Looking for RV-6A advice

[akorchak]

Can anyone out there tell me if my RV-6A should do 160+ knots as Vans claims it should? If so, how come mine doesn't?

[flyeyes]

Hard to say without a lot more information.

A fairly thorough, independent evaluation of a clean, well-built example can be found on the web here:

http://www.cafefoundation.org/aprs/R...inal%20APR.pdf.

Van's numbers are realistic.

If you've had the engine looked over (to make sure it's capable of making rated power), The next step is to collect careful performance data for a baseline before changing anything. Kevin Horton's RV-8 website is the best place to start, and he has links to several techniques for measuring performance, and spreadsheets to make it painless. His flight test links can be found here:

http://www.kilohotel.com/rv8/phplinks/index.php?&PID=1

There is a very useful book on airframe cleanup and drag reduction available here:

http://www.buildersbooks.com/speed_with_economy.htm.

Kent Paser's airplane is a Mustang II instead of an RV, but the principles are the same.

It doesn't take much excess drag to slow these airplanes down, especially with a fixed-pitch prop (the slower airspeeds mean less RPM which means less power, etc.).

The first thing I'd look at would be wheel and gear leg fairings

James Freeman

[n468ac]

do you have all the fairings?
what engine?
what prop?
are you talking IAS, TAS, or Ground speed via GPS?
what Alt are you testing at?
what rpm?
what % power?

all these things come into play.

Our RV-6A just beats Vans numbers ... here's how we tested;
1. tests need to be at 8000' pressure ALT (set your ALT to 29.92)
2. 75% power ... at 8000' thats WOT without going past 2700 rpm
3. level, trimed, and mid-high max weight
4. All IAS need to be converted into TAS.

with that said we just beat Vans numbers.

[szicree]

Here's a couple of no cost checks:

1. Wing incidence
2. H. stab incidence
3. Go fly with no pants or gearleg fairings.

1 and/or 2 out of whack will require excess trim input and slow 'er way down. Regarding 3, misaligned fairings may be worse than no fairings.

Steve Zicree
RV4 finishing

[Kahuna]

Originally Posted by akorchak

Can anyone out there tell me if my RV-6A should do 160+ knots as Vans claims it should? If so, how come mine doesn't?

The short answer to your short ? is easily.

Everything depends. We need way more data.

[baisicrv]

Was hoping for any suggestions that came out of this thread to see what to look for on my 6a.I did not build but am going through it to clean it up.I am runnning the 0320-160 hp,sterba wood prop and older wheel pants.I only can get 150 mph at 7500 feet using gps in triangle pattern to count out wind factor.I am replacing wheel pants with new style shortly.Any other suggestions on what to look for that slows them down?Thanks

[jclark]

When you fly it, at what RPM are you running for the stated speed?

As mentioned, more data is required.

With our 1105 # (empty) RV6, O320 - 160HP, Ed Sterba Wood Prop (forgot the pitch) at 4500 ft, ~25+" MP and ~2600 (2650??) RPM with OAT of ~65*F, I was getting a True Airspeed of 160-163 knots. Pushed it a little harder and got to 165 kts.

Normally plan for 150 knots.

I have been able to turn up to 2850 RPM during flight testing but I do NOT run it at that RPM.

Do a few runs and report back with the data.

Many people will sasy go to 8000-8500 feet and push the throttle to wide open. Let it settle (do not go beyond any limits your equipment may have) and record the results.

Capture GPS groundspeed, Indicated Airspeed, Heading, Outside Air Temperature and Barometric Pessure for the area on 3 tracks 120 degrees apart or 4 at 90 degrees apart.

Another area ... if your flaps are ALL THE WAY UP and if you hold one of the ailerons perfectly aligned with the flap, is the OTHER aileron and flap aligned **and** are the wingtips on BOTH sides ALSO aligned with all of this???

Third idea (don't remember if this was mentioned already) ... are the gear leg/fuselage fairings staying in place during flight?? Are the screwed on and NOT moving? I have personally seen one of these slip down in flight on a friends plane and it REALLY slowed him down.

Just a few thoughts.

GOod luck,

James

Originally Posted by baisicrv

Was hoping for any suggestions that came out of this thread to see what to look for on my 6a.I did not build but am going through it to clean it up.I am runnning the 0320-160 hp,sterba wood prop and older wheel pants.I only can get 150 mph at 7500 feet using gps in triangle pattern to count out wind factor.I am replacing wheel pants with new style shortly.Any other suggestions on what to look for that slows them down?Thanks