Company selected acceleration height
Thread Starter
Joined: Aug 2013
Posts: 1
Likes: 0
From: Latvia
Company selected acceleration height
Hello everyone,
The question of this thread is: what is the reason of setting company minimum acceleration altitude higher than 400ft?
As I see it, acceleration altitude must be highest of:
- minimum regulatory altitude (400ft AGL)
- acceleration altitude limited by obstacles
- noise abatement procedure required minimum
From the above, if at the given AD/RWY there is effective noise abatement procedure,or there are obstacles which required minimum acceleration altitude to be higher than 400ft AGL, then That minimum shall be used.
But, if to consider AD/RWY with no obstacles, no effective noise abatement procedure - what could be the reason to restrict acceleration at 400ft AGL?
I am looking at this question from fuel efficiency perspective.
As:
- the sooner a/c retracts flaps (less drag),
- the sooner it accelerates to final climb speed (higher speed)
- the less fuel will be burned on the flight.
The tendency described above can be seen, e.g. by comparing BCOP outputs. The difference between accelerating at 400ft and 1000ft for B737NG at average weight could be like 5 kg less fuel burn total.
It is not much for a jet a/c single flight, but fleet-wise yearly savings for the company could be significant.
So the question is, what could make companies to select minimum acceleration altitudes 800/1000/1500ft?
Thank you a lot!
Any comments, critics, opinions are highly acceptable.
The question of this thread is: what is the reason of setting company minimum acceleration altitude higher than 400ft?
As I see it, acceleration altitude must be highest of:
- minimum regulatory altitude (400ft AGL)
- acceleration altitude limited by obstacles
- noise abatement procedure required minimum
From the above, if at the given AD/RWY there is effective noise abatement procedure,or there are obstacles which required minimum acceleration altitude to be higher than 400ft AGL, then That minimum shall be used.
But, if to consider AD/RWY with no obstacles, no effective noise abatement procedure - what could be the reason to restrict acceleration at 400ft AGL?
I am looking at this question from fuel efficiency perspective.
As:
- the sooner a/c retracts flaps (less drag),
- the sooner it accelerates to final climb speed (higher speed)
- the less fuel will be burned on the flight.
The tendency described above can be seen, e.g. by comparing BCOP outputs. The difference between accelerating at 400ft and 1000ft for B737NG at average weight could be like 5 kg less fuel burn total.
It is not much for a jet a/c single flight, but fleet-wise yearly savings for the company could be significant.
So the question is, what could make companies to select minimum acceleration altitudes 800/1000/1500ft?
Thank you a lot!
Any comments, critics, opinions are highly acceptable.
Joined: Apr 2009
Posts: 495
Likes: 4
From: UK
Striking a balance between safety and saving some fuel can be one reason for adjusting your acceleration heights. Some airports are extremely busy with rapid fire Atc instructions and frequency changes once airborne. Having someone heads down adjusting thrust levers, doing radios, changing frequencies, making fcu selections if the other pilot is hand flying all at 400ft above the deck is asking for trouble. That's what our flight ops department thinks anyway.
