I just found the reference in the manual..P9.No minimum RPM stated.
CAUTION
Avoid RPM during cruise below 2300min –1!
On Wednesday, 17 October 2018, 9:19:12 am AEDT, Laurie Hoffman via dog
<[email protected]> wrote:
There's a requirement in the manual not to cruise between 2000-2300 rpm (I'm
pretty sure this is the nominated range).I understand its a harmonics issue.
Jarek if you intend to remain in the thermal I'd suggest that you incrementally
reduce the throttle and CHT back to the point where you believe the prop is not
generating drag (near but not to idle and dependent on pitch setting).
After all if the thermal or wave strength is sufficient to soar, maybe
somewhere above 230-250fpm, why not save fuel and engine wear? Ideally switch
off altogether once the CHT is low enough. The H36 soars better than just about
any other TMG.
Sent from Yahoo7 Mail on Android
On Wed, 17 Oct 2018 at 8:39 am, Michael Stockhill<[email protected]> wrote:
Others will have other thoughts, but effectively, with any fixed pitch
propeller, its maximum rpm at full throttle will follow airspeed. If you left
the prop in low pitch and leveled off and let the bird accelerate without
reducing throttle, the rpm would readily exceed maximum redline rpm.
Similarly, with the propeller in cruise pitch, its rpm will also follow
airspeed. Slowing from cruise airspeed to thermalling speed will also reduce
rpm. At the extreme, if these propeller had much more pitch or bite, rpm at
climb could be significantly less that what you are seeing. Think of a bicycle
kept in the wrong gear. But extreme pitch would be unusable in anything other
than level flight. Does it matter that your rpm drops to 2200? I see that
frequently at reduced airspeeds especially at high altitudes where the engine
produces less power. After 16 years, I would say it is not a factor, and it is
improbable that you will harm the engine. If you could fly at an airspeed
significantly less than stall speed, maximum rpm with cruise pitch would be
even less. You might do a static runup before your next takeoff with the pitch
in cruise position to discover the minimum/maximum anticipated full throttle
rpm. If you ever inadvertenly try a takeoff with the prop in cruise pitch
position, you will likely see rpm of 2000-2200 as you accelerate to liftoff
speed.
On Tue, Oct 16, 2018 at 2:20 PM Jarek Steliga <[email protected]> wrote:
Hello,
When trying to thermal with engine running and propeller in cruise position, I
noticed that the recommended RPMs of ca 2400, drop with airspeed even as low as
2200. Is this harmful to the engine and should be avoided?
Best regardsJarek
