A

albertaflyer

Active Member
Hi,

Can someone please explain the difference between an aerobatic and a cross country c/s prop? isn't it just blade profile (type of blade used)?

Thanks,

Tony
 
One issue posted recently:

Aerobatic prop will move to the pitch to max when oil pressure is lost, such as an engine out at slow speed.
 
The concept

The concept as explained to me is for an aerobatic manouver when an engine might lose oil pressure, even for a few seconds, a standard prop would flatten its pitch and possibly overspeed the engine.

On a more cruisey type situation where for any reason you might lose oil pressure for a few seconds during a take-off situation an aerobatic prop could go full coarse pitch and kill your take-off horsepower.

This oil pressure loss could be from anything from a failed governor to a cracked governor oil line. The standard prop would get you a little more time & altitude before the engine starved for oil and give you possibly better options.

That is just what I was told. Your truth may vary.
 
On the Hartzell, the aerobatic prop is counterweighted so that loss of oil pressure during aerobatics (knife edge, 0 G, etc) will not overspeed the engine. These are essentially the same blades used on twin engine propellers that will feather upon loss of oil pressure. The blade pitch stop is set diferently between the two. With loss of oil pressure, the blades tend to move towards full coarse until they reach the pitch stop, and in the case of the twin, that's feathered.

The governors are different as well. On a "normal" prop, increasing governor pressure increases pitch, while decreasing pressure makes it go flat. The aerobatic/twin governors are the opposite.
 
So if the price was right would you consider and aerobatic over a cruise prop? The fact that it goes coarse on low oil pressure shouldn't be that big of a concern as long as your paying attention. Btw, thanks for the info.
 
"Weight" a minute...

Tony,
All of the above are correct. The biggest and most important difference between an Aerobatic and "Standard" C/S is weight. The counterweights add a significant amount of weight to the propeller and the nose of an RV. Unless you plan to fly your RV in competition aerobatics with negative G's, tail-slides or outside snaps (I recommend another aircraft if you do) Keep the nose light.

I'm on my third RV "type" (2 FP, one Hartzell) and perform aerobatics exclusively unless I need a short trip somewhere. I have found after flying MANY RV's that the light nose airplanes are by far the best aerobats. My Hartzell equipped Harmon Rocket was a nose heavy beast doing acro solo. My best so far is my very light nosed RVX with a Catto FP 2 blade.

If you can choose, go with the lightest most durable cost effective prop you can for the money. The Aerobatic props weigh more, cost more to overhaul and have more to inspect on your C.I. every year. FYI...

V/R
Smokey
 
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Acro prop

The 13" Van's spinner will not fit over the counterweights. Hartzell uses a 14" spinner. I decided not to install my Hartzell because of spinner to cowling clearance. My spinner would be 1 inch further aft than Van's which means you have to redo the cowl or have somebody make you a prop spacer. More weight there too. I've decided to use a regular prop and install an oil accumulator.
 
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