Thursday, May 07, 2009

Air Tahoma Convair 580 fatal crash in Ohio: NTSB Preliminary Report

Air TahomaThe U.S. National Transportation Safety Board (NTSB) has released a Preliminary Report containing new information about the investigation of the fatal crash of an Air Tahoma Convair 580 (CV-580) freighter in 2008. The new report supplements previously released information about the crash, and includes a transcript of the accident aircraft's Cockpit Voice Recorder (CVR). Among the factual findings from examination of the wreckage: the aircraft's elevator trim cables were reversed.

The accident happened just after noon on September 1, 2008, shortly after the aircraft (registration number N587X) had departed from Rickenbacker International Airport (LCK), south of Columbus, Ohio, en route to Mansfield, Ohio. The aircraft impacted terrain minutes after takeoff as it was attempting to return to LCK. The aircraft was completely destroyed, and all three crew members on board were fatally injured.

The new NTSB Preliminary report about the Air Tahoma CV-580 accident says that "the accident flight was the first flight following a maintenance Phase 1 and Phase 2 check, which included flight control cable rigging as part of the check. The flight was also intended to provide cockpit familiarization for the first officer and the observer, and a training flight for the first officer." The captain was a CV-580 Check Airman for employees of Air Tahoma Inc.

Possibly the most salient finding, arising from inspection of the wreckage: "The on-site inspection of the accident airplane revealed that the elevator trim cables were reversed. As a result, when the pilot applied nose-up trim, the elevator trim system actually applied nose-down trim."

The CVR transcript, included in the new report, indicates that both pilots struggled intensely, but unsuccessfully, to achieve nose-up trim in the moments before impact. At several points the CVR transcript notes "sound similar to the trim wheel motion" recorded by the Cockpit Area Microphone, until the captain declares, "there's nothing anymore on the trim." The pilots' dramatic struggle to control the aircraft proceeded for another minute and seventeen seconds, until the aircraft impacted the ground.

By the way, the accident flight was not recorded by the Flight Data Recorder (FDR). The NTSB report says:
The accident airplane was equipped with a switch in the cockpit to provide power to the FDR. Selection of the FDR switch was a checklist item that required the pilots to select the FDR switch to ON.

The CVR tape indicated that the pilots skipped over the checklist item that called for the FDR switch to be selected to the ON position. The CVR recording indicated that there was no discussion between the pilots concerning the FDR switch, whether it should be in the ON or OFF position.

The panel that contained the FDR switch was not located in the wreckage.
The investigation is ongoing.

Here is the link to the Preliminary Report: NTSB ID: CHI08MA270