M20J Missile Help

[zehutiman]

As a new owner of a 1980 M20J Missile with the IO550A engine, I can’t find any cruise performance information in the Supplement provided by Rocket.  Are there any Missile owners out there who might be willing to share their tables, or know where I can access them?  Obviously, they’d be nice to have and to assist with learning the best leaning procedures.  Much appreciated.

[Fly Boomer]

30 minutes ago, zehutiman said:

As a new owner of a 1980 M20J Missile with the IO550A engine, I can’t find any cruise performance information in the Supplement provided by Rocket.  Are there any Missile owners out there who might be willing to share their tables, or know where I can access them?  Obviously, they’d be nice to have and to assist with learning the best leaning procedures.  Much appreciated.

Not sure about the Missile, but the Rocket has a basic chart on the sun visor.

[1980Mooney]

6 hours ago, zehutiman said:

As a new owner of a 1980 M20J Missile with the IO550A engine, I can’t find any cruise performance information in the Supplement provided by Rocket.  Are there any Missile owners out there who might be willing to share their tables, or know where I can access them?  Obviously, they’d be nice to have and to assist with learning the best leaning procedures.  Much appreciated.

Rocket Engineering did not provide any cruise performance information.  I had my J modified by Rocket - I have everything that they provided back then, all paper work, - there are not any detailed tables. 

When you say "leaning procedures" - it is pretty simple.  If ROP - just bring one cylinder to peak and then richen however much you desire. 75 or 100 degrees.  Interestingly I find that the old analog cylinder head temperature gauge (which has to remain per the STC) is just as accurate as the digital engine monitor - and quicker.  For running LOP you need to ask others - I don't do it.

The Missile is tightly cowled and heat is an issue on warm days and during long idling holds for IFR release - you need to watch your temps during climb - stay rich.  You may have to level off to build speed in order to enhance cooling on some climbs.  The IO550A on the Missile has "Auto-Lean" so you always take off full rich regardless the density altitude.

Take off and climb are simple - full throttle, full rich until you level off at cruise altitude (Auto-Lean takes care of that).  If going any reasonable distance I really prefer to cruise at 9,000-12,000 ft.  I fly 2,400 rpm and wide open.  When I begin a long descent, I keep the engine manifold pressure "square" as altitude drops and engine manifold pressure begins to rise - I close the throttle to keep it at 24" hg. and richen it up a tad.  

If you are looking for tables which show all the combinations of RPM at various altitudes with speed, engine manifold pressure and fuel consumption the original M20R tables and charts are a pretty good resource.  The Ovation had the IO-550-G.  It produced 280 hp because it was limited to 2,500 rpm.  Your IO550A is rated 300 hp at 2,700 rpm.  

The Missile is a bit slower and the fuel burn is probably a bit higher than these numbers.  I know the other day with a light load a little warmer than Standard Day temp, 6,000 ft, 2,400 rpm, wide open, 75 degrees rich of peak I can average 180 kts. TAS.  I don't recall the fuel burn.  The charts below have 2 examples.  The second one shows 25 degress C, 3,200 lbs,, 6,000 ft, 2,400 rpm, 15.6 gph, 75% power (ROP Best Power), and 178 kts.  The first one shows 9 degrees C., no weight shown, 8,000 ft, 15.6 gph, 75% power (ROP Best Power)- if you go to the second chart that equates to 180 kts. 

One thing that makes it hard to compare to these charts is that the Missile has ram air.  If you have a good seal between the upper cowl and the filter then it adds about 1 inch hg pressure.

Edited January 15, 2023 by 1980Mooney

[carusoam]

There are more than a few Missile owners around here…

I always invite @Seth when Missile questions arise…

Searching for a Missile is how I found MooneySpace more than a decade ago…

IO550 Ops are pretty similar…. The M20R engine procedures are pretty helpful for comparison…

Rocket engineering wrote an STC for the 310hp IO550G used in the Ovation3, Standing O, and Screamin’ Eagle…. Really good information…

Like 1980’s chart above… the 310hp M20Rs use 2700max RPM….

