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.
The tail skid system has these components:
Tail skid hydraulic actuator assembly
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
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
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.
|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.
Military Aircraft Every type from fighters to helicopters from air forces around the globe
Classic Airliners Props and jets from the good old days
Flight Decks Views from inside the cockpit
Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior
Cargo Aircraft Pictures of great freighter aircraft
Government Aircraft Aircraft flying government officials
Helicopters Our large helicopter section. Both military and civil versions
Blimps / Airships Everything from the Goodyear blimp to the Zeppelin
Night Photos Beautiful shots taken while the sun is below the horizon
Accidents Accident, incident and crash related photos
Air to Air Photos taken by airborne photographers of airborne aircraft
Special Paint Schemes Aircraft painted in beautiful and original liveries
Airport Overviews Airport overviews from the air or ground
Tails and Winglets Tail and Winglet closeups with beautiful airline logos