The story of the CVR and the man with blinders

blinders3If there was one thing that caused the investigation of TWA 841 to go off the rails, it was the discovery that there were only nine minutes of recorded audio on the thirty minute CVR tape. This was discovered within days of the incident. A bulk erase tone was present on the remaining 21 minutes of tape, indicating that the CVR had been bulk erased. There is an erase button in the cockpit that crews can use to erase the CVR. The button was placed there to appease pilots who opposed CVRs in the cockpit. The regulations state that you are not to erase the CVR in the event of an incident. Since the tape had been bulk erased, the NTSB concluded that the crew had deliberately erased the CVR to cover something up. The crew testified under oath that they did not erase the CVR. Hoot testified that it was his routine to erase the CVR after every flight, but he did not remember doing it on this flight.

In order to erase the CVR two conditions had to be met: the aircraft has to be on the ground, and the brakes have to be parked. Later on in the investigation someone came to the realization that maybe there was a problem with the CVR.  The CVR had been removed the night of the accident. The electrical wiring that sent signals to the CVR that the plane was on the ground and the brakes were parked were severely damaged. That electrical wiring was repaired within days of the incident. So to cover their tracks the Investigator in Charge contacted TWA to ask them if there had been any problems with the electrical connections to the CVR. Not wanting to take the blame for mishandling an important aspect of the investigation, TWA replied that there were no problems found. So now everyone was covered from this glaring oversight. Here is how the official report reads:

Tests of the CVR in the aircraft revealed no discrepancies in the CVR’s electrical and recording systems.

That is a false statement. For one, there had not been any tests done on the CVR before or after it was removed. Here is what mechanic Mel Brown, who removed the CVR within hours of the incident, had to say about the CVR electrical system:

A. One other thing I was thinking about, you know all the wiring around the gear switches were ripped right out. I don’t know if this had any effect on that voice recorder.

Q. Was the right gear safety switch completely gone?

A. The right and left gear switches, yes. All the warning switches. I’m sure you could find that through the inspection department in Kansas City. They had a detailed write-up on all this.

Q. So, in other words, the wiring to the boxes was actually loose.

A. Yes, some of it was just ripped right off and the boxes pulled away and the linkage was just hanging there…

By this time the investigation had separated into two camps: Boeing and the NTSB spent all of their time trying to prove that the crew had done something to cause the slat to extend; TWA and ALPA spent all of their time trying to prove that the slat had come out on its own. We now know that it was all wasted energy because the slat wasn’t even involved.

Yet the erased CVR continued to implant a bias on all parties of the investigation. It actually got to the point where the NTSB chairman suggested that the investigation would have been a lot easier had the plane crashed. Here is the actual exchange:

King:…And you are telling us that, in this particular case if the slat hadn’t failed, the chances of its recovery then become marginal, at best?

Tobiason (Richard Tobiason chairman of the performance group): Yes, sir.

King: And certainly random?

Tobiason: That is correct.

King: And for our purposes, we would have recovered probably all the instrumentation and had an easier case to work with, which is, indeed unfortunate. It would have made a very big hole in the ground.

The erased CVR also found its way into the NTSB findings of probable cause:

We believe the captain’s erasure of the CVR is a factor we cannot ignore and cannot sanction.

Remember, there was never any proof found that anyone erased the CVR deliberately or otherwise. As you can see the CVR played a significant role in this investigation. However, when the NTSB finally responded to Hoot’s petition for reconsideration, here is what they had to say about the CVR:

…The only audio evidence from the CVR that was available to the investigation was a brief crew conversation that was determined to have taken place after the airplane had landed in Detroit. As a result, the Safety Board concludes that the CVR information is largely irrelevant to the investigation and should not be a subject for reconsideration.

The end result of the crew coming under suspicion was that they were excluded from the investigation. This is true of TWA and ALPA as well. Hoot was told to not make any noise. “If you want our help, then let us handle this,” they told him. It was as if the investigators all had blinders on. But by not taking the time to thoroughly question the crew, important details were either not received or overlooked. This not only frustrated the crew, but it also frustrated some of the investigators.

One investigator, Gene York, went as far as to purchase a voice stress analyzer that he wanted to use to prove that the crew was telling the truth. He paid for the $8,500 device with his own money. The lead ALPA investigators told him that he couldn’t use the device. Below is a clip of an interview with Gene York, one of the original investigators on TWA 841.



  1. […] my previous post,  The story of the CVR and the man with blinders, I talked about how the crew was excluded from the investigation. Three expert witnesses and no one […]

  2. […] the aircraft or after it was removed from the aircraft. You can learn more about this in the post, The story of the CVR and the man with blinders. In reviewing the civil trial held in May of 1983, I came across the testimony of George Andre, a […]

Speak Your Mind