---------------------------------------------------------- Rocket-List Digest Archive --- Total Messages Posted Wed 09/21/05: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 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 _____________________________________ Time: 06:09:13 PM PST US From: N395V Subject: Rocket-List: Vx Vy Best glide --> Rocket-List message posted by: N395V Blank What is everyone using as Vx Vy and best glide? ________________________________ Message 2 _____________________________________ Time: 06:40:37 PM PST US From: "Fred Weaver" Subject: Re: Rocket-List: Vx Vy Best glide --> Rocket-List message posted by: "Fred Weaver" This ought to be good...... ----- Original Message ----- From: "N395V" Subject: Rocket-List: Vx Vy Best glide > --> Rocket-List message posted by: N395V > > Blank > What is everyone using as Vx Vy and best glide? > > > > > > ________________________________ Message 3 _____________________________________ Time: 06:50:43 PM PST US From: Norman Younie Subject: Rocket-List: [Fwd: Photos from the Frozen North] --> Rocket-List message posted by: Norman Younie ________________________________ Message 4 _____________________________________ Time: 11:54:33 PM PST US From: Morocketman@aol.com Subject: Re: Rocket-List: 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!