theflcowboy
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Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 11:46 am


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Why would a plane land not using full flaps?
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N231YE
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 12:11 pm

Noise control is one of the reasons...
 
IAHFLYR
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 12:23 pm

I know on the B738 and B739 CO uses flaps 30 most of the time to lessen the tail strike possibilities.
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3DPlanes
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 12:31 pm

More flaps equal more drag, which for a stabilized approach means more thrust required... Providing another source of noise, and of course using more fuel.

Coming from a GA perspective, I would think that for the bigger planes, the runway length and/or landing weight would be the major factors for determining how much flap to use.

In some GA planes, its routine to not use full flaps - unless you need the short field performance. Others use full flaps on most every approach, unless you want to minimize the effect of gusts and/or a crosswind.
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theflcowboy
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 1:11 pm

Quoting IAHFLYR (Reply 2):

Can you explain this more? How does this reduce tail strike possibilities?
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KELPkid
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 1:15 pm

Well, for one, if I turn final and I'm below the VASI, I'm not going to add full flaps, because I'll also be adding tons of power to maintain altitude until I'm back to red over white...
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2H4
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 1:27 pm




Quoting Theflcowboy (Reply 4):
Can you explain this more? How does this reduce tail strike possibilities?

Extending the flaps increases the angle of attack. This reduces the deck angle required to maintain a given angle of attack. Shallower deck angle in the flare = less chance of a tailstrike.  Smile


2H4


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DKCFII
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 2:17 pm

This may apply more to smaller aircraft, but when there's really strong crosswinds or gusty conditions I use less flaps. It helps in maintaining directional control of the airplane, and allows for more versatility in terms of changing your flight config should things go awry.
 
rendezvous
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 3:00 pm

using flaps may reduce the deck angle for the same airspeed, but generally the use of them is to reduce the approach speed, which means it would be a similar deck angle whether flaps 30 or 40 were used.
 
ThirtyEcho
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 6:29 pm

Control surface authority increases with airspeed; the rudder, ailerons and elevators have more "power" at higher airspeeds. If you are landing in a gusty, crosswind environment, this is what you want, You don't want to be loitering at low speed over the runway while being blown this way and that way with low control surface authority. A lower flap setting will give you a higher touchdown speed.

When I began flying, many decades ago, flaps were regarded as a "crutch" used by bad pilots. If you needed to kill altitude and airspeed during an approach, you did a sideslip.
 
FrancoBlanco
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 8:56 pm

While most larger aircraft fully extend the flaps for landing (except for crosswind landings, engine-out landings, etc.), the 737 usually uses flaps 30. Flaps 40 is only used for short fields, high landing weight, etc. Flaps 40 is also more common on 738 and 739 models, on the other hand, as already mentioned, it increases the possibilty of tail strikes.

From my understanding, the original 737 inherited the wing from the 727 (which also had a flaps 40 position). Since the 737 is a lot shorter and lighter than the 727 (at least the classic models), flaps 40 are not needed most of the time.

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PhilSquares
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 9:40 pm

Quoting FrancoBlanco (Reply 10):
While most larger aircraft fully extend the flaps for landing

On the 744/747 flaps 25 and 30 are considered landing flaps. It is just a matter of company SOP.
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vikkyvik
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RE: Why Not Fully Extend Flaps When Landing?

Mon Feb 26, 2007 11:34 pm

Quoting 2H4 (Reply 6):
Extending the flaps increases the angle of attack. This reduces the deck angle required to maintain a given angle of attack. Shallower deck angle in the flare = less chance of a tailstrike.

So what you just told me is that more flaps = shallower deck angle. That's correct, but it doesn't exactly explain:

Quoting IAHFLYR (Reply 2):
I know on the B738 and B739 CO uses flaps 30 most of the time to lessen the tail strike possibilities.

unless there's something I'm missing  Smile

Maybe it just takes a lot of flare to arrest the descent on a flaps-40 landing?

Quoting FrancoBlanco (Reply 10):
While most larger aircraft fully extend the flaps for landing (except for crosswind landings, engine-out landings, etc.),

I'm not entirely sure that's accurate. As Phil said, the 744 has two landing flap settings. I believe that many Airbus aircraft can use the either of the highest two flap configs for landings. This is just what I remember reading, though.

