The Piper Cherokee 180D I am flying doesn’t have a published Vg in the POH.

Princesspilot206

Princesspilot206

Pre-takeoff checklist
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Princesspilot
How would I find it? The checklist says 85mph, but I don’t see anything about that in the POH. I see online there are various Vg speeds talked about for this make and model.
 
Many older planes to not have a best glide speed published. 85 mph sounds about right for a Cherokee.
 
The early Pipers (I've got a 180D also) did not have a POH, but a crappy AFH. So I bought the generic 180E "Owners Handbook" from Piper. Here are the specs. As a rule, a cherokee is a brick when it comes to glide. You'll notice there's no best glide:

Take-off Run (maximum effort, 25° flap) (ft) 720
Take-off over 50-ft barrier (maximum effort, 25° flap) (ft) 1625
Best Rate of Climb Speed (mph) 85
Rate of Climb (ft per min) 725
Service Ceiling (ft) 13,000
Absolute Ceiling (ft) 15,000
Top Speed (mph) 152
Optimum Cruising Speed (75% power, optimum altitude) (mph) 143
Cruising Range (75% power, optimum altitude) (mi) 725
Optimum Cruising Range (55% power, optimum altitude) (mi) 845
Stalling Speed (flaps down) (mph) 57
Stalling Speed (flaps up) (mph) 67
Landing Roll (flaps down) (ft) 600
Landing Roll over 50-ft barrier (ft) 1150

To make matters even more interesting, the Archer II POH has a Glide Range chart, assuming Power off, flaps up, 76 kts, and max 2550# (which is more than the 180D 2400# max). 76 KTS is 87 mph, by the way, so the 85 mph glide is about right. But remember glide is affected by weight, and the archer is heavier than the cherokee.


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If it's not in the POH you can't be tested on it.

Also absent will be any performance numbers for grass ops. My examiner made that a teachable moment and even said piper still doesn't have anything for grass in the POH.
 
Thank you all for your responses. I appreciate it.
 
murphey said:
The early Pipers (I've got a 180D also) did not have a POH, but a crappy AFH. So I bought the generic 180E "Owners Handbook" from Piper. Here are the specs. As a rule, a cherokee is a brick when it comes to glide. You'll notice there's no best glide:

Take-off Run (maximum effort, 25° flap) (ft) 720
Take-off over 50-ft barrier (maximum effort, 25° flap) (ft) 1625
Best Rate of Climb Speed (mph) 85
Rate of Climb (ft per min) 725
Service Ceiling (ft) 13,000
Absolute Ceiling (ft) 15,000
Top Speed (mph) 152
Optimum Cruising Speed (75% power, optimum altitude) (mph) 143
Cruising Range (75% power, optimum altitude) (mi) 725
Optimum Cruising Range (55% power, optimum altitude) (mi) 845
Stalling Speed (flaps down) (mph) 57
Stalling Speed (flaps up) (mph) 67
Landing Roll (flaps down) (ft) 600
Landing Roll over 50-ft barrier (ft) 1150

To make matters even more interesting, the Archer II POH has a Glide Range chart, assuming Power off, flaps up, 76 kts, and max 2550# (which is more than the 180D 2400# max). 76 KTS is 87 mph, by the way, so the 85 mph glide is about right. But remember glide is affected by weight, and the archer is heavier than the cherokee.
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The chart from an Archer "I" POH will get you closer:
Screenshot 2025-07-10 at 12.03.06 AM.png

It is 50 lbs. heavier than a Cherokee 180D, but also has a 2 ft. longer wingpsan which would tend to reduce induced drag and offset the increased weight, so 85 MPH is probably correct for a 180D. (It's also the recommended flaps-up landing approach speed in the operating instructions.)
 
It’s about 80 in ours when just me and instructor and utility weight.

Try it out. We worked with 85 too and found rate of descent to be worse than about 80. Still going to be a lot more difficult to nail a forced approach practice then typical Cessna.
 
midlifeflyer said:
Isn’t the power-off 180 in a Cherokee 180 basically,
1. Toss brick out of window.
2. Follow it down.
?
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Not exactly lol but it is a lot of stressful then a 172.

