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747 Taking Off On Two Engines ....  
User currently offlineCondor24 From United Kingdom, joined Mar 2004, 43 posts, RR: 0
Posted (8 years 7 months 2 weeks 4 days 6 hours ago) and read 13855 times:

I was discussing with a friend the 'psychological' benefit of 4 engines vs 2. I'm not in the aviation business and I have always felt safe on a 9 hour flight aboard a 777 or A330. The friend mentioned to me that he'd heard a 747 can take off on 2 engines and I wondered whether this also meant 2 port or 2 starboard engines. Any feedback would be appreciated & I'm sorry if this has been discussed in previous threads ... Condor.


'Condor, the span to fly'
22 replies: All unread, jump to last
 
User currently offlineWhiteHatter From , joined Dec 1969, posts, RR:
Reply 1, posted (8 years 7 months 2 weeks 4 days 6 hours ago) and read 13817 times:

Doubtful, although with zero payload and minimum fuel (like absolute minimum!) it could be attempted at somewhere like Edwards with that huge runway.

It can certainly take off with 3 engines (required performance) and continue to fly on just 2.

There is an amazing story, however, of an Eastern L-1011 which outdid even that. It was flying back to the USA from Mexico on two engines after one would not start at the gate, and EA arranged an empty ferry flight back for an engine swap.

On climbout a second engine failed. Somehow the crew managed to get it round a circuit and landed back at the airport on a single engine!


User currently offlineCruiser From Canada, joined Apr 2005, 1001 posts, RR: 7
Reply 2, posted (8 years 7 months 2 weeks 4 days 6 hours ago) and read 13759 times:

Quoting WhiteHatter (Reply 1):
On climbout a second engine failed. Somehow the crew managed to get it round a circuit and landed back at the airport on a single engine!

An AC A333 landed on just one engine about two weeks ago in KEF. I am not sure how long they flew on the one engine!

That said, there was a thread on this exact topic a while back. I seem to recall that a while back, either a 747 or A340 lost two engines on the same wing in flight. It was able to get to wherever it had to and landed safely. The way I see it, I don't care how many engines are under the wing. If there are four engines on a plane, and one dies, then it puts a greater strain on the other three, and I think that it is MORE likely to have another engine failure. Especially out over the ocean. That said, I also realise that the two holer also faces the same problem. However, because I think people are much more comforted by the fact that they still have three engines, they start doing stupid things. Like the BA 747's last year. If it were a twin, then it would land at the nearest possible place. Either way, I see it that I have as good a chance on a 4-holer, or a 2-holer.

James



Leahy on Per Seat Costs: "Have you seen the B-2 fly-by at almost US$1bn a copy? It has only 2 seats!"
User currently offlineWhiteHatter From , joined Dec 1969, posts, RR:
Reply 3, posted (8 years 7 months 2 weeks 4 days 6 hours ago) and read 13679 times:

Quoting Cruiser (Reply 2):
If there are four engines on a plane, and one dies, then it puts a greater strain on the other three, and I think that it is MORE likely to have another engine failure.

not that simple.

The BAe Nimrod has 4 engines. It can shut two down and station-keep for many hours, flying on just two.

The engine-out rules cover takeoff power, loss of a single engine does not really affect an aircraft's remaining engines when cruising beyond a slightly higher cruise power setting to accomodate the drag from the rudder and shutoff engine. Certainly not to the stage where the remaining engines are being stressed as aircraft do not cruise with engines at their maximum thrust.

Even big twins can operate on a single engine at cruise as the extra power needed is still not the same as having to run the engine at takeoff power. However they are subject to the more stringent ETOPS rules as a single powerplant operating is always going to be more of a risk than three.


User currently offlineZeke From Hong Kong, joined Dec 2006, 8883 posts, RR: 75
Reply 4, posted (8 years 7 months 2 weeks 4 days 5 hours ago) and read 13615 times:

IMHO, takeoff on two - no way.

Can takeoff on three (as a no passenger/cargo ferry flight at light weight), and still survive if you suffer another loss.

