Double engine failure turnback
Thread Starter
Double engine failure turnback
Whilst brushing my teeth this morning I started to ponder the feasibility of a 'turnback' on a B733.
What height would be required for such a manouevre to be successful? Indeed, is it even possible assuming typical weights and weather?
WWW
What height would be required for such a manouevre to be successful? Indeed, is it even possible assuming typical weights and weather?
WWW
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For most situations couldn't you just turn and land back on the runway you've just taken off from, only in the reverse direction? The worse the tail wind the more you get blown back to the airfield in the turn which is a help. Offhand I would say the optimum glide sink rate is lower than the normal climb rate so you just need enough height to give you the turn. Otherwise you always make a profit.
Thread Starter
I was thinking more of finding the MINIMUM height required for a turnback to land on the reciprocal to the take-off runway.
WWW
WWW
Try using Microsoft flightsim, the 737 model seems quite good and it would give you a pretty good idea I suspect, your problem will be the radius of the turn required change direction, you are going to end up a long way off the centre line. Good luck, I'm going to give it a go now.
Thread Starter
I don't have a flightsim. Cheers,
WWW
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It's not simply a question of height. It is also a question of how quickly that height was obtained.
Far better to land in a farmers field with the wings level than cartwheel over the airport fence.
At a guess, I would say that 1000ft ft per nm from the end of the runway with a minimum of 2000ft and 2nm in no wind could be done.
The minimum would see the aircraft align with the centerline as it hit the runway 300m in.
Must try it.
DFC
Far better to land in a farmers field with the wings level than cartwheel over the airport fence.
At a guess, I would say that 1000ft ft per nm from the end of the runway with a minimum of 2000ft and 2nm in no wind could be done.
The minimum would see the aircraft align with the centerline as it hit the runway 300m in.
Must try it.
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Interesting question WWW. Next sim-check Ill play around and see what happens. Your assuming a 2-eng exercise holding max power at V2 flap 5? Or a normal everyday T.O.?
If its the latter:
Any particular TO flap setting? 5 or 15? We arent alowed flap 1 for T.O. and the sim wont accept it either.
3rd segment? 800 ft ok?
Weight? MTOW or MLW or a mid-range weight of say 56 tonnes?
Wind? Say a typical 10kt head?
Power? Max or reduced?
Runway length? A 4000 foot cricket-pitch or a 13,123 foot freeway? I assume a full-length T.O. run?
If its the latter:
Any particular TO flap setting? 5 or 15? We arent alowed flap 1 for T.O. and the sim wont accept it either.
3rd segment? 800 ft ok?
Weight? MTOW or MLW or a mid-range weight of say 56 tonnes?
Wind? Say a typical 10kt head?
Power? Max or reduced?
Runway length? A 4000 foot cricket-pitch or a 13,123 foot freeway? I assume a full-length T.O. run?
WWW - is there something we need to know about Go-Fly......
Don't know much about the little 73, but in man-sized aeroplanes you also lose a considerable number of hydraulic and other systems with total engine failure - it's outside the realms of consideration unless on an ETOPS twin you have a massive fuel leak and an associated single engine failure on that side and then elect to run the 'fuel imbalance' checklist and lose all your remaining fuel as a result....
Once took off from Cyprus and lost 2 engines; whilst completing the drills another failed at around 2500ft . Set full power on the last and flew a 250 kt descent until we were on the reciprocal glidepath, then dropped the gear and reduced to around 210 until sure of getting in, selected flaps and slats t/o and out and kept full power until we landed in that configuration. In the simulator, of course!
Don't know much about the little 73, but in man-sized aeroplanes you also lose a considerable number of hydraulic and other systems with total engine failure - it's outside the realms of consideration unless on an ETOPS twin you have a massive fuel leak and an associated single engine failure on that side and then elect to run the 'fuel imbalance' checklist and lose all your remaining fuel as a result....
Once took off from Cyprus and lost 2 engines; whilst completing the drills another failed at around 2500ft . Set full power on the last and flew a 250 kt descent until we were on the reciprocal glidepath, then dropped the gear and reduced to around 210 until sure of getting in, selected flaps and slats t/o and out and kept full power until we landed in that configuration. In the simulator, of course!
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WWW - why not try it in the sim, maybe from the power cutback (say) 1000' AAL and see how you get on.
