Piper Cherokee glide speed and distance question

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Hi all,
After my close call a few weeks ago when my cylinder head crack in flight causing a partial loss of power, I have been thinking more about emergency situations and what I would do if faced with one of them.

I know that in the Cherokees that I rent, the best glide speed is 73. Is that calculated based on no flaps (clean)? I assume so. What would happen if you lose your engine and add 10 degrees of flaps? I know there would be extra drag but also probably some lift, so would that do anything positive as far as the gliding distance you could get?

Thanks.
 
Best glide is ALWAYS clean. Use flaps only to lose altitude when the runway is made (though arguably, a slip is better in that situation).

Best glide is 73 at max gross. It will probably be slower at light weights. TRY IT.
 
Concur. Best glide is always clean.
If you add flaps, you are adding lift but also drag. Try it clean and dirty and watch your VSI.
 
orange said:
Hi all,
After my close call a few weeks ago when my cylinder head crack in flight causing a partial loss of power, I have been thinking more about emergency situations and what I would do if faced with one of them.

I know that in the Cherokees that I rent, the best glide speed is 73. Is that calculated based on no flaps (clean)? I assume so. What would happen if you lose your engine and add 10 degrees of flaps? I know there would be extra drag but also probably some lift, so would that do anything positive as far as the gliding distance you could get?

Thanks.
Click to expand...

Go up with a CFI and try a few power off 180s in the pattern, those are always good practice for engine outs. And, if you ever decide to go after your Commercial License at least that'll be one thing you have down :).
 
MAKG1 said:
Best glide is ALWAYS clean. Use flaps only to lose altitude when the runway is made (though arguably, a slip is better in that situation).

Best glide is 73 at max gross. It will probably be slower at light weights. TRY IT.
Click to expand...

Or to stretch the glide in ground effect. Power off 180's in a Hershey bar wing Arrow taught me that one.
 
Just don't plan on gliding anywhere far away. Cherokees come down like bricks with the power out.
 
"Best Glide" gives tou the best ratio of lift to drag. While flaps increase the capability to produce lift at slower speeds, they don't actually give you more lift in flight...in the most basic equation, lift is still equal to weight.

Drag does increase, however, so the ratio of lift to drag decreases, so your glide gets worse.
 
While I was learning to do better crosswind landings in my Archer my CFI had me try landing using only the first notch of flaps. We found that to get the speed and descent rate we wanted, you had to nearly pull the power to idle abeam the numbers. I'm not sure how the hershey bar wing cherokees will do but with no or minimal flaps you might be surprised just how far it can go.
 
steingar said:
Just don't plan on gliding anywhere far away. Cherokees come down like bricks with the power out.
Click to expand...
cowman said:
I'm not sure how the hershey bar wing cherokees will do but with no or minimal flaps you might be surprised just how far it can go.
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My "Hershey bar" would glide at maybe 800fpm which did correspond with the POH numbers that said 1.7 nm/1000ft glide ratio at 70KIAS with no wind.
So yes, she does glide like a brick but the good news is that she DOES glide. :)
 
Not directly to the question but a good thing to do in any plane that you fly regularly is to find out how much up trim it takes to get from your normal cruise to engine out best glide speed. When I did that in my Cherokee 140, I found that I didn't need to count crank turns, just go to the up trim hard stop, then adjust from there if necessary for varying CG loading.
 
BigBadLou said:
My "Hershey bar" would glide at maybe 800fpm which did correspond with the POH numbers that said 1.7 nm/1000ft glide ratio at 70KIAS with no wind.
So yes, she does glide like a brick but the good news is that she DOES glide. :)
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That's 10:1. I think the 172 is 9:1.
 
800 fpm down at 80 to 83 mph = 9:1 +/- a tenth or two. I've seen different V speeds for the 140 in different year's books. Whatever the real performance is, it doesn't glide as well as a 172.
 
Could that be a function of the Cherokees feeling more nose heavy than a 172? That there's a perception that they glide like a brick, when the reality is they glide just as well, but feel clunkier?

I ask this not having any idea what a Cherokee flies like and base my experience exclusively on what I've read.
 
The glide performance of a 172 is virtually identical. A 182 is as well if you pull the prop.

They glide like bricks compared to jets or sailplanes, but not compared to other light singles.
 
I had a Cherokee for over 20 years. I had a surprise with the better glide performance of a CAP 172 when I had to do a simulated engine out off field approach to landing for a CAP check ride. It definitely did not come down as fast as the Cherokee.
 
BigBadLou said:
Concur. Best glide is always clean.
If you add flaps, you are adding lift but also drag. Try it clean and dirty and watch your VSI.
Click to expand...

Do not watch the VSI, best glide ratio is not the same as minimum sink. You could calculate glide ratios using VSI and airspeed but the instruments, particularly the VSI, really aren't accurate enough.
 
dmspilot said:
Do not watch the VSI, best glide ratio is not the same as minimum sink. You could calculate glide ratios using VSI and airspeed but the instruments, particularly the VSI, really aren't accurate enough.
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How do you recommend calculating?
I've figured just go up a few thousand feet, pick a point on the gps/find a vor to fly over using DME and simulate an engine failure and see how far you travel in loosing 1,000 or more.
 
farmerbrake said:
How do you recommend calculating?
I've figured just go up a few thousand feet, pick a point on the gps/find a vor to fly over using DME and simulate an engine failure and see how far you travel in loosing 1,000 or more.
Click to expand...

The no-wind range is tas*altitude/fpm/60. With wind, substitute ground speed for tas.
 
Graueradler said:
I had a Cherokee for over 20 years. I had a surprise with the better glide performance of a CAP 172 when I had to do a simulated engine out off field approach to landing for a CAP check ride. It definitely did not come down as fast as the Cherokee.
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That's been my experience. I tend to overshoot the first couple of landings when I fly a 172. Granted, an Arrow does actually come down like a brick with the gear down and flaps, but that's been the case even when I used to fly Cherokees.
 
Sac Arrow said:
That's been my experience. I tend to overshoot the first couple of landings when I fly a 172. Granted, an Arrow does actually come down like a brick with the gear down and flaps, but that's been the case even when I used to fly Cherokees.
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My experience with Cherokees has been that many of the V-speeds vary relatively rapidly with weight, and the POH only reports max gross. Best glide with two up front may very well be less than the POH says.

As an example, if you believe the Warrior POH, IFR in a Warrior above 4000 feet should be problematic because it can't climb at 500 FPM (on a standard day). But, on a slightly warmer than standard day, I managed to climb 500 FPM in one all the way to 8000. Solo, full fuel, climbing at 70 KIAS instead of the published Vy (79).

Cessna 100-series seem to be considerably less sensitive to that.
 
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