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HAWK21M
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Chocks On Parked Aircraft

Fri Jun 27, 2008 8:41 am

What are the requirements in terms of numbers on parked aircraft,either with power on,as in transitting aircraft & power off for long halt aircraft out there.

Here its minimum six chocks per Aircraft & of rubberised material.

regds
MEL
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wilco737
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 8:46 am



Quoting HAWK21M (Thread starter):

We only use 4. 2 on the left main gear (rear and front) and 2 on the right main gear (rear and front).

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HAWK21M
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 9:00 am



Quoting WILCO737 (Reply 1):
We only use 4. 2 on the left main gear (rear and front) and 2 on the right main gear (rear and front).

I presume you are talking about MD11?
Are these cocks wide enough to cover both Main wheels or just one.
Also why no chocks on the NLG.

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MEL
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wilco737
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 9:10 am



Quoting HAWK21M (Reply 2):
I presume you are talking about MD11?

 thumbsup 

Quoting HAWK21M (Reply 2):
Are these cocks wide enough to cover both Main wheels or just one.

Just the outer ones. One each

Quoting HAWK21M (Reply 2):
Also why no chocks on the NLG.

no.

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aogdesk
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 11:07 am



Quoting HAWK21M (Reply 2):
I presume you are talking about MD11?
Are these cocks wide enough to cover both Main wheels or just one.

Wilco737: I'm soooo disappointed that you didn't take the opportunity to answer "why yes, my cock is wide enough to cover both main wheels on an MD-11".

Or am I just an immature idiot? I think I know the answer to that.......sigh..... Wink
 
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 11:09 am



Quoting Aogdesk (Reply 4):
Wilco737: I'm soooo disappointed that you didn't take the opportunity to answer "why yes, my cock is wide enough to cover both main wheels on an MD-11".

 rotfl  I didn't even see that typo! but indeed a good one  Wink  bigthumbsup 

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fr8mech
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 12:28 pm

Typically, you don't want to chock the nose gear or center gear on an MD11 or DC10. As the aircraft loads and fuels, the nose and center gears will walk forward because of their geometry. Any forward canted gear will walk as the aircraft gets heavier.

The number of chocks installed is usually a matter of company policy.
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HAWK21M
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 2:50 pm



Quoting WILCO737 (Reply 5):
I didn't even see that typo! but indeed a good one

Hey I did not notice that typo too.... Guess we are getting serious on this forum.  Smile

Quoting Fr8Mech (Reply 6):

Typically, you don't want to chock the nose gear or center gear on an MD11 or DC10. As the aircraft loads and fuels, the nose and center gears will walk forward because of their geometry. Any forward canted gear will walk as the aircraft gets heavier.

On the B752 we use the NLG chocks & keep a space forward & aft of the chocks for such events.The AMM states ideal 6 inches spacings ,which is quite a lot.

Also some operators use Towbarless Tugs that grip the NLG,so could that be a reason,if the Tug is already attached.

regds
MEL
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fr8mech
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 7:45 pm



Quoting HAWK21M (Reply 7):
On the B752 we use the NLG chocks & keep a space forward & aft of the chocks for such events.The AMM states ideal 6 inches spacings ,which is quite a lot.

We use 2" on all chocks. We do chock the nose and center but use 6 ". Other operators choose not to chock to avoid the issue all together.

The B757, and all straight leg gear, should not walk during load/unload operations.
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airtran737
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RE: Chocks On Parked Aircraft

Fri Jun 27, 2008 9:30 pm

We (WO) chock the nose, and the mains. Nothing on the middle gear.



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josekmlb
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 2:56 am

We use 4 for the mains on the MD-88 and one long one for the nose. On the CRJ 4 for the mains and 2 for the nose. On the A320 4 for the mains and 2 for the nose.
 
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 3:34 am

How are planes chocked when doing high power engine runs? Are they all chocked?
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vikkyvik
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 5:39 am



Quoting Fr8Mech (Reply 6):
Typically, you don't want to chock the nose gear or center gear on an MD11 or DC10. As the aircraft loads and fuels, the nose and center gears will walk forward because of their geometry. Any forward canted gear will walk as the aircraft gets heavier.