One time I knew I was low and could need to abort the forced practice before I “made” the field. Instructor was like try putting in a notch of flaps, it will pop you up and carry you over. Eh no. We just sank faster. Works in a Cessna, will kill you in a Piper lol.
 
I have a 73 180. It's the Archer body with a Hershey bar wing. The "Owner's Handbook" has best glide at 80 MPH (roughly 70 knots). I've done some long distance glides with the engine at idle and get roughly 9:1 glide ratio, it would be a bit less if the prop wasn't spinning or it was spinning a against compression in a non-running engine.
A good way to test for best glide achieved in your normal weight configuration is to go out early am no wind day and get to roughly 1 mile agl. Find a tall object like a smoke stack in the distance, say about 8 miles or so away, just short of where you can theoretically glide to. Find a target past the object that is aligned with the top of it. Edge of a field or highway is good. Go to idle and get to best glide speed. If the target rises relative to the object, your glide will reach the target. If the target falls below, you won't reach it. Play around with air speed to find where your best glide is. Allow the plane to stabilize at each speed for a bit to take energy surges out of the equation. It works best if you have a GPS that can give you relative wind as well. Also good to do it upwind and downwind to see the difference.

Slight rant on how instruction seems to focus on a cardinal speed (Vg) vs how to 1. Optimize glide and 2. Figure out pretty quickly if you can reach a target or not, so if not, you can quickly select an alternate. The last thing you want to do is fly over a perfectly good grass field trying to stretch a glide over a forest to a paved runway that you can't reach. Math alone won't tell you that. The target rising or falling relative to a feature in front of it is a good tool to have. Think a tree line before a runway. You can get a pretty good idea if you can reach it or not miles before you get there.
 
The only way to really get the numbers is, as @EdFred said, go out and test. Without knowing the exact numbers, you can approximate best glide by holding a level cruise pitch attitude, but that’s still not going to give you a calculated ratio.
 
Jim K said:
For all of the piston singles I've flown, best glide turns out to be the same as Vy. The FAA says it falls somewhere between Vx and Vy:
https://www.faa.gov/sites/faa.gov/files/2022-01/Best Glide Speed and Distance.pdf
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I've flown about 30 different types of singles and I think that's generally true of the Piper singles. Either Vy or within just a few knots. But in others, there can be a wider margin. Cessna single Vgs tend to be in that range between Vy and Vx. OTOH, in a Bonanza 3g or Mooney Ovation, Vg is more than 10 KIAS faster than Vy.
 
Racerx said:
If it's not in the POH you can't be tested on it.
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This is partly true. You can't be tested on it during a checkride. But you may be tested on it somewhat more directly when the engine quits.

As far as the Archer comparisons go, I think that all Cherokee 180s had Hershey bar wings while all Archers had tapered wings. I don't know how much that affects gliding.

As far as Vbg = Vy goes, it's worth experimenting. I determined Vbg in my RV-14 to be 75 KIAS, which is closer to the 70 KIAS Vx than to the 95 KIAS Vy. I would suggest to look for information about how to determine your Vbg, go and fly a bunch, and let us know what you find out.
 
iamtheari said:
This is partly true. You can't be tested on it during a checkride. But you may be tested on it somewhat more directly when the engine quits.

As far as the Archer comparisons go, I think that all Cherokee 180s had Hershey bar wings while all Archers had tapered wings. I don't know how much that affects gliding.

As far as Vbg = Vy goes, it's worth experimenting. I determined Vbg in my RV-14 to be 75 KIAS, which is closer to the 70 KIAS Vx than to the 95 KIAS Vy. I would suggest to look for information about how to determine your Vbg, go and fly a bunch, and let us know what you find out.
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The comment about Archers is not true. The Hershey bar wing was still on the first generation Archer, which was re-named from the Challenger. It was the Archer II (1976) that got the semi-tapered wing.
 
murphey said:
The early Pipers (I've got a 180D also) did not have a POH, but a crappy AFH.
Click to expand...
Actually, they called it the "Owners Handbook." Just like a car of the same era.