~Vik
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EridanMan
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RE: Why Not Fully Extend Flaps When Landing?

Tue Feb 27, 2007 3:04 am

Yeah, I'm kinda confused about the tailstrike thing too, unless the argument is more flaps = less chance of tailstrike (in which case it hasn't been stated well).

Anyone whose landed a clean plane knows that you really have to get the nose WAY up in the flare.
 
IAHFLYR
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RE: Why Not Fully Extend Flaps When Landing?

Tue Feb 27, 2007 4:54 am

Quoting Vikkyvik (Reply 12):
unless there's something I'm missing

I have simply been told this by some of their crews so certainly no first hand knowledge and yes my initial thought was a lower deck angle as well.....I know they (CO) uses flaps 30 on those alot with ref speeds in the 155 KIAS range, they catch the preceeding arrival pretty quick on final.

Quoting Vikkyvik (Reply 12):
Maybe it just takes a lot of flare to arrest the descent on a flaps-40 landing

And lots of power as well....chop the power I'm told on the 800/900 with flaps 40.....better hang on as it is coming to the runway in a hurry.

Again, only passing on what I'm told from guys who drive them around....so I offer that caveat!  Smile
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FredT
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RE: Why Not Fully Extend Flaps When Landing?

Tue Feb 27, 2007 7:29 am

If you need to get a steep climb gradient in the event of going missed, you want to land fast if the runway length will permit it. Higher speed on the approach means more energy to convert into altitude quickly. Not to mention that in many aircraft the climb performance will not be optimum to begin with with full flaps.

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/Fred
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CosmicCruiser
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RE: Why Not Fully Extend Flaps When Landing?

Tue Feb 27, 2007 9:32 am

On the MD-11 the use of flaps 50 will decrease stop dist by only about 500' ft. but adds more stress on the airframe. Flaps 35 is normal with 50 being used mostly for CATIII.
 
DigbyDude
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RE: Why Not Fully Extend Flaps When Landing?

Wed Feb 28, 2007 8:03 am

Not a pro as one can probably tell, but I recall when coming into land on a 752, when the flaps were set the front of the plane felt to be pointing downwards quite a lot, is this just a feeling, or on a 752 does the plane actually point nose down during approach ?

Adam
 
MDorBust
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RE: Why Not Fully Extend Flaps When Landing?

Wed Feb 28, 2007 8:59 am

Quoting DigbyDude (Reply 17):
...or on a 752 does the plane actually point nose down during approach ?

What phase of the approach?

Every plane that I can think of has it's nose down at some point in the approach. Only late in the approach do planes start flying in a nose up attitude.
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highflyer9790
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RE: Why Not Fully Extend Flaps When Landing?

Wed Feb 28, 2007 9:21 am

Quoting MDorBust (Reply 18):
Every plane that I can think of has it's nose down at some point in the approach. Only late in the approach do planes start flying in a nose up attitude.

the heavier the aircraft and the slower the aircraft the earlier it will pitch nose up. generally, most commercial aircraft start to go noticably nose up during the flare, starting around 200 feet. in GA aircraft, it really only starts in the flare, around 20 feet!  Smile

generally, i wont go full flaps with gusty conditions (C172) because it makes the plane easier to handle, flying the approach about 10 kts faster until the threshold.
121
 
KELPkid
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RE: Why Not Fully Extend Flaps When Landing?

Wed Feb 28, 2007 10:44 am

Quoting MDorBust (Reply 18):
Every plane that I can think of has it's nose down at some point in the approach. Only late in the approach do planes start flying in a nose up attitude.

I used to drive home down Interstate 205, right by the approach end of RWY 28L and 28R at PDX. By the time they crossed I-205, they were already in a nose high attitude. It looks strange...I'd say the one that most amazed me (due to the apparent high alpha) was FX's MD-11's...not sure if that's due to FX's flight procedures or the nature of the MD-11  Wink
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highflyer9790
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RE: Why Not Fully Extend Flaps When Landing?

Wed Feb 28, 2007 10:55 am

Quoting KELPkid (Reply 20):
not sure if that's due to FX's flight procedures or the nature of the MD-11

nature of the MD-11, i think  wink 
121
 
CosmicCruiser
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RE: Why Not Fully Extend Flaps When Landing?

