Are Van's numbers bogus?

I'm still studying the RV-4 market in depth. This site is huge for information! That's a big help. So, I'm hoping to tap into the wealth of experience here.

Van's website under specifications says 905-913 lbs for an empty weight. I haven't seen many like that. Make that ANY like that.

Flip to performance, 193 mph cruise for a 160 hp, 75% power @ 8000 feet? 201 for 180 hp? Is a 200 mph cruise realistic?

"Top speed" over Vne with a wood fixed pitch prop?

Rate of climb at gross 1,650 (160 hp) - 1,950 (180 hp)? 2,050 - 2,450 solo?

Is this with the same wood FP prop as the 204-213 mph top speed?

I've read posts where the Catto added 15 mph, etc. over a different prop.

What are the real numbers, verifiable, repeatable numbers that can be honestly expected from an RV-4?

I've read and heard that Van doesn't exaggerate his numbers as other experimental manufacturers do. I'm hoping that's the case. If you guys would share your true real world numbers here with engine/prop configurations, I'd be very interested to see them and compare. I want those numbers on Van's site to be true.

Thanks --


George

Here are my numbers...

Empty wgt: 1053lbs
Engine: 180hp was LASAR, now dual PMags
Prop: Hartzell constant speed
Speed: 175kts @7500 feet, 24" manifold (all I can get), 2400 rpm
Fuel flow: 9.4 gal/hr - running 25-40 degrees ROP
Rate of climb: 2000+ FPM solo, half fuel on a cool, dry day
With full fuel and a passenger on a hot humid day, much less - 1400-1500 fpm
My new blended airfoil prop does not seem to climb as well as my old Hartzell CS. I don't have any good data for this seemingly minor delta.

I believe all Van's numbers are accurate. Hitting the advertised weight requires a simple machine, little to no paint, and few instruments.

Regards,

Dean Pichon
Bolton, MA

If you want Van's numbers you have to build like Van. Most of us build heavier, adding creature comforts and such. Very few stick to Van's "keep it simple" philosophy. Regardless, there are some RV racers out there, so attention to detail can make for a fast plane.

One data point; the RV4 I built and flew for almost 8 years. It was VERY clean, fairly light, tightly baffled, and had no trouble keeping up with most 4's I flew with:

200HP (dyno tested)
FP Amar Demuth prop 78/86
1025 empty

I usually ran 65% or so at 11500-12500 MSL, LOP. This does not compare directly with the claims you related above. But, at 2550 rpm, and 12000MSL or so I routinely got 165 knots TAS with fuel burn in the low 7's.

The airplane was capable of hitting V_ne in level flight at lower altitudes, like 3000 MSL. I never "cruised" near 200 mph though due to the fuel burn, high power required.

You should be aware that gross weight has little effect on level flight performance, due to the extremely low wing loading. The 4 would turn in the same cruise numbers solo or dual, it didn't really matter. Higher weights affected climb performance much more directly. So, "building like Van"; ie keeping it light (maybe 100 lbs less than average) would have an almost immeasurable effect on cruise speed.

Well Dean and Bill, those are both respectable numbers, pretty close to the ones Van's stie has posted, but with 180 and 200 hp instead of 160, and both with CS props. At least with more power the numbers are attainable, though.

Anybody have 150/160 hp CS and FP numbers?

Bill, you mentioned the plane being "clean" and having more speed in it. What did you mean with that?

Thanks guys


George

Welcome, George...

...Clean in this business means internal antennae, good fitting cowling and tight baffles, very little to no protrusions that create drag. Also tight fitting upper and lower intersection fairings on the landing gear and attached with flush fitting countersunk screws to minimize drag.

We only have our com antenna outside to that end...the VOR and marker beacon antennae are in the tips.

Some guys make fairings for the fuel drains under the wing and also fair the aileron hinges, among other drag reducing things.

A California dentist (Dave Anders) has a -4 that broke the CAFE records at 265 MPH straight and level! This on very carefully calibrated test equipment.
Blew John Harmon's (Harmon Rocket) record by a big margin.

Visit the CAFE site and read the story.

