Engine-out procedures and eccentric forces on engine pylons

[Mxsmanic]

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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[Bob Moore]

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

[BDS[_2_]]

"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

[Bob Moore]

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

[Mxsmanic]

Bob Moore writes:

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

I've seen engine nacelles swaying merrily to and fro (along the wing axis) in
turbulence but I didn't know if twisting forces applied to the pylons would be
so easily tolerated.

As it is, modern pylons, so seemingly frail and so apparently inviting of very
concentrated stresses as they hold the engines way out in front of the wing,
always look like an invitation for trouble to me. But I suppose if they are
engineered properly they can hold, rather like that glass walkway that the
Havasupai recently built out over the Grand Canyon.

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[Mxsmanic]

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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[Erik]

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.

[TheSmokingGnu]

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

[Richard]

"Erik" > wrote in message
...
>
> 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 counting missing rivets and watching spinning rivets takes my mind
off the wing flex.

[muff528]

>
> I love the window seat, but dammit, I cannot look at the wing
> ever......

1971 - My very first airline ride -- Delta DC-9 Tampa to Atlanta
The wing looked very solid and very much "one with the airplane" --o--

30 minutes later - My second airline ride -- PanAm 747 Atlanta to LA
I coulda swore that the wings were flapping ~~o~~

I missed a lot of scenery :-)

TP

[Erik]

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.

[Bertie the Bunyip[_2_]]

Mxsmanic > wrote in
:

> 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?

Nope, pretty much the same as everythign else you post.


Bertie

[Bertie the Bunyip[_2_]]

Mxsmanic > wrote in
:

> Bob Moore writes:
>
>> You should see what those pylons do in heavy turbulence!
>> The only stress is on the pilot who looks at them. :-)
>
> I've seen engine nacelles swaying merrily to and fro (along the wing
> axis) in turbulence but I didn't know if twisting forces applied to
> the pylons would be so easily tolerated.

Fjukktard



Bertie

[tom laudato[_2_]]

I.m wondering if the engineering on wings has changed a bit. I worked for
an airline carrier in the early 60's and we took deliver of the first
boeing 727 built. the company provied us with a very similar video. Its
showed a 727 straped into a cradel and the wings were bent up similar to
what this utube shows..
Difference:
i watched the wings pushed up to where both tips touched each other many
many many times
there was not a failur and i do not remeber exactly how many times but it
was in the dozens. I wonder what the difference is that this wing breaks
after only one raise
tom
"Bertie the Bunyip" > wrote in message
.130...
> Mxsmanic > wrote in
> :
>
> > Bob Moore writes:
> >
> >> You should see what those pylons do in heavy turbulence!
> >> The only stress is on the pilot who looks at them. :-)
> >
> > I've seen engine nacelles swaying merrily to and fro (along the wing
> > axis) in turbulence but I didn't know if twisting forces applied to
> > the pylons would be so easily tolerated.
>
> Fjukktard
>
>
>
> Bertie

[Bertie the Bunyip]

On 24 May, 21:40, "tom laudato" <tommyann> wrote:
> I.m wondering if the engineering on wings has changed a bit. I worked for
> an airline carrier in the early 60's and we took deliver of the first
> boeing 727 built. the company provied us with a very similar video. Its
> showed a 727 straped into a cradel and the wings were bent up similar to
> what this utube shows..
> Difference:
> i watched the wings pushed up to where both tips touched each other many
> many many times
> there was not a failur and i do not remeber exactly how many times but it
> was in the dozens. I wonder what the difference is that this wing breaks
> after only one raise

Nope, essentially the same up to the point where they're sticking
Carbon fiber spars in, but the certification standards are the same.

A wing pylon will happily accept a consideraable load in just about
any flight attitude, what it won't accept is s sudden high G load such
as extreme turbulence or an abrupt engine stoppage might cause.
you won't break a wing off too easily, though.

Bertie

[Bertie the Bunyip]

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

[Kev]

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/American_Airlines_Flight_191

[muff528]

"Kev" > wrote in message
ups.com...
> 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/American_Airlines_Flight_191
>
>
Wow! this is spooky! (from the wiki article cited above)................

"The crash in Chicago remains the most deadly single-aircraft accident in
United States history. Another flight with the same number, Delta Air Lines
Flight 191, crashed at Dallas/Fort Worth International Airport in 1985. Most
recently, Delta Air Lines Flight 5191, operated by Comair as Flight 191,
crashed in 2006 killing 49 people. All three carriers have since retired the
flight number 191, as is currently customary after major accidents on most
airlines. In addition, Puerto Rican airline Prinair also had a fatal flight
numbered Flight 191. The only fatal X-15 crash was also Flight No. 191."

[Bertie the Bunyip]

On May 23, 5:11 pm, Erik > wrote:
> 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.-

Understandable. I'd feel the same way if I was you.


Bertie

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