flaps30
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Full Power Takeoffs

Mon May 25, 2009 6:15 am

I have been hearing the term "full power takeoffs" alot lately. Forgive me for sounding naive, but I always assumed my aircraft was departing under full power. Why would they takeoff on anything but full power? Whats the benefit of taking off under reduced power aside from the obvious fuel burn. It seems to me there are less options in an emergency at a reduced power setting.
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wilco737
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RE: Full Power Takeoffs

Mon May 25, 2009 6:25 am



Quoting Flaps30 (Thread starter):
but I always assumed my aircraft was departing under full power.

I did nearly 2000 flights and I would say about 20 of them were full power, the rest was done with reduced thrust, so it happens most of the time.

Quoting Flaps30 (Thread starter):
Why would they takeoff on anything but full power?

If you do that the engine isn't that stressed  Smile So it can be operated longer.

Quoting Flaps30 (Thread starter):
It seems to me there are less options in an emergency at a reduced power setting.

It is still perfectly safe as you calculate with this thrust reduction and you have the same options. And if you want to, you can always advance the thrust levers and get full power anyway. So this is always an option as well.

wilco737
 
vikkyvik
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RE: Full Power Takeoffs

Mon May 25, 2009 6:41 am



Quoting Flaps30 (Thread starter):
I have been hearing the term "full power takeoffs" alot lately. Forgive me for sounding naive, but I always assumed my aircraft was departing under full power. Why would they takeoff on anything but full power? Whats the benefit of taking off under reduced power aside from the obvious fuel burn. It seems to me there are less options in an emergency at a reduced power setting.

As Wilco stated, engine wear is a factor. In addition, it reduces noise, and burns less fuel as you stated.

Most large airports have long runways - the runway length isn't usually the limiting factor in a takeoff. So if you have the extra room, it makes sense to use a bit more of it and save some money.

There are situations in which a full-power takeoff is required - for instance, a short runway. I've also heard that some airlines require full-power takeoffs every so-many takeoffs, to basically ensure the engines can still work. I don't know if that's an FAA requirement, though.
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wilco737
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RE: Full Power Takeoffs

Mon May 25, 2009 6:57 am



Quoting Vikkyvik (Reply 2):
burns less fuel as you stated.

There are people still of different opinions. You need longer to reach acceleration height, so you have longer take off power until you set climb thrust. And the climb thrust is reduced as well, so you reach your cruising level later as well which cost you more fuel and you climb slower.  Wink

Quoting Vikkyvik (Reply 2):
I don't know if that's an FAA requirement, though.

We don't do full power take off until it is necessary for performance or MEL reasons.

wilco737
 
vikkyvik
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RE: Full Power Takeoffs

Mon May 25, 2009 7:28 am



Quoting WILCO737 (Reply 3):
There are people still of different opinions. You need longer to reach acceleration height, so you have longer take off power until you set climb thrust. And the climb thrust is reduced as well, so you reach your cruising level later as well which cost you more fuel and you climb slower.

Ah, that's a good point. Although couldn't your climb thrust setting still be the same as for a full-power takeoff? In which case, you're only "losing" the fuel you'd use from takeoff to throttle-back to climb. Or is the climb thrust setting always also reduced?
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wilco737
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RE: Full Power Takeoffs

Mon May 25, 2009 7:35 am



Quoting Vikkyvik (Reply 4):
Ah, that's a good point. Although couldn't your climb thrust setting still be the same as for a full-power takeoff? In which case, you're only "losing" the fuel you'd use from takeoff to throttle-back to climb. Or is the climb thrust setting always also reduced?

Sure you can do that, but then it could happen that the "full power" climb thrust his higher than the reduced take off thrust. That means reaching acceleration (thrust reduction) height that the engine N1 increases.  Smile

wilco737
 
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HAWK21M
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RE: Full Power Takeoffs

Mon May 25, 2009 10:20 am

Why use full power,when you can get airborne with the needed EPR/N1 required considering the OAT/Length of runway/load.
Saving on the Engine life is important.

