BO 105
Both engines start normally at sea level a/c flies to landing site 6000' and shuts down.
Return trip engine one starts normally, hit starter button engine two and number one engine stalls. Pilot and engineer exchange puzzled looks and try again. Same result as soon as starter button for two pressed number one engine stalls. A cursory inspection due to location performed with no obvious defects.
Another attempt made this time starting two first then one. No problems!!!
Aircraft returns to sea level and the problem disappears and is put down as altitude related although no obvious answer.
A couple of weeks later the problem reaccurs this time at sea level.
Investigation shows that the number one compressor casing is very badly erroded.
The penny drops.
Due to disturbed airflow the stall margin on one is reduced.
Normally starting one first is on battery and when stabilised generator is switched on prior to starting number two. The additional load on the number one generator caused by starting two caused a drop in N1 sufficient to drag the compressor in to the reduced stall band and induce the stall. This explains why there was no problem starting two first as the compressor was in a far better condition.
Moral of the story, if operating in a sandy environment minus sand filters keep a good eye on you compressor case errosion. Also dont ignore P.A checks!!!!!!!!!
Last edited by ericferret; 15th Feb 2013 at 13:31.