On Thursday, February 25, 2016 at 2:26:37 AM UTC-8, wrote:
About jet sustainers, it is not true to say that they are not cerified for aircraft use, the M+D (JS1) and PSR (Ventus) jets are EASA certified. As regards the need to be spun to high rpm to start - what is the issue there? Given that the turbines run at 75,000 to 100,000 rpm they have got to get up there somehow. The M+D jet is only spooled up to 8,000 rpm by the electric motor before the fuel system takes over (in two stages). 8000 rpm is nothing remarkable for an electric motor.

Lastly, we can't meaningfully judge the reliability of jets based on the experiences of pre-certification installations during the development stage - which includes all the JS1 installations prior to November 2015. My jet was installed under South African experimental type certificate. I think that the turbine and firmware are at or very close to the certification spec and so far I have had no failed starts out of 44 attempts.

In general I think that failures of all types of sustainer generally arise from ancillary components ( e.g. fuel pump, spark plugs, carburettor diaphragm etc) and electrical issues (e.g. relays, connections etc) and electric glider motors certainly have potential reliabilty vulnerabilities.

Ok, so what you are saying is that jets installed in the last 3 months are reliable. My experience has been that engine installation problems may take years - not months - to reveal themselves. This might be ok if you exercise due caution, primarily having a landable field within easy reach. Jets do have the advantage that they are low vibration, an issue with a reciprocating piston engine (I really like my Wankel for this reason). On the down side, they consume a lot of fuel.

Tom