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Full Thrust On Take Off?  
User currently offlineSkyHigh777 From United States of America, joined Aug 2005, 378 posts, RR: 0
Posted (9 years 1 week 12 hours ago) and read 7371 times:

This may seem like an ignorant question, but do pilots always use full thrust on take-offs? I know that once the plane is airborne manytimes the engine power is cut back (at least that I have noticed as a passenger), but is it possible to do a take-off with half or 3/4 throttle?


Prepare for take-off.
14 replies: All unread, jump to last
 
User currently offlineAA61Hvy From United States of America, joined Nov 1999, 13977 posts, RR: 57
Reply 1, posted (9 years 1 week 12 hours ago) and read 7362 times:

If I recall correctly, pilots rarely will do full thrust-unless in extreme situations. As it hurts the engines in the long haul. Most of the time I think the pilots usually go 92% of full thrust.


Go big or go home
User currently offlineAv8rPHX From United States of America, joined Mar 2003, 713 posts, RR: 9
Reply 2, posted (9 years 1 week 12 hours ago) and read 7330 times:

Yes,most times a FLEX/reduced power takeoff setting is used.

User currently offlineS12PPL From , joined Dec 1969, posts, RR:
Reply 3, posted (9 years 1 week 12 hours ago) and read 7328 times:

There was a trip report where someone took BA from I think IAD to LHR? Or maybe LAX. Anyway, in they're in-flight magazine they're "plane of the month" was the 757, and a pilot was quoted saying he only uses 50% thrust for take-offs most of the time.

User currently offlineAirxLiban From Lebanon, joined Oct 2003, 4518 posts, RR: 53
Reply 4, posted (9 years 1 week 12 hours ago) and read 7290 times:

That was me:

http://www.airliners.net/discussions/trip_reports/read.main/68538/



PARIS, FRANCE...THE BEIRUT OF EUROPE.
User currently offlineDIA From United States of America, joined Jan 2001, 3273 posts, RR: 27
Reply 5, posted (9 years 1 week 12 hours ago) and read 7264 times:

Quoting S12PPL (Reply 3):
There was a trip report where someone took BA from I think IAD to LHR? Or maybe LAX. Anyway, in they're in-flight magazine they're "plane of the month" was the 757, and a pilot was quoted saying he only uses 50% thrust for take-offs most of the time.

I would tend to think that is the average case for the 757 (with average weights/pax/fuel/weather/airport altitude/etc. all considered)

Now, for an A343 taking off from DEN to FRA, you bet more than 50% power is applied.

That said, I remember flying through MDW on 722s on ATA. We always started the t/o by sitting at one end of the runway, applying a tremendous amount of power with with brakes applied, then releasing the brakes for a high-powered start...I always thought that these t/os have got to be be full powered (or darn near)...



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User currently offlineIkramerica From United States of America, joined May 2005, 21582 posts, RR: 59
Reply 6, posted (9 years 1 week 12 hours ago) and read 7263 times:

twins should by design only need 50% thrust to take off, otherwise if one engine goes out, 100% thrust of single engine would not be enough and the plane would crash...

Of course, using more than 50% will take you off faster and climb better, so they use more, but there's not reason to come close to 92% on a twin.



Of all the things to worry about... the Wookie has no pants.
User currently offlineLitz From United States of America, joined Dec 2003, 1788 posts, RR: 0
Reply 7, posted (9 years 1 week 12 hours ago) and read 7247 times:
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I do remember reading here that full thrust is used every xx number of takeoffs to certify a "full thrust takeoff". I'm sure people in-the-know can confirm/deny and clarify ...

I've been on a DL 757 during such an event (asked the pilot after landing) ... it's quite a ride !

- litz


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 8, posted (9 years 1 week 12 hours ago) and read 7219 times:

IIRC, the maximum thrust reduction on takeoff is around 25%. That will apply to all aircraft. At my airline, the most we do is 8%, TO-1 52C.

User currently offlineDIA From United States of America, joined Jan 2001, 3273 posts, RR: 27
Reply 9, posted (9 years 1 week 12 hours ago) and read 7216 times:

Quoting Ikramerica (Reply 6):
twins should by design only need 50% thrust to take off, otherwise if one engine goes out, 100% thrust of single engine would not be enough and the plane would crash...

I'm not sure what you mean by this.

Twin-engined a/c (like the 777) are able to t/o with one engine...it is a requirement, just in case of an engine failure too late to abort t/o.



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User currently offlineHiFi From Brazil, joined Apr 2005, 192 posts, RR: 0
Reply 10, posted (9 years 1 week 11 hours ago) and read 7187 times:

It all depends on weight, temperature, airfield altitude and runway length... The power necessary to safely take off is different in each situation. It may be full power on a hot day, taking off an elevated field, with a short runway and a heavy plane...


no commercial potential
User currently offlineSpacecadet From United States of America, joined Sep 2001, 3669 posts, RR: 12
Reply 11, posted (9 years 1 week 11 hours ago) and read 7110 times:

Quoting Ikramerica (Reply 6):
twins should by design only need 50% thrust to take off, otherwise if one engine goes out, 100% thrust of single engine would not be enough and the plane would crash...

