M20J 201 Model Speeds

[EricJ]

8 hours ago, ArtVandelay said:

I would assume the G5 can be recalibrated and adjusted, no?

Not airspeed.  There's a cal procedure for altitude, but not for airspeed.

[FlyingDude]

23 hours ago, KSMooniac said:

Current project is deleting the pop up roof scoop and forward COM antenna. I

How many knots are you hoping to gain from that?

[KSMooniac]

How many knots are you hoping to gain from that?

10 knots! I'll be happy with 3. Or just anything I can detect, actually. It's a labor of love... Lots of labor in a hot hangar! A sane owner would've just bought a newer Mooney.

The best part will be the better overhead vent solution that is very much needed.

Smooth belly is coming up next, but after OSH since the roof improvements are taking longer than hoped.

Sent from my LM-V405 using Tapatalk

[KSMooniac]

Forgetting Mike 201er?
163KTAS, 139KIAS, 161GS, 9000ft, 11C OAT, 21.9”MP, 2620RPM, 63%HP, 8.4GPH, 10LOP, 2150lbs GW

Sorry, Mike! I didn't forget... I never knew your J was that fast/efficient! I knew you did long flights and now that helps explain it. Did you do a lot of optimization, or just luck-of-the-draw end up with a fast one? (Perfectly straight and rigged from the factory)

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[201er]

7 hours ago, KSMooniac said:

 

 

Sorry, Mike! I didn't forget... I never knew your J was that fast/efficient! I knew you did long flights and now that helps explain it. Did you do a lot of optimization, or just luck-of-the-draw end up with a fast one? (Perfectly straight and rigged from the factory)

Sent from my LM-V405 using Tapatalk
 

 

It used to be a slow one. 140-148 cruise on 8-8.5gph. Now 150-160 cruise on same fuel. A lot of small mods over the years that didn’t seem to add up to anything but then when I got it repainted, jumped about 8 knots. But it wasn’t just paint. New windshield, windshield cap, body work, etc. It all came together since.

[ArtVandelay]

It used to be a slow one. 140-148 cruise on 8-8.5gph. Now 150-160 cruise on same fuel. A lot of small mods over the years that didn’t seem to add up to anything but then when I got it repainted, jumped about 8 knots. But it wasn’t just paint. New windshield, windshield cap, body work, etc. It all came together since.

I went through the same (our Js were probably built within a few weeks of each other), same results. I’m faster when up north in cooler/dryer air, slower in Florida. I remember seeing your plane on Fort Pierce ramp, a lot of paint chipping on the leading edges as I recall…crucial for low drag to keep the leading edges smooth for low drag.

[KSMooniac]

Maxwell told me long ago the best speed mod is cold, calm day!  He's correct. 

[jetdriven]

On 6/14/2022 at 1:46 AM, KSMooniac said:

10 knots! I'll be happy with 3. Or just anything I can detect, actually. It's a labor of love... Lots of labor in a hot hangar! A sane owner would've just bought a newer Mooney.

The best part will be the better overhead vent solution that is very much needed.

Smooth belly is coming up next, but after OSH since the roof improvements are taking longer than hoped.

Sent from my LM-V405 using Tapatalk
 

I see you did what I did. Beefed up the flange on the dorsal fin then countersunk it with flush rivets 

[graham28105]

I'm just gonna ask. Did the original poster retract the gear? It's a huge speed mod.

[jetdriven]

On 6/16/2022 at 7:48 AM, jetdriven said:

I see you did what I did. Beefed up the flange on the dorsal fin then countersunk it with flush rivets 

 

[Ragsf15e]

3 minutes ago, jetdriven said:

 

Yeah it’s fast, but you’re permanently NORDO and lost!  Where the heck did hide the comm and gps antennas?

[jetdriven]

7 hours ago, Ragsf15e said:

Yeah it’s fast, but you’re permanently NORDO and lost!  Where the heck did hide the comm and gps antennas?

The GPS antennas are here. The COM 1 is right before the dorsal fin. 

[Ragsf15e]

3 hours ago, jetdriven said:

The GPS antennas are here. The COM 1 is right before the dorsal fin. 

Very slick.  The airplane looks real good that way.

[jsm]

Surprising to me how much variability it seems in the speeds of "different" 201's.  My 77' 201 is stock except for the Firewall forward HP+ conversion (10:1 compression pistons).  Just returned from BWG at 9,000'. 22"/2350 rpm, operating 10-20 degrees LOP.  This equates to about 55-65% power.  Full fuel, two passengers, baggage, etc (120 lbs below Max Gross weight). TAS entire trip varied between 155-159 knots (averaged about 157 kts..  variable depending on up/down drafts).  peak EGT 1300; peak CHT 365; OAT 14C. Fuel flow in cruise at this power setting/altitude (per fuel flow meter) varied between 7.8-8.0 gph. These are routine numbers that I have achieved over many years of flying with this plane.  

Have never tried to duplicate the "201 advertised maximum speed" since I am reluctant to run it a full power/rich at low altitude to duplicate the book numbers, but I have little doubt that it would do so.  (also there is a MP limitation on the STC at low altitude.. .so full-throttle below 1800' is prohibited). On shorter trips at lower altitudes and higher power settings I have routinely seen cruise speeds of 165 kts (burning >10 gph)..  

I wonder if the variability in cited performance numbers reflects variations in airframe trim and drag + variations in engine tune/condition? 

