Performance M20C with Hartzell 3 blade propeller HC-C3YR-1RF/F7282

[Urs_Wildermuth]

We just got this prop installed. Due to the power flow exhaust we also have, we find that we are massively restricted in power settings, as there is a note to avoid continous operation between 1900 and 2350 RPM with MP smaller than 22".

Question: Does anyone have performance tables for this configuration? I just looked at the M20C POH and it is e.g. not even possible to determine a 65% cruise regime if you are limited to run the prop above 2350 RPM. Likewise, there are no data on fuel flow or similar things.

How do those who run this prop on the M20C calculate their performance? Just by experience? Or is there some documentation for this?

[1967 427]

I don’t have that prop, but I believe that the original RPM restriction was due to harmonics generated by the original prop.  I think you should look into that new Hartzell prop, I think the RPM restriction may not apply.  Don’t know for sure, I would do some research if I were you.  Only a pp’s thoughts

[cferr59]

How does the Powerflow restrict you? I have a C with a Powerflow and the RPM restriction is from the prop, not the exhaust.

[Hank]

@Urs_Wildermuth, I'm not sure offhand which Hartzell 3-blade prop I have (it was there when I bought the plane), but my prop restriction is 2000-2250. Time to look for a picture!

I used to set power by the Performance Tables, now i pretty much use Key Number = 46 and go with it.

Oh, there is a placard to avoid 1950-2350 below 15" though. 

1970 M20-C, Hartzell 3-blade, normal exhaust 

[ShuRugal]

2 hours ago, Hank said:

Oh, there is a placard to avoid 1950-2350 below 15" though. 

landing prohibited.

[Hank]

1 hour ago, ShuRugal said:

landing prohibited.

No, it says "avoid continuous operation below 15 inches Hg between 1950 to 2350 RPM" which does not affect my ability to land, either at the 3000' obstructed field I was based at for seven years, or at a 2000' grass field.

[Urs_Wildermuth]

The STC gives two restrictions:

Avoid continuous operatio below 15 inches HG between 1950 and 2350 RPM.

If Powerflow STC ... for a tuned exhaust is installed:

Avoid continuous operation below 22 inches HG between 1950 to 2350 RPM.

The latter imho is a total killer, as it means no more long range cruise and loss of most of the performance information we have in the POH!

If we have to fly 2400 RPM all the time, 65% power is not possible below 7500 ft using the POH, let alone 55% or any other power setting. That means pretty much no long range cruise, worse range and so on.

There is also no information in the STC the way I see it as to what performance factor the new prop has. So basically we have to testfly this?

I am extremely angry at myself (and the others involved in the purchasing of this prop) for not seeing all this before I ordered, i would never have ordered this prop with these restrictions. But now we have spent 20k$ for the darn thing, we don't have money to throw it out and buy another.

And without validated performance tables, how are we supposed to operate this airplane? The thing I see coming is that we have to testfly it in all configurations in order to find out what FF and TAS we get and basically recreate the performance section. Before that, we can't release the plane to the other pilots who fly it as well.

I honestly wonder how this STC could have been approved without all this vital data.

So I still am asking the same question: Those who fly this prop with or without the Powerflow exhaust, what performance tables do you use? Standard POH are obviously for the 2 blade. So we are basically on experimental ground, but with a certified airplane.

 

 

[Hank]

Urs, again no Power Flow on my C, just the 3-blade Hartzell. I use the Performance Tables in my Owners Manual and / or the Key Number approach, but have settled for mostly these:

< 4000 msl:  23" / 2300

4000-7500:  22" / 2400

>7500:  WOT- / 2500

For the latter, I back the throttle off slowly until the MP needle wiggles, hoping that it creates enough turbulence in the carb from the cooked throttle plate for improved fuel atomization and more uniform mixing and distribution. 

Even with the additional Power Flow restrictions, this should work for you. I get 145-148 KTAS, with.block fuel burns as low as 8.5 gph when cruising at 8000 or higher.

