best glide speed of a warrior

[d&tm]

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

[john smith]

73 kts is the stall speed at max gross and aft CG.

Vs(actual)=[sqrt(actual wt/gross wt)]*Vso(gross)


d&tm wrote:
> 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.

[OtisWinslow]

73k stall speed? a Warrior? I don't think so or I'd have crashed on final
many
times.




"john smith" > wrote in message
...
> 73 kts is the stall speed at max gross and aft CG.
>
> Vs(actual)=[sqrt(actual wt/gross wt)]*Vso(gross)
>
>
> d&tm wrote:
>> 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.
>

[Hilton]

john smith wrote:
> 73 kts is the stall speed at max gross and aft CG.
>
> Vs(actual)=[sqrt(actual wt/gross wt)]*Vso(gross)

Vbg is the stall speed at max gross and aft CG? Where did you get that
from???

Hilton


> d&tm wrote:
> > 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.
>

[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

[Jay Somerset]

On Sun, 12 Dec 2004 22:43:48 GMT, "Hilton" > wrote:

> john smith wrote:
> > 73 kts is the stall speed at max gross and aft CG.
> >
> > Vs(actual)=[sqrt(actual wt/gross wt)]*Vso(gross)
>
> Vbg is the stall speed at max gross and aft CG? Where did you get that
> from???

It was either a brain fart, or a typo. :-)


>
> Hilton
>
>
> > d&tm wrote:
> > > 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.
> >
>

[Maule Driver]

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
>
>

[G.R. Patterson III]

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.

[Blanche]

According to the ASA "generic" Warrior Pilot's Guide, the Warrior II
(not the Cadet version) has the following airspeed limitations:

Vne 160 kts
Vno 126 kts
Va 111 kts at 2240 pounds
Va 88 kts at 1531 pounds
Stall 50 kts (clean)
Stall 44 kts (full flaps)

And remember, as per Kershner, stall & glide speed are dependent
on weight.

OBTW - same numbers for the Cadet (I just turned the page)

[Maule Driver]

"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.

[d&tm]

"john smith" > wrote in message
...
> 73 kts is the stall speed at max gross and aft CG.
>
> Vs(actual)=[sqrt(actual wt/gross wt)]*Vso(gross)
>
>
I am not talking about stall speed but it makes sense to me that the
calculation should be the same for the change in glide speed,

so if my best glide speed is 73kts at gross wt (1055 kg), then with just me
and half fuel at about 850 kg
this would give a speed of 66kts, which is a significant difference (
especially from the 75 the flying school suggests)

now that i think about it your equation makes sense. lift required should
be proportional to weight. but lift generated by the wing is proportional to
v^2. So for the same angle of attack it makes sense that the speed should
be a factor of
sqrt ( actual wt/gross wt). in the stall example you are just talking about
a different angle of attack ( 16 degrees) instead of the best glide angle of
attack (4 degrees)

thanks for the help John.

Terry

[d&tm]

"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]

"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

[d&tm]

"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

[john smith]

Yup, brian fart.
The equation is the same, just change the Vso to Vglide and the best
speed at reduced weight will be correct.

Jay Somerset wrote:

> It was either a brain fart, or a typo. :-)

[G.R. Patterson III]

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.

[Larry Dighera]

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.

[Robert M. Gary]

I usually have my student's fly final at 60. I would think we'd have
noticed if stall speed were 73. :)

[Peter Duniho]

"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

[Robert M. Gary]

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

[john smith]

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
>

[Hilton]

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

[Hilton]

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

[David CL Francis]

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

[Mike Beede]

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

[Jay Somerset]

On Fri, 17 Dec 2004 09:15:40 -0600, Mike Beede > wrote:

> 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

Actually, its much closer to 3/4 Vbg (not 2/3) 76% to be more precise.
This is also very close to stall AOA in most light GA aircraft, so you will
amoost certainly have the stall warning blaring at you if you try and fly at
Vmin-sink.