A definitive statement.
One of the perpetual discussions amongst R44 pilots (or at least those I talk to) is how awkward the Raven II can be to start if has been recently shut down – referred to as a “hot start”. Most R44 pilots have come from the R22, which does not have a fuel injected variant; so the starting procedure is somewhat different (although the R44 Raven is the same) – and even following the procedure in the Pilots Operating Handbook will not always result in an easy start if the machine has recently been shut down.
Doing a quick search on Google for the problem results in at least 5 different starting scenario’s, all different – yet all are claimed to be successful. The thing is you have to be very careful when dealing with failed starting attempts because if you are not then you will end up damaging the starter ring gear – to which end the aircraft I use has the following terms in its Self Fly Hire Agreement:
To protect the R44 starter ring-gear from damage on engagement due to rotation of the starter motor gear, the pilot will wait a minimum of 10 seconds after any attempted engine start before attempting to start the engine again. After 3 failed starts, the pilot will wait a minimum of 3 minutes for the starter motor to cool before attempting a restart.
The PoH even has starting tips; but none of them deal with the specific situation of a hot start. Well, in this quarters Robinson News (a four page flyer sent to Robinson owners / safety course attendees worldwide), RHC have finally addressed the issue. Of course, anything printed from RHC is classed as a definitive statement!
It turns out that the poor hot start performance of the Raven 2 is caused, typically, by the fact the resultant heat in the engine compartment causes fuel in the fuel lines to vapourize – and thus there is none to start the engine with again. Robinsons advice for improved hot starts is:
Pull the mixture control knob full out.
With master switch on, activate the aux fuel pump by turning key to “prime” for 20-30 seconds.
Then proceed with normal start.
Their reasoning for the prime with the mixture out (and thus not really priming) is that since the mixture is at idle cutoff the aux fuel pump will draw cooler fuel from the main fuel tank and pump the hot fuel in the lines through the fuel return line back into the fuel tank instead of the engine. A scan of RHC’s actual advice is here.
It makes sense when you think about it – hope this helps fellow pilots who’ve had trouble hot starting Raven IIs, especially in hotter climates than the sunny United Kingdom!