A320 Thr reduction/Acc alt

[squawkident.]

Hi Guys,

Ive recently started working for an A320 operator. The company requires us in the departure profile to have a thr reduction alt of 1000aal and acc alt of 3000aal.

With my previous company both were 1000aal and so im still getting used to the differences within the climb profile.

A few days ago, I was on the SID which had a published stop alt of 6000. Passing about 2000agl, we were cleared direct to FL80.
Consequently I set 8000, but due to alt constraint I then pulled open climb.
This consequently took us from SRS direct to open climb at 1000 lower than as per the profile.

What do you suggest I do as an alternative? I could remove the constraint in the SID or select V/S?
Perhaps in a busy TMA VS would be appropriate but what about in a more isolated airfield??

How significant is accelerating at 3000 agl as opposed to accelerating earlier? Am I perhaps putting too much thought into this or is it not that significant?
My understanding is this is just a noise abatement procedure?

Thanks

SI.

[Dan Winterland]

Pulling the ALT knob and going into Open Climb cancels your acceleration altitude constraint, which maybe for either terrain clearance or for noise. If you want to keep it, you need to control the speed manually. Either by pulling the speed knob and adjusting the speed to your previous SRS speed, or if you can anticipate this happening in the planning phase, put a suitable manual speed in the climb phase.

In either case, you lose SRS protection, so another way is to dial up the new altitude/FL and go into open climb by pulling it once you have accelerated. If you haven't already gone into ALT* and there is no alt constraint, then it will accept it as a new climb altititude/FL and climb accordingly. If there is, you can get always the other pilot to cancel the constraint.

I wouldn't personally use VS as it won't maintain a speed reference.

[Gary Lager]

a) that profile is usually just noise abatement, if it were obstacle clearance then the THR RED altitude is modified, not the ACCEL alt in my experience. If you are worried about terrain then you can always select speed (it doesn't have the same protections as SRS but by this time you're 2000'+ agl and going up, so not a huge worry). So it's not the end of the world if you pull OP CLB by too early.

b) why not pre-select the cleared FL (in this case FL80) and delay pulling OP CLB until the FMA changes to CLB mode. I know you said you had an alt constraint but there's no reason you can't delay 'pulling the knob' until 3000' - you're not going to bust your level and the FMA change can act as your cue to select OP CLB if you're worried about forgetting.

c) whatever you decide, tell your colleague! It's important they know what you're doing, if you deviate in any way from 'standard' i.e. from what they would expect.

[CaptainProp]

Squawk,

Accelerating at 1000' or 3000' is not significant as far as aircraft handling goes (disregarding airport specific obstacle requirements). In the situation you described I would PULL selected speed, and then PULL open Climb. Once you reach 3000' select 250 kt, accelerate and clean up. If necessary due to busy airspace PULL selected speed, PULL VS and adjust vertical speed. On reaching 3000' select 250 kt, accelerate and clean up.

Now, why is you new operator using 3000'? Because it is in PANS OPS DOC 8168. There are two noise abatement procedures described here. NAPD 1 and NAPD 2 and you can find them described in "Appendix to Chapter 3" in Doc 8168, Volume 1. They both, with some difference in wording, call for "At 900 m (3 000 ft) above aerodrome elevation, accelerate to en-route climb speed." This is why your new ops procedures call for the 3000' acceleration. The procedure as such, in PANS OPS, is not new. However, I believe that last year the rules changed somewhat and if I am correct you are now to follow this procedure on every departure unless local procedures call for a different climb/acceleration schedule. I have not been able to find a reference to this but maybe some else can provide this?

If you keep this in mind before every departure then you can change the acceleration altitude on the PERF page before takeoff and you will not have the "problem" you described above. When given clearance to higher alt/lvl just delete the constraint.

Good luck!

CP