCO and FSS. and also what do they do?
Do they control air traffic by communicating with pilots?
Also, do they offer WX information in air born?

ARTCC or Air Route Traffic Control Center:

Does control traffic, generally in larger areas and above FL180 (Class A airspace)
Will broadcast some weather info and provide advisories

  ARTCCs broadcast a Severe Weather Forecast Alert (AWW), Convective
  SIGMET, SIGMET, or CWA alert once on all frequencies, except
  emergency, when any part of the area described is within 150 miles of
  the airspace under their jurisdiction

RCO or Remote Communication Outlets:

Extends the range of FSS broadcasting ability
Many are being shut down

  The remaining RCOs are of two types: 1,223 RCOs that allow pilots to
  contact flight service and receive transmissions over a common
  frequency; and 398 RCOs over which pilots can transmit—usually on
  122.1 MHz—and monitor flight service’s response on the frequency of a co-located VOR.

FSS or Flight Service Stations:

  Flight Service Stations (FSS) are air traffic facilities that
  communicate directly with pilots to conduct preflight briefings,
  flight plan processing, inflight advisory services, search and rescue
  initiation, and assistance to aircraft in emergencies. FSS also relay
  Air Traffic Control clearances, process Notices to Airmen (NOTAMs) and
  provide updates on aviation meteorological and aeronautical
  information.

Provides inflight weather, preflight planning and clearances and takes NOTAMS. Does not control traffic in the air but is involved in dispatching instructions (clearances) prior to takeoff.

Offering weather is a bit tricky. Controllers and those on the other end of the radio all have access to different levels of weather information and weather radar. Many will provide some level of information if asked. What they will provide is perhaps worthy of its own question here.


What's the minimum cruise speed of modern airliners? Often when approaching landing, I feel the aircraft slow down considerably, it hasn't landed yet, but kind of hovers around waiting for clearance to land. Thus I was wondering, is there any defined minimum cruise speed for airliners.

It's called the stall speed. Below which the wings won't give enough lift to stay airborne.

Another minimal speed to adhere to is the minimal control speed. Below that the controls surfaces won't be able to counteract suddenly losing an engine.

However slowing down before landing has nothing to do with waiting on their turn/clearance. If they need to wait they go around in a circle instead.

The slowing down is so they touch down with as low speed as possible to limit the braking distance needed on the runway.


How does experienced pressure vary with airspeed? Drag increases with the square of airspeed. Is the same true of the pressure that a forward-facing area experiences?

As an aircraft approaches and then exceeds the speed of sound, how does experienced pressure on a forward-facing area increase?

1) Pressure is simply a force divided by an area, so yes: The dynamic pressure experienced by a forward-facing surface will, in an incompressible flow, vary with the square of the speed.

2) The dynamic pressure increases dramatically as one approaches the speed of sound, once going faster than mach one the pressure will begin to decrease. The trans-sonic phase (around mach one) is difficult to describe and can depend on the airflow around the body - but in many cases it can be quite stable.

-edit-
For the second question here's a couple of links that can provide more information:

Transonic flow around a rocket
NASA history of transonic research


Why does JetBlue have aircraft registered in Germany? I recently saw a JetBlue A321 with a German flag on its tail and was wondering why it would be registered in Germany if it was a US-based carrier. I was thinking maybe it had something to do with Airbus but I wasn't 100% sure.
Any thoughts?
Thanks!
Image source: https://www.linkedin.com/feed/update/urn:li:activity:6771365770770309120/

I am the pilot who delivered this aircraft on Friday.
The German registration remains on the aircraft up until the time we (JetBlue) purchase the aircraft. Prior to transfer of title, we perform a series of ground tests and flight checks.  This is all accomplished while Airbus still owns the aircraft.  Once any discrepancies are corrected, and we accept the aircraft, we buy it, the ownership changes and the temporary (German) registration is removed. This is typically the day prior to ferrying it over to the US.
As for the Hamburg/Toulouse question- TLS does not produce A321 aircraft, so all of our JetBlue deliveries come from either Hamburg or Mobile, AL.


Why does the B-52 take off without rotating? In the answer to this question it is noted that the B-52 takes off without rotating and climbs out in a nose-down attitude. Why was it designed this way?

The reason was to give the bombs the place close to the center of gravity.

