do we really need to retract flaps in case of an engine failure after take-off?
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do we really need to retract flaps in case of an engine failure after take-off?
hello, experts, one qiz doubt me very much recently--do we really need to retract flaps in case of an engine failure after take-off?
the standard procedure of B737 says we can retract flaps when above min retraction alt. i think that's because of performance requirement if we need to follow the departure route, but in real world, retracting flaps has few negative factors:
1\increase crew's work load,do we really need to retract then extend flaps? remember we might have time pressure if we need to turn back;
2\increase potential hazards of system failure such as flaps...what if we can't extend flaps again after retract them?
my opinion is it should depend on different situations:
1\if we need to turn back,
a.with critical terrain situation, normally we will have a specific procedure for it,follow it.
b.with nice terrain situation,keep your take-off flap setting,follow ATC instruction.
2\if we need to divert, retract flaps.
one more thing,for situation 1/a, i really suggest performance dept to design a procedure without flaps retracting action. i've ever heard there is 3 different way to design the single-engine inoperative procedure, and one of them is without flaps retracting action? i don't know it's true or not?
waiting for your opinions,thank u!
the standard procedure of B737 says we can retract flaps when above min retraction alt. i think that's because of performance requirement if we need to follow the departure route, but in real world, retracting flaps has few negative factors:
1\increase crew's work load,do we really need to retract then extend flaps? remember we might have time pressure if we need to turn back;
2\increase potential hazards of system failure such as flaps...what if we can't extend flaps again after retract them?
my opinion is it should depend on different situations:
1\if we need to turn back,
a.with critical terrain situation, normally we will have a specific procedure for it,follow it.
b.with nice terrain situation,keep your take-off flap setting,follow ATC instruction.
2\if we need to divert, retract flaps.
one more thing,for situation 1/a, i really suggest performance dept to design a procedure without flaps retracting action. i've ever heard there is 3 different way to design the single-engine inoperative procedure, and one of them is without flaps retracting action? i don't know it's true or not?
waiting for your opinions,thank u!
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In all aircraft, swept wing or straight (excluding delta-winged aircraft), the best rate of climb is achieved when flaps/leading edge devices are fully retracted and the airplane is flown at the appropriate speed.
Suggest you fully read and understand the book....'Handling The Big Jets'...authored by Capt DP Davies.
He explains it all, very nicely.
Suggest you fully read and understand the book....'Handling The Big Jets'...authored by Capt DP Davies.
He explains it all, very nicely.
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"In all aircraft, swept wing or straight (excluding delta-winged aircraft), the best rate of climb is achieved when flaps/leading edge devices are fully retracted and the airplane is flown at the appropriate speed."
---agree with that, and that's basic.
but for the case i mentioned above, we depart from a airport located in a nice broad champaign- climb gradiant is not the priority factor anymore,but the time pressure/working load is.
thank u for your recommendation, anyway.
---agree with that, and that's basic.
but for the case i mentioned above, we depart from a airport located in a nice broad champaign- climb gradiant is not the priority factor anymore,but the time pressure/working load is.
thank u for your recommendation, anyway.
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The slower a wing flies the higher the Angle of Attack (or "alpha") becomes, which increases drag and eventually results in the wing-stalling.
To allow reasonably low-speed performance a variety of high-lift devices are used which increase lift, thus reducing the alpha for a given airspeed allowing you to fly slower without excessive drag or stalling, reducing stall, landing and takeoff speeds (and reducing takeoff run).
As your airspeed increases, the alpha lowers and flaps are no longer needed to keep the wing from stalling. Flaps produce drag (which at low speeds is offset to some degree by reducing the wings overall alpha), and as airspeeds increase this becomes quite significant (also, most flaps used on commercial jets have a structural limit of around 250 knots) and it becomes practical to retract them.
Excessive drag affects climb-performance by affecting acceleration and speed: The faster you accelerate, the faster you get up to a reasonable speed; the faster you fly for a given angle of pitch, the more rapidly you climb.
To allow reasonably low-speed performance a variety of high-lift devices are used which increase lift, thus reducing the alpha for a given airspeed allowing you to fly slower without excessive drag or stalling, reducing stall, landing and takeoff speeds (and reducing takeoff run).
