Why don't commercial passenger jets tuck their engines into the fuselage? (jet, training)
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I would think it would be a lot more efficient aerodynamically than to have those two or four jets hanging out on the wing. Would there much aerodynamical advantage to doing this?
Or would it make it too hard to maintain the jets or compromise things like luggage space if they put them in the fuselage?
On military aircraft, the engines are buried in the fuselage to minimize radar reflection. Also the wing is much nearer the ground than on commercial aircraft..
Placing the engines underneath the wings on commercial airliners helps to stabilize the wing which would otherwise flutter. It also allows the wing to be made of a much lighter material.
Other factors include reducing the noise in the cabin and of course, ease of maintenance.
In addition, an engine mounted inside either the fuselage, or the wing could cause significant damage to the aircraft if it were to explode.
However, having the engines mounted beneath the wings means that they're more susceptable to foreign object damage such as in the case of a bird strike.
Also, in the event of an emergency landing on water, the engines will increase the load on the wing and could cause it to snap off, possibly hitting the fuselage or even destroying the aircraft.
Fortunately, water landings are few and far between.
"Flying with the British airline company BOAC, the De Havilland DH-106 Comet 1 became the world's first passenger jet aircraft in May 1952. Note the unique placement of the jet engines inside the wings; a detail on commercial aircraft only seen elsewhere* on the Tupolev 104 (Tu-104)”
"Flying with the British airline company BOAC, the De Havilland DH-106 Comet 1 became the world's first passenger jet aircraft in May 1952. Note the unique placement of the jet engines inside the wings; a detail on commercial aircraft only seen elsewhere* on the Tupolev 104 (Tu-104)”
Not all military aircraft bury their engines. In the case of a single-engine fighter it makes sense, same for a two-engine fighter. The high-bypass turbofans of today are too large in diameter to place inside; an example is the A-10, which has external engines for a number of reasons, including frontal area of the fan. Others over the years: B-45, B-47, B-52, B-58, S-3, all cargo jets, even the XB-70 and B-1 have podded engines.
There are disadvantages to internal engines, including maintenance, and as previously mentioned if one engine cuts loose it often takes the other(s) with it if they're mounted in close proximity (my pilot training base lost a T-38 in that scenario).
The "jet" turbine itself doesn't create a lot of thrust. Most of the thrust of a modern airliner comes from the fan in front of the turbine. These fans are, on long haul aircraft well over 9' in diameter. There's simply no space.
You can see the size of the fan in relation to the actual turbine itself below.
Military planes use much much smaller fans that are designed for much higher speeds that are much less fuel efficient.
Thanks for the info guys! It was just something I had wondered when I looked at commercial planes, I figured there had to be an answer, I just didn't know why.
Internal engines can be a real problem if one has to make a belly landing. In one of the early test flights of the first (and surviving) XB-70, the gear failed to lower but a belly landing was out of the question due to engine placement. That problem was solved by one of the pilots crawling back into the guts and repairing the circuit.
Keep in mind that with many military jets, one has an ejection seat as an alternative.
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