What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Does a constant speed propeller ever pay for itself?

Echo Tango

Well Known Member
I understand that fuel economy will increase with a constant speed prop.

And climb performance increases. But are they really necessary with the increased maintenance and upfront cost? Where is the break-even point?

I admittedly don't know much about them
 
Hi Frank

I understand that fuel economy will increase with a constant speed prop.
IMO, not really. You will spend 90% of your time cruising at a specific altitude band and power setting. Buy a FP Prop optimised for that regime, and the VP Prop will have no better economy.

You might save a few cents each climb, but will lose that (and more) in weight, parts, overhauls, cost etc.

So if $$ is your priority a FP Prop is almost certainly the winner, but then is even an RV the right choice?

To me, the VP Prop "pays for itself" the moment I take off, and my 180HP engine gives 180HP through the Prop, not 100HP. I can do aeros from 60K to 200K and have carefree throttle handling. I have drag on approach/landing.

Only you can decide where your priorities and budget lead you - there is no one answer for all ;)
 
Frank, if you are only looking at "fuel ROI" then the constant speed propeller may not be a sound investment for you. However, a CS prop has other factors to consider. For example, if you have a fixed pitch propeller and it's been set primarily for cruise then you may find some high altitude runways are too short for you. Even at lower altitudes, the CS prop could one day "safe more than gas".

For those interesting in more than the occasional "gentleman's aerobatics", the CS prop has benefits to consider as well.

I'm not saying everyone should invest in a constant speed propeller. I didn't. I'm only pointing out that fuel burn is not the only "ROI" that may be relevant.
 
Last edited:
Hi Frank

IMO, not really. You will spend 90% of your time cruising at a specific altitude band and power setting. Buy a FP Prop optimised for that regime, and the VP Prop will have no better economy.

You might save a few cents each climb, but will lose that (and more) in weight, parts, overhauls, cost etc.

So if $$ is your priority a FP Prop is almost certainly the winner, but then is even an RV the right choice?

To me, the VP Prop "pays for itself" the moment I take off, and my 180HP engine gives 180HP through the Prop, not 100HP. I can do aeros from 60K to 200K and have carefree throttle handling. I have drag on approach/landing.

Only you can decide where your priorities and budget lead you - there is no one answer for all ;)


Thank you for the write-up. So it's not so much an economy thing as a performance item, related mostly to take-off and approach to landing/maneuvers.

Can you expand on the bolded part?
 
....The main benefits of the CS prop are stated already, but I must add that the performance in my aircraft is so phenomenally improved that it makes me feel its worth every dime, every time I fly it. One other consideration that should be stated is this fact. When the day arrives to sell the plane, you should recover 60% to 80% of the initial cost of the propeller in increased value. That makes it somewhat more cost effective. Thanks, Allan...:D
 
I have the opportunity to fly several RVs besides my own and anytime I am piloting one with a FP prop, I think about how much better the experience would be with a CS prop on the nose.

My 7 has a blended airfoil CS prop up front.

Economy? The CS prop cost me many dozens of thousands of dollars more than a FP prop...because I wouldn't have bought my plane if it had a fixed pitch prop installed.
 
Thank you for the write-up. So it's not so much an economy thing as a performance item, related mostly to take-off and approach to landing/maneuvers.

Can you expand on the bolded part?

The engine will only put out full rated power at sea level, full throttle, and red line RPM. With a fixed pitch prop pitched for cruise takeoff RPM will be way lower than red line.
 
I have the 180 C/S. Anyone with a FP uses about 2 gallons an hour more using a higher RPM in cruise to keep up. Some have converted and are very happy, some have not and just keep spending the money on fuel and are very happy. Do the math and then do what makes you happy. It becomes a very personal decision really. 8-10K savings in a 1000 hrs and better resale value? :)
Larry
 
A CS prop will pay for itself the first time you need the extra takeoff and climb performance to clear obstacles on a high density altitude takeoff :D
 
Anyone with a FP uses about 2 gallons an hour more using a higher RPM in cruise to keep up.

