Chocking A/C

[H Ferguson]

hello,

Is there any risk of damage to a/c landing gear, wheels, by chocking the wheels too soon after landing ,in particular Boeing a/c ?

[Spooky 2]

I have never seen or heard of any chocking restrictions on any airliner other than the center gear on the MD11 and DC10-30.

[Feather #3]

A/c are parked with the brakes on [unless hot!]

Smart engineers leave the chocks about 2 inches [50mm] from the tyres so they don't get jammed!

G'day ;)

[con-pilot]

A/c are parked with the brakes on [unless hot!]


Sorry, but most strongly disagree, respectfully.

In the 42 some years that I have flown I only set the parking brake until chocks are inserted under the gear. Then the brakes are released.

Smart engineers leave the chocks about 2 inches [50mm] from the tyres so they don't get jammed!

Now on this statement I agree. Even then the aircraft will roll onto the chocks causing problems. There have been occasions that a tug had to be used to push the aircraft back to enable the chocks to be moved.

Once on a 727 we had to have the main tires changed because an old tubular metal chock was used and the chock failed cutting into the tires.

Now, to answer the question posed by this thread. No.

[muduckace]

Sorry, but most strongly disagree, respectfully.

In the 42 some years that I have flown I only set the parking brake until chocks are inserted under the gear. Then the brakes are released.

Operating the largest fleet of B727's in the world we leave our brakes set...Allways, we chock the mains as well and the nose if weather is expected and a pushback is not connected.

[MarkerInbound]

"Is there any risk of damage to a/c landing gear, wheels, by chocking the wheels too soon after landing?"

Ah, yes, if you chock the gear before you get to the ramp, that's not good.

[Feather #3]

Indeed with 40 years at the same company operating Boeing equipment, the same as muduckace above.

G'day ;)

[con-pilot]

Well, as I flew 727s for over ten years and have over 7,000 hours as Captain in the aircraft, just what did you do when the 727s were parked over night and the parking brake pressure bled down?

We never, repeat never, left the parking brake on after being chocked. If for no other reason than brake disk warping.

Do you leave the amp selector switch in the Bat Volt position overnight as well?

You show me a 727 parked on a sloping ramp with only the parking brake on and no chocks left overnight and I'll show you a 727 at the bottom of the sloping ramp.

[SNS3Guppy]

I've never left parking brakes set. Chock, then release.

Setting chocks back helps keep them from getting trapped. Setting them at an angle to the outboard side of the tire helps break them lose if they do get trapped.

[Old Fella]

In the fifty and some years that I have been involved in aviation, as a ground engineer, flight engineer and pilot I cannot ever recall a normal requirement to leave the brakes applied after having the chocks in place. That applies to all the aircraft I have been associated with from light aircraft to B747's. I am not questioning the posts of those such as mudackace or Feather #3, just a little surprised that their company uses such practice.

[Bullethead]

Interesting variations on procedure.

The company I fly for leaves the park brake set after shutdown and during turn arounds and the only time I've ever seen otherwise would be for an instance of hot brakes.

Regards,
BH.

[autoflight]

During 42 years I always released brakes after chock insertion, including during 7000 hours on B727. Even on A320 with brake fans, followed same procedure.
There is a story of a RAAF C130A parked on a slope at Kainantu, PNG about 45 years ago. During unloading of a vehicle, army troops borrowed 2 downhill chocks to pevent vehicle runaway. Aircraft rolled but captain was fast enough to chase aircraft, jumped aboard and applied brakes, saving a write-off.
So on a slope, depending on brake temp and company policy, belt and braces would seem appropriate.

[airsupport]

This is really weird. :uhoh:

In my 45 years in the Industry, Engineer NOT Pilot, and at several different Airlines, we have always chocked aircraft on arrival (yes after stopping) then release the brakes.

IF it is just a turnround then that is it normally, however IF it is on an extended turnround and definitely if overnight, once the brakes are cooled off brakes are parked and chocks left in. :ok:

That includes ALL the aircraft I have ever been involved with, including B727s.

