Van's has changed Hartzell recommendations

FWI. Van's has removed a number of props from there order form (but the form has the same rev #). There are now only 4 choices, one for I(O)-320's, one for I(O)-540 and two for I(O)-360's. The 180 hp and 200 hp now get the same prop the C2YR-1BFP/F7497 in either 72" or 74".

I faxed in my order yesterday for a F7496 and got a call in the afternoon explaining that Hartzell now recommends the F7497.

BTW. I printed the "old" order form on Sunday and noticed that the current form has removed the F7496's or F7666A4 as options.

Do you know what the restrictions are for this prop on an IO-360, 180 HP? It is no longer in the catalog and I can' find it on the Hartzell of Van web site.

I asked Hartzell tech support ...

I sent a note to Hartzell asking why the change and if there are any restrictions. I will post their reply when I get it.

There's a spreadsheet somewhere in the props/engine section from Les, the Hartzell guy. Posted a couple of months ago. The 4797 has no restrictions.

*edit - in the FAQ, http://www.vansairforce.net/faq.htm

I have had confirmation from Hartzell that their 7497 prop has
been officially approved on 180HP Lycomings with no operating
restrictions or placards. I have the e-mail at work so I can't reproduce it here but will do so tomorrow AM, unless someone else has done it by then.

The TCDS will state the following engines:
IO-360-B1A, -B1B, -B1D, -B1E, -B1F, -E1A, -M1A

This TCDS is OK for the Lyclones here in the UK, tho obviously I don't know about the US. I think this change has been coming for some time and in fact I ordered a 7497 some months ago for my Superior 180hp as Hartzell were very firm in their view that it was th prop to go for.

Hope that helps

Chris.

HA - srv got there first!

No restrictions at all?

chris mitchell writes: I have had confirmation from Hartzell that their 7497 prop has
been officially approved on 180HP Lycomings with no operating
restrictions or placards. I have the e-mail at work so I can't reproduce it here but will do so tomorrow AM, unless someone else has done it by then.

What about electronic ignition and 9:1 pistons?

Yep its cool

Rick_A said:

I sent a note to Hartzell asking why the change and if there are any restrictions. I will post their reply when I get it.

Click to expand...

I had a long talk with hartzell.

The 7496 was their first go at it. Its a fine blade and a little thinner than the 7497. As they developed the 7497 for the IO360 angle valve they realized it would work on the 180HP as well with out the small limitations.

I asked about weight and loss of performance?

Yes the 7497 weighs a little more but as a precentage of the props total weight its very small (no specifics given).

Performance? Talking to the engineer that did the flight test development for the 7497 the there may be a slight hit on speed, but its too small to measure. Hartzell has the same challenges in getting good flight test data like we all do, especially when trying to compare two different props.

If you have the 7496 blade its still rocks and you do get that slight weight advantage and minor edge on speed. The limits on the 7496 are pretty minor. So if you have a 180HP 360 you have the choice of either. However if buying new today, the 7497 with no limits is the way to go as Hartzell recommends.

I don't know about 9:1 pistons but here is a clip of an e-mail from Hartzell in respnse to a question about LASAR ignition - in UK we have to use at least one magneto so we cannot have a totally electronic ignition system

"The LASAR ignition is basically an electronic ignition system that piggybacks onto a relatively standard magneto. As I understand, it provides the timing advance capability like other electronic ignitions but the backup mode is a standard magneto. Although we have not tested a true electronic ignition on the -M1( ) and cannot give an official approval, I personally feel the 7497 is the best choice for that combination. Some of the Superior and ECi engine clones do not have dampers, but I suspect the 7497 could also be approved on those engines as well. When we did testing with the 7496, we found the Superior O/IO-360-B1A2 (no dampers) was better than the Lycoming."

I cannot work out how to add the .pdf from Hartzell for the TCDS here - if someone can tell me I'll gladly add it!

