RV-6A Stall Speeds

[beberle]

I'm trying to figure out why my RV-6A shows an indicated stall speed of 65mph/57kts for all phases of un-accelerated stall (clean, 15deg, 30deg, 40deg). I can believe 57kts clean, but full flaps? Looks like I have standard static ports and not Van's rivet head style. However, I would think there would be 'some' difference in stall speeds. Cruise speeds line up perfectly w/ GPS...

thoughts?

[cfiidon]

My -8 was showing stall speed about 5 kts higher than it should. I recently discovered I had a couple of static leaks. Airspeed checks with GPS only showed about 1-2 kts off.

Give your static system a checkout if you haven't done so already.

Don

[Pmerems]

I fly an RV-7A with the Van's stock static port (pop rivet). No leaks in my static or dynamic systems. My indicated airspeed is about 4 kts slower then actual. I have confirmed this at low and high speeds using the test pilot GPS calibration spreadsheet after collecting data from several flights (search for previous posts on airspeed calibration).

So my indicated stall speeds are about 4 kts lower then Van's published numbers.

[664781]

Brian,
My 6A stalls full flaps at 63 MPH and I have the Van's rivets for static ports. Cruise speeds are good, so I just marked it up to the high angle of attack at stall speeds.

[plehrke]

Watch your altimeter next time you take off and see if your altitude changes as you roll faster down the runway (before lift off). If it reads different then before your take-off roll then your static system is not reading true static.

[beberle]

I'm getting ready for annual inspection, so I'll check for static leaks.

Even w/ a static leak, I would expect the stall speeds to be at least a few kts different between clean and full flaps. Or maybe not? 65mph is good bit higher than specs, but sounds not unreasonable. After 1yr together, I know this will be a lasting relationship ;-)

[tmendy]

With the posted numbers it really looks like there's something wrong with the pito lines and/or ASI instrument.

Vans published numbers dirty, are 49mph (42kts) light, and 55mph (47kts) heavy.

Our 6 ASI reflects those published numbers.

For safety considerations in any plane new to me, I do slow flight until stall indication. In small planes I'll let it buffet or drop a wing, then document that stall number.

Trust, but verify the numbers!

After confirming, when low I always fly at least 50% above VSO combined with max bank of standard rate turns or less until stabilized final.

Then VSO plus 30% (Vref) on final bleeding off some more if the winds are light and the field is short.

It's just tragic to see so many general aviation "slow and low" accidents happen that could be avoided with proper speeds and bank angles

[Mel]

My -6 stalls at 60 mph IAS clean and 53 mph full flaps.
I have the "pop-rivet" static ports as called out in the plans.

[plehrke]

Originally Posted by Mel

My -6 stalls at 60 mph IAS clean and 53 mph full flaps.
I have the "pop-rivet" static ports as called out in the plans.

Kind of a side question: Should the POH list stall speed (or maybe performance in general) as CAS or IAS? I currently have CAS listed but the reality of when flying and referring to the numbers in the POH you are going to use IAS, since that is what you read off the instrument (unless you can put a calibration curve into your glass panel somewhere to have it read CAS). I fly with the good old fashion airspeed indicator so maybe IAS is what the POH should reference.

[Mel]

Yes, I agree that IAS should be listed in the POH, simply because as you say, that's what you read directly in the cockpit.