M20J glide ratio

[Sportster64]

I’ve looked at a couple of the online POH for the m20j models, it appears the best glide ratio is different depending what manual you look at, or possibly it may be calculated differently based on gross weight vs 2300 lbs?

I’ve seen 12:1 also 10:1 in the Poh I’ve looked at.

I was wondering what people are actually seeing for glide ratio in the m20J. No mods

 

[WaynePierce]

Not to help you at all, just add more confusion... ForeFlight lists it at 11:1 :-)

[Skyland]

As discussed here in a recent thread, be sure to pull the prop all the way back to extent the glide.  A windmilling engine has enough oil pressure to feather the prop as much as possible.  A dead stick prop apparently results in an even better glide ratio.

[alextstone]

It's 11.46:1

[carusoam]

For an interesting answer to your specific question….

Find Chuck @cnoe….

He ran a bunch of real life numbers for his M20J…

A nice way to find the answer for your specific plane…

Then get the glide rings on your iPad…   
 

Of course… WnB are really important, as is procedure, and knowing your Best glide speed at the time….

The Mooneys aren’t as good as gliders, but, there isn’t a better GA plane to compare to….

Better to find a good place to land, then glide to a better place and goof up the procedure… 

PP thoughts only, not a CFI…

Go Mooney!

Best regards,

-a-

[Hank]

The Owners Manual for my C gives two Best Glide speeds:  prop windmills gear and prop stopped (10.3:1 and 12.7:1). Your J should do better.

[PT20J]

My 1997 M20J POH shows a glide range of 16 sm from 7300' which works out to a glide ratio of 11.57

My 1994 M20J POH shows a glide range of 16 nm from 8500' which works out to a glide ratio of 11.44.

Note that the older manual lists range in statute miles and the later manual uses nautical miles.

Both are listed for propeller windmilling.

Best glide occurs at L/Dmax angle of attack. So the glide speed (and corresponding sink rate) will vary with weight, but the glide ratio (which is numerically equal to L/D) does not.

Skip

[A64Pilot]

Mooney glide, about 11 to 1

C-172 about 9 to 1

Maule about 8 to 1, Maule on floats, coke machine

So, what’s the glide ratio of an MD-80? I’d tell you but you wouldn’t believe me.

[Skates97]

8 minutes ago, A64Pilot said:

Mooney glide, about 11 to 1

C-172 about 9 to 1

Maule about 8 to 1, Maule on floats, coke machine

So, what’s the glide ratio of an MD-80? I’d tell you but you wouldn’t believe me.

That reminds me of an aerobatics guy talking about the glide ratio of a Pitts, he said drop a brick and follow it down. 

[Jerry 5TJ]

9 hours ago, Skates97 said:

That reminds me of an aerobatics guy talking about the glide ratio of a Pitts, he said drop a brick and follow it down. 

Yeah, that’s one idea, but it leaves you looking up at the brick. 

[N201MKTurbo]

9 hours ago, A64Pilot said:

So, what’s the glide ratio of an MD-80? I’d tell you but you wouldn’t believe me.

I used to have access to a 737 sim. I flew it a lot. I did some power off glides with it, I was surprised how good it glided, so I assume the MD-80 is pretty good too.

[N201MKTurbo]

I just looked up the MD-80, they say 28-1.

[N201MKTurbo]

On my flight review last week, my instructor just says out of the blue “your engine just quit, what are you going to do” I pulled the power back to about 14” (don’t want to kill the poor engine) and choose a landing site a few miles away. She says “don’t you want to slow to best glide speed?” I asked “why, it will take us all day to get down there as it is” to which she said, your engine just caught fire! So I put the wheels and flaps down and cranked it into a 60 degree turn. We got down pretty fast. When I was on base to my spot she said “that’s good enough” And I said let’s take it all the way. I went down to the flare and then went around. It was a nice dirt clearing in the desertI could have easily landed without incident. The funny thing is when she filled out my logbook, she listed it as a touch and go.

[A64Pilot]

49 minutes ago, N201MKTurbo said:

I just looked up the MD-80, they say 28-1.

That’s a number I can’t get my head wrapped around, it’s very close I believe to an average run of the mill glider, not the high buck professional machines, but ones you’ll find in an average glider club say.

‘Without giving it any real thought I assumed Commercial aircraft wouldn’t glide very well, but I was very wrong.