I challenge that assertion. A properly pitched FP prop (i.e., pitched for cruise) will achieve a similar fuel burn to a CS prop. I won't argue that there are a lot of advantages to CS, not the least of which is the combined climb and cruise performance.

Greg
 
I have the 180 C/S. Anyone with a FP uses about 2 gallons an hour more using a higher RPM in cruise to keep up. Some have converted and are very happy, some have not and just keep spending the money on fuel and are very happy. Do the math and then do what makes you happy. It becomes a very personal decision really. 8-10K savings in a 1000 hrs and better resale value? :)
Larry

I also have a 180 and mine has a FP. I have kept fuel burn figures for the life of my airplane, which is over 15 years. The overall fuel consumption has been 8.3 GPH, much of that at 165 knot or higher speeds. If you are getting 6.3 GPH at those speeds I am in awe.

There is a small theoretical fuel burn advantage with a constant speed prop due to the lower rpm possible at the same power output, under some conditions. I believe that advantage tends to be overshadowed by other factors. Early in the life of my airplane I took a long trip with 3 other RVs of all different configurations. My FP had the lowest fuel burn over all, probably due to pretty aggressive leaning. I had to throttle back in climb to stay back with some constant speed airplanes, probably due to their heavier weight.

I do like that push back in the seat feeling on takeoff that a light weight constant speed equipped RV can give you, but I also like the very agile handling of my light airplane compared to some I have flown. My airplane performs well at 17,500 and the idea of it not being able to handle any paved strip in the US is something I have trouble grasping.
 
Last edited:
I can fly downwind at 150 kts, pull the power abeam the numbers, and it slows right down into the white arc to set up for landing... and I am doing a 180 degree turn right to the numbers. Plus the 3,500 (+)FPM on take-off is a blast.
 
Larco got it right, in my case for sure.

My change from FP to CS resulted in a solid 2 gallons per hour savings. at typical RV6 o360 CS cruse speeds flown by the folks I fly with. I bought my RV6A with o360 and FP wood prop. FP worked very well from high altitude airports around the SW US.

Agree, FP was not optimum for high speed cruse but it was what it was and IMHO a change was needed. So why not get the most bang for the buck. I now have a bit over 500 hours on a CS that cost something around $2500 including an overhaul and governor. That is at least 1000 gallons of fuel I have saved...at an average of around $4 per gallon over the past few years...my finger math says I'm money ahead and have better performance than before CS.

A side benefit of changing out my wood FP for CS is my static CG moved forward to the center of the CG range giving greater baggage carrying capability...with FP with wife and I on board we were limited to somewhere around 75 pounds of baggage (I've forgotten exact number). We now have use of the full 100 lbs if needed. Agree 75 pounds is a lot but my wife was never one to travel light, voluntarily anyway.

As ever, YMMV, but for me CS is the only way to go.
 
Last edited by a moderator:
If I were to build another RV, I would go back to round dials and give up glass long...long before I would give up my constant speed. I would leave the plane unpainted before I gave up the blue knob. The day JG and JS talked me out of the Catto and into a constant speed was a day I will always be grateful for. The braking with the nose pointed down alone is worth it to me. We build these planes because of the performance they offer...why hamstring it? With that said, there are budgetary concerns for all of us but a used or overhauled constant speed prop is not exactly rare. In my -8, I could use some more front end weight for CG purposes so a fixed pitch would be even less bubba passenger capable.
 
Last edited:
Originally Posted by LARCO View Post

Anyone with a FP uses about 2 gallons an hour more using a higher RPM in cruise to keep up.

I challenge that assertion. A properly pitched FP prop (i.e., pitched for cruise) will achieve a similar fuel burn to a CS prop.
I think the key is in his "keep up" - he has set the cruise parameters, and if they are beyond where the FP Prop works well, then yes, they will use more fuel.

