What is your sweet spot altitude (for best TAS)

[Pinecone]

11 hours ago, cliffy said:

Did 5.3 hr  east bound ONCE but never again. Had 1+15 left in gas. Way too long to sit.

 

Such a short flight.

I have done 3 flights in the range of 7 to 7.5 hours.  Not as bad as I expected.

[cliffy]

13 hours ago, cliffy said:

Just for fun 2 years ago I did Tampa (Sun n Fun) to Santa Fe NM at 1500 AGL  all the way

and didn't talk to a sole unless I landed at a towered airport. 

Did 5.3 hr  east bound ONCE but never again. Had 1+15 left in gas. Way too long to sit.

 

How about a spelling change (thanks autocorrect)  SOLE  to SOUL

I wasn't talking to the fishes  :-)

[M20F]

3 hours ago, Pinecone said:

Such a short flight.

I have done 3 flights in the range of 7 to 7.5 hours.  Not as bad as I expected.

Jose and his piss tube will always win. 

[EricJ]

3 hours ago, M20F said:

Jose and his piss tube will always win. 

Less paint staining than G100UL! 

[BloodRedSkies]

E model w/McCauley 3 blade, Power Flow, 201 windshield, Cowl closure mod, One piece belly, Flap and Aileron seals, Oil cooler relocation. 

23.5-24" 2400rpm was light 2300lbs. 

Book says ~175mph(152kts) TAS, I see 158-163 KTS as my G5s are in KTS. 

Edited April 23 by BloodRedSkies

[DC_Brasil]

1990 M20J 

Standard Lycoming IO-360-A3B6D 

I usually like to fly as close to 10K as possible depending on winds, operating LOP and WOT.

At 2200 RPM, I usually get around 140 Kts and between 7.7 and 8.3 Gal/h depending on weight and temperature. 

[jetdriven]

Your plane would be not just faster but also more efficient at 2500 or even 2600 RPM.

[jetdriven]

2 minutes ago, jetdriven said:

Your plane would be not just faster but also more efficient at 2500 or even 2600 RPM.

Here’s 2650 rpm and 160 ktas at 2650 rpm. 10GPH that’s just rich of peak. 

[cliffy]

I read somewhere long ago that the intake was optimized for 2500 RPM

[TangoTango]

I also find that 2500 rpm just feels right. Above about 2600 it gets vibey and noisy, lower than 2500 it gets a lower kind of vibration, almost like it's lugging. I'm sure it's fine, but it doesn't feel smooth like 2500 rpm does. 

I'm not usually fuel limited (and at 2500 I can always run as far LOP as I care to), but if one were trying to stretch the range wouldn't lower rpm allow you to run further LOP? Something about giving a slower leaner flame front adequate time to expand at a slower piston speed?

[cliffy]

2400  16.5 inches and just rich of leak EGT (25 deg)  seems to be the longest endurance in the 

J manual up around 8000 to 10000 ft   A little over 7 hrs 

[varlajo]

Squarely in the 7500-9500 ft camp, WOT, 2450 rpm, 50 LOP. 

[R Van Dyck]

Good Evening my Fellow Birdmen, I built an excel spread sheet with associated graphing. I am running an standard 75 C Model with the O-360. I commute from Southern Oregon to Los Angeles for work. I have only flown 3000' PA and above so the lower chart data is not correct it is out of the POH. I do as most of you NA fellas, I Run WOT -MP wiggle with about 1" of Carb Heat on. I have an engine analyzer to help with the data. Please feel free to plagiarize and modify to your needs.

Fly Smart,

Ryan

Mooney Economy.xls

[cliffy]

3 hours ago, R Van Dyck said:

Good Evening my Fellow Birdmen, I built an excel spread sheet with associated graphing. I am running an standard 75 C Model with the O-360. I commute from Southern Oregon to Los Angeles for work. I have only flown 3000' PA and above so the lower chart data is not correct it is out of the POH. I do as most of you NA fellas, I Run WOT -MP wiggle with about 1" of Carb Heat on. I have an engine analyzer to help with the data. Please feel free to plagiarize and modify to your needs.

Fly Smart,

Ryan

Mooney Economy.xls 64 kB · 5 downloads

Some of us can't open it

[Hank]

15 hours ago, cliffy said:

Some of us can't open it

It's an Excel spreadsheet. Just download Excel. I have it on my laptop, tablet and phone; then again, I'm an engineer and give by Excel!

