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convair880mfan
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At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Mon Aug 02, 2021 8:47 pm

I have heard 1000 feet agl and 1500 ft agl from pilots. A former TWA Boeing 707 pilot told me that in his time 800 feet agl was when they reduced thrust and leveled off to build speed for flap retraction.

A now retired 747 captain told me that on that aircraft, one needed to fly level for a time to build speed for flap retraction and that at heavy gross weights it was rare to be able to climb initially and retract flaps at the same time.

Are there many commercial airliners that can retract flaps in a climb or is it related to weight and other conditions?. I have no idea.

Thanks to one and all for your responses.
 
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BWIAirport
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Mon Aug 02, 2021 8:56 pm

I've only flown on simulators (PMDG products, etc) but in my experience it's around where you mentioned, certainly below 2000ft. As you alluded to, there are variables to this such as aircraft weight and noise restrictions at the departure airport. Someone correct me if I'm wrong but the cost index or climb/cruise profile may contribute as well.
 
Nicoeddf
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Mon Aug 02, 2021 9:16 pm

convair880mfan wrote:
I have heard 1000 feet agl and 1500 ft agl from pilots. A former TWA Boeing 707 pilot told me that in his time 800 feet agl was when they reduced thrust and leveled off to build speed for flap retraction.

A now retired 747 captain told me that on that aircraft, one needed to fly level for a time to build speed for flap retraction and that at heavy gross weights it was rare to be able to climb initially and retract flaps at the same time.

Are there many commercial airliners that can retract flaps in a climb or is it related to weight and other conditions?. I have no idea.

Thanks to one and all for your responses.


If not obstacle limited, it is 1000ft AGL for NADP2 and 3000ft AGL for NADP1, respectively.

Most of the times though, there is barely a real world change in thrust, due to take off derate.
 
convair880mfan
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Posts: 219
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Mon Aug 02, 2021 9:18 pm

NADP1? NAPD2? Sorry I don't know the meaning of these?
 
Okcflyer
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Mon Aug 02, 2021 9:38 pm

On many aircraft, there can be a thrust INCREASE transitioning from derated takeoff thrust to climb thrust (usually also derated)
 
ChrisKen
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Mon Aug 02, 2021 9:39 pm

convair880mfan wrote:
NADP1? NAPD2? Sorry I don't know the meaning of these?

Noise Abatement (Departure) Procedures - 1 Areas close to airport. 2 Further away ~25kms
 
GalaxyFlyer
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Mon Aug 02, 2021 10:02 pm

Quads tend to have less excess thrust on take-off than twins, so twins often can reduce to climb thrust and maintain a heathy climb rate. Remember they both have to fly with ONE engine inoperative, so the twin has lots of excess on a AEO take-off.
 
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tb727
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Tue Aug 03, 2021 1:06 am

Okcflyer wrote:
On many aircraft, there can be a thrust INCREASE transitioning from derated takeoff thrust to climb thrust (usually also derated)


We had FE's giving us numbers on the 727 when light that would show an addition of thrust at 1000', at which point we said you don't reduce takeoff thrust below your climb thrust.

It's funny on the Airbus I call it a climb thrust takeoff when we are pretty light, especially on the 319's. I've seen some FO's will try to be all smooth bringing the thrust lever from FLX/MCT to CLB slowly as to have a smooth thrust change when there isn't even a difference.
 
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Starlionblue
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Tue Aug 03, 2021 1:16 am

In our case, the thrust reduction and acceleration altitudes are typically both 1500ft AAL.

Nose down. Reduce thrust to the CLB detent. Accelerate and clean up. Maintain green dot (max L/D ratio until 3000ft. Basically NADP2.

Some airports have different procedures, which require variation of thrust reduction and/or acceleration altitude.

convair880mfan wrote:
NADP1? NAPD2? Sorry I don't know the meaning of these?


NADP1
Image

NADP2
Image
 
Woodreau
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Tue Aug 03, 2021 3:29 am

When you run your performance numbers for the airport and specific runway, the takeoff performance report will tell you what your thrust reduction and AEO/TEO (all engines operating / two engines) and OEI (one engine inoperative) acceleration altitudes are for that one specific takeoff you are doing.

Normally, our airline does thrust reduction and acceleration at 1000ft AFE.

However at one airport, thrust reduction is at 1000ft AFE, and acceleration is at 3000ft AFE. At another airport, thrust reduction is at 800ft AFE, and acceleration is at 3000ft AFE.
 
CanukinUSA
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Tue Aug 03, 2021 3:42 am

There are a lot of variables that may affect where a pilot reduces to climb thrust: (Sorry if this adds to your confusion over thrust reduction altitude)
1) How long the engines may be operated at takeoff thrust. All Engines are certified for 5 minutes at takeoff thrust. Many Engines now are approved to use takeoff thrust for 10 minutes in the event of an engine failure to improve climb performance. Since Engine life is typically affected by the time spent at high thrust levels, most airlines will try to reduce thrust during takeoff and the reduce to climb power as soon as they can legally and safely. It depends on the aircraft weight, runway length, elevation. temperature, air pressure and if there are obstacles present on the departure path. Larger airlines have Aircraft Performance Engineers that will do takeoff calculations and specify a Thrust reduction altitude to optimize Aircraft Performance and Engine Life. For smaller airlines and Business Jets because they do not have aircraft performance engineers and the flight crew typically do the takeoff performance calculations, they use procedures for reducing thrust in accordance with the FAA Aircraft Certification Standards, so they typically use 1500 feet above airfield elevation as that is what the FAA has the takeoff and climb out profile up to in the Aircraft Certification Regulations for Transport Category Aircraft.
2) Noise restrictions at many airports as demonstrated in the post above may require thrust reduction at particular locations to keep the noise level down over noise sensitive areas. The Noise Abatement procedures shown in the previous post were developed by International Civil Aviation Organization (ICAO) to standardize Noise Abatement procedures worldwide so that a million different procedures do not get developed in different countries, but some countries may decide to have procedures that differ from the ICAO standard ones.
 
Max Q
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Tue Aug 03, 2021 4:56 am

Disregarding certain airports special departure procedures there are two types of noise abatement departures :


ICAO ‘A’ - Take off thrust is maintained to 1500’ AGL then reduced to climb thrust, and speed maintained, acceleration (with flap retraction) to clean maneuvering speed then cleared speed starts at 3000’ AGL, this procedure is more commonly used outside the US



ICAO ‘B’ - Take off thrust maintained to 1000’ AGL then reduce to climb power, accelerate to clean maneuvering (with flap retraction) maintain clean maneuvering to 3000’ AGL then accelerate to 250 KIAS or cleared speed
 
e38
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Re: At what height above field elevation is takeoff thrust reduced [increased] to climb thrust

Tue Aug 03, 2021 1:54 pm

convair880mfan, if it helps to put the two noise abatement departure procedures (NADP) in context, in the U.S., NADP1 (ICAO A) is commonly referred to as the “Close-in Community Noise Abatement Departure Procedure” while NADP2 (ICAO B) is called “Distant Community Noise Abatement Departure Procedure.”

Normally, published flight operations directives dictate to the crew which procedure to use when departing an airport. Occasionally it may be different for different runways at the same airport.

e38

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