Landing on two, possible, something you do in the sim on a regular basis.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineUal744 From United States of America, joined Aug 2005, 13 posts, RR: 0
Reply 5, posted (8 years 7 months 2 weeks 4 days 5 hours ago) and read 13482 times:

I have done it in the simulator with the 747-400. I cut both engines on the same side at the worst possible time on takeoff, and it depended on the weight. A max weight takeoff is 875,000 lbs. It seemed the plane could do it at a weight of about 750,000 or less. For fuel, this weight roughly translates to a 10 hour flight or less. As far as two engine landings, they are usually much more doable, and they are a normal maneuver that we practice in the simulator.

User currently offlineAirfoilsguy From , joined Dec 1969, posts, RR:
Reply 6, posted (8 years 7 months 2 weeks 4 days 5 hours ago) and read 13389 times:

Quoting Zeke (Reply 4):
Can takeoff on three (as a no passenger/cargo ferry flight at light weight), and still survive if you suffer another loss.

3 Engine flights are done sometimes.

View Large View Medium
Click here for bigger photo!

Photo © Norman Gage



Sometimes there are even 5 engine flights.

View Large View Medium
Click here for bigger photo!

Photo © Steve Ruttley



User currently offlineZeke From Hong Kong, joined Dec 2006, 8883 posts, RR: 75
Reply 7, posted (8 years 7 months 2 weeks 4 days 4 hours ago) and read 13288 times:

Quoting Ual744 (Reply 5):
I cut both engines on the same side at the worst possible time on takeoff, and it depended on the weight.

Could not do that under Vmcg.

Quoting Airfoilsguy (Reply 6):
Sometimes there are even 5 engine flights.

Thats a 4 engine flight, the 5th one is on a pod not producing power.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineManchesteruk From United Kingdom, joined Sep 2005, 140 posts, RR: 0
Reply 8, posted (8 years 7 months 2 weeks 4 days 4 hours ago) and read 13241 times:

http://www.airsafe.com/events/noengine.htm

here some info about unpowered incident, eg air transat august 2001


User currently offlineKC135TopBoom From United States of America, joined Jan 2005, 12128 posts, RR: 51
Reply 9, posted (8 years 7 months 2 weeks 3 days 15 hours ago) and read 11620 times:

Actually, a B-747, or most other 4 engine airplanes, could take off with only two engines operating, if they were symetrical engines (either both inboards, or both outboards operating), if the gross weight were low enough and a slightly aft CG (percent of MAC).

Usually the maximum thrust to weight ratio a turbo-jet or a turbo-fan can lift is 7:1. Meaning, for every 1 pound of thrust, it can lift 7 pounds of weight. This assumes the wing is aerodynamicly capable.

So, a B-747-200 equipped with, say four GE CF-6-50s, each producing 52,000lbs of thrust, but only operating on just the two inboard engines (104,000lbs of total thrust) should be able to take off (10,000'-12,000' long runway at sealevel to about 1,000' above sealevel airports field elevation) up to a MGTOW of 728,000lbs.

There are several other variations here that could effect this. So, the actual weight could be less.

The one most important fact to remember here is under these conditions, there is no safety factor. You cannot loose an engine, and both engines must be able to reach their maximum thrust. There also must be at least a 10 knot headwind down the runway. Any cross wind componet will add to the ground roll, and you might not make it. There is no tail wind capability.

The only way to add or increase a safety factor is to reduce the gross weight, but keep a slightly aft percent of MAC.

After take off and the landing gear and flaps have been retracted (as well as the reduced weight because of the fuel you already burned), there is a safety factor and thrust can be reduced.

I would never recommend doing this.

Kids, remember, we are professionals. So, do not try this at home.


User currently offlineA390 From South Africa, joined Sep 2005, 204 posts, RR: 0
Reply 10, posted (8 years 7 months 2 weeks 3 days 13 hours ago) and read 10892 times:

In the early 1990's I witnessed a SA B747 take off after two engines failed. I forget the flight number but it was a JNB-ZRH routing and fully loaded. On rotation an engine on the starboard side had a flame out, a flame shot out the engine some distance, then at appox 200ft an engine on the port side also failed. The aircraft continued to climb, very very slowly! Fuel was dumped and the B747 returned some 40 minutes later and did an emergency landing. The landing was pretty heavy but all onboard were safe. A very interesting and scary evening at work indeed!

