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XXXX10
Topic Author
Posts: 707
Joined: Mon Jan 03, 2000 7:10 am

Flaps At Altitiude

Mon Aug 06, 2001 2:38 am

Has anyone ever heard of an airliner using flaps/salts at altitiude or increasing the setting during the climb- perhaps allowing a lower speed or a steeper climb

Are flaps/slats inhibited above a certain altitude?

Many thanks

XXXX10
 
tt737fo
Posts: 468
Joined: Thu Jun 07, 2001 2:13 am

RE: Flaps At Altitiude

Mon Aug 06, 2001 3:01 am

Airspeed generally dictates the flap setting. Below 10,000 the idea is to climb as rapidly as possible under 250kts. Flap setting is usually in the neighborhood of 10degrees (fairly minimal as it is).

Keeping the aircraft clean allows for greater fuel efficiency. Best rate of climb will, in most cases, call for a clean aircraft.

Just as a side note (and kind of an inverse to your question), in 707 flights over the Andes, it was a common practice to deploy the landing gear (and spoilers), at alititude to speed the rate of descent into Santiago.
 
Guest

RE: Flaps At Altitiude

Mon Aug 06, 2001 4:57 am

On approach to landing, in the C172, we lower flaps to induce drag and slow us down. Flaps also allow us to fly slower and lower.
 
XFSUgimpLB41X
Posts: 3961
Joined: Fri Aug 25, 2000 1:18 am

RE: Flaps At Altitiude

Mon Aug 06, 2001 5:36 am

Flaps are only inhibited by your airspeed, not your altitude.
Chicks dig winglets.
 
FBU 4EVER!
Posts: 980
Joined: Sat Jan 27, 2001 6:53 am

RE: Flaps At Altitiude

Mon Aug 06, 2001 6:13 am

On the MD-80' and -90's I fly,the max speed for operation of slats and 11 degrees of flap is 280 KIAS/Mach 0.57.The change from KIAS to Mach takes place somewhere in the region of 20-23,ooo feet,and at high weights,the clean speed (lowest speed in clean configuration that can be used for maneouvring) will be higher than M 0.57,thus we're not usually able to extend flaps/slats above these altitudes.
"Luck and superstition wins all the time"!
 
Notar520AC
Posts: 1517
Joined: Sat Jul 21, 2001 6:53 am

RE: Flaps At Altitiude

Mon Aug 06, 2001 6:18 am

I've heard that the 747 uses them up until they reach cruise?

-Notar520AC
BMW - The Ultimate Driving Machine
 
XFSUgimpLB41X
Posts: 3961
Joined: Fri Aug 25, 2000 1:18 am

Notar520AC

Mon Aug 06, 2001 8:02 am

Nope... on the contrary they clean up as quickly as possible to save fuel (see the exceeding 250 kts below 10,000 feet thread).
Chicks dig winglets.
 
EssentialPowr
Posts: 1732
Joined: Wed Sep 06, 2000 10:30 pm

RE: Flaps At Altitiude

Mon Aug 06, 2001 8:16 am

"Flaps are only inhibited by airspeed, not altitude" is an incorrect statement as it relates to airliners.

The max altitude for flaps on a 727 is 20,000 feet. I would assume there is a similar restricition for most transport category jet a/c, as high/low speed stall characteristics of a wing at high altitude would be radically different "clean" as opposed to "dirty" (particularly for a swept wing design).
 
rendezvous
Posts: 542
Joined: Sun May 20, 2001 9:14 pm

RE: Flaps At Altitiude

Mon Aug 06, 2001 11:38 am

On the occassion that Qantas does a scenic flight to Antartica, they are not permitted to have the flaps extended due to icing problems.
 
JETPILOT
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: Flaps At Altitiude

Mon Aug 06, 2001 11:51 am

As per company profile...most airlines begin clean up at FE + 1000 or 1500 ft.

Once you reach clean up altitude you retract flaps according to the retraction schedual based on the minimum flap manouvering speeds.

After rotation you hold V2 + 10 until FE + (see above). at that point you nose the plane over and retract the flaps as soon as you pass the minimum manouering speed for the flap setting you retracting to.

When the plane is clean you climb at 250 until 10,000, or request a higher speed if your minimum manouvering speed may be higher due to AC weight.

At 10,000 you climb at 280-300 KIAS.

Flap retraction is usually comlete by 3000 FT AGL.

