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Engine Spool Up Before Take Off Power

Sxmarbury33 From United States of America, joined Oct 2000, 445 posts, RR: 0
Posted (11 years 1 month 1 week 5 days 6 hours ago) and read 2724 times:

I was wondering what is the average N1 of an aircraft engine to spool it up before take off power. Ive heard from 50N1 to 70N1 and also 1.05EPR to 1.2EPR is there an average or does it really change that much.

12 replies: All unread, jump to last

VC-10 From United Kingdom, joined Oct 1999, 3656 posts, RR: 42
Reply 1, posted (11 years 1 month 1 week 4 days 20 hours ago) and read 2575 times:

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1.05 EPR is Idle. T.O. EPR will be around 1.54

Idle N1 is around 28% while T.O. will up in the high 90's on average.

The actuals will depend on ambient temp and pressure.

Max Power From , joined Dec 1969, posts, RR:
Reply 2, posted (11 years 1 month 1 week 4 days 19 hours ago) and read 2553 times:

How can anyone really answer such a question with out knowing what engine? What is the average aircraft engine?? They are each a little different or a lot different and some like a few models of the Spey are always spooled up even at idle..

VC-10 From United Kingdom, joined Oct 1999, 3656 posts, RR: 42
Reply 3, posted (11 years 1 month 1 week 4 days 12 hours ago) and read 2523 times:

Max Power,

Please explain what you mean by :-

"and some like a few models of the Spey are always spooled up even at idle".

As someone who holds a type licence on the Spey I am curious

AAR90 From United States of America, joined Jan 2000, 3342 posts, RR: 51
Reply 4, posted (11 years 1 month 1 week 4 days 9 hours ago) and read 2501 times:

I think you're asking about spool up _prior_ to applying takeoff thrust, if so AA's 737-800 procedure is 40% N1, AA's MD90 procedure was Crying

1.20 EPR (same for MD80 I think), and its been a year since I flew the 767 or 757 and my memory doesn't go that far back. Wink/being sarcastic

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

Max Power From , joined Dec 1969, posts, RR:
Reply 5, posted (11 years 1 month 1 week 4 days 8 hours ago) and read 2504 times:

?? No idea what you mean a type licence on a Spey? I am talking about the Spey on the BAC1-11 200 series the engine was always "spooled up" at idle thrust. IE: power levers full retard to idle and no "delay" for spool up! It was always ready.??

JETPILOT From United States of America, joined May 1999, 3128 posts, RR: 37
Reply 6, posted (11 years 1 month 1 week 4 days 5 hours ago) and read 2487 times:

Impossible question to answer as every engine has its own operating range.

JET

Sxmarbury33 From United States of America, joined Oct 2000, 445 posts, RR: 0
Reply 7, posted (11 years 1 month 1 week 4 days 5 hours ago) and read 2478 times:

Ok sorry i diddnt know there was such a wide veriaty how about on a 763 with GE engines. If you need to know specific model of engine i have that so tell me if i need to post it.

VC-10 From United Kingdom, joined Oct 1999, 3656 posts, RR: 42
Reply 8, posted (11 years 1 month 1 week 3 days 23 hours ago) and read 2475 times:

Max,

Before the advent of the 747,DC10 etc in the UK you had to hold a Type licence on a particular airframe/engine/electrics/instruments/radio before you could certify that particular aircraft. (You didn't need to hold all of them but if you were required to sign for engine work you had to hold the engine licence). To obtain the licence you had to pass a written exam on aircraft engineering subjects and then be orally examined by the Airworthiness Authority on those subjects plus the airframe/engine etc that you had applied for.

The Civil Aviation Authority deemed the early widebodie's too complex for any one man to be able to hold a type licence on, so they did away with the type licence. They thought the a/c were so complex you would become a systems specialist. In its place they issued you with a Licence without Type rating which cover the general aspects of aircraft maintenance. To certify these 'complex' aircraft your employer issued you with an approval after an oral examination on the aircraft with the Quality Department. So you ended up with an approval to certify the the whole airframe etc just like before, except you coudn't take it with you when you left that organisation.

Anyway back to the subject, I would say the Spey was always ready because it is a 'real' engine i.e when accelerating the engine you don't have to overcome the inertia of a fan and the thrust is all what is coming out of the exhaust.

Max Power From , joined Dec 1969, posts, RR:
Reply 9, posted (11 years 1 month 1 week 3 days 18 hours ago) and read 2467 times:

VC-10, Ok I understand now, thanks, I agree with you on the old spey, it was a good one but extreemly noisy Smile

Regards, Max

CX flyboy From Hong Kong, joined Dec 1999, 6129 posts, RR: 57
Reply 10, posted (11 years 1 month 1 week 1 day 14 hours ago) and read 2427 times:

I love noisy engines.

On our RB211-524G/Ts, we spool up to 1.10 EPR before hitting the TOGA switches.

F-WWAI From Andorra, joined Dec 1999, 131 posts, RR: 0
Reply 11, posted (11 years 1 month 1 week 15 hours ago) and read 2392 times:

it doesn't really matter at what initial thrust the engines are stabilized above idle before setting thrust for take off. please understand the reason for this procedure first:

the pre-stab is put in procedure to be sure that all engines depart from the same, above-idle, thrust setting during there acceleration to take-off power.
if they do not, a large x-wing thrust unbalance may establish before the aircraft reaches VMCG and the plane may leave the runway ....

in use:
CFM56 : 50 % N1
CF6-80 : 50 % N1
V2500 : 1.05 EPR (=about 50 % N1)
PW4000: 1.10 EPR ( guess what ?)

etc ....

have fun Smile/happy/getting dizzy