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RV-3: Interim Phase 1 Report

Ironflight

VAF Moderator / Line Boy
Mentor
Well, we are just a month past first flight, and two of these weeks we were out of town. We?ve had a couple of ?No Fly? days due to weather, but we now have 33 hours on the airframe, and I can share a few test results.

We?ve expanded the speed envelope from a flaps-down stall of 50 knots IAS to the redline of 183. We did a few limited TAS excursions (a couple of knots) above that in a smooth-air descent, but will stick with the design redline ? I have no desire to test the flutter limits beyond Van?s engineering. Stalls are normal for an RV ? power off, it breaks sharply, but honestly, and recovers instantly when you release back pressure. Holding it in an incipient stall with power on gives a fair amount of tail ?rattle? (it?s a metal airplane), but I found nothing loose or damaged afterwards ? it?s just a little noisy.

One turn spins left and right were quick, but normal, with a steep entry. We?ll explore spins more in future tests. I don?t think this will be a favorite spinning airplane ? it loses altitude pretty quick. I?ll go get a Cub for lazy spins?.

Max G?s demonstrated have been 4.8?..if I?m going any higher than that, I?ll have to wear squeeze pants?.

Best rate of climb airspeed appears to be between 95 and 100 knots IAS at sea level. A timed climb at 125 TAS from 3,000 to 12,000 took 6:30, for an average ROC of 1384 fpm. That was a ?Cruise climb to keep CHT?s below 400. Max ROC we?ve seen steady state (after the zoom) down low is in excess of 3,000 fpm between 2,000? and 3,000? (msl). Speaking of cooling, it IS winter, but the oil temp hasn't gone above 180, even in extended slow flight. CHT's are limiting for climb after awhile - but do just fine at a 1,500 fpm cruise-climb at 120 KTAS.

I took the airplane up to 17,500? today where it was still climbing at 500 fpm at cruise-climb of 120 KTAS. I leveled off (no IFR in Phase 1) and let the airplane stabilize at full throttle (leaned to peak) and 2500 rpm. The EFIS showed this as 50% power, with a fuel flow of 5.7 gph. This gave a TRUE airspeed of 165 knots. There was 35 knots of wind up there, and when I pointed the nose downwind, that gave a groundspeed of 200 knots, with a mileage of?.yeah, it was ridiculous!).

Coming down from altitude requires a considerable throttle-back, or you?re over the TAS redline pretty quick.

CG has been tested to the aft limit, and right on the line, pitch stability is neutral and undamped ? yet the airplane is easier to land in that condition than an aft-loaded RV-8. With normal loading, it is positively perfect at all speeds and conditions.

Louise has been busy with cruise performance testing, and is reducing the data when she has the chance. I haven?t tried a flat-out max speed run at full throttle on the deck, but based on what I have seen, I expect it to be about 183 knots ? redline.

Aerobatics ? I?ve done all the rolls (except snaps), loops, Cubans, Immelmans, cloverleafs, Split S?s?well, pretty much all of the stuff I would expect this sport acro machine to do. It?s really got the power to do vertical rolls and it?s so nice having the Half-Raven system to keep from spewing oil all over the belly.

I?ve done a fair amount of avionics testing to make sue the major stuff works. After squashing a few bugs here and there, everything seems to work ? G430 is great for GPS, VOR, and ILS work ? approaches are great ? coupled or uncoupled. The GxPilot is doing great, and plays very well with the G3X ? which is also outstanding. I?m still working through all of the A/P modes, but it is pretty cool to give it a crossing altitude at a fix and a desired rate of descent ? then watch it start down at the right time. We?ve done one cross-country to College Station (in our test area) to see how it is in cruise ? and it?s great! It?s pretty easy to get it dialed in for 70% power and 7 gph at a few thousand feet ? that?s a nice four hours to dry tanks.

On the maintenance side, we?ve had one instance of cracking on the little extension of the right lower flap skin that ?underlaps? the fuselage. The flap skin is pretty thin, and I expect that the unsupported piece is flexing in the breeze when deployed. I?ll probably add a doubler before it goes to paint. We added a small rudder trim wedge until I engineer and install an active trim tab (or don?t?..). the right brake seems to be evaporating brake fluid?.have had to pump it up once in 33 hours, but can?t find any sign of the fluid going anywhere. Little stuff ? nothing major.

So onto finishing up Phase 1?then we?ll be free to explore a bit more ? need to take it on a trip to the paint shop to get Grady looking at ideas for us?. 
 
Paul, thanks for the report--------

I have to second what someone said in one of your prior posts, Vans needs to give you and Louise a commission on the RV 3's that are going to be sold here is the near future.

