Variable pitch prop problems

[MikeR]

I just flew my recently purchased RV-4. WOW! What a rush! I am, however, having a problem with the variable pitch prop. (Hartzell hydraulic on an IO-320). At minimum pitch, it's able to turn 3000rpm. Is there an adjustment to scale it back to 2700? Thanks for all the help.

Mike

[Mel]

There are basically 2 adjustments. One is the governor itself and the other is the low pitch stop on the prop. Both should be adjusted by a qualified prop shop.

[Ted Radclyffe]

Mike,
I am not close to my prop manual at present but I changed the pitch setting without any trouble, base on the manual. I was only pulling 2500 at full throttle.
The adjustment is in the center of the prop and is an Allen keyed screw with a locknut round it. So a ring spanner and suitable Allen key is all that is required.

The clue is to mark the original setting so that you can get back to it if all goes wrong. The adjustment I seem to remember is about 50 revs for 1/4 turn. I seem to remember that I could see the blade angle change.

There is a warning (though I can't remember where I read it) not to jigger round with the govenor to effect a better pitch on take off.

There is also a belief that the prop pitch adjustment shouldn't be touched unless absolutely necessary as it is factory set, but my technical guru insisted that the prop should turn at 2600 at full throttle (based on his wealth of experience an another similar aircraft with an O-320 on the day). I did as asked and when fining the pitch got a slight govenor hunt. So found a good compromise. Your problem is the reverse but the adjustment is the same principle.

No doubt there will be many other replies which will give more accurate information.

Don't be daunted, it is no big deal provided you mark your starting point and only move the adjustment in small increments.

Ted
RV-6A "Rough Red"

[MikeR]

Do you remember which way to adjust it?

[flyeyes]

Before you do anything, I would check with an optical tach to make sure it's really turning 3000.

Another thing to check is the part number of the governor and make sure it's appropriate for your engine. It's my understanding that there are at least a couple of different possible drive ratios, and if you have the wrong governor it could let the prop turn either too fast or too slow.

[cropduster]

After verifying that your tach is accurate, adjust your governor to max RPM first. If you reset pitch stop first your governor will cause prop to hit stop which can cause damage. Your pitch stop should be set above governor and is designed to catch prop if governor fails.
barryb

[Dale Ensing]

Contact Hartzell for Propeller Owner's Manual and logbook No.115N
Manual has instruction for adjusting and maintain the prop.
phone 937 778-4200

[Wes Hays]

Hartzell POM and Logbook gives the instructions for the low pitch stop adjustment on page 403, 404, and 405 under Testing and Troubleshooting. It specifically states that RPM adjustments must be made with reference to a calibrated tachometer.

I had to tweak mine and it really wasn't that big a deal as long as you follow the instructions in the manual.

C.(1)(a) states "Loosen the jam nut while holding the low pitch stop with an allen wrench to prevent the low pitch stop from turning as the jam nut is loosened. Turning the low pitch stop IN will increase blade pitch to reduce RPM, and turning the lowpitch stop OUT will lower blade pitch and increase RPM." In addition, "Turning the stop 3/4 of a turn will change the blade pitch of approximately one degree. One degree of blade pitch will change engine RPM by approximately 140-150 RPM. One full revolution is equal to approximately 200 RPM."

Please consult the Hartzell Manual, follow the instructions, and you should be fine. I think the main thing is to know that your tach is giving you the correct reading. The props usually are not off that much.