B737 Maximum Flaps Extended Altitude
 

Hi guys,

in the Limitation section of the AFM (and FCOM) of the B737 Classic, the limitation states the following:

- Do not extend flaps above 20,000 feet pressure altitude.

Now, let's say you take off and have a Flaps asymmetry during retraction, the airplane is well under control and you decide to continue flight to your (short leg) destination for different reasons (company base, maintenance ecc.).

Can you climb above 20,000 feet with Flaps extended?

It seems, reading the aforementioned limitation, that you are only limited by the Flaps extension (thus, the "operation" of the flaps and not the flaps already extended).
The Non Normal Checklist covers this trouble (asymmetry) during approach only. I checked the 737 MRG book too, but it says nothing more than to avoid using FMC fuel prediction in case of continuation toward the destination.

I just want to know if you are legally authorized to do it and not if you would or wouldn't do that because of Mach effect etc. :ok:

Thank you

My bet is on no since aircraft wasn't flight tested with flaps extended above 20.000ft and is therefore not certified for such operation - nor is it likely that it will ever be, given that no airport in the world requires use of flaps above FL200.

BTW, if it's a short leg and assuming you have appropriate amount of fuel to fly to preferred airport, why even bother with flying outside of certification scope?

What a ridiculous question
 

No Pilot would exceed the 20.000 ft limitation knowingly.

If you had a flap problem on departure then your main concern would be:

a) the landing flap configuration
and:
b) the most suitable airfield to land

Worrying ...
Why would anyone even think about flying at high altitude with flaps assymetry?
I suggest you read about high altitude flying,particularly on maneuvring issues.

First of all, I'd like to express my disappointment to Exeng, there are no ridiculous questions anywhere in any subject, only stupid answers (like yours).

Why did I ask that? Because you, as a pilot, have access to different manuals. If none of these manuals report the certification of flight with flaps EXTENDED but only "flaps extension altitude" (this is my concern, the way it is written) how could you know that flying already with flaps extended above 20000 feet is out of limits?

I would never fly above that altitude with flaps extended, but as I was discussing with an instructor who would do that, I'd like to find something to be proved legally.

In simple terms, how could you prove you are out of limitations if you are not EXTENDING the flaps above 20000 feet, but you are actually climb above that altitude already in that configuration?

I hope this clarify my question...otherwise, I think you don't like to listen.

Question: 'Having watched the movie 'Flight', would it be possible to replicate that inverted approach in a B737 and roll out to a safe landing. There's nothing in the manual on the subject?'

Sensible answer: ?

I thought it is logical to understand that it is not the extension process (e.g. flaps going for example from 0 to 5) that is the issue above 20.000ft, it's the flaps extended, since aircraft hasn't been tested with flaps extended at higher Mach numbers. Therefore, Boeing has only provided maximum flap speeds only in KIAS - do you think it's really safe to fly at FL370 at M.75 with 240 KIAS and flaps 5 (limitation for F5 in -400 is 250 KIAS)?

AFM limitation:

FCOM:

Sometimes a bit of logic helps, but as it appears not with everyone...

That's what I think too, as said, I'd never fly above 20000 feet flaps extended; it was just a discussion with a colleague that prompted me to find something printed clearly.

Once again proof there are stupid questions.

I'd say that you are legally authorized to break the rules in the event of an emergency. In other words, you can't get back into your departure airport and will run out of fuel if you don't get up to a higher altitude, then you have a justifiable reason to be acting as the equivalent in this case of a test pilot.

More of a remote area ops scenario.

BtS - we are probably into semantics here, but you are correct - the driver's handbook does not prohibit flight above 20k with flaps extended.

I suggest the intention of the restriction is self-explanatory? However, I do not expect anything dramatic is going to happen at 20001' in your scenario that would not happen a 19999', so I say "if you have to...................you have to". You would certainly get reasonable notice that things are not going too well, I think, as you climbed.

I can, like you, think of very few scenarios where you might want to do it.

