Maximum Acceleration Altitude

[lion-g]

Hi Guys,

I just came across this term. My guess is this is due to the time limit available on the engines for TOGA power. Any other performance related explanation ?

Thanks for your help.

Cheers,
lion-g

[B-HKD]

Not necessarily limited by TOGA time as thrust reduction can be at a different altitude. Of course depending on aircraft type etc.

On the 744 for example:

Valid accel. height figures are: 400'agl to 9999'agl

Valid thrust reduction height firgures: 400'agl to 9999'agl or at Flaps 5.

this being specific tot he 744.

[Capt Groper]

This term is usually used for an ENG INOP situation, where if not already at MCT then one should level off to accelerate, clean up to Flap Zero (clean) and be able to achieve the final climb (Green DOT for Airbus speak) where MCT can be selected all within the TOGA time limitation (usually 10 mins).
In general terms it is approx 1000' above the minimum acceleration ALT unless operating from hight altitude airports.
:ok:

[Mansfield]

The maximum acceleration height, from the Boeing standpoint, is precisely what you had surmised. Takeoff thrust must be maintained through the third segment (acceleration and clean-up). The third segment must be completed before the time limit on takeoff thrust expires. This will necessarily limit the height at which the third segment can be started.

That said, I've never seen this limit come into play.

[FE Hoppy]

Same on the Embraer E-jets except the software ends at 3000AGL!!

[dalan]

Hi PPRune Community,
as this is my first post, just a short introduction. I'm a just retired performance engineer having worked for more than 3 decades for a major airline.
The selection of the proper acceleration altitude has accompanied me all times in my job.
According to the regulations (FAR 25.111) an airplane must satisfy a certain minimum climb gradient at every point along the takeoff flight path starting at 35 ft until end of third segment. The requirement reads 1.2% for a twin, 1.5% for a three engine aircraft and 1.7% for a quad. There is no word about the required thrust setting during the second and third segment. So from the regulations perspective the maximum acceleration altitude is not limited by the thrust time limit rather by the climb gradient capability (for acceleration the equivalent climb gradient is used).
Most takeoff programs however have adopted the thrust time limit to calculate the maximum acceleration altitude for computation simplification reasons. One exemption is the Boeing program (e.g. B737-300) allowing a so called "extended second segment" where the acceleration and flap retraction is performed with Maximum Continuous Thrust.
Hope this helps clarifying this subject.

Regards dalan