"Capt.Doug" wrote

On the B-727, autospoilers deploy upon compression of the left main
strut.

The rest of the story..........


AUTOSPEEDBRAKES
When on the ground, the autospeedbrake system will automatically
extend the spoilers whenever reverse thrust is used, regardless
of whether the speedbrake handle has been placed in the ARM detent.
This ensures that the spoilers will be extended for every landing
and rejected takeoff.
If the speedbrake lever is placed in the ARM detent before landing,
the autospeedbrake system will automatically extend the spoilers
when the airplane is firmly on the ground. If a go-around in
initiated after landing, the speedbrake lever automatically returns
to the DN position when the No. 1 or No. 3 throttle is advanced to
go-around thrust.

If the speedbrake lever is not in the ARM detent, the lever will
automatically be raised out of the DN detent to the ARM detent
whenever either the No. 1 or No. 2 reverse thrust lever is moved
into idle reverse.

The autospeedbrake system includes a motor that will, on signal,
drive the speedbrake lever to the uP or DN position. System
operation is confirmed by observing speedbrake lever movement.

The autospeedbrake motor always runs to the up or down limit of
the speedbrake lever and then shuts off. Thereafter, manual
operation will slip the motor clutch and the speedbrake lever will
remain in the manually selected position.

An electrical malfunction of the automatic speedbrake system is
indicated by illumination of the SPEED BRAKE DO NOT ARM light when
the speedbrake lever is set in the ARM detent.

The SPEED BRAKE DO NOT ARM light will also illuminate after landing
when the airplane's wheel speed is below 60 kt.

To automatically extend the spoilers, the following interlocks
and logic must be satisfied:
• The speedbrake lever must be in the ARM detent. This provision
is bypassed by either the No. 1 or No. 2 reverse lever being
in the idle reverse position.
• The airplane must be on the ground (as determined by the left
main gear) or one wheel on each main gear must have attained a
.. speed of over 60 kt.
• No. 1 and No. 3 throttle at idle position.
• No retract signal to the autospeedbrake motor re-tract relay.

The autospeedbrake system can be overridden manually at any time.