Tesla Airplane Crash Investigation Gets Uunexpected Clue

One wonders if we are not already at the age of Big Brother, in light of the most recent, albeit, welcome news that the airplane crash that killed three executives of Tesla Motors was caught on audio tape and is now providing assistance to air safety investigators.


On Wednesday, February 17th, Douglas Bourn a senior engineer at the electric car company Tesla Motors, flew his 33 year old Cessna 310 into a high power transmission line shortly after taking off from Palo Alto Municipal Airport in California. Mr. Bourn, an experienced pilot, multi-engine, instrument rated and a certified flight instructor failed to make the required departure turn out over the bay and instead flew the plane into the tower killing himself and the other two executives who were passengers on the flight.

The limited visibility conditions on Wednesday morning may have been an added complication. A pilot who arrived at the airport shortly after Mr. Bourn took off told a reporter visibility was terrible. The NTSB puts it at 1/8^th of a mile. Either way, Wallace Moran, a retired airline captain and F.A.A. pilot examiner who has frequently flown from Palo Alto airports told me, he suspects something else went wrong and limited visibility might have just compounded the problem.

“There are other things that could cause him to go in the wrong direction either instrument issues with the airplane or a medical condition with the pilot, so the NTSB will look at those possibilities.”

What the NTSB has to work with, and this is really a fascinating wrinkle to the investigation, is a series of five audio tapes made from a city wide acoustic surveillance system in East Palo Alto, California. I’ve posted one of them here.

As Police Department Capt. Curt Estelle explained it to me, eighteen months ago the city installed the ShotSpotter recording system. The recording triggers when the sensors detect the kinds of sound associated with gunfire and a report and location information is sent to the police department. “It allows us to respond a lot faster and with a lot more precise location information rather than waiting for citizens to call,” Capt. Estelle told me.

I don’t know what kind of crime problem they have in East Palo Alto, but Capt. Estelle says the department gets about 100 triggering events a month including fireworks which are illegal there. Plane crashes? Capt. Estelle says this is the first.

It was quick thinking on the part of ShotSpotter president James Beldock that resulted in capturing the sound of the crash and putting it together for NTSB investigator in charge Josh Cawthra. Within minutes of learning about the accident, Mr. Beldock checked to see if the system picked up either the engine or impact noise. It had.

This gives Mr. Cawthra an unexpected clue, five recordings of the sound of the airplane as it approached impact and several seconds following, recorded at distances ranging from 600 to 1500 feet. As dramatic as it might be to the lay listener, these recordings should prove illuminating to the specialists in the NTSB sound lab, where Mr. Cawthra said they are now headed.

I was curious to know how a recording system that triggers on certain sound frequencies actually catches the sounds preceding initiation. Mr. Beldock explained it to me yesterday, while I was interviewing him for The New York Times Wheels blog. As it turns out, the system has a “trailing buffer,” which from what I can tell means it is actually always recording.

“You often hear noises right before a shooting and that’s important,” Mr. Beldock explained. A sound determined by the system to be significant, prompts the memory to store the sounds immediately beforehand. Otherwise that memory is constantly recording over itself.

In the midst of the tragedy for Tesla and for the dozens of people in the community who were certainly traumatized by the event, this technological “who’duh thunk it?” provides a tiny bright spot.