As your airspeed increases, the alpha lowers and flaps are no longer needed to keep the wing from stalling. Flaps produce drag (which at low speeds is offset to some degree by reducing the wings overall alpha), and as airspeeds increase this becomes quite significant (also, most flaps used on commercial jets have a structural limit of around 250 knots) and it becomes practical to retract them.
Excessive drag affects climb-performance by affecting acceleration and speed: The faster you accelerate, the faster you get up to a reasonable speed; the faster you fly for a given angle of pitch, the more rapidly you climb.
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As a non-expert, If I was on fire I in good VMC I would consider an immediate turn downwind, retain the takeoff flap and a visual circuit to land. In a dire situation I think it is necessary to consider all options for an early and relatively safe arrival.
For any other non normal involving controlability or with endurance limited only by fuel I would probably stick to the book.
For any other non normal involving controlability or with endurance limited only by fuel I would probably stick to the book.
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thank for everyone's reply!
i think the main reason for keep retracting flaps in Boeing's standard procedure is for training purpose. I still think we should consider a little different from that depanding on factors such as terrain\kind of emergency,etc.
so what about your company policy? maybe we can find sth. from that.
i think the main reason for keep retracting flaps in Boeing's standard procedure is for training purpose. I still think we should consider a little different from that depanding on factors such as terrain\kind of emergency,etc.
so what about your company policy? maybe we can find sth. from that.
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i think the main reason for keep retracting flaps in Boeing's standard procedure is for training purpose.
You think cleaning up the airplane following an engine failure is only for training? You really believe this??
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My two cents
Lets see....
OEI and Flap Retraction above TOSA....
Gets you going faster with same thrust... a FAR bigger advantage since lift depends on square of your velocity compared to coeff of lift which is a function of your AoA. So you can climb quicker which is ALWAYS good because chances of rubbing against concrete or dirt is less in that particular configuration.
Another way to look at it is that IF THIS IS really that one day you are gonna get the OEI chances are you might get the other one going off too...
Something that sounded kinda like " Gents in case you are in trouble hope for the best BUT assume and plan for the worst" said day in and day out in the flight school comes to mind...
Thus I would rather make sure I am wings clean after TOSA at Flap retraction speed instead of having extra drag in OEI situation.
If you think OEI and Flap retraction is high work load; I dare to presume both motors gone and having to retract flaps THEN will be beyond belief in terms of workload...
As for the statement:
"i think the main reason for keep retracting flaps in Boeing's standard procedure is for training purpose"
I sincerely hope you do not believe that... Stuff in those manuals and indoctrained in the Sims are things to make sure we have the highest probability of getting back in the air after an incident.
Safe flying buddy...
OEI and Flap Retraction above TOSA....
Gets you going faster with same thrust... a FAR bigger advantage since lift depends on square of your velocity compared to coeff of lift which is a function of your AoA. So you can climb quicker which is ALWAYS good because chances of rubbing against concrete or dirt is less in that particular configuration.
Another way to look at it is that IF THIS IS really that one day you are gonna get the OEI chances are you might get the other one going off too...
Something that sounded kinda like " Gents in case you are in trouble hope for the best BUT assume and plan for the worst" said day in and day out in the flight school comes to mind...
Thus I would rather make sure I am wings clean after TOSA at Flap retraction speed instead of having extra drag in OEI situation.
If you think OEI and Flap retraction is high work load; I dare to presume both motors gone and having to retract flaps THEN will be beyond belief in terms of workload...
As for the statement:
"i think the main reason for keep retracting flaps in Boeing's standard procedure is for training purpose"
I sincerely hope you do not believe that... Stuff in those manuals and indoctrained in the Sims are things to make sure we have the highest probability of getting back in the air after an incident.
Safe flying buddy...
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...After take off with engine failure it's practical reality to retract flaps, especially when heavy and fuel dumping is required, which could take up to 50 minutes [B74]. In many cities, as FRA, for example, you couldn't dump just anywhere, you'd be vectored up to the North Sea for dump. And besides all that, it's not a "distraction" to retract flaps, just as it is not a distraction to raise the gear after positive climb. . . with or without an engine failure. 
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There is only one sensible reply on this thread from someone who has read and understood the question - Sciolistes in post #5.
Let's see - we have:
worrying about retracting flaps with a double engine failure after take-off on a twin jet??
worrying about fuel dumping on a 737
worrying about flying into a hill where none exists
The answer as given, eagle, is stick to the book UNLESS there is an over-riding reason not to.
