70
votes
Accepted
Why is tape being applied to this jet engine?
It's not duct tape. It's speed tape.
Speed tape is an aluminum pressure-sensitive tape used to do minor repairs on aircraft and racing cars. It is used as a temporary repair material until a more ...
- 31.3k
66
votes
Accepted
How are aircraft depainted?
Paint stripper. Lots of paint stripper.
(originally I said thinner, but I have been corrected, it's more accurately called stripper)
Seriously though, it's actually not too different to other things ...
- 631
53
votes
Accepted
Why do military jets sometimes have elevators in a depressed position when parked?
It generally means that the hydraulic actuator (power control unit) driving the surface has an "idle" facility that allows fluid to move internally between the two sides of the actuator piston, or ...
- 134k
53
votes
Accepted
Why are 'ghost flights' necessary?
Airliners are both larger and more complex than the small aircraft you're familiar with at your local flight school. For an example of some of the items to consider, see: What do you need to do to ...
- 73.5k
46
votes
Accepted
Why are aircraft coloured in yellow during construction, repair or overhaul?
For unassembled and new planes or planes not yet painted the green/yellow color you see is the anti-corrosive coating on the aluminum
...every unpainted airplane is nominally green from being ...
- 102k
45
votes
Accepted
Why do aircraft piston engines consume so much oil?
Automobile engines are not similar. They are liquid-cooled and therefore can be built to much tighter tolerances with regard to thermal expansion and contraction.
Air-cooled aircraft engines must ...
- 37.9k
42
votes
Accepted
Do multi-engine jets need all engines with equal age to reduce asymmetry in thrust and fuel consumption arising out of deterioration?
It doesn't quite work that way. When an engine wears out it's rated thrust doesn't decline; its "ITT Margin" (or some similar phrase - basically its thermodynamic margin at takeoff) declines.
When ...
- 134k
42
votes
Accepted
Why might using flaps trip the breaker on a Cessna 172G?
Something is wrong with your flaps, the wiring leading to them, or the breaker itself. The breaker is tripping to keep your plane from starting on fire. Stop resetting it and have a mechanic look at ...
- 17.5k
38
votes
Accepted
Can the emergency slide be re-used after it has been deployed?
Sure. In fact, the emergency slides have to be removed from aircraft and tested periodically under present regulations.
According to Lufthansa Technik:
Under current regulations each emergency escape ...
- 100k
37
votes
Accepted
How do jet engines generate electrical power?
All jets and turbofans run a gearbox driven off the outer spool shaft. The gearbox has drive pads for all of the powered accessories like hydraulic pumps, fuel pumps, and the generator, and an input ...
- 134k
36
votes
Accepted
What is this cylinder covered in threaded studs and what is it for?
It's the inner liner of a heat muff, either for cabin or carb heat (you can see the engine mount tubes right next to it and that's exactly where I'd expect to see it, and the black pucks behind are ...
- 134k
36
votes
Why would it not be OK to replace a map light bulb with an LED?
White LED spectra contains quite a bit of blue range wavelength, which is bad for night vision. Red light is much better.
The eyes have cone receptors for day time and rod receptors for night vision. ...
- 20.9k
32
votes
Accepted
Why should an overheated wheel be approached from the front/back and not in line with the axle?
Besides staying clear of the fuse plug in the rim, it's partly because the sidewall of the tire is the weakest part of the carcass, so that a rupture from overpressure from overheating means most of ...
- 134k
31
votes
How are aircraft depainted?
In addition to the chemical method in Simon's answer, there are mechanical methods, like bead blasting. This method was introduced in the 80s by airforces concerned with the volume of chemical waste ...
- 8,611
30
votes
Passenger window insert pops out mid-flight
Copied from https://thepointsguy.com/news/what-are-airplane-windows-made-of/:
A cabin window consists of three panes: 1) an outer pane flush with the outside fuselage, 2) an inner pane — which has a ...
- 3,719
29
votes
Accepted
What sort of debris has been found in 737 Max fuel tanks?
As a generic answer, not unusual. Besides personal objects like bucking bars, clecos, rags and such left in tanks, the biggest contamination source, from my experience working on a production line ...
- 134k
29
votes
Accepted
What does the abbreviation "SCMOH", related to an engine overhaul, mean?
The C refers to "Channel Chrome" (SCMOH = Since Chrome Major Overhaul), a plating process used to restore worn-oversize cylinder bores. What they do is electroplate the cylinder bores to ...
- 134k
28
votes
Why are 'ghost flights' necessary?
Perhaps this adds little to the answer already posted, but I feel it needs to be emphasized that
airliners are designed to fly.
Designed to fly a lot, in fact. Like, spend a significant portion of ...
- 3,347
28
votes
Is Aeroflot flying airliners without brakes?
The Aeroflot warning, on which the article is based, states:
The exact translation of the message's title is:
"Safety culture (braking with a deactivated brake)". With this wording, "...
- 28.3k
26
votes
What to do when an AD is published but your aircraft is nowhere near a maintenance facility?
First thing you would do is study the compliance requirements of the AD.
Most ADs come with some kind of "fly-by" compliance period either by calendar date or hours/cycles. It's pretty ...
- 134k
26
votes
Accepted
What does Line imply in Line Replaceable Unit?
"Line" refers to "Air Line" or "Flight Line". It's the same "line" as when you refer to "line operations" or, for pilots, "line indoctrination&...
- 134k
25
votes
Accepted
Why would a C150 tachometer bounce so much that the needle fell off?
Cessna 150s have a mechanical tachometer driven by a mechanical tach drive cable geared to the engine.
The tach needle is moved by sensing spinning magnets driven by the tach cable.
They do wear ...
- 37.9k
24
votes
Why would it not be OK to replace a map light bulb with an LED?
Quite simply because a random LED bulb is not certified for operation in an aircraft, and the light holder is not certified to operate with a LED bulb.
In practice it would probably work fine, but it ...
- 481
23
votes
Accepted
What is the small cylinder on the firewall to the left of the battery?
That is a fuseholder for the optional clock or optional Hobbs meter. The yellow wire probably should be connected to it but you should have a certified mechanic inspect it.
- 37.9k
23
votes
Accepted
What do you need to do to bring a 737 Max back in service after 6 months in storage?
Bringing any plane back into service will involve more or less the same things but vary in scope and scale depending on the size of the aircraft. It looks like Southwest is moving their 737's to their ...
- 102k
23
votes
Why did older versions of B747 use radioactive material?
The counterweights were 12 to 83lbs, 99% depleted uranium, coated with nickel and cadmium. There were "21 to 31" of the weights in the tail, with 692-1059 pounds of counterweights per plane. ...
- 2,801
23
votes
Is Aeroflot flying airliners without brakes?
It is most certainly not legal* or safe for an aircraft to operate with all its brakes disabled. News reports indicate that the aircraft are 5 Boeing 777 and 4 Airbus of various types. They are less ...
- 17.5k
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