Regards,

Thanks Pierre -

I think Smokey posted the story of how the good doctor pushed his way into the CAFE race. Do you know what his most significant mods were? Obviously as the world record holder, his airplane isn't typical. Why don't we see "Anders style" RV-4's everywhere with performance like that?

I've read lots of your posts, so you're obviously actively involved in the RV community. What do you think are typical 160 hp RV-4 numbers?

Thanks again --


George

Standard RV4 160hp

Hi George
My -4 is about as close to the standard as they come. Delta Mike weighs 948lbs ready to fly. The Lycoming O320 E2D is making 160hp. On a trip to Corvallis from Carson City @8500' I made 172kts TAS there and back, Fuel burn was 9.4gph at 2700 RPM. Climb rate performance changes with the density altitude around here. In the Summer DA is around 6500? to 8500? @ 1450 lbs I see 1200-1400fpm. In the winter DA 2500-4500 @ 1450wt I see1700-1900fpm. At Corvallis in the morning by my self with the weigh around 1300 lbs the climb rate was over 2000fpm. Your mileage may very

George, you need a ride

I'm not sure why you're having a hard time believing Van's numbers. Maybe you need a ride in an RV. Those numbers and the ease of achieving them are the whole reason people are so wild for the design.

The RV4 numbers you quote are almost identical to the RV6 numbers, and I can verify that my RV6A was within a couple MPH of the Vans numbers. I had a 160hp with a Hartzel and even with my heavy 1120 empty weight, my 75% cruise was 195 mph TAS at 8000 ft, top speed at 2000 ft indicated was 201 mph, and I routinely climbed out at better than 1600 fpm dual and 2300 fpm solo.

The RV4 performs even better, with it's lighter weight, smaller cross-section and one less gear leg hanging in the wind, so I have no trouble believing that those posted numbers could be achieved with a properly designed wood prop.

You're right about the weight, though. It's tough to make yourself build as light as Van's does, but some people do, particularly with the 4's. My experience, though, was that the airframe is so slippery that weight didn't make that much difference anyway. I still made the Van's numbers.

Thanks Dayton - which prop? And do you think your plane is pretty typical of 4's? I asked the guy who has the first one listed in Barnstormers, very light at 864 lbs or something like that. He said he's got a climb prop and "cruises at 160 mph". Not much detail there, but that's a small number. I like yours much better.

Thanks Jon, you're right, I need to bum a ride. The only one I've had was in the demo 7 and it fell short of the speed and stalled higher, but that was unverified indicated speed.

I talked to Rob Reid, named on this site a few times, and the numbers he threw around were lower than published. He's flown 50 million different kinds of planes though, and admitted he didn't know precise numbers for all and didn't know what typical 4's weigh in at.

So I'm just seeking reassurance that there really is a Santa Claus until I can actually fly and verify numbers for myself. The two 180 hp responses are right on, but for the 160 hp figures. Daytons 160 hp numbers, however, are in there. I hope his is the norm.

Glad to hear your 6 came in as advertised, or within tolerance.


George

George, I put 1500 hours on a stock 1991 RV-4 with a stock 160 hp with a CS prop. There was nothing special with the plane. At 8000 ft. at 2600 rpm it would cruise at 191 mph, however I always used lower rpm for less fuel burn, more quiet, and less vibration. Typically I cruised at 180+ at 7 gph and very happy with it.

Steve Barnes The Builders Coach

pierre smith said:

A California dentist (Dave Anders) has a -4 that broke the CAFE records at 265 MPH straight and level! This on very carefully calibrated test equipment. Blew John Harmon's (Harmon Rocket) record by a big margin.

Click to expand...

Hey, that's a great read, Pierre. Thanks!

RV-4: New CAFE Triaviathon Champion
http://cafefoundation.org/v2/pdf_apr/RV-4.pdf

CuriousGeorge said:

Well Dean and Bill, those are both respectable numbers, pretty close to the ones Van's stie has posted, but with 180 and 200 hp instead of 160, and both with CS props. At least with more power the numbers are attainable, though.

Anybody have 150/160 hp CS and FP numbers?

Bill, you mentioned the plane being "clean" and having more speed in it. What did you mean with that?

Click to expand...

George,

Yes my airplane was clean by any reasonable standard. I built it very tight: all fairings were hand-laid and fit like they'd hold water. All exterior screws were flush, and it only had a COMM antenna on the belly.