Let's see - we have:
worrying about retracting flaps with a double engine failure after take-off on a twin jet??
worrying about fuel dumping on a 737
worrying about flying into a hill where none exists
The answer as given, eagle, is stick to the book UNLESS there is an over-riding reason not to.
Hi Eagle737.
Besides the reasons mentioned above you also might want to consider the Asymmetry.
In an assymmetric thrust situation you want to have as little drag as possible because that improves controllability margin.
And that is good to have. It keeps you from loosing yaw authority.
You definitely want a plane as little draggy as possible in such a situation.
So as the previous posters stated: Stick to the books. They are there for a reason....
Besides the reasons mentioned above you also might want to consider the Asymmetry.
In an assymmetric thrust situation you want to have as little drag as possible because that improves controllability margin.
And that is good to have. It keeps you from loosing yaw authority.
You definitely want a plane as little draggy as possible in such a situation.
So as the previous posters stated: Stick to the books. They are there for a reason....
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To expand on BOAC's post...
and being non-type specific.
To not retract the flaps is different to the SOP / trained for profile / expectation of both crew members. To deviate from the SOP requires justifcation, and such justification needs to be agreed by both crew members. That agreement may be by company / type SOP (which you say is not offered?), or on the day briefing (prior takeoff). If it has not been established until after the engine failure, it is not the time to break the profile / checks and start discussing "if it is a good idea"
As a guide, in our outfit / type, it is in our books for an (exceptional)immediate VMC return option, which cleans up to 1 stage of Flap. I tend, when the weather is appropriate to "mention" it in the brief as an option. However, I can see workload meaning it difficult to get it agreed at the appropriate moment - it jumps a fair amount of the decision / diagnosis process(es).
NoD
The answer as given, eagle, is stick to the book UNLESS there is an over-riding reason not to
To not retract the flaps is different to the SOP / trained for profile / expectation of both crew members. To deviate from the SOP requires justifcation, and such justification needs to be agreed by both crew members. That agreement may be by company / type SOP (which you say is not offered?), or on the day briefing (prior takeoff). If it has not been established until after the engine failure, it is not the time to break the profile / checks and start discussing "if it is a good idea"
As a guide, in our outfit / type, it is in our books for an (exceptional)immediate VMC return option, which cleans up to 1 stage of Flap. I tend, when the weather is appropriate to "mention" it in the brief as an option. However, I can see workload meaning it difficult to get it agreed at the appropriate moment - it jumps a fair amount of the decision / diagnosis process(es).
NoD
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Remembering that if you are taking off into icing conditions with the engine failure (assuming you intend to return to land) Boeing recommend the holding pattern be conducted clean for as long as practicable. In any case, your claim of extra load on the crew during flap retraction is nothing out of the ordinary. Same with flap extension. There is more load on the crew if fiddling with FMC's at low altitude. There is so much 
about crews being overloaded even when the tasks are mundane. You have been reading too much psycho-babble.
about crews being overloaded even when the tasks are mundane. You have been reading too much psycho-babble.
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The takeoff flight profile is dictated by the takeoff flight path certification requirements of F.A.R. Part 25 (or its equivalent). The carrier can modify the regulatory takeoff flight path segments, but only with the concurrence of the aircraft O.E.M and usually also with the concurrence of the state of registration aviation authority.
The crew is most decidedly not competent to further modify that profile in the event of an engine failure on takeoff. They have no idea of the location of critical obstacles, clearance of which may only be assured by following the takeoff flight path with precision.
Further, failure to follow the flap retraction schedule with OEI, especially with a heavy aircraft at a critical airport, can result in running out of airspeed, altitude, and ideas, all at the same time.
The crew is most decidedly not competent to further modify that profile in the event of an engine failure on takeoff. They have no idea of the location of critical obstacles, clearance of which may only be assured by following the takeoff flight path with precision.
Further, failure to follow the flap retraction schedule with OEI, especially with a heavy aircraft at a critical airport, can result in running out of airspeed, altitude, and ideas, all at the same time.
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i really respect everyone's opinion and thank for them. but as BOAC said, i am also doubting that my opinion is cleared by everyone or not. Sorry about my english, i'll try to make myself clearer this time.