Some Airports have noise restrictions too,which nessistate lower thrust settings.

regds
MEL.
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Dufo
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RE: Full Power Takeoffs

Mon May 25, 2009 8:17 pm

On Saab 340 we are required to perform full power takeoff once per 100 takeoffs (if not otherwise required by limiting factors).

Most of the time we use 92-100% of maximum 108% torque - saves a lot of money for overhaul as we operate under on-condition maintanance plan.
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Mir
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RE: Full Power Takeoffs

Tue May 26, 2009 2:20 pm



Quoting Flaps30 (Thread starter):
Whats the benefit of taking off under reduced power aside from the obvious fuel burn.

There you go. Whether it actually saves fuel or not is debatable, but what it does save is engine wear, and it cuts down on noise. Both of those are desirable outcomes.

Quoting Flaps30 (Thread starter):
It seems to me there are less options in an emergency at a reduced power setting.

You can always push the throttles forward if something happens.

Quoting Vikkyvik (Reply 2):
There are situations in which a full-power takeoff is required - for instance, a short runway.

Depending on the airplane, a wet runway also requires a full power takeoff.

-Mir
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OffshoreAir
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RE: Full Power Takeoffs

Tue May 26, 2009 3:25 pm

There are all kinds of "max" thrust settings, and true max thrust is not used as common as people would think.

If I remember correctly, when I took a turbine transition class that used a King Air as the turbine template, the King Air could operate, in an emergency situation, at max available thrust for a certain period of time. This is if an engine lost power on take-off or at a low altitude, the pilot could firewall the throttle which would send the ITT temps skyrocketing and the engine would need to be overhauled before it could be used again.

Another Professor of mine who use to be a 777 captain at United told us they only used full-power take-offs if the runway had a certain amount of rain water or snow on it. He told us a story where he did it in FRA and said they upset a lot of locals near the airport with the giant 777 engine noise  laughing 
OffshoreAir
 
PGNCS
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RE: Full Power Takeoffs

Tue May 26, 2009 6:24 pm



Quoting Vikkyvik (Reply 4):
Although couldn't your climb thrust setting still be the same as for a full-power takeoff?

It depends on the aircraft, but yes it sure could.

Quoting Vikkyvik (Reply 4):
Or is the climb thrust setting always also reduced?

Again, it depends on the aircraft. Even some aircraft with reduced thrust climb available don't use it at some operators for a variety of reasons.

Quoting WILCO737 (Reply 5):
Sure you can do that, but then it could happen that the "full power" climb thrust his higher than the reduced take off thrust. That means reaching acceleration (thrust reduction) height that the engine N1 increases.

This is uncommon, but not unheard of (MD-90 for example.)

Quoting Mir (Reply 8):
Quoting Flaps30 (Thread starter):
It seems to me there are less options in an emergency at a reduced power setting.


You can always push the throttles forward if something happens.

Mir is right. All reduced thrust takeoffs meet performance requirements without requiring additional thrust. There are times when reduced thrust may not be advisable (unstable weather, for instance,) but the ability to advance the throttles always exists (although EEC/FADEC controls may limit the power produced to prevent overboosts or overspeeds unlike earlier hydromechanical fuel controls.)
 
flaps30
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RE: Full Power Takeoffs

Tue May 26, 2009 7:05 pm

Quoting HAWK21M (Reply 6):
Some Airports have noise restrictions too,which nessistate lower thrust settings.

OK, but what about SNA (John Wayne airport Orange County,CA). That seems to be an exception because the noise restrictions require departing aircraft to make a very steep initial climb. Can that be done on a lower thrust takeoff or is SNA one of the exceptions that require a full power takeoff?

[Edited 2009-05-26 12:17:08]
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wilco737
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RE: Full Power Takeoffs

Tue May 26, 2009 7:12 pm



Quoting PGNCS (Reply 10):
This is uncommon, but not unheard of (MD-90 for example.)

Can happen on the 737 if you use max deration for take off and select full CLB thrust, then the N1 increases. usually the 737 uses CLB - 2 then and the N1 reduces slightly, but if you select CLB, then the N1 increases. Uncommen - yes, but possible.

wilco737
 
PGNCS
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RE: Full Power Takeoffs

Tue May 26, 2009 8:08 pm



Quoting WILCO737 (Reply 12):
Quoting PGNCS (Reply 10):
This is uncommon, but not unheard of (MD-90 for example.)

