71 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 ...
  • 30.9k
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 ...
56 votes
Accepted

Why isn't there a "check engine" light in airplanes?

With a few exceptions (modern aircraft engines with FADEC systems) a "Check Engine" light on an aircraft would be essentially useless. In a modern car we have an Engine Control Unit which manages ...
  • 67.5k
54 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 ...
  • 110k
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 ...
  • 69.9k
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 ...
  • 96.5k
45 votes

Why isn't there a "check engine" light in airplanes?

Because your basic premise is completely wrong. The people flying a Cessna or Cirrus generally have a vast amount more knowledge about their planes than the average car owner. Between the POH (Pilot ...
  • 1,405
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 ...
  • 34.4k
43 votes
Accepted

Do any aircraft carry spare parts for making repairs?

South African Airways flights to 'less developed' locations in Africa often carry a mechanic and some spares on board. If there are no suitable repair facilities, supplies or maintenance personnel ...
  • 70.6k
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 ...
  • 110k
38 votes

Could most commercial jet engines today run on ethanol without any problems?

Although turbines could be designed to run on ethanol it's actually a lousy aviation fuel (actually it's a lousy fuel in general). Petroleum-based jet fuel is high grade kerosene which has lubricant ...
  • 50.6k
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 ...
  • 98.8k
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 ...
  • 110k
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 ...
  • 110k
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. ...
33 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 ...
  • 110k
32 votes
Accepted

What is ETOPS and how does it work?

ETOPS stands for Extended-range Twin-engine Operational Performance Standards, a rule which permits twin engine aircrafts to fly routes which, at some point, is more than 60 minutes flying time away ...
  • 39.3k
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 ...
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 ...
  • 110k
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 ...
  • 110k
28 votes
Accepted

How are off-wing jet engines transported?

They have the usual transport options: shove into cargo area, on a flatbed truck, shipping container,... They can also be attached below the wing of a large aircraft and flown with if there is no ...
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 ...
27 votes
Accepted

Why are cabin doors outlined with a different color than the fuselage?

The doors are painted like this because it is a federal law that all cabin doors on commercial airplanes should be outlined in a color which contrasts with the fuselage color. It is done so that in ...
  • 29.2k
27 votes

Do any aircraft carry spare parts for making repairs?

All of the 747-100/200 freighters I flew in the 1990s had FAKs (Fly Away Kits) aboard. I just checked a couple of the weight & balance data sets I still have from having done weight & balance ...
  • 38.7k
27 votes
Accepted

Where do extra planes come from?

In my experience, having permanent airplanes standing by as spares does not really happen. Based on historical data potential realtime spares, airplanes with potential availability on any given day, ...
  • 20.9k
25 votes
Accepted

How is metal fatigue detected in an aircraft?

How do the engineers, maintenance team, etc know if an aircraft has metal fatigue? First of all, is not an "aircraft" that has fatigue, but a component. To the naked eye, there is no way to detect ...
  • 31.6k
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 ...
  • 34.4k
24 votes
Accepted

What are these aircraft at AMARG? Why are they dismantled this way?

Some B-52s and other aircraft were put out of commission as part of the START treaties. They were dismantled in such a way that the Russians could verify this with satellite reconnaissance, just as ...
  • 30.9k
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 ...
  • 479

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