The scenario, regarding the discussion with the colleague, was:

- Take Off from an airport with no assistance by maintenance, 50 min flight time to destination that is our home base (the only one along the route and with full maintenance assistance etc.) which offers 3 long runways. Weather is excellent everywhere and no mountains are there to make you concern about them.

- Fuel is 100-200 Kg more than minimum; anyway, not enough to reach the destination if flying with flaps extended at low flight levels.

- Plenty of suitable airports along the route.

That's right but in this case we have to first clarify if "breaking" the 20000 feet limit is legal or not!

Land at one of the suitable airports and have the company deal with it. A maximum altitude is like a minimum weather requirement. It is a limitation. And you do not have an emergency.....although, I suppose you could declare one.

You may want to share the http://www.pprune.org/tech-log/51113...ransports.html thread with your instructor. And I would confirm the wording is the Boeing approved version regarding flap extension above 20k.

How did he come up with the fact you can make it above 20, 000' as you stated the FMC doesn't account for flap extended like it doesn't account for gear extended, FCOM 2 would have no perf figures for flap above 20, 000'. You can't assume Fuel flow and ground speed would be better.

What will happen when suddenly you hit the sweet spot and flutter rips your asymmetric flap off or your outboard aileron etc.

Is your colleague a test pilot?

Quite simple, if the flap limit is 20,000 ft, don't exceed it. My Jetstar gear wouldn't retract going from LAS to LAX one day so we stayed at FL200 and maintained max gear extention speed. It took 20 minutes longer but our passengers didn't have to wait for an extensive maintenance delay.

Flight, the movie, might have been tried by Alaska Airlines because they were going to die anyway but we all know flying inverted is not going to save any lives because even if the wings don't fail at some point when you roll upright you will dive into the ground with the HS jackscrew problem they had.

The list of posters here who are completely failing to answer the question is staggering. Let me do 'a Clandestino'?

- in terms of the wording, there is no '20000ft limitation'. - tell us what these are.- your test results showing this?- waste of server space!- your link has no reference to flaps. As far as I know there is no 'instructor' involved in this query. We know the wording. The meaning was what the question was about! - no-one is saying you can, but the question was 'is it ok to try'? I take it you would have no 'flutter' worries at 19,999'? 737 does not have an 'outboard aileron'. - which flap limit is that?

BtS - I think you will have to give up here since no-one actually knows the answer. You could try Boeing, but since there have been no (official) tests above 20k involving flaps as far as I know they would probably say no. Your choice would be try it, succeed and get a 'chocolate nose' award from company, or possibly write off the a/c.

Mach number and its effect on flaps will be your problem. Personally, unless things were desperate, I would, like JammedStab, try to persuade company to let me spend a few days at a 'choice' diversion with decent facilities.:)

I agree with you, BOAC, regarding some of the answers here, with sage-like advice and rude criticism from people who haven't bothered to read the question. I think it would have been better if BTS had excluded the scenario from his question and simply asked about extending the flaps above 20000', as opposed to leaving them already extended above 20000'.

Clearly there are issues to extending various various bits of metal into the airflow, versus leaving them there and that's why, for instance, there are differing speed limits for gear lowering and gear extended etc (this is only an example and I do understand the reasons behind this particular case). However, I think FlyingStone best answered the question with his quote from the FCOM:

Although it only refers to actually extending the flaps (as opposed to leaving them already extended) the FCOM is quite clear that Mach number is the problem and is, therefore, suggesting the 'excessive structural loads' will be present when the flaps are extending, as well as when they're extended, so the limitation applies to both scenarios. I say 'suggesting' because it doesn't clearly state that.

Doubtless there are those who will sarcastically say 'duh, it's obvious' but they are the same people who didn't read the question properly in the first place and consider 'extending' and 'extended' to mean the same thing.

Why the hell would you want to try?

Of course there are no issues at 19999' nor probably at 21000' but the limit it there simple.

I know the 737 doesn't have an outboard aileron that's why I added the etc does it matter which A/C or are you saying it's Ok because it doesn't have one? The 747 has the same 20000' limitation the point being you don't "try" flying outside the certified envelope, our job is to get people safely from A to B not try things because we think there is a loophole in the manuals.

