Soaring in the Mooney M20

[Kevin Harberg]

Just curious to see if anyone has tried this. I had logged about 400 hours in my father's 1966 M20C (same as shown, even same colour), but never attempted to stop the prop inflight.

[jaylw314]

I recall reading somewhere here some MS'ers trying to get the prop to stop, and without any modification, they had problems keeping it stopped above stalling speeds, so it seems unlikely you could keep it stopped for long at best glide speed.

That being said, the windmilling glide ratio in my POH is 12:1, which is not much worse, and you'd probably gain a bit if you pulled the prop all the way back.

FWIW, it doesn't look like the prop is stopped in that photo, I think they're just claiming that glide ratio with stopped prop in test flights.

Edited December 30, 2020 by jaylw314

[PT20J]

We discussed this in another thread and IIRC, the result was that the drag of a stopped prop is slightly higher than a windmilling prop set to high pitch. I believe there are some youtube videos about. There's actually quite a bit of blade area to create drag when the prop is stopped but not feathered, and a non-feathering prop will go to flat pitch when stopped. 

Of course feathered is best. I recall reading somewhere that to get measurements to confirm the B-17 drag polar, Boeing flew one up to 20,000 feet or so and shut down all four engines and feathered all four props and did glide tests. I guess they got them started again  Test pilots have all the fun.

Skip,

[kortopates]

I recall reading somewhere here some MS'ers trying to get the prop to stop, and without any modification, they had problems keeping it stopped above stalling speeds, so it seems unlikely you could keep it stopped for long at best glide speed.
That being said, the windmilling glide ratio in my POH is 12:1, which is not much worse, and you'd probably gain a bit if you pulled the prop all the way back.
FWIW, it doesn't look like the prop is stopped in that photo, I think they're just claiming that glide ratio with stopped prop in test flights.

Your referring to Chuck, think his last name was Noe or perhaps close. He created spreadsheet with different conditions including the prop stopped. I don't recall if he got 13:1 but the spreadsheet is here on Mooneyspace.

What I derived for the J is 11.5:1 windmilling with prop pulled all the way back from the POH. The difference is dramatic compared to prop forward.
Still can't imagine seeing a Mooney ride a thermal like a glider for any length of time - but now is the season to try on the Eastern slopes of the Sierra's!


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[Comet]

Given 100 MIAS best glide speed, I figure you’d need a 7-8 kt thermal to maintain altitude.

might be fun to get into a good mountain wave...

[markgrue]

Years ago I was flying over Minden NV and caught a good mountain wave.  I had a picture of the prop stopped and the rate of climb at 2000 fpm.  We started at about 10K and finally decided to come back down when we reached 14.5K  If I recall it took an airspeed of over 120 to get the engine turning again.  Of course that is prime glider country so the waves and thermals were very common.

 

Mark

[201er]

4 hours ago, Comet said:

Given 100 MIAS best glide speed, I figure you’d need a 7-8 kt thermal to maintain altitude.

might be fun to get into a good mountain wave...

Wouldn’t be at best glide, but at minimum sink which is closer to Vx. Not that it makes much a difference but just saying.

[Comet]

I was assuming best glide listed in my POH, not a rigorous L/D max vs. minimum sink airspeed.

I’d love to see a polar for a Mooney (lots of armchair flying could be had).

 My G-CFI always mentioned the similarity of the laminar flow wing of a Mooney compared to a glider....still, 30:1 ratio is much different than 12:1!

[PT20J]

 

1 hour ago, Comet said:

I’d love to see a polar for a Mooney (lots of armchair flying could be had).

There’s some info in this thread that may be of interest:

 

[65eTurbo]

I did my PPL and IFR at Frasca Field.  Rudy Frasca had a short bodied Mooney (and a Spitfire, and a....).  Anyway, one day he mentioned in passing that he used to take it up high and kill the engine and soar with it.

[RobertGary1]

When I had the Aeronca several friends who stop the prop and do spot landing contests with  it stopped. They claimed the glide was much better stopped than windmilling. You did have to get to stall speed to get it to stop.

-Robert

[Joe Zuffoletto]

I didn't stop the prop, but I did go soaring in my Encore back in 2004 when the alternator shook loose and all the oil went overboard.  

Edited January 6, 2021 by Joe Zuffoletto

[Kevin Harberg]

21 minutes ago, RobertGary1 said:

When I had the Aeronca several friends who stop the prop and do spot landing contests with  it stopped. They claimed the glide was much better stopped than windmilling. You did have to get to stall speed to get it to stop.

-Robert

 

[Kevin Harberg]

In any videos I have seen, it appears as though you are correct in the low airspeed (just above stall) required to stop the prop. I will on occasion (at cruise speed) try and run a tank dry, and by watching my fuel pressure gauge I can sometimes catch the drop and switch tanks in time to keep the power on. Occasionally, the plane goes quiet for a second before the windmilling prop restarts the engine after restoring fuel supply. Without a starter, I am concerned the sleek Mooney may have to exceed VNE (143mph IAS in the M18) before the prop starts spinning again. I suppose the pitch of my fixed prop and engine condition (compression) may determine IAS required. The deadstick airport landings should not be too difficult, as I routinely chop power late on downwind and seldom require additional power to reach desired touchdown point, however, I am just a little uncomfortable determining the effects of wind direction and speed. I am aware that a person should pick a flare point further down the runway when landing deadstick to avoid an off strip landing short of the threshold, but still the idea of attempting this is unsettling. Your friends are obviously better prepared (or less frightened) than I practicing their deadstick landings. The Mooney seems to be a greater challenge due to its flatter approach profile.

[EricJ]

4 hours ago, RobertGary1 said:

When I had the Aeronca several friends who stop the prop and do spot landing contests with  it stopped. They claimed the glide was much better stopped than windmilling. You did have to get to stall speed to get it to stop.

-Robert

We used to do this in C150s and it was the same;  you have to get it pretty slow to stop the prop, and it'll stay stopped until you get a lot of airspeed back.   We did it for the same reason, the glide is quite a bit further with it stopped than windmilling.

Like this in a Taylorcraft (one reason he has to keep tapping the altimeter is because the engine isn't running to provide the vibration to break the stiction):
 

 

[carusoam]

One day...

I took the M20C out flying without a lot of fuel money available...

Being familiar with the glider ad, and some detail about ridge soaring...

Interesting to see how much time you can get flying with the engine running at idle...

The only challenge I noticed... without a decent engine monitor... the engine is running in a pretty cold state...

NJ has a few ridges that aren’t very tall, but produce some easy waves to fly on...

Logic prevailed...  and I flew home...

Seeing if @cnoe is around... 

Best regards,

-a-

[Ibra]

23 minutes ago, EricJ said:

We used to do this in C150s and it was the same;  you have to get it pretty slow to stop the prop, and it'll stay stopped until you get a lot of airspeed back.   We did it for the same reason, the glide is quite a bit further with it stopped than windmilling.

Same in SF25C motor-glider stall speed was about 50kts, prop stops about 55kts and start rotating slowly at 75kts (slightly above in +85kts you can air-restart with no battery but the bang on the exhausts is not healthy compared to restart at 60kts), don't recall the exact POH best glide speed but I always made sure it's done with horizontal propeller...

I doubt one could thermal in M20J, except in Namibia or Nevada, but it's ideal for cruise while wave flying and cloud street just less seat in the pants feedback but one can geuess it with AP on atitude hold 

Edited January 6, 2021 by Ibra