best glide speed of a warrior

George wrote:
d&tm wrote:

Wont the best glide speed also keep you in the air the longest? if not
what
speed will?

No, best glide doesn't do that. The best loiter speed is a bit lower than
that
for the best angle of climb. It's usually not published, but you can
determine
it pretty well by empirical experimentation.

Vms really has nothing to do with Vx. Vms minimizes power-off power loss,
Vx maximizes power-on excess thrust.

Vms is easy to calculate. It's just 76% of Vbg (make sure you do
IAS-CAS-*0.76-IAS; i.e. multiple CAS, not IAS).

Hilton

On Tue, 14 Dec 2004 06:50:15 +1100, "d&tm"
wrote in
::


Wont the best glide speed also keep you in the air the longest?

I believe 'best glide' speed is ebullient to maximum L/D speed which
will provide the maximum distance obtainable (in still air) for a
given AGL altitude.

if not what speed will?

As Maule Driver stated in Message-ID:
, 'minimum sink speed'
will yield the maximum time aloft (in still air or not) for a given
AGL altitude.

Both speeds are easily found if you have a polar diagram of aircraft
(airfoil) performance plotted on a grid with airspeed on the X axes
and vertical speed on the Y axes. There's an example here
http://www.afg.ethz.ch/Info/polaren.xls; click the 'Polar Chart' tab
at the bottom.

On Tue, 14 Dec 2004 at 06:50:15 in message
, d&tm
wrote:

Wont the best glide speed also keep you in the air the longest? if not what
speed will?

Nope. Minimum sink rate is close to maximum lift AoA.
Strictly, for simple math, it is at max (CL^(3/2))/CD.

Best glide angle is at Maximum CL/CD which is usually at a lower AoA
than minimum sink.
--
David CL Francis

In article , David CL Francis wrote:

On Tue, 14 Dec 2004 at 06:50:15 in message
, d&tm
wrote:

Wont the best glide speed also keep you in the air the longest? if not what
speed will?

Nope. Minimum sink rate is close to maximum lift AoA.
Strictly, for simple math, it is at max (CL^(3/2))/CD.

If you had a way to measure TAS instead of CAS, it would be
at almost exactly 2/3 of best glide speed for any reasonable
aircraft. This is only academically interesting, since airspeed
indicators are notoriously inaccurate at the low end of their
range. It's significantly slower, though. If you really want to
know what it is, you can determine it (roughly) by experiment.
You won't get an exact number without shutting down the
engine, but I don't recommend that.

Mike Beede

"Maule Driver" wrote in message
m...
The best glide speed in the book is calc'd at gross weight. At lighter
weights, the best glide will be lower. The calculation for best glide at
various weights is straight forward but I don't know it. I'm going to
guess
that it will be about 6 knots slower at empty weight plus a standard pilot
(can't wait to find out what the real number is)


See responses above, your 6 kts was a good guess,

Flying that speed accurately is valuable but perhaps not as valuable as
understanding the other major variable in doing an engine out glide to a
spot on the ground. That variable is wind. Since this is a ground
reference manuever so to speak, wind plays a signinficant role. The task
at
hand is generally "best glide speed for distance over the ground". If
you
are flying upwind to a spot, best glide speed will be higher. Downwind to
a
spot, a slower than best glide speed will take you further. Accurately
flying 73 knots to make maximum distance over the ground into a 20 knot
headwind is a mistake. (I'd guesstimate that 80-85 knots would be more
like
it).

excellent point about the wind, i can make sense of that, spend less time
going against the wind.



I don't know the formula for doing the calc and doubt you will have it if
faced with the problem. When faced with the problem, I had a gps driven
glide computer in my glider which would give you precise guidance based on
wind, glide polar, and vertical air motion.

I dont intend to be doing the calcs on the spot but to have some numbers in
the back of my head for different wts. I always have a fair idea of what my
wt is at any time.


A couple of rough rules of thumb
- err on the high side for upwind max distance glides - you really need to
go faster upwind and there is disportianate penalty for being slower than
optimal
- err on the high side for downwind - you can get a little more distance
by
going slower than best glide speed, but not much. Just fly best glide if
in
doubt

I'm really interested to see what the actual speeds are for different
weights and wind conditions.

Im interested in the wind calcs too now. thanks Maule. by the way what is
this Maule thing that you drive?

Terry