It's probably safe till FL250 however Boeing probably said make it FL200 for the idiots that want to "try".

Nothing against the question I just find it amazing that people are possibly being trained that it is ok to bend the rules if you think it's not black and white and then do a check on a guy based on the grey?

I think was part of the point being made, SMOC, the limit is not specific enough to be a limit. The limitation says do not extend flaps, it doesn't say don't fly with flaps extended above 20000'. If that's what they mean (and I'm certain in my own mind they do) then Boeing should write it.

I agree with you that we should not be trying to this, nor should we attempt to be Boeing test pilots, however, in my opinion, the poor English used in the AOM opens Boeing to challenge if someone were to go above 20000' feet with flaps extended and it all went wrong. Semantics, yes, but that's what lawyers love when big industry cocks up.

Pontius, likewise, I guess the world is becoming a place where everything has to be written and common sence has no place, it'll never stop, the next question will be it doesn't say I can't do barrel rolls so can I try? I know extreme the mind boggles when pilots can't think of the "intent" Asia is full of its "not written" shame the Western world is going down the same path.

I'm very impressed by the very low number of users who really understood my question.

How can someone expect a professional and serious answer if so many don't even spend 2 seconds reading and understanding the question.

English is not my native language, maybe I was not so clear in the initial message but I believe I'm not the only one in fault here.

That's obvious that braking a rule (better...braking a limitation) outside an emergency situation is not professional and not even safe.

As those ones, really few, who correctly understood my question said, we are not braking any AFM-FCOM etc Limitation...looking the papers.

I was just trying to find (that's why I asked your help) a document where something clearer was stated because I might have missed it!

Captain 'Hoot' Gibson of TWA 727 fame, is the man to ask about flaps at high altitude. I think it's called, 'the other way to get down'.

Yes

Yes


The limitation is for A/C configuring for high altitude airfields not for use in an abnormal situation.


George :ok: exactly.

This is an anonymous forum. I hope there are a lot of MS Flight Sim pilots here.

By George:

He certaintly is. He would refer you to Boeing and today probably cite the 787 as an example of Boeing's methods.

As a fellow TWA pilot may I add, as I have before, neither the FAA nor the company faulted that crew. The NTSB did because they were in Boeing's pocket at the time.

Now, many years later, the FAA is in Boeing's pocket instead of the NTSB.

breakthesilence:

I read your entire first post the first time.

No one in their right mind, who is actually a real airline pilot, would come even remotely close to doing what you proposed.

Now, go back to your MSFS and have fun.

- to introduce this 'history' into this thread demonstrates a complete lack of understanding of aircraft performance and the topic.

Why not tell us EXACTLY what happened and then everyone will see the irrelevance of the posts. Did he climb above 20k with flaps extended? Did he extend flaps above 20k contrary to the limitation?

Aterpster, please, quote any post where I "proposed" to fly above 20000 feet with flaps extended.

I always respect my colleagues, virtual or real, but at this point I really think I'm not talking with people but actually monkeys; it's unbelievable how you are able to put down expression or ideas one has never expressed!

Before sending me to play Flight Sim, I can send you to play toys in diaper, than you could start learning how to read and maybe in few years you'll be able to write down your name.

I will not fall in the game "I'm a real pilot, I have XXXX Flight Time etc."; I don't have to disclose my CV to anyone to face your invitation to MSFS.

Here is a self quote from post number 5:

Chaps,

Time to retire to the various corners of the ring and count to ten. Saves me the trouble of wielding the big stick ... far prefer rational thought to return to the fray.

The guiding light remains "play the ball, not the player"

j.t.:

The "ball" in this game was the launch question:

Can you climb above 20,000 feet with Flaps extended?

Even as a hypothetical it was beyond the pale.

It was akin to me asking you, "If I lose an engine below Vmcg can I attempt a takeoff anyway?"

Come on...be serious, it's not the same kind of question, above all if you read that I was looking for sections of manuals or something written to support the misleading statement of Boeing's Limitation section of the AFM.

