Center gear braking

[stilton]

On aircraft such as the DC10-30 and A340
with a center gear bogie assuming they
are equipped with brakes this configuration
prompts a question

Obviously pressing the left brake activated
braking on the left wheels and the same on
the right

So how are the brakes activated on the
center gear?

I suspect any time either set of brakes are
activated ?

[DaveReidUK]

Originally Posted by stilton

On aircraft such as the DC10-30 and A340 with a center gear bogie assuming they are equipped with brakes

The DC-10/MD-11 centre gear is certainly braked. On the A340, the -200/-300 centre gear isn't, but I believe it is on the -500/-600.

Obviously pressing the left brake activated braking on the left wheels and the same on the right

So how are the brakes activated on the center gear?

I suspect any time either set of brakes are activated ?

You may be right, but I suspect that could make taxying difficult. It would make more sense for the centre wheel brake only to operate when both brake pedals are pressed simultaneously.

Can anyone confirm?

[Meikleour]

Further to the above - on the A340-600 the left brake pedal activates the forward centre gear brake and the right pedal the aft centre gear brake. Odd I know but it is french designed!

[Uplinker]

The arrangement you mention gives half braking on the centre gear in the event of a full left or full right braking action turn, and full braking on the centre main in the event of full symmetrical braking, which seems reasonable. I suppose they could have split the centre main brakes left and right instead of front and rear. Perhaps there was some other consideration, leading them to keep the centre braking forces symmetrical around the gear leg?

Splitting the centre main brakes in this way makes for a very simple hydraulic arrangement. Anything else would require extra valves and possibly electronics to achieve the same purpose.

[Meikleour]

I have always thought it was so as to avoid the need for a torque link on the body gear.

[wiedehopf]

you always need a torque link.

but with breaking just left or right tires the torque link would weigh a ton

[DaveReidUK]

As well as being pretty ineffective in terms of providing a turning moment.

[fantom]

This is a troll.

Trolls cannot spell 'centre'.

[Uplinker]

Not necessarily; s/he might be American? They spell centre ‘center’.

[Discorde]

Hi Meikleour

All oleo type landing gear legs need a torque link (or splines) to maintain wheel alignment during compression or extension of the leg.

Braking the left or right wheels separately on the A340 centre gear would probably induce unacceptably high torsional stresses on the leg.