probability of engine failure 747 v. 767

[Al Man]

You know the old joke about the Scotsman English and Irishman on the plane and all four engines fail - well statistically, ARE you safer crossing the Atlantic in a 747 than, for example, a 767 on the basis that a 747 has more engines??

Which kind of leads me to my next question: does the likelihood engine failure increase in line with the number of engines?

just a question that a relative of mine has thrown my way and i have no idea whatsoever and interested what everyone out there has to offer!!

Cheers
Al

[Notso Fantastic]

You're twice as likely to have an engine failure on a 747. But when you do, it is only a 'mild eyebrow' raiser rather than a 'Holy Mary, Mother of God!' event. You still have 3 more, and losing a second is just as unlikely unless there is a connected event. Losing one on a twin is a bit more traumatic. My outfit puts the same type of engine on 767s and 747s, and it improves the statistics by putting the best engines on the twin. Even so, engine failures are becoming incredibly rare events the condition monitoring and general reliability is so good now.

[yggorf]

Yeah. Too bad there is no civilian version of the B52.

[Lu Zuckerman]

Reliability, what's that?

To: yggorf

True the B-52 has a lot of engines per wing and it is very rare that all of them will shut down at the same time. However the B-52 has been known to shed a wing taking four of the engines with it.

[lomapaseo]

You're twice as likely to have an engine failure on a 747. But when you do, it is only a 'mild eyebrow' raiser rather than a 'Holy Mary, Mother of God!' event. You still have 3 more, and losing a second is just as unlikely unless there is a connected event. Losing one on a twin is a bit more traumatic.

If losing a second is twice as likely on a quad, why on earth would losing only one on a twin be so traumatic

[Intruder]

"If losing a second is twice as likely on a quad, why on earth would losing only one on a twin be so traumatic"


First, when you lose an engine on a 747, you lose 25% of available thrust, normal electrical generating capacity, and bleed air supply, vs 50% in a 767.

Second, if you lose a second engine in a 747, the airplane can still remain airborne in controlled, powered flight; where a 767 becomes an oversized glider.

[25F]

Oversized gliders... I can think ot three.
The Gimli glider, 1983:
http://www.wikipedia.org/wiki/Gimli_Glider
Air Transat, 2001:
http://www.airsafe.com/events/airlines/transat.htm
A BA 747 running into volcanic dust:
http://aviation-safety.net/database/...19820624-0.htm

And thanks to Google I've found a similar volcanic dust incident in 1989:
http://www.geo.mtu.edu/department/cl.../historic.html

[G-ALAN]

L Zuckerman

Shed a wing? You say they have been known to shed a wing, I'm just curious is it some kind of flaw in the B-52 airframe that makes them more likely do so?

I think it's a pilots worst nightmare to watch a wing drop off it doesn't even bear thinking about!