Wed Feb 28, 2007 8:54 pm

Quoting KELPkid (Reply 20):
I'd say the one that most amazed me (due to the apparent high alpha) was FX's MD-11's...not sure if that's due to FX's flight procedures or the nature of the MD-11

There are no procedures here that dictates an app. pitch that's particular to FEDEX. The MD-11 has about a 3 deg. nose up att from glide slope intercept down. The flair takes you to about 6 or 7. At 11 or more you''ll hit the tail. We fly the jet by the manuf. specs. With flaps 50 it will be lower att. but NEVER a negative att.Personally I''ve never flown a jet that DID have a nose low app attitude. I know some w/o slats (short DC-9) may but it isn''t the norm.
 
usair320
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 8:51 am

Well in the Cessna 150 that I fly it is because 40 degrees of flap is to much drag for the 8,000 ft runway I land on. $0 degrees can cause a hell of a lot of drag resulting in one hell of a stall.
 
CosmicCruiser
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 9:03 am

Quoting Usair320 (Reply 23):
Well in the Cessna 150 that I fly

If you notice I said jet. I too have a whole bunch of time in small Cessnas and understand what you're saying.

Quoting Usair320 (Reply 23):
40 degrees of flap is to much drag for the 8,000 ft runway I land on.

What's the runway have to do with it?
 
KELPkid
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 9:08 am

Quoting Usair320 (Reply 23):
40 degrees of flap is to much drag for the 8,000 ft runway

The Cessnas that don't have flaps restricted to 30 deg. can make some amazing drop-in approaches right on the numbers at short mountain strips  However, 40 degrees + side slip is a bad combination (in the 172, IIRC, this causes the tail to buffet, not dangerous, but disconcerting...). I'd be nervous using anything above 20 degrees with a strong x-wind component, however...

EDIT: spelling

[Edited 2007-03-01 01:20:32]
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2H4
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 9:09 am




Quoting Usair320 (Reply 23):
40 degrees can cause a hell of a lot of drag resulting in one hell of a stall.

It's been awhile since I've flown a 150, but I don't recall a lower flap setting resulting in more violent stall characteristics...


2H4


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IAHFLYR
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 9:15 am

Quoting Usair320 (Reply 23):
Well in the Cessna 150 that I fly it is because 40 degrees of flap is to much drag for the 8,000 ft runway I land on.

Heck 40 degrees of flaps on a C150 would be way too much drag on a 2,500' runway!!!  Smile
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KELPkid
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 9:15 am

Quoting 2H4 (Reply 26):
It's been awhile since I've flown a 150, but I don't recall a lower flap setting resulting in more violent stall characteristics...


2H4

I recall my 1st flight instructor teaching me to do an approach configuration stall in a 150 whose flaps went to 40 degrees...on recovery, he taught me that the second order of business, after shoving in the coals and before bringing the nose up, was to lose 10 degrees of flaps (the only situation where bringing the nose up wasn't the second order of business). This was all from a field whose field elevation was 4454' Big grin
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2H4
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 9:22 am




Quoting KELPkid (Reply 25):
The Cessnas that don't have flaps restricted to 30 deg. can make some amazing drop-in approaches

Indeed. I love it when the scenery seems to come up more quickly than it seems to go past...  biggrin 





Quoting IAHFLYR (Reply 27):
Heck 40 degrees of flaps on a C150 would be way too much drag on a 2,500' runway!!!

When landing, I am of the opinion that...so long as forward progress is possible...there's no such thing as too much drag. Just like how, during takeoff, there's no such thing as too much thrust....  Wink


2H4


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ThirtyEcho
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 5:54 pm

Gotta love those 40 degree flaps on the early Cessnas. I've dropped into many a 2000 foot long and 35 foot wide runway, over the tops of 50' pine trees, in East Texas in my youth. The best Cessnas had the mechanical flaps; just hold the detent in and play the flaps like spoilers with the throttle at idle (I always "cleared" the engine, first) and, then, do the flare, dump the flaps and taxi off with room to spare.

My instructor was an AA Captain in 1937. He probably could have done the same thing in a DC-3.
 
