Engine Mount

[Bubblehead]

Is it true that wing mounted jet engines are held by shear pin/s so that in the event of a serious rotor imbalance the affected engine is designed to fall off to prevent damage to the wing.

Bubblehead

[beaky]

I doubt it- it'd be less hazardous to shut it down before things got to that point. I can't see having a manually-operated release to drop an engine to prevent the worst-case vibration scenario, which would mean... dropping an engine. Doesn't make sense. And if you're talking about a passive release system, similar logic applies: you'd want that engine to stay put as long as possible.
Airliners have landed successfully after losing an entire engine, but not every time it's happened... sometimes the unit will still be generating enough thrust to take it up over the leading edge of the wing- this could be a problem, obviously.

[Jakemaster]

I seriously doubt it.  A sheer pin would be a lot easier to break or fall out if you were flying in rough conditions.  Also, dropping an engine would be a bad idea.  Heres why: Engines are very heavy, dropping one would cause an extreme imbalance, and the plane would become impossible to control.  Ever flown with one engine? Even the lack of power makes it very defficult to control, throw in a weight change and you're screwed.  Also, do you have any Idea how much damage a Jet engine dropped from altitude would cause?  Some impact craters are made by items smaller than jet engines (grant it they are fallin faster).  

So the answer to your question is no.  Now, Jet engines are held in place by a few pins, they basically just hang there

[Bubblehead]

What you guys said make a lot of sense. A couple more questions however.

1.  How long before an engine running at full speed come to a complete stop after being shut down.

2.  Have you ever seen a rotating element such as the jet rotor suffer an imbalance while running at full speed?

The reason I have asked these questions was because I had substantial training in noise and vibration analysis while in the Navy and I've seen what it would do to a gas turbine engine if it suffers an imbalance condition. It literally self distructs.

Thanks.

Bubblehead

[elite marksman]

#1, it depends. If I took an old rust jet thats been in storage for 50 years it will stop pretty quick(assuming I can even get her going), but if I took a brand new turbine out of Pratt & Whitney's factory it would take a couple of minutes. It all depends on how well and often the mechanics lubed the engine.

#2 In person, no, but while my brother was training to be a mechanic somebody gave him a video of an engine that had not been maintained correctly in a while and had serious metal fatiuge, It was running up on the ground when a blade came off. He showed it to me, wasn't pretty, certaintly not what you want to happen in flight.

[Craig.]

Engines falling off inflight have caused some serious accidents, I believe the DC10 crash in Chicago was caused by an engine which fell off. However they are designed to rip off in the event of a crash landing in water and on the ground.

[Fly2e]

New technology from BAE Systems....

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[Fly2e]

or you could replace an engine and use the wrong rivets!!!

AIRCRAFT taking off from Manchester Airport could have crashed into part of a jumbo jet engine which had fallen on to the runway.

A disturbing report by aviation inspectors published today blamed the incident on the standard of maintenance on the Pakistan International Airlines Boeing 747, which was carrying 303 passengers.

Another report on a separate incident revealed bosses at Manchester had adopted new docking procedures after a jet which was trying to park beside a terminal building crashed into an air bridge which was left in the wrong position.

No one was hurt in either incident, but government inspectors made a series of recommendations.

The standard of maintenance on the PIA jumbo was severely criticised after a large part of one of its four engines sheared off shortly after it landed after flying in from New York.

The pilot of another jet who saw it fall off alerted air traffic controllers who stopped other aircraft from landing while the debris was cleared.

Debris

A report by the Air Accident Investigation Branch said: ". . . in less favourable circumstances, an aircraft taking off on the same runway, shortly afterwards, could have been at risk of colliding with the debris on the runway at a critical time."

The report slammed the standard of maintenance after inspectors found the wrong rivets had been used and work was not recorded.

The report said: "It would appear that the rivets . . . were replaced without any reference to a manual or understanding of their purpose. It also seems that the installer . . . considered them so unimportant that their installation was not recorded or mentioned."

Inspectors also recommended more rigorous maintenance routines after the incident in 2002.

Manchester has adopted new docking procedures after a jet which was trying to park beside a terminal building crashed into an air bridge.