Chris

I got this tech sheet from Hartzel this morning. Here is the text:




Flight testing of a new "blended airfoil" Hartzell propeller has been accomplished in accordance to FAR 23.907 to ensure compatibility with the Lycoming O-360-A1(A, C, D, F, G, H, P). As a result of this testing, Hartzell propeller model HC-(C,F,M)2YR-1(B)FP/F7497 is recommended for use with these engines. The following results were obtained:

Hartzell Propeller Model HC-(C,F,M)2YR-1(B)FP/F7497 is vibrationally approved when mounted on Lycoming Model O-360-A1(A, C, D, F, G, H, P) engines rated at 180 HP at 2700 RPM without dampers (8.5:1 compression ratio) with magneto ignition and installed in normal category type single engine tractor aircraft such as the Van's RV series. There are no operating restrictions.

Diameter range is 74" to 72".

At this time no aerobatic testing has been performed with the above listed propeller and engine combinations.

Testing of this propeller on the Lycoming Model O-360-A1( ) engine equipped with Electronic Ignition and/or FADEC has not been conducted at this time.

Hartzell Propeller Model HC-(C,F,M)2YR-1(B)FP/F7497 is vibrationally approved when mounted on Superior Model O-360-B( )( )2 engines rated at 180 HP at 2700 RPM without dampers (8.5:1 compression ratio) with magneto or electronic ignition and installed in normal category type single engine tractor aircraft such as the Van's RV series. There are no operating restrictions.

Diameter range is 74" to 72".

At this time no aerobatic testing has been performed with the above listed propeller and engine combinations.

Testing of this propeller on the Superior Model O-360-B( )( )2 engine equipped with FADEC has not been conducted and is not a recommended combination.

NOTE: Propeller vibration characteristics and stress amplitudes on a reciprocating engine installation are primarily mechanically generated by the engine. Any modification to the standard engine configuration to include high-compression pistons, electronic ignition, FADEC, tuned induction and exhaust, and turbo-charging or turbo-normalizing have the potential to adversely affect the propeller vibration characteristics and stress amplitudes. Hartzell Propeller therefore does not endorse any such engine modification unless the specific engine and propeller configurations have been tested and found to be vibrationally acceptable according to 14 CFR 23.907.

The Hartzel tech sheet, which is quoted above, lists tuned exhaust as having a potentially adverse affect on prop vibration and stress.

My sense is that most of us run tuned exhaust systems like Larry Vetterman's. I do. And, it's a great product. I see many threads addressing the potential impact of high compression pistons and electronic ignition on prop vibration and stress. But, I don't see much about tuned exhaust. Why?

Is the conventional wisdom that tuned exhaust has only a negligible impact on prop vibration and stress? I'm just lookin' to learn something.

Good point, That's why its Experimental

rv620mr said:

The Hartzel tech sheet, which is quoted above, lists tuned exhaust as having a potentially adverse affect on prop vibration and stress.

My sense is that most of us run tuned exhaust systems like Larry Vetterman's. I do. And, it's a great product. I see many threads addressing the potential impact of high compression pistons and electronic ignition on prop vibration and stress. But, I don't see much about tuned exhaust. Why?

Is the conventional wisdom that tuned exhaust has only a negligible impact on prop vibration and stress? I'm just lookin' to learn something.

Click to expand...

Because no one really noticed, GOOD POINT! Gold star.... It has been mentioned but I don't think any one has really flagged it or tested it.

You are right the 4-into-1 "tuned exhaust" or headers do change the flow, power and pulses, no doubt.

I did ask about high compression pistons. Engineers don't like to speak off the record, but off the record the engineer I talked to thought HC pistons do make small changes to existing limits, such as a little border or wider range (not much). He did not think it would shift the whole range up or down. Basically higher compression does not make wholesale large changes in the vibration characteristics but small ones.

I suspect exhaust (wild guessing on my part) would have similar affect as HC pistons, in that it will increase the HP slightly. The cross-over Vetterman is no slouch; it's way better than any stock Cessna or Piper exhaust system. However 4-into-1 headers do have a little more savaging and affect on the power curve over cross-overs. I doubt there would be any huge shift, change or new limits that did not exist already (like HC pistons). However the HOTTER the engine (further from stock) the more you have to think about the affect on a metal prop, more so with the 7496 than the 7497 blade.

