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Least Number Of Engines Can A B777/B767 Fly On?  
User currently offlineB773A346 From United States of America, joined Feb 2008, 77 posts, RR: 0
Posted (6 years 6 months 2 weeks 3 days 14 hours ago) and read 4195 times:

I was wondering if the Boeing 747 can complete an entire journey without turning on all 4 engines and using only 2 or 3 engines all the time, and one engine for the B767 and B777. Is it safe though ?

20 replies: All unread, jump to last
 
User currently offlineBAKJet From United States of America, joined Nov 2007, 744 posts, RR: 0
Reply 1, posted (6 years 6 months 2 weeks 3 days 14 hours ago) and read 4181 times:



Quoting B773A346 (Thread starter):
was wondering if the Boeing 747 can complete an entire journey without turning on all 4 engines and using only 2 or 3 engines all the time

I think a BA 744 fly on 3 engines LAX-LHR(maybe it ended up landing in SNN). Although, I think it was because of and engine failure.


User currently offlineRwy04LGA From United States of America, joined Jul 2005, 3176 posts, RR: 8
Reply 2, posted (6 years 6 months 2 weeks 3 days 14 hours ago) and read 4163 times:

Zero! Any plane could still fly, just not maintain altitude (Space Shuttle). But, obviously, the answer is one, even a 4-holer.

And the word is 'LEAST'



Just accept that some days, you're the pigeon, and other days the statue
User currently onlineStitch From United States of America, joined Jul 2005, 30889 posts, RR: 87
Reply 3, posted (6 years 6 months 2 weeks 3 days 14 hours ago) and read 4162 times:
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A four-engined plane can complete her mission on three, but if they lost two, I'm pretty sure they'd need to divert.

A two-engined plane needs to divert once it drops an engine.


User currently offlineViscount724 From Switzerland, joined Oct 2006, 25125 posts, RR: 22
Reply 4, posted (6 years 6 months 2 weeks 3 days 13 hours ago) and read 4126 times:



Quoting Stitch (Reply 3):
A four-engined plane can complete her mission on three, but if they lost two, I'm pretty sure they'd need to divert.

Three and four engine aircraft are also permitted to make ferry flights with one engine out under certain conditions (obviously with only the crew aboard) to get an aircraft to a maintenance base.


User currently offlineAvioniker From United States of America, joined Dec 2001, 1109 posts, RR: 11
Reply 5, posted (6 years 6 months 2 weeks 3 days 12 hours ago) and read 4119 times:

Many 747 operators leave it up to the captain to continue or divert if an engine is lost after departure.
My favorite is the BA 747 that lost an engine after departing LAX and continued on to LHR landing only slightly late. The crew apparently didn't even consider returning to LAX or diverting and BA didn't think much of it either; at least until the press panic artists got hold of it. . .  Silly

 Smile



One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
User currently offlineCitationJet From United States of America, joined Mar 2003, 2433 posts, RR: 3
Reply 6, posted (6 years 6 months 2 weeks 3 days 12 hours ago) and read 4106 times:



Quoting Viscount724 (Reply 4):
Three and four engine aircraft are also permitted to make ferry flights with one engine out under certain conditions

And also one engine OFF.........


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User currently offlineThesorcerer From United Kingdom, joined Oct 2005, 1048 posts, RR: 0
Reply 7, posted (6 years 6 months 2 weeks 3 days 11 hours ago) and read 4100 times:



Quoting CitationJet (Reply 6):

Would this not affect the aerodynamic properties of the aircraft? I mean in terms of less drag on the one side than on the other. Could this be corrected simply by adjusting the rudder trim?

Dom



ALITALIA,All Landings In Torino, All Luggage In Athens ;)
User currently offlineAvioniker From United States of America, joined Dec 2001, 1109 posts, RR: 11
Reply 8, posted (6 years 6 months 2 weeks 3 days 11 hours ago) and read 4096 times:

The answer is a simple yes and yes.