[jetdriven]

General the Mooney airplane is slower the higher you go. It seems to not matter much between 3000 and 7000 feet but it’s definitely slower above that. Here’s a real 203 miles an hour true (176kt) in a J model but look at the altitude.

 

[cliffy]

49 minutes ago, jetdriven said:

General the Mooney airplane is slower the higher you go. It seems to not matter much between 3000 and 7000 feet but it’s definitely slower above that. Here’s a real 203 miles an hour true (176kt) in a J model but look at the altitude.

 

Braggart!   :-)

[cliffy]

I think (IMSMC) that the original 201 mph was supposed to be at

sea level.

I could be wrong but that's what I remember. 

[A64Pilot]

On 4/27/2025 at 8:10 PM, cliffy said:

Braggart!   :-)

From memory when I bought mine I went out and did a three way speed run and got 167 kts at 1000 MSL. WOT and 2600 RPM

I was also burning right at 20 GPH though. 8.35 MPG and I’m certain not real good for engine longevity

Back down to 23 squared and pretty deep LOP gives me 16.88 MPG at 135 kts at 1000 MSL

I can further reduce to 22 squared, 6 GPH at 20 MPG, but can’t stand that and it’s tough to keep cyl head temp in the green

Legend Cub as a comparison cruises 80 kts and 6 GPH for 13.3 MPG. Amazes me that we burn far less fuel than a Cub MPG wise.

[A64Pilot]

On 4/23/2025 at 7:53 PM, jetdriven said:

Your plane would be not just faster but also more efficient at 2500 or even 2600 RPM.

Define efficient.

Your MPG will go down but your speed will increase if the only variable is RPM.

[A64Pilot]

14 hours ago, cliffy said:

I think (IMSMC) that the original 201 mph was supposed to be at

sea level.

I could be wrong but that's what I remember. 

I’m sure it was sea level or lower, maybe a polished airframe, bare bones equipment, 5 gls of fuel on board and a 90 lb girl flying. Ailerons may have been reflexed a little, And maybe just a little wind behind it  

[jetdriven]

12 minutes ago, A64Pilot said:

Define efficient.

Your MPG will go down but your speed will increase if the only variable is RPM.

Actually, the miles per gallon goes up, the total trip burn goes down, and the trip time goes down as well. 

[cliffy]

I can rely on 16 MPG 155 statute at 9.6 GPH

Been doing that for years   WOT 2500 RPM  @9,000 ft

[A64Pilot]

1 hour ago, jetdriven said:

Actually, the miles per gallon goes up, the total trip burn goes down, and the trip time goes down as well. 

Your one of those guys that thinks their car gets better milage at 80 mph than 55 aren’t you? I’m just teasing but I’ve run into many that believe that.

I wish you were correct, but your not, unless your so slow your in the region of reversed command any additional speed of course requires more power which requires more fuel and the fuel required exceeds the speed increase percent wise, so the MPG goes down. Unfortunately you can’t increase fuel flow by say 20% and go more than 20% faster, I just pulled 20 out of the air, use any number.

I know what your thinking, that there is an efficiency point where the the fuel required to make horsepower has a peak, that is a point that the engine is operating at its greatest BSFC and your correct, there is, but unfortunately that small increase in efficiency is more than wiped out by the larger increase in drag from going faster. I have no idea at what RPM our motors peak at BSFC wise but suspect due to frictional losses it’s lower than 2500, add in of course prop efficiency and it’s peak is definitely lower than 2500. I don’t have an RPM number but suspect it may be the bottom of the green.

Turbines are often different, they are so inefficient at partial power that sometimes going faster will increase range because they are so much more efficient at higher power, but piston engines aren’t that way.

[jetdriven]

I think it's more of the efficiency of the prop, but when the plane slows down 6 kn between 2500 and 2700 RPM, and the fuel flow only goes down .3, you can see it. And at 14,000 feet, the airplane slows down 10 kn in turbulence, and the speed at 2400 RPM takes two minutes to recover whereas at 2700 RPM takes 30 seconds. So your average ground speed is just higher. And really you don't have enough horsepower above 10,000 feet anyway, 2700 just gives you more of the 100 HP available.  We've done it several times actually..... if you get up to 10,000 feet, and then set it up however you like at 2400 RPM, and look at your JPI fuel and time to destination, and then bring it up to 2700, and then re-lean for best power or slightly lean of that, the fuel at destination often is the same and sometimes less, but the time is always less.