BAE146QT
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 10:10 pm

Quoting ThirtyEcho-but-not-really:
I've dropped into many a 35 foot long and 2000 foot wide runway,

If your CFI used to be a Naval aviator;

"Man, that was a short runway."
"Yeah but look how *wide* it is!"
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pygmalion
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RE: Why Not Fully Extend Flaps When Landing?

Thu Mar 01, 2007 11:34 pm

For most aircraft, the change in wing shape as a result of adding flaps does two things, It increases lift and adds drag. For any given angle of attack, to about 15-20 degrees of flap extension, you increase lift faster than drag. Over 20 degrees extension, the drag goes up a lot faster and the lift only goes up slowly. For large transport aircraft, takeoff flaps are used to shorten take off distances. Landing flaps are used more to slow the big mutha down than anything else. When a LCA goes nose down on approach, you are steepening the descent angle and using the flaps to prevent overspeed. Small civil aircraft normally dont have enough engine to get much benefit from TO flaps and dont need to reduce speeds so much to land as the runaways are easily long enough for flap up landings.
 
KELPkid
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RE: Why Not Fully Extend Flaps When Landing?

Fri Mar 02, 2007 12:32 am

Quoting Pygmalion (Reply 32):
Small civil aircraft normally dont have enough engine to get much benefit from TO flaps

Well, in most Cessna high wing models a short and/or short and soft field takeoff calls for 10 deg. flaps...milked up once your airborne in ground effect, as the drag on climbout will substantially lower your rate of climb  Smile

Quoting Pygmalion (Reply 32):
dont need to reduce speeds so much to land as the runaways are easily long enough for flap up landings.

Very true. I once did a flaps up landing at ELP in the 172 (because the controller told me to keep the speed up for the 737 that was behind us) and maintained 90 kts. groundspeed on final [gotta love GPS!  Wink ]. We floated about halfway down runway 26L (9000 feet) before the mains finally kissed...something about the Cessna 172, excess airspeed, and a wing that loves to fly when you carry extra airspeed  Smile
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jetmech
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RE: Why Not Fully Extend Flaps When Landing?

Fri Mar 02, 2007 10:39 am

Quoting Theflcowboy (Thread starter):
Why would a plane land not using full flaps?



Quoting PhilSquares (Reply 11):
On the 744/747 flaps 25 and 30 are considered landing flaps. It is just a matter of company SOP.

I think that one of the reasons full ( 30 degrees ) flaps is sometimes not used by particular operators of B744's is due to brake wear considerations. Apparently, using flaps 25 requires a slightly higher approach speed. This means that the carbon brakes must absorb more energy. Apparently, the increased heat that the brakes are subjected to by absorbing this extra energy is somehow beneficial for the life of carbon brakes. I'm not sure of the exact mechanism, but apparently, carbon brakes wear as a function of the number of applications, and not so much as a function of the amount of heat absorbed. IIRC, QF were doing flaps 25 landings as SOP ( with the exception of runway 13 at Kai Tak ) until the Bangkok incident with VH-OJH.

Regards, JetMech
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PhilSquares
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RE: Why Not Fully Extend Flaps When Landing?

Fri Mar 02, 2007 10:44 am

Quoting JetMech (Reply 34):
IIRC, QF were doing flaps 25 landings as SOP ( with the exception of runway 13 at Kai Tak ) until the Bangkok incident with VH-OJH.

Actually, QF was a 30 flap landing company, min reverse and autobrakes 3. The increase in Vref is from 5-7 knots depending on your weight. The additional energy with flaps 25 isn't all that much. And you're correct in your statement about carbon brakes liking the heat.

For some airlines it's a matter of trading off some reverse thrust and flaps 25 or min reverse and flaps 30.
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jetmech
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RE: Why Not Fully Extend Flaps When Landing?

Fri Mar 02, 2007 12:05 pm

G'day Phil  Smile,

Yes, apparently QF was a flaps 30 company as stated in their B744 procedures manual. Apparently, maximum reverse thrust was also SOP although not specifically stated in the B744 procedures manual (p158). On the 6th December 1996, after a period of development, a 6 month trial of flaps 25 and idle reverse thrust SOP (with conditions) was approved (p164). These new landing SOP's were renewed for 3 month periods on 11th March 1997, and 5th June 1997(p165). On the 28th February 1997, these new procedure were incorporated into the B744 procedures manual (p165).

