A340 Touch Down .

[VP TAA]

What causes the the bone jarring thump after initial smooth touch down on the A 340 ? What can be done to prevent it ?

[AhhhVC813]

The rotation of the main bogies towards the front axle after touch down of the rear wheels, can cause a thump as the spoilers deploy, and the higher the pitch attitude at flare the worse it is. However the main second thump occurs as the centre gear touches down after the spoilers deploy, and the aircrafts weight is dumped onto the oleos. The centre gear lands after the mains as it is not stressed for landing. Landings tend to be smoother on the A330, which does not have the centre gear, (or a 340 with the centre gear retracted).
The 340-500/600 is better in this respect as the centre gear is landing stressed and lands at the same time as the main bogies.

[canuck slf]

AhhhVC813

I did not realize that a 340 was capable of landing with the centre gear retracted. What would be the reason for doing this and is it normal practice?

Thanks in advance.

[Golden Parrot]

Similar thing happens on the 330. Best way to avoid it is to flare for the rear axle, then smoothly derotate until the front axle is on the ground and THEN apply reverse. For extra points, a slight tug on the sidestick just as the nosewheel comes down will avoid waking up the first class pax. If reverse is applied as the rear axle touches down the aircraft will literally fall a meter or so onto the front axle as the combined effect of reversers and ground spoilers kill the lift. This technique assumes you are at the right place with the right speed on touchdown and a long and clean runway. If any of these conditions are not met I just fly the thing into the runway and go full reverse asap.

[AhhhVC813]

canuck slf.

If, (unlikely), the gear is lowered by gravity extension on the 200/300 series, the centre gear does not extend. It can also be locked in the retracted position if there is a fault, this being done by ground maintenance action, (rather than something that can be done from the flightdeck). No, it is not normal practice, as it reduces the MTOW substantially.

[VP TAA]

AHHHVC813 and Golden Parrot thanks for the response . I certainly will give the technique a try next time .
VP TAA