A330 Pitch Up on Touchdown
 

To the A330 gurus:

I have noticed a few times the nose pitching up after touchdown. I looked closely at a recent landing. Commenced flare at around 35 feet, closed thrust levers, good touchdown rear bogies then a deflare and idle reverse, into full reverse, nose then suddenly pitched up a few degrees requiring more nose down control.. I don't believe that that I am applying any back pressure on stick. Could this pitch up be caused by gnd spoiler deployment. Probably just need more deflare. Any idea's.

I believe you answered your own question, bare in mind that I am not on the A330 fleet, this is exactly what happens when using the same landing techniques in the smaller bus, try a pitch up about 2 degrees at 35-40 and then de-rotate slowly.

Flame suit on.

Had it happen once each on the L1011 and the A330. Both times had a lot of reverse on. My sense of it is, spoilers will affect the tendency for the nose to pitch up but will not, in themselves, cause it to do so under normal operational circumstances.

First thing I would do is call your flight data analysis team, preferably an association gatekeeper and ask to look at your flight because you're concerned about technique. Properly read data and some aeronautical knowledge should be able to help determine what the cause was.

I know you say "after deflare", but still ask, was the nosewheel completely on the ground when reverse was selected? Was the aircraft light, (around 160T or less)? Was the CG slightly more aft than normal? When did the nosewheel begin to lift, (what N1/EPR/Airspeed)? Was there a quartering tailwind - I've seen this as a factor in some tailstrikes esp if the speed is on or slightly below Vapp just before touchdown.

Your data analysis program will be able to tell you all this. If you don't have a data analysis program on the airplane, ask your airline why not. Then, try to recall all the above to learn why it's happening - it's not common for the airplane. Full reverse down to a full stop is permitted in the AOM if required in an emergency but one still must guard against pitch up.

The AOM doesn't specifically state that slight nose-down stick is to be held but a very slight amount won't be hard on the nosewheel structure and may prevent the tendency - ask your checking/training staff first though...this is an anonymous forum!

PJ2

PJ2;

Agree with what you wrote. What needs to be kept in mind is that nose-down stick takes some load off the main wheels and thus reduces brake effectiveness. Just don't overdo it, particularly on wet/slippery runways. EDIT: If you're using full reverse and not using brakes, then of course it won't matter. But is it generally good practice to delay braking until you need it? Perhaps early use of brakes will pitch the airplane nose-down naturally without having to apply nose-down stick? Does autobrakes play a role in this?

regards,
HN39

Did you have your MLG on ground when that happened or just the rear bogies?

Hello HN39;

Agree with you...for reasons stated, gently on the nose-down elevator during the landing rollout is absolutely required for a number of reasons. In fact, any forward-stick would be more to avoid any potential slight nose-up input...and as MrWooby indicates, he was cognizant of this and recalled that no nose-up stick had been applied, so he was thinking of this.
In the case of the A330, use of the autobrake is an SOP. Usually the setting used is the lowest, (LOW), vice higher settings (MED) which would be used for contaminated runways or when landing distance is a factor. The "MAX" setting is used only at takeoff, for the rejected takeoff. Although the setting will work on landing, it is not recommended.

Re delaying use of brakes; - on LOW, the autobrakes are applied one second after the ground spoiler deploy signal; at MED the brakes are applied when the signal is sent. The nosedown tendency upon autobrake application can be benign or significant depending upon those factors mentioned. I have had experience with both.

At touchdown and de-rotation, the AOM specifies caution if the brakes are applied while the pitch is still high (flare attitude), meaning that the pilot should be ready with as much as full back-stick to prevent the nosewheel from slamming down on the runway. Again, weight, CG, wind and pilot technique are all components in such an event. There is no AOM statement regarding a slightly-forward stick after touchdown and one certainly does NOT want to apply down-stick before the nosewheel is on the ground - the AOM specifies that back-pressure on the stick is "relaxed" and the nosewheel descends "naturally" in flare law.

Sidebar comment: Increasingly throughout airline operations, the use of IDLE Reverse and reliance on brakes is becoming normal. This isn't the thread to debate that decision, but the AOM states that reverse can be used up to the maximum any time the pilot deems necessary, right down to full stop.

shortfuel;
Neither reverse, nor ground spoilers (and therefore autobrake), are available before the main-gear bogies are on the ground. So pitch-up could not occur as a result of high reverse thrust at this point in the landing.

The "unlocking" (hydraulic leveling) of the bogie can result in a very hard landing or something less than satisfactory and it is beyond the direct control of the pilot, resulting in much discussion and different touchdown techniques..."trying to beat the forward wheels to the ground" has resulted in some pretty hard nosewheel touchdowns, the alternative being really firm "second touchdown" when the bogies unlock. They are designed to work this way to increase the distance between the tail and the runway surface - on the takeoff rotation, the bogies also rotate to lift the aircraft about 4ft or so. They are hydraulically leveled during the retraction sequence.

(For those interested in why this is so, I was informed that the space available in the inner-wing/body structure for the main gear oleo and bogie was not large enough to provide for the length required to provide good clearance for the tail during rotation/landing flare. Rotating the bogie for height resolved the problem for both the A340 and A330).

PJ2

Thanks for the input guys, will have to look very closely at the next few landings. Shorfuel, I believe whole MLG was in gnd contact, not just rear bogie. Funny, things used to be so easy on the Boeing, flare, fly the nose on.

Hello PJ2;

Thanks for your explanation. It is more complex than I thought. Perhaps my perception is somewhat biased by the way 'max. performance' landings must be done for certification: maximum braking on a dry runway without using reverse thrust. I guess the reversers on your airplane are very effective.

regards,
HN39

Probably spot on, this was an issue for the DC-10 and resulted in hull losses with the MD-11.