130
votes
Accepted
Why do we need to starve the engine before turning it off?
The reason is the large spinning thing on the front. Residual fuel in the engine has been known to auto-ignite (i.e. combust without a spark), causing the prop to spin, causing serious injuries and ...
- 52.8k
85
votes
Accepted
Could a Dyson fan scale up to be used as a bladeless aircraft engine?
No. Not a useful propulsion engine.
The first problem is power. The air stream from Dyson's fans is weaker than what you can get from a conventional fan the same size, and jet engines need a very ...
- 22.6k
76
votes
Accepted
Should the helicopter be washed after any sea mission?
The helicopter shown is an Anti-Submarine Warfare Helicopter. ASW helicopters generally have the ability to detect submarines either Passively or Actively. Passively, sonar-buoys are dropped into the ...
- 1,166
60
votes
Accepted
What's wrong in this engine test cell picture from the book 'Ignition'?
I think there's a mix-up in the labeling of the photo.
Here's the photo and caption from a copy of "Ignition" that I just downloaded:
Here's the photo and caption from the next page:
Seen together, ...
- 618
54
votes
Which manufacturer produced this fan blade?
GE Aviation
Clue 1. Parts designed at the Lynn MA plant have part numbers of the form xxxxTxxPxx, where x is a digit. 4922T12P01 fits that pattern.
The gr.in is another clue. That refers to a ...
- 5,463
52
votes
What are the least powerful airplanes that ever flew?
There are a number of human-powered aircraft (list here). For the Gossamer Albatross, we have
In still air, the required power was on the order of 300 W (0.40 hp),
though even mild turbulence ...
- 3,219
49
votes
What is the rationale for single engine military aircraft?
Because single engine fighters are substantially cheaper to purchase and operate. Exact figures are hard to obtain, but as an example, an F-15 squadron will spend about 25,000 USD per flight hour ...
- 71.9k
47
votes
Why don't airplane piston engines have mufflers?
Today, most GA aircraft in Europe do have mufflers so they can pass the ever more stringent noise requirements. Here is one mounted to a Cessna 172 (picture source):
Historically, mufflers were ...
- 228k
47
votes
Why then don't aircraft fly even higher, for even greater efficiency?
Some do (or have in the past) but very high altitudes present their own issues. Historically the Concorde cruised anywhere from FL550 to FL600 and was actually allowed to climb and descend at its ...
- 100k
44
votes
Accepted
What is the significance of 104% for throttle power and rotor speed?
This happens when the maximum output was changed after design.
100% is simply a reference to a certain value. In the space shuttle's case, the engine output was increased after the initial design. ...
- 39.6k
42
votes
Accepted
What are the most powerful airplanes that ever flew?
Most thrust overall?
Well the most powerful aviation gas turbine to date is the GE90-115B, producing a whopping 115,000 lbs of thrust per engine at maximum static thrust settings.
Overall the ...
- 71.9k
41
votes
What is a rubber engine?
A rubber engine is not to be confused with a rubber motor (a rubber band which is twisted in order to store energy which can be released when the rubber band untwists. This type of engine is good for ...
- 228k
41
votes
Accepted
Is it allowed to let the engine of an aircraft idle without a pilot in the plane. (For both helicopters and aeroplanes)
You won't see it done in the fixed wing world unless the aircraft is tied down or otherwise securely restrained (like when you tie off the tail to something when hand starting your no-starter ...
- 125k
39
votes
Why do we need to starve the engine before turning it off?
Combustion in a gasoline internal combustion engine for most aircraft, requires four things: fuel, oxygen, compression and ignition.
If the engine is starved of fuel, accidental combustion (and an ...
- 17.7k
37
votes
Accepted
Can hydrogen gas be an alternative fuel source for a gas turbine engine?
Yes, and it has been demonstrated 30 years ago on the Tupolev 155. This is/was a hydrogen-powered version of the Russian Tu-154B tri-jet. Only one has been built and has since been retired after ...
- 228k
36
votes
Accepted
What is the rationale for single engine military aircraft?
Fighters don't carry passengers.
The figure of merit for combat aircraft isn't passenger-miles flown between accidents, it's objectives completed (like enemy targets destroyed) per billion dollars ...
- 22.6k
35
votes
Accepted
Why do new engines have a case with a triangular tiling pattern?
This type of structure is called isogrid structure. Solid walls are usually very heavy and therefore engineers use more weight-efficient structures such as sandwich structures or stiffened structures ...
- 4,282
34
votes
Does a 120cc engine burn 120cc of fuel a minute?
This is possible, but still quite extreme fuel consumption.
120ml == 120cc gasoline are ~90g by mass
90g gasoline need about 1320g air in order to fully combust
1320g air are about 1.08 cubic meters ...
- 1,172
33
votes
Accepted
Can you identify this engine?
It appears to be a Rolls Royce Viper turbo jet engine made in 1966. The maker's mark (BSB) derives from Bristol Siddeley, formed from Armstrong Siddeley (the company that originally developed the ...
- 3,606
32
votes
Accepted
Why is the front part of the engine not painted?
The engine inlet lip is bare metal to facilitate anti-icing. The area is heated from within using hot engine bleed air.
This partial schematic (from Boeing AERO QTR_01.12) shows the engine anti-ice ...
- 3,113
32
votes
Why are all engines identical in typical commercial airplanes?
Engines don't fail, on average. And if they do, it's a very low probability that two engines will fail at the same time.
Modern jet engines are extremely reliable, with failure rates on the order of ...
- 1,526
31
votes
Is the bleed air passengers breathe tapped from the engines before or after it comes in contact with fuel? And why? Isn't this unhealthy?
The bleed will be tapped from one or two of the 3rd, 4th, 5th or 6th High Pressure Compressor stages. Usually there are two bleed ports. The highest pressure port will supply really hot air for ...
- 125k
29
votes
Does the cannon of the A-10 deliver more thrust than the engines do?
The A-10 uses a GAU-8/A. According to Wikipedia:
The average recoil force of the GAU-8/A is 10,000 pounds-force (45
kN), which is slightly more than the output of one of the A-10's two
TF34 ...
- 4,282
29
votes
How can an Airbus Beluga fly only with two engines and use short runways?
This airplane is based on the Airbus A300-600. The maximum take-off weight of the aircraft is 155 tonne as published in the wikipedia. In addition, the the manufacturer has published the Aircraft ...
- 994
29
votes
Accepted
What are the benefits of mounting an engine above the fuselage?
It's strictly to stay clear of spray in seaplanes, or because the engine was tacked on as an afterthought for some reason (like a motorglider conversion) and that was the only place to put it.
There ...
- 125k
28
votes
Accepted
What's the use of so much torque on propellers?
Even small 1 hp electrical motors can achieve that RPM
Yes, but can it sustain that RPM when something tries to stop it, that is the question. 1 hp combustion engines can get to 2700 rpm as well, but ...
- 61.2k
28
votes
Which manufacturer produced this fan blade?
That looks very much like a TF-34 fan blade. The TF-34 is used on the A-10 Thunderbolt and S-3B Viking. The root style is known as "pinned" or "clevis". You can see a blade being pinned into the rotor ...
- 3,751
27
votes
Why do new engines have a case with a triangular tiling pattern?
This is simply a way to achieve required rigidity/strength and vibration dampening with less material than in a solid, even thickness design.
Varying the weave pattern gives a relatively easy and a ...
- 26.8k
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