Gear won't retract because of loose tyre tread?

[simtronix]

Quote from 737NG ops manual:

"A spinning tire with a loose tread must be stopped prior to entering the wheel well or it can cause damage to wheel well components. When a spinning tire with loose tread impacts a fitting in the wheel well ring opening, that gear stops retracting and free falls back to the down position. The affected gear cannot be retracted until the fitting is replaced."

Does anyone know what that fitting is and or where it is located? Exactly how does this fitting interrupt the retraction process?

[IFixPlanes]

Hi simtronix
This frangible fitting is installed in the gear up hydraulic line of the retraction.
The loose tread dismantle the lower part of the frangible fitting.
Now you have a unusual high fluid flow through the fuse.
AMM: "Volume fuse in the up pressure line closes when the hydraulic flow through the frangible fitting increases to 180-250 cubic inches (3-4 liters). This stops the loss of fluid from the hydraulic system." ... by closing the fuse.
And with this stop you interrupt the fluidstream to get the gear up and it fall back down.
http://img195.exs.cx/img195/9338/frangiblefitting033lf.th.jpg (http://img195.exs.cx/my.php?loc=img195&image=frangiblefitting033lf.jpg)
http://img195.exs.cx/img195/2610/frangiblefitting049oc.th.jpg (http://img195.exs.cx/my.php?loc=img195&image=frangiblefitting049oc.jpg)

HIH

Ingo

[CaptainSandL]

http://www.b737.org.uk/tyredamagefitting.jpg

From http://www.b737.org.uk/landinggear.htm

The pin is shown in the centre of this photo. There are two, they are at the aft outside of each side of the wheel-well.