Auto thrust on the A330

[cornwallis]

Have any of you experienced poor athr response on approach in an A330? A few times i have seen the athr not increase thrust when the speed has decreased below the approach bug and even reduced to idle thrust in the very late stages of an approach and then not increase as speed decays. This of course leads to the inevitable firm landing!I would welcome any comments of similiar experiences.

[Jet A1]

The A321 also suffers from the same problem and has led to high pitch angles and resultant tail strikes on landing.

I counter this by intervening with a selected speed target from the box and this seems to get the thrust to become more accurate and responsive.

The slow responses with A/THR I have found to be when using Managed Speed.

[Fbwdude]

I have been flying A 320/319 for almost 5
years now and only once I had to move the thr levers out of climb detent, fwd as stated on fcom 3 to correct speed.
I believe auto thrust is much better(reliable) than auto throttle .Response time is pretty good.
Best regards to you all.

[cornwallis]

The problem i am referring to is on the A330-200 with trents.The athr often reduces thrust at inappropriate times,i have seen it happen below 100ft ra back to idle and then it leaves you do your best to avoid the inevitable hard landing.You cannot notch below 100ft ra as you get toga.has anybody else experienced this?

[Angels40]

Cornwallis

I agree with you 100%. I've flown the 330 with all three engine types, ( CF-6, PW,and trent). Of the 3 types, I have found the GE CF-6 to be the better engine in terms of Autothrust responsiveness! The bloody things start up in around 30 secs flat from master swith on.

Nothing worse than when landing in turbulent conditions, to find your speed dropping below the Approch Speed Target and the engines doing nothing about it. Fair enough, the engines are big, and take time to respond. I heard engineers talking about the computer software which controls the autothrust, mentioning that it depends on which model of computer controling the autothrust that determines the engine responsiveness?!?!?!?!?!?!

Some guys add 2 or 3 knots onto the MCDU VApp speed above 700' to compensate for this. I actually prefer flying with the autothrust OFF. It is an aeroplane after all, and I'll make it do what I want it to do!

The 340 with the CFM-56's is OK. The smaller engines react well to the autothrust command, and Approach speed is maintained in all conditions I've been in.


So yeh, I know what you're on about.


:)

[oryxbollocks]

I agree with Angels. I have not flown the P&W, however I agree the Trent is slow to respond compared with the GE and the CFM on the 340.

I never bother with additives to Vapp or relying on 'notching'. I just fly an approach in gusty conditions with the auto thrust off.

GB

[SMOC]

I remember hearing some time ago that autothrust on the Roller 330s were hunting excesively to maintain speed, so the fix was to modify the software as Angels40 has mentioned, and now it's too slack.

[Dan Winterland]

320s with V2500s - no problems. 321s with V2500s - same problems as metioned before. Gets slow, takes ages to get back to Vapp if at all. Answer, make Vapp VLF+8. Works every time.

[A330ETOPS]

I agree. GE CF-6's are the better engine in terms of Autothrust responsiveness, compared to the Trent 772b's

[petitfromage]

In my experience:

In 'soft' ATHR mode the IAS can vary +/- 4kts without the ATHR being overly concerned. At Vapp - 4kts it will give you a sudden increase in thrust, but before that it gives you very little and in small increments. (Im assuming this is a software issue?)

Personally, I find 'bugging up' the Vapp by 5kts, tends to result in a long flare (esp at lower weights around 155T).
The A333 definitely prefers to land heavy (> 175T)

The Trent772 is a large engine and even at 'high idle' (used during approach) it does take its time to spool up. I do find that getting the aircraft stabilised at Vapp by 1000ft AAL really helps with the ATHR stability.

Below 100ft RA, if you apply anypower yourself (I assume this is what you refer to as notching?) you will get THR CLB (not TOGA), even if you you replace the levers into the CLB detent. That is because moving the thrust levers below 100ft RA, disconnects the ATHR.

Lastly & I concur with others here, if the wind is greater than 10kts across, or gusting at all, I personally use manual thrust and fly 2-3kts above Vapp (I dont adjust Vapp in the MCDU, the mini-GS takes care of that)
I reduce the IAS to Vapp depending on the conditions (to stop a long flare), most often at about 100ft.

IMHO:
a. ensure youre stabilised at Vapp at 1000ft AAL
b. use manual thrust if the wind is unstable
c. dont bug up the 'VApp' if using manual thrust (its self defeating) just fly a few nts above and let mini-GS do the hard work.
d. enter the flare at Vapp.

All the above only my humble opinion; Ive not flown the GE engines.

[A-3TWENTY]

Hi Fellows,

I`m flying the 320 and use to land at LPMA(Funchal, Madeira Is) known by extreme turbulent approaches.

It`s recommended by the company the use of flaps 3 in order to decrease drag and give you more thrust available and the use of managed speed.

