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DEAR ED;
HERE'S A TRICK that worked well in my Cherokee. When you lose your
engine or just practicing. Give her full up trim. The plane will assume its
proper glide speed and stabilize there. Then you can do other important things
like picking a soft spot to land. I cut power at 7000 ft and 12 miles from the
base and easily made the field.
Works in a Coupe to. Works in any plane I have tried it in.
The important thing is by stabilizing the glide you are free to pick a
field, try for a restart etc. etc..
BOB
----- Original Message -----From: Ed BurkheadTo: CtechSent: Saturday, April 08, 2006 6:12 PMSubject: RE: [COUPERS-TECH] power off descend----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
Hartmut wrote:
> I then took the time to measure the actual sink that happened
> over one minute and the altimeter measured merciless 800ft.
>
> It turns out that my best glide speed is between
> 60 to 70 Miles indicated on my airspeed meter and that it is
> around 800ft/minute. Maybe less with some luck, more if you
> hit a downstream.
>
> At 4000 ft altitude above ground I would have 5 minutes glider
> time until I touch ground. At 60 Miles/hour, I would have 1
> mile/minute, giving me a radius of 5 miles (8 km) to find a
> suitable spot for landing, provided no wind condition.
Hartmut,
As I understand it, you tried several airspeeds to find which one gave you
the minimum sink rate - i.e. the longest time in the air.
I think you will find that the best glide ratio and best glide range will
happen at a higher speed. At 75-85 mph, I think you will find that you have
a higher sink rate but you will also have higher forward speed.
Based on your 800 fpm sink rate at 65-70 mph you get 5 minutes, as you said.
During that time, at 60 mph, you could travel 5 miles, as you said. That's
5280 * 5 = 26400' of forward motion. Dividing by the vertical drop of
4,000', you get a glide ratio of 6.6. That's not very good, as we all know.
As I recall from ground school, the best duration glide speed usually gives
a far shorter glide than does the best range glide speed.
Sometime when you can fly again, please try it at higher speeds. You only
need to measure the sink rate (via altimeter and stopwatch) at each speed
and record the airspeed and temperature. Then, using your whiz-wheel you
would correct the indicated airspeed value to be the true airspeed.
With that data, we'd compute the glide ratio and glide range again.
When I did it with my old, inaccurate airspeed indicator, I was surprised
how good the glide ratio seemed to be at the higher airspeeds.
Thanks for providing real, hard data with which to calculate.
Ed Burkhead
http://edburkhead.com
ed -at- edburkhead???.com (change -at- to @ and remove "???")
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