MerlinIIIB From Norway, joined Aug 2005, 121 posts, RR: 0 Posted (9 years 6 months 4 weeks 1 day 4 hours ago) and read 13347 times:
Yesterday I was a passenger on board a 737-600 for a late evening 45 min flight. Approx 50 pax on board and a 3900 m. Rwy, winds calm, +5C. I was amazed at the low (derated) lake-off thrust selected and the very poor initial rate of climb. About one minute into the flight, a significant increase of thrust was felt. The noise outside must have been significantly reduced!
Is there a defined derated thrust limit, or is it up to the pilots to decide the minimum thrust required based on runway length, weights etc.?
The landing took place without reverse thrust (wheel breaks only), and I have experienced that only once before. How common is that?
WILCO737 From Greenland, joined Jun 2004, 9250 posts, RR: 76
Reply 1, posted (9 years 6 months 4 weeks 20 hours ago) and read 13315 times:
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I can only say it for the Classic 737, I dont fly the NG anymore!
The max allowed thrust reduction is 25% from the max allowable thrust. That gives you an assumed temperature of about 60°, this is the highest I ever had. Then you have a take off N1 of about 80% (only spoken for the LH 733) and then you have 2 steps in climb power: full climb power, CLB-1 and CLB-2! the last one is the lowerst climb power setting and increases engine live and noise! Sure you dont climbg that fast then, because you use less power, maybe the pilots added full climb power then to get a better climb performance thats why the thrust increase...
Landing without reverse, happen, but not too often! Usually you use idle reverse only (spoken for LH) for safety reasons you can use a lot more! But when I land in FRA, 4000m runway and runway dry, not a hot day (otherwise maybe hot brakes) and there is no traffic behind us then just let it slow down on her own... and then exit the runway when possible! Maybe there was a problem with the thrust reverser that they are blocked and cannot be used, which is allowed (check MEL prior flight)
From Oslo Gardermoen Airport, Rw 01L. Landing was at Stavanger Sola airport Rwy 18. I fly 3-4 times a month, and this was my second landing at Sola in 10 years without reverse thrust. I have never experienced it while landing at any other airport, and on both occasions it was a late evening landing in dry conditions. Rwy 18 at Sola is approx 2700 meters long, Gardermoen 01L almost 4000 m.
Thanks Wilco737 for providing the facts on the Classic 737.
Ryanair737 From , joined Dec 1969, posts, RR:
Reply 5, posted (9 years 6 months 3 weeks 6 days 12 hours ago) and read 13181 times:
You have just experienced a normal assumed temp takeoff on the B737!
Quoting MerlinIIIB (Thread starter): Is there a defined derated thrust limit, or is it up to the pilots to decide the minimum thrust required based on runway length, weights etc.?
They work out before departure how much they will be able to de-rate on the takeoff; this calculation is based on the atmospheric conditions outside, weight of the aircraft, runway length and the airfield pressure in MB/HP. This assumed temperature is then entered into the N1 Limit page in the B73G FMC (Flight Management Computer), the engines on takeoff automatically set to the reduced N1 when the TOGA buttons are pressed.
Quoting MerlinIIIB (Reply 4): I have never experienced it while landing at any other airport, and on both occasions it was a late evening landing in dry conditions.
To be good neighbours at night to the many people who live near the airport many pilots decide to use idle reverse or no reverse whatsoever and just select a higher setting of autobrake or brake more firmly manually.
Prebennorholm From Denmark, joined Mar 2000, 6717 posts, RR: 54
Reply 7, posted (9 years 6 months 3 weeks 5 days 7 hours ago) and read 13081 times:
At CPH nobody uses reverse thrust, except "idle reverse" which isn't really reverse power, but only being more ready in case of a wheel brake problem.
At CPH it is simply forbidden to use reverse power except in case of wheel brake problems or an emergency etc. Consequently I experience no reverse thrust at roughly half of the landings.
Advantage is less noise on Copenhagen city. Disadvantage is more wheel brake mnt.
Some ten or fifteen years ago most planes landing at CPH used reverse thrust with very much reduced power for the same reason, never anything like full power. But that's long time ago.
A related joke: CPH is surrounded by noise recording equipment and every operation is recorded noise wise. One day many years ago Maersk Air got a letter from the local CAA requesting an explanation for a gross overstepping of the nominal max allowable noise during a B733 take-off.
Maersk Air explained that the captain testified that the take-off was nominal and in all respects performed according to the standard take-off and climb out profile. Therefore they requested a tape copy to be analyzed.
When playing the tape they heard a dog barking - and a very faint background jet engine noise.
Always keep your number of landings equal to your number of take-offs
MerlinIIIB From Norway, joined Aug 2005, 121 posts, RR: 0
Reply 8, posted (9 years 6 months 3 weeks 4 days 6 hours ago) and read 13050 times:
Quoting Chksix (Reply 6): On all my flights as pax on SAS domestic I've very rarely seen reverse thrust used.
I guess we envy the longer runways in Sweden and Denmark ... I was back in Stavanger this week and spent two nights at the airport hotel watching about 20 SAS 737 landings - all with very noisy reverse thrust. Or did I observe "idle reverse" and not full reverse, is it possible to tell the difference by listening...
I hope that a 737 pilot will comment on the following quote:
Quoting Prebennorholm (Reply 7): At CPH nobody uses reverse thrust, except "idle reverse" which isn't really reverse power