Do you mean that the nose gear and center main gear on the DC-10 and MD-11 are not vertical when extended? Out of curiousity, is there a particular reason for this?

Quoting Aogdesk (Reply 4):
Or am I just an immature idiot? I think I know the answer to that.......sigh....

Nothing wrong with a mind in the gutter. I spotted that typo as soon as I read the reply, and would have commented on it had it not already been brought up  Smile
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 6:45 am



Quoting Vikkyvik (Reply 12):
Do you mean that the nose gear and center main gear on the DC-10 and MD-11 are not vertical when extended? Out of curiousity, is there a particular reason for this?

The MD-11 nose gear is canted forward a few degrees, as shown below.


View Large View Medium
Click here for bigger photo!

Photo © Jerry Pang



I believe that the reason for canting the nose leg forward, would most probably be related to the need to provide a self centering function for the nose-wheel steering. Canting the nose-leg achieves a similar outcome to the rake and trail geometry used on motorbikes.

Because the projected axis of the nose-leg upon the ground is forward of the tire contact point, there exists a couple which tends to return the nose-wheels to the straight ahead position if they are displaced.

Aircraft such as the A330 / A340, and B747 have nose-legs that are vertical. The self centering function is achieved in these cases, by having the centre-line of the axle a certain distance behind the centre-line of the nose leg. This arrangement acts like a shopping trolley castor to provide the self centering function. You can see from the picture below, that the nosewheel axle of the 747 is located several inches behind the axis of the strut.


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Click here for bigger photo!

Photo © Willem Honders



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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 7:54 am



Quoting HAWK21M (Thread starter):
What are the requirements in terms of numbers on parked aircraft,either with power on,as in transitting aircraft & power off for long halt aircraft out there.

Depends on who I was working for at the time.

Alaska it was the port maingear that got the chock.
At Reeve we just would chock the NG for a flight.
If it was an RON flight all three wheels
At FS We would chock one of the mains. Usually the port side on the lears and the Casa and the port main on the metro because on one of ours the power cord plugged in there.
If we knew the weather was going to be bad overnight we would do both mains.
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HAWK21M
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 8:48 am



Quoting Fr8Mech (Reply 8):
The B757, and all straight leg gear, should not walk during load/unload operations.

At Transitting Aircraft,We keep the Parking brake set too,in addition to the Six chocks.

Quoting AirframeAS (Reply 11):

How are planes chocked when doing high power engine runs? Are they all chocked?

Out here for High power runs only the NLG is chocked,& no one on ground around till thrust levers brought back to Idle.

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AirframeAS
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 3:12 pm



Quoting HAWK21M (Reply 15):
Out here for High power runs only the NLG is chocked...

Same at AS, I just wondered how other airlines do it. When I was there, we used HUGE chocks with metal chain linkages to ensure that the chocks don't get sucked into the intake.

Quoting HAWK21M (Reply 15):
....& no one on ground around till thrust levers brought back to Idle.

We have had guys outside on high power runs, just about 100 feet from the aircraft or so with headsets on.
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HAWK21M
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 5:18 pm



Quoting AirframeAS (Reply 16):
We have had guys outside on high power runs, just about 100 feet from the aircraft or so with headsets on.

Risk of permanant ear damage is the minor risk here. Smile
Not advisable.
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 6:08 pm



Quoting JetMech (Reply 13):

I believe that the reason for canting the nose leg forward, would most probably be related to the need to provide a self centering function for the nose-wheel steering. Canting the nose-leg achieves a similar outcome to the rake and trail geometry used on motorbikes.

Because the projected axis of the nose-leg upon the ground is forward of the tire contact point, there exists a couple which tends to return the nose-wheels to the straight ahead position if they are displaced.

