Airbus Approach Profile Question

[Mr_MD11]

Greetings All Professional Pilots

The aircraft involved in this question is a A330, Once on approach descending through approx 900 ft we were Vref +4 Kts which was still acceptable but the problem was that because of this over speed the engines on the auto throttle did not spool up and thus the N1 remained below the stable approach criteria.

1st Question: What actions can be done in this situation to bring the aircraft back into profile considering speed brake use is not allowed below 1000ft and we were already at flaps 4?

2nd Question: The captain on this flight seeing this situation order the flaps to be retracted to 3 from 4, is there any logical reason why he would do this?

All responses will be greatly appreciated I am still searching through the manuals on how the auto throttle works in this situation and any suggestions on what section this info maybe in will also be much appreciated.

Cheers Tommy

[MestiAdaSaudara]

Hey MrMD,

If you are Vref+4kts, in nil wind conditions you would actually be Vaap-1kt. Bit hard to eye-ball 1kt but assuming you can, I guess that would be a tad bit on the unstabilized side.

If you wanted to bring the N1 up what you can do is just bring the thrust levers back just out of the CLB detent whilst disengaging the A/T. This will give a boost of power but just remember that the A/T is disengaged and if left at a high power setting, will cause your IAS to increase quite rapidly.

If you bring the thrust levers out of the CLB detent up closer to FLEX/MCT, the boost of power will be too much and the chances of high IAS is greater.

MAS

[Carnage Matey!]

I can only speak from experience on the A320 but in our company we had such a problem achieving the N1/EPR criteria at 1000ft that it was eventually changed to 500ft.

If it is critical that you have at least a certain N1 at a certain altitude then the quickest way to bring the power up on the engines is to go to selected speed and wind a few extra knots no. Once you've passed the gate simply return to managed speed, the power will tail off but should return by 500ft. That technique is realy no different to flying an approach with a strong gusty headwind.

The Captains actions of commanding flap 3 seems a bit bizarre to me. On an A320 it would change the managed speed target from Vapp to F speed which would command a power increase, but if your intention is to meet stabilised approach criteria then why destabilise the approach significantly by retracting Flap Full below 1000ft, especially when you are so close to Vls?

By far the best option for a quick response is to disconnect the A/THR and manually set the power, but we're banned fom doing that now in our outfit.:suspect:

[Mr_MD11]

Firstly Thanks for the reply.

From reading the posts it seems that the only way to get the N1 to spool up to the correct figure is to accept a increase in speed, which is what we expected.

Question 1: If we happen to be in a situation with flaps 4 and Vapp +10kts and the N1 value is still below the acceptable value is there anything that can be done to save the approach?

Question 2: Not considering stable approach criteria for this case, Will the extra 10kts be enough to compensate for the inital slowed response of the engines in a go-around due to the lower N1 Value?

Cheers Tommy

[Flap 5]

Changing flap setting below your minimum height for a stabilised approach should only be done in the event of a go around. The captains action of changing from flap full (not 4 - by the way) was very suspect.

Vref + 4kts is a little slow. If the autothrust has the engines spooled down then Mesti's method works. Too many people forget that even the A330 can be flown like a basic aircraft. The A330 is harder to slow down compared to the A320. However if you are slow (due to an unstable approach or windshear) you have to be very careful because the increase in thrust is large, although slightly delayed, when the autothrust is cancelled and the thrust levers are still in a high thrust lever angle.