We can cruise the RV-8 4.2GPH quite happily. Saves lots of fuel, but if I wanted to go everywhere at 110K not sure I would have got an RV :eek:

Like many on here, for my purposes I would always go for a VP Prop - but I do not think it is the "best" solution for all. An RV with a FP prop still outperforms most GA types in all areas ;)
 
Van's used to have a good discussion on fixed pitch props in its construction manual comparing cruise pitched props to performance pitched props. I don't see it in their current RV-8 construction manual I have on CD. But the conclusion was that a performance pitch would out perform a cruise prop in most situations.
I have an IO-360 and Catto 3 blade on my RV-8. I'm looking at pictures of my EFIS screen I took on a trip last summer. One shows 15950 DA at 2700 RPM making 178 KTAS burning 7.77 GPH. The other screen shot shows 11859 DA at 2441 RPM's making 158 KTAS burning 5.85 GPH. Both are ROP.
I can climb out of my almost sea level airstrip at 2000 FPM.
No doubt, a constant speed prop can be used to optimize speed, climb and/or fuel consumption, but the above shows a Catto 3 blade is no slouch.
 
Last edited:
Don't confuse "performance" with flying qualities. Lighter airplanes fly nicer. FP equipped machines are usually, inherently, lighter.

That said, you can pry my CS prop out of my cold dead hands......
 
I can fly downwind at 150 kts, pull the power abeam the numbers, and it slows right down into the white arc to set up for landing... and I am doing a 180 degree turn right to the numbers. Plus the 3,500 (+)FPM on take-off is a blast.

And that other plane in the pattern that you didn't see just about got run over. I know, because that other plane was me last summer when an RV-7 almost broadsided me on base flying the same pattern you describe. (That happened at a Class D airport and we were both talking to the controller.)

Another reason to use a FP prop is to maximize your useful load without raising Van's recommended GW.

As others have said, the push in the backside and initial climb with a CS prop is impressive. Any time you think your FP RV is a dog, go rent a 172 and remind yourself how outstanding your RV is.
 
You might wind up being unhappy after you buy a FP and then sell it down the road to replace it with a CS. Plus there's the extra work installing the governor, oil line and control cable after you already set it up for the FP. Do it right the first time. There is a big difference between the two.
 
One aspect of the FP vs CS prop discussion that I have discovered first hand is operating out of short, confined runways may be a little bit riskier with a FP prop. RVs are slick and even with full flaps, if you point the nose at the ground during an approach, it picks up speed and a FP prop offers little drag. Slowing down and getting the acft on the ground and stopped then becomes an issue. Yes, you can slip an RV very easily, but its not the ideal answer to the problem. Many times I have operated CS prop RVs and other CS prop equipped acft (Maule M-7, Baron 58, Navajo) into short, confined runways and having the ability to aim at the threshold and make a steep approach by pulling the power back and using the prop(s) as brake is essential to a safe landing. Also, the ability to add power and get immediate thrust when the approach is botched can be critical. Possibly an answer to the question; "does a CS prop ever pay for itself", it may pay for itself in added ability and safety in certain operating conditions. The weight, complexity and cost savings may favor the FP prop, but in certain conditions, the CS prop offers distinct advantages. The cost delta of CS prop over a FP prop will seem small after an accident. It all depends on your abilities and where you operate your RV. With all that being said, I intentionally put a FP on my RV and it has been an exciting Phase 1 at times, but I have learned to operate within my limitations. 3 point landings work best on short strips.
 
Here are a couple of thoughts and I?ll try to keep my opinion out of it as much as possible:

It has been established that an optimized fixed pitch propeller will outperform a C/S unit at a particular airspeed. At one airspeed it will provide more thrust with less weight, cost and complexity. It has also been established that there are plenty of fixed pitch RV?s flying and most of them will match or exceed the performance of similarly powered spam cans.

But the real question is ? Is this ?good enough? for you? And in most cases, the only way to answer that is with an honest look at your mission requirements. If your mission involves the requirement to achieve 2750 RPM on takeoff, climb to cruise altitude and then pull the RPM back to 2350 for the next two or three hours ? all while at WOT, then the choice is pretty clear. If your primary mission is 30 minutes to the pancake breakfast at a neighboring airport, then the answer is less clear.

The bottom line is that you can?t really say categorically whether a C/S is ?better? than a fixed pitch ? Both propeller systems have their place. While there are some very compelling reasons to choose a C/S propeller system for your airplane, those reasons my not apply to your situation. That said; if your primary reason for selecting a C/S prop is to reduce lifecycle costs through fuel savings, then you probably don?t need one.