More importantly than the little parasite items, the plane was baffled really tightly and had nice clean, tight fairings everywhere.

Still, I know there was more speed to be had by way of a couple upgrades I would have done had I kept the plane: replace the 1st gen wheel pants with the new pressure recovery type (worth apprx 5 mph) and upgrade to a new hi-temp epoxy cowl (lose 10 pounds); add inlet diffusers and possibly a cowl exit afterbody (another 5 mph at least).

One small correction to your observation: my 4 had a fixed pitch prop, not CS.

TAS not IAS

CuriousGeorge said:

Thanks Jon, you're right, I need to bum a ride. The only one I've had was in the demo 7 and it fell short of the speed and stalled higher, but that was unverified indicated speed.

Click to expand...

Be careful of judging by indicated speed. The Van's cruise numbers are TRUE airspeed at 8000 ft. If you were cruising in the factory demonstrator at 8000' and saw 165 mph on the ASI, you were traveling at 191.4 mph TAS. Here's a calculator: http://www.csgnetwork.com/e6bcalc.html

The top speed number is also True Airspeed, but it's done at a lower level where you can get full power and the IAS is closer to TAS. My top speed number was actually measured by flying a three-leg course on the GPS, so technically it was ground speed rather than IAS or TAS.

I would be shocked if the Van's RV7 demonstrator didn't stall exactly at the advertised speed. The stall speeds for the various RV's are very predictable and generally if a particular plane doesn't stall at the advertised number, it's due to pitot/static error. (My plane indicated 5 mph lower than standard at high angles of attack because I was using a Piper pitot mast instead of the standard static ports.) But obviously, the demonstrator has a standard pitot/static system, so if you say it stalled at a higher number, I'm a skeptic. I've never flown that plane, but I did fly the 9A demostrator once and I can tell you it was dead on.

RV-4

My -4 weighed in at 945 no gyros, painted, built to the plans

160 hp lyc. 0320 Sensenich FP metal prop 81 pitch

At 2600 rpm just about any alt. ( below 10,000msl) 165kts TAS

at 9500 leaned out 164 ktas 7.3 gph

Catto 2 blade, 76 pitch modified cord 2850rpm 180kt tas at 8000 den alt.

Chris M.

Where does the weight come from?

After considering all the stuff we put in our planes, it's no wonder mine is about 100 pounds heavy (1055lbs). Off the top of my head, I was able to generate this list of "goodies" probably not included in Van's original design:

• CS prop
• 20 "extra" HP (180HP)
• fuel injection/purge valve/fuel filter/fuel totalizer/fuel bypass plumbing
• Cockpit heat
• Oil filter
• Vacuum pump
• Prop governor
• Oil cooler louvers and cockpit control
• Epoxy primer on each and every part (prior to assembly)
• Clear coat over 2 base colors
• Full gyros
• Transponder
• Strobe, position, and dual landing lights
• Rudder w/0.020 skin
• Two axis electric trim
• Electric flaps

The only item that "saved" weight was the epoxy/honeycomb cowl

I may weigh it again. 1055 seems light...

Regards,

CuriousGeorge said:

Thanks Dayton - which prop? And do you think your plane is pretty typical of 4's? I asked the guy who has the first one listed in Barnstormers, very light at 864 lbs or something like that. He said he's got a climb prop and "cruises at 160 mph". Not much detail there, but that's a small number. I like yours much better.

Click to expand...

Unfortunately, "Climb prop and cruises at 160 mph" isn't enough information to properly evaluate. Is that IAS, TAS, CAS, and at what altitude and power setting? To accurately determine power setting, we need manifold pressure, density altitude, and RPM information.

For what it is worth, I know plenty of RV guys who cruise at 170-180 mph TAS, but that is typically at 60 or 65%. That's describes how I fly, but if I flew at 75%, my airplane's cruise would be ~190 mph.

CuriousGeorge said:

I'm still studying the RV-4 market in depth. This site is huge for information! That's a big help. So, I'm hoping to tap into the wealth of experience here.

Van's website under specifications says 905-913 lbs for an empty weight. I haven't seen many like that. Make that ANY like that.