What do you think? What long range cruise settings do you prefer that you are losing? 

Any time your MP + RPM = 46 or less, you are at 65% power or less.

[Urs_Wildermuth]

@Hank,

My problem is, the POH does not even give figures for 65% at 2500 and 5000 ft for 2400 RPM. So how can I e.g put a proper planning together at 65% in those altitudes. If I read the performance part of the manual and look for 65% at 2500 or 5000 ft there is simply nothing there.

The long range cruise figures we had with the 2-blade prop were based on 2300 RPM and optimized figures out of the tables, basically see where you get the largest range with least consumption and within a reasonable time. The 1800RPM cruise does not make sense unless you are up for an endurance record, as the time you fly (and with it get to time limits TBO, 50 and 100 hour checks faster) also is part of the aim to fly efficient. From what I've seen so far, 2400 RPM in the lower range figures ups the consumption, therefore decreasing range.

But all of the stuff in the POH is with the 2 blade prop. So what about the 3 Blade ones? I have no table which even tells me it has no influence on the POH figures (apart from the restriction) so in fact, I have no document available to tell me the performance of this airplane. So what do I feed into the 65 and 55% sections in the flight planning computer? On what basis do I do my fuel calculation? 

Which to me means, we have to go out there and figure them out with test flying.

With Fuel prices up to 12 $ per gallon and rising, simply putting the pedal to the metal does not work anymore, at least not for me. We always flew 65% below 1 hour of flight and LRC whenever above it. Only that with 2400 RPM, the figures aren't even there to start calculating.

[chriscalandro]

If you only go to places with 12$ gas you aren’t very good at planning anyway. In this case max cruise is the least of your problems. 
 

you should easily be able to find gas for half that price, which tells me you’re an extreme exaggerator. 
 

Gas at signature at LAX is 10$

Edited July 13, 2022 by chriscalandro

[Rwsavory]

6 minutes ago, chriscalandro said:

If you only go to places with 12$ gas you aren’t very good at planning anyway. In this case max cruise is the least of your problems. 
 

you should easily be able to find gas for half that price, which tells me you’re an extreme exaggerator. 
 

Gas at signature at LAX is 10$

He's in Switzerland. lol

[Fly Boomer]

7 minutes ago, chriscalandro said:

you should easily be able to find gas for half that price, which tells me you’re an extreme exaggerator. 

You might want to look at where he is before you run your mouth.

[Urs_Wildermuth]

@Hank and whoever else flies with this prop:

What static and what rolling take off power do you see at Max Take Off Thrust?

At the test flight we got 25" and 2500 RPM with all the levers full forward. OAT was about 27 degrees Centigrade at 1400 ft, so about 2000 ft DA.

[Hank]

19 minutes ago, Urs_Wildermuth said:

@Hank and whoever else flies with this prop:

What static and what rolling take off power do you see at Max Take Off Thrust?

At the test flight we got 25" and 2500 RPM with all the levers full forward. OAT was about 27 degrees Centigrade at 1400 ft, so about 2000 ft DA.

The prop shouldn't affect your manifold pressure, it should be unchanged from before. I live nice and low, my home base is 685 msl. I pretty much always have 27" available there, and I would be surprised to see noticeably less than 2700 on takeoff. Not sure of static RPM, though, and the forecast for the rest of the week is not conducive to even short test flights. Sorry, Urs . . . I'll report back when I can.

P.S.--this time of year, 27ºC is pretty cold! We're supposed to be cooling off to ~95ºF [35ºC] this week.

[Hank]

1 hour ago, Urs_Wildermuth said:

@Hank,

My problem is, the POH does not even give figures for 65% at 2500 and 5000 ft for 2400 RPM. So how can I e.g put a proper planning together at 65% in those altitudes. If I read the performance part of the manual and look for 65% at 2500 or 5000 ft there is simply nothing there.

My Owners Manual gives power settings at 2500 and 5000 msl covering 2400 RPM.