I'd like TT737FO to show me oytherwise per his companies 10 degree flap climb. I dont belive it.

The profile above is based on my experiences in a 727.

As Essential power said max flap extension altitude in the 727 is 20,000 feet. Thats a Boeing limitation.

JET
 
Guest

RE: Jetpilot

Mon Aug 06, 2001 12:02 pm

Are you saying that TT737FO is not as he says, a Boeing 737 First Officer?
 
fr8tdog
Posts: 120
Joined: Wed Feb 16, 2000 4:25 pm

RE: Flaps At Altitiude

Mon Aug 06, 2001 1:32 pm

The SF340 has a flap restriction of 14,000' even though its certified to FL250 unless the O2 mod is installed for O2 for all pax then up to FL310 for Far 121.
Corp's that operate under part 91 can climb to FL310 with the 10% rule on O2.
 
musang
Posts: 818
Joined: Sun Apr 08, 2001 4:11 am

RE: Flaps At Altitiude

Tue Aug 07, 2001 12:37 am

The Avro RJ 100 I drive has a flap limit of 14,ooo feet.

Never heard of any procedure involving inreasing the flap setting during the climb except on bombers during WW2. On reaching the level where further climb proved impossible, the story goes that the flaps would be lowered to the first setting, providing a sudden increase of lift and allowing further climb. However what happened when the flaps were again retracted, I don't know. Unless the speed had been regained, surely it would just sink again??

Generally speaking, a lower flap setting on t/o gives a longer t/o run but better climb rate, better for noise abatement, fuel consumption and general efficiency.

A higher setting would get the aircraft off the runway sooner, but with less climb performanc in terms of feet per minute.

The gradient may however be better in the initial stages, despite the lower forward speed, but the advantage is lost as climb rate and angle are sacrificed during acceleration through the flap retraction schedule.

At Jersey we take off flap 30 due short runway, there are no obstructions in the climb. Normal flap for t/o would be 18, used at most other destinations. At Chambery, surrounded by mountains, the southerly t/o uses flap 24 for the first 2900 feet approx of the departure before retraction/acceleration begins following an 80/260 degree course reversal in the valley.

Regards - Musang
 
cv640
Posts: 843
Joined: Wed Aug 30, 2000 8:10 pm

RE: Flaps At Altitiude

Tue Aug 07, 2001 2:55 am

Not exactly a large airliner but I know the Saab 340s limits to the flaps are 14,000 feet.
 
cv640
Posts: 843
Joined: Wed Aug 30, 2000 8:10 pm

RE: Flaps At Altitiude

Tue Aug 07, 2001 2:56 am

Also should add I've heard the 757/767 is limited to 20,000 feet with flaps extended.
 
cedarjet
Posts: 8946
Joined: Mon May 24, 1999 1:12 am

RE: Flaps At Altitiude

Wed Aug 08, 2001 2:09 am

BTW 727 crews used to extend the leading edge slats in cruise to get better performance out of the aircraft. The procedure was illegal and involved pulling circuit breakers. The practise ended when a TWA 727-100 had an upset at 41,000 ft and fell out of control to 9,000 ft in something like 90 seconds. The aircraft was badly damaged but landed safely at Detroit. The upset was caused by a slat extension, but whether it was deliberate or not isn't known because the flight crew erased the CVR tape, which is possible once the parking brake is set. Nice work on the part of the pilot to save the aircraft which at one point was spinning vertically at Mach 1.

JETPILOT must know more about it.
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
 
fr8tdog
Posts: 120
Joined: Wed Feb 16, 2000 4:25 pm

RE: Flaps At Altitiude

Thu Aug 09, 2001 12:54 am

Extending the Led's on 27's was an old wives-tale.
After the TWA incident, the pilots where cast as hero's.
As the investigation progressed, there was a rumor that the pilots had extended the Led's and caused that problem, they where then crucified.
There where extensive simulater tests completed to try to duplicate the incident, and found that extending the LED's actually resulted in worse performance due to additional drag.

The slat extention was determined to be a component failure, that Boeing said could never happen.
(sounds familiar doesnt it!)

I believe that the pilots where later exhonerated but not without damage to the credibility and lives of the pilots it had affected.

Fr8t.
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Flaps At Altitiude

Thu Aug 09, 2001 1:54 am

I remember reading the incident report for that TWA 727. I certainly don't think the pilots were "heros" for operating the aircraft contrary to the AFM.

