Originally Posted by
alf5071h
what next - FAR 25, thank-you.
Thence if an alerting system was fitted, was it functional, was it adhered to ?
I recall that it was suspected that the Helios 737 audio alert was mistaken for overspeed - warning horn.
On the Helios flight it was confusion between the takeoff config horn and the cabin alt warning horn (which were identical as they used the same horn), coupled with the fact that in the 737 Classic a secondary symptom of excessive cabin altitude was the EFIS instruments (EADI and EHSI) going monochrome as the thinner air failed to cool the avionics effectively.
The already hypoxic crew were trouble shooting entirely irrelevant problems; hence why afterwards Boeing installed lights to indicate which warning was going off.
I have not flown the Classic for a long time, it was an absolutely marvellous machine, but it could be very very unforgiving compared to more modern aircraft. That said, hypoxia is one of the biggest threats we face, not least as the condition itself can interfere with your ability to realise you are in difficulty.