Wing sweep (for high cruise Mach numbers) in combination with a high aspect ratio of the wing (for low induced drag) made it impossible to place the landing gear in the wing, so it had to be integrated into the fuselage. The main landing gear normally needs to be close to the center of gravity (slightly behind for a tricycle gear, slightly ahead for a taildragger), but this space was needed for the massive bomb bay. Since the bombs will be dropped somewhere along a bombing mission, dropping them should not upset the balance of the aircraft, so no compromise was possible.

B-52 cutaway drawing showing the two bomb bays in the center of the fuselage (picture source)

This problem existed already during the development of the 6-engined B-47 a few years before. In both designs, two pairs of landing gears were chosen, one pair ahead and one pair aft of the bomb bay, and the aircraft lost its ability to rotate for takeoff. Due to the powerful fowler flaps the attitude in cruise and at slow speed could be made identical. The downside is more drag during the take-off run, since the wing produces more lift, but this could be tolerated in a strategic bomber with air refueling capabilities.

B-47 on approach with gear down and drag chute deployed (picture source). Note the outriggers between the inner pair of engines - those were needed to keep the aircraft level on the ground.

B-52 in flight with gear down (picture source). Here the forward and aft gear of the B-47 have been replaced by pairs of gears to distribute the load over eight wheels and the outriggers are positioned outside of the outer engine pair, but the general gear configuration is fairly similar.

The Russian design bureau Myasishchyev found a different solution for their M-50 supersonic bomber in the mid-50s. They also had to put the bomb bay into the center fuselage and the main gear had to be placed so far aft that the M-50 could not be rotated the usual way with the elevator. To solve the problem, the engineers devised what they called the "galloping bicycle". When the aircraft reached 300 km/h, the forward gear rapidly extended to rotate it to 10°.

Myasishchyev M-50 with extended front gear strut (picture source). The two open doors under the cockpit were for the pilot and navigator: Their downward-ejecting seats would be lowered on cables for the crew to be strapped in at ground level, then winching themselves into place.


What is the purpose of the hole in the Cirrus SR22's parachute? Watching this video I notice there is a big hole in the middle of the parachute, at its top when deployed. This feature seems to exist in other smaller parachutes.

For me, it seems that air can escape the parachute by this hole and thus the parachute is less efficient than a same-sized parachute without this hole. But it must serve in a way I don't imagine. What is its purpose?

For me, it seems that air can escape the parachute by this hole

That's the point, air HAS to escape the parachute anyway, and without the hole it would do so laterally and in an uneven fashion, leading to lateral oscillations.

The hole allows the air to escape in a controlled location, avoiding undesired and possibly dangerous oscillations.

Some (most personal ones, but for example not the SR22 one) parachutes have handles that allow the user to deform the parachute: this allows some extra air to escape from the desired side, giving lateral controllability.


How do aircraft engine manufacturers achieve a higher bypass ratio while still meeting the thrust requirements for a given aircraft? I understand that a higher bypass ratio leads to greater efficiency as less air moves through the core, and therefore less fuel is burned. However, how is the thrust requirement for the same aircraft met with a newer engine that has a higher bypass ratio? Since most of the mass flow will be provided by the front fan, I want to understand what changes are made to turbofan engines that allow the same amount of thrust while minimizing airflow through the core.

Early turbojets were so inefficient that adding a fan was considered but not implemented because that would had made the engines even more sluggish and narrowed the operating limits even more. If you compare the Jumo 004 with the EJ200, you will find that both are of similar size, have  8 compressor stages, but vary widely in their compression ratio and thrust (3.2 vs. 26 compression ratio and 9 vs. 60 kN dry thrust).

When compressor flow was better understood, turbine temperatures and pressure ratios rose, the excess power delivered by the engine core rose and allowed to drive a second turbine and shaft; initially with bypass ratios as low as 0.25. If you compare the overall pressure ratio with the bypass ratio, you will certainly spot a trend:

Engine             compressor       pressure ratio     bypass ratio
RR Conway        7LP, 9HP stages       14  :1             0.25:1
P&W JT3D      2fan, 6LP, 7HP stages    12.5:1             1.42:1
GE CF6-6      1 fan, 1LP, 16HP stages  25  :1             5.8 :1
RR RB211-535  1 fan, 6IP, 6HP stages   25.8:1             4.3 :1
GE 90         1 fan, 4LP, 9HP stages   42  :1             9   :1
RR Trent XWB  1 fan, 8IP, 6HP stages   52  :1             9.3 :1
RR Ultra Fan                          >70  :1           >15   :1 (projected)

A more efficient core allows to leave more energy in the exhaust past the high pressure turbine, so the low pressure turbine can extract more power to drive a larger fan.