You are exactly right. As someone who works on designing the steering system of a plane, caster is very important. If you lose steering capability and have to steer only with the rudder (high speed) or differential braking (low speed), you need caster in the front wheel. That allows it to naturally center, or follow the plane in a turn. If it didn't have caster, then it might be tempted to rotate on its own, which would cause major steering problems.

On most planes, it is done by having the nose gear angled forward and locating the axis of the wheels behind the line of axis through the nose gear axis. If that sounds confusing, just look at a bicycle because they are all made with caster. The wheel is not in line with the axis of the strut.
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RE: Chocks On Parked Aircraft

Sat Jun 28, 2008 9:44 pm



Quoting HAWK21M (Reply 15):
At Transitting Aircraft,We keep the Parking brake set too,in addition to the Six chocks

Brakes are always off after chocking. Reduces the heat stress on the brakes.

We rarley chock during high power runs and never have a person on the headset during high power. We use fuel for ballast as recommended in the AMM.
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KingAir200
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RE: Chocks On Parked Aircraft

Sun Jun 29, 2008 2:33 am

We always chock the nose and both mains on 319/320s and DC-9-30s. We only chock the mains on DC-9-40s and -50s because of the spray deflector on the nose gear. On CRJ turns, we'll chock the nose gear and the right main gear. For terminators, we chock all three.
 
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HAWK21M
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RE: Chocks On Parked Aircraft

Sun Jun 29, 2008 6:41 am



Quoting Fr8mech (Reply 19):
Brakes are always off after chocking. Reduces the heat stress on the brakes.

On our B752SFs & B752PCFs.since the EICAS status screen does show the Brake temperature,its normally monitored & Parking brakes are set,though Hydraulics are switched off unless there is strong winds around.

Loading & Unloading operations on B752 freighters does cause mvmt of the Aircraft along the longutional axis & to a lesser degree vertically.having the parking brakes set along with the Six chocks does help.

regds
MEL
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fr8mech
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RE: Chocks On Parked Aircraft

Sun Jun 29, 2008 6:02 pm



Quoting HAWK21M (Reply 21):
On our B752SFs & B752PCFs.since the EICAS status screen does show the Brake temperature,its normally monitored & Parking brakes are set,though Hydraulics are switched off unless there is strong winds around.

So you put someone on the flight deck to monitor the brake temps? The problem isn't so much the temperature as the possibility that the heat stack fuse or warp when it's under pressure and cooling after a stop.

We don't have brake temp installed on our B757's.
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Tristarsteve
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RE: Chocks On Parked Aircraft

Sun Jun 29, 2008 6:49 pm



Quoting Fr8Mech (Reply 22):
So you put someone on the flight deck to monitor the brake temps? The problem isn't so much the temperature as the possibility that the heat stack fuse or warp when it's under pressure and cooling after a stop.

About 5 years ago British Airways standardised the procedure on all their aircraft. The brakes stay on all the time. Both main gears are chocked fore and aft. We don't chock the nose because we normally use TBLs and it can be embarrassing if the NLG chock gets stuck!
On an overnight the NLG is chocked as well because on Boeing aircraft the park brake pressure bleeds away slowly and can be zero after 10 hours. Airbus don't have this problem because of a different park brake hyd set up.
When I have a B757 nightstopping, and high winds forecast, I try and park a TBL on the nosegear. (We only have two nightstops).
 
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HAWK21M
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RE: Chocks On Parked Aircraft

Mon Jun 30, 2008 5:33 am



Quoting Fr8Mech (Reply 22):
So you put someone on the flight deck to monitor the brake temps

The brakes if warm on arrival is very noticable & parking brake can be switched off.
As mentioned Hyds are off unless there are strong winds around.

Quoting Fr8Mech (Reply 22):
We don't have brake temp installed on our B757's.

Its a customer option.I sure would like our EICAS screens to display wheel pressure though  Smile

Quoting TristarSteve (Reply 23):
On an overnight the NLG is chocked as well because on Boeing aircraft the park brake pressure bleeds away slowly and can be zero after 10 hours.