There is nothing for 65% at 2300, it's either 21/2300 for 63.1%, 5:46 or ~835 sm or 22/2300 for 67.3%, 5:22 or ~800 statute miles.

Or try 21/2400 for 65.2%, 5:34 or ~820 statute miles.

Flying higher is always better. This is what I see for 5000 msl:

I use 22/2400 = 72%, 4:56 or ~770 statute miles. But I don't fly this for long trips.

Again, 21/2300 for 65.5%, 5:30 or ~825 statute miles.

I much prefer this at 10,000:

Cruise at 20/2500 or 61.0%, 5:55 or ~890 statute miles.

Distances are all approximate, because I don't want to copy the two distances for Gross weight and 2200 lbs, but approximated the center point between them [typically only 25 mile difference anyway]. Down low, there's just not a lot of difference.

FYI, my Owners Manual from my 1970 C is in the Downloads section if you want to look up anything else. I'd be curious if there's much of a difference with your own 1965 version.

[chriscalandro]

1 hour ago, Fly Boomer said:

You might want to look at where he is before you run your mouth.

You might want to shut yours. Do the math. It still doesn’t add up. 

Edited July 13, 2022 by chriscalandro

[Urs_Wildermuth]

3 hours ago, Hank said:

I pretty much always have 27" available there, and I would be surprised to see noticeably less than 2700 on takeoff.

Thanks. That confirms what I think. That prop's governor needs some talkin' to.

 

2 hours ago, Hank said:

There is nothing for 65% at 2300, it's either 21/2300 for 63.1%, 5:46 or ~835 sm or 22/2300 for 67.3%, 5:22 or ~800 statute miles.

Well yea, but that means you can calculate or at least estimate what 65% is as it is between 63.1 and 67.3. On the 2400 table the lowest you get is 70% if I recall right. So what if I need a setting for 65 or 55% i.e. to feed a flight planner? We can't very well use our former airplane profiles otherwise that prop won't last very long, they tend to get bent when people run out of fuel 200 NM before their destination and land in a cornfield! And as our British friends point out, that is NOT Cricket.. and there are cheaper ways to make popcorn.

 

2 hours ago, chriscalandro said:

You might want to shut yours. Do the math. It still doesn’t add up. 

Hey ya all, keep it cool. Yea, I am in Europe and within that in Switzerland. Avgas prices here have gone beyond the current rate of 3.26 CHF per Liter (after coming down from more). Soo, one USG last time I looked was 3.78 liters, consequently a US Gallon costs 12.32 CHF per USG. And the US Greenback is noted at 0.97 to the Swiss Franc right now, so that makes it $12.70 per USG. Today. Thankfully I only need to fuel on Friday

But seriously, I think some here have gotten their boots on the wrong way about this before. European Fuel prices are a totally different league than in the US. Why do you think we fly Mooneys and why do you think Tesla is selling way too many cars over here. I fuelled normal 95 grade autofuel two days ago for $9.13 per Gallon.

Before Uncle Vlado threw his wobbly prices were somewhere in the 1.70 CHF for automotive fuel and 2.30 for Avgas, so if you do your math right, that would be between 6 and 9 $ per USG respectively. We are used to it, mortage our houses and carry on flying. Oh, yea, and I got a 1300 USG heating oil tank buried under my back garden which I need to fill. I just hope the oil speculation will go back to pre-Ukraine levels before I have to do that. Otherwise, another mortage...

They all but had to revive me some years back when I filled up my rental car in Miami after 2 weeks of driving on one fuel tank. Swiss and Europeans tend to have nervous breakdowns and google searches for Greencard Lotteries at gas stations in the US. Chill. It's normal. Enjoy it while you can.

Anyway, there is one good thing about this bickering about European prices here... I can do the math between liters, gallons and between CHF and USD in my sleep now.

 

[Jcmtl]

On 7/12/2022 at 4:10 PM, Urs_Wildermuth said:

We just got this prop installed. Due to the power flow exhaust we also have, we find that we are massively restricted in power settings, as there is a note to avoid continous operation between 1900 and 2350 RPM with MP smaller than 22".

