Just how fast would a C model fly, if a C model could fly fast?

[Sabremech]

I’ve done a number of 3 point performance flights after my cowling mod and my 66 C comes in at a solid 154 ktas airplane. I’m going to install my Sabre Cowl Ver 2 on my bird for installation data and more performance flights. It will be interesting to see if I pick up a little more speed or if it’s reached it’s max potential. I have most of the speed mods and a 1900 SMOH engine with 500 hours since bottom inspection so it’s not a new engine. 
David

[0TreeLemur]

On 12/1/2019 at 11:01 PM, flyer338 said:

N78898 was one of the planes that fell withing the great Chevron bad fuel debacle of 1994 and wound up with a factory reman engine. I flew it down to Lakeport for Lasar to do the work; Paul Loewen flew me back in his E (I think it was a '65) and it trued at 170 knots at 6,500.

Here are a couple of pictures of 898:

 

I'm a little bit skeptical of the 170 KTAS C model and here's why.   Assuming a standard atmosphere, at 6500 ft, 170 KTAS would be 154 KIAS.  According to Sequoia Benchmark, with WOT (MP=24.4") and 2400 rpm, to achieve 170 KTAS, the drag coefficient in a Mooney with stock Hartzell propeller (87.5% eff.) can at most be 0.015.  Such a slick Mooney C does not exist?  According to the data in Sequoia, a M20J has a drag coeff measured of about 0.0168.  A M20C could hardly be lower, right?

From the data in Sequoia, M20J N1220G has a cruise speed at 6500' STP with 24.4" MP and 2400 rpm (70% POH pwr) of 163 kts.  To get the J up to 170 kts cruise, rpm must increase to 2630 rpm.   Who does that?     I'm calling B.S. on the 170 kt C unless they were cruising at much higher than normal rpm.

[David Lloyd]

Uhhh. Read that again, that was an E doing 170.  Still....

[flyer338]

Paul’s airplane was an E model. I doubt there is anyone, except possibly Roy LoPresti, more knowledgeable about getting Mooneys to fly fast. This was his personal airplane. I do not know how accurate the ASI was, but I had just flown that route in my plane, so I knew the winds aloft; I think what I reported was very close. I would sell my 201 and buy that plane in a heartbeat!

[flyer338]

I think the degree to which the elevator is in trail depends on the downforce necessary for level flight In the current configuration. The pictures are not from the speed trial posted. I was flying in formation with a C-182, and slow. The less downforce, the less drag. That is one of the reasons I reported the CG. I loaded the plane for a near limit aft CG for the speed trial on purpose.

[Pete M]

The cowls on the 64 and 65 (with eyelets) were narrower than later short bodies. The front cylinders and exaust often had clearance issues but the presented less frontal area. 170Ktas? Stock? I'm not so sure but it's certainly possible. Hot cam, the old hotter ig timing, massaged cylinders, inner gear doors and what not. Sure would like to know what he did.

[rbridges]

My C model routinely hits 200 knots with only one speed mod.

 

[chriscalandro]

I use presto logs. 

[0TreeLemur]

16 hours ago, David Lloyd said:

Uhhh. Read that again, that was an E doing 170.  Still....

I couldn't tell from the photo.  An E and a C are the same airframe.  I don't think the IO360 vs. O360 would make that much difference in cruise when connected to the same propeller.

[0TreeLemur]

2 hours ago, Pete M said:

The cowls on the 64 and 65 (with eyelets) were narrower than later short bodies. The front cylinders and exaust often had clearance issues but the presented less frontal area. 170Ktas? Stock? I'm not so sure but it's certainly possible. Hot cam, the old hotter ig timing, massaged cylinders, inner gear doors and what not. Sure would like to know what he did.

Must have been near-magic, but after all LoPresti was undeniably "the man" when it comes to Mooney aircraft and speed. 

[DXB]

47 minutes ago, 0TreeLemur said:

Must have been near-magic, but after all LoPresti was undeniably "the man" when it comes to Mooney aircraft and speed. 