In the emergency section under power off landing, they do indicate the "best gliding angle" is 80 MPH IAS. Interestingly, in the E handbook, it goes up to 82.
 
Last edited:
SebIp said:
It’s about 80 in ours when just me and instructor and utility weight.

Try it out. We worked with 85 too and found rate of descent to be worse than about 80. Still going to be a lot more difficult to nail a forced approach practice then typical Cessna.
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Minimum sink speed is lower than best glide speed
 
....go out and test....you mean....stop the engine and then let it windmill....uhhh.....what could possibly go wrong....?
 
bbchien said:
....go out and test....you mean....stop the engine and then let it windmill....uhhh.....what could possibly go wrong....?
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Well if I can do OEI at night my first time in a twin - why not? Man it's been 20 years since that happened!
 
Jim K said:
For all of the piston singles I've flown, best glide turns out to be the same as Vy. The FAA says it falls somewhere between Vx and Vy:
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For me, Vg is 91.5 KIAS and Vy is 105. Vx is 85, so Vg is closer to Vx in my case - Sounds like that's similar to the Grumman and RV numbers posted above. Maybe efficient wings are closer to Vx and "pig wings" are closer to Vy? :D

Jim K said:
https://www.faa.gov/sites/faa.gov/files/2022-01/Best Glide Speed and Distance.pdf
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Non-broken link: https://www.faa.gov/sites/faa.gov/files/2022-01/Best Glide Speed and Distance.pdf

That doc is a good but quick read (2 pages).

SebIp said:
Try it out. We worked with 85 too and found rate of descent to be worse than about 80.
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Best glide speed is *not* the minimum descent rate - That's minimum sink speed, which usually isn't published and is slower than Vg. Minimum sink gives you more time in the air, but Vg will get you more distance.

midlifeflyer said:
I've flown about 30 different types of singles and I think that's generally true of the Piper singles. Either Vy or within just a few knots. But in others, there can be a wider margin. Cessna single Vgs tend to be in that range between Vy and Vx. OTOH, in a Bonanza 3g or Mooney Ovation, Vg is more than 10 KIAS faster than Vy.
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Other way around. Vg in the Ovation is nearly 15 knots slower than Vy; and just a handful faster than Vx.

One thing that should be considered in planning for a gliding scenario as well as executing it is the effects of wind. If you have a tailwind that is more than the difference between Vg and minimum sink, usually just a few knots, you'll get farther if you use minimum sink speed and ride the tailwind.

Likewise, since Vg is relative to the air and not the ground, if you have a headwind, you'll actually travel farther if you use a speed above Vg. And a direct crosswind is also effectively a headwind.
 
flyingcheesehead said:
Best glide speed is *not* the minimum descent rate - That's minimum sink speed, which usually isn't published and is slower than Vg. Minimum sink gives you more time in the air, but Vg will get you more distance.
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Vx is time/altitude and Vy is distance/altitude, so if you can eliminate drag from (feather) your prop, Vx should be your Vmin-sink and Vy your Vg.
 
billsgs126 said:
Vx is time/altitude and Vy is distance/altitude, so if you can eliminate drag from (feather) your prop, Vx should be your Vmin-sink and Vy your Vg.
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You're forgetting the effects of the vertical component of thrust on Vx and Vy... So I don't think your last statement is true. My Vy is significantly faster than my Vg. But, I can't feather my prop to test it. ;)
 
Don't forget that the book Vbg is specified at max weight. At lower weights, best glide will be slower (it's a square root relationship). So while knowing the book number is good, don't think of it as an absolute firm number. In practical application, flying a little slower than the published Vbg will probably work better, since you probably won't be at max weight.
 
Half Fast said:
Don't forget that the book Vbg is specified at max weight. At lower weights, best glide will be slower (it's a square root relationship). So while knowing the book number is good, don't think of it as an absolute firm number. In practical application, flying a little slower than the published Vbg will probably work better, since you probably won't be at max weight.
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The better . . . and this is something of a tautology . . . manuals contain a set of performance charts that show the variable nature of all of those book numbers based on weight and density atmosphere.
 
