Propeller recomendation for RV aerobatics

[morristull]

Gents.
I would like comment from you RV fliers out there who fly aerobatics regularly up to the limit of the capability and design of the RV7 and RV8 and have an inverted oil system fitted and a constant speed propellor.
Most CS propellors go to fine pitch and hence overspeed in the event of loss of oil pressure.
Do you ever get propellor surge or overspeed from loss of oil to the governor in any of the aerobatics flown in the RV like verticals or stall turns or inverted flight when using a starndard type Hartzell or MT or Whirlwind propellor?
Do you feel it necessary to fit an aerobatic constant speed propellor with appropriate governor that goes to coarse pitch in event of loss of oil pressure?
If so which propellor would you recommend?
Regards Morris Tull.
RV7 ready for paint and prop. Dubai.

[smokyray]

Morris,

I have flown positive G acro in all three of my RV's. My Four and current RVX both have FP props. My HR2 had a Hartzell (non aerobatic) C/S prop and no inverted oil. I never had a prop surge while maintaining positive G aerobatics. Even with a few "diversions" into 0 or negative G, the prop on my Rocket never faltered. I like 23 squared for aerobatics in most RV's, a great setting and it teaches energy management much better.

If I were you I would go with a lightweight composite Whirlwind or MT C/S if you really like acro. If Cross country, IFR, level flight and autopilot's are your bag with an occasional roll thrown in for good measure, go with a Hartzell BA.

Good Luck.

Smokey

[hendrik]

Check this thread: http://www.vansairforce.com/communit...ad.php?t=35265

[JonJay]

Originally Posted by hendrik

Check this thread: http://www.vansairforce.com/communit...ad.php?t=35265

Read post #55.

[smokyray]

Hendrik,
Good thread and input but I believe, unrelated. Both of those events occurred while in test phase or due to an anomaly from faulty parts, installation or otherwise, NOT while performing basic aerobatics.
In my humble experience (3000+ RV hours) I have never had a prop overspeed and if installed correctly and oil pressure maintained, you shouldn't either.

If it is a concern, then install a FP prop, simply put.

Smokey

http://www.youtube.com/watch?v=nplK5ZoUxu4
Bob Herendeen in his Glasair, no inverted oil system!

[RVjim]

Even with an inverted oil system, zero G maneuvers will cause the loss of engine oil pressure.
(Vertical maneuvers will also cause engine oil pressure loss unless you mount the inverted oil valve 15 degrees off of vertical on the firewall so the oil will be forced to be taken from the rear of the engine.)

The counterweighted blade CS propeller will go to high pitch (low RPM) with the loss of engine oil pressure. Low pitch protects the engine and propeller from overspeeding.

If you are planning on flying aerobatics most of the time, then a blade designed for maximum thrust at slow airspeeds would be appropriate. (An aerobatic propeller blade with a small loss in cruise speed.)
I haven't had any interest in this propeller, yet.

If you are planning on the all around use of your aircraft with occasional aerobatics, then a blade designed for maximum efficience in cruise would be appropriate. (A counterweighted blade cruise propeller with a small loss in vertical performance.)
I have a couple of these propellers being delivered to RV-8 customers at this time.

Jim Ayers
jim@lessdrag.com

[morristull]

Jim, Smoky.
Thanks for your wise advice. I researched the other threads including Kevin Hortons, I have the later Superior aluminium cold air induction and associated deep sump designed for aerobatics with the oil pickup located toward the front, this should elliminate the issue Kevin had on his engine with the oil flowing forward of the pickup.
I will modify my inverted oil valve to 15 degree slant on the firewall and also will do this to my Pitts.
It is clear that you only have to have one major overspeed and you are up for $20,000 repair bill so the extra $4000 for an aerobatic or counterweighted prop is good insurance.
I have had a look at the Moroso oil accumulators and they will provide additional safety margin, where exactly did you plumb it into the oil system?

To give my hollow constant speed crankshaft more margin of safety from separation from gyroscopic loads or damage from prop stike, I am keen for wood composite or carbon blades with thier significantly lower forces.
I am ok with slightly reduced cruise speed for the peace of mind doing aerobatics.
Jim, The counterweighted cruise blade prop you mentioned for RV8 customers, can you tell me the model please.
I look forward to meeting some of you guys at Oshkosh this year if you are there. Regarrds Morris.

[RVjim]

The aerobatic constant speed cruise propeller from MT Propeller:
for the (I)O-360 engine is a MTV-12-B-C/C183-59b.
for the (I)O-375 engine is a MTV-9-B-C/C183-50.

If Bart Lalond at Aerosport Power gets the counterweighted crankshaft going on the 375 engine, then the MTV-12-B-C/C183-59b propeller should work fine for this engine configuration.

Jim Ayers

[mdevans9]

Hi Morris,

I too was worried about protecting my engine during stall turns and during other negative manuevers that I may do (a pull-push humpty comes to mind, or just a few inverted turns for example). After talking with Neil McCleod, who is on this forum and has first-hand experience with this on his RV-7, I purchased an MTV-15-B-C/C-183-50 two-bladed composite prop and the appropriate PCU5000X governor. I have not flown yet, but based on his comments, I think I will be very happy with it. I chose the two-bladed model as several reviews/tests have shown the three-bladed model to be slower at cruise, and to have less vertical capability (sorry, do not have them handy, as this is from memory of research done several years ago).

Just to acknowledge the recent discussion on manuevering speed and control deflections, I respect the limitations and understand that an RV-7 is not a Pitts - with which I do have experience.

Best regards

[dav1111]

Originally Posted by morristull

Gents.
I would like comment from you RV fliers out there who fly aerobatics regularly. which propellor would you recommend?
Regards Morris Tull.
RV7 ready for paint and prop. Dubai.

Check out this thrend:

http://www.vansairforce.com/communit...highlight=avia

Best regards,