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Joined: Mon Jul 16, 2001 2:14 pm

Park Brake Lever

Mon Dec 10, 2001 7:36 am

Hi All

What would happen if say, a commercial airliner (747/777 etc) were to touch down with the park brake ENGAGED (I'm not talking 'bout the autobrakes).

I cant say that I've noticed any reference to the "park brake DISENGEDED" item on the before landing checklist.

Come to think of it has anyone else see that 747 (from memory) touching down with an "OFF CENTRE" nosewheel????? (something else thats not on the before landing checklist??)

I'll bet THAT scared the beegeebies out of the pilots....

Kind Regards
Dave Hollingsworth
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RE: Park Brake Lever

Mon Dec 10, 2001 9:50 am

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Pacifism only works if EVERYBODY practices it
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RE: Park Brake Lever

Mon Dec 10, 2001 10:24 am

Nothin' says love like using Airborne  Smile/happy/getting dizzy
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RE: Park Brake Lever

Mon Dec 10, 2001 12:04 pm

Parking brakes are part of the take-off warning system and on some aircraft part of the landing or config warning system. Thus, if you attempt to take-off (you gotta take-off before you land) with the brakes set, the airplane screams at you and you don't move. If for some reason you set the brakes in the air, the airplane will scream at you when you configure for landing. What will happen if you ignore the airplane? I believe you will blow all your tires.

As for the "off center nose wheel". The nose gear on all commercial aircraft is of a self-centering design which rarely if ever fails. There is no check-list item because on most aircraft there is no indication or real control.

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RE: Park Brake Lever

Mon Dec 10, 2001 3:44 pm

Air2gxs is correct on the self centering nosewheel. As the Nose strut extends at t/o, there are cams inside the strut that force it to the centered position. The only way it can fail is a true parts failure, or the torque links somehow becoming disconnected. On some aircraft if the nosewhell is not centered, the gear will not retract.
I've not given too much thought to the parking brake issue, DC-9's & DC-10's will honk if not configured for t/o. (flaps.leading edge device, elevator trim) but don't remember about the brakes. We usually just pull the t/o warn breaker during a runup so we don't have to drop flaps or listen the the horn. I've done runups on both a/c and not been able to stay in one place due to weather conditions. DC-10 sliding on ice is a real trip!
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RE: Park Brake Lever

Mon Dec 10, 2001 7:46 pm

I have seen the result of a BAC 1-11 landing with the
Park Brake set - 4 flat spotted wheel hubs, about 6 inches ground off the hubs.

As for self centreing nose wheels. We once jacked a World Airways DC10 with the torque links disconnected and as the leg extended to nose wheels turned through 90 Degs ! The strut centreing cam had some how been fitted 90 degrees out. The only thing holding the leg straight was the steering jacks.
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RE: Park Brake Lever - AIR2GXS

Mon Dec 10, 2001 10:50 pm

Can u tell me which aircraft give you an aural warning if brakes are set in the air??
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RE: Park Brake Lever

Tue Dec 11, 2001 12:35 am

The MD80 and DC9 are interesting in the fact there is no nose gear centering cams.
When the nose gear lifts off the ground, the ground shift mechanism (cable driven) holds the *steering tiller* in the centered position thus pointing the nose wheels straight ahead.
With the nose gear off the ground (full oleo extend) and hydraulics turned off, the nose gear can be physically turned left and right by grabbing the nose tires and twisting it.
You're only as good as your last departure.
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RE: Park Brake Lever

Tue Dec 11, 2001 2:05 am

Most airliner antiskid systems incorporate a "touchdown protection" mode. This function (generically speaking), while airborne with the gear down, "dumps" all brake pressure either if the pedals are depressed or parking brake set prior to touchdown. Initial wheel spinup would occur, in other words, the brakes shouldn't be "locked" on touchdown.

After touchdown wheel spinup, when the touchdown protection mode deactivates, the brakes would probably lock (with the parking brake set scenario) because setting the parking brake deactivates the antiskid system.
You're only as good as your last departure.
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RE: Park Brake Lever

Tue Dec 11, 2001 3:19 pm


I am only making the assumption that those aircraft that have config (take-off) warning for the parking brake, i.e. B757 & B767 would also trigger for landing warning. But. I have never verified it.

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RE: Park Brake Lever

Wed Dec 12, 2001 8:12 am

The Dash 8 has the park brake tied into the takeoff warning horn. For landing configuration, the GPWS is used, and there is no park brake input. There is a caution light which comes on when the brake is set, but nothing stops you from landing that way. On the Dash, the park brake is also the emergency brake, and so has no antiskid protection.

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