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Which CS prop for my O320 RV6

I

IO390

Member
Currently I have an Aymar Demuth 68" X 74" on my RV6. Engine is an O320 D2A.

Take off performance near max weight is OK, but a CS is too tempting to ignore.

My current max airspeed, at sea level and WOT is 165-167kt depending on temperature and weight. I'm told this is reasonably good for an O320 powered 6 so I'd like to avoid losing much top end.

The plane weighs 1000lb and I need more nose weight also. The propeller options are:

MTV-12-C/180-57 - MT 3 blade - 43lbs + governor

Hartzell C2YL-1BF/F7663-4 - 57lbs (I think) + governor

I keep reading that one will tend to lose a few knots with a MT prop. If I lost say 2-3 knots I wouldn't care, but say 7-10 knots would be annoying. I gather this is unlikely to happen with a 2 blade Hartzell.

Does anyone have experience with the MT on an O320? The benefits of the MT are lower weight and smooth running (plus it looks cool).

Obviously I'll have to be sure that the engine can take a CS prop. I know it has the governor drive pad, the correct nose bearings, hollow crank and the oil feed hole in the side of the case. The only thing I don't know yet is whether it has the oil cross tube in the crank, so I'll have to pull the crank plug and find out.

There is also a price difference, it's about $4000 more for the MT. The main annoyance of the Hartzell is that the one which is sold for the O320 is an old design, and the blended airfoil version is only for the 360 and up.

Any thoughts on the above? What would you do?
 
I’d take the 3 bladed MT anytime :)

Not only will you get shorter takeoff distances, but the climb, and the braking performance will improve. Also your ship will definitely be quieter, should you care about that ;)

Another plus is the field repair option… having ripped-away an inch of the leading edge, and cracked the tip of one blade (engine off) on mine (don’t ask how… never rush for a flight…) I thought I’d be grounded for a while… sent a description and pictures to MT Germany in the evening, received instructions and link to the field repair manual next morning. A couple of hours work later, and the repair is barely noticeable.

As you mentioned, a top speed loss for the -3/-6/-7/-8 of about 2-3 knots is to be expected. Another minus is being of wooden composite, I wouldn’t install one on a non-hangared airplane.

Another option which has been working pretty well for a few years now on the O-320 equipped -4 I built, is the electrical version of the same prop. The only difference in ops is a slightly slower pitch change, and the adjustment/replacement of the brushes on the maintenance side.
 
Dan 57 said:
I’d take the 3 bladed MT anytime :)

Not only will you get shorter takeoff distances, but the climb, and the braking performance will improve. Also your ship will definitely be quieter, should you care about that ;) ......
Click to expand...

Hey Dan. I am leaning towards MT, in fact my RV's stablemate is a Glastar with the exact same engine and the correct MT prop. I'd like to "borrow" it for testing purposes but the owner may not approve...

One concern is servicing costs and downtime. The Whirlwind looks interesting, I will call them for a price later. But their website says it's a 500hr interval between teardown - I'm in the UK so having to return a prop to the US every 500 hours is an absolute no go.
 
I have an RV-6 with a Whirlwind prop, I'm very pleased with it. My engine is different to yours so specifics don't read across but it is as light as an MT and as fast (or faster) than a Hartzell.
 
Southern Pete said:
I have an RV-6 with a Whirlwind prop, I'm very pleased with it. My engine is different to yours so specifics don't read across but it is as light as an MT and as fast (or faster) than a Hartzell.
Click to expand...


Pete, which Whirlwind do you have? I know some Whirlwinds are in service in the UK, so shouldn't be too much of a problem with LAA but I wonder what the support from Whirlwind is like in case of problems?

About to install G3X and servos also, so I'm expecting some downtime while the LAA approve the install...

Cheers, Sheldon
 
Here’s another vote for checking in to the Whirlwind 300 series - we’ve had one on our IO-320 powered RV-3 for close to a year now (and one on the O-360 RV-8 for a couple of years). I haven’t compared the performance to an MT, but comparing it to the latest Hartzell blade designs, the two were very close - and the WW was way cheaper.

I can’t tell you how support would be overseas, but if I were in your position, I’d at least send some emails and have a conversation with them.
 
I have a MTV-11-C Prop on my O-320-D2A engined RV9A and love it, great climb and cruise performance hope thats of help
 
I've phoned Whirlwind, the guy on the phone was helpful and confirmed they already have some 300 series props in service in the UK, and they have a UK service centre (proptech at lee on solent).

So the options are now (all costs without shipping):

- MT 3 blade: 16600 USD with governor, 40 week lead time

- Hartzell 2 blade from Vans: ~ 13000 USD with governor, 12 week lead time

- Whirlwind 300 3 blade: 15600 USD with governor, 8 week lead time

WW seems a good option then. I will see what the LAA say.
 
IO390 said:
Currently I have an Aymar Demuth 68" X 74" on my RV6. Engine is an O320 D2A.

Take off performance near max weight is OK, but a CS is too tempting to ignore.

My current max airspeed, at sea level and WOT is 165-167kt depending on temperature and weight. I'm told this is reasonably good for an O320 powered 6 so I'd like to avoid losing much top end.

The plane weighs 1000lb and I need more nose weight also. The propeller options are:

MTV-12-C/180-57 - MT 3 blade - 43lbs + governor

Hartzell C2YL-1BF/F7663-4 - 57lbs (I think) + governor

I keep reading that one will tend to lose a few knots with a MT prop. If I lost say 2-3 knots I wouldn't care, but say 7-10 knots would be annoying. I gather this is unlikely to happen with a 2 blade Hartzell.

Does anyone have experience with the MT on an O320? The benefits of the MT are lower weight and smooth running (plus it looks cool).

Obviously I'll have to be sure that the engine can take a CS prop. I know it has the governor drive pad, the correct nose bearings, hollow crank and the oil feed hole in the side of the case. The only thing I don't know yet is whether it has the oil cross tube in the crank, so I'll have to pull the crank plug and find out.

There is also a price difference, it's about $4000 more for the MT. The main annoyance of the Hartzell is that the one which is sold for the O320 is an old design, and the blended airfoil version is only for the 360 and up.

Any thoughts on the above? What would you do?
Click to expand...

I have the listed Hartzell prop on my RV-6. At sea level over the Pacific Ocean, I can get 175 KIAS with everything forward. I do not remember what TAS was but I also had 175 Knot GS on GPS. Had an "A" hub originally but now have a "B" hub but the airplane has been flying 26-years and has over 3,500 hours on it.

Typical cruise is 150 KTAS at 2,300 RPM / 23" manifold and 7.3 GPH.

Economy cruise is 122 KTAS at 2,100 RPM / 22" manifold and less than 6 GPH. (Have seen 5 GPH with aggressive leaning but I also lose speed by not feeding the horses.)
 
Following some discussion I've decided to go with the Whirlwind.

I am told that the prop could be shipped by the end of November, which would be great as I can then tie the downtime in with my autopilot install, which will also ground the plane for some time as the paperwork goes from one side of someone's desk to the other.

MT's 10 month lead time is a total non starter for me, unfortunately. I was going to buy a Hartzell through Vans, but that's also a non starter now too...
 
8 days after ordering my whirlwind is complete and ready to ship. Once it arrives and flies I'll post some results.

The limiting factor time wise will now be the LAA approving the new propeller, which will probably take a couple of months at best.
 
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