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FR 738 Take Off  
User currently offlineF.pier From Italy, joined Aug 2000, 1531 posts, RR: 9
Posted (12 years 6 months 2 weeks 6 days 13 hours ago) and read 2650 times:

I sincerely don't know if it's only a Ryanair procedure, but I realized that every time the plane is at the beginning of the runway, ready to take off, the pilots add thrust to the engines, then they reduce it quite a lot, and finally they increase the power for the takeoff.

Is it a normal procedure or it's only a Ryanair procedure?

Why they do this?

5 replies: All unread, jump to last
User currently offlineFritzi From United Arab Emirates, joined Jun 2001, 2763 posts, RR: 2
Reply 1, posted (12 years 6 months 2 weeks 6 days 11 hours ago) and read 2582 times:

I think its standard procedure with all opperators.

First you get the engines stabalized at around 40% N1, then you throttle up to the desired amount of thrust for the takoff.

User currently offlineCancidas From Poland, joined Jul 2003, 4112 posts, RR: 10
Reply 2, posted (12 years 6 months 2 weeks 6 days 10 hours ago) and read 2542 times:

on airbus a/c, you need to do that to disengage taxi mode. not sure as to why you do that on boeings.

"...cannot the kingdom of salvation take me home."
User currently offlineB747Skipper From , joined Dec 1969, posts, RR:
Reply 3, posted (12 years 6 months 2 weeks 6 days 9 hours ago) and read 2543 times:

The procedure to set takeoff power is basically the same in all airplanes.
After line-up on the runway, you advance the power levers to somewhat of a "higher" N1 or EPR power setting, this to "spool up" the engines, meaning by that that many bleed valves close at such a power setting.
When the engines are stabilized, and "spooled", a quick look at the numbers indicated (the flight engineer, in my old 747), the PF sets the takeoff power, from "spooled up", engines generally accelerate equally, and "adjustments" are done by our flight engineer.
At 80 kts, we put the "auto throttle" switch ON if we want to use it.
For our airplanes (we use EPR since we have JT9D-7Q engines) we set the "takeoff EPR" initially (that number is valid up to 80 kts), should the flight engineer need to "adjust" the power beyond 80 kts, he would have to use the "go around EPR" (somewhat lower number) since using straight "takeoff EPR" above 80 kts would possibly exceed the EPR limit of the engine...
Each engines are somewhat different, but the procedures are equivalent. I have flown airplanes with JT3D, JT4A, JT8D, JT9D, CF6 and CFM engines, while numbers are obviously different, the procedures remain the same.
Happy contrails  Smile
(s) Skipper

User currently offlineWing From Turkey, joined Oct 2000, 1601 posts, RR: 23
Reply 4, posted (12 years 6 months 2 weeks 6 days 8 hours ago) and read 2498 times:

On 737 autothrotle is set to ARM position when the aircraft lined up with the centerline.Then the PF takes the controls advances the throttles to aproximetely 40 % N1.when both engines spooled up equally and stabilised you press the TO/GA then the A/T advances the thrust lever to desired N1 setting.That helps pilot to see if the engines responding normally and avoids uneven throttle movement which can cause loss of allignment with the runway centerline.

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User currently offlineAAR90 From United States of America, joined Jan 2000, 3590 posts, RR: 44
Reply 5, posted (12 years 6 months 2 weeks 5 days 10 hours ago) and read 2344 times:

the pilots add thrust to the engines, then they reduce it quite a lot,

I suspect the reduced sound you hear is the engines nearly matching RPMs at the ~40% spool up point. Any change in the CFM56 engine's RPM causes a fairly significant increase in noise compared to any stable RPM noise level. An engine noise level decrease is noticable even in the cockpit whenever I allow the engines to fully stabilize prior to advancing to T/O power --normally I don't wait for a complete stabilization, but rather just "close enough" to know they will spool up without problem(s).

FWIW, a rolling takeoff is the standard takeoff procedure at AA. As pointed out earlier, 99+% of the runways we use are a lot longer than "balanced field length."

*NO CARRIER* -- A Naval Aviator's worst nightmare!
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