NADP Accel Alts

[Airmann]

Consider NADP1,

THR RED: 800'
ACCEL: 3000'

Is there any reason why I, due to operational reasons (e.g. constraints on SID) couldn't increase the ACCEL alt?

I have a hunch that the critical issue for NADP1 is close in noise sensitive areas which calls for a THR reduction early, followed by a decent gain in altitude before acceleration. It seems that perhaps 3000' has been chosen more as what the designers considered a minimum acceptable level rather than being specific. That is that they had to specify an alt and based on their research decided that 3000' was good for the procedure. Would my deciding to accelerate at 4000' or 5000' upset anyone?

[oceancrosser]

In NADP1 departures, we actually reduce thrust at 1500’. I can think of some European airports where they would really like you to accelerate and be on your way. If you have weather reasons to climb slow, just advise and they will accomodate.
Far fewer airports require noise 1 than 2, but I don’t want to mention examples as this is information I look up when needed but don’t store in my head (enough useless information there already)...

[Airmann]

Ok, not sure if there's room for variation but at my company and from the documentation we have NADP 1 has a thrust reduction alt of 800'. I believe NADP A which is more common in Europe is 1500'/3000'.

Regardless I'm more concerned with the Accel height.

[iceman50]

Why not clean up and maintain minimum clean or just above to make any constraints, ATC will expect you to accelerate to ensure traffic spacing. As Oceancrosser said if it is a one off request, ask ATC for clearance, it is not difficult. Otherwise why have procedures we should all do our own thing.

[Tomaski]

Consider NADP1,

THR RED: 800'
ACCEL: 3000'

Is there any reason why I, due to operational reasons (e.g. constraints on SID) couldn't increase the ACCEL alt?

I have a hunch that the critical issue for NADP1 is close in noise sensitive areas which calls for a THR reduction early, followed by a decent gain in altitude before acceleration. It seems that perhaps 3000' has been chosen more as what the designers considered a minimum acceptable level rather than being specific. That is that they had to specify an alt and based on their research decided that 3000' was good for the procedure. Would my deciding to accelerate at 4000' or 5000' upset anyone?

The need for this profile is somewhat aircraft dependent. We used to use this all the time at certain noise sensitive airports but received waivers for newer aircraft with quieter motors. We rarely use this procedure now as our company only routes the newer aircraft through the noise sensitive airports.

[Miles Magister]

The basic premise of a NAPD is to point your noise back at the airfield for as long as possible as you gain height to transit the noise sensitive area which is when you should reduce your thrust and transit the sensitive area quietly.

However you should note that there is no longer any such thing as the NAPD 1/2 in the ICAO PANSOPS Doc, it was removed some time ago and the Doc now states that operators should construct their own noise abatement procedures. I do not have the reference available right but will now but will try and find it later. You should consider things like limiting body angle to 15 Deg as with some modern aircraft, especially business jets, if you depart at full power and V2+10 then the RoC will be very high and level off manoeuvres will require uncomfortably large and rapid control inputs. Also if the pitch attitude is very high it could be difficult to handle at full power in the case of an engine failure on departure, high power and high nose with large yaw are not sensible.

So plan your own NAPD and write it in your Ops manual but think of body angle limits. It could be a good idea to plan all of your departures to reduce power after gear retraction and maintain max body angle of 15 Deg with flap to 1500' or flap retraction alt. This will comply with the previous ICAO NAPDs, easily comply with minimum climb gradients and allow safe effective operations.

MM

Edit: I think you can find reference to the requirement to design your own NAPD in the Jepp Vol 1 Air Traffic procedures noise abatement, but do not quote me as I do not have access to any Jepps any more. If you use the word search function on your EFB you should find the right paragraph easily.

[FlightDetent]

My understanding is the altitude of 3000 in NADP A/B/1/2 was not a constraint by its meaning, but a release. I.e. one may be restricted for noise abatement reasons to follow a certain profile up to 3k, but then she's all yours - up and away.

ATC workload and impact on other traffic is something to consider, sure.

2c, absolutely no reference.

[oceancrosser]

Just to confuse you Airmann, here is an old discussion from 2013: https://www.pprune.org/archive/index.php/t-514590.html