User avatar
HAWK21M
Topic Author
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

Chock Spacing Between Wheel

Mon Jan 21, 2013 9:17 am

For reasons known to prevent the chocks biting into the wheel due to added weight by loading of pax/cargo and refuelling, the manufacturer has recommended a spacing to be maintained between the wheels and the chocks, irrespective of the parking brake position.

On some Aircraft the AMM states to keep a 6-12 inch gap between the chocks and wheel. Isn't a 2-3 in gap more realistic considering that the Aircraft could move a foot fwd or aft during a cargo loading ops on the main deck [for freighters], this could strike an GSE located around the Aircraft, also refuelling wont cause the wheels to grip the chocks beyond 3 inches.

Any reason as to why 6 inches to 12 inches....Just seems a bit too much gap.
I may not win often, but I damn well never lose!!! ;)
 
Daleaholic
Posts: 2653
Joined: Sat Oct 29, 2005 9:38 am

RE: Chock Spacing Between Wheel

Tue Jan 22, 2013 8:51 am

Leaving a gap sort of defeats the object of a chock being in place, does it not?

I've seen it done and do question it. Especially on passenger aircraft. If the aircraft rolls forward for any reason, the door could be damaged when connected to an airbridge...
Religion is an illusion of childhood... Outgrown under proper education.
 
musang
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Chock Spacing Between Wheel

Tue Jan 22, 2013 9:28 am

Quoting Daleaholic (Reply 1):
Leaving a gap sort of defeats the object of a chock being in place, does it not?

Agreed. It would be interesting to know how much the tyres spread when weight goes from empty to max.

Something I once suggested in the ground handling company I worked for was to put up a sign to show which way the parking stand sloped, and put the downhill chock in contact with the wheel, the upslope chock not in contact.

Too complicated apparently...........

Regards - musang
 
ak907
Posts: 39
Joined: Wed Mar 07, 2012 10:56 pm

RE: Chock Spacing Between Wheel

Tue Jan 22, 2013 9:54 am

I'm familiar only with heavies, 767, 747, 777 - but we rest the plane on the nosewheel chocks only. We put them in place, and the pilot releases the brakes, the plane sits on two chocks. Then we add more chocks on the main wheels, but leave about a four inch gap. These are backup if for some reason the nose gear chocks pop out. Now the only GSE I can think of that would be affected if the plane were to move this distance is the entry door stairs, and even then only if it is parked very close. The lowerdeck and maindeck doors are far enough out of the way to be not affected.

Whit this method, the plane doesn't move at all, but I agree, 6-12 inches is kind of excessive. And even if the plane settles on the chocks, it's not too difficult to get them out.

In my five years I have worked at the airport, I have never seen an airplane move because the chocks gave way.
 
KC135Hydraulics
Posts: 435
Joined: Sat Nov 03, 2012 2:05 am

RE: Chock Spacing Between Wheel

Tue Jan 22, 2013 9:59 am

When I'm refueling a C-17 our TO says to position the chocks 2 inches from the tires. Any other time the chock is to be placed against the tire. If its hard to pull later on you can pull the rear chock and use it as a sort of battering ram to pop out the stuck chock.
MSgt, USAF
KC-135R / C-17A Pneudraulic Systems Mechanic Supervisor
 
canoecarrier
Posts: 2569
Joined: Sat Feb 14, 2004 1:20 pm

RE: Chock Spacing Between Wheel

Tue Jan 22, 2013 6:58 pm

Other than the occasional difficulty to remove the chocks as the wheels expand under load pressure have you noticed tire damage because of this? When I was working GA aircraft we typically used wooden wheel chocks, I never saw any tire damage due to them.

When I worked commercial aircraft we used rubber chocks and as mentioned above if we left a small gap (2'' or so) I rarely had a problem removing a chock. Even then we would move the aircraft slightly forward or backward with the tug to relieve pressure between the tire/chock and it would come right out.
The beatings will continue until morale improves
 
harrystanhope
Posts: 21
Joined: Sun May 27, 2012 4:21 am

RE: Chock Spacing Between Wheel

Wed Jan 23, 2013 12:01 am

I work ground handling for JQ A320's, whenever I receive the aircraft i place the chocks against the wheels. Some guys kick them in but then they become hard to remove due to the loading.