Quoting Thesorcerer (Reply 7):
Would this not affect the aerodynamic properties of the aircraft? I mean in terms of less drag on the one side than on the other. Could this be corrected simply by adjusting the rudder trim?

That's normal procedure on a three engine ferry. With the engine off there's less offset rudder trim required.

 Smile



One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
User currently onlineStarlionblue From Greenland, joined Feb 2004, 17019 posts, RR: 67
Reply 9, posted (6 years 6 months 2 weeks 3 days 9 hours ago) and read 4055 times:



Quoting B773A346 (Thread starter):
I was wondering if the Boeing 747 can complete an entire journey without turning on all 4 engines and using only 2 or 3 engines all the time, and one engine for the B767 and B777. Is it safe though ?

Do you mean that they should turn off an engine or two for some reason?


As for the answer, it has been given above.
- Quad can remain aloft on two or three. Two requires a diversion.
- Twin can remain aloft on one. This requires a diversion.

The time aloft is dependent on the amount of fuel. Note also a twin on one engine cruises slower.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineXXXX10 From United Kingdom, joined Jan 2000, 777 posts, RR: 0
Reply 10, posted (6 years 6 months 2 weeks 2 days 16 hours ago) and read 3966 times:



Quoting Avioniker (Reply 5):
Many 747 operators leave it up to the captain to continue or divert if an engine is lost after departure.
My favorite is the BA 747 that lost an engine after departing LAX and continued on to LHR landing only slightly late. The crew apparently didn't even consider returning to LAX or diverting and BA didn't think much of it either; at least until the press panic artists got hold of it. . .

To be fair there is no evidence that they 'did not consider diverting'. I believe the crew contacted ops for advice and were told that it was up to the captain.

The aircraft diverted to MAN as they were unable to use all of the fuel that they had.

There was an AAIB report which IIRC did not criticize the crew for not landing earlier.


User currently offlineViscount724 From Switzerland, joined Oct 2006, 25125 posts, RR: 22
Reply 11, posted (6 years 6 months 2 weeks 2 days 15 hours ago) and read 3925 times:



Quoting XXXX10 (Reply 10):
To be fair there is no evidence that they 'did not consider diverting'. I believe the crew contacted ops for advice and were told that it was up to the captain.

The aircraft diverted to MAN as they were unable to use all of the fuel that they had.

There was an AAIB report which IIRC did not criticize the crew for not landing earlier.

The AAIB report on the BA incident:
http://www.aaib.dft.gov.uk/sites/aai...ng%20747-436,%20G-BNLG%2006-06.pdf


User currently offlineThegeek From Australia, joined Nov 2007, 2638 posts, RR: 0
Reply 12, posted (6 years 6 months 2 weeks 2 days 14 hours ago) and read 3895 times:



Quoting Stitch (Reply 3):
A four-engined plane can complete her mission on three, but if they lost two, I'm pretty sure they'd need to divert.

If a four engine plane were light enough, could it maintain level flight at a lower altitude on one engine? If so, they could continue even on two.


User currently onlineStarlionblue From Greenland, joined Feb 2004, 17019 posts, RR: 67
Reply 13, posted (6 years 6 months 2 weeks 2 days 8 hours ago) and read 3843 times:



Quoting Thegeek (Reply 12):
If a four engine plane were light enough, could it maintain level flight at a lower altitude on one engine? If so, they could continue even on two.

That would depend on the weight.

However:
- I don't know the two engine cruise speed of a typical quad, but I wager it's not too hot. So you might not get where you're going anyway. In other words, divert.
- If a quad lost two, that would be a pretty strong indication of a possible fault independent of the engines. Would you want to continue?  Wink



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineThegeek From Australia, joined Nov 2007, 2638 posts, RR: 0
Reply 14, posted (6 years 6 months 2 weeks 2 days 7 hours ago) and read 3825 times:



Quoting Starlionblue (Reply 13):
- If a quad lost two, that would be a pretty strong indication of a possible fault independent of the engines. Would you want to continue?