Continental also wrote a nice handbook for the engine…

One thing to know… the Missile’s max FF seems to be lower than other IO550 installations… 25 vs. 30 and everything in between…. CHT control can be better with the higher FF… talk with your mechanic for details…

Leaning an IO550 is standard practice…

If your engine is fortunate… it can lean infinitely, until it gets quiet up front….  Altitude dependent, above 10k’ the engine can lean to 50°F LOP or more before getting quiet… down low, 100°F LOP is possible before things shut off…

Question for 1980… do you have a 25gph max FF…?  another MSer was struggling with CHT control and was challenged by this.  I think he stopped coming by before he found a solution…

PP thoughts only not a mechanic or cfi….

Best regards,

-a-

[zehutiman]

10 hours ago, 1980Mooney said:

Rocket Engineering did not provide any cruise performance information.  I had my J modified by Rocket - I have everything that they provided back then, all paper work, - there are not any detailed tables. 

Well, that’s a bit of a relief to know that I’m not missing them.  In the flights I’ve had so far, I’ve just been leaning to about 15.5 gph between 8000 and 10,000’, which is what the previous owner stated was his procedure — which looks to be a good ballpark target.  And, I’ll try your technique next.  Thanks for the charts.

[zehutiman]

8 hours ago, carusoam said:

Question for 1980… do you have a 25gph max FF…?  another MSer was struggling with CHT control and was challenged by this.  I think he stopped coming by before he found a solution…

I’ll have to look at that.

[1980Mooney]

8 hours ago, carusoam said:

Question for 1980… do you have a 25gph max FF…?  another MSer was struggling with CHT control and was challenged by this.  I think he stopped coming by before he found a solution…

 

27 minutes ago, zehutiman said:

I’ll have to look at that.

Yes - it is set up per the Continental book specs.  When you say "25 ghp max FF" you mean at sea level. The Auto-Lean then reduces mixture and fuel flow per the chart below.  Mine tracks within the ranges with one caveat - When at speed the ram air produces 1 inch hg denser air with is approximately equivalent to the pressure altitude produced by 1,000 ft.   So when wide open at 6,000 ft I am seeing the fuel flow and performance for 5,000 ft.  If I slow down at 6,000 ft and then open the engine wide open then I see the book fuel flows for 6,000 ft.

[KLRDMD]

14 hours ago, 1980Mooney said:

The IO550A on the Missile has "Auto-Lean" so you always take off full rich regardless the density altitude.

The Missile had auto lean when converted but not all Missiles have retained it. I looked at a Missile last year that did not have auto lean.

[KLRDMD]

14 hours ago, 1980Mooney said:

If ROP - just bring one cylinder to peak and then richen however much you desire. 75 or 100 degrees.  Interestingly I find that the old analog cylinder head temperature gauge (which has to remain per the STC) is just as accurate as the digital engine monitor - and quicker.  For running LOP you need to ask others - I don't do it. 

When I begin a long descent, I keep the engine manifold pressure "square" as altitude drops and engine manifold pressure begins to rise - I close the throttle to keep it at 24" hg. and richen it up a tad.  Your IO550A is rated 300 hp at 2,700 rpm.  

I know the other day with a light load a little warmer than Standard Day temp, 6,000 ft, 2,400 rpm, wide open, 75 degrees rich of peak I can average 180 kts. TAS.  I don't recall the fuel burn.

In my Bonanza I have a Continental IO550B that makes 300 HP at 2,700 RPM. That's not exactly the same as the IO550A in the Missile but overall I think the airplanes are similar enough to get an idea. I run LOP and generally cruise between 8-12k ft. Yes, I could/should tweak my settings per specific altitude but I just use fixed numbers. I cruise at full manifold pressure, whatever that gives me. For the prop I choose either 2,400 RPM if not in a hurry to get anywhere or 2,500 RPM if I want to get somewhere. For the mixture, 12.5 GPH if at 2,400 RPM and 13.0 GPH at 2,500 RPM. In cruise get 178 KTAS at 2,500 RPM, 13.0 GPH and 8,500 ft.