Where I work, Townsville, Queensland - we use to have a procedure to place the chocks an inch or 2 away from the wheels. This gave just the right amount of space between the two..its was never anywhere near 6-12 inches. This procedure was rethought because when someone was connecting the push tug they did not stop in time and nudged the aircraft backward, I guess if the chocks were further away (6 or even 12 inches) the aircraft may have rolled a little more..then again the hand break should always be on  
 
wn676
Posts: 1116
Joined: Mon Jun 20, 2005 5:33 am

RE: Chock Spacing Between Wheel

Wed Jan 23, 2013 12:58 am

Never heard of leaving any space. On our Airbus NBs we chock both nose wheels and one of the left mains, and on 757s we chock one of the nose wheels and one of the left mains. Both are done on arrival before any equipment can approach the aircraft and no space is left in either case. It's easy on the single tires to kick the chocks out (or hit the stuck one with the other chock); on the Airbuses you have to be really good at aiming a chock to throw between the two nose wheels if one is stuck.

Maybe on widebodies it's a different story?
Tiny, unreadable text leaves ample room for interpretation.
 
User avatar
airportugal310
Posts: 3208
Joined: Sun Apr 11, 2004 12:49 pm

RE: Chock Spacing Between Wheel

Wed Jan 23, 2013 5:34 am

When I worked on the ramp for YX, we would leave 2-3in of space between the chocks and the main (717). Just the way I had been trained. For loading, was the reason I was given.
I sell airplanes and airplane accessories
 
KC135Hydraulics
Posts: 435
Joined: Sat Nov 03, 2012 2:05 am

RE: Chock Spacing Between Wheel

Wed Jan 23, 2013 9:32 am

As mentioned by others, when I have a stuck chalk on a KC-135/C-17 I use the chalk on the opposite side of the gear as a battering ram to pop the other out. Very occasionally the jet will lurch forward slightly but it's not nearly enough momentum to overcome the flat spot on the tires so it doesn't go far.
MSgt, USAF
KC-135R / C-17A Pneudraulic Systems Mechanic Supervisor
 
musang
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Chock Spacing Between Wheel

Thu Jan 24, 2013 3:56 pm

Quoting wn676 (Reply 7):
and on 757s we chock one of the nose wheels

Interesting! I worked for a handling company once, and one nosewheel of a 727 was chocked, on a sloping stand. When the hydraulic pressure bled off, the aircraft rolled gently foreward and the nose leg pivoted around the chock i.e. steered the nose gear about 45 degrees before stopping.

Regards - musang
 
FlyDeltaJets
Posts: 1631
Joined: Thu Feb 02, 2006 4:24 pm

RE: Chock Spacing Between Wheel

Fri Jan 25, 2013 7:14 am

UA policy is to have the chock to touch the wheel so that there is no space between the wheel and the chock to prevent jumping of the chock.
The only valid opinions are those based in facts
 
nwcoflyer
Posts: 677
Joined: Thu Jun 19, 2003 7:55 am

RE: Chock Spacing Between Wheel

Fri Jan 25, 2013 8:01 am

US policy is one tire on each side of the nose gear is chocked with no gap. Additionally, the right main is to be chocked as well- both sides- no gap on turns. On RON's All 3 sides of the a/c must be chocked. Seems that leaving big gaps indeed does defeat the purpose of chocks. Wonder where OAL policies differ. Yes chocks get wedged from time to time. Most of the time just kicking the chock out or hitting it with another chock before departure does the trick. Once in awhile I would have to pull the aircraft forward a little prior to push in order for a chock to be removed.
The New American is arriving.
 
musang
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Chock Spacing Between Wheel

Fri Jan 25, 2013 10:52 am

Quoting nwcoflyer (Reply 12):
US policy is one tire on each side of the nose gear is chocked with no gap.

Good point. Only a small proportion of the weight rests on the nose gear anyway (something like 6% depending on C of G?).

musang
 
User avatar
HAWK21M
Topic Author
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Chock Spacing Between Wheel

Sat Jan 26, 2013 7:08 am

Almost everyone agrees to the no gap or 2 inch max gap......Why does Boeing not revise the AMM that states 6-12inches gap on the B757.
I may not win often, but I damn well never lose!!! ;)
 
B777LRF
Posts: 1425
Joined: Sun Nov 02, 2008 4:23 am

RE: Chock Spacing Between Wheel

Sat Jan 26, 2013 12:26 pm

Our policy is to chock the nose-gear only until chocks are in place on the main(s), then they are removed. Reason: Suspect damage to nose-gear mount may happen during loading and un-loading operations. Please note, this is a freighter operation.

That's the global rule we're operating to, and is valid for every single of the 60+ carriers flying for us .... except for a single American one who "knows better".

We do not leave a gap between the chock and the wheel. Boeing has been rather inconsistent in its recommendations, so we've learned to disregard them and do what we know works.
From receips and radials over straight pipes to big fans - been there, done that, got the hearing defects to prove
 
User avatar
HAWK21M
Topic Author
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Chock Spacing Between Wheel

Mon Jan 28, 2013 6:18 am

Quoting B777LRF (Reply 15):
Please note, this is a freighter operation.

what type.....

