Critical Engine on 747/A340

[Alan Partridge!]

Any guys out there who can help me with this question. I have an understanding of what the critical engine on the prop plane is such, but what on a multi jet plane? Is it systems related? Any thoughts?

[mutt]

For the purpose of certification, there isnt one! From the flying aspect it depends on the crosswind.

Mutt

[Captain Airclues]

Alan

Go to 'search'. Enter the word 'critical'. Select 'Titles only' and select 'Tech Log' and you will find many previous discussions on this topic.

Airclues

[Trentino]

There is no real critical engine on a ducted engine because there is no real thrust line like on a prop.
There is a critical engine however on the aircraft you mentioned.
The critical engine is located on the upwind wing on a crosswind takeoff and landing.
On a crosswind an aircraft tends to weathervain into the wind, now imagine losing an engine on that side. Its going to be uglier than losing the engine on the downwind side of the crosswind

Hope it helps.

[MrBernoulli]

Trentino,

Please, it is 'weather vane' not 'vain'.

[barit1]

An outboard engine will always be more critical than an inboard because the yawing moment is greater, thus greater trim drag.

(If a tri-jet loses a center engine, for example, there is no yaw moment.)

Now that I think about it, if a DC-10 or MD-11 loses #2 (with its thrust line well above the Cd), there must be a noticeable nose-up reaction, but still no yaw.

[Techman]

But the you got the light......................

[denkraai]

Barit1

You're correct.The MD11 pitches up like crazy when #2 fails.This effect can ruin your day when flying close to max. flight level.:hmm:

[Vetical Limit]

MrBernoulli

Thanks for that great contribution, glad to see that all is right in the world again after correcting Trentino's gross indiscretion.

Oh, and please shouldn't MrBernoulli be two words i.e. Mr Bernoulli...

[MrBernoulli]

Vetical Limit,

You're absolutely right! It was stated as a bit of banter, tongue in cheek, etc. No harm or offence intended.:ok:

"Vetical Limit" - what does that name mean exactly? Or should it be Vertical Limit?;)

[Trentino]

Vane Vane Vane Vane....im sorry, I shall never sin like this again....HEHE...brings me back to bein a young'n in private school
:)

Getting back to the topic at hand..with all the above being said It would really ruin ones day if their outboard upwind engine failed during a stiff crosswind at MTOW

[john_tullamarine]

.. on the contrary, the MTOW case generally is not limiting ... now consider the min weight Vmcg-limited case ... and you are off the runway in all likelihood with a decent crosswind.


Depending on the aircraft the effect of wind on the "real" Vmcg on the day can be in excess of 1kt/kt. If you have, say, a 35 kt crosswind from the "wrong" side ... you are in for an interesting ride. The only option may well be to reject above V1 to stay on the runway.

The main reason we like to see this topic come up is to cause folk to consider the options before pushing up the levers ... do we have the option of using a higher speed schedule ... can we delay until the main wind goes through etc ...

[Vetical Limit]

Guess i left myself open for that one, MrBernoulli...:)

Don't want to clog up this discussion with an explanation of the intended misspelling, just a personal joke. ;)