M20J 201 Model Speeds

[MooneyPilot145]

I have a 1977 M20J 201 with an IO-360-A3B6D. This model boasted 201 mph back in its time, but I average about 150 mph groundspeed (~135 kt true). It trims out nice in flight but just curious what others see.

I've also noticed the elevator has a natural downforce to it because of the bungee springs in the back. That tension decreases SOME when the tail is trimmed, but curious if anyone knows why those springs are there, and if it's possible it could be causing any drag in flight?

Any other mods or tweaks to improve speed or is what i am seeing normal?

[ohdub]

What power setting and fuel flow are you using to get the 135KTAS?

Steve

[Ragsf15e]

Definitely need your power settings, but at anything “normal”, that seems wrong. I plan for 145ktas in my F when ROP and 138 LOP when between 7-10,000’. You should be 10kts faster.

[201Mooniac]

It does seem slower than normal, I flight plan 155 kts when flying at max performance (between 9-10 gph depending on altitude) and 145 kts when running economy setting (8-8.5 gph).  At my max performance setting I can typically see 160 kts.

[Mooney Dog]

31 minutes ago, MooneyPilot145 said:

150 mph groundspeed (~135 kt true)

groundspeed isnt true airspeed. Groundspeed is true +/- winds.

 

My E model easily gets 145 true at 2400rpm 23mp around 5,000ft. a J should be getting better if not for the same as that. 

[MooneyPilot145]

21 minutes ago, ohdub said:

What power setting and fuel flow are you using to get the 135KTAS?

Steve

 

14 minutes ago, Ragsf15e said:

Definitely need your power settings, but at anything “normal”, that seems wrong. I plan for 145ktas in my F when ROP and 138 LOP when between 7-10,000’. You should be 10kts faster.

Flying at 5500 and 6500 yesterday. 2400 RPM, 21" MP, 50deg ROP, ~140ktas

Even at WOT, ROP, 2500 rpm at any altitude I've not seen anything over 145ktas.  Does the 175ktas (201 mph) actually exist?

[EricJ]

I have a 77 J, totally stock as far as far as aero goes, and I typically see 150 kts in general at WOT and 2500 rpm.   It'll do faster down low (5-6k ft), and obviously slower if the power or fuel is pulled back.

On mine the cowl flaps make a big difference.   If I'm slower than usual it's often because I forgot to close them fully.

[Mcstealth]

Bad Airspeed indicator?

 

[Ragsf15e]

21 minutes ago, MooneyPilot145 said:

 

Flying at 5500 and 6500 yesterday. 2400 RPM, 21" MP, 50deg ROP, ~140ktas

Even at WOT, ROP, 2500 rpm at any altitude I've not seen anything over 145ktas.  Does the 175ktas (201 mph) actually exist?

Talk me through exactly how you’re determining your true airspeed.

[EricJ]

31 minutes ago, MooneyPilot145 said:

Does the 175ktas (201 mph) actually exist?

At sea level on a perfect day with a brand new airplane as interpreted by a marketer...maybe.   

[elimansour]

That does seem a bit slow.  In my J, 75% (2500RPM/ 25in) will typically yield 160kts and 65% (2400RPM/ 23in) around 155kts. 

[Bolter]

45 minutes ago, MooneyPilot145 said:

 

Flying at 5500 and 6500 yesterday. 2400 RPM, 21" MP, 50deg ROP, ~140ktas

Even at WOT, ROP, 2500 rpm at any altitude I've not seen anything over 145ktas.  Does the 175ktas (201 mph) actually exist?

That is very close to the IAS to TAS difference for that altitude and good performance.  Depends on the temperature at those altitudes.  How are you calculating KTAS?  140 KIAS is very close to what I would see on my J when my KTAS was 155-158 KTAS.

And I may get to be the first in this thread to point out that 50°F ROP is a terrible place to run the engine.  Ignore what the manual says.  That is the point of peak internal pressures.  Speaking in very broad strokes, if you are over 65% power, you should be 100F ROP.  Your CHT's may have been a little high.  If you are using a factory single point EGT and CHT measurement, then you have no idea if the other cylinders are hot/cold or lean/rich, which is why many owners install the engine analyzers.  

-dan

[ArtVandelay]

I have a 1977 M20J 201 with an IO-360-A3B6D. This model boasted 201 mph back in its time, but I average about 150 mph groundspeed (~135 kt true). It trims out nice in flight but just curious what others see.
I've also noticed the elevator has a natural downforce to it because of the bungee springs in the back. That tension decreases SOME when the tail is trimmed, but curious if anyone knows why those springs are there, and if it's possible it could be causing any drag in flight?
Any other mods or tweaks to improve speed or is what i am seeing normal?

I assume you mean 150knots, cause 150 mph is ridiculously slow.