These SOP's, which were current at the time of the incident (23rd September 1999), stated a preferred flap setting of 25 and idle reverse thrust unless the situation (such as HKG Kai Tak runway 13) required otherwise (p49). The intention to follow these SOP's (flap 25 / idle reverse) was apparently heeded by the crew (p20), and indeed, the flaps were found to be in the 25 degree position upon examination of the aircraft (p27).

Apparently, the revised procedure with flaps 25 and idle reverse was instigated by a presentation from the brake manufacturer that revealed that carbon brake wear was reduced at higher temperatures (p158). It is interesting to note that QF showed early interest in the flaps 25 procedure (1993) for the 747 but subsequently rejected the proposal. Boeing also seemed to be somewhat luke-warm to the idea of reduced flap landings on it's aircraft (p167).

All page number references are with respect to the PDF version of the following ATSB report;

http://www.atsb.gov.au/publications/...999/AAIR/pdf/aair199904538_001.pdf

Regards, JetMech
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PhilSquares
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RE: Why Not Fully Extend Flaps When Landing?

Fri Mar 02, 2007 12:25 pm

G'day JetMech,

Not to hijack this to a QF analysis.....but

Quoting JetMech (Reply 36):
Boeing also seemed to be somewhat luke-warm to the idea of reduced flap landings on it's aircraft (p167).

If you check (p52) you'll find Boeing's recommendation about 25 v. 30 flap landings. Boeing had "no technical objection" to min reverse and 25 flaps, especially in light of noise abatement and flap wear. However, as everything with Boeing (insert aircraft mfgr) it came with the typical qualifiers.

However, what is interesting to note, if the crew had selected 30 flaps and done the same thing, the results would have been just about the same. The crew's reliance or lack of situational awareness with respect to the autobrakes becoming disarmed (pg 25) and the lack of deceleration is one of the key factors in the incident. That coupled with the "You got it, I got it, we got it" approach in the last 100' and subsequent decision to go around then not.....is what sealed their fate.
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jetmech
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RE: Why Not Fully Extend Flaps When Landing?

Fri Mar 02, 2007 3:13 pm

Quoting PhilSquares (Reply 37):

G'day Phil  Smile,

Thanks so much for the input! It is always fascinating and most informative to get the pilots perspective on such issues bigthumbsup !. The language of the ATSB report with respect to Boeing's happiness with the flap 25 technique is somewhat confusing (p52). The way I read it, Boeing was actually not happy to provide a "no technical objection" to the flap 25 procedure  Confused . The language confuses me as it is a sentence that contains a double negative.

As you mentioned, any sort of technical request to aircraft manufacturers seems to have many conditions applied. I can actually understand this approach by Boeing. I can only image the sort of legal trouble they may get in if they approve a procedure which contributes in even a small way to an incident. Out of curiosity, what is the flap and thrust reverse technique you usually apply?

Regards JetMech
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PhilSquares
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RE: Why Not Fully Extend Flaps When Landing?

Fri Mar 02, 2007 4:20 pm

Quoting JetMech (Reply 38):
Out of curiosity, what is the flap and thrust reverse technique you usually apply?

I really prefer flaps 25, moderate reverse and autobrakes 2. Once I'm down to 100 knots or so, I tap the brakes to deactivate the autobrakes and then try to be at idle reverse at 80 and out by 60. Using flaps 25 takes a lot of stress off the flaps (the BA problem) and it also saves about 100Kgs of fuel.

However, landing at 300tonnes, in ANC, with a snowy runway it's flaps 30, max reverse and autobrakes 3. The 744 isn't all that hard to get stopped, but in places like SIN/BKK if the runway is wet you really need to make a "firm" touchdown to ensure you don't have the same problems QF did.

There's a big reluctance to use reverse thrust these days. I think flight ops has fallen into the trap that was evident in the ATSB report. I guess my philosophy is if they didn't want you to use reverse they wouldn't put it on the airplane.

Cheers!
Fly fast, live slow
 
OldAeroGuy
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 12:04 am

Quoting 2H4 (Reply 6):
Extending the flaps increases the angle of attack.