Half Fast said:
Don't forget that the book Vbg is specified at max weight. At lower weights, best glide will be slower (it's a square root relationship). So while knowing the book number is good, don't think of it as an absolute firm number. In practical application, flying a little slower than the published Vbg will probably work better, since you probably won't be at max weight.
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More on that in a thread @Hang 4 spun off from this one. The speed change with weight variations is easy enough to calculate. The performance hit you take by flying off optimum is not as simple but good to know for those who choose to use book Vg. I contend that it might be better to also publish the speed and performance at max zero-fuel gross weight but no traction as of yet. :cool:

Nauga,
falling with style
 
flyingcheesehead said:
You're forgetting the effects of the vertical component of thrust on Vx and Vy... So I don't think your last statement is true. My Vy is significantly faster than my Vg. But, I can't feather my prop to test it. ;)
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Perhaps, right now I am rigging up a fish scale to measure the Apache's horizontal component of thrust. :)
 
flyingcheesehead said:
Other way around. Vg in the Ovation is nearly 15 knots slower than Vy; and just a handful faster than Vx.
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Yep. I was reading my own stuff backwards.

Best Glide ............................. 91.5
Best Angle (VX)........................ 85
Best Rate (VY) ....................... 105
 
What is the difference in Vg when a prop is stopped vs windmilling, vs at idle?

Anyone got number for any airplane on that? I would think that for a 180D the difference wouldn't be enough to worry about testing it with the engine out.
 
EdFred said:
What is the difference in Vg when a prop is stopped vs windmilling, vs at idle?

Anyone got number for any airplane on that? I would think that for a 180D the difference wouldn't be enough to worry about testing it with the engine out.
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Well, if you idle at the "right" speed your small amount of thrust can equal the drag of the turning prop resulting in equilibrium.

A windmilling prop produces drag without contributing thrust. Feathering the prop minimizes drag. And that contributes to a flatter glide angle and increased gliding distance. The only place that I have seen this in print is a motor glider's POH. It offers the same 59 mph IAS for Vg and best L/D. But specifies an L/D of 27 with a windmilling prop and and L/D of 29 feathered.

When we flew the 1-26 sans canopy in summer, we just accepted the small impact on aerodynamics as the price to pay for comfort.
 
billsgs126 said:
Well, if you idle at the "right" speed your small amount of thrust can equal the drag of the turning prop resulting in equilibrium.

A windmilling prop produces drag without contributing thrust. Feathering the prop minimizes drag. And that contributes to a flatter glide angle and increased gliding distance. The only place that I have seen this in print is a motor glider's POH. It offers the same 59 mph IAS for Vg and best L/D. But specifies an L/D of 27 with a windmilling prop and and L/D of 29 feathered.

When we flew the 1-26 sans canopy in summer, we just accepted the small impact on aerodynamics as the price to pay for comfort.
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How does one feather a fixed pitch prop?
 
It works out to be 85 mph 900 fpm sink, 80mph 800fpm. Or similar. Math wise 80 seems to work out as maximum distance no?

Can try again but it is somewhere in the 80-85 mph range.
 
SebIp said:
It works out to be 85 mph 900 fpm sink, 80mph 800fpm. Or similar. Math wise 80 seems to work out as maximum distance no?

Can try again but it is somewhere in the 80-85 mph range.
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Interesting that Vg right around the approach speed. And in the Comanche it is as well, even though it's a gear up/down situation in the latter.
 
EdFred said:
How does one feather a fixed pitch prop?
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Well . . . maybe there is an STC to install an IO-360-B1E and a Hartzell HC-yada-yada . . . maybe one for retractable gear too . . . :biggrin:

But, in seriousness, I was trying to compare apples to apples. I don't recall any of the Airplane POHs I have read having differential glide data for windmilling props vs feathered. The motor glider POH offered both numbers.
 
some years ago, did the boring tests for my 1969 180D - result was Vg at 80mph for the majority of my flying weights (approx 400lbs under max weight)
 
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