‘But just as surprising was the fact the Mooney doesn’t really do all that much better than the run of the mill average GA airplane, I had assumed there would be a much bigger difference

[RobertGary1]

In the robbinsons it’s 4:1. Our training gliders are 32:1. Mid range gliders are 50:1 but there are some 70:1. 

[A64Pilot]

I don’t know about the ratio, but just as the point of intended landing disappeared under the nose of an AH-64, collective full down and you would make it.

Pretty sure well less than 4 to 1

[Jerry 5TJ]

The Piper P46T does about 23:1 glide up high and 15:1 near sea level, but only with the prop feathered.  
With the prop flat it will glide about like a Robinson.

[DCarlton]

15 hours ago, PT20J said:

My 1997 M20J POH shows a glide range of 16 sm from 7300' which works out to a glide ratio of 11.57

My 1994 M20J POH shows a glide range of 16 nm from 8500' which works out to a glide ratio of 11.44.

Note that the older manual lists range in statute miles and the later manual uses nautical miles.

Both are listed for propeller windmilling.

Best glide occurs at L/Dmax angle of attack. So the glide speed (and corresponding sink rate) will vary with weight, but the glide ratio (which is numerically equal to L/D) does not.

Skip

Does your POH recommend prop position to achieve that glide?  

[Sportster64]

So, it seems the general numbers are roughly 11:1.

given that number a quick number to keep in the back of my head would say for every 11000 ft of lateral movement, you would loose 1000 ft vertically. So that translates with a little safety margin added  to about 2 statute miles laterally for every 1000ft AGL loss.

yes, all the tables state with a windmilling prop. So I guess they assume you will not have any oil pressure to feather the prop ? Or is it more efficient with it windmilling?

 

 

 

[PT20J]

24 minutes ago, DCarlton said:

Does your POH recommend prop position to achieve that glide?  

No, it just says prop windmilling.

[Sportster64]

Where I wanted to go with this, I know ForeFlight will give glide to land rings while in flight. But I don’t know of any flight planning tools that will plan a route close to airports based on a glide ratio ?

in other words, if the flight planning software knows glide ratio, and bases it on current winds aloft , which of course will naturally introduce potential error, it could automatically plan the flight path to have an airport close enough.

if you use my example of 2 miles for every 1000 ft, say you plan 10,500, that would give a path of about 20 miles from airports. Figuring terrain near sea level, which would also add complexity.

possible in some areas, probably not realistic in remote areas. Also probably not possible for IFR flight planning.

 

 

Edited November 22, 2022 by Sportster64

[Hank]

32 minutes ago, Sportster64 said:

So, it seems the general numbers are roughly 11:1.

given that number a quick number to keep in the back of my head would say for every 11000 ft of lateral movement, you would loose 1000 ft vertically. So that translates with a little safety margin added  to about 2 statute miles laterally for every 1000ft AGL loss.

yes, all the tables state with a windmilling prop. So I guess they assume you will not have any oil pressure to feather the prop ? Or is it more efficient with it windmilling?

2 miles per 1000' is a good general number for your Mooney.

Just be aware that your prop does NOT feather! But moving the prop control to Full Coarse is required to reach this glide number.

[WAFI]

Just now, Hank said:

2 miles per 1000' is a good general number for your Mooney.

Just be aware that your prop does NOT feather! But moving the prop control to Full Coarse is required to reach this glide number.

When you say "Full Coarse" do you mean high rpm or low rpm?

[Ibra]

2 hours ago, Jerry 5TJ said:

The Piper P46T does about 23:1 glide up high and 15:1 near sea level, but only with the prop feathered.  

Why 15 vs 23? is that KTAS vs KIAS conversion? or something specific to PA46? 

I don't recall best L-to-D ratio (or VSI to ASI ratio) does change a lot with altitudes? the air density rho will disappear from the ratio and it's pure alpha angle of attack and wing geometry...also, in gliders best ratio of VSI to ASI stay about the same all the way to 20kft, I have not flown higher than that but I don't think it will move a lot?

Edited November 22, 2022 by Ibra

[Ibra]

Should one bother with the propeller in the case of serious catastrophic engine failures? 90% of chances it's gone, or does not feather, or does not turn, or go to fine pitch by itself...

I may feather it in glide (and go fine pitch for the flare) if it's something to do with air, fuel or mags though 

Edited November 22, 2022 by Ibra