Question: Does anyone have performance tables for this configuration? I just looked at the M20C POH and it is e.g. not even possible to determine a 65% cruise regime if you are limited to run the prop above 2350 RPM. Likewise, there are no data on fuel flow or similar things.

How do those who run this prop on the M20C calculate their performance? Just by experience? Or is there some documentation for this?

i don't really understand the problem.  Why can't you cruise at WOT and 2400 rpm at 8k and above?   Are you saying you're scared to lean because you're not sure about being below 65% power?   Just lean anyway and monitor your temps.  

[Urs_Wildermuth]

1 hour ago, Jcmtl said:

i don't really understand the problem. 

How do you want to plan a flight, produce a legally acceptable Operational Flight Plan and fuel calculation if you have no idea about the speeds and consumptions?

1 hour ago, Jcmtl said:

Why can't you cruise at WOT and 2400 rpm at 8k and above? 

WOT at 8000 ft means some 75% power with 11 GPH. We usually cruise at 65% power with 9 GPH. At that altitude this would be somewhere around 20" and POH TAS of 140 kt. 

1 hour ago, Jcmtl said:

Are you saying you're scared to lean because you're not sure about being below 65% power? 

No, heavens no. We lean very agressively from the start.

 

I am a former flight dispatcher and I get very uneasy about going into undocumented territory when it comes to flight planning. Not to mention that there are no indications about the speed loss the 3 blade prop causes vs the POH TAS. I am now hearing 8 to 10 kts, which would be horriffic. Basically turns a M20C into a PA28. Also we do operate the airplane (any airplane we operate) strictly by numbers out of the POH, not just some guesswork.

The way I see it we will now start using a 10 kt performance penalty and increase final reserve to 1.5 hours on flight planning for the time being while we have to testfly the airplane to figure out what it actually will do. As nobody appears to have legit figures I don't see any other way. This about halfs the range of the airplane for the time being, but with no figures available, we basically have to start as if we had an undocumented experimental on our hands.

Clearly I was totally naive and stupid when it comes to the impact of this prop change. I expected some improvement in noise fees and I really did NOT expect loosing 10 kts of speed. We will see, most probably we will have to change back to a 2 blade prop in the not too distant future.

[Rwsavory]

I have the same prop on our 1965 C. I cruise at about 140 knots and average 10 gph. If I were you I wouldn’t worry so much. But if you really want to worry, get yourself a fuel totalizer and carry on.

[Raptor05121]

I have this prop but no PF

I run WOT/2500RPM when im going somewhere

If I'm staying local I do low/slow 23 squared.

[Andy95W]

2 hours ago, Urs_Wildermuth said:

I am a former flight dispatcher and I get very uneasy about going into undocumented territory when it comes to flight planning. 

I completely understand that rationale.  I appreciate having a dispatcher in my day job (I fly a very advanced jet) who looks at all possibilities and provides fuel burn numbers that are accurate to within 1/2 of 1%.  Makes me feel good knowing that someone like you is looking out for us.

But we’re not talking about a FADEC controlled jet that has been so thoroughly checked and tested that it is extraordinarily accurate and predictable.

We’re talking about a modified 57 year old airplane that never had an accurate POH, but instead an “Owners Manual” that wasn’t regulated by the FAA or EASA.  Instead of digital engine control, it has a carbureted O-360 that, in essence, throws avgas upwards into the induction tubes and, if lucky, some amount of it will get sucked into a cylinder through a carbon-encrusted intake valve and ignited with sparks from a magneto that was designed almost 100 years ago.  Unfortunately, we’re all looking for digital accuracy in an old-fashioned analog world.

Hopefully you can do some testing and provide some real-world accurate numbers to help others with your engine/prop combination.

[Hank]

Urs, again, at altitude my C with this prop, 201 windshield and guppy mouth closure, runs 145-148 knots true, depending upon conditions--with recent OATs around 74°F (23°C) at 8000 msl, at the low end of this speed range. My Owners Manual calls for about 162 mph = 141 knots.

