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Catto 68x74

Jamie Aust

Jamie Aust

Well Known Member
I would like anyone with the same prop as mine to reply with your TAS at 8K.
I have been reading all catto posts and have not found anyone with the same prop as me.

pa130041.jpg


All leg and wheel pants etc are on. Only 1 com and 1 Txpdr antenna. 2 steps.
0360A1A, Plenum, 1 mag, 1 plasma II. Prop balance only a few weeks ago.

If the weather is better on the weekend, I will post the new findings of a gps box run at @8K WOT.

I dont seem to be able to get over 150kts just now. Im also going to go over my static system to see if that could be a problem.
 
Hi Jamie,
Going by the date on your prop's sticker, I am a little confused. I thought Craig stopped making the 68" prop about a year before yours was manufactured. I may be misremembering, but I thought his latest design was "more efficient" and it was a 66x74.

Whether I'm misremembering or not, I recall a conversation with Craig when I ordered my prop where he said the new design gave the same performance, if not 1 mph faster.

I've had my RV-7A up to 187 knots TAS. I'm guessing your static or pitot lines are leaking. Have you compared your airspeed with a GPS going 3 different directions (to compensate for wind)?
 
Thanks Sonny,

Im going to look over my static / pitot system, then do some more box gps runs. I hope its just a leak in the system.

ok, if 66x74 is the new style prop, anyone with that combo please tell me your TAS.
 
I Received my prop April 2011.
It is on a IO360-A1B6 200hp.

At a DA of 8080 WOT I'm getting 176Kt 2780rpm.

at 2700rpm I'm getting 170kt tas

I need to do some work on the snorkel, I think I'm losing about an inch of manifold pressure. On the ground engine off, I'm showing 28.2 inches hg.

full throttle on the ground 27.4. I took off and stayed just above the runway and it moved up to about 27.6.

I plan to paint in a couple weeks, and plan pull the prop and send it back to craig for re-pitch to bring the rpm down 100 RPM.
 
Catto -68x74 TAS

lostpilot28 said:
Hi Jamie,
I've had my RV-7A up to 187 knots TAS. I'm guessing your static or pitot lines are leaking. Have you compared your airspeed with a GPS going 3 different directions (to compensate for wind)?
Click to expand...

Can you tell me a bit more about your engine configuration? About the max I have seen is 178kt and the engine is taching over 2800rpm.

thinking I was slow, I did multiple gps runs and confirmed the tas was about 3kt lower than actual.

I did some static ports tweaking and now my SV D1000 TAS is a knot or so faster than actual.
 
Hi Larry,
I have an ECI O-360, 180 hp engine. Dual P-mags, 8.5:1 compression. I have the Sam James cowl and plenum setup, which seem to be faster, but the cooling is worse. I had all the wheelpants on, airplane was painted and clean...and I think the aircraft's loaded weight was around 1650, so this wasn't at gross weight. Also, I think I was flying at about 5,500 ft density altitude that day.

Truth be told, I think it would've gone 1 or 2 mph faster...but I got tired of waiting for it to claw it's way up there...the air wasn't smooth enough!
 
I also did some static ports tweaking. This is what we found yesterday. All in KTS.

Max static on the ground 2240 rpm, Max at alt was 2740 rpm, on climb out just after takeoff 2440 rpm,

GPS box RUN 1 @ 2500 ft OAT 22 C Full fuel WOT, TAS 169

N 176
E 154
S 160
W 181

RUN 2 @ 3000 ft OAT 17c WOT 2450 rpm 34 ltrs ph TAS 145

N 155
E 137
S 140
W 157
 
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Jamie Aust said:
I also did some static ports tweaking. This is what we found yesterday. All in KTS.

Max static on the ground 2240 rpm, Max at alt was 2740 rpm, on climb out just after takeoff 2440 rpm,

GPS box RUN 1 @ 2500 ft OAT 22 C Full fuel WOT, TAS 169

N 176
E 154
S 160
W 181

RUN 2 @ 3000 ft OAT 17c WOT 2450 rpm 34 ltrs ph TAS 145

N 155
E 137
S 140
W 157
Click to expand...

