Action Follows Incident In Which Thrust Reversers Were A
The FAA has issued a Safety Alert
For Operators (SAFO) outlining training procedures for pilots of
Learjet 60 aircraft. The SAFO is designed to ensure that Learjet 60
Training curriculums properly address the best practices on
recognizing thrust reverser(s) stowage while commanding deployment
during takeoff and landing phases of flight.
The SAFO is the result of an incident on September 19, 2008, in
which a Learjet 60 overran runway 11 while departing Columbia
Metropolitan Airport, South Carolina. Sparks were observed on the
takeoff roll, and the pilot initiated a rejected takeoff. The
airplane continued beyond the runway, struck an embankment, and was
destroyed by post-crash fire. The flight crew and two passengers
were killed and two other passengers seriously injured.
Post-accident examination of markings and tire debris indicated
that during the takeoff, the right outboard tire failed from
apparent under inflation. Subsequently the other tires failed,
which damaged a squat switch. This resulted in thrust reversers
stowage while deployment was commanded, resulting in
high forward thrust from both engines.
Pilots should be aware of the possibility that thrust reverser
stowage can occur while deployed if the air/ground squat switch
circuits are damaged. Under these conditions, it is possible that a
damaged squat switch may incorrectly sense that the aircraft is in
air mode and stow or prohibit the reverser(s) from activating.
Accordingly, the engines would provide forward thrust even though
the reverse levers are in reverse position. The degree of forward
thrust would be commensurate with the angle of the reverse thrust
lever position commanded by the pilots. The only way to reduce
forward thrust under these abnormal circumstances is to move the
reverse levers to the stowed position, which is counterintuitive to
a pilot during a rejected takeoff.
If the thrust reversers inadvertently stow during a rejected
takeoff or landing, the pilots would note the following
- The white TR DEPLOY lights would extinguish.
- The amber TR UNLOCK lights would illuminate momentarily.
- The green TR ARM lights would blink momentarily during the
transition to stow.
Learjet 60XR (thrust reverser indications are displayed on the
Engine Page in the Learjet 60XR):
- The white DEP annunciations would extinguish.
- The red UNL annunciations would illuminate momentarily.
- The amber REV annunciations may flash momentarily.
The only indication available to the pilots that the
cockpit reverse levers and engine thrust reverser(s) do not agree,
would be the pilots’ comprehension that neither of the TR
DEPLOY or DEP annunciations are illuminated, with the reverser
levers in the position normally associated with reverse thrust.
Unless exposed to the need for evaluating reverse thrust indicator
lights when reverse thrust deployment is commanded, pilots may not
properly diagnose a thrust reverser failure during critical phases
of flight. Additionally, it will be difficult for a pilot to
recognize the absence of reverse thrust solely by indicator lights
while attention is focused outside the aircraft. This issue and its
implications must be stressed during training.
The FAA recommends that in the event of inadvertent and or
un-commanded thrust reverser stowage; maintain directional control,
immediately stow both thrust reverses, reduce thrust to idle and
initiate maximum braking effort. Directors of safety, directors of
operations, training center program managers and individuals
responsible for training programs are encouraged to review their
training curriculums to ensure emphasis on recognizing inadvertent
stowage of thrust reversers during takeoff and landing phases of