As an aside, I guess it?s good that Van does not offer wing flaps as an option. Can you imagine the debate concerning performance vs. the ?added cost, weight and complexity? of wing flaps?
 
ROI

Strictly from an ROI perspective a CS setup from Vans is approximately $8,800.00, a FP is approximately $3,500.00; or about $4,300.00 more for CS.

At $6.00 a gallon that is 700+ gallons of gas. So from an ROI perspective FP is the way to go. (The numbers are approximately based on a quick review of Vans online catalog, you might get the components for less elsewhere.)

Having said that, I am putting CS on my RV-7 because I want CS. I suggest you build the airplane you want. I am not sure ROI and airplane ownership run together.

Just my two cents.
 
Last edited:
And that other plane in the pattern that you didn't see just about got run over. I know, because that other plane was me last summer when an RV-7 almost broadsided me on base flying the same pattern you describe. (That happened at a Class D airport and we were both talking to the controller.)

I did see the other aircraft over the numbers and the controller did not have his head jammed up his backside like your controller did, so I was safe and flying the airplane well within it limits. At uncontrolled fields, I do match the speeds of C-172s.
 
Besides better fuel economy and overall better performance there's other factors to consider. There's more vibration when running FP due to higher RPM's, there's longer engine life running lower RPM's, less pilot fatigue with less vibration, quieter flying. Also better resale down the road.
 
OK, I have to jump in here.......

Besides better fuel economy and overall better performance there's other factors to consider. There's more vibration when running FP due to higher RPM's, there's longer engine life running lower RPM's, less pilot fatigue with less vibration, quieter flying. Also better resale down the road.

My Catto F/P prop is "turbine smooth" compared to any C/S prop.
 
As an aside, I guess it?s good that Van does not offer wing flaps as an option. Can you imagine the debate concerning performance vs. the ?added cost, weight and complexity? of wing flaps?

Indeed!

Sometimes it seems "simple" has become absolute absolute dogma within certain parts of the GA community. Simplicity is good, but it needs to be weighed against capability and ease of operation, and kept in mind that simplicity isn't always directly apparent. Compared to an E6B, a $10 scientific calculator is fiendishly complex, nevermind even a basic smartphone or tablet. But if I want to figure out fuel burn or crosswind component, I know which one I'm going to pick up, and it's not the "simple" E6B.
 
My Catto F/P prop is "turbine smooth" compared to any C/S prop.

It's not the prop it's the higher RPM's. One thing I can say for sure... I've converted many FP's to CP's and there's one thing in common to ALL.. That big smile on the owners face you can't pry off after the first flight.
 
Last edited:
It's not the prop it's the higher RPM's. One thing I can say for sure... I've converted many FP's to CP's and there's one thing in common to ALL.. That big smile on the owners face you can't pry off after the first flight.

Well we can agree to disagree, but if the prop is properly balanced, rpm doesn't matter. Many people run F/P props at 3K rpm and above with little to no vibration.

I, myself, have also done a number of conversions, and the smile doesn't come from smoothness.
 
A C/S propeller system is simply a “performance envelope expansion” device – just like:

Adding lights so you can fly at night;

Adding O2 so you can fly higher;

Adding inverted fuel and oil systems so you can maintain negative G flight;

Adding flaps so you can land shorter;

Adding IFR equipment so you can fly in a larger variety of weather.

None of the above are required for basic flight, but all expand the capabilities of the aircraft and all add weight, cost, complexity and maintenance.

Needs are dictated by mission; wants are dictated by wallet.
 
Well we can agree to disagree, but if the prop is properly balanced, rpm doesn't matter. Many people run F/P props at 3K rpm and above with little to no vibration.

I, myself, have also done a number of conversions, and the smile doesn't come from smoothness.

We do disagree. I balance props. And there's no such thing as an engine with NO vibration (piston). The faster they spin the more noise and vibration they produce. I will say that a light FP prop in itself will have less vibration potential then the heavier CS prop. But with both balanced right that equation is no longer a factor, it's the engine and components resonance that create vibration, this includes the airframe and all the hardware.
 