BEagle - you say its outside the realms of consideration but how about the SAS MD80 (or whatever it was) that suffered a double engine failiure due to ice which had formed over the cold soaked fuel tanks and then broke off and entered the rear mounted engines. Happened about 10 years ago and they got id down reasonably OK in afield (straight ahead but the problem occured at low height straight after takeoff)
Regards
BEagle - you say its outside the realms of consideration but how about the SAS MD80 (or whatever it was) that suffered a double engine failiure due to ice which had formed over the cold soaked fuel tanks and then broke off and entered the rear mounted engines. Happened about 10 years ago and they got id down reasonably OK in afield (straight ahead but the problem occured at low height straight after takeoff)
Regards
> how about the SAS MD80 (or whatever it was) that suffered a double engine failiure due to ice which had formed over the cold soaked fuel tanks and then broke off and entered the rear mounted engines. Happened about 10 years ago and they got id down reasonably OK in afield (straight ahead but the problem occured at low height straight after takeoff)
Regards<
It wasn't ice formed over cold soaked fuel. It was the first flight of the day after snowing overnight. All aircraft would have had the same ice that day.
Regards<
It wasn't ice formed over cold soaked fuel. It was the first flight of the day after snowing overnight. All aircraft would have had the same ice that day.
Thread Starter
Lets say Full power take off 49,000kgs 10kt headwind, flap 5 T/O Boeing speeds, ISA VMC conditions.
I don't have a sim for a while. Its purely a theoretical exercise - obviously a controlled straight ahead 'landing' is much more likely to be the better option.
Back of a fag packet calcs suggest to me 2,200ft...
WWW
I don't have a sim for a while. Its purely a theoretical exercise - obviously a controlled straight ahead 'landing' is much more likely to be the better option.
Back of a fag packet calcs suggest to me 2,200ft...
WWW
Are there any aeronautical experts out there that can tell us what the ideal bank angle would be??? Something that gives the best rate of turn / rate of descent ratio I suppose.
My gut feeling says 45 degrees bank angle. Don't ask me why.
If you were doing say 210kts and you just tried to do a 180 degree turn back, the radius of turn would be about 1.4 nm. So if say you were 3 nm up wind, you'd end up about 45 degrees off the runway centre line.
So to track back the the upwind end of the runway you would have to turn 225 degrees and then try and judge a 45 degree turn right at the last moment to track down the centreline. A total heading change of 270 degrees.
If you did a 80/260 turn you'd have to turn a total of 340 degrees. You'd be on the centreline for sure but I just wonder if the extra heading change might be the difference between making it back or not. Depends on how much altitude you've got to play with of course.
Great topic.
Oops.
That radius of turn assumes 25 degrees bank angle. At 45 degrees bank angle the radius is 0.63nm. Therefore at say 3nm upwind that would put you 23 degrees off the centreline. The total change in heading would be 226 degrees (180+23+23).
I think too that it would have to be a situation where you had a sudden double engine failure after climbing away on two engines. If it was the case where you had an engine failure early on in the piece say, soon after v1 and then you had a second failure after climbing at around 2.4 to 3 percent climb gradient, you wouldn't have a hope of turning back would you? Climb angle of 3 percent plus a glide angle of at least 5 percent, means that unless you find that nice open field in front of you, there's an exellent chance you'll scratch the paint.
My gut feeling says 45 degrees bank angle. Don't ask me why.
If you were doing say 210kts and you just tried to do a 180 degree turn back, the radius of turn would be about 1.4 nm. So if say you were 3 nm up wind, you'd end up about 45 degrees off the runway centre line.
So to track back the the upwind end of the runway you would have to turn 225 degrees and then try and judge a 45 degree turn right at the last moment to track down the centreline. A total heading change of 270 degrees.
If you did a 80/260 turn you'd have to turn a total of 340 degrees. You'd be on the centreline for sure but I just wonder if the extra heading change might be the difference between making it back or not. Depends on how much altitude you've got to play with of course.
Great topic.
Oops.
That radius of turn assumes 25 degrees bank angle. At 45 degrees bank angle the radius is 0.63nm. Therefore at say 3nm upwind that would put you 23 degrees off the centreline. The total change in heading would be 226 degrees (180+23+23).I think too that it would have to be a situation where you had a sudden double engine failure after climbing away on two engines. If it was the case where you had an engine failure early on in the piece say, soon after v1 and then you had a second failure after climbing at around 2.4 to 3 percent climb gradient, you wouldn't have a hope of turning back would you? Climb angle of 3 percent plus a glide angle of at least 5 percent, means that unless you find that nice open field in front of you, there's an exellent chance you'll scratch the paint.
Last edited by Blip; 2nd May 2002 at 00:21.
Thread Starter
Double engine seperations - wow - that is a bad day. I thought maybe a flock of geese...
Good point on turn radius and optimum angle of bank.
At some airports that have a 180 degree Emergency Turn procedure I guess a landing back on would be a viable option if you encountered the mythical formation of kamikazee Geese.
Needs someone with more perf knowledge than myself...
WWW
Good point on turn radius and optimum angle of bank.