Power Flow makes those 4-into-1 exhaust systems for certified planes? Did they do prop vibration testing on every airframe for those STC's? They claim 15% or 20 HP power increase! Its not MORE than rated HP. It does not turn a 150/160 HP O-320 into 170/180HP, it just gets back close to rated hp of the engine, overcoming the poor stock exhaust, which cost about 20 HP. Still I wounder did the FAA consider the affect on the props. They make Power Flow systems for Mooney's, which of course uses Hartzell constant speed props.

Your exhaust point is super valid. It's why certified planes are so picky about having the original configuration not be altered, with out all kinds of hoop jumping. The cause and affect can not always be predicted, so each and every change needs to be tested.

72 or 74 inches

Van offers both 72 & 74 for 7A.
What is the difference (except for the ground clearance)?

Ben

72 vs 74

Len Kaufman (RV-8) told me you can grind down the 74" if you have tip damage that's severe, but the 72" can't be shortened to address a tip issue. I got the 72" for increased ground clearance before knowing the above. Bill

Bill Dicus said:

Len Kaufman (RV-8) told me you can grind down the 74" if you have tip damage that's severe, but the 72" can't be shortened to address a tip issue. I got the 72" for increased ground clearance before knowing the above.

Click to expand...

That was one of the reasons why I bought a 74" prop, but I am no longer convinced that it holds water. If you have a major prop strike, you will almost certainly damage more than the last inch on the blade. If you have a minor prop strike that only damages the last inch, you probably wouldn't have damaged a 72" prop, as the shorter blade wouldn't have hit.

I bought a 74" as the data I got from Hartzell suggest it would be very slightly more efficient at 65% power and below, which is where I expect to cruise. It will be a bit less efficient at high power and/or high rpm, so max speed, and 75% cruise would be better with the shorter blades. I did this analysis for the 7666 blades. It might not be relevant to the newer blended airfoil props.

Excellent point and correct as usual

Kevin Horton said:

That was one of the reasons why I bought a 74" prop, but I am no longer convinced that it holds water. If you have a major prop strike, you will almost certainly damage more than the last inch on the blade. If you have a minor prop strike that only damages the last inch, you probably wouldn't have damaged a 72" prop, as the shorter blade wouldn't have hit.

I bought a 74" as the data I got from Hartzell suggest it would be very slightly more efficient at 65% power and below, which is where I expect to cruise. It will be a bit less efficient at high power and/or high rpm, so max speed, and 75% cruise would be better with the shorter blades. I did this analysis for the 7666 blades. It might not be relevant to the newer blended airfoil props.

Click to expand...

Excellent post as usual. Why not an ODD length? 73" Just asking.

The deal is any prop strike will be bad news so don't have them. Will the 1" gnd clearance between 74-72 make much difference? I guess it could but chance is if you really wack them, what ever the scenario, you just bought two new blades, prop overhaul and likely a tear down inspection of the engine as well. I don't even like to think about it.

This is one of the best arguments for a light relatively cheap fixed wood prop (not even fiberglass coated). If it hits dirt, it shatters and saves the engine, more likely than not. Replacement of the prop is relatively cheap. So if you have a constant speed prop or metal prop don't have a prop strike.

Kevin: Good thoughts. You make me feel better about the 72 incher. Was unaware of performance differences for the two props. Wonder if they apply identically to the BA model? Thanks for the info. Bill

Van's Aircraft and 72" vs. 74"

If you look the Van's order form (http://www.vansaircraft.com/pdf/hartzell_order_form.pdf) you'll notice that they will recommend 72" propeller for 'any model' while 74" propellers for only A-models (tri-gear). Hope this helps to make you choice.

Kevin Horton said:

If you have a major prop strike, you will almost certainly damage more than the last inch on the blade. If you have a minor prop strike that only damages the last inch, you probably wouldn't have damaged a 72" prop, as the shorter blade wouldn't have hit.

Click to expand...

