Aeromexico
flight 498 left Tijuana, Mexico on the
morning of August 31, 1986 bound for Los
Angeles. 58 passengers and six crew
members were on board the DC-9 as it
made it's approach to LAX. Meanwhile, a
Piper Archer carrying a family of three
had departed Torrance Municipal Airport
bound for Big Bear.
It was a clear day in
the Los Angeles basin with visibility
reported at 15 miles. The Archer was on
an easterly climb while 498 was
descending to the northwest. At an
approximate altitude of 6,500ft, the two
aircraft collided, the horizontal
stabilizer of the DC-9 slicing through
the cockpit of the Archer. 498 rolled
onto it's back and fell inverted into a
residential area, the Archer impacting
in a school yard about a quarter of a
mile away. All aboard both planes were
killed in the accident along with 15
people on the ground. 18 houses were
destroyed in the impact.
......The Archer was equipped with a
non-encoding transponder, meaning it's
radar return did not include it's
altitude. The controller working the
aircraft at the time did not remember
seeing the return from the Archer,
though review of the ATC tapes showed
that it was visible. The Archer was
operating VFR and had not received a
clearance to enter the Los Angeles
Terminal Control Area. Radar data showed
that the aircraft had penetrated the LA
TCA eight minutes after departing
Torrance, straying into the path of
Aeromexico 498.
At about the same
time the Archer entered the LA TCA,
another aircraft also strayed into the
airspace in the path of a commuter
aircraft. The controller was temporarily
distracted during it's communication
with the aircraft and when he had
returned his attention, the collision
had already occurred. Because there was
no altitude reported for the Archer and
it had neither requested nor received a
clearance to enter the LA TCA, the
controller had no idea that it was not
staying below of the floor of the
airspace.
Examination of the
wreckage showed that the pilot of the
Archer had the LA TCA chart open during
the flight, so no clues were given as to
the deviation. In addition, by operating
VFR, the pilot of the Archer was
assuming responsibility for collision
avoidance. Based on the flight paths of
the aircraft, both pilots should have
been able to see each other. Because of
this accident, the FAA now requires that
all aircraft flying in a 30nm radius of
the primary airport of a TCA/Class B
airspace be equipped with an
altitude-encoding transponder.
