turbo

turbo

Well Known Member
This should be an interesting post. Do you know how fast your plane will go? Some have tweeked your machine to the nines. OH YA. I have seen them and they are very impressive. Mine Is very 'untweeked'. How fast did it go? It is a 1999 6A O-360 FP Sensi 85"P with Mags. At SNF years ago when they did the timed races i turned 208 mph 2,850 rpms WOT on the deck. What a blast. Glad i did it. Have not done it since. Give it a try, if you dare. Might want to turn off the ALT. Have fun.
 
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my numbers

7A w/ IO-360, lightspeed and airflow performance. Got a TAS of 219 mph at about 1800'. Balls to the wall.

Not sure what HP my engine is. It is the 180 hp model w/ 8.5 - 1 pistons so I would assume 180 HP. People tell me that fuel injection can add to that.
 
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Curious

Is there a known relationship between top speed at very low density altitudes vs best speed at, for example, 8000' density altitude?

I would expect there to be many differences in prop performance, engine performance, airframe drag. I just wonder if those differences are consistent between RV's?

Anyone know?
 
hevansrv7a said:
Is there a known relationship between top speed at very low density altitudes vs best speed at, for example, 8000' density altitude?...
Click to expand...
Top speed occurs at the lowest possible density altitude with normally aspirated airplanes. It doesn't matter what the airplane is.
 
hevansrv7a said:
Is there a known relationship between top speed at very low density altitudes vs best speed at, for example, 8000' density altitude?

I would expect there to be many differences in prop performance, engine performance, airframe drag. I just wonder if those differences are consistent between RV's?

Anyone know?
Click to expand...

See this thread (post #5)
http://www.vansairforce.com/community/showthread.php?t=46791

The slope of the curve looks like 2.2 kts increase in TAS for every 1000 ft increase in density altitude (for my RV-6a, IO-360-B2B with Sensenich 72FM8S9-1-85)
 
Hmmmmm. Something must be wrong with mine. My 9A, O-320, three blade Catto will do 192 mph TAS at 8000' DA, a little faster higher, but I won't quote that as I don't have really sound, repeated numbers. I can't get it that fast on the deck, only mid to high 180s! I have been told it is because the E-Mags increase the timing at altitude. I only know the numbers, not the reasons.

Bob Kelly
 
I did 184 knots coming into Osh this year. Never went that fast before and has never gone that fast again. Divine interventation wanted me to make it to Osh that day.
 
RV9A
All kinds of antenni hanging out i.e. 2 coms, 1 ELT, 1 Garmin GPS, StrikeFinder,VOR, Transponder, Glideslope.
IO-360 180hp, 3 blade MT constant speed.
Returning from Oshkosh at 9500', WOT, 2400 rpm
193 mph true @ 8gph
I'm happy !!
Jack
 
RV-6A, O-360-A1A, 72" Hrtzl C/S w F7666 ...

My airplane is a modified RV-6A, with a stock O-360-A1A engine, and a 72" Hartzell C/S with F7666 blades (non-blended airfoil), external antennas (2 com, nav, GPS, transponder). My testing is all done at 6,000 ft density altitude, 3-way passes (360,120,240), 5 consecutive 20 sec. interval readings with no more than 1 kt difference across all readings, WOT, max rpm (2720-2730), leaned for best speed, the average of the 5 speed recordings and GPS track angles input into the appropriate cells of the NTPS spread sheet. With the last mods my speed is up to 184.4 kts or 212.2 mph. I'm not happy yet.

At the first 2-way speed dash time trials at Courtland, Alabama my speed was a little over 220 mph (191.174 kts)

The text and full set of results copied from TVAR Results at www.sportairrace.org are shown below:

The Speed Dash was a timed run over 1-mile of runway. Contestants had to limit their pattern altitude to 1,000' AGL [Courtland elevation is 588 ft MSL] and had to fly down the runway between 500' and 200' AGL. A run was made in each direction in an attempt to negate the wind, and the average speed of the two runs:


Race # Name Aircraft Average Speed (MPH)
Race 28 Jeff Ludwig Glasair III 277.059
Race 109 Tom Martin EVO Rocket 253.390
Race 14 Wayne Hadath F1 Rocket 251.349
Race 58 Mark Frederick EVO Rocket 246.303
Race 30 Marvin Guthrie Bonanza 225.805
Race 71 Bob Axsom RV-6A 220.017
Race 26 Mike Thompson RV-6 215.401
Race 83 David Adams LongEZ 206.249
Race 448 Jim Porter Cirrus SR20 193.383
Race 112 Stu Morse Grumman AA5B 182.103
Race 121 John Dawson Beech Sierra 175.159
Race 34 Chris Murphy RV-4 174.293

Note: Chris Murphy was air boss and just tried to squeeze in a run to be a part of this 1st speed dash event in June - it is way below his best speed in his O-320 powered RV-4 that normally is close to my speed. Marvin Guthrie's Bonanza is hot but I did beat him later in the cross country Tennessee Valley Air Race at Courtland.

Bob Axsom
 
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As we always do, we are comparing apples and oranges here.

Bob has a great process for getting pretty good TAS.

The 2-way speed dash time trials at Courtland, Alabama are not the same as they are average ground speeds (not TAS), most likely have a decent involved, and are unknown if they are average or peak speeds down the runway. Don't get me wrong, these are great speeds and I admire the guys doing this, but they can not be compared to TAS gotten from testing.
 
n5lp said:
Top speed occurs at the lowest possible density altitude with normally aspirated airplanes. It doesn't matter what the airplane is.
Click to expand...

plehrke said:
See this thread (post #5)
http://www.vansairforce.com/community/showthread.php?t=46791

The slope of the curve looks like 2.2 kts increase in TAS for every 1000 ft increase in density altitude (for my RV-6a, IO-360-B2B with Sensenich 72FM8S9-1-85)
Click to expand...

Phil, what I believe Larry is writing is that at WOT, max speed is at the lowest altitude, or more specifically, the lowest density altitude. Your chart showing the increasing TAS with increasing altitude is for a constant power setting. Larry, is this correct?
 
AlexPeterson said:
Phil, what I believe Larry is writing is that at WOT, max speed is at the lowest altitude, or more specifically, the lowest density altitude. Your chart showing the increasing TAS with increasing altitude is for a constant power setting. Larry, is this correct?
Click to expand...
Yes, that is what I meant. Top speed=as fast as you can go.

The factory folks report top speed at sea level in standard conditions at 100% power. I used to always have a picture in my mind of them whizzing just above the waves off San Diego on that elusive standard day. In reality they probably just calculate it.
 
I'm from Missouri...Show Me!

Think you are buttressing arguments with cold hard facts? Add copious amounts of technical arcana to any conversation and you are sure to overwhelm at least some, including me with a mind numbing confusion and an overwhelming urge to fall asleep. I'm yawning. :rolleyes:

Simple guy that I am, technical stuff like aerodynamic efficiencies, fluid dynamics and tax law bore me to tears. :eek:

How fast is my 160 H.P. fixed pitch RV? Fast enough to walk away from a Beech Bonanza after meeting up wing tip to wing tip and agreeing on the exact moment to go WOT. Fast enough to out-pace the locally based Mooney when I announced my RV would be passing on his right. Fast enough to make the same 324 NM trip to Oshkosh within a mere few minutes of a Baron feeding its 2 thirsty engines. :cool:

Fast enough to jump off the ground quickly and demonstrate the RV's high and low speed range to a skeptical spam can driver who before yesterday had never flown in any RV. Fast enough to make it a point of showing that same skeptic how easy it is to flirt with and sometimes exceed 200 MPH GS in level flight when aided by a minor tailwind component. Twice during the demo flight he asked "This has a 160 H.P. engine?" How fast is my RV? I dunno.....you tell me.:)
 
Reproducibility?

TSwezey said:
I did 184 knots coming into Osh this year. Never went that fast before and has never gone that fast again. Divine interventation wanted me to make it to Osh that day.
Click to expand...

I'd be interested to know how well others have been able to reproduce their top speed measurements. My own observation has been that even with careful testing techniques its surprisingly difficult to get results that agree at within an error range smaller than 2-3 knots. Has anyone else tried testing the same configuration under equivalent conditions on different days?

I'd also argue that direct readings from the ASI or EFIS are meaningless in making these comparisons, even if "calibrated".
 
It depends

At Cruise - All TAS - 9,500 feet ROP gets 163 knots and LOP gets 158 knots (7.2g/hr). Drop down a bit where I can get more power and last trip was at 7,000 dead on 170 knots (10.5g/hr). I file flight plans at 160 knots.
 
