Chocking A/C
Brakes set when hot... a point worth considering is the gradual weakening of rigid pipes and (especially) flex hoses caused by increased pressure in the lines due to thermal expansion.
Warning Toxic!
Disgusted of Tunbridge
Disgusted of Tunbridge
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Not saying it's right, but we always set and leave park brake (737 and 57), chocks or not. When you get on, park brake is still set. Stays on throughout turnarounds. I assume they are carbon brakes- perhaps not so critical?
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Basically all I'm saying is that I follow the checklist. To that point, I have never seen (or remember to be honest) a checklist that did not have 'release brakes after chocks installed' on said checklist. And that has been a lot of different checklists for a lot, a whole lot, of different aircraft.
As for carbon-brakes, the few aircraft that I flew that those were installed had the same thing on the checklist, however, the only Boeing I flew was the 727.
As for carbon-brakes, the few aircraft that I flew that those were installed had the same thing on the checklist, however, the only Boeing I flew was the 727.
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I think there is some tribal procedures creeping in here. In the airlines I always released the brakes when the chocks were in place. I left the cockpit and went on with my busieness leaving the aircraft in the capable hands of the mechanics. End of story. In my corporate life, operating a B757 and 767, I did sometimes leave the brakes on as the ground crews were usually not very disciplined, or in many cases simply not around. The thought of waking up in the middle of the night, wondering if the airplane had moved for some reason was cause enough to not take any chances. Since no one had access to the flight deck during these layovers, there was not much question about someone moving the aircraft.
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As an engineer of xx years, I do what the pilot asks me to do
If (s)he tells me (s)he is going to release the brakes, I put the chocks in a little tighter on the downhill side. The pilot will probably freak out if the aircraft rolls more than an inch or two (onto loose chocks). Once the aircraft has settled onto the chocks, even if the park brake is reset later, it's basically impossible to get the chocks out again, especially after refuelling. Having said that, it's no sweat off our noses to tow the aircraft a few inches forward to get weight off the chocks to remove them.
We would never rely solely on the park brake for parking an aircraft. The Boeing 744 maintenance manual only specifies 8 hours of braking ...and then only if the (any) of the following tests are done:
Accumulator pressure drop of less than
1) 275psi over 10 minutes
2) 600psi over 30 minutes
3) 800 psi over 1 hour
4) 1000psi over 2 hours
But then there is always Murphy's Law
The park brake relies on the principle of trapped fluid in the brake lines (but there lots of valves through which fluid can leak if seals are faulty).
We leave the park brake set at all times (unless the brakes are hot) and the wheels chocked. Our standard towing/pushing procedure is always to ask the flight deck to release the park brake or to confirm that the park brake has been released.
Rgds.
NSEU
If (s)he tells me (s)he is going to release the brakes, I put the chocks in a little tighter on the downhill side. The pilot will probably freak out if the aircraft rolls more than an inch or two (onto loose chocks). Once the aircraft has settled onto the chocks, even if the park brake is reset later, it's basically impossible to get the chocks out again, especially after refuelling. Having said that, it's no sweat off our noses to tow the aircraft a few inches forward to get weight off the chocks to remove them.
It matters not a jot if the main system hyd pressure drops to zero overnight, the brakes remain ON.
Accumulator pressure drop of less than
1) 275psi over 10 minutes
2) 600psi over 30 minutes
3) 800 psi over 1 hour
4) 1000psi over 2 hours
But then there is always Murphy's Law
The park brake relies on the principle of trapped fluid in the brake lines (but there lots of valves through which fluid can leak if seals are faulty).We leave the park brake set at all times (unless the brakes are hot) and the wheels chocked. Our standard towing/pushing procedure is always to ask the flight deck to release the park brake or to confirm that the park brake has been released.
Rgds.
NSEU
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Brakes left set to Park or Released?
Can't remember for sure about the B707, however the B747 Classic
"Parking Checklist" calls for, in respect to Parking Brake;
"Parking Brake"...................................................... .. Set
(Check that the Parking Brake and Anti-Skid Hyd lights are illuminated.)
"Shutdown Checklist" says;
"Parking Brake"...................................................... ...As Required
(Release Brakes if not required)
That is what Boeing has to say about it, what individual companies do is their call. Personally, if the aircraft is properly chocked with appropriate chocks I can't see any real need for leaving the brakes applied for extended periods.
Thanks Muduckace, as I said, I did not doubt your post. I guess some people just go for an extra bit of "insurance", especially if the area is prone to very high velocity winds. I think the point on increased pressure due thermal expansion raised by stevef is valid.
"Parking Checklist" calls for, in respect to Parking Brake;
"Parking Brake"...................................................... .. Set
(Check that the Parking Brake and Anti-Skid Hyd lights are illuminated.)
"Shutdown Checklist" says;
"Parking Brake"...................................................... ...As Required
(Release Brakes if not required)
That is what Boeing has to say about it, what individual companies do is their call. Personally, if the aircraft is properly chocked with appropriate chocks I can't see any real need for leaving the brakes applied for extended periods.