These folks did even better when it comes to making an E model go fast, so it seems within realm of plausibility to me.  I think this bird is still flying somewhere in the hands of a private owner.

https://cafe.foundation/blog/185-mph-on-6-7-gph-cafe-mooney-for-sale/

[cliffy]

Just remember- a wax job is good for 10 knots!

[0TreeLemur]

10 minutes ago, DXB said:

These folks did even better when it comes to making an E model go fast, so it seems within realm of plausibility to me.  I think this bird is still flying somewhere in the hands of a private owner.

https://cafe.foundation/blog/185-mph-on-6-7-gph-cafe-mooney-for-sale/

Ok, thanks for sharing that link.   Now I see why my skepticism is unfounded.  That is so far from a stock airframe it is unbelievable.   I would bet that this CAFE Mooney can cruise at 170 with 75% power.

[DXB]

22 hours ago, PilotCoyote said:

Yes, come to think of it I do remember Rich saying that, and it does make sense. I think you just assigned me a science project for my short body...! At some point, when I have good weather again, I'd like to spend a little time flying the aircraft and seeing what configuration gives it best speed. Until then, I cannot be sure that vanity and aerodynamics might not go hand-in-hand. You certainly have me doubting my original idea though...

Please report your findings!

[bonal]

Wide range of performance for our C depending on how I fly I have seen 154 knots TAS down low pushing WOT 2500rpm at 4500 feet. A three heading gps flight at 8000 feet with two on board gave 149 knots and at 10500 feet with two and heavy fuel produced 140 knots true. Our C is nothing special has a few mods but no dorsal fin or even re positioned calipers so I have no doubt that a really clean fresh motor modded C could be a high 150 to low 160 knot airplane. But again it has a lot to do with how hard you want to push it. Cool winter weather makes a big difference as well, ours hates hot weather. Knot bad for 180hp with 1015 pounds of useful load. Short bodies are great little airplanes.

[gsxrpilot]

@0TreeLemur Think of it this way... an E is just a J with 10" less fuselage to drag around. 

An E with all of the same LoPresti mods that were done to the J, should be faster than a J. It's smaller, lighter, but with the same power plant. If I were not flying a turbo, I'd prefer a slicked up E over a J, no question.

[rbridges]

41 minutes ago, gsxrpilot said:

@0TreeLemur Think of it this way... an E is just a J with 10" less fuselage to drag around. 

An E with all of the same LoPresti mods that were done to the J, should be faster than a J. It's smaller, lighter, but with the same power plant. If I were not flying a turbo, I'd prefer a slicked up E over a J, no question.

well, you're just gonna have to suffer along with your 252.  

[Tcraft938]

On ‎12‎/‎3‎/‎2019 at 9:56 AM, cliffy said:

Belly panels?  Eh- put it up a little on jacks for room and take a small electric screw gun (know how to use it by breaking the screws loose first then hit the trigger) (and use a good NEW bit) and they all come off in about 15 mins. No big deal. I replace all the screws for new every 3 or so times off. Makes a big difference. Remember, all the screws down there are not the same. mark them with tape and pencil. 

You'll spend more time cleaning them than it took to get them off. Good time to wax them when they are off. 

Cliffy, dead on sir. Snow storm this weekend and my A&P said, I'm doing an annual on an E model and owner doesn't want to assist, has no problem if you do if you want to start your education early, it will save him some $ and you will be more efficient for your annual next month, saving you more $ and me more time.  He had me do very similar to what you said and it was not big deal, just some time and better me doing that simple work than paying him $80 per hour.  Took pictures of things before I undid it, separate baggies labeled for the screws, few drops of oil in the baggy to help clean and lube them and set the clutch real low so don't strip them.  He even had marks on his jacks for height and then wood blocks to go under the belly that were perfect to hold the belly pans in place to start the screws.  He works alone most of the time so he has a million tricks to get a two man job done by himself.  

