August marked the anniversary of two remarkable aircraft accidents, the affects of which we feel on every flight, even 25 years later.
On August 31, 1986, a Piper Archer and an Aeromexico DC-9 collided over the community of Cerritos, California, killing all 64 on the airliner and the three occupants of the Archer. In addition, 15 people on the ground were killed and five homes destroyed and seven damaged by fire and falling debris. The Archer was squawking VFR with a Mode A (non-altitude-reporting) transponder and inadvertently penetrated the bottom of the Los Angeles Terminal Control Area (today we call that Class B airspace).
The accident led to the mandate for Mode C (altitude-reporting) transponders around Class B airspace and even beyond the Class B borders in what is known as the Mode C veil. The convulted airspace around Los Angeles is in part also a result of the Cerritos accident, as ATC attempts to separate loads of airline and GA traffic around dozens of airports.
I worked for an independent aviation magazine at the time and remember the remarkable effort by AOPA public relations staff to attempt to protect GA from onerous new regulations. Any time people on the ground are injured or killed from an aircraft accident, the potential for knee-jerk regulations escalates. Killing 15 on the ground was unprecedented. The media frenzy went on for months and AOPA staff worked admirably through it all, advocating for reasonable changes that improve safety without compromising the ability to take advantage of the versatility and utility possible with GA aircraft.
Discussions of requirements for airliners to carry collision avoidance systems was already underway, but the Cerritos accident escalated that talk. The TCAS mandate followed quickly, and today all airliners and many GA aircraft carry such systems.
Fortunately, discussions to require Mode C transponders in all types of airspace at all times–even from aircraft without electrical systems–calmed with time and thanks to AOPA’s input. The debate about the Mode C veil would continue for years before finally being implemented in the late 1980s.
However, what we learned about collision avoidance from Cerritos pales compared to what we learned about microbursts from the Delta Airlines accident at Dallas-Fort Worth International a year earlier on August 2, 1985. The Delta L-1011 was en route from Fort Lauderdale to Los Angeles with a stop in Dallas. On approach to DFW, the airliner tangled with a thunderstorm that slammed it into the ground, killing 8 of 11 crew members and 126 of the 152 passengers as well as one person on the ground. A massive investigation showed that the airplane encountered a little understood windshear phenomenon that became to be called a “microburst.” Essentially, a large burst of air near a thunderstorm that slams into the ground, robbing an airplane on approach of critical airspeed.
As a result of that accident, we soon saw the development of low-level wind sheer alert systems at major airports, more sophisticated algorithms in next-gen weather radars that look for microburst signatures, and new generation airborne weather radars that also seek to alert to microbursts and turbulence. In addition, training scenarios were established to help pilots recognize microburst situations and escape from them.
Here’s hoping we continue learning from such accidents and see no more of them.