Just my two cents!  

jon

 

[jetdriven]

5 hours ago, jsm said:

Surprising to me how much variability it seems in the speeds of "different" 201's.  My 77' 201 is stock except for the Firewall forward HP+ conversion (10:1 compression pistons).  Just returned from BWG at 9,000'. 22"/2350 rpm, operating 10-20 degrees LOP.  This equates to about 55-65% power.  Full fuel, two passengers, baggage, etc (120 lbs below Max Gross weight). TAS entire trip varied between 155-159 knots (averaged about 157 kts..  variable depending on up/down drafts).  peak EGT 1300; peak CHT 365; OAT 14C. Fuel flow in cruise at this power setting/altitude (per fuel flow meter) varied between 7.8-8.0 gph. These are routine numbers that I have achieved over many years of flying with this plane.  

Have never tried to duplicate the "201 advertised maximum speed" since I am reluctant to run it a full power/rich at low altitude to duplicate the book numbers, but I have little doubt that it would do so.  (also there is a MP limitation on the STC at low altitude.. .so full-throttle below 1800' is prohibited). On shorter trips at lower altitudes and higher power settings I have routinely seen cruise speeds of 165 kts (burning >10 gph)..  

I wonder if the variability in cited performance numbers reflects variations in airframe trim and drag + variations in engine tune/condition? 

Just my two cents!  

jon

 

how were you measuring TAS

[PT20J]

There are a lot of variables. Eliminating measurement error would be helpful when making comparisons.

tas_fnl3.pdf

[blaine beaven]

On 7/30/2024 at 3:53 PM, PT20J said:

There are a lot of variables. Eliminating measurement error would be helpful when making comparisons.

tas_fnl3.pdf 28.34 kB · 14 downloads

Do people actually use this method with a spreadsheet? Another option I’ve heard is to fly 4 cardinal GPS headings, record GS, and divide by 4 to get TAS. It seems like less math, but is it not as accurate? 

[PT20J]

1 hour ago, blaine beaven said:

Do people actually use this method with a spreadsheet? Another option I’ve heard is to fly 4 cardinal GPS headings, record GS, and divide by 4 to get TAS. It seems like less math, but is it not as accurate? 

The national test pilot school adopted this method and I believe that it is considered the gold standard. NTPS created a spreadsheet to automate the calculations.

gps-pec-method.pdf

GPS_PEC.xlsx

 

[MikeOH]

@PT20J

This looks to be, fundamentally, the same as Prof. Rogers "Horseshoe Heading" technique:

 

horseshoehead_screen.pdf

[PT20J]

1 hour ago, MikeOH said:

@PT20J

This looks to be, fundamentally, the same as Prof. Rogers "Horseshoe Heading" technique:

 

horseshoehead_screen.pdf 57.89 kB · 3 downloads

It's similar, but more general because it does not require flying a specific headings which may introduce compass errors into the calculation and errors if the headings are not held exactly.

[Fly Boomer]

4 hours ago, blaine beaven said:

but is it not as accurate

Close, but not quite.  If you prefer to avoid doing the math (and avoid running the spreadsheets), you can use a version that runs in your browser (Javascript):

https://www.eaa62.org/technotes/speed.htm

 

[MikeOH]

3 hours ago, PT20J said:

It's similar, but more general because it does not require flying a specific headings which may introduce compass errors into the calculation and errors if the headings are not held exactly.

While I’d agree it is more general in the sense you don’t have to fly headings 90degrees apart, I don’t see how it eliminates either compass errors or reduces the accuracy to which headings need to be held. After all, if the headings didn’t matter what would be the point!

[PT20J]

5 minutes ago, MikeOH said:

While I’d agree it is more general in the sense you don’t have to fly headings 90degrees apart, I don’t see how it eliminates either compass errors or reduces the accuracy to which headings need to be held. After all, if the headings didn’t matter what would be the point!

The horseshoe heading technique requires flying three headings exactly 90 degrees apart, so if your compass is off a few degrees on some headings then errors will be introduced. The NTPS technique only requires flying three legs at different headings and the exact headings don't matter. The only requirement is to hold the heading long enough for GS and TRK to stabilize. The NTPS spreadsheet allows entering four legs so that the solution is overdetermined leading to increased accuracy.

[Thedude]

On 6/14/2022 at 6:53 AM, 201er said:

It used to be a slow one. 140-148 cruise on 8-8.5gph. Now 150-160 cruise on same fuel. A lot of small mods over the years that didn’t seem to add up to anything but then when I got it repainted, jumped about 8 knots. But it wasn’t just paint. New windshield, windshield cap, body work, etc. It all came together since.

You don't happen to have a full list of mods do you?... How did a new windshield help?

[MikeOH]

1 hour ago, PT20J said:

The horseshoe heading technique requires flying three headings exactly 90 degrees apart, so if your compass is off a few degrees on some headings then errors will be introduced. The NTPS technique only requires flying three legs at different headings and the exact headings don't matter. The only requirement is to hold the heading long enough for GS and TRK to stabilize. The NTPS spreadsheet allows entering four legs so that the solution is overdetermined leading to increased accuracy.

I suspect we are in violent agreement here, but I still fail to see why compass errors would not affect the NTPS technique, as well; you have to input the headings flown, so a compass error would still affect the calculation.  Frankly, there is no need to use the compass with either technique. I've just picked a heading, say north, held the heading on my HI until GS is stable (no need to worry about track), turned 90 degrees using HI, stable GS, turned another 90, stable GS. DONE.

Seems the NTPS technique just allows you to pick arbitrary headings, and add an extra leg to improve accuracy, as you mentioned.