CS Propeller "high RPM !"

[Pilottonny]

Hi guys. I have a Whirlwind 200 RV propeller and an MT govornour on my 164 HP IOX-320. At take off I can only push the throttle in very slowly otherwise the Dynon EMS starts shouting "RPM High!". Ones in flight I get max. 2.690 RPM.

It feels like I am already airborne before I can reach full throttle without overspeeding the propeller (have managed to stay below 2.750 RPM).
Is there a proper technique or setting to avoid this, or is it normal?

Regards, Tony.

[Andy Hill]

If it was a Hartzell, I would say read the Manual again and set the 'Fine Pitch Stop' - many (including us!) do not, and get (got) a similar problem. I suspect the Whirlwind is the same?

In essence you are adjusting the Fine Pitch position of the blades, such that 'Static RPM' is at (or less than) Max Engine RPM. This depends on your engine HP, so the Prop Manufacturer cannot set it for you (unlike the Governor).

Personally, on an over-powered RV, unless you need absolute Max Takeoff Performance, I would be happy with the Static RPM at 2600-2650 RPM. This will reduce overspeeding in a headwind on takeoff / on touch-and-go landings etc. Your only loss of HP would be when IAS is 20K or less i.e. not very often

Andy
RV-8 G-HILZ

PS Read the Engine/Prop docs about over-speeding - engine almost certainly is good for 10% (2970RPM!) for 3s, prop same or more. Not suggesting you plan to do this, but it is there, and might be better to use it than spend the takeoff run watching/fiddling with the RPM!

[Pilottonny]

Andy,

Are you suggesting I take the propeller hub appart to adjust the stops of the blades, inside??? Ouch!!

I assume that it will take less time for the prop to go from partially fine to climb-pitch, than from fully fine to climb-pitch, so it will be at the right setting quicker and will not overspeed that easily, right? If that is the case, Whrlwind should have set it for an O-320 engine before they shipped the propeller, because that is what I ordered it for and not for anything else.

OK, with regards to setting the max. RPM to a lower setting, I can adjust the high RPM by just pulling the blue knob out a little bit and see what happens. If that makes a difference, maybe I should adjust the high RPM screw. But..... if the engine does not make max RPM (2.700), it is not going to make max power and that is what you want on take-off and climb, right?.

Regards, Tonny.

[Andy Hill]

Tonny

Are you suggesting I take the propeller hub appart to adjust the stops of the blades, inside??? Ouch!!

No... I suggested

I would say read the Manual again

On the Hartzell, to adjust the FPS you take the spinner off, undo a lock nut, and turn an adjusting bolt with an Allen Key. 10mins.

If that is the case, Whrlwind should have set it for an O-320 engine before they shipped the propeller, because that is what I ordered it for and not for anything else.

Please re-read my post. It has to be setup for your exact engine. An "O-320" can vary between, say, 140HP (because it is shagged) and 180HP (lots of fancy extras / luck).

Your last paragraph shows you are not understanding the fundamental point. On the start of takeoff, the prop will be in fine pitch. You advance the throttle quickly, and the RPM increases rapidly. The governor cannot act quickly enough to adjust the blades to stop that increase at 2700 - so RPM overshoots (as you observe) and then returns to ~2700.

By "coarsening" the FPS you ensure the RPM will not exceed 2700 at nil/low airspeed. This then gives the governor a chance to control the RPM as you accelerate IAS (which it should do).

All my thoughts are to do with the Hartzell prop. But any VP prop essentially works the same way... and if you cannot (easily) adjust the FPS, then you have a problem that requires a better governor than most of us have!

Andy

[Steve Sampson]

Tony, let me try.

You have an MT governor and a Whirlwind prop.

Section 5.5 and 5.6b of the MT manual cover the issue you are talking about wrt to the governor. I know nothing of your prop.

I am with Andy. Clearly the governor is easily able to govern the prop, from what you say to 2680 in flight, but the blades are set just too fine to start with. This is what the sections above (and common sense) indicate.

