M20F cruise performance & service ceiling

[Shadrach]

I have had my F to DAs in the 17,000 range. We were light (just over 2300lbs). It did way better than a normally aspirated, 200hp single has a right to.  I did not record the speed but recall that the lowest measured TAS was about 140kts.  Climb was reasonable up to about 15,000 (400ish FPM). We stopped for speed runs every 1000 feet on the way down and this made it clear that the airplane would be usable at higher altitudes when initiating climbs from cruise speed.  This flight was done for fun about a decade ago.  I don't like the nose hose (but could learn if I had a plane that warranted it) and have no use for flying that high where I am.  For NA ops I prefer 10,000 to 12,500 if winds are favorable.  Best combo of MPG and speed in that altitude range.

[Ventus4]

If it helps I do have a 1967  M20F practically with zero mods and I performed a series of tests at 2500ft, what I got was within 3% of POH on all the 6 different settings.

The Temperature was ISO standard and we were at MTOW and surprisingly the average  IAS on the four segments  was practically identical to the avi GPS

(max 1kt different) 

Only the Fuel was up respect to the POH (about 8-9% more) , we lean 100ROP.

In general now I feel better of the plane performances. 

Andrea

 

[Shadrach]

5 minutes ago, Ventus4 said:

If it helps I do have a 1967  M20F practically with zero mods and I performed a series of tests at 2500ft, what I got was within 3% of POH on all the 6 different settings.

The Temperature was ISO standard and we were at MTOW and surprisingly the average  IAS on the four segments  was practically identical to the avi GPS

(max 1kt different) 

Only the Fuel was up respect to the POH (about 8-9% more) , we lean 100ROP.

In general now I feel better of the plane performances. 

Andrea

 

I agree, our bird (67 Exec) is damn close to POH numbers in cruise and climb as long as you don't use POH technique.  The climb numbers given in the POH were achieved WOT, Ram air open and 2700rpm.  However, the POH recommends climbing at 26"X2600 as soon as the gear is retracted. This does little more than ensure book numbers will not be attained and that time to altitude will be increased.  It may make for higher CHTs as well...

[Ragsf15e]

On 1/20/2021 at 3:33 PM, Chris Briley said:

I purchased a 1970 M20F last year and have really enjoyed flying it.   I’m wondering if anyone has cruise performance for the mid teens?   In my POH, I have climb performance to 16,000  but the cruise performance figures only go to 12,500.

I’ve run into an issue with flight planning in foreflight as it maxes out the altitude to 12,500 based on the POH.    

My understanding is that the 20F has a service ceiling of 16,900, so not sure why the POH stops at 12,500.

Any info would be great.  

Thanks,
Chris

I fly an F in Washington state and down through Idaho, Nevada, Utah a lot.  It will get up to the mid teens but it’s not really happy up there if it’s warm and/or you’re loaded anywhere near gross.  Clearly you can get the airplane higher (see the post about going to FL220), but comfortable cruising ended for me through about 14,500 on a warm day (DA may have been much higher).  Your engine is getting pretty close to about 50% power... 100hp!   

As @TTaylorsaid, somewhere around 9gph and 140kts is all you’ll see up there.  Up that high, rich of peak and 2600+ rpm are your friends! Additionally, be careful around the mountains because your climb rate can easily be overcome by a good downdraft, rotor, or mountain wave (the sinking part obviously, the up part is awesome!).

Edited January 22, 2021 by Ragsf15e

[MikeOH]

18 hours ago, Niko182 said:

If the plane isnt stalling, doesnt that mean it can continue to climb?

True.

But, that does not prove the converse true. Just because the plane can't climb does NOT mean it's on the verge of stalling.

[Ragsf15e]

9 minutes ago, MikeOH said:

True.

But, that does not prove the converse true. Just because the plane can't climb does NOT mean it's on the verge of stalling.

We’re getting in the “power curve” here.  You can be “behind the power curve” and not stalled.  In that case it actually takes more power to go slower (think slow flight).  Theoretically, it will take less power to go faster but you have to get there first!  In slow flight you have extra power available and can accelerate.  At cruise you’re already at full.  Assuming you are already at full power, you will not accelerate, you will have to descend to accelerate and then possibly to climb higher.  I definitely wouldn’t think cruising less than Vy is gonna be very successful?

[MikeOH]

18 hours ago, carusoam said:

Essentially the air is so thin...

The AOA to sustain flight... is very high...

At the point you have reached the absolute ceiling you have run out of available AOA...

a simple bump in the air is capable of exceeding the critical AOA...

or trying to climb another foot... again you exceed the AOA limit...

or a small amount of bank... now you have an accelerated stall to avoid... 

Each foot you climb, the %bhp of the engine decreases... requiring the PIC to increase the AOA the slightest amount to hold altitude...

Lots of balance required at the edge... between decreasing HP, and increasing AOA....

Expect to get a feel for what Vy or Vz is while up there...  efficiency is going to be important...  remember you are really low on usable hp up that high...

PP thoughts for discussion only, not a CFI...

Best regards,

-a-

I maintain that at absolute ceiling you are NOT near the stalling angle of attack.  Here is a chart that shows the convergence of Vx and Vy at the absolute ceiling.  We are assuming level flight at 1g.  You can see that Vx is lower at sea level (about 92 kts IAS), but obviously above stall speed.  At the absolute ceiling Vx has risen to almost 100 kts.

Is your claim that stall speed rises from its sea level value to just under 100 kts IAS at the absolute ceiling?