At some airports that have a 180 degree Emergency Turn procedure I guess a landing back on would be a viable option if you encountered the mythical formation of kamikazee Geese.
Needs someone with more perf knowledge than myself...
WWW
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WWW you want 49T? Thats 700 kg under 733 MZFW. How about 55T as a more realistic fugure? Sure your on 300s and not 500s mate?
PS Ill try mucking around in the sim and come out with a figure that gives you a heading rollout on final at 50ft alt at Vref flap 5 for 55T (168 kt).
PS Ill try mucking around in the sim and come out with a figure that gives you a heading rollout on final at 50ft alt at Vref flap 5 for 55T (168 kt).
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You could probably work it out from the Performance Charts. Go on, WWW, when was the last time you worked it all out from scratch?
I have the following in my collection. Admittedly it is for a light single, but many of the principles remain the same.
I have the following in my collection. Admittedly it is for a light single, but many of the principles remain the same.
THE IMPOSSIBLE TURN
In May 1992 at Tumbler Ridge, B.C., a Piper Cherokee aircraft with five passengers crashed following an attempt by the pilot to return to the runway after experiencing an engine failure. The aircraft was only 100 feet above the ground when the engine problem occurred. The aircraft stalled during the attempted turn, causing loss of control at an altitude from which recovery was impossible.
This was not an isolated incident. During a 10-year period from 1982 to 1991, there were 176 accidents resulting from engine failure after take-off in single-engine aircraft. In about half of these, the pilot tried to turn back to the departure runway instead of landing straight ahead. In most of these accidents, the pilot lost aircraft control while attempting the impossible return to the runway.
An analysis of these accidents showed that an aircraft crash caused by loss of control as a result of excessive manoeuvring is 10 times more likely to cause fatalities, and five times more likely to cause serious injuries than if the pilot had elected to land straight ahead. Lower groundspeed associated with a straight-ahead into-wind forced landing, as well as being under control prior to impact with the terrain, reduces the risk. Surprisingly, the data also revealed that experienced pilots are just as likely as novices to attempt the impossible.
Using data from the Cessna 172 Aircraft Flight Manual, our test pilots crunched some numbers to help convince you that straight ahead and under control is your only real option.
Using the following conditions, the analysis was done for an engine failure at 500 ft and 1000 ft.
Conditions and Assumptions
Altitude - Sea level
Temperature - ISA
Wind - Calm
Climb speed - 75 kts IAS
Rate of climb to 500' - 688 ft/min
Rate of climb to 1000' - 675 ft/min
Glide speed after engine failure - 65 kts IAS
Glide performance - 1.5 nm/1000'
Bank angle in turn back - 30 degrees
The analysis assumes a straight climb-out followed by a 270 degree turn, a reversed 90 degree turn and a straight return to the runway. It also assumed that the climb starts at the end of the runway at 50 ft and at the specified climb speed. Flap extension for landing was not considered.
Results
Failure at 500'
Failure at 1000'
Time to climb
39 secs
84 secs
Distance covered
4,937 ft
10,634 ft
Radius of turn
648 ft
648 ft
Return distance covered during turns
1,296 ft
1,296 ft
Distance remaining to runway
3,641 ft
9,338 ft
Total distance from failure back to runway
7,711 ft
13,408 ft
Glide capability after engine failure
4,560 ft
9,120 ft
The analysis shows that from 500 ft a turn back would result in landing 3150 ft short of the runway, and from 1000 ft the landing would be 4300 ft short.
You can argue that a tighter turn reduces the distance back, but it also increases the load factor and therefore degrades glide performance, gaining you no advantage.
If a 10-knot headwind is considered and the numbers recrunched, the results show that the landing would still be 1840 ft short of the runway and 1460 ft short for the 1000 ft case.
The calculations indicate that given sufficient wind a return to the field may be theoretically possible, but the hazards of a downwind landing in such strong wind would not make this advisable, specially if one considers the very low groundspeed expected during a forced landing directly into a strong wind.
In summary, for a single-engine aircraft, given reasonable wind conditions, it is not possible to return to the take-off runway following an engine failure. Straight ahead and into wind is the only option.
In May 1992 at Tumbler Ridge, B.C., a Piper Cherokee aircraft with five passengers crashed following an attempt by the pilot to return to the runway after experiencing an engine failure. The aircraft was only 100 feet above the ground when the engine problem occurred. The aircraft stalled during the attempted turn, causing loss of control at an altitude from which recovery was impossible.
This was not an isolated incident. During a 10-year period from 1982 to 1991, there were 176 accidents resulting from engine failure after take-off in single-engine aircraft. In about half of these, the pilot tried to turn back to the departure runway instead of landing straight ahead. In most of these accidents, the pilot lost aircraft control while attempting the impossible return to the runway.