I'll give you another reason why a 72" hartzell makes more sense. If you have a prop strike and make an insurance claim (and a prop strike is virtually certain to be an insurance claim) you can be GUARANTEED of getting a new prop. But if the insurance company can repair that 74" prop then they certainly will to save a few dollars.

Builders who plan on insuring and who buy 74" props because they think they can be repaired in the event of a prop strike might just be shooting themselves in the foot.

I would get the 72" 7496 if possible

Within the past couple of months I asked for and received efficiency graphs custom plotted for me by Hartzell and George's statements conform to those graphs and what I was told in the accompanying message. The pre-blended airfoil 7666 efficiency drops drastically above 165 KTAS while the 7496 declines very slowly after peaking at 185 kts. Because of the confidentiality of disclosure statements in the correspondence I cannot duplicate what I was told or shown but if I could find a 72" prop configuration with Hartzell 7496 blades there is no way I would settle for the same prop with 7497 blades. You will have to read Jack Norris' on propeller theory (a painful reading experience) to learn about tip loading problems, etc. The bottom line is the new 7497 is a performance compromise from all I have seen.

Bob Axsom

How much?

Bob Axsom said:

The bottom line is the new 7497 is a performance compromise from all I have seen. Bob Axsom

Click to expand...

How much? It was expected the blade is thicker, which was done as a "compromise" to improve vibration characteristics and RPM limits. I talk in broad terms and in my discussion I heard the difference was small, 7496 v. 7497, may be a one mph? So Bob what is the deal? I think for the avg pilot the 7497 is better and what is recommended. Clearly the 7496 is a rocking blade for the 180HP, but if you go 200HP you have (suggested) to go 7497.

That is probably on the right order

The difference is reported to be small but when you are struggling for fractions of a knot, throwing away a whole knot is unacceptable. My prop is "only" three knots slower than a 7496 and yet I try to rationalize on the order of $10,000 for 7496 blades (haven't succeeded yet).

Bob Axsom

HC-M2YR-1...F7497BFP

can anyone tell me the difference between the HC-M2YR-1BFP as compared to HC-C2YR-1BFP.....F7497 blades for both....the C2YR seems to be the reccomended prop by vans....RV8...T/W...IO360 Superior...i have an opportunity to buy the M2YR.......rgds to all...stan

'C' is the standard hub, 'M' is the extended hub (BTW, Hartzell has an application guide online and the model designators are explained near the front). I'm not sure exactly what that translates to (though the guide seems to indicate that there is an extra 3.5" between the flange and the parting line on the hub) but I expect you can look forward to spinner fit issues and possibly some extra weight up front.

<<Is the conventional wisdom that tuned exhaust has only a negligible impact on prop vibration and stress?>>

In my opinion, yes.

Tuned pipes and high compression pistons both add horsepower, but they do it in very different ways. The key issue regarding propeller vibration is an increase in the amplitude of a forcing frequency, ie variation in force applied to the crankshaft as it rotates through 720 degrees.

Tuned pipes (hopefully) improve cylinder scavenge and filling (negative pressure during overlap) and reduce pumping losses (negative cylinder pressure following blowdown as well as less overall backpressure, ie no muffler).

Improved cylinder filling should increase gas pressure above the piston during combustion and increase force to the crank during that period of rotation. However, I don't think we get any huge improvement in filling; we don't have the necessary cam timing to make pipe tuning really effective.

Reduced pumping loss would tend to reduce crankshaft torque variation in that part of the cycle, a good thing for a prop. And I think backpressure reduction is the primary source of horsepower improvement in our case.

High compression pistons are another animal. They increase crank torque variation during compression (slow the crank). They increase gas pressure during combustion and thus again increase crank torque variation (acccelerate the crank). If they weigh more due to increased crown height (I dunno, do high compression Lyc pistons weigh more?), they would increase recip inertia and again increase crank torque variation, in particular during the ex/in period around TDC.

So, I suspect a lot more variation with HC pistons than with tuned exhaust. But I could be wrong. Trouble is, ain't much data available. 720 degree crankshaft torsional measurements tend to be closely held information, as are propeller vibration plots.

<<I'm just lookin' to learn something.>>

Me too.

Nice, there Dan-o.