Quoting B777LRF (Reply 15):
Boeing has been rather inconsistent in its recommendations, so we've learned to disregard them and do what we know works.

whats regulatory's take on that......
I may not win often, but I damn well never lose!!! ;)
 
canoecarrier
Posts: 2569
Joined: Sat Feb 14, 2004 1:20 pm

RE: Chock Spacing Between Wheel

Mon Jan 28, 2013 7:39 pm

Quoting HAWK21M (Reply 14):
Almost everyone agrees to the no gap or 2 inch max gap......Why does Boeing not revise the AMM that states 6-12inches gap on the B757.

I'd say that of all the operations I had to look up in a manual, the aircraft manufacturer's recommendation on chock spacing was something I'd never even thought about doing. It seems like most of us learned how to do this by a coworker when we originally started working in ground ops. Even if Boeing revises the AMM, I doubt it would change operationally how wheel chocks are placed.
The beatings will continue until morale improves
 
jetmatt777
Crew
Posts: 2809
Joined: Sun Jun 26, 2005 2:16 am

RE: Chock Spacing Between Wheel

Mon Jan 28, 2013 8:37 pm

I usually leave a 2 cm gap.
Lighten up while you still can, don't even try to understand, just find a place to make your stand and take it easy
 
fr8mech
Posts: 6606
Joined: Mon Sep 26, 2005 9:00 am

RE: Chock Spacing Between Wheel

Mon Jan 28, 2013 9:29 pm

Quoting HAWK21M (Reply 16):
whats regulatory's take on that......

The regulatory authority probably doesn't care so long as an approved procedure is written down and adhered to...and the company's procedure is more stringent that the manufacturer's.

So, if Boeing says 6 inches and company procedure says 2, you're good to go...if company procedure says 8 inches, then they need to provide justification for the deviation and chances are, the manufacturer would have to buy off on it.

Quite a waste of resources for chock placement.
When seconds count...the police are minutes away.
 
User avatar
HAWK21M
Topic Author
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Chock Spacing Between Wheel

Tue Jan 29, 2013 12:08 pm

Quoting fr8mech (Reply 19):
The regulatory authority probably doesn't care so long as an approved procedure is written down and adhered to...and the company's procedure is more stringent that the manufacturer's.

It could be the otherway around....The company has a more practical relaxed safe procedure than the manufacturer.....who decides that...Regulatory....right.
I may not win often, but I damn well never lose!!! ;)
 
B777LRF
Posts: 1425
Joined: Sun Nov 02, 2008 4:23 am

RE: Chock Spacing Between Wheel

Tue Jan 29, 2013 6:59 pm

Quoting HAWK21M (Reply 16):
what type.....

All of them (every single Boeing jet, MD-11, DC-8, A300 .....)

Quoting HAWK21M (Reply 16):
whats regulatory's take on that......

None what so ever. Our GOM lists a set of procedures that we, as a corporation, has signed off on. It's only if they're found to be seriously wrong, and results in something dramatic and expensive happening, the regulator will ever get involved in such nitty-gritty details. What's more important is what the industry has to say, in this case IATA via their IOSA and ISAGO certifications, and they're absolutely fine with it.
From receips and radials over straight pipes to big fans - been there, done that, got the hearing defects to prove
 
fr8mech
Posts: 6606
Joined: Mon Sep 26, 2005 9:00 am

RE: Chock Spacing Between Wheel

Tue Jan 29, 2013 9:54 pm

Quoting HAWK21M (Reply 20):
It could be the otherway around....The company has a more practical relaxed safe procedure than the manufacturer.....who decides that...Regulatory....right.

That's why if, in this case, the operator wants to increase the distance, that operator must seek approval from the manufacturer, but decreasing the distance does not require approval.

Also, the various procedures manuals, GOM, GMM, GPP (whatever a particular operator calls them) are approved by the FAA (here in the States)...so, presumably, they've bought off on the 2 inch policy we have.
When seconds count...the police are minutes away.
 
User avatar
HAWK21M
Topic Author
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Chock Spacing Between Wheel

Wed Jan 30, 2013 12:37 pm

Quoting B777LRF (Reply 21):
It's only if they're found to be seriously wrong, and results in something dramatic and expensive happening, the regulator will ever get involved in such nitty-gritty details.

Shouldn't Regulatory be proactive rather than reactive.

Quoting fr8mech (Reply 22):
the operator wants to increase the distance, that operator must seek approval from the manufacturer, but decreasing the distance does not require approval.

Its not necessary that reducing the distance is a better option than increasing the distance......Things could go wrong/or not go wrong on both ways.
I may not win often, but I damn well never lose!!! ;)

Who is online

Users browsing this forum: Bing [Bot], zaphod42 and 10 guests