Strictly from an ROI perspective a CS setup from Vans is approximately $8,800.00, a FP is approximately $3,500.00; or about $4,300.00 more for CS.

At $6.00 a gallon that is 700+ gallons of gas. So from an ROI perspective FP is the way to go. (The numbers are approximately based on a quick review of Vans online catalog, you might get the components for less elsewhere.)

Having said that, I am putting CS on my RV-7 because I want CS. I suggest you build the airplane you want. I am not sure ROI and airplane ownership run together.

Just my two cents.

It would be interesting to see the comparison if, instead of using a CS prop, one takes the $4300 saving and invests it into a higher HP engine. Instead of an IO-360/180HP, go to an IO-375 or IO-400. Weight would be slightly higher than the stock engine but probably not as much as the prop weight difference. Seems to me that this would provide a faster TAS at the optimal altitude.

Climb rate may still be better with a CS, but the extra 20-30 HP from the engine will help the FP a lot, especially if its lighter. Trade off some of the top speed for a lower pitched prop and climb rate can be improved.

I bet someone can calculate the equivalence. An 1800 lb aircraft at X horsepower fixed pitch, optimized for the same top speed would generate the same climb rate as an 180 horsepower Hartzell CS engine. Solve for X, within the constraints of gross weight.
 
Nearly twenty years ago when I was mulling the configuration of my pending RV-6 build, CS props were regarded by most builders (and Vans) as unnecessarily heavy, complex, and expensive. I consequently installed the FP metal Sensenich that was designed for the RV. It is pitched for cruise--the plane has been a joy to fly and has transported me to a good portion of the country with good performance and economy since 1999. Prop maintenance cost for the past 1300 hrs has been.....zero.

Now days....people ask me which prop I have and when I tell them it is FP they look at me with pity, almost to say "Bless his pea-pickin' heart, that boy is stuck with a slothful dog of an RV....too bad he doesn't know anything about props". My how times change. My response is to hop in the -6 and go flying. Thankfully it doesn't know that it is disrespected and it just keeps on ripping up the sky like it always has.

I have no reservations about recommending either type prop to anyone who asks after we have discussed their expectations. But some of the comments in this thread about the vast superiority of a CS prop border on ridiculous with their claims of a huge advantage in speed and economy. Yes, a FP prop that is pitched for climb is going to be struggling to keep up with any RV with a cruise or CS prop. But a good FP with optimum pitch delivers strong, smooth cruise with more than satisfactory climb performance. Field history has been established by hundreds (thousands?) of RVs with simple props......and happy owners.
 
Last edited:
I have no reservations about recommending either type prop to anyone who asks after we have discussed their expectations. But some of the comments in this thread about the vast superiority of a CS prop border on ridiculous with their claims of a huge advantage in speed and economy. Yes, a FP prop that is pitched for climb is going to be struggling to keep up with any RV with a cruise or CS prop. But a good FP with optimum pitch delivers strong, smooth cruise with more than satisfactory climb performance. Field history has been established by hundreds (thousands?) of RVs with simple props......and happy owners.

Very well said.
Everyone has the right to their own choice and opinion. I put on a FP prop and will never change. Works for me and many others on their RV. Simplicity, $4300 in my pocket, more bucks saved every year when I add up maintainence bills, and only a slight reduction in performance at limited places in flight envelope is more than enough to justify my decision.
 
Last edited:
I would build mine the same, 180hp O-360 and Catto given the same money saving circumstances. I would also have used an O-320 had I found a good deal. I have never felt like I couldn't keep up with my RV buddies, perhaps they're just being nice.
My buddy's 180hp O-360 Hartzell spinning RV6 will pull away on takeoff until 120 knts, 120knts and above performance is nearly identical. His 6 does push you back in the seat compared to mine on takeoff.
I really like the feel of my Catto while cutting around compared to then Hartzell, pretty sure it lets me butcher some aeros without being able to feel it. I've only rolled the Hartzell, it's a much different feeling than the Catto. My aero instructor taught me to set the power and use G loading to control airspeed, no issues with speed control on the down lines. I probably don't know what I'm missing.
My buddy's 6 with the Hartzell always uses less runway, sometimes I wouldn't feel comfortable unless I had at least 2000 feet with my fixed pitch.
In the end they are both great airplanes I would fly any day over a certified plane, well I would like to fly a Pitts, Cub, Highlander, Glassair, Lancair anything that burns jet fuel......
 