Good point.


User currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 15, posted (6 years 6 months 2 weeks 2 days 4 hours ago) and read 3788 times:

Depending on the AUW of the Aircraft at the time of IFSD.
The B767 & B777 should be able to continue its journey on one Functioning power plant

regds
MEL



Think of the brighter side!
User currently offlineDavid L From United Kingdom, joined May 1999, 9524 posts, RR: 42
Reply 16, posted (6 years 6 months 2 weeks 2 days 4 hours ago) and read 3781 times:



Quoting B773A346 (Thread starter):
without turning on all 4 engines

I'm pretty sure thery're not allowed to deliberately take off with one engine not operating unless it's under the special conditions of a ferry flight, as mentioned above. Continuing when an engine fails after take-off is another matter.

Quoting XXXX10 (Reply 10):
To be fair there is no evidence that they 'did not consider diverting'.

 checkmark  I'd go further than that. I'd say there's plenty of evidence that they definitely did consider diverting and continued to do so throughout the flight.


User currently offlineFrancoflier From France, joined Oct 2001, 3741 posts, RR: 11
Reply 17, posted (6 years 6 months 1 week 6 days ago) and read 3474 times:

Every airline operating quads has specific guidelines in its ops manual regarding engine failures enroute for the pilots to follow.

Usually, it'll say that to continue to destination (or to a diversion airport a little more hospitable than a semi-deserted military airbase in Siberia) you need:

- Certain weather conditions at the planned destination
- Terrain clearance for the 2 engines scenario for the remainder of the flight
- Depressurization scenario fuel considerations for the remainder of the flight
- A certain amount of fuel upon arrival at the planned destination airport, and ultimately,
- The commander's satisfaction that the plane is safe to fly to the planned destination.

It varies from airline to airline, obviously, and depends on local regulations.

To give an idea of 1 engine inop performance on a quad, a 744 will burn around 10 to 15% more fuel on 3 engines than on 4. It'll usually have to descend around 2000 to 4000 feet below its optimum cruise altitude. It would usually be able to make it to destination within the above mentioned guidelines from an IFSD occurring around 1/3 to 1/2 of the way to that destination on a typical 12 hours flight, or even from earlier on in some cases. speed and time loss would be relatively marginal.
It all depends on weight and fuel on board, sector lenght, company fuel policy, weather, etc, of course....


When it comes to twin, I don't know of any airline/country regulations that would allow it to continue anywhere other than to the closest suitable airport when in a engine out scenario...
Whether it could physically do it is another question, and it would largely depend on altitude/speed loss and increase in fuel burn, which will obviously be much greater than for a quad.



Looks like I picked the wrong week to quit posting...
User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 18, posted (6 years 6 months 1 week 5 days 21 hours ago) and read 3438 times:



Quoting CitationJet (Reply 6):

Is that one of Kalittas'?


User currently offlineKELPkid From United States of America, joined Nov 2005, 6370 posts, RR: 3
Reply 19, posted (6 years 6 months 1 week 5 days 19 hours ago) and read 3397 times:

Any of them can still fly with no working engines  Smile Just don't stall...but you will for sure be descending. Best to trim for the best rate-of-glide airspeed at that point...and picking out a landing site  Wink The Gimli and Azores gliders both proved this.


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineFlyUSCG From United States of America, joined Jun 2006, 656 posts, RR: 0
Reply 20, posted (6 years 6 months 4 days 15 hours ago) and read 3057 times:



Quoting Avioniker (Reply 5):
My favorite is the BA 747 that lost an engine after departing LAX and continued on to LHR landing only slightly late.

It actually didn't make it to LHR due to lack of fuel and headwinds etc... I think thats why it got so much negative press (and rightfully so).



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