M20C to 18,000'

[Albatros]

Took our 1962 M20C 18,000' today. Took 45ish minutes to reach altitude. I was surprised it was still climbing steady at 18k. I was not cleared to Alpha by controler so have to stay below. Cool experience !

[MIm20c]

Not many C’s have ever been to 18k would be my guess. I’m curious if you have an engine monitor and what the cht’s were at the end of your climb when you took the picture?

[yvesg]

I wish to take mine up there too at some point. Got an oxygen tank of my own now so will try next long trip.

Yves

[Hank]

Took my C to 15,000 msl one August afternoon. Later calculated that DA there was 18,800! As you noted, climb wasn't good, but she was still going. Stopped at 15,000 so that Indy Center wouldn't have to pass us off to someone else just for me to head back down again. It was also great Emergency Descent practice, those steep spirals work very well!

[Hector]

Had mine to 16500 once and she was still climbing. Curious what MP were you able to develop at 18k


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[larryb]

I had my J up to fl 210 once. That was it. I had a clearance for fl 220 but could not get there. Had to negotiate with ATC to stay where I was, which was the wrong altitude for my direction of flight. This was an attempt to stay above some weather on a trip.

[mooneyspeed]

Were you going somewhere or just seeing if it would do it?


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[Albatros]

I was not going anywhere just decided to test Mooney ceiling. AD at MSL was 1200' and air temp 68. Naturally it was slowing down with altitude. Engine where good and steady climbing 300-500 rate. It was impossible to keep cylinders below 420 degrees at altitude no matter what I did with lean. Manifold Pressure was dropping steadily as climb continued. I think, on the end it was 12 in hg. RPM remain same (26). I did power descend to prevent rapid cooling. Over all it did great. I did not expected to go over 15-16k and was suprised to see it was still climbing all the way to 18. Than naturally I got Jax Center give me little warning to stay out of Alfa. I was expecting that anyways and was laughing when he told me. Never expected in M20C to be told to stay out of Alfa!

[gsxrpilot]

Get a turbo Mooney... and you'll never want to come back down. 

I still makes me smile when I hear "November 252 alpha delta climb maintain flight level ..."

But back to the thread... I had my C to 16,500 once to get over some weather. 

[ArtVandelay]

70 knots on climb, curious what your CHTs were?

[carusoam]

More proof that an M20C contains a lot of value!

Nice data collection, Albatross

Go Mooney!

Best regards,

-a-

[peevee]

2 hours ago, bluehighwayflyer said:

Well, his OEM CHT gauge is showing about 460 dF in the panel picture. 

Seems worth it. 

[cliffy]

Getting up high and staying up high are two different animals  in an NA airplane. 

Can you hold 16,500 or 17,000 (IFR) with any kind of down draft?

During the 9/11 shut down I got IFR to 15,000 in my D (due to MEAs out here in the west) and finally had to ask for a block (14k to 15K) because of down drafts exceeding my ability to climb to hold altitude.

DA was 17K+

[Albatros]

Theoretically, naturally aspirated engines do not perform good at these altitudes. Naturally, many factors/factors contribute to this. I just did test and do not plan to cruise here anyways. If Center alowed me I would continue to climb until I could not gain any more altitude. I believe I was close to that point, but who know ;). Always good to know limits of bird you are flying. 

[Jerry 5TJ]

34 minutes ago, Albatros said:

Theoretically, naturally aspirated engines do not perform good at these altitudes.....

Pedantic Quibble:

I was riding in back on a Southwest 737 at FL400 not long ago.  They have normally aspirated engines. 

My P46T climbs briskly until bumping into the RVSM “ceiling.”  It is normally aspirated.  

The M20C doesn’t climb well at 18,000 because it only has about 70 hp remaining up there, not because it’s normally aspirated.  

Congratulations on reaching that high in your C.  I never got mine above 14,000.  ATC was patient with me at that.  

If you file an IFR plan you can keep on going up. Pick a cold day with standing lenticular clouds and stay upwind of the cloud bases.....

 

[bonal]

4 hours ago, Jerry 5TJ said:

Pedantic Quibble:

I was riding in back on a Southwest 737 at FL400 not long ago.  They have normally aspirated engines. 

My P46T climbs briskly until bumping into the RVSM “ceiling.”  It is normally aspirated.  

The M20C doesn’t climb well at 18,000 because it only has about 70 hp remaining up there, not because it’s normally aspirated.  

Congratulations on reaching that high in your C.  I never got mine above 14,000.  ATC was patient with me at that.  

If you file an IFR plan you can keep on going up. Pick a cold day with standing lenticular clouds and stay upwind of the cloud bases.....

 

While I agree on your point that our engines can only make a low percentage of rated power up high because they are normally aspirated I disagree that a jet engine is also normally aspirated. They have compressor blades that pressurize the incoming air to a higher psi or am I wrong. Just like a mechanical blower or turbo charger does for piston engines just a different method of air compression.