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2000ft
71F
27.7"
2680rpm
fuel flow 15.4 gph
Using a cx2 ,with IAS180 knots
Calculated TAS 215.4 Mph

Normally cruise around the patch at 2000ft, 22/22 ,7.5GPH, and IAS
135 knots
 
Time of the Speed Dash

I will try to find out for you and all others that are interested. I will not be able to participate this time but I can tell you how it went in June. We arrived the day before the event and tied down by the FBO. The next day the weather was a problem And the organizers were scrambling to get in the planned air show, the speed dash and the cross country air race so we had to be ready whenever they told us it was time to fly. It ended up that the speed dash was flown early followed by the air show then the cross country air race. For the speed dash we were lined up in slowest to fastest order. The idea was to provide a show of increasing speed for the spectators. We were launched in pairs with a large space between airplanes. The first plane made a pass then the air boss cleared in the second plane. After the second plane cleared in the first direction pass the air boss cleared in the first plane for the second pass in the opposite direction. When the first plane cleared in the second pass the second plane was cleared in for the second pass. Those two cleared the course and landed on a different runway as the next pair were being launched. It worked out very well but Chris Murphy (Air Boss) said they learned a lot and I expect some modifications to the procedure as a result.

Chris (RV-4) reads this forum but I will send him an e-mail to see if there is a nominal schedule for the events on October 17, 2009 at Courtland, Alabama. (see www.sportairrace.org)

Bob Axsom
 
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Alan Carroll said:
I'd be interested to know how well others have been able to reproduce their top speed measurements. My own observation has been that even with careful testing techniques its surprisingly difficult to get results that agree at within an error range smaller than 2-3 knots. Has anyone else tried testing the same configuration under equivalent conditions on different days?

I'd also argue that direct readings from the ASI or EFIS are meaningless in making these comparisons, even if "calibrated".
Click to expand...
There is often some small vertical air mass motion. The air in low pressure systems is climbing, and the air in high pressure systems is sinking. That is one reason why low pressure systems have so much cloud, and the air in high pressure systems is usually clear. Thus the speed data from any single test in one weather system might vary by a few knots from a similar test in a different weather system.

Bottom line - performance data from a single flight shouldn't be looked at too closely. Gather data from several flights in different weather systems and average the results.

There is nothing wrong with using ASI or EFIS to access performance, if you have determined the errors in your airspeed indication system. This is a much more efficient test technique than doing a three or four leg GPS test every time you want to measure TAS.
 
Kevin Horton said:
There is often some small vertical air mass motion. The air in low pressure systems is climbing, and the air in high pressure systems is sinking. That is one reason why low pressure systems have so much cloud, and the air in high pressure systems is usually clear. Thus the speed data from any single test in one weather system might vary by a few knots from a similar test in a different weather system.

Bottom line - performance data from a single flight shouldn't be looked at too closely. Gather data from several flights in different weather systems and average the results.

There is nothing wrong with using ASI or EFIS to access performance, if you have determined the errors in your airspeed indication system. This is a much more efficient test technique than doing a three or four leg GPS test every time you want to measure TAS.
Click to expand...

HA-HA-HA-HA-HA.

Bob Axsom
 
Bob Axsom said:
HA-HA-HA-HA-HA.

Bob Axsom
Click to expand...
Bob, please tell me that I am misinterpreting your post. You seem like a good guy. If you are skeptical of what Kevin has to say please make it clearer what you disagree with.

In my experience over about 12 years on this forum and Matt's RV-List and in person, Kevin is absolutely, far and above, the most reliable source of information on test flying and is a hugely valuable resource for we amateurs. His knowledge is understandable, since test flying is what he does all day. He is in the internet hall-of-fame along with Mel, who is the expert on inspections, FARs and paperwork, among other things.

I think Kevin is saying that if the instrumentation is calibrated to his standards you can look at it and know what is going on for that day and that the atmospheric conditions can greatly affect performance. Do you disagree?
 
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Kevin Horton said:
There is often some small vertical air mass motion. The air in low pressure systems is climbing, and the air in high pressure systems is sinking. That is one reason why low pressure systems have so much cloud, and the air in high pressure systems is usually clear. Thus the speed data from any single test in one weather system might vary by a few knots from a similar test in a different weather system.