How long does it take for pilots to become unconscious after an uncontrolled depressurization at FL 340? I've just read a news article on the depressurization incident that happened today in Australia. How much time did the pilots have before they lose consciousness if they hadn't used their oxygen masks? This incident is said to have happened at FL 340.


What lifting gas was used for barrage balloons during the world wars? During the world wars, various barrage balloons were used to protect targets from low-flying aircraft or similar threats (e.g. V-1 flying bombs), in particular by Britain.
What lifting gas was used for such barrage balloons – the highly flammable hydrogen or the rare and expensive helium?

According to a BBC article here, hydrogen was used, not helium.


How are military aircraft directed to targets? How would a controller, say, AWACS or ground radar, direct via voice an aircraft to the location of an airborne target?

I've seen it in movies, but don't know if they where right, nor did I understand it.

The controller has radar ID of both aircraft. The radar display used is 'smart' in that it can plot the direction and speed of flight of the target and attack aircraft. It then is a simple matter to direct the attacker on a course to intercept the target.  At least that is how I did it, once.


Could a GE90-115 engine generate enough suction to ingest a typical passenger vehicle? We all know that a jetliner can generate enough blast behind it to toss around cars, light aircraft, and even the occasional school bus, and also can generate enough suction to inhale (and promptly destroy) unwary ground crew.

However, if some foolish ground person drove a car (let us assume it's a typical passenger car of exactly 1 ton weight) into the intake hazard area of a GE90-115 engine during a full power runup, would that engine generate enough suction to pick the car up and attempt to ingest it? Or would they have to get so close to the intake that they'd notice that they'd better put the pedal to the metal and get out of Dodge before they went for one last, most unfortunate ride?

This question would probably be better answered by an automobile aerodynamicist, so be wary of my assumptions. Hopefully, I can at least outline how to get a rough estimate.

Assuming that a "typical passenger car" is less streamlined laterally than longitudinally, let's consider a car crossing orthogonally to the intake airstream of the engine. Assume also that the intake air only generates a force on the car pointed towards the center of the inlet, parallel to the ground, and low enough to not tip the car over (this may not be a good assumption, as crosswinds can generate other aerodynamic forces on a car, especially if it's moving forward or backward).

The problem then basically reduces to overcoming the friction between the tires and the surface on which they rest; let's assume it's concrete. We can start right at the inlet, because if the engine can't move the car there, it can't move the car anywhere in the intake hazard area.

Here's a helpful paper (if I'm interpreting it correctly) that experimentally determined some dimensional sidewind coefficients $K$ for typical vehicles under a somewhat analogous situation. It's a bit odd to use a dimensional coefficient (and thanks to Koyovis for pointing that out; always check your units!), but with some unit conversion we can make it work. Let's take $K=.003(239.6)=.7188\;\mathrm{kg/m^3}$ as a typical value. The side force on our car is thus
\begin{equation}
F=KAV^2\,\text{,}
\end{equation}
where $A$ is the area facing the flow and $V$ is the air velocity. Let's say a good value for the area of a side of a car is $5\;\mathrm{m^2}$ based on this calculation from these numbers.

The mass flow rate $\dot{m}$ of a GE90 at full thrust is $1350\;\mathrm{kg/s}$ and the intake radius $R$ is $1.562\;\mathrm{m}$. Taking a standard air density of $1.225\;\mathrm{kg/m^3}$,
\begin{equation}
V=\frac{\dot{m}}{\rho\pi R^2}=144\;\mathrm{\frac{m}{s}}
\end{equation}
or about 320 mph.

You've specified a mass $M$ of $907.185\;\mathrm{kg}$, so we'll use that. The static coefficient of friction $\mu$ between dry concrete and rubber is around $.75$. So the force we need to overcome is
\begin{equation}
f=\mu Mg=6675\;\mathrm{N\,.}
\end{equation}
Meanwhile, assuming the whole side area of the car is exposed to the maximum air velocity,
\begin{equation}
F=KAV^2=74525\;\mathrm{N\,.}
\end{equation}

So, under our assumptions, the engine has more than enough suction to ingest our car at the inlet. However, I think a more realistic mass $M$ is about $1270\;\mathrm{kg}$, which yields
\begin{equation}
f=\mu Mg=9344\;\mathrm{N\,,}
\end{equation}
which is still plenty below what the engine produces.