The elevators normally droop at little in cruise flight.

I can do 150knots on 8.5gph above 8000’.

Speed depends on power, so engine may not be making full book horsepower.

Horsepower depends on OAT and humidity. I gain about 7 knots when I get out of the southeast higher humidity and higher temperatures.

[A64Pilot]

1 hour ago, MooneyPilot145 said:

 

Even at WOT, ROP, 2500 rpm at any altitude I've not seen anything over 145ktas.  Does the 175ktas (201 mph) actually exist?

I think it does, my J is heavy, every possible avionics there was in 1981 even a radar altimeter and storm scope as well as the Century 41 autopilot that I’ve heard is 35 lbs?

I can get as in have gotten 168 kts true at 500 MSL at takeoff power, meaning of course ram air open 30” MP, full rich and 2600ish rpm, I need to one day adjust the prop so I get 2700. I was at full fuel and I’m 250. I was burning 19 GPH too.

So take a new green airplane, no avionics to speak of, light weight pilot and just enough fuel for the speed runs I feel sure there is 7 more kts in there. Is that realistic cruise? Of course not, but I don’t think they were saying cruise, just that on a good day they could get one to 175 kts.

However I can cruise 155 kts pretty easily, run it hard maybe close to 160, but 155 is a sure bet.

To get actual real speed you need to do an airspeed calibration run, there are too many errors in calculating true from indicated.

This ought to work, we used to fly ground courses between set point and time them which was a PIA, Dr. Ralph Kimberlin wrote a procedure to use a GPS that the FAA accepted that seems very similar to what I attached.

Edited May 23, 2022 by A64Pilot

[Hank]

@MooneyPilot145, your numbers are low for two reasons:  you're using Indicated Airspeed, not True, along with ground speed which includes effects of the wind, and you're at reduced throttle, 21". 

Why so little throttle?

My C, 180hp with a carburetor, will give 145-148 knots true depending upon my load and the conditions, at 8000 msl, where I generally have 22"/2500.

So my questions are simple:

• Why only 21"?
• How do you figure 135 KTAS?
• Where did you find this power setting?

[201er]

2 hours ago, MooneyPilot145 said:

Does the 175ktas (201 mph) actually exist?

Have you checked the POH under what circumstances they claim this speed? It’s certainly not at those economy cruise settings or altitudes you’re using.

[Hank]

47 minutes ago, 201er said:

Have you checked the POH under what circumstances they claim this speed? It’s certainly not at those economy cruise settings or altitudes you’re using.

My C reaches max speed, right at or near book speed, at 1000 agl, WOT, 2700, full rich. That's 165 mph. In reasonable cruise, I indicate 140-145 mph, and have 145-148 knots true.

Edited May 24, 2022 by Hank

[Fly Boomer]

16 hours ago, MooneyPilot145 said:

Does the 175ktas (201 mph) actually exist?

Not if your airplane has paint, interior, all the seats, more than 10 gallons of fuel on board, radios, or instruments.  Or if you weigh more than 135 pounds.  Also, the 231 and 252 suffer from similar fantasies.  The 252 might do 252 with all the previously named conditions and flying level at 28,000, but not under any "normal" conditions.  Those numbers came from the Marketing Department.  According to Bob Kromer (test pilot) Marketing had already decided that they were going to call it the 252, and he needed to figure out a way to get one to go that fast.  That's how he ended up at 28,000 feet.  He said he would never do it again.  If your oxygen has a hiccup, you can't get down while you are still conscious.

[1980Mooney]

9 hours ago, MooneyPilot145 said:

I have a 1977 M20J 201 with an IO-360-A3B6D. This model boasted 201 mph back in its time, but I average about 150 mph groundspeed (~135 kt true). It trims out nice in flight but just curious what others see.......

Any other mods or tweaks to improve speed or is what i am seeing normal?

The M20J is basically an "F" with all the speed mods that make economic sense.  From Flying Magazine  https://www.flyingmag.com/aircraft-pistons-magic-mooney-201/

"It all comes down to drag reduction. Mooney engineers had seen the potential for aerodynamic improvements of the M20F, but it wasn’t until Roy LoPresti joined the company in 1973 that the ball got rolling.

“It was the first thing Roy did when he got there,” said Bill Wheat, who has thousands of hours in Mooneys and worked as a test pilot and engineer for Mooney for 53 years. 

Several key modifications contributed to the increase in speed. Wheat said the engine cowl redesign added about 8 mph, the sloped windshield also added about 8 mph, the inboard gear doors added about 5 mph, and the gap seals, flap hinge and empennage fairings added another 1 mph compared with the M20F.