[Raptor05121]

I think Jerry is about to dump some rocket science definition the rest of us won't understand

[Jerry 5TJ]

Well, I’m not a rocket scientist but thanks anyway. 

My lay reasoning:

Both NA piston engines and turbine engines have a fixed compression ratio (ignoring variable inlets and adjustable stator blades which small subsonic turbine engines rarely have)

Given fixed compression ratios the combustion chamber absolute pressure declines with altitude, right?   In the piston we reduce fuel by “leaning” to keep the Fuel to O2 ratio optimal.  The turbine engine’s fuel controller reduces fuel flow similarly.  Both types lose power along similar curves: at around 18,000 feet the air density is about half that of sea level, and engine power is similarly reduced.  

The turbocharged piston engine is the odd system:  It has a pre-compression system ahead of the fixed-ratio piston compression chambers.   Power remains constant up to the point where the pre-compression system runs out of range aka it reaches the critical altitude.  (Or until the engine components melt, pre-ignition starts or other expensive noises happen.)

The main reason the usual turboprop has better high altitude performance is it has more power in reserve to begin with.  The PT6A-35 maximum permissible shaft power at sea level is only a bit over 60% of the engine’s thermodynamic limit.   So it will provide that flat rating to around 15,000 feet (on a hypothetical standard day) Above that altitude power declines.

If you operated the O-360 in your C model the same way you’d push the throttle in to about 60% or 115 hp for takeoff at sea level.  You would keep adding throttle to maintain 115 hp as you climbed.  Around 10,000 you’re at WOT.   Above that altitude power declines.

You guys are now asking why, if I claim the two cases are so similar, does the piston reach WOT at 10,000 (60% power) while the turbo shaft engine made it to 15,000’ to reach its power limit?  

Well, I’m not sure, but I think it mainly has to do with temperature.  The O-360 runs at fixed rpm and at 60% is leaned to best power mixture producing a fixed temperature (EGT) regardless of altitude up to WOT point.   The PT6A runs at higher rpm and higher ITT as it climbs.  The piston engine efficiency is stable while the turbine engine efficiency rises with altitude.  That efficiency rise offsets the adiabatic power loss somewhat.  

The turbine engine reaches its maximum design temperature at some altitude and then it isn’t permitted to increase further, so power output drops as the climb continues.  

The ideal efficiency point in the turbine is at the altitude where ITT is at maximum and engine rpm is producing best efficiency, probably near 100%.   Without RVSM you generally can’t quite get high enough for the PT6A to peak its rpm. 

The piston can reach its peak combustion efficiency at any altitude, unlike the turbine.   

Classic topic drift.   I still feel 18,000’ in a C model is pretty remarkable.   

[carusoam]

1) the c is amazing...

2) the O360 can be fit with a compressor.  A turbo normalizer for the carb... There is at least one MSer that has one...

3) Compressing the engine's air inflow is what keeps some engines from being considered normally aspirated. Turbo charged, turbo normalized, and super charged are not Normally aspirated...

4) having a compressor disc at the front of the engine sort of disqualifies it from being NA. It compresses the air differently than a TC does, to produce a big % of power at altitudes where there is not a high % of air density available...

5) you can see from Fuel flow and power output that...  the jet is designed to run at one set of high altitudes.  It's efficiency is terrible down low...  not as versatile as a TC'd engine or as flexible(?)(Produces power even if the turbo fails) as a TN'd engine...

6) But, If it allows Jerry to fly a NA P46T... I won't tell anyone...

7) I can claim I didn't see a TC on that there Brand P plane... it must be NA...

8) gotta love the straight pipes, no mufflers...

9) Speaking of straight-er pipes... does powerflow make an exhaust for the M20C?

Best regards,

-a-

[Hank]

10 hours ago, carusoam said:

1) the c is amazing...

2) the O360 can be fit with a compressor.  A turbo normalizer for the carb... There is at least one MSer that has one...

3) Compressing the engine's air inflow is what keeps some engines from being considered normally aspirated. Turbo charged, turbo normalized, and super charged are not Normally aspirated...

4) having a compressor disc at the front of the engine sort of disqualifies it from being NA. It compresses the air differently than a TC does, to produce a big % of power at altitudes where there is not a high % of air density available...

...

9) Speaking of straight-er pipes... does powerflow make an exhaust for the M20C?

Best regards,

-a-

I agree with Points 1-4. Sorry, but jet aircraft are not NA. There's no way a piston engine, even TCed, can make the same compression rate that a turbojet does. Ram jets are NA, but no one flies behind them any more . . . Few ever did.

And for #9, yes, there is a Power Flow for the C. I chose not to put one on when replacing my muffler a couple of years ago (there was a fist-sized hole on the bottom . . .   ). 

Which just reinforces #1:  Cs are awesome, and incredibly versatile!