In the above and several other 747-400 takeoff videos, (as well as personal experiences looking out the window) I have noticed that the high weight climb profile for the 744 seems to call for keeping flaps extended for the first few minutes of climb.
What, if any, would the exact parameters for this be in the FOM?
In the video, I would hazard a guess they departed at flaps 20 and maintained that setting for the first couple minutes of climb. Flaps 10 looked to be set another couple minutes with the wing not fully cleaned up until nearly 4 minutes after getting airborne. I am aware that the 744 and other similar-sized aircraft are not particularly great climbers at high weights by any measure, so I'm curious as to the benefits and trade-offs associated with leaving the flaps extended quite so long.
Many thanks in advance for satisfying my curiosity.
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Starlionblue From Hong Kong, joined Feb 2004, 15873 posts, RR: 66 Reply 1, posted (4 months 3 weeks 5 days 18 hours ago) and read 2471 times:
Quoting Aaron747 (Thread starter): In the above and several other 747-400 takeoff videos, (as well as personal experiences looking out the window) I have noticed that the high weight climb profile for the 744 seems to call for keeping flaps extended for the first few minutes of climb.
What, if any, would the exact parameters for this be in the FOM?
Wild guess here but flaps cannot be retracted prior to a certain speed. So if you want to keep a certain angle of climb due to a required climb gradient at a high weight this predicates a lower speed on climbout. Ergo retraction later.
Anyway wild guess.
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Some departures call for speed limits until certain waypoints or altitudes. If that speed is below flap retraction speed (which varies with weight) then the flaps stay.
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vikkyvik From United States of America, joined Jul 2003, 8228 posts, RR: 28 Reply 3, posted (4 months 3 weeks 5 days 12 hours ago) and read 2316 times:
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I remember reading that at high TOW, a 747's min safe maneuvering speed (or whatever - I don't know the technical term) might be faster than the typical 250kt-under-10,000-feet speed limit at US airports. So my guess is, instead of requesting a higher speed, they leave the flaps out until they're clear of 10,000 feet (or clear of traffic that they may hamper by flying faster).
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Fabo From Slovakia, joined Aug 2005, 1111 posts, RR: 1 Reply 4, posted (4 months 3 weeks 5 days 12 hours ago) and read 2310 times:
Seems like a normal climb to me. Probably NADP1.
You climb until ~1500ft on takeoff speed, flaps out. Then you pull back to climb power and climb to 3000ft, still on take-off speed. Only then you start to speed up and retract flaps as you manage to speed up in a slight climb.
Could very well take a couple minutes for a heavy 747 to get to retraction... methinks.
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Quoting Aaron747 (Reply 6): OK, so they're staying dirty to stay under the limit then
If there is no other choice, yes. Normally is not necessary, as controllers clears us for high speed climb.
Quoting Aaron747 (Reply 6): Would that suggest that even a 744 at heavy TOW is more slippery than she looks?
Not really. The -400 has full maneuver capability during the flap retraction, unless TOW is above 680,000 lbs. in which case we are bank angle limited until Vref + 100.
Quoting Aaron747 (Reply 6): would getting in the neighborhood of Va as quickly as possible be the ideal?
Generally correct, until obstacle clearance or crossing altitudes restrictions are met. Then accelerate to climb speed.
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Starlionblue From Hong Kong, joined Feb 2004, 15873 posts, RR: 66 Reply 8, posted (4 months 3 weeks 5 days 2 hours ago) and read 2072 times:
Quoting B747FE (Reply 7): The -400 has full maneuver capability during the flap retraction, unless TOW is above 680,000 lbs. in which case we are bank angle limited until Vref + 100.
Out of curiosity, is that bank angle limit in place when flaps are out, or only during flap operation?
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B747FE From Hong Kong, joined Jun 2004, 230 posts, RR: 3 Reply 9, posted (4 months 3 weeks 4 days 23 hours ago) and read 2006 times:
Quoting Starlionblue (Reply 8): Out of curiosity, is that bank angle limit in place when flaps are out, or only during flap operation?
Above 680,000 lbs. you are still limited to 15 degrees until reaching Vref + 100 regardless of flap position.
Flap retraction would normally be commanded from flaps 1 position to flaps up at Vref + 80 KIAS, which happens to be Va for a clean wing if the aeroplane is below 680,000 lbs.
Regards,
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Qantas744ER From United States of America, joined Jun 2005, 1252 posts, RR: 4 Reply 10, posted (4 months 3 weeks 3 days 7 hours ago) and read 1709 times:
Quoting Aaron747 (Thread starter):
Was killing time going through some videos on YouTube and got to wondering about this:
In the above and several other 747-400 takeoff videos, (as well as personal experiences looking out the window) I have noticed that the high weight climb profile for the 744 seems to call for keeping flaps extended for the first few minutes of climb.
What, if any, would the exact parameters for this be in the FOM?
In the video, I would hazard a guess they departed at flaps 20 and maintained that setting for the first couple minutes of climb. Flaps 10 looked to be set another couple minutes with the wing not fully cleaned up until nearly 4 minutes after getting airborne. I am aware that the 744 and other similar-sized aircraft are not particularly great climbers at high weights by any measure, so I'm curious as to the benefits and trade-offs associated with leaving the flaps extended quite so long.
Many thanks in advance for satisfying my curiosity.
United has been using NADP-1 off 28L and 28R for a few years now. Hence on the 744, (they do both flaps 10 and 20 departures) thrust reduction height to CLB thrust is 1500' AGL (United has no CLB-1 and CLB-2 derate on their 744) and acceleration height to VREF+100kt (clean speed) is 3000' AGL.
Off all other runways at SFO they use the standard NADP-2 profile, which on the 744 means acceleration at 800' AGL and thrust reduction to CLB at flaps 5.
Quoting vikkyvik (Reply 3): I remember reading that at high TOW, a 747's min safe maneuvering speed (or whatever - I don't know the technical term) might be faster than the typical 250kt-under-10,000-feet speed limit at US airports. So my guess is, instead of requesting a higher speed, they leave the flaps out until they're clear of 10,000 feet (or clear of traffic that they may hamper by flying faster).
They will always accelerate to VREF+100kt (clean speed) on the 747 without asking ATC in the U.S. The reason being that ATC is well aware that a heavy 747 will have a clean speed above 250kt.
Some pilots prefer requesting, others simply go for it. After all, operating the aircraft safely trumps the 250kt/10000ft rule.
Also, having flaps 1 out until 10,000 would NOT make any pilot happy during icing conditions!
A very experienced B744 captain once said here, that in 20+ years of flying he had never encountered a situation where accelerating to VREF +100kt was not possible.
Fabo From Slovakia, joined Aug 2005, 1111 posts, RR: 1 Reply 11, posted (4 months 3 weeks 2 days 5 hours ago) and read 1486 times:
Quoting Qantas744ER (Reply 10): They will always accelerate to VREF+100kt (clean speed) on the 747 without asking ATC in the U.S. The reason being that ATC is well aware that a heavy 747 will have a clean speed above 250kt.
Not just that ATC are aware, it is actually stated in the FARs that the aircraft should maintain under 250 or minimum clean speed under 10K
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