MMmmm .....
......
how would going to manual on the 139 increase the ITT? ....
Quite simply .... unlike the 412, when going into manual requires the retardation of the affected engines throttle prior to 'flipping' the switch ... with the 139 if the Gov. switch is inadvertently switched to manual the EEC 'Freezes' the engine power setting commanded at the time the switch is selected.
If this is not noted and the collective is then reduced the good engine will drop its output and the naughty engine will/may overspeed/overtemp ??
It may be ... that because of the 2 chaps flying were possibly doing a check flight ... that they might have in fact been doing a 'Simulated Governor Failure' sequence and found out the hard way how very sensitive the manual Gov. 'beep' adjust is to operate .... and unlike the 412 the beep is operated in 'shots' rather than as a continuous 'beep up/down' ..... it can all go wrong so very quickly!