...I have no reservations about recommending either type prop to anyone who asks after we have discussed their expectations. But some of the comments in this thread about the vast superiority of a CS prop border on ridiculous with their claims of a huge advantage in speed and economy...

I have noticed on this and other aviation forums that people tend to ignore (or don't know enough to define) the mission requirements and seek "opinion" to choose something. Look for example, at how many questions come up regarding the choice between a RV-12 and any other RV... Really? If you are considering a -12 or a -7, then it's a fair bet your flying mission is undefined or you just like to build. Similarly, if you are using the up front cost as a barier to buying a C/S propeller system, then you probably don't need one. I know my mission for my Rocket (and the -8 I fly), and a C/S is a hard requirement- regardless of cost. My Starduster Too, on the other hand, was going to be fixed pitch.

It's a little like going into a store to buy work shoes - you should know before you step through the door if you need steel toe construction boots or soft leather wingtips.
 
Last edited:
I like the Catto because it is smooth, simple and just as efficient as C/S up high. Take off and climb suffer until rpm gets up to 2500, HP is HP makes no difference what the prop.

The Catto airplane is at least 55 lbs lighter than with C/S, that converts to better flying qualities all around. Elevator trim is not maxed out on final.

The for sale return is less, but so is the initial investment - its a wash.

To each their own, I've had both. Light weight is always good. Performance is always good, take your pick.

dd
 
Last edited:
I like the Catto because it is smooth, simple and just as efficient as C/S up high. Take off and climb suffer until rpm gets up to 2500, HP is HP makes no difference what the prop.

The Catto airplane comes in is at least 55 lbs lighter than with C/S, that converts to better flying qualities all around. Elevator trim is not maxed out on final.

The fore sale return is less, but so is the initial investment - its a wash.

To each their own, I've had both. Light weight is always good. Performance is always good, take your pick.

dd

55 lbs? I think you are way off base there. As for weight OFF the front converting to better flying qualities.....not on my -8.
 
55 lbs? I think you are way off base there. As for weight OFF the front converting to better flying qualities.....not on my -8.

How much does your 8 weigh, Bill? Mine came in at 1029.

I believe 55 lbs is in the ball park, depends on the props compared of course.

The difference in flying qualities is subjective, we all have different tastes but generally lighter is better, at least Van has believed that since the beginning.

I pealed off over 180 lbs when going from the Subby H6 to Lycoming 180 power plant with the RV-7A, most of it from up front. I liked immediatly the difference in flying quality, even with the FP Catto vrs the MT CS. The greatest transition item was slowing to land, the FP requires more planning. I recently reduced idle rpm of 650 from 800 to improve stopping a bit.

To each his own. The bottom line though is any RV is a delight to fly, this discussion is comparing RV to RV and I should not even comment on it, the choices are so personal. Neither prop system detracts from the overall fun and satisfaction of flying the RV.

My friend Oly recently flew a 4 with FP vrs his CS, how 'bout a report Oly. :)
 
I challenge that assertion. A properly pitched FP prop (i.e., pitched for cruise) will achieve a similar fuel burn to a CS prop. I won't argue that there are a lot of advantages to CS, not the least of which is the combined climb and cruise performance.

Greg


100% agree with Greg... I have a wood FP Prop and have found that I'm actually faster than many of my fellow RV friends in cruise and full throttle during cruise. Now I'm not saying this is the case for every RV out there and definitely not challenging anyone :D, however, even if I'm burning 2 gallons per hour more (which I'm not but let's say I am) I guess then it may pay for itself if nothing goes wrong with prop, prop governor and anything else associated with it.
 