Actually in turbulent conditions I really use flaps 3 BUt A/THR OFF and VLS+5.

Of corse it makes your landing run a bit longer but if you touch down where you want you just go a little bit harder on brakes.

The other problem I see in Airbuses that I have never felt in other acft`s is the low responde of flight controls.In extreme conditions they are really slow.
I have never flown other acft where I so often need to take the controls to te stop (extreme conditions).
Normal law at the 320 gives you a roll rate of 25º/s
Maarcel Dassault is now lunching a new Falcon with fly-by-wire and its roll rate is 40º/s.
Seems much more reasonable...

:ok:

[SMOC]

Don't shoot the messenger.

I was told by a training Capt. but found it nowhere in the manuals that the sidestick has an input to the autothrust.

Apparently if you're aggresive with your sidestick inputs the autothrust becomes aggressive and likewise if you are gentle with sidestick = gentle autothrust.

another 2 cents

Not on the Bus anymore but like many, enjoyed/preferred manual thrust.

[A-3TWENTY]

If you have a gust that put you 15 degrees bank in a glance you have no other choice.
And if you use ailerons the A/THr has nothing to do with that.
And third.....I have never seen or heard anything like that .

Ask to the Captain where is it written.

[cornwallis]

I have seen in my company's guidance for overweight landings that at high gross weight getting the speed into VLS will lead to a firm landing even if the pilot puts a flare input in.Does anybody have any data on athr logic for the 330 or a chart showing howdrag increases as the speed deteriorates into VLS?

[javelin]

2000 hours on 330's - mainly Trent, sometimes P & W (yeuch !).

Never taken the autothrust out, our stats have shown that several of the tailstrikes recently, in particular the 321 also were flown in manual thrust, practise in the sim, it wasn't designed to be flown in manual thrust unless in bad turbulence.

It does hunt, it sometimes dips into VLS, so what, it ain't going to stall or come anywhere near it. VLS is a reference speed with lots of protection left in normal operations.

Compare a manually flown approach to an autopilot flown approach - you will notice that with the autopilot in, the thrust doesn't hunt. That tells me that we are all guilty of PIPO and end up blaming the autothrust. There is a lot of inertia, the engines are large.

Finally, I wouldn't be adding a knot here or a knot there to Vapp, when it all goes horribly wrong, the lawyers will come a hunting :ok:

[petitfromage]

I dont discount your experience at all....but youve obviously not flown into Hong Kong in a typhoon then?
Bugging up Vapp & using manual thrust is essential (an i.a.w FCOM/Airbus procedures, as you say, for significant turbulence)

I do agree that too many Airbus pilots get a real bee in their bonnet over VLS. It is not a critical speed and gives you significant margin above Vs....but dont for a second believe the AOA protections will always save you from a stall.
They cannot and will not with significant windshear. (Not trying to be condescending, so please dont take it the wrong way...its always good to hear others experiences)

Quick question though: you've never used manual thrust on approach ever? Not even in training? I assume you have in the sim? What about base training? Havent you ever done a single engine, manual thrust, approach/landing in the aircraft (not sim) for training?
All these are requirements in my airline.

[popay]

Hi guys, I read with interest the discussion and felt like to add my 2 cents to that. I quite don't remember what it used to be like on A 321, but on A 330 with AP on its seems to be stable, once you take the AP off and don't do any input, i have the impression that the A/C tends to pitch up. Thats the moment, I think, the problem starts cause the guys start to chase the director, which cause on the other hand the auto thrust to go the opposite way and the problem only aggravates. I try to keep constant pitch 2,5 Flaps Full for the pedants and see where it takes me initially adjusting than with small inputs so the inertia of the aircraft doesn't play a bad game with me. That's of course only in stable conditions. For the same reason mentioned above its better to take it off while in gusts. However I think it doesn't make any difference whether with or without auto thrust the pilot should be able to fly it correctly.
Cheers.:8

[javelin]

petitfromage,

I have used manual thrust many times, both during training, in the sim - it is recommended for all single engine work, and on line.

After recent incidents and after accepting that the aeroplane is designed to be flown with the autothrust in, I do not fly on the line with manual thrust because we don't do it frequently enough as routine and the times we practise in the sim are just that - in the sim.

I actively encourage F/O's to hand fly the aeroplane as all types we fly (multi fleet flying - 320 V2500 and CFM, 321 CFM, 330-200 Trent, 330-300 Trent) are great to handle. I no longer allow manual thrust unless conditions dictate it's use from the FCOM's.

If any MD pilots are watching, what did you do because our old MD's I believe used autothrust all the time unlike the Boeing philosophy of AP out, AT out.

[cornwallis]

Some interesting replies to my original question.The athr does not seem as sharp as it was when the aircraft was originally delivered.Now i would describe its speed control as poor.Does anybody know anybody in airbus i could discuss this with?