User currently offlineWorldliner From United Kingdom, joined Aug 2005, 275 posts, RR: 0
Reply 11, posted (8 years 7 months 2 weeks 3 days 9 hours ago) and read 8813 times:

i head about a BA 744 going san francisco - LHR. shortly after take off an engine failed but they kept on flying and got to LHR with only a 30 min delay. sorry i cant seem to find the piece on it but ill keep looking.

regards

worldliner



@777Worldliner
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17003 posts, RR: 67
Reply 12, posted (8 years 7 months 2 weeks 3 days 7 hours ago) and read 7509 times:

Quoting Cruiser (Reply 2):
The way I see it, I don't care how many engines are under the wing. If there are four engines on a plane, and one dies, then it puts a greater strain on the other three, and I think that it is MORE likely to have another engine failure.

Wrong. Why should there be more stress on the other 3? They can handle a higher thrust setting.

Quoting Cruiser (Reply 2):
Especially out over the ocean..

Why would the ocean make a difference.

Quoting Cruiser (Reply 2):
However, because I think people are much more comforted by the fact that they still have three engines, they start doing stupid things. Like the BA 747's last year. If it were a twin, then it would land at the nearest possible place.

Pax in general have no idea how many engines an aircraft has. Just ask next time.

Pilots in general do not start doing "stupid things" just because an engine goes out. There are rules (authority and airline) covering the situation, and those rules are followed. The BA crew didn't break the rules. A quad is allowed to continue with three engines.


As for a 744 taking off on two engines, maybe it could, but since an engine out scenario would doom it, the rules say you can't. No pilot would be stupid enough to try.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineDrP From United Kingdom, joined Jul 2005, 280 posts, RR: 4
Reply 13, posted (8 years 7 months 2 weeks 3 days 6 hours ago) and read 6729 times:

You can fly a 747 with just two engines, but it has to be an empty ferry, you have to have dispensation and the pilots must have completed additional training in order to do so. Obviously in an emergency situation where two engines fail, this is not the case  Smile


My pony plays the mamba . .
User currently offlineGary2880 From , joined Dec 1969, posts, RR:
Reply 14, posted (8 years 7 months 2 weeks 3 days 6 hours ago) and read 6683 times:

Just for the sake of my interest, if they had the choice, which would be the best 2 to use, 2 outboard or 2 inboard?

Just wondering  wave 


User currently offlinePilot21 From Ireland, joined Oct 1999, 1384 posts, RR: 2
Reply 15, posted (8 years 7 months 2 weeks 3 days 6 hours ago) and read 6675 times:

Quoting Worldliner (Reply 11):
i head about a BA 744 going san francisco - LHR. shortly after take off an engine failed but they kept on flying and got to LHR with only a 30 min delay. sorry i cant seem to find the piece on it but ill keep looking.

This was a LAX-LHR BA flight (or maybe SFO) which was discussed a lot here last year. The engine failed just after take-off, and after discussing the issue with Ops in London the Captain decided to continue the journey, but they didn't get the expected tailwinds from the jetstream, so they had to make an emergency landing at MAN with a low-fuel situation, hence all the press discussions on it.

In 2003 a United B777 lost an engine on a Auckland-LAX flight and so became the longest true ETOPS flight on 1 engine when the crew flew for 3hrs on a single engine to reach Hawaii. While I generally don't give much thought to the aircraft I'm flying on (i.e 2 or 4 engines), in that situation I'd have preferred 3 other engines taking the strain rather then 1. Remember, while ETOP twins do have very strict maintenance rules and procedures, you can't always protect against human dumbness, which was the reason for the L1011 above loosing 2 engines after take-off, the same mechanic worked on both engines, and fitted the same oil seal wrongly on both engines. (I think it was an oil seal issue which caused the engines to seize)

Just my 2 cents worth



Aircraft I've flown: A300/A310/A320/A321/A330/A340/B727/B732/B733/B734/B735/B738/B741/B742/B744/DC10/MD80/IL62/Bae146/AR
User currently offlineCruiser From Canada, joined Apr 2005, 1001 posts, RR: 7
Reply 16, posted (8 years 7 months 2 weeks 3 days 6 hours ago) and read 6660 times:

Quoting Starlionblue (Reply 12):
Wrong. Why should there be more stress on the other 3? They can handle a higher thrust setting.

