Best propeller for short take off

Hi,

I have a short grass runway in France and it is shorter in Winter...
So I would like to know what is the best propeller for the shortest TO.
Constant speed of course.
2 or 3 blades ?
72 or 74" ?

I plan to install an IO375 ( 195 HP) from aerosport power.

Any suggestions ?
In advance thank you

SIncerely
Sylvain

We have done a lot of propeller testing over the years. If c/s, static thrust, and short field is the driving force, the Hartzell 2 blade composite G2YR/N7605W-2X showed a significant improvement in static thrust and take off distance over the other Hartzell, MT, and Wirlwinds. Takeoff distances reduced by at least 100' in all cases that I remember. In fact, the cord on the blade is so big, and the bite so hard, that they went to a G hub, slightly longer hub, so that the wide cord blade would not hit the cowl. Its takes a huge bite. Being composite, the spin up, to bite, to launch off the brakes quite exhilarating.

Thank you Kahuna for your reply. Do you think the Hartzel is better than the 74RV Whirlwind ?

Im not sure what the static thrust numbers are on the 74RV. And with complete tear down inspections required every 650 hours, Id not put one on my plane to try it.

Hi Sylvain

As Kahuna says, the composite Hartzell gives a significant increase in static / low speed thrust - yet with little performance loss at the high speed end (unlike the 3 blade MT).

I would comment though that:

1. For a short strip and an RV, getting out is easy - the more difficult aspect is getting back in!
2. The composite Hartzell (also the 3 blade MT) are good here for drag, but that drag needs to be handled carefully
3. I am not familiar with the G Hub, but an RV-7 (wider cowling) with James cowl (intakes sticking forward) is not the ideal starting point for the composite Hartzell - I suggest you check carefully it will be clear.

No experience of the Whirlwind, in the UK it is almost impossible to get an uncertified C/S prop cleared for use...

Andy Hill said:

Hi Sylvain

As Kahuna says, the composite Hartzell gives a significant increase in static / low speed thrust - yet with little performance loss at the high speed end (unlike the 3 blade MT).

I would comment though that:

1. For a short strip and an RV, getting out is easy - the more difficult aspect is getting back in!
2. The composite Hartzell (also the 3 blade MT) are good here for drag, but that drag needs to be handled carefully
3. I am not familiar with the G Hub, but an RV-7 (wider cowling) with James cowl (intakes sticking forward) is not the ideal starting point for the composite Hartzell - I suggest you check carefully it will be clear.

No experience of the Whirlwind, in the UK it is almost impossible to get an uncertified C/S prop cleared for use...

Click to expand...

The Hartzell composite will NOT CLEAR the James Cowl at full pitch. It is a zero clearance on mine with the 2.5" sabre spacer. If you are interested in fitting this prop, let me know and I will dig out the dimensions. Basically, the cowl needs to be moved aft by 5/8" and then the ring behind the spinner extended forward by the same. Since the the engine in the 7 is not straight, it will be the right side that is worst. The air inlet (combustion, not cooling) has adequate clearance. I do not have the G hub.

PM me if you need better dimensions.

That is a good point though, about a c/s prop helping with short field landings too. Full forward with the prop control and throttled back to single digit manifold pressures and RV's come down at easily controllable speeds and very useful descent rates for short field landings. A little power to stop the descent rate is but a small forward throttle push away.

With 195hp, even with the standard aluminum Hartzell blended airfoil constant speed prop, such an RV-7 will feel like a race car with nitrous oxide injection on takeoff.

Glad I was on here today to take in this info, I had no Idea about the James cowl and full pitch on particular blades. Eye opener for sure!

BillL said:

The Hartzell composite will NOT CLEAR the James Cowl at full pitch. It is a zero clearance on mine with the 2.5" sabre spacer. If you are interested in fitting this prop, let me know and I will dig out the dimensions. Basically, the cowl needs to be moved aft by 5/8" and then the ring behind the spinner extended forward by the same. Since the the engine in the 7 is not straight, it will be the right side that is worst. The air inlet (combustion, not cooling) has adequate clearance. I do not have the G hub.