Bottom line - performance data from a single flight shouldn't be looked at too closely. Gather data from several flights in different weather systems and average the results.

There is nothing wrong with using ASI or EFIS to access performance, if you have determined the errors in your airspeed indication system. This is a much more efficient test technique than doing a three or four leg GPS test every time you want to measure TAS.
Click to expand...

Kevin - thanks for the response.

Do you have any idea how much variance can be introduced by differences in weather systems? Is it knots, or fractions of knots?

What I was getting at in the last part of the comment was that I think relatively few people have carefully determined the errors for their plane, across a range of airspeeds. Often its also not clear how (or if) the calibrated airspeed has been converted to true airspeed. The nice thing about using GPS is that it sidesteps these issues.
 
AlexPeterson said:
Phil, what I believe Larry is writing is that at WOT, max speed is at the lowest altitude, or more specifically, the lowest density altitude.
Click to expand...

n5lp said:
Yes, that is what I meant. Top speed=as fast as you can go.
Click to expand...

Thanks for clarifing. I recorded a bunch of that data a few months ago but have not plotted it up yet. So much data so little time to look at it. I tend to keep flying rather then spend the time analyzing. Maybe over the winter I will get to it.
 
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speed dash and xc race

DanH said:
What time of day is planned for the speed dash? It might be fun to watch.
Click to expand...

The speed dash is planned for 1pm Oct 17th at Courtland,Al and the xc race will take place after the speed dash. The speed dash is contingent on approval of the waivers.

No, the speed dash is not a scientific method to determine your true level top speed but it offers a chance to get an "official result from an independant source.

Chris M
 
No you are not misinterpreting my post

n5lp said:
Bob, please tell me that I am misinterpreting your post. You seem like a good guy. If you are skeptical of what Kevin has to say please make it clearer what you disagree with.

In my experience over about 12 years on this forum and Matt's RV-List and in person, Kevin is absolutely, far and above, the most reliable source of information on test flying and is a hugely valuable resource for we amateurs. His knowledge is understandable, since test flying is what he does all day. He is in the internet hall-of-fame along with Mel, who is the expert on inspections, FARs and paperwork, among other things.

I think Kevin is saying that if the instrumentation is calibrated to his standards you can look at it and know what is going on for that day and that the atmospheric conditions can greatly affect performance. Do you disagree?
Click to expand...

This is about testing period, not personalities or superstar status and I laugh at the possible interpretation that just looking at the instruments is adequate for serious performance testing. It is efficient as Kevin says but it is not adequate for performance testing either absolute or relative. It is a ballpark feel good approach and from years of reading Kevin's posts to me and to others I'm surprised at this muddying of the water.

Bob Axsom
 
Bob Axsom said:
This is about testing period, not personalities or superstar status and I laugh at the possible interpretation that just looking at the instruments is adequate for serious performance testing. It is efficient as Kevin says but it is not adequate for performance testing either absolute or relative. It is a ballpark feel good approach and from years of reading Kevin's posts to me and to others I'm surprised at this muddying of the water.

Bob Axsom
Click to expand...
You need to first do the work to determine the errors in the airspeed indication system. That takes perhaps two flights, plus some time analyzing the data. Once you have done that, you know how to convert from IAS to CAS. The conversion from CAS to TAS is predictable, so you can now convert from IAS to TAS.

This allows you to determine cruise performance from data on a single leg. Hold the conditions long enough to find the stabilized IAS, OAT and altitude, and later you can calculate TAS. Repeat a few more times on other flights in other weather systems and you will get a pretty good idea of the TAS for that aircraft configuration. This is much better than doing three or four legs on the same flight, as all those legs are affected by the same weather system.

Alan Carroll said:
Do you have any idea how much variance can be introduced by differences in weather systems? Is it knots, or fractions of knots?
Click to expand...
I've tried to get data on how much vertical motion there is in low and high pressure systems, but I've never found anything, nor have any meteorologists ever responded to my question. I can say that I recently did two cruise performance tests on my aircraft on different days in different weather systems and got results that differed by about two to three knots. There had been no changes in aircraft configuration between these flights, and the test technique was as identical as I could make it.

Bottom line - data from one flight must be assumed to have an error band of at least two or three knots. If you are looking for the effect of a small mod, relying on test data from only one flight might lead you to reject mods that actually had promise.