It was curiosity, search for something I was, probably, not able to find.

The concept is clear: it's not a great idea to fly above 20000 feet with flaps extended.

The curiosity: Had Boeing set such a limitation in any manual as I don't know if I'm missing it?

It's really, reaaaaally different from stating that I don't know or, worse, I'm willing to fly that way.

Given the exact phrasing of the original limitation, I think the question was a reasonable one and did not deserve the offhand comments it has received.

There are plenty of aircraft systems which can have multiple limits on some types, like landing gear: one maximum for deployment, one for when it's down and yet another for retraction. Also can be IAS, mach or both.

On the 777, the computers won't let you deploy flap >20K which can be problematic if you have a certain type of static failure and the aeroplane still thinks it's at 30,000' even though you're nearly on the ground.

I'd guess there are sound aerodynamic/structural reasons why it isn't a good idea to fly around at high altitude with flaps/slats out, so Boeing have thought what might be needed for operational reasons (going in/out of Bogata, for instance), added a margin then rounded it up to 20,000'. The text doesn't say what exact configuration, so there would logically be less of a problem with F1 than F30.

It's one of those scenarios that rewards a little previous thought. Like BOAC, I don't regard 20K as a hard "wings stay on/wings come off" limit but would be reticent to exceed this unless it was to avoid something worse, like hitting a mountain or running out of fuel.

The answer to: "Can you climb above 20,000 feet with Flaps extended?" would be yes, of course, but only if you *really* need to. It takes quite a bit of imagination to get to that point but hey, you never know.

Also, "If I lose an engine below Vmcg can I attempt a takeoff anyway?", could be answered by yes as well. Not all attempts will be successful, depending on the exact circumstances! It's not something that's recommended either. ;) (Next time in the sim in a twin, try a single-engined takeoff from stationary - surprising what a non-event it can be...)

This thread is a good example of why I don't really contribute here anymore. Lot's of people with 1000s of post, claiming to be real pilots, who can't even read.

I found your initial question interesting, I don't know the answer either. I feel for you Breakthesilence, load of rubbish replies and insults. I salute you and am impressed that you managed not to sink into their levels. I probably would have, which is why I stay away, because every thread here tends to degenerate :(


As for the scenario, the question is "why do it?":

A 50 min flight is normally not planned much higher than FL300, so how much do you actually expect to gain comparing to flying at FL200? If in your scenario the home base has 3 runways and it's CAVOK, why not simply dip into the alternate fuel and complete the flight in FL200.

The very first reply has the answer as far as I am concerned (737 TRE) . The 20000 restriction is in place because the aircraft has not been flight tested/certified with flap above 20000. Will it fall out of the sky? Probably not, but it is unknown territory, hence the manufacturer's requirement

I once flew as an FO with a CAA inspector in the left hand seat, where this exact question came up. The CAA inspector insisted that the limitation was specific about extending the flap, not operating with flap extended - and we proceeded to FL380 or so with a small amount of flap extended.

(There's more to that story, but that's the guts of it.)

So - yes, it's an old question. Yes, it can be misinterpreted, and yes where it can be misinterpreted there will be a pilot who will do it.

The limitation is standard on every jet aircraft I have flown, and like everyone else, I am convinced that it simply means "Flaps aren't tested in this region - here be dragons".

You flew to FL380 with some Flap extended????????

I'd suggest that with your IAS below VFE your TAS would be way toooooooo fast for the poor old Flaps to not be damaged!!!!

Yikes.....

I said it was a small amount of flap. ;)

... and since when are flap limitations based on TAS? Indeed, what would TAS have to do with flap loads at all? :confused:

I think nitpicker is confusing TAS with performance. If you're at a high TAS low level you're at a high IAS too and almost certainly outside flap operating limits. If you are at a high TAS because of altitude then you're about to change a high speed wing into a lower speed wing. And that's if you're even able to get flaps out (the limitation part of a LOIN check) at high level given your inevitable high IAS ( 240-260 kts on the A320 at FL360+). And yes I know the PFD is actually displaying CAS/EAS.