We have a 2001 EC120 that has an extremely irritating, intermittent starting problem.
FCU at 22 degrees, pump 30 secs, voltage > 25v. Activate starter, T4 rises to around 700 degrees, Ng typically climbs slowly to somewhere around 36% when the engine just stops accelerating. Tweaking the twist grip to nudge the red line (T4 800 degrees) sometimes helps, occasionally we have to go into the red, nudging 850-860 degrees for 3-4 seconds . When this happens, the engine accelerates again, but as soon as you throttle back to T4 < 800 degrees, the Ng droops and the engine stagnates again, typically at around 36%. A second attempt might be slightly better (faster initial acceleration), but the problem still exists. If a third attempt is necessary, the problem then is the exhausted battery (after the previous extended start attempts) and so a GPU is needed. But here's the thing... we only normally use the GPU after one of these failed starts and when we do, the start is often faultless, with Ng racing towards 50% in no time and T4 between 600 and 700 degrees
. If we use a GPU initially, the start will be better, not surprisingly, but we may still get the 'stagnation' problem. Using a GPU after one of these failed starts always gives the best start of all.
The aircraft has had a recently overhauled starter/gen, new FCU and new injector manifolds (which substantially improved power margins). It doesn't seem to matter if the engine is warm or cold, nor whether the ambient temperature is warm of cold. It has a particle seperator, but the problem persists whether this is removed or not.
We're stumped - any ideas anyone?