Alan Carroll said:
What I was getting at in the last part of the comment was that I think relatively few people have carefully determined the errors for their plane, across a range of airspeeds. Often its also not clear how (or if) the calibrated airspeed has been converted to true airspeed. The nice thing about using GPS is that it sidesteps these issues.
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True, if people are using a proper means to convert from GPS ground speed to TAS. Some folks think you can simply average a bunch of GPS ground speeds and get TAS. That simple approach has errors that increase with the wind speed.
 
Rick6a said:
Think you are buttressing arguments with cold hard facts? Add copious amounts of technical arcana to any conversation and you are sure to overwhelm at least some, including me with a mind numbing confusion and an overwhelming urge to fall asleep. I'm yawning. :rolleyes:

Simple guy that I am, technical stuff like aerodynamic efficiencies, fluid dynamics and tax law bore me to tears. :eek:

How fast is my 160 H.P. fixed pitch RV? Fast enough to walk away from a Beech Bonanza after meeting up wing tip to wing tip and agreeing on the exact moment to go WOT. Fast enough to out-pace the locally based Mooney when I announced my RV would be passing on his right. Fast enough to make the same 324 NM trip to Oshkosh within a mere few minutes of a Baron feeding its 2 thirsty engines. :cool:

Fast enough to jump off the ground quickly and demonstrate the RV's high and low speed range to a skeptical spam can driver who before yesterday had never flown in any RV. Fast enough to make it a point of showing that same skeptic how easy it is to flirt with and sometimes exceed 200 MPH GS in level flight when aided by a minor tailwind component. Twice during the demo flight he asked "This has a 160 H.P. engine?" How fast is my RV? I dunno.....you tell me.:)
Click to expand...

Love it!!! Sounds like an old Drag racer at heart. Before all this bracketing stuff.
 
To mirror another poster

I have been separately to Mt Rushmore, Devil's Tower, Mesa AZ, Page AZ with a trip to Antelope Canyon from 00V Colorado all on day trips.

I also made a day trip to Kitty Hawk from Atlanta GA.

And more day trips:

Key West from Ft Pierce FL

North Eleuthera Bahamas Pink Sand Beach from Ft Pierce Florida.
 
Kevin Horton said:
I can say that I recently did two cruise performance tests on my aircraft on different days in different weather systems and got results that differed by about two to three knots. There had been no changes in aircraft configuration between these flights, and the test technique was as identical as I could make it.
Click to expand...

Interesting. This is very similar to what I've observed.

Kevin Horton said:
Some folks think you can simply average a bunch of GPS ground speeds and get TAS. That simple approach has errors that increase with the wind speed.
Click to expand...

I've been using the NTPS spreadsheet you posted.
 
RV Speeds with new Hartzell Composite Props

After doing multiple runs on multiple days in my RV-4 with the new Hartzell composite two blade propeller I have found the following:

RV-4
180HP IO-360 with one PMAG
Pilot Only
Altitude 5,000 ft
2500 RPM
Full throttle 24.9? Manifold
50 deg ROP
Fuel flow 11.3 GPH

I used the autopilot to fly a ground track N, E, S, W for 2 to 3 minutes per leg and then put the data in the NTPS spread sheet to calculate the TAS.

Result = 178.8 KTS

I have replaced the composite prop with a new Hartzell Scimitar metal prop and should have a comparison later this week.

Just for fun I decided to do the same test in my RV-10 with the Hartzell three blade composite prop. I only made one flight to test the numbers and will repeat it a number of times to verify the results.

RV-10
IO-540 with one Light Speed Ignition
Pilot Only
Altitude 5,000 ft
2500 RPM
Full throttle 25.2? Manifold

Result = 176.3 KTS

Rob Hickman
N401RH RV-4 180HP
N402RH RV-10 260HP
 
For what it's worth, glider tow pilots (as are soaring pilots themselves) are well aware of the effects on speed of flying through alternating bands of lift and sink. In my simple way of thinking, any lift encountered helps hold the airplane up and will result in an almost instant increase in speed and vice versa (at a given power setting and pitch attitude). When towing, if the tow plane encounters lift, its airspeed will immediately increase. Normally we raise the nose to increase our climb rate as a result of the speed increase (generally, glider pilots prefer a constant airspeed on tow; the preferred speed will vary with the type and model of the glider). In other words, we "play" the lift against a constant speed climb in order to haul the glider up to release altitude in the least amount of time.

