Old 20th Feb 2021, 17:17
  #6 (permalink)  
Join Date: Nov 2005
Location: Zulu Time Zone
Posts: 720
Originally Posted by Obs cop View Post
However, what happens if the prop is cycled (not suggesting it should be) whilst on the ground and the throttle is at idle? Will there be an increase in pitch and therefore a further drop in prop rpm or will the rpm remain the same?
The short answer is it remains the same because the rpm is below the governed range. Now, I don't know the range of every governor out there so I cannot definitively say what would happen if you tried it but I strongly suspect the answer holds good in general for piston singles. I am talking about idling with the throttle on the stops here circa 800 as opposed to the 1100 rpm that lyco recommend be set with throttle in order to avoid lead fouling. At 1100 you will see from the figures below that you might be at the minimum governed for some units so there is the potential for a little movement.

It stands to reason that the governor has a limited range and hence a minimum selectable rpm. We know redline rpm but the minimum selectable rpm is not information that the pilot needs to know so it is hard to find. Two examples are below, namely, 1100 and 1400. Note the 1400 figure results from reduction gearing so the engine revs in that case will be 1616. There is also an example where the minimum governed rpm is “NA”; that is simply because that unit is for the SR22-T which is a special case because it has only one single governed speed of 2500.

Last edited by oggers; 20th Feb 2021 at 17:28.
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