Jamie,

I have the same prop same pitch, and an O-360. Your max static and max WOT RPMs at altitude are right in line with mine. I'm seeing at 8000 density altitude WOT, a True airspeed of 205 mph. That was before paint, but with all of the fairings installed. We are pretty close in numbers other than your at 2500 ft, so I would check your static system.
 
sbarger24 said:
Jamie,

I have the same prop same pitch, and an O-360. Your max static and max WOT RPMs at altitude are right in line with mine. I'm seeing at 8000 density altitude WOT, a True airspeed of 205 mph. That was before paint, but with all of the fairings installed. We are pretty close in numbers other than your at 2500 ft, so I would check your static system.
Click to expand...

I don't know, Steve...you're 11 kts faster...that's not very close! Because Jamie is indicating close to the same RPM at WOT as me, I'm guessing he still has a pitot or static leak, or his instrument is out of calibration. 25 kts between my RV and his is pretty big, and I'd guess that if his airplane was draggy he wouldn't be generating the same RPMs. I think I was turning 2780 or so when I did 187 kts.

I guess my point is, wouldn't his engine be lugging more than that if he was going that much slower? Also, are you sure your prop is pitched the same as his? I thought you and I had 66x74.
 
Steve,

Jamie's static is now correct. Or should I say the calculated TAS based on the EFIS, compared to the GPS box data is within 1 to 2 knots.

I think realistically it will do around 200MPH or 172 knots when leaned for best power at altitude.

Doing a GPS box and comparing the result to your calculated TAS based on instruments is a very important task. If at around 150 knots +/- 30 you are within 2 knots, I would say all is good. Your altimetry and encoder will be within say 25 feet. If you are out by say 9-10 knots, your altimetry is well over 120 feet out :eek: And depending on where you are in the world that makes you out of tolerence before you start!.

Read up on Kevin Hortons posts.... he is the guru :)
 
just went up this afternoon. climbed till the dynon DA said 8000.
rpm 2760 ff 11.4 mp 24.3
gps box averaged 180.75kt fairings on, no paint.

I am thinking I want the RPM maybe 100 less. Does anyone have before and after re-pitch data? I certainly don't want it too low, after all rpm is power. :)
 
NDrv8r said:
just went up this afternoon. climbed till the dynon DA said 8000.
rpm 2760 ff 11.4 mp 24.3
gps box averaged 180.75kt fairings on, no paint.

I am thinking I want the RPM maybe 100 less. Does anyone have before and after re-pitch data? I certainly don't want it too low, after all rpm is power. :)
Click to expand...

Larry,

Your prop is performing perfectly as designed... IMHO, I would pass on the re-pitch. :)
 
Lostpilot
I think I was turning 2780 or so when I did 187 kts.
Click to expand...

Was this 187knots a genuine GPS box confirmed true airspeed, or was it just what your instruments told you? :confused:
 
I did not do that run in a GPS box...but I did calibrate my instrument a few months prior to that using Dan Horton's spreadsheet. It was spot on...less than 1/2 mph difference between the average GPS and the instrument. Now, I'm not claiming nothing changed in my pitot or static system, but I would think a leak of some kind would make my instrument read slower, not faster.

Also, keep in mind I was not at gross weight. Van's website states 208 mph is "Top Speed" for 180 hp RV-7A, at solo weight. Gross weight is just 1 mph slower. Also, Craig Claims his props are "3 or 4 mph faster" than Van's numbers. The same claim is made by Sam James for their cowl & plenum. I don't think that's cumulative, but I believe they all will make better speed when combined.

Either way, I got 7 mph faster than Van's claimed top speed number. That's not very much, but I believe it to be accurate. I do plan on checking it again this weekend if possible, and I'll report back with the results.

Edit: I forgot to mention that I'm also running dual P-Mags. They burn the fuel/air more completely, and they have spark advance.
 
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Thanks for the feedback !

Looks like rain here for the next few days until Sunday, so im not able to give an update till then.
Here is a picture of my plane so you can see if it looks draggy or not.

ycabdbtm.jpg


The last test I posted was at gross, ie 2 people, full fuel.
RE: my instruments, Im running dual 10" skyviews,with dynon gps, they seem to be very accurate. We used a spreadsheet on the ipad to calc the numbers of the GPS box runs.

Will update again when we have more data.
 