The same phenomenon affects aircraft in cruise. My guess is that speeds will vary +/- 10 knots (or more) at a given power setting at a fixed altitude in moderate conditions of generalized lift versus conditions of generalized sink. Kevin is right in my opinion, if you want the highest absolute top speed numbers for your airplane (all else being equal), test it in the highest lift conditions you can find. In effect you will be flying slightly downhill while actually maintaining altitude. Sometimes generalized areas of lift are very large. Competition soaring pilots sometimes report "cloud streets" where reliable lift can be found extending over tens if not hundreds, of miles.

Good luck!

Lee...
 
Data here is for my Super Six with an IO-540 and an 80" two bladed D-twist Hartzell paddle, one mag and one Electroair EI (so granted this a bit of apples to oranges, when you consider it against 4-banger RVs, or RV-10s, or Rockets). But I think it's a fun thread, and if you place the results into airplane/RV "classes", it gives us all something to compare to in general (and as an RV brotherhood, something to be proud of...heck, I'm darn impressed with the speeds all RVs attain!)

I did a number of 4-way GPS runs recently, on multiple days, as I prepped for the Pagosa 100 race. Really wanted to get an idea of how accurate my airspeed indicator (Dynon D100) is, and see what I might expect to run in the race. Since I live in Reno, the tests were at 8500' (which also somewhat mirrored the "average" altitude of the course in Pagosa).

I did several runs at various RPMs, to get an idea of the accuracy of the IAS/TAS from the Dynon (and my pitot/static system) at various speeds. What I found was that my Dynon TAS readout was indicating 2.5-5.0 knots fast, when I calculated the TAS from the 4-way spreadsheet from Kevin's site (and Kevin, the standard deviation was always less than .5...even had one that was 0.0, so I think it was pretty good data).

In my max power runs, I averaged 205 kts TAS on the Dynon, and the GPS results showed 202.6 KTAS avg.

In the Pagosa 100, during the level portions I was seeing about that same 205 KTAS on the Dynon, and I ended up running 203.88 KTS/234+ mph for the 100 miles. Granted, there were some downhill portions and some uphill portions, so it's not a scientific validation of my earlier test runs...but it correlates pretty well in a ball park fashion.

The fastest EFIS speed readouts I have seen was with Pierre while racing Steve Barnes side-by-side in his Super Six at 3500 feet on a cool day a while back. EFIS readout was 209 KIAS/218KTAS, which penciled out to 251 MPH. GPS groundspeed readout was also 218 kts, and we had a small direct x-wind indicated, so, although it was not scientific at all, things seemed to match up pretty well (and this was before I did indicator error testing with the GPS method, so I won't yet claim that as a true top-end!) But it does show an increase in speed at a lower density altitude, FWIW.

With respect to Kevin's comments about using the IAS/TAS indications once you have determined the error in your system, I think that is a fair statement for ball-park comparison work (which is what I'd call the 218 kt result above), and would agree that it would be much easier and less expensive, gas-wise.

I'd also agree with Bob A, in that if one was really trying to determine how much a specific speed mod (or even a change in weight or CG) might have on real top speed, that I'd prefer to use the GPS method, and try to duplicate external conditions, to make it as scientific and repeatable as possible. Applying the rigor would be a good thing when you are getting to the nitty gritty, but Kevin's quicker method might be usable for making initial gross (versus fine) measurements of speed changes following mods (perhaps throw a mod out if you can't get close to previous top speed after making the mod).

So as I start to make some speed mods in the quest for catching some of those fast Rockets, I'll likely use both methods as I go along. One goal will be to run a future race and hit or break 250 mph avg speed (will likely have to be one near sea level!)

On the speed dash, Bob or Chris can confirm this, but I believe the racers were required to be level for 5 seconds before entering the speed timing trap, and the desired result is a level top speed. Wind is of course a factor, and might change from run to run, but the two (opposite direction) runs were averaged to get the speed result. Perhaps not totally scientific, but certainly a very fun way to get some speed comparisons!!

