Topic Author
Posts: 57
Joined: Wed Jul 20, 2005 5:24 pm

Emergency Brakes

Mon Dec 18, 2000 3:28 am

I´ve heared that some planes have an emergency braking system.I would kike to konow how it works and which particullar jobs it has.

thank you very much
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RE: Emergency Brakes

Mon Dec 18, 2000 3:33 am

I think they have a pneumatic system consisting of air bottles to help stop the aircraft in an emergency, but don't quote me on that.

RE: Emergency Brakes

Mon Dec 18, 2000 3:56 am

Lears have a Nitris canister if you gear does not come down you can use this for to extend your gear, and you will be able to use what is left after the gear extension to stop the aircraft!
Posts: 1989
Joined: Mon Jul 10, 2000 4:51 am

RE: Emergency Brakes

Mon Dec 18, 2000 4:27 am

The F28 and the dash8 both have emergency brake accumulators. These store hydraulic fluid under pressure, and may be used if the normal brake system fails, which is usually due to fluid loss from a ruptured line elsewhere in the a/c. There is enough in the accumulators to apply the brakes several times, more than enough to stop after landing.
Posts: 138
Joined: Thu Nov 02, 2000 9:31 am

RE: Emergency Brakes

Mon Dec 18, 2000 4:35 am

On take off, one selects RTO (Rejected Take Off) setting on the autobrake system, so that if after 80kts on the take off run, take off is aborted, as soon as the throttles are pulled back, the maximum braking is automatically applied.

Also the spolers can be armed so that they deploy at the same time in an aborted take off - Also spoliers can be armed so that brakes are automatically applied on main bogie wheel touchdown when landing.

The autobrakes also have setting 1,2,3,4, MAX, for automatic braking on landing, higher the setting the greater the braking force. So for instance if one needs to slow down quickly in order to vacate the runway at a certain taxiway - on the approach, or descent a higher autobrake setting would be selected. However one would need to take into consideration when the plane will next be flying, because higher automatic braking makes the brakes VERY hot - and may take an hour or two to cool down to a temperature that would be permissible with which to fly again.

Hope that answers your question.
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Joined: Tue Oct 26, 1999 11:34 am

RE: Emergency Brakes

Mon Dec 18, 2000 6:22 am

The 707 had a pneumatic accumulator that as its operating handle in the cockpit was turned progressivly put nitrogen into the brake lines to apply the brakes. It was a bitch to bleed after the syst had been used.

The 747 brake syst had 3 sources of hyd power, normal brakes Syst 4, secondary Syst 1. These two sytems use the same hoses/lines. Alternate brakes is on Syst 2. This syst utilises seperate lines so if brake hose bursts in syst 4 or 1 there is still a method of applying the brakes.

RE: Emergency Brakes

Mon Dec 18, 2000 6:24 am

I can't speak for smaller planes but transport category aircraft have backup or emergency braking systems.

Generally speaking, one hydraulic system is used for normal braking. Alternate braking using a different hyd system will kick in if the primary (normal) sytem fails. On the B75/76 and A300 this "switch over" happens automatically.

If the normal and alternate sytem fail the crew can activate a button on the Capt's side (B75/76) that uses standpipe protected hydraulic reservoir fluid to activate the reserve brakes (and nose wheel steering on the 767).

If your having a really bad day and all 3 of the above systems fail, all is not lost...yet. You're still left with accumulator pressure which is good enough to get the aircraft stopped.

The A300 works the same way minus the reserve brake option.
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Joined: Sat Nov 11, 2000 8:58 pm

RE: Emergency Brakes

Wed Dec 20, 2000 3:38 pm

Convair used a nitrogen bottle that would both blow the uplock releases and provide nitrogen pressure to the brake system using the normal plumbing. If you had a failed hydraulic line in the brake system, you were screwed. And, yes, it is a cast iron bitch to bleed if the pilot uses it. Have to completely purge and recharge the system. Both were activated by big red knobs on the capts side panel and quite touchy if you applied too much pressure.

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