My favorite question from him, "a couple of months ago you helped with a Piper Arrow, which plane was easier and gave better view of retract system and control surface linkages and then ask yourself based on your answer, as I fly out of here which plane am I more confident Ed saw the most of and verified?'   He smiled and then said, "yup Mooney's can be a PITA (pain in the axx) but they are a Brilliant PITA, everything else is a stupid PITA".  

My real lesson I think is to not worry so much about the horror stories and negative opinions about Mooney I have heard until I have actually experienced enough to form my own opinion.  

[Chessieretriever]

My 88 year old friend owns a '67 C that will do 160kts TAS every time we fly. He has all of the mods described before but uses a cowl that resembles the J. This guy has owned this AC since it was 2 years young and at the time he was Director of Maintenance for all 747s Worldwide at Pan American Airlines. As a result he did all of the mods himself and still "works" on his airplane every chance he gets. Here is a picture of N9738M in level flight with 3 on board at 11,500. I know that the air speed indicator was close as we had Airport radio hang a mercury bar on the pitot system and check how far out of "calibration" it was (it was off by a few 2 MPH). I have another friend who has a well equipped J and this C walks away from it every time regardless of load. Don't know exactly why. Cheers, Chessie.

[MBDiagMan]

My C was modded very much like the one in the OP and although it was never scientifically tested for speed I firmly believe that it was very similar.  If I hadn’t injured my shoulder I would still have it.  It was so much easier to fly than my F and solidly reliable.  I miss her a lot although she is in a good home.

[tigers2007]

You guys are making me feel bad. My much modded C drags along at 146Kts max.  Everything but the lower gear doors.  A full rigging is in order.  Maybe next year.

Okay. WTH. Mine trues out at 137kts with my Hartzell 3-blade. I need to serious rigging adjustment.


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[Hank]

1 minute ago, tigers2007 said:

Okay. WTH. Mine trues out at 137kts with my Hartzell 3-blade. I need to serious rigging adjustment.

Yes you do!! My C trues out at ~147 KTAS . . . .

[0TreeLemur]

 

27 minutes ago, tigers2007 said:

Okay. WTH. Mine trues out at 137kts with my Hartzell 3-blade. I need to serious rigging adjustment.
 

 

I've been keeping track of reported TAS values for C models since I've been lurking here on MS.   It seems that the average is about 143 kt, with a std. dev. of 2 kts, for various degrees of airspeed mods.  Having 3 blades is inescapably known to knock a couple of kts off cruise speed.   Power setting and those habits are really important, and I think that accounts for a fair bit of the variance.   This small variance caused by the various speed mods pales in comparison to the average headwind that I fly against...  So, I'm happy with what I get.  

Remember, power=drag*airspeed.   Planes having similar power, will fly at the speed that similar airframes get. 

When considering drag, there is no magic, like there is in the case of lift.

[cliffy]

One item no one ever mentions is?  ???????     Wait for it-

Where is the CG sitting when the speed checks are done? Also,  What is the Gross weight?

None of the speeds are comparable model to model UNLESS the CG and the weight is the same. Think "trim drag".

How much from full FWD to full AFT? Might be interesting to see, light to full gross?

Because I'm not dainty :-) My CG is always way forward with up trim evident because of it, lots of up trim drag

My D (with a 3 blade) is a rock solid 137 - 139 KTS TAS, Measured many times, 

I'll bet if we all calculated our CG and Weight then gave the TAS we might have a better idea of what is normal model to model. 

I've just moved my battery to the back and calculated the CG shifted 1 1/4 inches aft, I"ll be weighing mine on scales next week to see how accurate my calculations were. 

If your flaps and ailerons match in cruise and the aileron tip weights are near fared you're pretty close in rigging (hands off of course).  

Later this year (when it warms up a bit) I'll be doing some speed checks with weight in the baggage compartment trying to get a full aft CG position to check with.

[ArtVandelay]

Also OAT and humidity, both affect horsepower...those of us in the southeast climate are at a disadvantage when it comes to bragging rights.