Rducky From United States of America, joined Oct 2003, 72 posts, RR: 0 Posted (12 years 3 months 6 days 9 hours ago) and read 8734 times:
A simple question, earlier this past week I flew on AA 757, from MIA-MCO, with a extremely light load, and I was looking out the window at the trailing edge flaps I couldn't help but wonder, how fast they retracted the flaps, it seemed like they were completely retracted below 1000'. I know the schedule for retracting the flaps depends on the weight of the aircraft and noise abatement procedure. Is it common to retract the flaps below 1000' when the weight of the aircraft isn't a factor, like leaving very light?
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 66
Reply 1, posted (12 years 3 months 5 days 16 hours ago) and read 8632 times:
Sorry your question has not yet attracted a response from someone who knows the 757 better than I do. I have the type rating but did not fly it very much. Certainly not much of an authority.
However, the book says that we would typically hold V2 + 15 knots to 1000 feet AGL, then accelerate to VREF + 80. We may select flaps up at VREF + 60 and accelerating. With more typical heavier loads we might accelerate by setting 100 fpm on the vertical speed and go through the flap retract schedule.
Flap limit speeds are 210 knots for flaps 15, 220K for flaps 5 and 240K for flaps 1.
This plane is a hotrod and MIA-MCO the fuel load would be very light you probably would have been bumping a very high deck angle and gaining speed approaching the flap limit speed. I doubt that they would have retracted the flaps below 1000' AGL but maybe immediately on reaching that altitude and just kept them coming up. Likely they did not have to drop the nose much to accelerate at that weight and the visual effect must have been rather like a space shuttle launch.
Yeah, it is a fun airplane.
Happiness is not seeing another trite Ste. Maarten photo all week long.
AM From Mexico, joined Oct 1999, 600 posts, RR: 2
Reply 2, posted (12 years 2 months 3 weeks 6 days 14 hours ago) and read 8450 times:
I've noticed the exact same thing on 757 take-offs. I particularly followed flap retraction with more attention during a take-off from MEX last September. We were going to ORD, fuel for the trip was 35200lbs (I was allowed into the flight deck before gate departure), for an estimated flight time of 3 and a half hours. Passenger load was at approximately 60%. We used flaps 15. V1=133kts, VR=133kts, V2=135kts.
I used my scanner for the first 10 minutes of the flight, so I could know better what was going on.
Acceleration height (when accelerating from V2+15 to 250kts) was 1000'. We took-off, and about 20 seconds into the flight the pilot not flying checked-in with departure at 8200'. Mexico City's elevation is 7300', so we were just 100' from acceleration height. Immediately after his report, the engine spool-down for climb power was felt, and the nose pitched down to accelerate. Flap retraction began about 10 seconds after that, so we were already above 1000'. The wing was completely clean before an intersection called VASOS, which is located 5 miles from the airport. The 757 had gone from flaps 15 to flaps up in less than a minute and a half. We couldn't have been higher than 3000' AGL.
Hope this helped a little bit.
"... for there you have been and there you will long to return."
DeltaGuy From , joined Dec 1969, posts, RR:
Reply 3, posted (12 years 2 months 3 weeks 6 days 2 hours ago) and read 8404 times:
All depends on the weight and what's written in the Speed Book for that particular weight. I've been on the 757/767 with a practically empty load, on a short JAX-ATL hop....the sucker climbs like a banshee, 6,000 FPM initially and then 4,000 on later climbout. You wouldn't believe how fast the flaps/slats come in, they have to be brought in quick so that you don't overspeed em. And this is with DERATED thrust. (Best time I had was on a Delta B767-300ER....had the ER engines, but wasn't an "ER" so to speak, 'twas domestic config...it was a rocketship)
On the flip side, you may have a climbout that takes awhile for the flaps/slats to come in, as you're heavy and can't accel. to 250 very fast. Remember, 250 kts is the "speed limit" below 10K feet, at least in the US.
'comon SlamClick....give yourself some more credit! Anyone with a type rating is more than qualified to answer these questions. MUCH better than a layman like me