We normally carry out a reset every 8 hrs if needed.

regds
MEL
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kbfispotter
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RE: Chocks On Parked Aircraft

Mon Jun 30, 2008 5:00 pm

At QX, the NLG on the Dash-8 gets chocked during normal turns at the gate, and the CRJ gets a MLG chocked. All wheels get chocked as well if we have to run the plane at the gate. When we have a plane parked at our hardstand in SEA, all three gears get chocked.

Quoting AirframeAS (Reply 11):
How are planes chocked when doing high power engine runs? Are they all chocked?

We do not chock our aircraft during high speed engine runs, as there is no one around to chock them for us... The SEA high power run pad is on the active taxiway, at the south end of Bravo when rnwy 16 is in use, and the north end of Bravo when 34 is in use. We need to be able to get out of there quickly if we have to. Plus, the brakes on our Dash's and CRJ's can hold the aircraft at power.

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RE: Chocks On Parked Aircraft

Mon Jun 30, 2008 5:20 pm



Quoting JetMech (Reply 13):
Canting the nose-leg achieves a similar outcome to the rake and trail geometry used on motorbikes.

For completeness, this is usually referred to as "caster angle" (in the UK at least) and absolutely has the effect of forcing a self-centering moment on the wheels.

I have no empirical evidence of this, but of the cars and trucks I have observed, those with power steering tend to have a greater caster angles. They benefit from better stability at speed, and have a powered steering rack to overcome it. Driving a car with PAS that has failed is really quite unpleasant and I would not do it on the open road.

Quoting RoseFlyer (Reply 18):
If it didn't have caster, then it might be tempted to rotate on its own, which would cause major steering problems.

I started my post before I saw your really-rather-good one, but will let it stand because it illustrates a point. Lack of caster angle coupled with a loss in directional control gives you shopping trolley handling.

Conversely, too much caster coupled with a lack of contol gives all the handling properties of a very angry horse.
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RE: Chocks On Parked Aircraft

Tue Jul 01, 2008 1:41 am



Quoting HAWK21M (Reply 17):
Risk of permanant ear damage is the minor risk here.  Smile
Not advisable.

True, it was still done at AS. Everyone wore earplugs with the earmuffs.
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CX Flyboy
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RE: Chocks On Parked Aircraft

Tue Jul 01, 2008 2:49 am

I have seen metal-frame type chocks used on my 777 as well as wooden blocks in addition to the rubberised type. There are usually chocks infront and behind one side of the NLG and chocks infront and behind the outer set of MLG on the left and right,
 
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HAWK21M
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RE: Chocks On Parked Aircraft

Tue Jul 01, 2008 9:07 am

From the list of Wooden,Metal & rubber....The rubber chocks would be most effective grip wise.
wooden chocks would be used for lighter aircraft.

regds
MEL
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wn676
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RE: Chocks On Parked Aircraft

Wed Jul 02, 2008 10:34 pm

For our high power runs we have these huge orange things that kind of look like the thing they use to jack race cars up during pit stops. They're shaped to fit the mains, and we slide them under and then pull this big handle down to lock them in place. The NLG gets regular rubber chocks.
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HAWK21M
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RE: Chocks On Parked Aircraft

Thu Jul 03, 2008 6:18 am



Quoting Wn676 (Reply 30):
these huge orange things

Any picture available?
regds
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FlyASAGuy2005
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RE: Chocks On Parked Aircraft

Thu Jul 03, 2008 8:50 am

With us (ASA) its SOP to have two on the left main and two on the nose. If the a/c is RON or there is no crew on board at the time and the door is to be closed, we add the extra two on the right main.
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HAWK21M
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RE: Chocks On Parked Aircraft

Thu Jul 03, 2008 4:37 pm



Quoting FlyASAGuy2005 (Reply 32):
With us (ASA) its SOP to have two on the left main and two on the nose. If the a/c is RON or there is no crew on board at the time and the door is to be closed, we add the extra two on the right main.

Whats the status of the Parking brake at this time.
regds
MEL
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