After the ignition switch is turned ON, my Captain always increases the RPM (throttle) very slowly. I don't know why, because our helicopter has an ECU. One day, my Captain asked me "Do you know why we increase RPM slowly?" so I answered "umm, to prevent a hot start?" Then my captain said "Nope. It is related to ENG OIL PRESSURE."

Is there any other reason about this slow operation (related to ENG oil pressure)?

Maybe compressor stall or surge?

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    $\begingroup$ Related: why-should-jet-engine-throttles-be-moved-smoothly? $\endgroup$ Mar 7, 2020 at 15:55
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    $\begingroup$ Is there some reason why you decided to drop the subject with your captain and come here instead? $\endgroup$ Mar 7, 2020 at 16:13
  • $\begingroup$ @Peter Kämpf I read that article already. but i can;t found any relation about ENG oil pressure,,, $\endgroup$
    – PilotK
    Mar 8, 2020 at 5:17
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    $\begingroup$ @Michael Hall because,,, captain set me a task,,, $\endgroup$
    – PilotK
    Mar 8, 2020 at 5:19
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    $\begingroup$ Yes, you are right, there is no mention of oil pressure in the other answer. Pump pressure goes up with RPM and lubrication demands of bearings do as well. Since there is a delay in pressure buildup, spooling up slowly minimizes the oil pressure lag. That would be my answer. $\endgroup$ Mar 8, 2020 at 9:37

2 Answers 2


he probably wanted to make sure the oil pump keeps up with the engine and bearings won't run hot, or that the oil circuit gets primed. turboshaft engines dont like it when running at idle, they tend to overheat; so it better be written somewhere that the engine rpm should be brought up slowly.

is important that whatever procedure, it comes out of the book. I would have expected your captain to direct you to startup procedure then mention the reason, so you could look it up rather than learn it by hearsay.


Well I hope he gave more of an answer than what you quoted above.

But it is indeed to do with oil - if you advance the throttle too fast, there is the potential for the engine's demand for oil to outstrip the oil pump/circuit's ability to provide it while things are still warming and spooling up. It's unlikely to immediately end in a catastrophic failure, but bearings and the engine itself will not be being lubricated and cooled appropriately for a period of time until the oil does catch up, which decreases service life of parts, and increases the possibility of something going wrong later.

This is really not much different to any other kind of engine, such as automotive - you don't really need to warm up a modern car, but you shouldn't thrash it in the first few minutes either, or again the demand for oil may exceed the oil system's ability to provide it.


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