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todehnal

Well Known Member
Can anyone offer some real world stall speeds for me.
Really, I would like to know how effective the RV-4 flaps are.
Van post the gross weight stall at 54 mph and the solo weight stall at 48. I'm sure that these are dirty figures and need to know the clean numbers.

Thanks for your help.

Tom
 
todehnal said:
Can anyone offer some real world stall speeds for me.
Really, I would like to know how effective the RV-4 flaps are.
Van post the gross weight stall at 54 mph and the solo weight stall at 48. I'm sure that these are dirty figures and need to know the clean numbers.

Thanks for your help.

Tom
Click to expand...
Since you don't specify, I don't know if you are interested in calibrated airspeed or indicated airspeed. There is generally a big difference at these low speeds and those that might want to reply would be helped by knowing.

I doubt if many folks go to the trouble to determine CAS stall and the IAS stall varies greatly, airplane to airplane.
 
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As Larry said, there is no point at all to comparing IAS stall speeds. The airspeed system accuracy and ASI instrument error would quite likely be different at the two conditions, so you can't compare the IAS numbers. But, the CAFE Foundation did do stall speed testing on an RV-6A and RV-8A, with a flight test airspeed boom. The airspeed boom put the pitot and static sources well ahead of the wing, so the position error should be very low. The ASI was also calibrated, so their stall speed numbers are probably quite accurate CAS values. The only gripe I have with their results is that they apparently did not use idle power for the stall speed tests. Instead, they set some higher rpm. Thus their stall speed numbers are probably a bit lower than they would be if they had used a FAR 23 type test technique. But, their results probably give a reasonable idea of the effect of flaps on stall speed.

RV-6A APR - flaps up stall = 58.7 mph CAS. Flaps down stall = 52.1 mph CAS. Thus the maximum coefficient of lift would be 27% higher with flaps down than with flaps up.
RV-8A APR - flaps up stall = 60.4 mph CAS. Flaps down stall = 54.2 mph CAS. Thus the maximum coefficient of lift would be 24% higher with flaps down than with flaps up.

The CAFE Foundation results show that the flaps on the RV-6A and RV-8A were quite effective. The flap design on the RV-4 is essentially identical to the -6 and -8, so I would expect similar results.
 
Indicated or Calculated

Since I don't know what Van used to determine his specifications, I am not sure which to ask for. Actually, the RV-6 Stats and the 4 numbers that were posted, really give me a good idea as to the effectiveness of typical RV flaps. Much better than I expected
Thanks for the responses

Tom
 
Stalls

I know IAS is not ideal for comparison here are my numbers:

IAS: clean 57 mph
IAS: full flaps 53 mph
 
RV-4 Stall Speeds

My RV-4 solo w.full fuel, CG ~21%MAC stalls at 45KCAS clean and 43KCAS full flap, idle (FP prop).
 
Slow flight...

My RV4 stalled at 50 mph indicated dirty, (46 knots) with the GS normally close. My Rocket stalls at 55 knots but will hang on the prop in the buffet down to zero knots. The flaps do help, if for nothing else, tighter turns while dogfighting...:)

For what it's worth...

RR
 
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