Can happen on the 737 if you use max deration for take off and select full CLB thrust, then the N1 increases. usually the 737 uses CLB - 2 then and the N1 reduces slightly, but if you select CLB, then the N1 increases. Uncommen - yes, but possible.

Thanks for the info. I only flew classic 737's and it was a while back. You are talking about the 737NG, right? I have seen this most frequently on the MD-90 (this is an interesting difference from the MD-80; I wonder about the 717...) but it's possible on others as well. Thanks for your insight!  Smile
 
wilco737
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RE: Full Power Takeoffs

Tue May 26, 2009 8:09 pm



Quoting PGNCS (Reply 13):
Thanks for the info. I only flew classic 737's and it was a while back. You are talking about the 737NG, right? I have

Nope, I was talking about classic. Maybe it is a different software setup then. I used to fly -300/-500s and they had that feature. To be honest, I cannot really remember on the NG, but I guess it is available there as well.

wilco737
 
PGNCS
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RE: Full Power Takeoffs

Tue May 26, 2009 9:12 pm



Quoting WILCO737 (Reply 14):
Quoting PGNCS (Reply 13):
Thanks for the info. I only flew classic 737's and it was a while back. You are talking about the 737NG, right? I have

Nope, I was talking about classic. Maybe it is a different software setup then. I used to fly -300/-500s and they had that feature. To be honest, I cannot really remember on the NG, but I guess it is available there as well.

Thanks...I don't know much about the NG; I mostly flew the 732, but we also had 733 in fleet. It's just been too long!  Smile
 
Mir
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RE: Full Power Takeoffs

Tue May 26, 2009 9:42 pm



Quoting Flaps30 (Reply 11):
OK, but what about SNA (John Wayne airport Orange County,CA). That seems to be an exception because the noise restrictions require departing aircraft to make a very steep initial climb. Can that be done on a lower thrust takeoff or is SNA one of the exceptions that require a full power takeoff?

Yes, the SNA noise abatement profile requires a full power takeoff (which is still not the max available power of the engines, since, as has been mentioned, the engines will be damaged if you firewall them), followed by a dramatic thrust reduction soon after takeoff (at 1,000 feet if memory serves).

Quoting PGNCS (Reply 13):
I have seen this most frequently on the MD-90 (this is an interesting difference from the MD-80; I wonder about the 717...) but it's possible on others as well.

It can happen on the CRJ-200 as well.

-Mir
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PhilSquares
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RE: Full Power Takeoffs

Tue May 26, 2009 10:20 pm



Quoting Mir (Reply 16):
which is still not the max available power of the engines, since, as has been mentioned, the engines will be damaged if you firewall them),

If you have a EEC/FADEC engine you can certainly firewall them since you have protection on overboost, overspeed and overtemp.
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longhauler
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RE: Full Power Takeoffs

Wed May 27, 2009 12:19 am

"Firewalling" the engine/engines in the event of a failure is something one has to be careful of. VMC is calculated at the reduced thrust, if you had the misfortune to lose an engine right at Vr, and you thought it prudent to firewall the remaining engine, you might not be able to control the aircraft at that low speed/high thrust condition.

It takes discipline (and restraint) but you have to trust that the calculations were made using the reduced thrust, and all things equal, it should carry you to safety one on engine.

That being said though, in non-thrust loss occurrences like say wind-shear or terrain warnings, firewalling the engine is always available.
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Mir
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RE: Full Power Takeoffs

Wed May 27, 2009 2:00 am



Quoting PhilSquares (Reply 17):
If you have a EEC/FADEC engine you can certainly firewall them since you have protection on overboost, overspeed and overtemp.

Very true. My point was that even on a full power takeoff, the engines are not developing all the power that they physically could be.