1. performance limit
the only situation i will consider this method is when taking off from an airport like MLE(capital airport in Maldives) -—we don't need to worry about climb gradient totally in case of an engine failure!
VMC? i really don't think it's necessary for my decision.
2. FAR regulations
Law is law, no negotiation on it, i know this. so i asked a qiz at my first post:" i've ever heard there is 3 different way to design the single-engine inoperative procedure, and one of them is without flaps retracting action? i don't know it's true or not?"
now i am still waiting for the answer.
3.company policy
my company's policy is the same as Boeing's procedure. can we doubt Boeing's procedure?best not before we have adequate proof--so we discuss and we learn.
Boeing is not the GOD, and its procedure is not the Bible,at least we may give it some good supplementary idea--and that's why we have so many company's policy.
acctually, i started this qiz just because i had a chance to give some advise to our company's SOP.
4.briefing between crewmembers
of course we need to brief and get a same expectation before we do that.
5.Asymmetry
good thinking.but let's see Boeing's procedure, you maybe only have 30 sec between retracting and extending flaps
as my company's SOP, PM should monitor how flaps' retracting and extending work and call out any abnormal situation like asymmetrical flaps---i think this rule is good----and this is what i mean "increasing work load"!
recent Qantas A380's engine failure has proved the possibility to a flap's malfunction after an engine failure---that is what i mean "increase potential hazards of system failure such as flaps"
6.icing conditions\critical airport...etc
sorry, i really didn't mean that.
1. performance limit
the only situation i will consider this method is when taking off from an airport like MLE(capital airport in Maldives) -—we don't need to worry about climb gradient totally in case of an engine failure!
VMC? i really don't think it's necessary for my decision.
2. FAR regulations
Law is law, no negotiation on it, i know this. so i asked a qiz at my first post:" i've ever heard there is 3 different way to design the single-engine inoperative procedure, and one of them is without flaps retracting action? i don't know it's true or not?"
now i am still waiting for the answer.
3.company policy
my company's policy is the same as Boeing's procedure. can we doubt Boeing's procedure?best not before we have adequate proof--so we discuss and we learn.
Boeing is not the GOD, and its procedure is not the Bible,at least we may give it some good supplementary idea--and that's why we have so many company's policy.
acctually, i started this qiz just because i had a chance to give some advise to our company's SOP.
4.briefing between crewmembers
of course we need to brief and get a same expectation before we do that.
5.Asymmetry
good thinking.but let's see Boeing's procedure, you maybe only have 30 sec between retracting and extending flaps
as my company's SOP, PM should monitor how flaps' retracting and extending work and call out any abnormal situation like asymmetrical flaps---i think this rule is good----and this is what i mean "increasing work load"!
recent Qantas A380's engine failure has proved the possibility to a flap's malfunction after an engine failure---that is what i mean "increase potential hazards of system failure such as flaps"
6.icing conditions\critical airport...etc
sorry, i really didn't mean that.
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Originally Posted by eagle737
1. performance limit (...) when taking off from an airport like MLE(capital airport in Maldives) -—we don't need to worry about climb gradient totally in case of an engine failure!
FAR regulations - (...) now i am still waiting for the answer.
FAR 25.111 Take-off path
(a) The take-off path extends from a standing start to a point in the take-off at which the aeroplane is 457 m (1500 ft) above the take-off surface, or at which the transition from the take-off to the en-route configuration is completed and VFTO is reached, whichever point is higher. In addition (...)
(c)(3) At each point along the take-off path, starting at the point at which the aeroplane reaches 122 m (400 ft) above the take-off surface, the available gradient of climb may not be less than –
(i) 1·2% for two-engined aeroplanes;
(...)
Have you checked that you can always meet the requirement of 25.111(c)(3)(i) with one engine inoperative, the remaining engine at maximum continuous thrust, and flaps in the takeoff setting?
Boeing is not the GOD
regards,
HN39
Last edited by HazelNuts39; 2nd Jan 2011 at 16:07.
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An acft with flap usually has more drag than one without. This again
means you need more thrust (assymetric) giving more acft assymetry, which again means even more drag...which again..
xpm
means you need more thrust (assymetric) giving more acft assymetry, which again means even more drag...which again..
xpm
Last edited by XPMorten; 2nd Jan 2011 at 16:33.