Paul Phelan/Cairns
New Zealand's Transport Accident Commission is probing whether paint on the radar-altimeter antennas may have degraded the performance of the ground-proximity warning system (GPWS) on an Ansett New Zealand Bombardier de Havilland Dash 8, which crashed at Palmerston North, New Zealand, in June 1995, with the loss of four lives.
The aircraft's GPWS gave a "terrain" voice warning 4.5s before impact, although the accident report says that prevailing aircraft configuration and terrain conditions should have triggered the warning 12.5s earlier.
"Research has shown that an average pilot-reaction time from hearing the GPWS warning to initiating a pull-up manoeuvre is 5.4s," says the report, which has called for Transport Canada "in conjunction with the aircraft manufacturers and the manufacturers of the GPWS and the radio altimeter", to determine why the GPWS did not operate to specification before the Dash 8 accident.
Transport Canada has expressed "serious concern", and is to work with de Havilland to review the certification of the GPWS installation in the Dash 8.
Since publication of the original report, it has been confirmed that both transmitting and receiving antennas were painted, despite having been stencilled "Do not paint". Senior New Zealand accident investigator Ron Chippendale has confirmed that the antennas "-were painted, and we have drawn that to the attention of Civil Aviation Authority, who have advised operators to be careful to make sure they aren't painted. The significance of that, we're still in the process of establishing."
Avionics engineers say that painting may not only affect propagation and reception, but could also conceal damage to antennas.
Source: Flight International