If you extend flaps at constant airspeed, CL will increase so angle of attack needs to decrease to maintain level flight.

Generally speaking, increased flap deflections reduce the possibility of a tail strike since the angle of attack for approach and during flare is reduced, even at the lower operating speed allowed by the higher flap setting.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
411A
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 1:35 am

Not using the maximum flap setting for landing, began a long time ago, with Pan American, with B707 aircraft, circa 1960, after a couple of years operation with the airplane.
The landing flap setting on these old 707's was 50 degrees, and PanAmerican asked Boeing for landing distance/Vspeed performance data on landing with flaps 40.
The answer received from Boeing was...
At max landing weight, wet or dry runways, the AVERAGE increase in landing distance was 800 feet, and the added increment to Vref was 2 knots, when landing with flaps 40.
PanAm then obtained runway charts for all normal destinations, that contained landing field length requirements for landing both with flaps 40 and flaps 50, and left it up to the Captain on the concerned flight to choose what flap setting was desired, with consideration to the airfield conditions being of primary importance.
It was stressed however, that since these straight-pipe (non-fan) engines needed a considerable time to spool up, that flaps 50 should be used if there was any problem expected.
Most Captains elected to use flaps 50, most of the time.
With the fan powered aircraft, I normally used flaps 40 for landing, unless the landing distance was critical.
 
vikkyvik
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 3:36 am

Quoting 411A (Reply 41):
It was stressed however, that since these straight-pipe (non-fan) engines needed a considerable time to spool up, that flaps 50 should be used if there was any problem expected.
Most Captains elected to use flaps 50, most of the time.

Is that because you'd be at a higher power setting for a flaps 50 landing?

There's a few things involved that I can see, in terms of which is better for go-arounds. Flaps 50 - engines are already at higher thrust. Flaps 40 - airplane is moving faster, and there's less flaps to stow upon go-around.

I assume that the engines already being at higher thrust outweighs the other variables?

Thanks...

~Vik
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OldAeroGuy
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 4:57 am

Quoting Vikkyvik (Reply 42):
I assume that the engines already being at higher thrust outweighs the other variables?

For the JT3D series, very much so.
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vikkyvik
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 5:21 am

Quoting OldAeroGuy (Reply 43):
For the JT3D series, very much so.

Gotcha  checkmark 

Thanks.

~Vik
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wing
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 5:53 am

Flaps 30 is the normal landing flap setting for 737-400 series.(Period)
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jetmech
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 11:21 am

Quoting PhilSquares (Reply 39):

Thanks again Phil!

It seems as though you are allowed to exercise much discretion and judgement in the landing configuration you choose to utilise. I have always believed that the pilot should have the ultimate say in how they operate their aircraft despite any SOP's. I guess when SOP's for non-emergency procedures become ingrained, pilots may lose the impetus to make choices based on their own judgement and experience.

Regards, JetMech
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ThirtyEcho
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 7:21 pm

"Man, that was a short runway."
"Yeah but look how *wide* it is!"


Good for you; you got the joke. There was a Cub pilot at my local airport who would, when the wind was just right, gun it from the taxiway and take off across the runway. He was a bootlegger who flew booze orders from our wet county into a dry county.
 
2H4
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RE: Why Not Fully Extend Flaps When Landing?

Sat Mar 03, 2007 11:15 pm




Quoting OldAeroGuy (Reply 40):
If you extend flaps at constant airspeed, CL will increase so angle of attack needs to decrease to maintain level flight.

Generally speaking, increased flap deflections reduce the possibility of a tail strike since the angle of attack for approach and during flare is reduced, even at the lower operating speed allowed by the higher flap setting.

Thanks, OAG. I think I was making an incorrect correlation between chord line and AOA.


2H4


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pilotaydin
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RE: Why Not Fully Extend Flaps When Landing?

Sun Mar 04, 2007 6:27 pm

sometimes it is good to use flaps 30 on the 737 because incase of a go around, the climb performance is much greater, and at places like Pristina or Sarajevo where there is terrain issues, a single engine situation at the point of go around would seriously effect the a/c in flap 40 position as far as approach and landing climb gradients go...
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