I've witnessed this sort of damage on a Beech 200. The pilots liked to "crack a little flap" at high altitude (35K) to gain a little stability. You need to pull the circuit breaker in mid travel to acheive this. Unfortunately they would forget about the flaps in the high KIAS descent and cause damage to the flap extension/retraction mechanism.

This practice later caused one screw jack to fail and the aircraft was almost lost on an approach when one of the flaps broke free and retracted under the air load. It tool full oposite aileron to recover and land.

There is no hard and fast rule to using flaps at particular altitudes or airspeeds that apply across the board to all models. Refer to the AFM.

In the case of the SAAB 340, there were some early incidents when the flaps were extended beyond 20 degrees on the "A" models. The airflow interfered with the "positive lift" tail and caused the aircraft to pitch down violently. This was fixed in the "B" model by redesigning the horizontal stabilizer to produce negative lift (inverted airfoil) like many other aircraft have.

 
Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: Flaps At Altitiude

Fri Aug 10, 2001 9:25 am

Gotta love that home-grown theory of flight.

I think the 20,000' restriction for operation of the flaps on the Boeing may be for cavitation reasons. Perhaps one of our AME colleagues can correct/confirm this "theory".

Best Regards,

Buff
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Flaps At Altitiude

Fri Aug 10, 2001 12:22 pm

Buff,

When you said:

"Gotta love that home-grown theory of flight."

Were you referring to my post? Just curious.

 
Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: Airplay

Fri Aug 10, 2001 2:21 pm

Hi There - The following is in reference to pilots:

Many of us older folks have witnessed some pretty funny thinking by some of our colleagues in this business over time. I had a flight instructor tell me years ago how flying in just a little bit of freezing rain was a good thing because it made the wing more laminar, and increased its curvature thereby providing more lift. When you think about it, it's not so much funny as horrifying that this kind of thinking actually takes place. It was to the practice of which you wrote that I was referring - that of some pilots who come up with weird ideas, put them into practice, then get burned when it turns out their idea wasn't very smart or just plain stupid. Worse still if they manage to convince their colleagues of the merits of their idea. Much like the practice described about cracking the slats. That's what I was referring to as "home-grown theory of flight".

It's sad but it happens. It reflects badly on the rest of us when instances like this are uncovered. It is one of the really negative aspects of this business, where so many of us learn from so many different sources, that uniformity of WHAT we learn is so difficult to control.

Sorry if my sense of irony reflected on you - that was certainly not the intent. I couldn't agree more with what you wrote! Maybe someone reading this will take a second look at something they've been doing without any proven justification for doing so. Or maybe they won't and we'll have more stories for next year's forums...

Best Regards,

Buff

Keep the blue side up!
 
zionstrat
Posts: 225
Joined: Sat Apr 28, 2001 3:26 am

RE: Flaps At Altitiude

Tue Aug 14, 2001 12:39 am

Regarding the TWA 727 incident, take a look at the book 'Emergency in the cockpit' and you will be convinced that this was a mechanical failure as opposed to the crew breaking the rules.
 
calpilot
Posts: 881
Joined: Sun Oct 17, 1999 5:16 am

RE: To Everyone

Tue Aug 14, 2001 5:56 am

I would like to say that "Buff" has a very good point. So many times people in this forum add their .02cents, when sometimes they don't know what their talking about. And belive me after reading many very good questions in here, I know I sure don't know eveything. for instance "XFSUgimpLB41X" make a statment above that flaps are not limited by altitude. Well he's wrong, and now 212 people might have it wrong, thats negative learning. I'd like to challenge everyone to be a little more careful with their facts before sending them to the world on the net.
 
fr8tdog
Posts: 120
Joined: Wed Feb 16, 2000 4:25 pm

RE: Flaps At Altitiude

Wed Aug 29, 2001 3:29 am

Airplay,

I recommend that you reread the TWA 727 incident, I think that you will find that the pilots where indeed following the AOM, This crew were indeed heroic in saving the lives of the passengers.
If you dont believe me or the reports, I recommend contacting ALPA and ask how their investigation turned out.

Fr8t.
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Flaps At Altitiude

Wed Aug 29, 2001 5:46 am

Yes.....why would a labour union lie to us?

 Smile

I believe this incident involves much which is open to interpretation. I've read enough to form my opinion at this point and I don't think it will change any time soon.

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