Can you explain the thumb/finger glide estimate technique a little better?  Or suggested a reference for additional reading?

Always wanted to get some glider time/training.  Your post got my interest peaked again.

Thanks,

Rick

 

p.s. During my multi-engine training, I once (too quickly) shut down the good (wrong) engine after the instructor had purposely shut down the first.  Big mistake - it got very quiet.  The restart was uneventful, but the few seconds of pure glide are still very vivid in my mind.

 

 

 

Grayhawk wrote:
> Bob, I am glad to see you mention the 10:1 ratio, would you use
> that ratio if you lost the engine and the prop was still rotating?

First, I should say that I probably have more engine-out and off-airport
landings than landings at airports and with an engine. I've been flying
hanggliders and sailplanes for 20+ years. There's a cliche about the
glider pilot who goes to get his engine rating added to his pilot license.
After a few lessons, the instructor pulls the throttle. While most power
pilots tense up at this point, the glider pilot heaves a sigh of relief
and continues the flight to the planned destination :-)
Occasionally that is literally true.

Back to the Lancair though... it would take a tremendous thermal
to climb away from the ground without the engine, so assume
I'll be landing soon after the engine quits. In still air, with mixture
pulled to cutoff, I see about 700 fpm descent at 100 kias.
That's pretty close to Paul's 15:1 idle-glide ratio.

If the engine quits over inhospitable terrain, I'll figure about
500 ft lost per mile. I'll also be aiming for a field within about
7:1 glide to a point 1000 feet above the field.
I'll be using visual cues primarily.  With my thumb against the
bridge of  my nose, I put the top of my index finger on the horizon.
If I can see something under the finger, I can fly to it with a 7:1 glide.

For 15:1, I use the tip of my thumb against my forehead and
put my pinky fingernail on the horizon. The pad of the pinky is
little better than 15:1.

Likewise I fly angles through the pattern to landing rather than numbers.
This is especially important at a field you've never seen before, at
an unknown altitude, and with no services (or paved runways).
I could go on for hours about how to identify a good field versus a
bad field for landing. There are literally hundreds of visual cues you
can use to identify a field's slope, texture, hardness and so on.
Similarly there are many ways to see wind direction without a
windsock or an AWOS.

One of these days, I'll go out to Castle Air Force Base and measure the
glide ratio of my 235 with the prop stopped. If I can stop the prop, I'll measure
sink rate at a few speeds before landing on the 12000 foot runway.
Like Gary, I'll be using about 3000 feet of that for the actual landing.

-bob mackey

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