Engine-out procedures and eccentric forces on engine pylons

Long ago it occurred to me that a twin-engine jet running with one engine out
might be putting tremendous eccentric stress on the plyon and mounting of the
running engine (meaning stress not aligned with the normal thrust vector of
the engine). Today it occurred to me that this might not be true if the
pilots adjust the attitude of the aircraft so that it is flying straight
forward. The adjustments would create opposing forces that not only keep the
aircraft in level flight but also realign the stress on the running engine, as
if there were still two engines and symmetric forces on the pylons.

Does this make sense? If so, are there limits to how far an aircraft can fly
out of trim in such a way as to put unusual stress on engine pylons (even with
all engines running). For example, does yawing sharply in a large jet put
unacceptable stress on the pylons?

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Mxsmanic wrote
For example, does yawing
sharply in a large jet put unacceptable stress on the pylons?

You should see what those pylons do in heavy turbulence!
The only stress is on the pilot who looks at them. :-)

Bob Moore

"Bob Moore" wrote...

You should see what those pylons do in heavy turbulence!
The only stress is on the pilot who looks at them. :-)

My wife and I were on a flight a few years back in an A300 IIRC and we were
in seats that gave us a clear view of the engine on the left wing. I was
casually looking out at it when I noticed that it was oscillating back and
forth quite noticeably and considerably, and we were only in light chop at
the time. My first impression was HOLY #$%&! quickly followed by the
realization that since it hadn't come off yet it must be normal.

Judging by how much it was moving around you would have thought it was held
on with bungee cords.

BDS

BDS wrote
Judging by how much it was moving around you would have thought it was
held on with bungee cords.

Nope! Back in my B-707 days, the engine was attached to the pylon
with just three bolts about the size of your forefinger, and each of
these bolts was designed to break-away and release the engine before
it could do damage to the wing.

Bob Moore

Bob Moore writes:

Nope! Back in my B-707 days, the engine was attached to the pylon
with just three bolts about the size of your forefinger, and each of
these bolts was designed to break-away and release the engine before
it could do damage to the wing.

Well, that's certainly reassuring.

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On 23 May, 17:04, Mxsmanic wrote:
Bob Moore writes:
Nope! Back in my B-707 days, the engine was attached to the pylon
with just three bolts about the size of your forefinger, and each of
these bolts was designed to break-away and release the engine before
it could do damage to the wing.

Well, that's certainly reassuring.


Why, what's it matter to you, you don't fly anyway.


Bertie

On May 23, 12:04 pm, Mxsmanic wrote:
Bob Moore writes:
Nope! Back in my B-707 days, the engine was attached to the pylon
with just three bolts about the size of your forefinger, and each of
these bolts was designed to break-away and release the engine before
it could do damage to the wing.

Well, that's certainly reassuring.

Not necessarily. Although it was admittedly caused by maintenance
crew abuse, don't forget the Chicago DC-10 accident, where the engine
came off and caused the deadliest accidental crash in US history.

http://en.wikipedia.org/wiki/America...nes_Flight_191

BDS wrote:
"Bob Moore" wrote...


You should see what those pylons do in heavy turbulence!
The only stress is on the pilot who looks at them. :-)


My wife and I were on a flight a few years back in an A300 IIRC and we were
in seats that gave us a clear view of the engine on the left wing. I was
casually looking out at it when I noticed that it was oscillating back and
forth quite noticeably and considerably, and we were only in light chop at
the time. My first impression was HOLY #$%&! quickly followed by the
realization that since it hadn't come off yet it must be normal.

Judging by how much it was moving around you would have thought it was held
on with bungee cords.

BDS



I love the window seat, but dammit, I cannot look at the wing
ever. "Ok, if it didn't flex like that, it would be brittle
and snap. It's supposed to bounce, it's not supposed to break"

But nothing reassures me.

Erik wrote:
I love the window seat, but dammit, I cannot look at the wing
ever. "Ok, if it didn't flex like that, it would be brittle
and snap. It's supposed to bounce, it's not supposed to break"

But nothing reassures me.


I find it helps in cases like these to watch a few videos of wing
loading tests, so you can see really just *how* far those wings can go
before breaking.

http://www.youtube.com/watch?v=6Uo0C01Fwb8

TheSmokingGnu

TheSmokingGnu wrote:
Erik wrote:

I love the window seat, but dammit, I cannot look at the wing
ever. "Ok, if it didn't flex like that, it would be brittle
and snap. It's supposed to bounce, it's not supposed to break"

But nothing reassures me.


I find it helps in cases like these to watch a few videos of wing
loading tests, so you can see really just *how* far those wings can go
before breaking.

http://www.youtube.com/watch?v=6Uo0C01Fwb8

TheSmokingGnu

Holy crap. I thought the two to three foot deflection
I've seen was a lot. I had no idea that you could turn
an airplane into a U.