Why have chocks?

[Guest allblack]

OK, I can't beleive I'm asking this, but here goes...I was looking at a picture of a 777 yesterday, and it had chocks under the nosegear to stop it rolling.Hang on! These things have parking brakes. Why the chocks? Is it because the brakes might fail???Another issue of concern is, what if the plane rolled forward three inches? The ground crew couldn't remove the chocks with the weight of a fully-laden 777 resting against them.What am I missing???CheersAllblack

[Guest jaapverduijn]

Greetings Allblack!"(...) These things have parking brakes. Why the chocks? Isit because the brakes might fail??? (...)"That's at least one of the reasons. Another is, that the crew micht have forgottten to engage the brakes. Basically, like everything when it comes to aircarft safety, it's a matter of redundancy. And then more redundancy. And then... well, you get the picture (grin)!"(...) what if the plane rolled forward three inches? The ground crew couldn't remove the chocks with the weight of a fully-laden 777 resting against them (...) Without the chocks a runaway plane wouldn't stop after three inches. The possible difficulty in removing the chocks is a very small price to pay for not having had a runaway aircraft slowly rolling hither and thither..."(...) What am I missing??? (...)"Nothing, really. You made good points and asked good questions. Be well!Jaap Verduijn.

[Guest allblack]

Thanks for that!I have a very good knowledge of things aviation, and felt dopey I didn't know the basics like that....I love the fact that a 150 million dollar aircraft can be kept safe by a $2.00 block of wood.CheersAllblack

[Guest]

Hi All-Tad more info on why the chocks are used.One of the really nifty things on the 757/767 is when you pull the parking brake handle all the little indication tells you is that the handle has been pulled, not that the brakes are actually engaged (ouch). You just don't trust'em till you are absolutly sure....At times, when the plane has had a long taxi to the gate the brakes will heat up and leaving them "engaged" at shut-down will increase the time it takes to cool.Tim757

[Guest Stratus_Fractus]

Also, I believe some aircraft will disengage the brakes after a certain period of time, although I'm not 100% sure on that.

[Guest]

It really is easy to remove the chocks even if the aircraft has rolled on to them. Simply moving the aircraft with the pushback tug. It happens all the time.mark- insert your favorite quote from the movie Airplane -

[Guest P3_Super_Bee]

True, don't know on other aircraft but on P-3's the brake accumulator(holds a preload airpressure and hydaulic fluid) only holds brake pressure for about 24 to 36 hours if aircraft is not powered. Yes brakes will be engaged but will not have pressure behind them. We also don't use parking brakes during cold weather ops. :-outtahttp://www.flightsimnetwork.com/dcforum/Us...43942b48d2b.jpg

[Mats_J 2]

I am almost certain that you are right. I've understood, but I could be wrong, that they disengage the parking brakes when parked for a longer period of time i.e. more than the average turn-around of 40 mins.TGIF