In article ,
says...

wrote in message
ups.com...

Dave Doe wrote:
In article ,
says...
On Thu, 2 Nov 2006 22:02:09 +1300, Dave Doe wrote in
:

fly at 65kts, and you get the longest time in the air

That is incorrect. Flying at best glide speed will give you the
maximum (no wind) distance over the ground just as Vy (velocity along
the Y axis: best rate of climb) does. Flying at minimum sink speed
will give you the most time before landing just as Vx (velocity along
the X axis: best angle of climb speed) provides the maximum height in
the shortest time (regardless of wind).

If the best glide speed is 65kts in a C172, what is the best min. sink
speed?

According to Kerschner, best glide speed (for distance) will be
around 1.3 Vs and minimum sink speed will be around 1.1 Vs. If the
airplane stalls clean at 50 kt, the minimum sink will be 55 kt and best
glide 65 kt.
But pay attention to the calibrated/indicated airspeed chart in
the POH. Airspeed indications are usually off quite a bit near the
stall.
One could go to altitude and do some gliding at various
stabilized airspeeds and find the one with the lowest rate of descent
on the VSI.

Another rule of thumb is lowest sink speed is 90% of best glide speed. So
for the C172
best glide 65 best sink 58.5
terry

Thanks guys.

--
Duncan