Jamie, that's a beautiful airplane! I see your problem, though. You have a tie-down ring still in the airplane! That's got to account for 10 kts. :p

Seriously, though...great looking airplane. I was in Brisbane a few years ago and visited the small airpark to the West (don't recall the name). Very nice people, and some great looking RV's. I'm embarrassed to say that I don't recall the names of everyone I met! Fantastic group, though.
 
but I would think a leak of some kind would make my instrument read slower, not faster.
Click to expand...

Well that depends on whether the leak is in a positive or negative pressure location, so you could have either. Chances are you just have one heck of a slippery machine.

Jamie still needs to install his gap seals around the wing roots and yes those tie down rings :eek: :D

I was in Brisbane a few years ago and visited the small airpark to the West (don't recall the name).
Click to expand...
You are truly a LOST pilot :D:D

I would guess you were at the Gatton Airpark just outside the farming town of Gatton. Its a great little airpark, and the folk are always welcoming. Most likely Martin Hone who has an RV6 would be one of the folk. He does frequent VAF from time to time.


Nice picture Jamie, I reckon that the Pilot Flying is one heck of a great guy ;) And his 200 series Landcruiser is parked outside the hanger right under the plane :).

The wx looks good right now mate, I think the only performance problems it has is the three fat a$$ed test pilots doing the flying :p

It really is one of the nicest RV7A's around!
 
You are correct! It was Martin. My apologies if he reads this! That was a very enjoyable visit for me. If there were ever a place I could live outside the U.S., it would be Australia. Some of the friendliest people I've ever met, and a beautiful country.

And yes, for the record, if I don't have a GPS, I'm probably going to get lost! ;)
 
Yes, I still need to install the gap seals around the wing roots.
I also need to work out a seal around the nose gear leg, where it goes into the lower cowl. I had to make the slot for the nose gear ( in the lower cowl ) a lot longer so I could get the cowl lower to pass under the 3 blade prop when removing it.

I wonder if we close the air vents while doing the test if it would make any changes.

I just hope the rain clears for this weekend.
 
Jamie Aust said:
Yes, I still need to install the gap seals around the wing roots.
I also need to work out a seal around the nose gear leg, where it goes into the lower cowl. I had to make the slot for the nose gear ( in the lower cowl ) a lot longer so I could get the cowl lower to pass under the 3 blade prop when removing it.

I wonder if we close the air vents while doing the test if it would make any changes.

I just hope the rain clears for this weekend.
Click to expand...

Hi Jamie, I read a post on VAF a couple years ago about how long someone cut the slot for the nosegear leg. I don't recall exactly, but I think it was over 2 inches longer than what's on the plans. Fortunately, the Fairings Etc intersection fairing covers the slot completely.

Someone also posted a couple months ago about open cabin vents slowing the airplane down, so I tested it a few weeks back. I had the airplane trimmed out and cruising along pretty smoothly. I closed the vents and it picked up between 2 and 3 mph. Opened them and it slowed down again. I was surprised by this, but I'll definitely have them closed when I validate my airspeed this weekend! ;)
 
Alright, here's the update...not great news for me, but oh well. :D I did several "calibration runs" using Doug Gray's method. It pretty much zeros out the wind and gives you a "real" TAS. From doing a little research, this TAS is exactly what I get for my actual test conditions. Note that I was not at 8,000 ft. density altitude, but at 7,000. My TAS ended up being 205 mph. Bummer...I was hoping for at least 210!

I have done a couple things that should have slowed the airplane down, as well as a couple that sped it up (since my initial calibration over 2 years ago). I've added prop-guard tape and I'm using auto-fuel...not sure how much the latter would slow me down (if any). For speeding it up I've painted it, and I have taped the intersection fairings.

Next weekend I plan to refly my calibration test using Avgas...we'll see what happens!
 
Whats a few MPH between friends.

My question is how does your accurate TAS from the GPS derived data compare to your TAS by airspeed indicator adjusted for DA/Temp or via a calculated TAS in an EFIS?

This is the thing everyone should be checking, their actual TAS v the "indicated TAS".

Cheers

DB :)
 
RV10inOz said:
Whats a few MPH between friends.

My question is how does your accurate TAS from the GPS derived data compare to your TAS by airspeed indicator adjusted for DA/Temp or via a calculated TAS in an EFIS?

This is the thing everyone should be checking, their actual TAS v the "indicated TAS".

Cheers

DB :)
Click to expand...