You don't need to be able to takeoff from a standing stop on one engine. That's the whole point of having V-ref speeds. All twin-engine airplanes that I know of need both engines running to get off the ground from a standing stop at most airports, at any thrust setting.

If an engine fails after V1 speed is reached, a twin-engine airplane has to be able to get airborne on the remaining engine. But to say a plane travelling (for example) 140 knots with 3,500 feet of runway remaining can take off on one engine is a whole different story than saying a plane stopped at the end of the runway can fully accelerate from zero to takeoff speed on one engine. In some cases it may be possible, depending on the length of the runway, but a) it would never even be attempted, and b) it is not a design requirement under any FAR regulation.

All of this stuff is taken into account when pilots calculate their takeoff reference speeds and corresponding thrust settings. In most cases these days, the FMC will calculate most of this stuff automatically given gross weight, runway length, atmospheric conditions and flap settings, although pilots still need to be able to know how to do it manually. It used to be the flight engineer's job, but that position has been eliminated from most modern cockpits. The FMC will give the pilots the most economical settings for takeoff, although the pilot can always override that or choose a different setting (most FMC's will give pilots a choice between economy or other types of takeoffs).



I'm tired of being a wanna-be league bowler. I wanna be a league bowler!
User currently offlineTom_EDDF From Germany, joined Apr 2000, 452 posts, RR: 0
Reply 12, posted (9 years 1 week 11 hours ago) and read 7084 times:

Quoting DIA (Reply 9):
I'm not sure what you mean by this.

Twin-engined a/c (like the 777) are able to t/o with one engine...it is a requirement, just in case of an engine failure too late to abort t/o.

Yep, but you won't do the whole T/O run on one engine, as this only applies if one engine fails at or past V1, which usually is already pretty close to Vr (rotation) and V2 (safe climbout). Could be 155/157/162kts, for instance.

Quoting S12PPL (Reply 3):
There was a trip report where someone took BA from I think IAD to LHR? Or maybe LAX. Anyway, in they're in-flight magazine they're "plane of the month" was the 757, and a pilot was quoted saying he only uses 50% thrust for take-offs most of the time.

I'd doubt an A330 or 777 at MTOW could accelerate and take off on just 1 engine within any reasonable runway length, and I would also doubt that any major airlines policy would allow anybody to take off with 50% thrust even on a moderately loaded 757, even if it was theoretically possible given the parameters of the aircraft, runway and weather conditions.

Flex take off (I know this is an Airbus term, but applies to similar procedures on other models) is based on an assumed temperature model. Under higher temperature conditions, maximum thrust is reduced in order to keep the engine within its operating limits.

Now, you can assume such temperature that is higher than the actual temperature, which makes the A/T system apply less take off thrust (the maximum possible thrust for the *assumed* temperature, which is *less* than the allowable maximum thrust under the *actual* conditions).

For instance, you could assume 52° C, given runway length, aircraft weight and weather would allow a safe take off under this condition, while your actual temperature is just 25° C.

Higher temperature = lower thrust.

Now, knowing this, you can imagine that (realistically) under no circumstances a temperature could be reached where your maximum allowable thrust would be 50% less than max thrust @ flat rated temperature of the engine or even close to that. Could be 5% less, 8%, 15% but no way 50%.

Cheers
T

[Edited 2005-12-13 20:41:40]

User currently offlineSkyHigh777 From United States of America, joined Aug 2005, 378 posts, RR: 0
Reply 13, posted (9 years 1 week 10 hours ago) and read 6959 times:

Wow I always thought full thrust was used on takeoff, up until I saw a video that was posted here (just about a week ago I believe) showing the virgin atlantic applying full thrust while a car drove behind the engines and flipped over. They said that if the full thrust is applied for too long, it can tear the runway apart...which is what got me thinking on this. Now I really wonder what it feels like to be part of one of those take-offs and hear the engines inside the cabin, must be quite an experience.


Prepare for take-off.
User currently offlineLonghornmaniac From United States of America, joined Jun 2005, 3355 posts, RR: 45
Reply 14, posted (9 years 1 week 9 hours ago) and read 6925 times:

My best experience similar to the ATA 722 at MDW was an AA 757 at SNA. We sat at 19R holding short, and the captain came on explaning the procedure. Taxied out onto the runway, set parking brake, spooled up to full power, released the brakes and went shooting down the runway like a bat outta hell. Really fun. Then, due to noise restrictions right off the end of the runway (some beach, can't remember exactly which one) you have to climb really steep, and then as your doing so, power back to roughly 50 % N1. Man does it make your stomach sink. Then once your out over the ocean you power up again and make your initial turn for wherever. Its a great one to play with on Flight Simulator.

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