Sometimes its fun to be scientific about all this, while at other times its fun to be in Rick's corner and just enjoy the fact that we can blow the doors off spam cans, or see the look on the face of a pax on their first ride in our RVs...showing them the beauty of an airplane that can do so many things so well, perhaps better than any other aircraft (go fast, go slow, to/land at short fields or blend in with high speed traffic at busy airports, do short fun hops or long X-Cs...or go upside down!).

So how fast is my RV...fast enough I guess...but maybe not as fast as it's gonna be! ;)

All intended in fun!

Cheers,
Bob
 
Neat thread....

...and thanks to all/Bob for the great write-up.

My buddy took his -4 to 6000 DA the other day and went WOT and simply could not get the Dynon 180 to show more than 199 MPH TAS. He hadn't leaned the 160 Lyc so he probably left a few MPH/RPM on the table. He was, however, turning 2760 RPM on his new Catto two-blade....what Craig told him.

My-6A, at 7500', WOT, 2740 RPM/Catto three-blade, will true 203 MPH, according to my E6B (Yeah, the same one I used as a student pilot in 1966:eek:, when the earth was cooling:D).

Regards,
 
speed 9A

Mine does 192 MPH at 8000 density wide open at 2585. I have the metal Sensi prop. 160 HP O-320 Superior. Haven't gotten accurate data at lower altitudes, but it is slower, of course. Seems to love 8000 for the top speed, as I haven't done quite as well at somewhat higher altitudes.
What really amazes me is the economy it offers up at lower throttle settings.
Love my 9A!!

Regards,
Chris
 
Plane is getting faster!

My plane has about 200 hobbs hrs on it now. All throughout the initial testing the plane gave a pretty consistent 173 knots TAS at 10.8 fuel flow around 8000'. The plane is now averaging between 185 and 189 knots TAS at similar settings. I saw 189 TAS at 4000' and 10.9 GPH today. My guess is that the engine is looser and producing more HP now. I am blown away by this plane! I still need to do some more in depth investigation to make sure that these numbers are accurate but nothing else has been changed on the plane and I am seeing this consistently now.

EDIT: after reading Kevin's post (2 posts after this one) I remembered that I did modify the static system to include the trio Alt Hold unit. It is therefore possible that I have a static leak and not increased horsepower to thank for these numbers. I thought about just deleting this post but then thought it might be good information for anyone else who see numbers that might be too good to be true. I will repost back again after testing my static system further.
 
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andrew phillips said:
My plane has about 200 hobbs hrs on it now. All throughout the initial testing the plane gave a pretty consistent 173 knots TAS at 10.8 fuel flow around 8000'. The plane is now averaging between 185 and 189 knots TAS at similar settings. I saw 189 TAS at 4000' and 10.9 GPH today. My guess is that the engine is looser and producing more HP now. I am blown away by this plane! I still need to do some more in depth investigation to make sure that these numbers are accurate but nothing else has been changed on the plane and I am seeing this consistently now.
Click to expand...
I would expect the engine power to increase a bit as it broke in, but a TAS increase this large implies the engine power increased by about 25%, which is extremely unlikely. There must be another cause lurking somewhere.

Are the TAS values calculated from GPS data on multiple headings, or are they calculated by your EFIS based on pitot-static data?

If the TAS values are from the EFIS, I recommend you check for a static system leak. The pressure inside the aircraft is usually less than the ambient pressure, so a static system leak will cause the pressure in the static system to be too low, leading to IAS values that are too high, and this would cause the EFIS to calculate a too high TAS.

Note that a static system leak will also affect the indicated altitude, so if you have such a leak you aren't flying at the altitudes you think you are.
 
Subaru Speeds

My Subaru STI engine on my RV7A has been modified with higher compression and a longer stroke crankshaft, and running normally asperated, the turbo is gone for now. These days my 3 way average GPS GS, (via the online calculator) are coming in at 164 Knots, or about 189 MPH. I see this at a reasonable cruise setting of 4600 engine RPMs (2300 prop) and full throttle up at 8000', 5400 RPMs would be redline on the prop. I have been able to repeat this average speed in several tests. Todays testing seemed to verify that going with straight pipe and no muffler made it lots louder but not really noticeably faster. The muffler will go back on soon.

Reading these posts makes me feel a little better about the performance I am seeing with this engine. Not bad when you think that this is coming from a little more than 150 Cubic Inches displacement with no boost. I have been comparing Van's performance specs for cruising at 8000' and feeling a little dissapointed that I am not closer to achieving that level of performance.