So I am actually 4 knots FASTER than book.

I don't know what rumor-monger's horrendous advice you are listening to instead of those of us with this prop on M20-C airplanes, but it's getting old having our real-world experience ignored and the worst of the worst fake numbers thrown back up as gospel truth.

You do what you need to do. This is the last advice I have for you. It's your plane, your time and your money, and no one here on MS can make you read with even one eye what we wrote from our real world experience. Go ahead, plan to fly Cherokee speeds with Bonanza fuel burns, and only fly Piper Cub legs lest the Earth rise up to smite your pig of an airplane. I plan my flights, with this same prop but no stupid Power Flow exhaust, using the Performance Tables in the back of my Owners Manual, as printed by Mooney in 1970. And I consistently meet or beat it.

So far, I’ve flown 4:45 twice, around 10,000 msl at WOT- /2500 and refueled just over 41 gallons. Recently I also went a similar time at 8000 on 2-3 gallons more, in and out of cloud tops and rain.

But you ignore this, plan on no more than 130 knots (the dumbest performance expectation I've ever heard of for any Mooney ever), at 11-12 gallons per hour (because you don't know how to lean the mixture?), and for God's sake land every 300 miles or so (because you really like walking around unfamiliar airports and paying fees for unnecessary landings).

It's bedtime, I was up at 0400 this morning for work. I just don't understand how you can ask for advice here then ignore everyone who offers it while listening to someone local who is filling your head with lies, distortions and garbage.

[Urs_Wildermuth]

9 hours ago, Hank said:

Urs, again, at altitude my C with this prop, 201 windshield and guppy mouth closure, runs 145-148 knots true, depending upon conditions--with recent OATs around 74°F (23°C) at 8000 msl, at the low end of this speed range. My Owners Manual calls for about 162 mph = 141 knots.

So I am actually 4 knots FASTER than book.

Ok, thank you, that is very good to hear.

I have not been looking at rumours but at the actual numbers from our test flight, which was done with 2300 RPM as we did not get the information about the 2350 RPM limit in time.

Cruise: (All DA and TAS)
75% TAS at 5000 ft between 138 kt with FF 10.6 GPH. According to the book it should be 146 kt at this FF
65% TAS at 5000 ft we got 127 kt. FF 9.2 GPH. According to the book, it should be 136 kt at this fuel flow.
75% TAS at  10'000 ft we got 140 kt. FF 10.6 GPH According to the book, it should be 153 kt.
65% TAS at 10'000 ft we got 135 kt, FF POH9.2 GPH. According to the book, it should be 141 kt.

This gives a consistent 6 to 8 kt less than book speed. And while it never reached fully book speed also before, the differences were less pronounced, max 1-2 kt at 75% and pretty much spot on at 65%.

We also did a test with WOT 2500 RPM at 6000 ft and got 148 kt at around 12 GPH.

The airplane is equipped with a Shadin Miniflo fuel computer linked to the GNS430W. No problem there. We also have an Aspen PFD so we can read off TAS direct and a Davtron instrument which reads DA direct. That is quite comfortable for what we need to do.

This morning, maintenance bench tested the RPM gauge and found it accurate. A run up at DA 2000 ft resulted in 2550 RPM and 25" HG. We are all clear that this is not enough, so we are talking to the prop shop how to proceed.

I am not ignoring anything, just the opposite, I collect all the values you guys give here with huge interest. And your report of being actually 4 kt above POH speeds tells me, that something really has to be checked with my airplane. It has the power flow exhaust, which in my experience has been largely responsible for us making book values with the 2 blade prop, so now getting values which I can't explain bothers me.

I spent quite some time last night to produce a preliminary power table taking into account the new situation and now we will testfly the airplane against that table at 2400 RPM and 2500 RPM to see what happens.

9 hours ago, Andy95W said:

 Unfortunately, we’re all looking for digital accuracy in an old-fashioned analog world.

