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HAWK21M
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B753 Tail Skid

Tue Jun 17, 2008 6:38 pm

I've heard that the B753 is equipped with a Hydraulically operated tail skid assy operated by the LH system.
Can anyone confirm on the same.
Thanks.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
troubleshooter
Posts: 420
Joined: Mon Feb 07, 2005 5:22 am

RE: B753 Tail Skid

Tue Jun 17, 2008 9:35 pm

Here´s a short description of the system:

The skid extends/rectracts together with the landing gear powered by L hydraulic system.

Quote:
TAIL SKID
The force of a tail strike is transmitted to the shock absorber which contains a
crushable cartridge. If the force exceeds the capability of the cartridge, the fuse
pin releases the upper attach link. The restraining link then guides the tail skid
assembly away from the aft pressure bulkhead.
Component Description
The tail skid system has these components:
 Tail skid hydraulic actuator assembly
 Fuse pin
 Linkage
 Tail skid shock absorber assembly
 Tail skid lever assembly
The tail skid hydraulic actuator rod end attaches to a crank on the forward lock
link. The actuator head end attaches to a crank on the fuse pin. Neither end of
the actuator is attached to fixed structure. Both cranks will move during tail skid
actuation. The tail skid actuator is a two−position hydraulic actuator. The
actuator retracts to extend the tail skid ,and extends to retract the tail skid. A
restrictor in the actuator head end limits the rate of extension and retraction.
A fuse pin connects the restrain link that is attached to the fixed structure and
the upper attach link that is attached to the shock absorber assembly. If the
fuse pin breaks, the restrain link that is attached to the fixed structure and the
upper attach link will limit the motion to avoid damage to structure and other
systems.
If the fuse pin is not broken, the tail skid can be retracted and locked after the
cartridge in the shock absorber assembly is crushed.
The linkage for the tail skid includes a forward and aft lock link and an upper
attach link. The lock links hold the upper attach link, the shock absorber
assembly, and the lever assembly in the extended or retracted position.
The shock absorber assembly is centered on lower airplane structure below the
horizontal stabilizer jackscrew in the stabilizer/trim jackscrew compartment.
The crushable cartridge is inside the outer sleeve between the upper and lower
end fittings. The crushable cartridge is a cylinder that has alternating layers of
bonded corrugated and flat aluminum foil.
The indicator assembly is a cap and detent that is normally flush with the
surface of the lower end fitting. The indicator pops out after a tail strike occurs.
The tail skid lever arm extends below the bottom of the fuselage during takeoff
and landing. There is a replaceable tip (drag shoe) attached to the end of the
tail skid lever. The shoe is a painted metal part. It is the part that touches the
runway if the airplane over−rotates during takeoff or landing.

TAIL STRIKE SENSOR
The tail strike sensor is a small fin (3 in) that is designed to break or shear off
the bottom of the aft fuselage if a contact with the runway surface occurs. The
sensor is aft of the tail skid and would not contact until the tail skid shock
absorber is fully compressed.

There are two isolated channels in the tail skid sensor, one channel monitored
by the proximity sensor electronic unit (PSEU) landing gear #1 subsystem and
the other by landing gear #2 subsystem. Normally, each sensor channel is
designed to conduct.
If the sensor is damaged as a result of the sensor coming in contact with the
runway (a tail strike) both of the sensor channels will either stop conducting
(open) or conduct to airplane ground (short). For each sensor channel, a failure
of the channel to conduct or a short to ground shall be considered a tail strike
condition. The current required by the subchannel cards for a normal sensor
channel condition is limited to 25 MA. A short to ground would be indicated by
an input less than approximately 10 MA. An open would be indicated by loss of
signal.
If either landing gear system detects an open/short sensor channel input it
provides an output to EICAS to display the associated channel status
message. If both landing gear systems detect their sensor channels open/short
both cause status messages to display. Both inputs also cause the TAIL
STRIKE caution message and master caution light to display.


[Edited 2008-06-17 14:40:49]
This job sucks!!! I love this job!!!
 
troubleshooter
Posts: 420
Joined: Mon Feb 07, 2005 5:22 am

RE: B753 Tail Skid

Tue Jun 17, 2008 9:43 pm

double post, SORRY!!!

[Edited 2008-06-17 14:52:58]
This job sucks!!! I love this job!!!
 
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HAWK21M
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Joined: Fri Jan 05, 2001 10:05 pm

RE: B753 Tail Skid

Wed Jun 18, 2008 9:34 am

Thanks.Do you have a pictoral view of the unit.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
troubleshooter
Posts: 420
Joined: Mon Feb 07, 2005 5:22 am

RE: B753 Tail Skid

Wed Jun 18, 2008 2:42 pm


View Large View Medium
Click here for bigger photo!

Photo © Freight-Dawg - Airside Photography



Here´s a quite good view of the tail skid. The tail strike sensor is behind. It is the small yellow fin which looks like an antenna. Hope this helps.
This job sucks!!! I love this job!!!
 
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HAWK21M
Topic Author
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: B753 Tail Skid

Wed Jun 18, 2008 3:52 pm



Quoting Troubleshooter (Reply 4):
Here´s a quite good view of the tail skid. The tail strike sensor is behind. It is the small yellow fin which looks like an antenna. Hope this helps.

The Sensor looks sized like an ADF/DME antenna.

On the pic,the photographer indicates O2 servicing being done on the rear aircraft.Is that permitted.Out here no online Servicing/charging of O2 is permitted,only O2 bottles can be replaced.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
N353SK
Posts: 826
Joined: Thu Jun 08, 2006 5:08 am

RE: B753 Tail Skid

Wed Jun 18, 2008 5:34 pm

I believe the 767-400 also has a tail skid.
 
PC12Fan
Posts: 1976
Joined: Sat Jan 27, 2007 11:50 pm

RE: B753 Tail Skid

Fri Jul 11, 2008 7:27 pm

As does the 767-300.


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