So we've determined that at the inlet the engine should be able to suck up a car. But what about the entire hazard zone? We calculated the inlet velocity right at the lip of the nacelle, but the area over which the engine draws air is much, much larger even inches away from the intake, seeing as the hazard zones extend behind it. Thus, at a distance away equal to a typical car's width, the velocity will be quite a bit lower. Let's model the increased suction area as a half-circle with a radius $R_0$ extending from the point on the ground directly beneath the hub of the fan.

First, let's calculate the actual airflow velocity needed to move the 1270 kg car:
\begin{equation}
V_0=\sqrt{\frac{f}{AK}}=51\;\mathrm{\frac{m}{s}}\,.
\end{equation}

Now, we can calculate $R_0$ based on that velocity:
\begin{equation}
R_0=\sqrt{\frac{2\dot{m}}{\pi\rho V_0}}=3.7\;\mathrm{m}\,
\end{equation}

or about 12 feet. The intake hazard zone for the much smaller CFM56 has a greater radius than this. So if we assume that all the air going into the engine comes from the hazard area and neglect the presumably increased hazard area for the GE90 (quite conservative), our car will still be okay unless it is right in the inlet. So, "would they have to get so close to the intake that they'd notice that they'd better put the pedal to the metal and get out of Dodge before they went for one last, most unfortunate ride?" I say yes.

However, because vehicles in jet blast tend to get tipped over and lifted from the ground, a simple statics problem is probably not the best model, but I don't have enough background in automobile aerodynamics to tackle the full dynamics problem.


What makes it so hard to land on an aircraft carrier? I have heard it is very difficult for a pilot to land on a carrier deck.

I have read this question but it didn't really give me a sense of the challenges that pilots face.

This question lent me the insight that metal decks, themselves, have different properties (that I should have considered)... perhaps friction, changes due to thermal shifts (that asphalt does not exhibit), perhaps it 'gives' differently under touch-down pressure.

Can someone paint a more-complete picture?  I'm sure there are also other factors, besides that the deck is moving.... but even then - perhaps there are 'different kinds' of movements of the deck that I haven't considered.

Edit

Since another user, with actual carrier experience, has given a detailed answer, please refer to his answer.

It now appears that a good part of my answer was incorrect.  As I wrote in the beginning, my answer was based on flight-sim experience, and reading, but nothing formal or official.

I'll leave my answer up, solely for historical reference, unless the better answer gets accepted.

I've never done it IRL, but read about it lots, and Flight Simmed it many times, so I'll take a stab.(until someone who has actually done it says better)

Glide Path
When landing on a fixed runway, your glide-path is pretty much right towards the end of the runway.Its not like that at all on a Carrier.  From up high, you are actually aiming for a point in front of the carrier.  You're aiming for where the runway will be in 30 seconds.   As you get closer, the carrier moves closer into position.  But still not entirely in position until the last second.   So you're always aiming for an invisible/imaginary point where the runway will be at the last second.
This is the best picture I've found of what I'm describing:

Notice that the flight path indicator (the little circle in the HUD) is well beyond the front of the carrier.  If this plane was landing on a runway, the flight path would be aimed right at the numbers.
No Flare
In a typical runway landing you flare out just before touchdown, "float" for a second and drop on to the runway.In a carrier landing, you maintain your glide-path attitude all the way on to the deck.   There's no flare or float. This helps you hit exactly the spot you're aiming for (the 3-wire), but in some sense you really are crashing into the deck at a not-inconsiderable descent rate.
Pitching Deck
Remember the glide path to the imaginary touch-down point?  Because the carrier deck can be pitching or rolling in the waves, that imaginary touch-down point is not a fixed distance directly in front of the ship.  As the ship bobs and weaves around, your touchdown point is moving around too.   That makes it even harder to hit the point right.  It can well be at the last second, as your plane is dropping quickly, the deck suddenly jumps up to meet you, making the impact even more violent.
Sideways Movement
The landing part of a carrier deck is the diagonal part on the back of the deck.   It is angled about 20-degrees to the left, relative to the carrier.  But it is moving directly forward with the movement of the carrier.  This means the "runway" is not moving directly away from you, but slipping sideways.


What would be the impact of replacing the engines on the 737 MAX, not just reworking MCAS? There has obviously been a lot of focus on the MCAS failure following from the 737 MAX crashes. However, the MCAS appears to be a compensating control for design decisions, specifically the replacement of the CFM56-7BE engines on 737NG with the much larger, more efficient LEAP-1B. That in turn necessitated a higher ground clearance.