The answer as Andy has said, lies in having the fine setting of the Whirlwind a little less fine. DO NOT ADJUST THE GOVERNOR!

The most I see on takeoff is about 2680rpm when I look at the AFS download. When the oil is already hot from a recent flight it probably controls to perhaps 2670. I put this down to the oil being warmer and the response quicker.

I presume you warm the engine up and cycle the prop before first takeoff?

Perhaps as a next step you should say to Whirlwind "The fine pitch is too fine to control the static rpm. What do I do?"

[Pilottonny]

I run the engine up to about 50?C oil temp. before take-off and cycle the prop twice. Even doing touch en goes (warm engine) it occurs, so that is not the problem.

The Whirlwind must be different to the Hartzell. I d not recall any setting-screws or bolts on the Propeller hub, appart from the cover attach screws. But, I will read the manual and see if it mentions anything that I can/should set.

Otherwise I will have to ask Whirlwind.

Anyway, after another 5 hours I will have the prop balanced, maybe they can do the setting of the fine pitch stop as well.

Thanks for the input, regards, Tonny.

[Andy Hill]

Tonny

There are 2 ways you can set the FPS... either, as per the manual, running engine to full power whilst tied down, shut down, adjust FPS, do again until it is <2700RPM. That takes some bravery and I cannot see as "good" for the aircraft / has potential for problems.

Alternative, once you work out how to do it, it fly it, see Max RPM, adjust after FPS flight, recheck next flight etc.

Andy

[RVjim]

Hi Tonny,

Andy provided the static RPM setting for the low pitch stop as 2600 to 2650 RPM. This is a "safrty of flight" issue, and is very important.

Like Andy said, refer to the whirlwind manual to adjust the low pitch stop.

I don't know the current whirlwind propellers, but I have disassembled a 4 blade Whirlwind propeller. The hub design was similar to the MT Propeller.

On the MT propeller the low pich stop is on the outside of the hub at the center of the front cover. There are two nuts safety wired together on a threaded aluminum shaft.

You'll need to remove the spinner dome and any filler plates behind the blades to make this adjustment. (Normally, dynamic balancing is done with the spinner dome installed, so don't expect the low pitch stop to be adjusted as part of their normal operation.)

Remove the safety wire between the two nuts. Use an open end wrench to hold the bottom nut and loosen the top nut. (The MT Propeller torque for these nuts is 90 to 100 foot pounds. So just trying to loosen the top nut could possible damage the threaded aluminum shaft.) (Also, I ground my 1 1/4" open end wrench thinner so it was the same thickness as the nut.)

After adjusting the bottom nut, torque the top nut (to Whirlwinds spec.), and do another static runup.

You want to see 2600 to 2650 RPM at full throttle.
So use the normal precautions for your runup tests.

Regards,
Jim Ayers

[DakotaHawk]

I don't have the Hartzell Prop manual, but I understand your point about setting the low pitch stop on the face of the Hartzell C/S prop hub.

Question: After loosening the locknut on the prop hub, does the hex screw turn CW or CCW to make the pitch coarser? Any rule-of-thumb for ratio of turns on the hex / 25 rpm change? In a perfect world, it would be great to make one adjustment and find that I set my low pitch perfectly for about 2670ish RPM!

Thanks for clearing up the differences between the governor stops and the low pitch stops on the prop itself.

[Bavafa]

Scott
Turning the low pitch 1 full turn will result in 250 RPM in a feathering prop (2/3 of a turn will result in about 150 RPM) Turing it IN will reduce the RPM and Turing it OUT will increase the RPM.

Andy is exactly right with his comment/procedure. You will need to set the static stops first and then adjust the governor. One easy way to adjust the governor is to go for a flight and adjust it with the blue knob in such way that with full power during a go-around your MAX RPM is not pass the desired RPM (2700) and then do not tough the knob till you have landed. Then set the stop screw at that point to where the knob is.

Hope this makes sense.