-Mir
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brons2
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RE: Full Power Takeoffs

Wed May 27, 2009 6:23 am

I've ridden on a NW A330-300 that had a pretty mild takeoff, but upon the time the flight would usually be throttling back, the engines actually increased and the buzzsaw was very pronounced for the next couple of minutes. So it would seem that the climb thrust was set above the takeoff thrust, however, it's impossible to tell for sure from the peanut gallery.
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LU9092
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RE: Full Power Takeoffs

Fri May 29, 2009 3:04 am

Back in December I rode on a UA A319 LGA to ORD. The weather was quite rainy that day in New York, and upon lining up on 31, the pilots held the plane with the brakes until the engines had reached (or, just about reached) takeoff thrust. I hadn't experienced that technique since sometime in the late 80's on a UA 727-200 departing LAS in late July. Would the pilots hold the plane with the brakes if they were not using "max thrust"? I do know I've never felt an A319 accelerate quite like this one did.  Cool
 
TK739ER
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RE: Full Power Takeoffs

Fri May 29, 2009 3:36 am



Quoting Mir (Reply 8):
a wet runway also requires a full power takeoff.



Quoting OffshoreAir (Reply 9):
they only used full-power take-offs if the runway had a certain amount of rain water or snow on it.

What is the reason for this? Maybe to cut the rolling time and get airborne asap because the runway surface is unstable??
 
Alias1024
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RE: Full Power Takeoffs

Fri May 29, 2009 3:58 am



Quoting Mir (Reply 16):
Quoting PGNCS (Reply 13):
I have seen this most frequently on the MD-90 (this is an interesting difference from the MD-80; I wonder about the 717...) but it's possible on others as well.

It can happen on the CRJ-200 as well.

Very true. In fact I'd say the majority of reduced thrust takeoffs I've done in the CRJ have resulted in an N1 increase. Depending on weight, runway length and atmospheric conditions, it isn't uncommon to have an N1 increase of 2-4% when climb thrust is set.
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vikkyvik
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RE: Full Power Takeoffs

Fri May 29, 2009 4:24 am



Quoting TK739ER (Reply 22):
What is the reason for this? Maybe to cut the rolling time and get airborne asap because the runway surface is unstable??

In a sense, yes. I would guess the major reason is that in the event of a rejected takeoff, your stopping distance will be considerably longer on a contaminated runway.

More distance required for stopping = less distance available for accelerating for takeoff = more power needed (for a given weight and configuration).
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OffshoreAir
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RE: Full Power Takeoffs

Fri May 29, 2009 7:23 am



Quoting TK739ER (Reply 22):
What is the reason for this? Maybe to cut the rolling time and get airborne asap because the runway surface is unstable??

Surface conditions of a paved runway that include snow, water, ice, etc also induce a certain amount of extra drag on the aircraft landing gear as well, making take-off roll's longer.
OffshoreAir
 
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longhauler
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RE: Full Power Takeoffs

Fri May 29, 2009 3:18 pm



Quoting LU9092 (Reply 21):
Back in December I rode on a UA A319 LGA to ORD. The weather was quite rainy that day in New York, and upon lining up on 31, the pilots held the plane with the brakes until the engines had reached (or, just about reached) takeoff thrust.

Quite often at LGA, ATC will instruct you to "keep the thrust up, be ready for an immediate takeoff", as they are co-ordinating landings on the intersecting runway. Sometimes, depending on how high your thrust is when the takeoff clearance is received, it can be very dramatic.
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stratosphere
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RE: Full Power Takeoffs

Fri May 29, 2009 8:08 pm



Quoting Mir (Reply 16):
full power takeoff (which is still not the max available power of the engines, since, as has been mentioned, the engines will be damaged if you firewall them

Thats true. Last year we had 2 727's that had windshear events in the same week one in RNO and one in GJT I believe and both required all 3 engines replaced due to the engines being firewalled.
 
LU9092
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RE: Full Power Takeoffs

Sat May 30, 2009 5:49 am



Quoting LongHauler (Reply 26):
Quite often at LGA, ATC will instruct you to "keep the thrust up, be ready for an immediate takeoff", as they are co-ordinating landings on the intersecting runway. Sometimes, depending on how high your thrust is when the takeoff clearance is received, it can be very dramatic.

It really is impressive to watch ops at LGA on a busy day. Clearly, every second counts!

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