----- Original Message -----

Sent: Monday, May 03, 2004 2:10 = PM

Subject: [FlyRotary] Tail Wing=20 Incident

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From:=20 Tracy = Crook
To: Rotary motors in = aircraft=20

Sent: Monday, May 03, 2004 = 2:42=20 PM

Subject: [FlyRotary] Re: = Injector=20 testing

I = probably am=20 overpropped at static and low speed. I told Clark Lydick to = build me=20 a speed prop. I figured that being overpropped on take-off doesnt = matter=20 if you have lots of HP and can get off the ground in 1200 ft and = climb=20 like a banshee anyway. I'll be sending the prop back for = adjustment once I=20 get solid numbers, but I don't think I'll want him to cut it back=20 much.

john = Slade

What sort of top speed, = and cruise=20 speed do you expect? What would be common for = an=20 O-360 powered=20 = plane?

Cheers,

Rusty (wishing the RV = airfoil wasn't=20 so draggy over 220=20 mph)

I used to think the same thing (draggy=20 airfoil) but I think the problem with RVs over 220 is = related to=20 wing / tail / fuselage incidence.   At 220 = I get the=20 visual impression that I am in a dive during level=20 flight.

&nbs= p;

The early Citation jets used the same = airfoil as=20 the lowly RV.

&nbs= p;

Tracy

&nbs= p;

Tracy,=20

&nbs= p;

   As you known, the airflow = over the=20 horizontal tail is such as to exert down force on the tail (Nose = up) to=20 overcome the forward pitching movement of the CL of the wing=20 airfoil. I suspect that at the higher airspeeds the airflow = over the=20 wing could be changed sufficiently that the tail surface might be=20 providing less downforce (nose up ) than = required.  =20 In otherwords the downforce on the horizontal stab is=20 sufficiently lessened that the nose lowers until the horizontal = stab finds=20 a new equilibrium point at your higher airspeed. As nose = goes down,=20 more of the upper surface of the horiz stab is exposed to the = airflow=20 causing more down force/nose up until the new equilibrium is=20 reached. Just a=20 thought.

&nbs= p;

&nbs= p;

&nbs= p;

Ed

Ed

Not questioning anything you just = stated. Keep in mind also, that with the dynamic pressure = increasing=20 as the square of the speed, the required angle of attack of the = wing is=20 reduced and the nose goes down from that alone. I am not = sure what=20 the CL shift is as the AOA decreases with increase in speed. = Tracy=20 is seeing AS numbers that I will never see on my 9A.

Dean Van Winkle    = RV-9A  =20 13B