I miss the turbo charger and the ability I had to control manifold pressure. With it I could easily exceed Van's published performace specs. I made a speed run with the turbo at 8000' running 47 square, gotta love a number like that. That was not a three way GS average, but I have learned just how much error my TAS readout has on the EFIS. Subtracting that error, I was still getting a solid 202 knots. Unfortunatley I had a problem with the turbo so I decided to back off a little and try something a little simpler and lighter, gee where have I heard that before:)

My plane doesn't quite set my hair on fire like it did with the turbo, but it feels real good to be building some time on the machine in this configuration.

I still need to get the wheel pant to gear leg intersection fairings on so maybe I can still eek out a few more knots. With that turbo power it seemed like drag did not matter...

Randy C
 
9A speeds

I was about 11 west of Ogden yesterday inbound for landing getting ready to connack the tower. Tower referenced me to an inbound from the north as "a fast mover at your 2 o'clock, 5400' and 160 kts".
And I was slowing down.
 
Kevin was right

So I learned today that you must listen to Kevin Horton because he knows! If you read my post which is on the previous page you will see that I was really enthusiastic about some unnatural speed gains of my aircraft. Kevin suggested that this might be due to a static leak instead of the grace of the god of speed. I saw Kevin at the airport this morning and we discussed the static system further. I investigated and found the static line had fallen off the "T" connection near the 2 static ports...1 point for Kevin. I did a speed run based on GPS ground speeds today then used Kevin's spreadsheet to calculate that the plane was doing 173.6 K TAS at 8000' at 10.9 GPH....another point to Kevin. This number is within 0.6 knots of my EFIS TAS when the static was not leaking. Problem solved, plane still fast enough.
 
Andrew,

I'm glad you found and fixed the leak. A static system error big enough to give the calculated TAS errors you reported would also cause indicated altitude errors on the order of 230 ft at 8000 ft. If you were flying a VFR cruising altitude, that would put you pretty close to the IFR traffic.
 
Kevin -you rock! I am glad that you are on our side...
Thanks for always taking the time to teach when the opportunity presents itself.
 
Another 9A data point

Finally got around to doing a speed test today as it was clear and calm.
7500' (~9000 DA), WOT yielded 200 mph true airspeed at ~2750 RPM and burning about 10 gph. Carrying about 12 gallons of fuel and 1 pax in addition to me. A bit better than Van's numbers, but I'm running an IO360 in my 9A so perhaps not unexpected. All in all, I'm pretty happy with this number.

greg
 
at the Pumpkin Dash

AT the TVARII pumpkin dash, my RV-4 was clocked at an average over the ground of 220mph. I was not at full thottle and max rpm because I had reached my tested limit of 190kias. I may have exceeded that slightly.

It was below standard temp that day and I cant remember the pressure but I am sure the dens. alt. was quite low which resulted in some pretty fast speeds.

I normally fly out of a field ele. of about 5000ft and I was caught by suprise by the amount performance that was available.

stock 160hp 0-320 catto prop.

After watching the video of race 41 it is easy to see he was significantly faster than I was.

Chris M RACE34
 
With light fuel, solo, 8000ft density altitude, balls to the wall, 178kts true -- confirmed on multiple occasions with 4-way GPS runs using the spreadsheet on Kevin Horton's site:

http://go.phpwebhosting.com/~khorton/rv8/phplinks/index.php?&PID=49

I have found that weight has a fairly significant effect on top speed. When I am two-up and loaded down for a trip my typical cruise at 9500ft is 163kts TAS at 21inches and 2400 RPM (ROP).

My plane comes in at 1130lbs empty with a Hartzell C/S prop and dual mags.
 
How fast???? I don't know exactly (somewhere between 150 & 250 knots), and it doesn't matter. It only matters that I'm faster than any of the other Cincinnati River Rats. We all have O-360's with CS props. However, mine is a Showplanes fastback (key word FAST), and I have a 200RV Whirlwind, plus it's the lightest of all, except maybe Wizz's RV-4 (don't know if it's ever been weighed). Second fastest is Mutha (JT), and he's a couple knots slower than me. When someone's chasing you, it doesn't matter how fast you are.... it only matters how fast he (they) is (are). Confused? Me too....

Scott
RV-8 FASTback
 
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