Wonder if I would fit in one????
 
I have to second what someone said in one of your prior posts, Vans needs to give you and Louise a commission on the RV 3's that are going to be sold here is the near future.

I asked a spy at the factory if there has been an increase in orders....the answer was not encouraging from a commision standpoint.....:rolleyes:

Wonder if I would fit in one????

I take the fifith on that one....:p
 
The RV-3 has zero static margin at aft cg?


I was just re-doing the W&B for the test, and we were just a little behind it for that data point. The good thing is, that was pretty heavily loaded in the baggage area - well beyond what we plan to placard it.

It was actually positive at 100 knots, but pretty much zero at 145. It's easier to land at full aft than the -8, probably becasue there is margin at the slower speeds.
 
On the maintenance side, we’ve had one instance of cracking on the little extension of the right lower flap skin that “underlaps” the fuselage. The flap skin is pretty thin, and I expect that the unsupported piece is flexing in the breeze when deployed. I’ll probably add a doubler before it goes to paint.

No need to do this immediately, but when you get a chance, will you please think about and share any ideas you might have for design changes to prevent this cracking which can be implemented at build time? I assume at the least that putting a doubler inside the flap at that point would look a little better.

You can add this to the long list of improvements you and the others have already shared. (It's interesting that the early -3 builders must have made such discoveries too, but until Randy, Rob, you guys, and a few others started documenting these tweaks on the web, there was no way to disperse these pearls into the collected memory for future builders.)

I asked a spy at the factory if there has been an increase in orders....the answer was not encouraging from a commision standpoint

Maybe not . . . yet!

It takes a certain courage to start a -3. Give it a little time and I bet there's a noticeable uptick.

--
Stephen
 
TAS Limits?

Paul, just reading about how you had to throttle back to keep from exceeding the TAS limit on your RV-3 - I'm guessing that you get a TAS display on your G3X?

I'm aware that we have both IAS and TAS limits on our RVs, the IAS being the structural limit and the TAS being the flutter limit. I know the IAS limit on my RV-6 - it's 210 MPH IAS. My question, for you or anyone else who knows: where do we find the TAS (flutter) limit for our RVs? Specifically, for a -6. Is it the same number, 210 MPH, except TAS vice IAS?

I've always observed the IAS limit on my -6, but until your post reminded me, I've been kind of ignorant of its TAS limit. Maybe because I have steam guages with no TAS display...
 
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Hi Ross...

If you read the Builders' Manual carefully, in the Flt Test section, you'll see in the ASI markings table the VNE referred to as TAS i.e. there is no defined IAS limit.

For practical purposes, observe it as IAS at lower levels. Higher up, knock off a suitable amount ;)
 
Paul, just reading about how you had to throttle back to keep from exceeding the TAS limit on your RV-3 - I'm guessing that you get a TAS display on your G3X?

I'm aware that we have both IAS and TAS limits on our RVs, the IAS being the structural limit and the TAS being the flutter limit. I know the IAS limit on my RV-6 - it's 210 MPH IAS. My question, for you or anyone else who knows: where do we find the TAS (flutter) limit for our RVs? Specifically, for a -6. Is it the same number, 210 MPH, except TAS vice IAS?

I've always observed the IAS limit on my -6, but until your post reminded me, I've been kind of ignorant of its TAS limit. Maybe because I have steam guages with no TAS display...

Kind of like Andy said Scorch - I am sort of extrapolating from what I have learned about the Flutter limit in Van's writings in general. I am basically assuming that the IAS Vne quoted at seal level is the TAS Vne to which the airplane has been tested - that is possibly conservative, but in the absence of data, and with the potential for catastrophic damage when talking about flutter, I'd rather be conservative.

And the EFIS really makes this pretty easy - not only does the G3X show TAS all the time in a little box, you can set the red line on the ASI tape to show where the current (calculated) TAS is relative to IAS. (I know that's a ridiculous sentence....basically, the red line is always at the place you shouldn't exceed RIGHT NOW). It's basically like the barberpole needle on a a turbine airplane's ASI. Time to get Danny to start installing an EFIS Ross! ;)

Paul
 
And the EFIS really makes this pretty easy - not only does the G3X show TAS all the time in a little box, you can set the red line on the ASI tape to show where the current (calculated) TAS is relative to IAS. (I know that's a ridiculous sentence....basically, the red line is always at the place you shouldn't exceed RIGHT NOW). It's basically like the barberpole needle on a a turbine airplane's ASI.

It is indeed a little tricky to describe! But there are a couple of pretty good pictures and descriptions of how this works, on page 63 of the G3X Pilot's Guide and under section 7.3.3 in the G3X Install Manual (pages 7-7 and 7-8).

mcb
 
Well, now I AM confused!