Sure they can handle a higher thrust setting, but four engines were put on the plane for a reason. Obviously, if you lose one, then the other three have to take up the slack of the other one, thus would be operating at 133% thrust (of normal flight) for extended periods of time. It is possible that the higher thrust setting for extended periods may cause additional problems. It is a rather simple thing really!

Quoting Starlionblue (Reply 12):
Why would the ocean make a difference.

Sorry, you are quite right. I didn't really finish my thought! Basically, over the ocean, there are fewer places to land should the plane run into further problems.

Quoting Starlionblue (Reply 12):
Pax in general have no idea how many engines an aircraft has. Just ask next time.

Pilots in general do not start doing "stupid things" just because an engine goes out. There are rules (authority and airline) covering the situation, and those rules are followed. The BA crew didn't break the rules. A quad is allowed to continue with three engines.

Ah phew, I am so glad that those rules are in place and are followed 100% of the time.  Yeah sureRules are continually updated. Following many crashes, there are updates to the rules and regulations so that they do not happen again. However, you surmise that the rules are perfect, and that nothing will happen because the rules are perfect and that they will prevent ANY accident from ever happening if followed properly.

Sure the plane is allowed to continue on with three engines under the rules, but is it taking un-warranted risk? Over 400 lives are at risk, just for the sake of a few hours of time.

Quoting Starlionblue (Reply 12):
As for a 744 taking off on two engines, maybe it could, but since an engine out scenario would doom it, the rules say you can't. No pilot would be stupid enough to try.

Never say never. I concur that the pilot would likely not be stupid enough to try, however, it could happen that the plane strikes an object during takeoff, and both engines on one wong become disabled. The plane needs to be able to circle around and land again. It could happen...although I will admit that the likelihood is minimal.

James
 Yeah sure



Leahy on Per Seat Costs: "Have you seen the B-2 fly-by at almost US$1bn a copy? It has only 2 seats!"
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 17, posted (8 years 7 months 2 weeks 3 days 4 hours ago) and read 6250 times:

Quoting Cruiser (Reply 16):
Sure they can handle a higher thrust setting, but four engines were put on the plane for a reason. Obviously, if you lose one, then the other three have to take up the slack of the other one, thus would be operating at 133% thrust (of normal flight) for extended periods of time. It is possible that the higher thrust setting for extended periods may cause additional problems. It is a rather simple thing really!

Completely wrong! You are assuming that all 4 engines need to run at 100%. That's not the case, thus a very wrong assumption.

As a 744 Captain, I can tell you that given a long enough runway the 744 will takeoff on 2 engines. Here's the qualifier: If it's light enough! I have done way too many 3 engine ferry flights on the 747/744, where all the takeoff performance is based on losing another engine (Hmm 3-1=2). But, that is all after VMCG. The assumption is prior to VMCG you'll have to abort, which you will.

Now, you could, if the runway was long enough, takeoff on two engines on one side only, but you'd need a runway that for all practical purposes was about 10Km long. In reality, you don't set takeoff thrust until you've passed VMCG, thus the extremely long runway. Not too practical, in my opinion.

The 744 takeoff performance is all based on 4 engines operating at the start of the takeoff roll, and then having 3 at V1. The 744 will fly at MTOW on two engines (assuming you lose them both at V1).

Quoting Cruiser (Reply 16):
Sure the plane is allowed to continue on with three engines under the rules, but is it taking un-warranted risk? Over 400 lives are at risk, just for the sake of a few hours of time

Since you're not qualified to answer that question or make any implications, I will. The crew did nothing that was against any FAR/JAR. End of story. If you don't like what the crew did, then tough. You stay in school and get your ratings and go to BA and become Chief Pilot and then you can change the SOP to prohibit the continuation of the flight.

This debate has taken place in other threads in this forum. It's surprising how many "experts" there are in the world. There were only 3 pilots (assuming augmented staffing) who were in the cockpit that night. I don't think they're members here, so none of us will ever know the decision process. But at no time did they jeopardize the safety of "over 400 lives"!!!!