Thanks Muduckace, as I said, I did not doubt your post. I guess some people just go for an extra bit of "insurance", especially if the area is prone to very high velocity winds. I think the point on increased pressure due thermal expansion raised by stevef is valid.
Had a DC10 once in AKL on the overnight ramp all chocked up. Frontal system went through and DC10 was found 30 degrees different heading from where we left it!!!
Center gear on the 10 was never chocked due to the rake angle of the gear. When the weight came on with fuel loading the gear would walk backwards.
Tight chocking of through flight aircraft not good as the weight change as the aircraft was loaded can spread the foot print of the wheel/tyre and jam the chocks.
Our company rule is 20 knots or more of wind the brakes must be on or all wheels must be chocked is required due hot brakes.
Center gear on the 10 was never chocked due to the rake angle of the gear. When the weight came on with fuel loading the gear would walk backwards.
Tight chocking of through flight aircraft not good as the weight change as the aircraft was loaded can spread the foot print of the wheel/tyre and jam the chocks.
Our company rule is 20 knots or more of wind the brakes must be on or all wheels must be chocked is required due hot brakes.
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Leaving parking brake on in wet/slippery conditions might be a good idea:
http://www.onnettomuustutkinta.fi/uploads/jf35ou.pdf
http://www.onnettomuustutkinta.fi/uploads/jf35ou.pdf
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There was an entertaining article on chocks in "Douglas Service" about thirty years ago. Sure wish I could find it, or another like it. Wiki has very little, and is asking for more.
GB
GB
Rejected takeoff??? simple... after the jet comes to a stop... tiller full offset... brakes released to prevent wheel lockup
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As an engineer of xx years, I do what the pilot asks me to do
Big airlines have safety depts full of people making rules.
I do what the airline wants.
BA always leaves the brakes ON, plus 6 chocks.
MH always releases the brakes after chocks ON. We have to be careful where we put them as they get trapped. You don't chock the nosewheels if you have a TBL, or you will have problems.
Boeings brake pressure declines with time and the brakes are not effective after 8 hours.
Airbus have a completely different park brake design and keep their pressure for ages. Overnight I see no decay at all.
Aaah yes, chocks, my favourite subject.
Chocks go in tight both sides. Unless engine running at high power.
Brakes released, the leeward IE uphill chock is pulled back an inch or two to allow for expansion during fueling etc.
If the downhill chock is stuck, good, that's what it's there for. At departure time the tug will shift the aircraft as necessary.
Different on an A330 as the main gear is angled and so you get creep as the weight goes off and on.
There is a MM procedure about chocking the nose and leaving the main chocks loose, or vice-versa, can't remember.
One Middle Eastern operator I could name demands that no ground equipment or airbridge/steps etc go near the aircraft until chocks have been confirmed in and brakes have been released. A thumbs up is required from the headset man who meets the aircraft on arrival.
Chocks go in tight both sides. Unless engine running at high power.
Brakes released, the leeward IE uphill chock is pulled back an inch or two to allow for expansion during fueling etc.
If the downhill chock is stuck, good, that's what it's there for. At departure time the tug will shift the aircraft as necessary.
Different on an A330 as the main gear is angled and so you get creep as the weight goes off and on.
There is a MM procedure about chocking the nose and leaving the main chocks loose, or vice-versa, can't remember.
One Middle Eastern operator I could name demands that no ground equipment or airbridge/steps etc go near the aircraft until chocks have been confirmed in and brakes have been released. A thumbs up is required from the headset man who meets the aircraft on arrival.
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Speaking of the A330, does anyone know why the 330 tends to jolt during refuelling and loading/unloading ? It's so sudden that the wheels and wings will shake ? I've never seen this on another a/c.
It's better to confirm brakes off and let the a/c settle on the chocks before letting any equipment dock with the a/c. I've seen a case where the jetway hit the AOA sensor and the door when the brakes were released after the jetbridge was docked.
It's better to confirm brakes off and let the a/c settle on the chocks before letting any equipment dock with the a/c. I've seen a case where the jetway hit the AOA sensor and the door when the brakes were released after the jetbridge was docked.
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Just a few discussion points-
Chocks are not a big deal, I have pushed right over them on an unlit remote parking area and did not feel a thing with a little momentum.
A stuck chock is not a big deal unless you are trying to capture a TLD and the chocks on the NLG are stuck.
Why does SOP for bogies have us all chocking the tires (tyres) fore and aft, if we just threw 2 chocks between the mains the aircraft would have to jump 2 chocks instead of 1 and they would be easier to handle.
Chocks are not a big deal, I have pushed right over them on an unlit remote parking area and did not feel a thing with a little momentum.
A stuck chock is not a big deal unless you are trying to capture a TLD and the chocks on the NLG are stuck.
Why does SOP for bogies have us all chocking the tires (tyres) fore and aft, if we just threw 2 chocks between the mains the aircraft would have to jump 2 chocks instead of 1 and they would be easier to handle.