There is no financial advantage of FP to CS other than the CS costs more. The real difference comes down to performance. Imagne having a Porsche with only one gear that runs the full range of speed compared to a six speed manual. You can set each gear where you want it depending on how your driving (traffic, street, spririted, track). Also, the day may come when you need or want to sell the plane and at least half the potential buyers, probably more, will not go any further than seeing you have a FP on the plane and move on to the next one for sale. Then there's formation flying. If you ever do any formation flying you will want the CS prop. I know there are lots of guys that fly formation with FP but it is more difficult. Acro....CS. I would never purchase an RV with perhaps the exception of the RV3 and even that with at least a ground adjustable prop, without a CS. I can't imagine a C182 without a CS just as I can't imagine an RV without one.

If $$$ are your concern then skip all the fancy cockpit stuff to save $4000 and spend that on the upgrade to CS.
 
A six speed Porsche to a one speed Porsche? No, its not like that at all. Guess this will have to go in the endless debate section.
 
Would retractable gear ever pay for its self? 5-10% faster cruise for the same fuel burn. You'd be asking much the same questions as with a c/s prop. It's heavier, more complex, more maintenance, more expensive.

Having said that, I bet the majority on here will say retractable gear is unnecessary. I'd guess that about 40% on here will also say that a c/s prop is unnecessary. It's all personal choice. Are the downsides worth the advantages.

As for if a c/s prop will ever save enough gas to pay for it's self? Too subjective to say. There's so many different options/pitches for fp props. Doing lots of long distance flying with a coarse pitch fp prop will probably save money in the long run. Just think that a c/s in in cruise, the blade angle is basically staying the same the entire time.
 
A six speed Porsche to a one speed Porsche? No, its not like that at all. Guess this will have to go in the endless debate section.

Yes it is like a transmission compared to one gear but a CVT compared to one gear would be a better comparison.

you-get-what-you-pay-for-v1.png

On my RV-6, if the CS were changed out for a FP, the payload would be cut in half when at the AFT CG.

Ask the people with FP props about how much weight they can put in the aircraft before they hit the AFT limit. Compare that to the CS guys.

I would rather own a Champ or Cub than own an RV with a FP prop. When I give up a CS prop on the RV, that is the day I will give up on Lycoming and Lycoming Clone powered RVs.

A fixed pitched prop on an RV may be the right thing for you but it is defiantly not something that I would own.
 
Your mileage may vary ....

On the SAME aircraft, I have flown the following:

O-320 (160 HP) with
- Ed Sterba 2-blade Fixed Pitch Wood Prop (~1000 hours)
- MT 2-blade Fixed Pitch Composite Prop
- Catto 3-blade Fixed Pitch Composite Prop
- Hartzell 2-blade Constant Speed Metal Prop

O-340 (~175-180 HP ???) with
- Catto 3-blade Fixed Pitch Composite Prop
- Whirlwind 2-blade Ground Adjustable Composite Prop
- Whirlwind 2-blade Constant Speed Composoite Prop

First, ALL of these companies have been great to work with.
Second, EACH of the props did what they were DESIGNED to do.

Now, some comments.

The plane was built with the Ed Sterba prop. WE were keeping the costs down and that is what I got used to with the plane. It was smooth, and if I wanted to run the RPM up a bit, I could go rather fast. For the RPM, I was most comfortable with though, I planned for 150KTS.

It was with this prop that I got my FFI Formation Checkride done. A lot more work (anticipation) than with a CS prop, but doable.

The biggest downside was if I was flying with friends and there was rain, I had to slow down and *some* of my friends were NOT into slowing down. :)

I decided to try the new MT 2-blade prop with metal leading edge. The assumption that I would not have to slow down as much. That prop too was smooth, and I could get over 170KTS if I ran up the RPM, but after some other issues, I decided to send it back to MT for a refund.

I later got the opportunity to get a 3-blade Catto with leading edge metal. It was REALLY smooth. Looked great and flew great. I changed it out later when I needed to do some engine work and had a good deal on a CS setup for my engine.

Thus the Hartzell. This made my formation flying much better and this was about the time that I was getting more serious about it and "Team RV" (now Team AeroDynamix) as the airshow team was coming into its own. So it was NEEDED! I sold the Catto to a friend with an RV9A with IO-320 and he LOVES its. Actually, he is now on his third or fourth as he keeps upgrading when something new comes out.