 

[MikeOH]

Just now, Ragsf15e said:

We’re getting in the “power curve” here.  You can be “behind the power curve” and not stalled.  In that case it actually takes more power to go slower (think slow flight).  Theoretically, it will take less power to go faster but you have to get there first!  In slow flight you have extra power available and can accelerate.  At cruise you’re already at full.  Assuming you are already at full power, you will not accelerate, you will have to descend to accelerate and then possibly to climb higher.  I definitely wouldn’t think cruising less than Vy is gonna be very successful?

Agree: Vx = Vy at absolute ceiling.  You have to descend as you are well behind the power curve.

Just not on the verge of stalling.  That is pulling back WILL result in a descent, but not an immediate stall.  You are not at critical AOA.

[Ragsf15e]

10 minutes ago, MikeOH said:

Agree: Vx = Vy at absolute ceiling.  You have to descend as you are well behind the power curve.

Just not on the verge of stalling.  That is pulling back WILL result in a descent, but not an immediate stall.  You are not at critical AOA.

Yes I definitely agree.

[M20F]

I have on occasion taken The Executive to FL250 where I see TAS 160-170kts depending upon ISA.  As Jack Welch liked to say, not all executives are created equal. 

[kortopates]

3 hours ago, MikeOH said:

Agree: Vx = Vy at absolute ceiling.  You have to descend as you are well behind the power curve.

Just not on the verge of stalling.  That is pulling back WILL result in a descent, but not an immediate stall.  You are not at critical AOA.

Agreed and sorry to be gone for awhile. You said it right above earlier. I was referring to the more practical nature of what a pilot is likely to do that perhaps doesn't understand the principle you so well pointed out. I don't think ASEL pilots get much training on this like multi-engine pilots do or are expected too since we see a lot of fatalities among multi pilots. But more specifically, ME pilots are taught that above the absolute ceiling, Vyse (Vy single engine) becomes the minimum  rate of sink speed; slower or faster you'll come down faster. But all to often, the pilot pulls back increasing the AOA attempting to stop the sink, but the sink gets worse and either the multi- pilot falls belong Vmc resulting in a stall spin or the single engine pilot stalls - both trying to prevent further sink.  Much more dangerous for the Multi pilot since single engine absolute ceiling can be pretty low relative to terrain.  Of course all they had to do was lower nose, gain some speed below absolute altitude; assuming they do have terrain clearance. But it only takes just a bit of high level turbulence to take you from just below absolute ceiling to above it due to the loss of performance in turbulent air (loss of airspeed). 

I think it takes some real discipline and understanding of the how the plane will handle if one is going to try this. After all you'll still be in a climb just to maintain level flight, the temptation to just climb steeper must be very strong.   

Edited January 22, 2021 by kortopates

[carusoam]

Thank you gents!

My knowledge clearly needs some work prior to going that high...   

Is any of this related to the ‘coffin corner’?

Possibly described by U2 pilots or SR71 pilots...?

Best regards,

-a-

[FastTex]

Great info. No intention to hijack this thread but, to the "F" pilots in here, can you share what oxygen system do you use?

 

[Keith20EH]

Coffin corner is where Vne and Vs meet, on the graph it makes a “corner”. High altitude, older jet concerns, no worries for the Mooney..

[TTaylor]

8 hours ago, FastTex said:

Great info. No intention to hijack this thread but, to the "F" pilots in here, can you share what oxygen system do you use?

 

Mountain High O2D2 with a portable tank.  I have it in a carry bag so I can bring it when I think I will need it.  It only works for 2, but usually enough for most trips.  Rarely do I fly high enough to require O2 for everyone on board (+15,000).  With the D2 the pilot can stay on O2 and we have individual cannulas for each of us, so the others can take turns as needed if we stay above 10,000 for long periods. Using 02 cuts down on fatigue and headaches even if you are not above 12,500.  We have a large tank in the hangar so cost is minimal for the benefit.

[Ryan ORL]

11 hours ago, carusoam said:

Thank you gents!

My knowledge clearly needs some work prior to going that high...   

Is any of this related to the ‘coffin corner’?

Possibly described by U2 pilots or SR71 pilots...?

Best regards,

-a-

In general that has to do with the convergence of stall speed and the maximum mach number.  Not really the same as Vne because it's not an indicated airspeed, but same idea.

Would be nice if a Mooney was fast enough to have a maximum mach number  

[Hank]

34 minutes ago, Ryan ORL said:

Would be nice if a Mooney was fast enough to have a maximum mach number  

My personal peak is 0.28M, but I have a C model further slowed by a 3-blade prop . . . .

[Ragsf15e]

18 hours ago, M20F said:

I have on occasion taken The Executive to FL250 where I see TAS 160-170kts depending upon ISA.  As Jack Welch liked to say, not all executives are created equal. 

Showoff.  I bet she’s still making 65% power too!

[carusoam]

Quote of the day award...

Mis-quoting Jack Welch in the most creative Mooney Way!  

Way to go Mike!

I think Jack would agree...

Best regards,

-a-

[Shadrach]

I had to make a supply run to our local pilot shop (2W2) for oil and filters. Not the best day for short field work( 29017G25).  However, I thought recorded FA initial climb performance might be interesting to folks not familiar with the vintage 200hp (25°) birds. These are low altitude flights between 2500 and 3500 so no climb to cruise info but a good indication that book climb rates are not as “optimistic” as some would have you believe. I weighed a little over 2200 on the first flight and just shy of 2400 on the return. DA at departure was 0’ at my 701’ field and I assume pretty close to the same at 2W2 (791’). Performance likely would’ve been better had it not been so bumpy.

 

[carusoam]

Excess hp really shines!

Cold weather, and low DAs are really helpful.

Great data, Ross!

Best regards,

-a-