Recommendation follows accident report, but manufacturers may fit systems voluntarily
Major US helicopter manufacturers may be moving toward voluntary fitment of terrain awareness and warning systems (TAWS) in new-build turbine helicopters, says US Federal Aviation Administration helicopter directorate manager David Downey.
This revelation comes as a US National Transportation Safety Board (NTSB) report recommends that the FAA should mandate TAWS in helicopters that carry six passengers or more.
The recommendation follows the NTSB investigation into a 23 March 2004 Era Aviation Sikorsky S-76A crash in the Gulf of Mexico. The NTSB says the event could have been avoided if the helicopter had been fitted with TAWS.
At the same time the NTSB is calling for flight data recorders (FDR) to be made compulsory on some helicopter categories that are exempted at present, including the S-76.
The helicopter that crashed was carrying two pilots and eight passengers on a night flight to an oil-drilling ship in the Gulf of Mexico. The NTSB has found that the helicopter descended into the sea because of “the crew’s failure to identify and arrest the aircraft’s descent for undetermined reasons which resulted in controlled flight into the water”. Everybody on board was killed.
Night visual meteorological conditions prevailed at the time of the accident, reports the NTSB, adding that if the aircraft had been fitted with TAWS the crew would have had adequate warning of the helicopter’s descent, which was clearly inadvertent.
The board notes that when the FAA mandated TAWS in fixed-wing passenger transport aircraft in 2000 there was not yet a version of the warning system appropriate for helicopters, but now there is.
In its report the NTSB has also emphasised its disagreement with the FAA’s 2003 decision to exempt the “S-76A and several other helicopter models from its requirement that they be fitted with FDRs”.
The FAA had claimed it was not in the public interest, but the NTSB has now compared the Era Aviation accident investigation – there was no FDR – with the ongoing probe into the 10 August 2005 S-76 crash in Estonia.
The FDR in the Estonian case rapidly yielded critical information: there had been “an uncommanded extension of the forward main rotor control actuator and the unit was not responding properly to pilot inputs”, says the NTSB. This enabled all operators and the manufacturer to be alerted.
DAVID LEARMOUNT / LONDON
Source: Flight International