For the type of flying that I NOW do, the Hartzell CS was the best answer.
- Acceleration/Deceleration
- Weight on the nose

There is the bonus of shorter take-off runs as well.

Fast forward to my need/decision to "upgrade" my engine to the ECI 340 "Stroker".

I could not use my existing Hartzell on it (the old one was for the 160 HP O-320)
And, after much discussion with Hartzell, we mutually decided that at this time the the harmonics they were seeing with that engine and their props was not something either of us wanted to experiment with just yet.

I discovered that Cattol and Whirlwind had props that they were willing to make available for the O-340.

Sooooo.... I called up and got a Catto for it. Great experience with Nicole.
Unfortunately, after just a few minutes of flight, I found that the one they made for it needed a LOT more byte (as in start over with a new prop) and they had a long lead time. And, my plane had been down long enough already getting the engine upgraded. So back it went. (Thanks Nicole!)

I figured that the Ground Adjustable from Whirlwind would allow me to "dial it in". And my buddies had had good experiences with Whirlwind. I get one. Dial it in and .....

After flying with the CS prop, the take-off roll, acceleration and deceleration for formation was not what I wanted FOR MY KIND OF FLYING.

The prop and the Whirlwind people were GREAT! Can't say enough good things about them and their prop (like the Catto) but it was not my cup of tea.

Fortunately, the same blades are available in a CS version. So I got one of those and that is what is on the plane now.
------------------------------------------------------------

The summary of all of this long winded dialog is...

Get the prop that works for the way you plan to fly.
There is no single answer that anyone can give. It will be up to your taste$.

If you don't need CS, Catto and Whirlwind (and Ed Sterba!) make a great fixed pitch and light prop for the RV.

If you want shorter take-off rolls and want a bit more acceleration/deceleration for your formation stuff then go for a CS.

If you need some weight on the nose and FP, the Sensenich is great.
If weight and CS, the Hartzell metal CS is great

Obviously Hartzell is the "gold standard" and in my experience, the Whirlwind is a good choice as well.

James

p.s. I am affiliated with Team AeroDynamix and Hartzell and ECI are sponsors of the Team.
 
Yes it is like a transmission compared to one gear but a CVT compared to one gear would be a better comparison.

you-get-what-you-pay-for-v1.png

On my RV-6, if the CS were changed out for a FP, the payload would be cut in half when at the AFT CG.

Ask the people with FP props about how much weight they can put in the aircraft before they hit the AFT limit. Compare that to the CS guys.

I would rather own a Champ or Cub than own an RV with a FP prop. When I give up a CS prop on the RV, that is the day I will give up on Lycoming and Lycoming Clone powered RVs.

A fixed pitched prop on an RV may be the right thing for you but it is defiantly not something that I would own.

Gary, if you followed the gross weight recommendation from Van's, what would your useful load be?

Mine is 570 lbs at the 1600 lb limit.
 
Somewhere in every C v. FP thread there's a "properly set up" disclaimer for FP. How many FP props must one buy before finding the "proper" one for the ship and standard mission, when the answer can be found with the twist of a blue knob on a CS?

I wouldn't hobble RVs with their 4:1 speed ratio. That kind of airplane just begs for a CS. Do you smile when you open all the holes on a V-8? That should answer.

CS props differ, too. I've had a BA Hartzell and a Whirlwind 74RV on the same -7, and they perform about the same. A friend's equally powered 7 with a 3-blade MT accelerates much quicker; it pops off the ground way before mine does.

Add this consternation to fretting over to prime or not to prime, T v. N dragger, tip v. slide, carb v. FI, mags v. EI, ad infinitum, it's a wonder any of us builders sleep at night.

John Siebold
 
This is the most entertaining thread I've read since the cease fire in the primer wars! :D
 
<snip>
I would rather own a Champ or Cub than own an RV with a FP prop. When I give up a CS prop on the RV, that is the day I will give up on Lycoming and Lycoming Clone powered RVs.
<snip>

Wow.............

I owned a Cub but sold it to fund the engine for my FP RV-6.....maybe I should have sold the RV project and kept the Cub.......

Nawwwwww...........
 
Back
Top