User currently offlineKC135TopBoom From United States of America, joined Jan 2005, 12128 posts, RR: 51
Reply 18, posted (8 years 7 months 2 weeks 3 days 2 hours ago) and read 6125 times:

Quoting PhilSquares (Reply 17):
The 744 takeoff performance is all based on 4 engines operating at the start of the takeoff roll, and then having 3 at V1. The 744 will fly at MTOW on two engines (assuming you lose them both at V1).

Quoting Cruiser (Reply 16):
Sure the plane is allowed to continue on with three engines under the rules, but is it taking un-warranted risk? Over 400 lives are at risk, just for the sake of a few hours of time

Since you're not qualified to answer that question or make any implications, I will. The crew did nothing that was against any FAR/JAR. End of story. If you don't like what the crew did, then tough. You stay in school and get your ratings and go to BA and become Chief Pilot and then you can change the SOP to prohibit the continuation of the flight.

This debate has taken place in other threads in this forum. It's surprising how many "experts" there are in the world. There were only 3 pilots (assuming augmented staffing) who were in the cockpit that night. I don't think they're members here, so none of us will ever know the decision process. But at no time did they jeopardize the safety of "over 400 lives"!!!!

Great answer, Captain.

Quoting PhilSquares (Reply 17):
Quoting Cruiser (Reply 16):
Sure they can handle a higher thrust setting, but four engines were put on the plane for a reason. Obviously, if you lose one, then the other three have to take up the slack of the other one, thus would be operating at 133% thrust (of normal flight) for extended periods of time. It is possible that the higher thrust setting for extended periods may cause additional problems. It is a rather simple thing really!

Completely wrong! You are assuming that all 4 engines need to run at 100%. That's not the case, thus a very wrong assumption.

As a 744 Captain, I can tell you that given a long enough runway the 744 will takeoff on 2 engines. Here's the qualifier: If it's light enough!

It is amazing what some people conclude as logical thinking. Another great answer, PhilSquares. I have had you on my respected list for some time now.


User currently offlineCaptain.md-11 From United Kingdom, joined Oct 2001, 704 posts, RR: 0
Reply 19, posted (8 years 7 months 2 weeks 3 days 1 hour ago) and read 5999 times:

People have a tendency to make assumptions and jump to conclusions based on no actual direct knowledge / facts, but we are only human  Smile

I have no experience of flying jets (20 hrs in a sim tops) so I do not tend to enter into these debates through lack of knowledge. However as PhilSquares said, take-off performance works on the engine out principal. If a 744 is allowed to and can perform 3 engine ferries, then yes, 2 engine take-off performance is possible.

I wouldn't go expecting a 4000 fpm climb-out though  Wink

On the twin I flew during my commercial / IR, you would be lucky to get 50 fpm climb following a simulated engine failure (especially with a dirty airframe) LOL



Twins,twins, everywhere.... but where are the three holers?
User currently offlineDc863 From Denmark, joined Jun 1999, 1558 posts, RR: 2
Reply 20, posted (8 years 7 months 2 weeks 3 days ago) and read 5980 times:

There was a 747-200 Continental aircraft flying from LGW-EWR in summer of 1987/88 that lost 2 or 3 engines just after rotation and barely cleared Beacon Hill.

User currently offlineEilennaei From , joined Dec 1969, posts, RR:
Reply 21, posted (8 years 7 months 2 weeks 2 days 19 hours ago) and read 5755 times:

Quoting Dc863 (Reply 20):
There was a 747-200 Continental aircraft flying from LGW-EWR in summer of 1987/88 that lost 2 or 3 engines just after rotation and barely cleared Beacon Hill.

Could not find anything such on Continental nor "747" for Newark Liberty Intl between roughly those dates in the FAA accident/incident database??
One CO 747 had returned on 21st Apr 1988 after a hydraulic failure, dumping fuel.
http://www.nasdac.faa.gov/portal/pag...3,33269&_dad=portal&_schema=PORTAL


User currently offlineDc863 From Denmark, joined Jun 1999, 1558 posts, RR: 2
Reply 22, posted (8 years 7 months 2 weeks 2 days 17 hours ago) and read 5636 times:

I remember reading an article about it in Flying magazine back in 1989. It may have been going to MIA. After takeoff it suffered from two engine failures. One controller in the Gatwick tower watched it and felt it was going to crash. So much so he called for the crash equipment. Apparently it came close enough to Beacon hill that the engine wake caused the treetops to sway.

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