V-Speeds for  Fly Babies

Posted September 2003

Other than the Vne of 135 and the listed Vs of 45 MPH, Pete never, as far as I know, established any V-speeds for the Fly Baby.  I got asked off-list
about what some of the other speeds should be.  FAR Part 23 has instructions for calculating the numbers for production-type airplanes, so I ran the equations for the Fly Baby.

For instance, the cruising speed (Vc) is defined (in knots) as 33 times the square root of the wingloading... that's 33 * sqrt(925/120), or 91 knots (105 MPH).

Maneuvering speed (Va) must be the higher of either Vc or the stall speed times the square root of the load factor used in the design.  If we assume the Fly Baby is equivalent of the utility category (4.4 limit load), that's 95 MPH.  Let's split the difference and call the maneuvering speed 100 MPH.

The final number is the maximum structural cruising speed (Vno).  FAR 23.1505 defines Vno as not less than Vc, and not more than .89 times Vne. That would be 120 MPH.

     Vs:   45 MPH
     Vc:  100 MPH
     Vno: 120 MPH
     Vne: 135 MPH

Best rate of climb and best angle of climb speeds are generally 1.3 or 1.2 times Vs, respectively.  That would be Vy at 58 MPH and Vx at 54 MPH.

Remember, these probably do NOT match your own airspeed and static setup. On N500F, I used 70 MPH for best rate.  Moonraker's airspeed seems a bit off (and it's heavy) so I use 75 on it.

Comments? Contact Ron Wanttaja .