This local copy interesting article by Mike Busch makes the point that following a turbo failure you can get a total engine stoppage, due to the mixture being too rich to ignite at all, and this has caused some fatal accidents where the pilots did not realise this.
I recall talking to one aircraft salesman, of the long-gone Air Touring, who told me that if the TB21 turbo fails, you just carry on without the turbo as if nothing happened. I suspect a lot of people think they just lose MP but if the engine stops completely it may not be obvious among the panic that you need to lean pretty aggressively to restart it.
In the APS engine course, the mixture sweep ( from Rich to lean and back) was shown as a powerful tool for engine diagnosis. After loosing a turbo at FL200, going full Rich is not going to solve the problem. If the air intake is suddenly restricted, you will need a much leaner mixture to keep the engine running.
Interesting stuff, I experienced a defective wastegate controller right after take-off, the wastegate opened bypassing the turbo, and I lost around 10 inches of MAP. I was light and at my home base on a cool spring day zo it was relatively harmless. Full power and full rich, but the engine kept running smoothly.
Bobo wrote:
Interesting stuff, I experienced a defective wastegate controller right after take-off, the wastegate opened bypassing the turbo, and I lost around 10 inches of MAP. I was light and at my home base on a cool spring day zo it was relatively harmless. Full power and full rich, but the engine kept running smoothly.
But the situation is completely different at high altitude…
That is a very important hint, many thanks for that. My POH gives no instructions for this case.
This summer we had very high temperatures, I remember a flight at FL150 with an OAT at 0°C. In order to keep the engine power I had to advance the throttle further than usual. I had never experianced that. I wondered if it was a problem with the TC or if the temperature was the cause. Since all engine temperatures and the FF where normal I decided to continue the flight and everything went normal while looking for the next airport.
In the APS engine course, the mixture sweep ( from Rich to lean and back) was shown as a powerful tool for engine diagnosis.
In the case of a TC failure it makes more sense to go from lean to rich until the engine – hopefully – starts.
Sir_Percy wrote:
In the case of a TC failure it makes more sense to go from lean to rich until the engine – hopefully – starts.
Depends on altitude – I doubt you can start engine full rich at FL250.
I propably was not precise enough. I meant go to full lean (asap to not flood the engine and exhaust), then gradually enrich until the engine starts.
It is also very likely that you won‘t be able to do a restart before you are below a certain altitude.
If you had an an engine stoppage out of other reasons the turbo might have run down and you won‘t get it
restarted as well before being back in denser air.
But the situation is completely different at high altitude…
Yes it is. I had a wastgate controller failure at FL150 with a stuck wastegate. The big problem is you get a massive overboost on descent. So you have to reduce to idle, which is not idle.
So the waste gate was stuck in the closed position. I understand that there is a simple spring operated overboost valve that pops open in the event that the engine receives to much boost, at least in the conti TSIO360.