Flip to performance, 193 mph cruise for a 160 hp, 75% power @ 8000 feet? 201 for 180 hp? Is a 200 mph cruise realistic?

"Top speed" over Vne with a wood fixed pitch prop?

Rate of climb at gross 1,650 (160 hp) - 1,950 (180 hp)? 2,050 - 2,450 solo?

Is this with the same wood FP prop as the 204-213 mph top speed?

I've read posts where the Catto added 15 mph, etc. over a different prop.

What are the real numbers, verifiable, repeatable numbers that can be honestly expected from an RV-4?

I've read and heard that Van doesn't exaggerate his numbers as other experimental manufacturers do. I'm hoping that's the case. If you guys would share your true real world numbers here with engine/prop configurations, I'd be very interested to see them and compare. I want those numbers on Van's site to be true.

Click to expand...

Not many builders match the empty weights of the Van's prototypes, because most builders install extra stuff that Van does not consider as necessary. You should be able to match Van's weights if you use the Burt Rutan approach to choosing stuff to install - "if you throw it up in the air, and it comes back down, then it is too heavy to install in your aircraft". Every ounce counts, and those ounces add up. The other way that some builders achieve low empty weights is to use uncalibrated scales.

If you want to get an idea of the credibility of Van's claimed performance numbers, compare the performance that the CAFE Foundation measured on RV-6A, RV-8A and RV-9A against Van's claimed numbers. You will find that the CAFE results generally matched or exceeded Van's claims on these models. E.g. - 180 hp RV-6A - CAFE Foundation found max speed at 7000 ft of 200 mph. Van claims 75% power speed of 198 mph at 8000 ft. Van almost certain has assumed that full throttle at 8000 ft = 75% power. But, note that achieving this speed requires running at high rpm - many builders are not comfortable cruising at such a high rpm, so they cruise at slower speeds. CAFE Foundation found full flap stall speed of 52 mph, Van claims 55 mph. Etc.

The CAFE Foundation never tested a "stock" RV-4, but there is every reason to believe that Van's claimed RV-4 performance is just as credible as his claimns on other models. Of course you need to build a straight, clean aircraft, have a good engine, and install a good prop if you hope to meet Van's claimed numbers.

I have roughly 500hrs on my IO-360 RV4 with CS prop (bought). Other than engine and prop stock standard. 1050lbs. Weight makes little difference, although when you have overkill HP, but am sure the 135hp -4 will suffer at 1100lbs for eg....

I use it as high speed commuter so fly at 75% power most days. Difference in my case between 2500rpm and 2700rpm is maybe 2-3kts, but that may be in accurate instruments. Fuel burn increases significantly over 2500rpm for little return in kts...

Flown in plenty air races where balls to the wall is the order of the day. We have GPS loggers which track and log speed alt etc every second. So data is relatively good. 75% is about all you get since all the races are at Alt (4000-5500ft ground level). Mine averaged over the 650nm 2 day course in 2008 in light wind conditions just over 175kts. That from standing start each day and flying skew "chasing" a Seneca on day 1 thus causing some extra miles which cost maybe a kt or 2 on the avg speed.

Average speed over the maybe 8 or so races (most are between 100 and 200nm) seems to be around 172kts, but WX conditions affected that and shorter races' speeds are lower due to number of turns, standing start and less air time.

Cruise speeds at 9gal/hr at 2500rpm and 21-23" (max I get at alt) are around 170kts TAS at 8000ft, although 175+ is not uncommon. I can get close to indicated VNE straight and level and climb performance is way better than stated.

I have flown in back of 160hp O-320 RV with wood prop (don't know pitch but was cruise prop), but we got close to 160kts at full tilt at 8000ft.

I fly formo with a fastback with a 0-360 with 3 blade MT prop. I don't know if he stroking my ego, but he can not keep up at balls to the wall... His is lighter and has all the newer fairings, but is maybe 2-3kts slower? No idea why.... Weights are similar - his slightly lighter with the new MT vs the old Hartzel.

My RV6 with O-320 and CS prop is on the numbers or marginally better, but it still new to me (<10hrs waiting for local FAA to finish paperwork - 2 months now) and I have not even started playing properly yet.