In lieu of redesigning the landing gear to provide greater clearance (and raising the overall height of the plane), the engine pylon was redesigned, moving the engine further ahead of the wing and closer in line with the wing surface. There were other changes as well.

The re-positioned engines changed the thrust line. The resulting control characteristics were compensated for in software, with the MCAS addressing a very specific negative flight characteristic.

Notwithstanding the new engines being more efficient (resulting in lower operating costs), is it possible and what would be the impact of retrofitting the existing fleet of 737 MAX with an engine and pylon in the previous position ? Could for example, the CFM56-7BE and pylon be retrofitted?

There are plenty of plane models offered with multiple engine configurations, though I imagine they are fit off a similar pylon / housing.

If I were an operator of MAX fleet in which the public has lost confidence in flying on, I'd like some other option than scrapping the fleet. Edit/Addenda: I don't know anyone is planning to scrap the fleet and it's far too early to suggest what the final outcome may be as this story plays out. There have definitely been order cancellations, orders lost and questions surrounding the plane's certification. You can't cancel an already delivered/completed order; it would be difficult to force Boeing to buy them back and replace them (with what?). IF Boeing offered to "retrofit the MAX as an NG-like", it might be the best possible outcome for all.

It certainly seems less drastic than Boeing starting from a completely different base design or losing customers to Airbus.

Possible? Yes.  Economically feasible, not even close.  To re-engine the plane, you would basically have to re-do a large amount of the FAR 25 certification.  Right now, Boeing has to re-do one thing, and it will take a few months.  To re-engine the plane would take several years at the least.  However much money it is losing right now, it is a drop in the bucket compared to the cost of what you propose.


Do any civilian aircraft use AESA or PESA for weather radar? Are there any weather radars in civilian aircraft that uses active or passive array techniques? I know that the most of the radar used in the civilian aircraft use doppler effect and latest military aircraft use AESA radars.

Doppler and Electronically Scanned Arrays are different types of technology. Doppler is a method of using radar to determine relative velocity of a radar return. An ESA is a type of radar transceiver. Doppler is useful for detecting precipitation and would probably still be useful on an ESA radar.

Probably the main reason that weather radar has not widely gone to ESA is cost. Especially AESA (Active Electronically Scanned Array) is very expensive. In a military environment, the extra functionality makes up for the high cost. But current weather radar on aircraft works "well enough". The technology has been in use a long time and is well-understood. Advances in signal processing have brought more and more capabilities. There need to be large benefits to justify the expense of developing and certifying a new architecture.

One benefit of ESA radar can be the lack of moving parts. However, a single array would have a limited field of view, where current radars can typically see 180 degrees in front of the aircraft. They could add mechanical steering, but that would be even more expensive to steer something heavier and more delicate than the typical slotted antennas used today.

There's also the issue of military usage. Although many countries have developed ESA radars, there may be some government resistance to exporting that kind of technology.

Although current technology still struggles to detect hazards that lack precipitation such as clear air turbulence, the industry is looking to other technologies such as LIDAR to fill this gap.


Can you feel passing through the sound barrier in an F-16? Is it possible for the pilot to feel passing through the sound barrier in an F-16?

What about other modern aircraft, will you feel anything? Do you need to go back to really dated designs before you can notice this, is it a problem of the past, or did the documentaries I watched which discussed this problem grossly exaggerate it?

In an aircraft designed to go supersonic, it's an absolute non-event, and one is only aware of it by observing the instruments, and noting diminished control authority-- slower roll rate, etc. At least, that was my experience in the T-38, and according to every account I've read.

If the aircraft is NOT designed to go supersonic, then the experience can be quite different, although that mostly comes from loss of control at high Mach numbers (starting in the 0.9X range, as best I recall), rather than anything that occurs right at Mach 1.00.


How should I attach an aircraft model in a wind tunnel when testing wind gust/yaw stability? Where should I attach the rod to the aircraft model when simulating wind gust /weather vane effect in wind tunnel testing? At the center of gravity, behind the CG, in front of the CG...?

In order to measure yaw derivatives, the airplane has to yaw when in the tunnel. If you mount it at the center of gravity, which should be reasonably close to the geometric center, it will stay in the center of the tunnel section.
In the old times, windtunnel models were mounted on strings. I expect that your model sits on a long sting. This sting sits on a rotating scale which rotates such that the mounting point does not move around when the scale is rotated. Alternatively, the scale is inside the model (see picture below). If your arrangement is different, please point this out in an edit of the question!

Internal force balance and sting (picture source)