LoPresti also fitted the M20J with new sculpted wingtips in 1981, although no speed improvement was seen with this modification. However, Wheat said the square wingtip design of prior M20 models produced turbulence at the outboard 10 to 12 inches of the ailerons. LoPresti’s wingtip design made a “noticeable improvement in the handling” by making the airflow over the ailerons smoother, which reduced the control wheel loads and created a faster roll rate, Wheat said."

[1980Mooney]

10 hours ago, MooneyPilot145 said:

I have a 1977 M20J 201 with an IO-360-A3B6D. This model boasted 201 mph back in its time, but I average about 150 mph groundspeed (~135 kt true). It trims out nice in flight but just curious what others see.

I've also noticed the elevator has a natural downforce to it because of the bungee springs in the back. That tension decreases SOME when the tail is trimmed, but curious if anyone knows why those springs are there, and if it's possible it could be causing any drag in flight?

 

[1980Mooney]

9 hours ago, MooneyPilot145 said:

Flying at 5500 and 6500 yesterday. 2400 RPM, 21" MP, 50deg ROP, ~140ktas

Even at WOT, ROP, 2500 rpm at any altitude I've not seen anything over 145ktas.  Does the 175ktas (201 mph) actually exist?

Per that same article in Flying Magazine again... "A published flight test evaluation made by the Mooney Aircraft Pilots Association (MAPA) produced 162 knots true airspeed at level flight at 7,000 feet with full throttle and 2,500 rpm, burning about 11.5 gph."

First you should fly a box and average the four GPS speeds.  If you are not getting book speed then you need to look at the engine, the prop and the rigging.

Engine

• Compression, Spark plug condition, fuel metering (nozzles/injectors) can all effect your actual horsepower.  Do you have an engine monitor to verify individual cylinder temps? 

Prop

• Are you able to get full book RPM on the prop?

Rigging, 

• During Annual, when your mechanic does the landing gear swing test you should observe the landing gear in the retracted position - ensure that the gear are fully retracted and that the doors fight flush and tight.  Also make sure the nose gear doors are fully closed.
• Has the rigging of the flight control surfaces been checked ever since it left the factory? 

 

[ArtVandelay]

The M20J is basically an "F" with all the speed mods that make economic sense.  From Flying Magazine  https://www.flyingmag.com/aircraft-pistons-magic-mooney-201/
"It all comes down to drag reduction. Mooney engineers had seen the potential for aerodynamic improvements of the M20F, but it wasn’t until Roy LoPresti joined the company in 1973 that the ball got rolling.
“It was the first thing Roy did when he got there,” said Bill Wheat, who has thousands of hours in Mooneys and worked as a test pilot and engineer for Mooney for 53 years. 
Several key modifications contributed to the increase in speed. Wheat said the engine cowl redesign added about 8 mph, the sloped windshield also added about 8 mph, the inboard gear doors added about 5 mph, and the gap seals, flap hinge and empennage fairings added another 1 mph compared with the M20F.
LoPresti also fitted the M20J with new sculpted wingtips in 1981, although no speed improvement was seen with this modification. However, Wheat said the square wingtip design of prior M20 models produced turbulence at the outboard 10 to 12 inches of the ailerons. LoPresti’s wingtip design made a “noticeable improvement in the handling” by making the airflow over the ailerons smoother, which reduced the control wheel loads and created a faster roll rate, Wheat said."

Not entirely correct. The J also got an improved intake (and maybe exhaust?) that made the ram air extraneous and was removed in later years.
The engine cowling needed beefing up in later years as well, most early models were retrofitted.
The 77 model year was a transition year, in 78 they went to push/pull controls, improved gear speeds, and few other changes.

[1980Mooney]

2 hours ago, ArtVandelay said:

Not entirely correct. The J also got an improved intake (and maybe exhaust?) that made the ram air extraneous and was removed in later years.
The engine cowling needed beefing up in later years as well, most early models were retrofitted.
The 77 model year was a transition year, in 78 they went to push/pull controls, improved gear speeds, and few other changes.

Yes but those were not speed mods.  The engine cowling would crack from vibration - I know it happened to me.  When you say "push pull controls" you mean the vernier control of mixture and RPM and push on throttle.

[Hank]

23 minutes ago, 1980Mooney said:

When you say "push pull controls" you mean the vernier control of mixture and RPM and push on throttle.

No, he means the J model changed in 1978 from having a big-plane throttle quadrant to having the three control cable knobs sticking straight out of the panel for operation using pull and push motions.

Vernier controls came later.

Other aerodynamic changes were made from F to J, not all disclosed by Mooney. Engine ducting is different, fresh air intakes moved from the cowl to the empennage, roof vent removed, etc., etc.

[PT20J]

7 hours ago, 1980Mooney said:

First you should fly a box and average the four GPS speeds.

Actually, that’s not accurate if there are winds. But there is a method that factors out the wind.

https://www.ntps.edu/information/downloads.html