Have flown the 7, 7A, 9A & 10 in said race conditions and all speeds are better than claimed by Vans at 8000 alt for those specific models. Interestingly the 10 (2) were within .02 of a kt avg speed over the whole race. 1 has 2 blader other has 3 blader and is slightly lighter... Avg speed was just over 180kts, can't remember exact figures, but the wind was huge and helped... In windless conditions we "tested" them at around 176kts TAS.

I would honestly say that Vans speed numbers are conservative (bordering on overly conservative) and that you should easily match them with avg build RV/eng/prop combination..., but take that with a pinch of salt. I have HUGE RV bias.... I bought the -4 without ever even having seen a real live RV and the 6 sight unseen, based on recommendation from a mate of mine 6000miles away. That my blind faith in the Vans product. Was not disappointed by either and will build my own as soon as time allows.... in mean time I am enjoying drilling fast (Bonanza, 210 type speeds) holes in sky on cub budget.

Not all RV's are created eaqual, but it is tough to botch the job IMHO, especially if the airframe, engine and prop combination have a couple 100hrs "experience"....

My advise would be to shedule said test flight, BUT clear it with bank manager or Deputy director of finance(Wife) BEFORE you go fly in the -4 and when you go fly the -4 take your chq book along... It will be an expensive ride, but grin will need to be surgically removed.... ENJOY.....

Thanks everyone

Well, this was a good response so I don't feel like I'm chasing unicorns. As I said in the beginning, my experience is very limited. If there's a 4 owner in S. FL or Maine (my summer hangout) who would like some back seat ballast, I'd love to see it all first hand.

The only ride I have had was a 15 minute demo ride at Sun 'n Fun a few years back in a 7. That alone was sufficient to install the famous RV grin on my face, and for a long time I thought the 7 would be it for me. But, having read more about the 4's handling, plus the fact that I know I'll be solo 90% of the time, plus it reminds me of my Navy flying days sitting in tandem, plus for whatever reason the prices are much lower on the 4, all that comes together to make the RV-4 my target.

Anyway, I vaguely remember the numbers coming up short, but there wasn't enough time to verify them. Then with other things I'd read, I became concerned. So thanks to all for the reassurance that the performance I'm hoping for will be there.

As a final question for Bill Wrightman, why did you give up such a good airplane? I see the RV-8 under your name. Did you eat too much airline food in your 777?


George

George,

The 4 was sold to help capitalize my new business, Intelligent Design Group and to fund development / production costs for putting The Terminal Tool on the market. That's right - I sold a beautiful sport plane to fund a wiring tool!

Now that the tool is finished, patented, and selling, I have an 8 in the shop. I just wanted to build again; I'm a builder at heart.

Airline "food"?

HA! Well yeah I've probably indulged in one too many Ben & Jerries hot fudge sundaes, chocolate boxes, Starbucks coffees, Cokes, and countless pieces of cheese cake at UAL. Ooommmph.... then comes the layover, with all its (mostly liquid) indulgences. Oh God, did I want to admit all that here?

edit: you must be an airline toad like me to ask such an insightful question

Ribbit

Hey Bill -

737 Int'l out of MIA - you can guess the airline. 20 years, if you can believe it. I've always flown the Caribbean and Latin America so I missed out on the once delicious European munchies. But I have seen their effects ; )

It's good we have fun hobbies... ever get on a long final at 170 KIAS and think "Hmmm, this is RV cruise speed!"?

It's good that at least one UA guy found a good way to market his tool... har har


--George

P.S. Thanks again for your helpful posts.

My -4 had a 180 HP O360 with a Hartzell C/S prop. It was heavy (1080 lbs), but consistently trued out at 170 knots at 8000 - 10000 feet. That was WOT, and 2500 RPM. Fuel flow was at 10 gph.

I took it to 17,500 once, and it was still climbing 400 fpm. I cant remember the TAS at that altitude, but it dropped off less than I thought.

It exceeded all of Vans numbers, but I think theirs was measured with a fixed-pitch wood prop.

RV4 performance

My 4, orginally had a wooden FP prop. 915lbs 180hp with inverted oil, so that added some weight. We hit vne S&L and climbed as advertised. Now it has a metal FP prop, it does not perform quite as well but is a lot more efficient.