For descent I pull the manifold pressure to 20" and begin a 500-600 fpm descent without changing the mixture or prop. That puts me right at the top of the green arc of 160 KIAS or slightly into the yellow arc. With smooth air (rare in Arizona) I leave more manifold pressure in.

[1980Mooney]

3 hours ago, KLRDMD said:

The Missile had auto lean when converted but not all Missiles have retained it. I looked at a Missile last year that did not have auto lean.

"Auto Lean" is simply an altitude compensating fuel pump.  Sadly many mechanics didn't understand how to adjust it. - adjusted fuel flows too lean, potentially caused damage and in the end the owner had to foot the bill to replace a perfectly good fuel pump.  See article below from 1998.  In the hands of a competent mechanic it works great.  I suspect the Missile you looked at suffered at the hands of a confused mechanic sometime in its life.

 

[KLRDMD]

34 minutes ago, 1980Mooney said:

"Auto Lean" is simply an altitude compensating fuel pump.  Sadly many mechanics didn't understand how to adjust it. - adjusted fuel flows too lean, potentially caused damage and in the end the owner had to foot the bill to replace a perfectly good fuel pump.  See article below from 1998.  In the hands of a competent mechanic it works great.  I suspect the Missile you looked at suffered at the hands of a confused mechanic sometime in its life.

I believe I was told a regular fuel pump was installed at overhaul.

[Seth]

Sorry for being late to the party! 

Feel free to reach out to me as a PM. I now have a 4 blade prop on my Missile so my numbers may be different, and I'm happy to chat. 

Also, just make sure the auto leaning mixture is set properly. At my recent overhaul Continental did not have it set up correctly so it was running lean until we adjusted it. Very important to use fuel to keep the engine cool on take off and initial climb.

 

-Seth

[Pinecone]

I have always heard that a good target for fuel flow for take off and climb was 1 GPH per 10 HP.  So a 300 HP engine should be around 30 GPH.

My 220 HP engine is about 24 - 25 GPH at full throttle and full rich.

[rickseeman]

Maybe this will help

 

https://www.planesandboats.com/wp-content/uploads/2021/03/MooneyMissileConversion.pdf

 

[rickseeman]

1 hour ago, Pinecone said:

I have always heard that a good target for fuel flow for take off and climb was 1 GPH per 10 HP.  So a 200 HP engine should be around 30 GPH.

My 220 HP engine is about 24 - 25 GPH at full throttle and full rich.

I think N/A should be lower than that.

[Greg Ellis]

1 hour ago, Pinecone said:

I have always heard that a good target for fuel flow for take off and climb was 1 GPH per 10 HP.  So a 200 HP engine should be around 30 GPH.

 

Did you mean 20 GPH?

[Guest]

4 hours ago, Pinecone said:

I have always heard that a good target for fuel flow for take off and climb was 1 GPH per 10 HP.  So a 200 HP engine should be around 30 GPH.

My 220 HP engine is about 24 - 25 GPH at full throttle and full rich.

A quick rule of thumb, 9% of rated HP for a normally aspirated engine and 11-12% for a turbocharged engine.  Your first number would be 15%.

[Pinecone]

6 hours ago, Greg Ellis said:

Did you mean 20 GPH?

No, I meant a 300 HP engine.

[Pinecone]

3 hours ago, M20Doc said:

A quick rule of thumb, 9% of rated HP for a normally aspirated engine and 11-12% for a turbocharged engine.  Your first number would be 15%.

Typo, it was supposed to be 300 HP in the second.

25 GPH for a 220 HP engine is amazingly 11.4%.