[rubik101]

con pilot, Once the parking brake is set, the pressurised hydraulic fluid is trapped in the system. It matters not a jot if the main system hyd pressure drops to zero overnight, the brakes remain ON. 38 years of Boeing ops in EU and we always set the brakes and left them set unless hot.

And if the ammeter flattens the battery overnight, you have a poor battery.

[Welle]

I do agree with the above said:

Chocks on - Brakes Off

At my last employer we the procedure only to leave the breaks on during very windy conditions (eg +35 kts..), but this is off course a company procedure and might be related to the aircraft type (crj)

now, here in the world of business aviation: NEVER leave the park-brake on, when you leave your aircraft, ´cause it is quite common that your aircraft is moved to a different parking apron after you left...
we even carry our own set of chocks on the plane because you never know where you end up in the end of the day.

my 2 cents
welle

[compressor stall]

The other reason to keep the chocks back an inch or two from the tyres where possible is that the a/c is usually much heavier when departing than arriving - the tyres before departure bulge out trapping the chocks in place.

[One Outsider]

Leaving the parking brake set slows the cooling of the heat sink, which in turn transfers more heat to the hydraulic fluid, which in turn cases it to become acidic, which in turn causes filter elements and seal to break down more rapidly, which in turn........

[captjns]

After 30 years flying Boeings... not much has changed except for carbon brakes.

After landing and parked, brakes set... chocks in place... brakes released.

Before engine start, brakes set, tug connected.

If the bird was overnighting... brakes set before shutting it down for the night. I rarely saw brake pressure equal to accumulator pressure. Its a good system with check valves to prevent back flow of fluid or pressure to the normal hydraulic system.

Rejected takeoff??? simple... after the jet comes to a stop... tiller full offset... brakes released to prevent wheel lockup... start the APU and shut down the motors. Whiel the aircraft is being towed to the stand... think about the acivities for the evening... once on stand... chocks in place before tug is disconnected so the brakes don't have to be set.

Go th the hotel, and have a great night.:ok:

[leewan]

Accumulator pressure will actually drop over time weakening the parking brake force. Unless the hyd demand pumps are on. There was once when a bunch of guys from my place who were towing an a/c to a remote stand couldn't find any chocks and decided to set the parking brake only and then go for lunch. Coming back after lunch, the airport authorities surrounded the a/c as the a/c actually rolled back blocking an active taxiway. Thank God there were no damages.

[muduckace]

Parking brake left set.
In the fifty and some years that I have been involved in aviation, as a ground engineer, flight engineer and pilot I cannot ever recall a normal requirement to leave the brakes applied after having the chocks in place. That applies to all the aircraft I have been associated with from light aircraft to B747's. I am not questioning the posts of those such as mudackace or Feather #3, just a little surprised that their company uses such practice.

It is odd but true. The only operator I have worked for that left the brakes set hot. We have no brake issues. I believe it is policy because of the 727's lack of hydrolock on the nosewheel steering as an additional measure to prevent the aircraft from spinning around in strong winds (they will jump chocks).

On another note it has been common practice in the past on all aircraft I have ever worked with to leave the brakes set during a layover (after they have cooled down). We do not practice this on other fleet types at my current employer.

[stevef]

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.

[Rainboe]

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?

[con-pilot]

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.

[Spooky 2]

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.:}

[NSEU]

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.

It matters not a jot if the main system hyd pressure drops to zero overnight, the brakes remain ON.

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

[Old Fella]

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.

[c100driver]

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.

[jjj2]

Leaving parking brake on in wet/slippery conditions might be a good idea:

http://www.onnettomuustutkinta.fi/uploads/jf35ou.pdf

[Graybeard]

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

[Centaurus]

Rejected takeoff??? simple... after the jet comes to a stop... tiller full offset... brakes released to prevent wheel lockup

Now that's what I call lateral thinking. A good simulator discussion point?

[Swedish Steve]

As an engineer of xx years, I do what the pilot asks me to do :ok:

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.

[TURIN]

Aaah yes, chocks, my favourite subject.:O:O




Chocks go in tight both sides. Unless engine running at high power.:O:{

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.

[leewan]

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.

[muduckace]

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.