An analysis of these accidents showed that an aircraft crash caused by loss of control as a result of excessive manoeuvring is 10 times more likely to cause fatalities, and five times more likely to cause serious injuries than if the pilot had elected to land straight ahead. Lower groundspeed associated with a straight-ahead into-wind forced landing, as well as being under control prior to impact with the terrain, reduces the risk. Surprisingly, the data also revealed that experienced pilots are just as likely as novices to attempt the impossible.
Using data from the Cessna 172 Aircraft Flight Manual, our test pilots crunched some numbers to help convince you that straight ahead and under control is your only real option.
Using the following conditions, the analysis was done for an engine failure at 500 ft and 1000 ft.
Conditions and Assumptions
Altitude - Sea level
Temperature - ISA
Wind - Calm
Climb speed - 75 kts IAS
Rate of climb to 500' - 688 ft/min
Rate of climb to 1000' - 675 ft/min
Glide speed after engine failure - 65 kts IAS
Glide performance - 1.5 nm/1000'
Bank angle in turn back - 30 degrees
The analysis assumes a straight climb-out followed by a 270 degree turn, a reversed 90 degree turn and a straight return to the runway. It also assumed that the climb starts at the end of the runway at 50 ft and at the specified climb speed. Flap extension for landing was not considered.
Results
Failure at 500'
Failure at 1000'
Time to climb
39 secs
84 secs
Distance covered
4,937 ft
10,634 ft
Radius of turn
648 ft
648 ft
Return distance covered during turns
1,296 ft
1,296 ft
Distance remaining to runway
3,641 ft
9,338 ft
Total distance from failure back to runway
7,711 ft
13,408 ft
Glide capability after engine failure
4,560 ft
9,120 ft
The analysis shows that from 500 ft a turn back would result in landing 3150 ft short of the runway, and from 1000 ft the landing would be 4300 ft short.
You can argue that a tighter turn reduces the distance back, but it also increases the load factor and therefore degrades glide performance, gaining you no advantage.
If a 10-knot headwind is considered and the numbers recrunched, the results show that the landing would still be 1840 ft short of the runway and 1460 ft short for the 1000 ft case.
The calculations indicate that given sufficient wind a return to the field may be theoretically possible, but the hazards of a downwind landing in such strong wind would not make this advisable, specially if one considers the very low groundspeed expected during a forced landing directly into a strong wind.
In summary, for a single-engine aircraft, given reasonable wind conditions, it is not possible to return to the take-off runway following an engine failure. Straight ahead and into wind is the only option.
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Pretty dependent on lots of things. Are we assuming both engines conk out simultaneously?
I was given a leaflet suggesting procedure for double engine failure on a B737 a while ago. It gave a circling visual approach, similar to the old "high key" / "low key" thing, and a glide approach clean one dot above an ILS glideslope.
The danger with turnbacks - as it is with light aircraft - is that you run the risk of stalling and spinning, or not getting where you want to. I suppose if the alternative is a mountain in front of you, you might give it ago. I'd like about 4000' below me to turn the aircraft through 180' - but that wouldn't get me back to the runway.
You ought to be able to work out what gradient you would need to climb out at to allow you to have enough height to turn around and land back on the reciprocal. My suspicion is that it would be something considerably more than you are likely to have until about 7 or 8 thousand feet.
I was given a leaflet suggesting procedure for double engine failure on a B737 a while ago. It gave a circling visual approach, similar to the old "high key" / "low key" thing, and a glide approach clean one dot above an ILS glideslope.
The danger with turnbacks - as it is with light aircraft - is that you run the risk of stalling and spinning, or not getting where you want to. I suppose if the alternative is a mountain in front of you, you might give it ago. I'd like about 4000' below me to turn the aircraft through 180' - but that wouldn't get me back to the runway.
You ought to be able to work out what gradient you would need to climb out at to allow you to have enough height to turn around and land back on the reciprocal. My suspicion is that it would be something considerably more than you are likely to have until about 7 or 8 thousand feet.
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With regard to the light single I would recommend reading:
The Possible 'Impossible" Turn By David F Rogers, AIAA Journal of Aircraft, 1995. Vol 32: pp 392-397.
Basically 45º bank turn at 1.05 V stall(clean).
There is a lot of math in the article but you might be able to use it to give data for heavy metal.
Rgds
CB
The Possible 'Impossible" Turn By David F Rogers, AIAA Journal of Aircraft, 1995. Vol 32: pp 392-397.
Basically 45º bank turn at 1.05 V stall(clean).
There is a lot of math in the article but you might be able to use it to give data for heavy metal.
Rgds
CB