best glide speed of a warrior

Vx and Vy get a little more complicate with altitude change.
Vx increases with altitude, Vy decreases with altitude.

Robert M. Gary wrote:
BTW: There is a formula to get Vy, Vx, and Vso (and probably best
glide) for each weight. I don't have it in front of me right now. That
formula is on the Flight Engineer FAA written exam.

-Robert, CFI

Robert M. Gary wrote:
BTW: There is a formula to get Vy, Vx, and Vso (and probably best
glide) for each weight. I don't have it in front of me right now. That
formula is on the Flight Engineer FAA written exam.

Vs is easy, but modifying Vx and Vy for weight would be a very complex
equation if done correctly since it would have to compensate for propellor
efficiency, engine efficiency, etc as the airspeed changes.

Hilton

Terry wrote:
the best glide speed of a warrior is quoted as 73 kts. but best glide
should
be at best lift /drag ratio...

It is.


which I recall is at about 4 degree angle of attack.

Who told you this? CFI? POH? Seems awful low to me; I've never seen an
AOA quote for Vbg for a GA aircraft.


But this must be a function of weight.

The airspeed is, not the AOA.


So my questions are what weight is the 73 kts based on?

Best lift over drag as you suggest.


My flying school actually rounds it off to 75kts, regardless of weight.

Stupid. Fly 73, not 75 - if you can't fly 73, you need practise. There are
numerous rules of thumb, to get it accurately, scale by sqrt(weight) /
sqrt(gross) - ensure you use CAS, not IAS.

Hope this helps,

Hilton

"Hilton" wrote in message
nk.net...
Terry wrote:
the best glide speed of a warrior is quoted as 73 kts. but best glide
should
be at best lift /drag ratio...

It is.


which I recall is at about 4 degree angle of attack.

Who told you this? CFI? POH? Seems awful low to me; I've never seen an
AOA quote for Vbg for a GA aircraft.




The 4 degrees comes from my theory books ( trevor Thom) and I understand it
is pretty much the same for all light aircraft. which is why the wing is
usually set at this angle when the aircraft is level ( the riggers angle I
believe they call it) But since we dont have an angle of attack meter the
number is pretty much academic. the principle is that the best glide speed
is at a constant angle of attack and if the weight changes the speed to
achieve that angle of attack must change. I just wanted to understand how
much it changes.




But this must be a function of weight.

The airspeed is, not the AOA.

yes I agree, I didnt write this well but the change in airpseed is what I am
after, since we dont know tha aoa


So my questions are what weight is the 73 kts based on?

Best lift over drag as you suggest.


My flying school actually rounds it off to 75kts, regardless of weight.

Stupid. Fly 73, not 75 - if you can't fly 73, you need practise. There
are
numerous rules of thumb, to get it accurately, scale by sqrt(weight) /
sqrt(gross) - ensure you use CAS, not IAS.

Im certainly doing the practice and good pt about using CAS


Hope this helps,

It does, thanks
Terry

"d&tm" wrote in message
...
The 4 degrees comes from my theory books ( trevor Thom) and I understand
it
is pretty much the same for all light aircraft. which is why the wing is
usually set at this angle when the aircraft is level ( the riggers angle I
believe they call it)

The angle is called "angle of incidence", and while not just one factor
controls the choice of angle of incidence, most often the primary factor is
the desire to keep the cabin relatively level during cruise. Cruise speed
usually results in an angle of attack well below the "best glide" angle of
attack (and an airspeed well above Vbg).

I don't know off the top of my head what a typical best-glide angle of
attack is, but it's above a normal cruise angle of attack, and if 4 degrees
is a typical angle of incidence (and thus a typical cruise angle of attack),
the a typical best-glide angle of attack would be greater than 4 degrees.

Pete

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)

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).

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.

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.

"d&tm" wrote in message
...
the best glide speed of a warrior is quoted as 73 kts. but best glide
should
be at best lift /drag ratio which I recall is at about 4 degree angle of
attack. But this must be a function of weight. So my questions are what
weight is the 73 kts based on ? and how much does this best speed change
say
between maximum weight and minimum wight , or lets just say an 80 kg ( 176
pounds for the folks up over ) pilot flying solo with half fuel? Why ? I
am just curious, I like practicising my forced landings ( solo) and just
wondered how much extra time /distance i might get by flying at a more
"correct" speed. My flying school actually rounds it off to 75kts,
regardless of weight.
Terry

Maule Driver wrote:

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.

Several experts (people like Barry Schiff) claim that the best speed to use is
actually a speed which will keep you in the air longest. That gives you the most
time to attempt a restart and use the radio. The only time you should use best
glide is when you actually need to in order to reach a suitable spot to land.

George Patterson
The desire for safety stands against every great and noble enterprise.

"G.R. Patterson III"
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.

Several experts (people like Barry Schiff) claim that the best speed to
use is
actually a speed which will keep you in the air longest. That gives you
the most
time to attempt a restart and use the radio. The only time you should use
best
glide is when you actually need to in order to reach a suitable spot to
land.

That makes some sense. My thinking for an engine failure at altitude is to:
1) Slow to best glide
2) Point the plane in a useful direction
3) Concurrent with one, troubleshoot and communicate

To maximize time in the air, one would want to fly at minimum sink speed
which will be slower than best L/D. So the experts are suggesting not
flying at best glide but flying minimum sink. Hmmm. Don't think I agree
unless I don't have anything landable under me (open water), or my best
landing option is well with gliding distance.

"G.R. Patterson III" wrote in message
...


Maule Driver wrote:

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.

Several experts (people like Barry Schiff) claim that the best speed to
use is
actually a speed which will keep you in the air longest. That gives you
the most
time to attempt a restart and use the radio. The only time you should use
best
glide is when you actually need to in order to reach a suitable spot to
land.


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

Terry

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.

George Patterson
The desire for safety stands against every great and noble enterprise.