PM me if you need better dimensions.

Click to expand...

You can get the Hartz composite blades on an extended hub for a SJ cowl. We have one.

More Info on the SJ cowl with the Hartz prop please?

I have the SJ cowl already but have not ordered my engine and prop. I was leaning towards the 3-blade MT, but this thread now has me re-thinking. Is there someone I can PM for more info?

FYI, plane is RV-8, engine will likely be near 200hp IO-360 based (titan or aerosport), will need to occasionally get in and out of a 1300' grass strip.

Thanks.
pdj

Glad I was on here today to take in this info, I had no Idea about the James cowl and full pitch on particular blades. Eye opener for sure!

Click to expand...

You can get the Hartz composite blades on an extended hub for a SJ cowl. We have one.

Click to expand...

Just adding some info here... Prior the 'G' hub, Hartzell learned to limit the coarse pitch stop on the composite prop to avoid standard RV cowls. "Standard" being difficult to define, since each RV varies somewhat

We used the Hartzell stop on standard cowl RV-8s, but took a small amount off the cowl edge to get a reasonable clearance (1/4"?).

Kahuna likely has more details, but the G hub should allow the coarse stop back to a more typical value. Now adding a SJ cowl may require that stop adjusted again?

A consequence of the altered coarse pitch stop is you can lose governing at high TAS e.g. high altitude / low RPM setting (start of descent) you are on the coarse pitch stop. We require initial and periodic VNE checks at 200KIAS (leave out VNE v TAS!), and if you do the check above ~5000' then full power will go past 2700RPM.

Not intended to discourage anyone from the composite prop - it is fantastic - but the above might give some background to "why" the G hub, and possible remaining SJ cowl issues, and solutions.

Kahuna said:

You can get the Hartz composite blades on an extended hub for a SJ cowl. We have one.

Click to expand...

When I purchased, the G hub also needed the Hartzell spinner (not Vans) to match the standard cowl and the extended hub was limited to 4G aerobatics. Is this still the case for both?

I was not aware of the actual clearance dimension (zero) until I measured it. Now, having the measurements, it is easy to check just by measuring the cowl R/S air inlet setback from the spinner ring. The cowl needs to be set back (as measured at the right cooling inlet) by the clearance desired. My SJ cowl (extended) had the spinner ring even with the forward edges of the cooling air inlets.

Here is the model # of the Hartzell 2 blade composite on a hub that fits the SJ cowl.
HC-M2YR-1NWX/N7605WX/SM8
You can check with Hartzell on any restrictions.

I have the Hartzell and Aerosport combo in my RV-7. It is the only RV with a CSP that I have flown in. That being said, it is a truly capable plane. Even if I roll the throttle on in a smooth manner, the plane is off the ground in only a few hundred feet. Basically by the time I get the tail up. The thing that surprises me is how short a landing I normally make without trying. I am a newb TW guy and flying a normal approach at 80mph, I still have to give it a little gas sometimes just to get to the first turnoff without jamming everyone up behind me. This has nothing to do with my skill level. The plane just lands and stops. I'm not really sure why because I am not using the brakes until I need to turn off, and I fly it to the numbers 5mph faster than I ever flew a Skyhawk. I guess it might be the lack of float in relative terms.

Incidentally, when I flew the plane home from the builder's hangar, I flew at 23" and what ever I could get out of the throttle. I burned 8.4'ish gph at 202 TAS, ROP.

OK guys, thank you for your replies. Will, from James Aircraft advised me about CS propeller : "The forward injected (cold air sump) cowl has to be used along with a 2.5" propeller extension for a constant speed propeller".

My runway is 300 meters long in winter, so I think it is enough with any CS propeller and 195 HP.

I think I'll keep my Whirl Wind choice : lighter than a Hartzell and cheaper than a MT propeller.

My definitive choice will be between the 200RV or the 74RV. Any advise about it ?

Sylvain