The left-hand engine of an Air Transat Airbus A310 which had just landed from Toronto, with 255 passengers on board, was severely damaged, according to the report.

A technical problem had left the air-bridge - used by passengers to get on and off the plane - in the wrong position.

An airport spokesman said: "We have worked closely with the AAIB throughout their investigations and as reported in their recommendations, we are changing our procedures accordingly."

[legoalex2000]

Engines falling off inflight have caused some serious accidents, I believe the DC10 crash in Chicago was caused by an engine which fell off. However they are designed to rip off in the event of a crash landing in water and on the ground.

a cessna c172 crashed into the DC-10's left engine.

i wouldn't think that the shear pin thing would be a good idea.with terrorists, all is made easier for the plane to crash with something like this. all you need is the smallest device to disable the manual pin operation or on the pin itself, and bam (and literally BAM!) engine's away and aircraft out of control.

Ramos

[Craig.]

Just remember that was before the flight and weakend the joints.

[gryshnak]

Engines falling off inflight have caused some serious accidents, I believe the DC10 crash in Chicago was caused by an engine which fell off. However they are designed to rip off in the event of a crash landing in water and on the ground.

Some years ago on another forum I asked Don Stackhouse (a man with a great deal of aerodynamic experience) about fowler flaps, and part of his reply was this:

There was a rather graphic example at Chicago O'Hare airport a number of years ago of what happens when flaps become unrestrained. The DC-10 uses two shear pins to attach each wing engine, designed to fail and let the engine fall safely free of the aircraft if it locks up. Without this, the tremendous rotational inertia of the engine rotors could rip the engine out of the airplane, perhaps taking the pylon and parts of the wing spar with it. These forward pins, which normally carry most of the weight of the engine, have required inspections. There is a special (and somewhat time-consuming to install) fixture used to support the engine while the forward pin is pulled for inspection. Some of the mechanics were taking a shortcut, using a forklift and a strap instead of the fixture to support the engine. They didn't realize that in the process they were overstressing the rear pin, setting it up for a premature failure.

Just as the subject aircraft (with a full load of passengers) rotated on takeoff, the rear pin failed. Still producing takeoff thrust, the engine pivoted forward and upward around the forward shear pin, going up and over the top of the wing and taking all of the hydraulic lines that ran inside the leading edge of the wing with it. These lines supplied the flap actuators. Suddenly without hydraulic pressure to keep them open, all the flaps on that side of the airplane immediately RETRACTED.

With takeoff flaps still deployed on one wing, and zero flaps on the other, the ailerons were hopelessly overwhelmed by the massive difference in lift between the two wings. The airplane immediately and inexorably rolled toward the flapless wing, carving a long, deep furrow in the ground with its wingtip before finally impacting nose-down and nearly inverted. There were no survivors. The missing engine, with its failed shear pins and some fragments of hydraulic lines, was found lying on the runway not far from the point of liftoff.

Gryshnak

[legoalex2000]

man i swear it was a plane collision....

[looks up on planecrashinfo.com]

http://www.planecrashinfo.com/w790525.htm

my apologies...

[looks for what i was talking about]

i have no idea what i was thinking... i thought i knew something about a cessna striking an aircraft...

whatever...ramos

[Craig.]

This case actually I believe was caused by a forklift collidiing with the engine when it was being fitted. Or something like that.

[Hagar]

Engines falling off inflight have caused some serious accidents, I believe the DC10 crash in Chicago was caused by an engine which fell off. However they are designed to rip off in the event of a crash landing in water and on the ground.

Here's an interesting report into that accident. This is also the one that Gryshnak referred to. Click Next to continue. http://lessons.air.mmac.faa.gov/l2/Am191/sum1a/

I could be wrong but seem to recall that the engines on some early transatlantic jet airliners could be jettisoned in an emergency. I thought this involved explosive bolts & it would usually only be contemplated over water. It would obviously only be practical on aircraft with the engines mounted in pods like the 707 & maybe even the 747.

[elite marksman]

I could have sworn that that was a MD-11 involved in that incident. Guess not.