Well, incidently, I have been flying this plane since 2009. The process I am going through right now is not new to me, other than up to today, I always had POH values to fall back on, to at least give me some base line to work from. During this time we found out quite a few snags which cost us performance or we thought it did, such as a faulty K-Factor in the Shadin which gave us a wrong fuel flow, such as an RPM gauge which overread by 50 RPM, such as a wrong conversion factor between mph and kt which got introduced into a flight planner and affected thousands of users, few ever noticed and even less noticed it's gone by now. Some even claimed they did reach the wrong KTAS figures but that is down to bragging rights I think.

What I can say is that if it is flown with some sort of precision, on AP and power set according to thee book, the airplane, like most, pretty much delivers a very constant performance. For economic reasons we always flew the airplane at 65% and sometimes 55% if we had to play range vs speed and it delivered with no less precision than the A320/330 and MD11's I used to dispatch. BUT, the main thing is, garbage in, garbage out. We have great flight plan systems like Foreflight and similar, which have accurate in flight winds e.t.c. but often profiles which were done with less than desirable accuracy. Add to that, each airplane has its particular performance deviation from the book, some better, many worse. I call this a performance factor and we had those in the Airbusses and MDC's as well. Individual fleets could vary up to 1-2 %, which in a 100 ton airplane is quite a lot. I've done some adapted tables for friends who fly Mooneys and other airplanes, if you really put the work in and get flight data back, those things are not worse than today's airliners with all their FADEC's and fancy displays.

You'd be surprised how many folks don't even know the real meaning of TAS vs IAS, can't work out a Fuel Flow even if it is displayed right in front of them and are simply uninterested in the nice features such as fuel computers e.t.c. we all have. Well, part of my fun I have is to be able to really plan my flights properly and to be able to fly them in such a way that pre-planning results work out in a reasonable fashion. I find that this way I can go much more towards the performance limits of this wonderful airplane than people who simply go fuelling every two to 3 hours no matter what. I recall vividly how we got a friend of mine out of a very short runway where one of his pilots had landed with a tech problem after they had thought to use a helo to get it out, but in the end the POH was right and it cleared the far end comfortably, after waiting for a day for conditions to be just right.

For me, a cross country flight is successful if it arrives within a couple of minutes of EET and +- 1 USG of either fuel remaining or used on the operational flight plan. Flying in an environment where most airports are PPR and many (including my homebase) give out tight slot times of +-15 mins you have to hit or divert, you can't afford not to know your performance.

  

9 hours ago, Andy95W said:

We’re talking about a modified 57 year old airplane that never had an accurate POH, but instead an “Owners Manual” that wasn’t regulated by the FAA or EASA.

Well, with enough effort, you can make an actual POH which works, has the correct stuff inside and can even be approved by the competent authority. I've pretty much done this for my plane with the performance part, (well I thought I did, back to square one now) and procedures, I might do it for the actual systems and equipment too. The stuff is out there, it just takes someone to organize it and put it into writing.

 

 

 

[Urs_Wildermuth]

1 minute ago, bluehighwayflyer said:

 Hey, on another topic, were you able to procure and install a new down lock block for your landing gear?  

Yes, both up and downlock. I actually had the chance to operate them today on the blocks and they work superbly. I also got the cowl closure, but that one will have to wait to be fitted until later. It is more work than I tought and the shop can't accomodate it right now.

 

2 minutes ago, bluehighwayflyer said:

I admire your search for the perfectly planned and executed flight, Urs.  It is unobtainable, of course, but we can all relate to the quest you are on.

It's not any where close as unobtainable than you think and once you are set up with a proper flight planner and really good and verified data in it, it's a very easy thing to do just that.

I used to have some fun with a friend of mine whom I visit by plane from time to time, after departure I text him my ETA and he will turn up exactly on time to verify. So far, the only time I got in there late was due to holding at destination. And so far I've never yet had to get even close to my final reserve fuel, even though we have done 5 hour flights with the airplane.