So what you guys are saying is, the 210 MPH "redline" for my RV-6 is, and has always been, a TAS restriction, not an IAS restriction, even though it is physically marked on the Airspeed Indicator, which is basically an IAS guage.

So how many of us stone-age steam guage drivers have been blissfully driving around thinking that as long as we kept the needle below the red line we were OK?

And, just to further muddy the waters: Andy, since Vans publishes only a TAS restriction, and not an IAS restriction, does this mean that in our RVs flutter is always more limiting than structural?
 
So how many of us stone-age steam guage drivers have been blissfully driving around thinking that as long as we kept the needle below the red line we were OK?

Lots.....;)

But seriously, this has been discussed quite a few times here, and Van has written about it numerous times in the old RVator. The problem, of course, is that you as a pilot have no obligation whatsoever to read any of that stuff, so how would you know?

I think part of this stems back to the fact that we are pretty much all putting on more horsepower than Van originally used in his designs, so we routinely operate closer to the upper end than was originally thought about. With more margin to the limit, it was not a big deal. Now we're all speed demons, and have to be careful - especially in descents from on high...

Paul
 
The preliminary performance data

Louise has been busy with cruise performance testing, and is reducing the data when she has the chance. I haven’t tried a flat-out max speed run at full throttle on the deck, but based on what I have seen, I expect it to be about 183 knots – redline.

Okay, here are the performance data based on one run at each combination of power setting and elevation . The scientist in me doesn't like to "publish" such preliminary data but Paul thought some of you might be interested in what we are finding. After a little experimenting with the Garmin G3X lean function, we decided to just go with the Lycoming graph for "peak" at a given elevation. So, I leveled out at a fixed elevation, running "rich", and settled at 2400 rpm. I then pulled the mixture back to 75% power (or whatever was the highest available power setting), adjusted the trim to stablize, then put the autopilot in control. Next, the mixture pulled back to the fuel flow recommended for peak by Lycoming for the IO-320: 75%- 8.7gph; 70% - 8.1; 65% - 7.6; 60% - 7.0; 55% - 6.4; 50% - 5.9. Once the fuel flow stabilized, I recorded the TAS (and IAS). (Other data, like OATs, were recorded but haven't yet been factored in.) I then repeated the procedure at each power setting. Here's what the TAS data (in knots and feet of elevation) look like:

Cruise%252520Performance.JPG


Please remember that I'm a neophyte test pilot and be kind in your comments. :eek:

I haven’t tried a flat-out max speed run at full throttle on the deck, but based on what I have seen, I expect it to be about 183 knots – redline.

Paul might be able to shed more light on this topic now. Paul?
 
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Louise,

You may not be a test pilot but the scientist in you is showing through very well.:D There's nothing like data to sort out facts from fiction, opinions, and misrepresentations (intentional and unintentional).

While I understand these data are preliminary, the consistency of the slope and the trend toward higher speed with altitude suggest the numbers probably are not far off. I'm, surprised more people don't do this exercise and post the results. This is exactly what I'm looking forward to doing with my RV-9A with the IO-340.

And if I did the calculations right, at 14,000 feet and 50% power, your getting a shade better than 31 mpg. That's really impressive considering your going 163 knots TAS.
 
Paul might be able to shed more light on this topic now. Paul?

Yes...ahem....I did a 1,000' speed run yesterday becasue the ceilings kept me from doing anything up high. Throttle, Prop and Mixture full forward, level at 1,000' msl (near STP) gave me 191 KTAS. We have established that the pitot/static error is +/- 2 knots, so I'd put the same error band on that number.

That's 7 knots over airframe redline BTW - for those thinking of an O-360 on one of these, I'd suggest a tail re-design (for balanced surfaces...).:cool:

Paul
 
Yes...ahem....I did a 1,000' speed run yesterday becasue the ceilings kept me from doing anything up high. Throttle, Prop and Mixture full forward, level at 1,000' msl (near STP) gave me 191 KTAS. We have established that the pitot/static error is +/- 2 knots, so I'd put the same error band on that number.

That's 7 knots over airframe redline BTW - for those thinking of an O-360 on one of these, I'd suggest a tail re-design (for balanced surfaces...).:cool:

Paul
Paul, I remember that doing the same sort of test I could see 222 mph IAS, though I leaned just a bit to get max speed. Very close. In fact all your numbers are very close, of course not surprising.

Yep, an O-360 is totally uncessary and would be heavier and therefore less desirable. Now an IO-340 that wouldn't add any weight..... ;-)

Wait till you fly with your other RV buddies, no one can climb with you as it is, not even close.
 
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