Yep, I agree with that! I actually posted on another forum for MGL EFIS owners to discuss this. Apparently, a few of us have varying degrees of accuracy with the IAS. The TAS in my EFIS is calculated based off IAS and density altitude, but the manufacturer always used standard temp for the OAT rather than the "actual" temp! They've fixed that in the latest firmware, which I do not yet have.

Fortunately, for my test runs, my OAT guage was bouncing between 58 and 60! Talk about lucky. So, given those values, the only one that was really not correct was my Indicated airspeed, which I now realize I have to calibrate.
 
We tested Jamies machine after a highly technical modification :D and bingo....no idea how apart from the fact I have become a good guess, but we nailed it.

We did two runs, one at indicated TAS of 169 and the GPS record was 168.12 knots. :):)

Second run at 145 indicated TAS or EFIS calculated TAS I should say compared to 147, now this run was just a really quick one so may not have been as accurate and stable. It was merely because I could not believe how close the first one was :D
 
Dave and I did some more testing on Sunday.
It was a hot 30 deg C and bumpy day. The trip up was at 8.5K and back was at 5.5K. At 8.5K we got it to run ROP very nice. On the way back we got LOP and smooth, our best lean was 28 ltrs per hour, giving us 5nm to the ltr. remember this is with a Carb, fixed pitch !
Here are some pictures taken with Iphone.

img0632large.jpg


img0631large.jpg


img0630large.jpg


img0629large.jpg


img0628large.jpg
 
WARNING TO ALL LOOKING AT THESE PICS

The ROP in the tacho section is wrong, we were LOP and I managed to confuse it to thinking it was ROP during my fiddling and experimenting.

Note at the bottom in yellow it says LOP, and we were.

Otherwise it was a good run. :)
 
Crunch these numbers please

I have very few hours on the bird but I'm thinking my Catto 3 blade may need more pitch. Yesterday I did a couple Gps boxes until I came up with these numbers. What do you think?

Alt 8000
Oat 46F
Man 22.2 ( anymore more and Rpms shoot past 2700. Lot of throttle travel left)
Fuel flow 12gph ( still not sue if calibration is correct. Things to do)

Indicated. Gps
N. 154. 154
E. 155. 164
S. 156. 194
W. 156. 176
 
Cfrisella said:
I have very few hours on the bird but I'm thinking my Catto 3 blade may need more pitch. Yesterday I did a couple Gps boxes until I came up with these numbers. What do you think?

Alt 8000
Oat 46F
Man 22.2 ( anymore more and Rpms shoot past 2700. Lot of throttle travel left)
Fuel flow 12gph ( still not sue if calibration is correct. Things to do)

Indicated. Gps
N. 154. 154
E. 155. 164
S. 156. 194
W. 156. 176
Click to expand...


Hey Chris, how about some specs? What engine, HP, prop diameter/pitch, etc? Also, are your number in knots, or mph?

If that's mph, then yeah, you're slow and probably needing to be re-pitched. How much past 2700 RPM will it go? It's pretty normal for Craig to pitch them so they turn around 2750 at WOT. If it goes past that, then yes again, you need to repitch it.
 
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Thanks for responding. Engine is an IO-360, 180 HP. The prop is a 66\74. It will hit 2800, maybe a little over, at 8000 ft. My speeds were in Kts.
 
lostpilot28 said:
Hey Chris, how about some specs? What engine, HP, prop diameter/pitch, etc? Also, are your number in knots, or mph?

If that's mph, then yeah, you're slow and probably needing to be re-pitched. How much past 2700 RPM will it go? It's pretty normal for Craig to pitch them so they turn around 4750 at WOT. If it goes past that, then yes again, you need to repitch it.
Click to expand...

Mine won't turn 4750 WOT :eek:
 
Chris, that's pretty much the same setup as mine...only difference is that I'm carbed. At least I *think* my prop is the same as yours. When you ordered your prop from Craig did you tell him you wanted it pitched a little more for Climb? When I ordered mine I told him to give me the best for both. My friend Steve Barger did the same thing...our RPMs pretty much match at WOT. My guess is that you're pitched for a better climb RPM.

Reilly, I caught my mistake after I clicked "Submit". LOL...I wish mine would turn 4750. Wonder what HP that would make (assuming it wouldn't explode into tiny pieces).
 
Yeah. Not knowing anything at the time, I asked for something in between climb and cruise. I think my prop may favor climb though.
 
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