Today's Message Index:
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1. 06:09 PM - Vx Vy Best glide (N395V)
2. 06:40 PM - Re: Vx Vy Best glide (Fred Weaver)
3. 06:50 PM - [Fw: Photos from the Frozen North] (Norman Younie)
4. 11:54 PM - Re: Vx Vy Best glide (Morocketman@aol.com)
Message 1
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| Subject: | Vx Vy Best glide |
--> Rocket-List message posted by: N395V <N395V@direcway.com>
Blank
What is everyone using as Vx Vy and best glide?
Message 2
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| Subject: | Re: Vx Vy Best glide |
--> Rocket-List message posted by: "Fred Weaver" <Mytyweav@earthlink.net>
This ought to be good......
----- Original Message -----
From: "N395V" <N395V@direcway.com>
Subject: Rocket-List: Vx Vy Best glide
> --> Rocket-List message posted by: N395V <N395V@direcway.com>
>
> Blank
> What is everyone using as Vx Vy and best glide?
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Message 3
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| Subject: | [Fwd: Photos from the Frozen North] |
--> Rocket-List message posted by: Norman Younie <rv6capt@pacificcoast.net>
Message 4
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| Subject: | Re: Vx Vy Best glide |
--> Rocket-List message posted by: Morocketman@aol.com
An excellent question. And an excellent explanation can be found on my
local "Missouri Pilots Association" web site written by our own Larry Harmon.
See mopilots.org/sgf/jan2001sgf2.htm. Larry describes the generic values for
Vx, Vy, and Best Glide speeds, and these are fine for the Rocket. I just add
the caveat that the Rocket has such an abundance of power that Vx is really
on the edge should the Lycoming get quiet. It is generally agreed (by most
test pilots) that Vx is/or about Vs + 20%. Commonly expressed as 1.2 x Vs. In
my Harmon (no relation to Larry) Rocket II, Vs is about 55 to 56 knots
depending on who is counting. Computing Vx of 66 knots at full takeoff thrust
would give a body angle that would be very, very dramatic. Assuming something
came undone, it would require a very rapid pitch over to maintain some
semblance of control near/above the desired Va approach speed (Vs + 30% or 1.3
Vs
or 73 knots which is the perfect over-the fence feel airspeed). It is simply
not necessary. My airplane climbs like a "rocket should" at 1.4 x Vs or 78
to 80 knots. Now, to address a very different
subject......................... Vy. Oh what a strange, and vague speed that
is, and how do we find it?
Technically, Vy should be 1.4 Vs, again the 78 knot number which coincidentally
should also be best glide speed. My explanation is that we are much like a
Century Series jet fighter...........they simply forgot to put enough "wing
on the thing." An RV-? wing of any kind is a short span, dare I say chubby
cord, and thick wing. When we clipped our RV-4 wings to the Rocket length, we
knew we were going the wrong way for gliding. Just look at the high
performance sailplanes with their extremely high aspect ratio "straight razor"
looking wings. My RV-4 felt-about-right at 85 knots for Vy, and my Rocket is
a
whole lot more like 100 knots. If I lost the engine on the Rocket, and was
able to get it to course pitch, I would think a great deal about 90 to 100 knots
until the last three hundred feet. And only then would I reduce to the
desired 73 knots IAS. I know the other factors like weight, wind gusts, density
altitude, etc., but these are just guidelines from my own very humble opinion
and 700+ hours on the stubby RV wings. Ya'll be careful out there, and
mainly fly the airplane where you (and it) feel comfortable. Les Featherston
"Airgasm" 228 hours, and just lovin' it!
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