Observed RV-10 flying qualities

Hey guys! As a pilot test flying number 15, I have a few observations and questions for the open floor. Vans is aware of all my less than flattering observations, and I am throwing these few things out for consumption and discussion. Flamers who think I am downing the 10, please stay at home quietly wioth your hands in your lap, or go and drive some more rivets..
I think it is the most awsome, smooth, best flying GA plane I have ever flown. This, coming from a professional pilot with over 12,000 hours of flying time. Nuff said.

....First, the tunnel is EXTREMELY hot! We took the rear cabin heat scat tube and blasted the rear cabin heat fresh air directly into the tunnel. I also installed some aluminumized insulation on the back of firewall in the tunnel, and under all the fuel lines. All this seemed to accomplish, was lower the fuel temp sufficiently so the engine would not vapor lock again. Before we did all this, the engine quit on me once, started right up when elec pump turned on.(IMHO, ground your 10 if the secondary pump is inop!)
Due to the high fuel flow at the cruise power setting I had set (carburated engine, MA 4), I had virtually no time to check the engine page after I got the Efis one alert of low fuel pressure. In fact, the pressure never even went below 1 psi, yet the engine quit as well.(mere seconds, but did in fact quit). The owner and his son, and a fellow pilot, have since put the front scat fresh air tube to the tunnel also, they say it makes a big difference. We now have no cabin heat now until a new cabin heat assembly is installed. But what the heck, we live in Florida!

....The highest TAS I am able to obtain is 191 MPH TAS. This is off the Efis one which appears to be right on. This is far below the Vans advertised numbers of 201. and max cruise of 211, well, just not gonna happen. This plane is 35 lbs lighter than the prototype, and Specs are as follows: Pilot 175 lbs, 20 gallons fuel, no paint, interior only seats. 8000?feet, 2300 RPM, 21.5 IMAP. Tas 191 MPH. ( I have found 2300 gives the best IAS vs 2400.

....There is definately not enough elevator authority. Any more than 1/3 flaps in the above mentioned weight catagory, one pilot, the plane cannot be trimmed to fly hands off at 85, or even 90 MPH. Aft CG will help this obviously, but, IMHO this plane will not be able to be fown with hands off in the patter and full flaps at ant weight or CG (IMHO, I am extrapolating, still testing). The good thing that I love is, the stall speed flaps up is, 69 IMPH, and full flaps 59 IMPH. Also extreme care must be taken upon landing so as not to crash the nose gear. Loss of elevator authority occurs extremely rapidly. Especially with full flaps selected! The flaps for me any way, are kind of a high lift/high drag device that I actually prefer not to use. I fly the plane 100% of the time now with flaps up, and can easily stop on our grass strip in less than 1500 feet from the end of the runway and not touch the brakes! Even to taxi!

....Unbelievable awsome flight characteristics I have observed include: Virtually no stall!, just a 600 FPM sink, that any passenger with 5 minutes of instruction could learn, and to land the plane and survive! Just stear with the rudders and hold the stick back!...Accelerated stalls are not stalls, just moderate shaking of the tail, I have yet to make with wing aggressively stall, this would almost have to be an accrobatic/violent maneouver!....I am absolutely 100% NOT worried about anybody EVER spinning this plane inadvertantly!...Heavy on the controls compared to all other RV?s, but so well balanced, who cares! Can you say stable?....Power on "stalls" (remember, basically will not stall) are a climbing event! Just watch those temps! Have a tree coming up at the end of the runway, dangerously close? Well you might not clear the tre, But, you will not stall this plane in! Awsome!.... Barely 2 Fugoids in rudder and undetectable in other two axis at any airspeed! Stable, stable, stable!....Rudder almost too effective. Turns are almost a feet on the floor manouver. Only a VERY anal pilot would notice any adverse yaw during a normal cxruise or pattern turn and no coordinated rudder.....
This plane is awsome and worth every penny! (PS ..Congratulations Jim!!)
Glen

Comments from non flamers gentlemen!!??

Regarding elevator authority...

Have you tried putting any ballast in the baggage area? I'm not a fan of ballast, but if you're solo or only have one passenger, a few pounds of ballast in the back isn't gonna hurt performance very much. Also, moving the CG back a bit will increase cruise speed, although I have no idea how much.

How accurate are your engine gauges and how clean is the airframe? Is it possible that your tach and/or MP gauge read high?

Glen,

I enjoyed watching the first flight for an hour or so last week, wondered where you have been.

My father and two friends just returned from Copperstate, they flew over early today from Bakersfield and spent 3 hrs. there-- one hour sitting in and investigating the RV-10. and they got back an hour ago.

I'll pass on the above info-- Dad watched the video the other day also.

What brand is your parachute? looks comfortable.

mark

OK, let me see if I can help. That's what all of us are here for. Right ow I could have, but don't know for sure, more hours on my 10 than the factory. I jsut crossed 126 yesterday.
The tunnel is extremely hot. I think I maight have addressed this in an earlier post. I disconnected the scat tube to the heater boxes completely. I mentioned it to Van while at the factroy last week and they agreed that there is a problem. I don't know what their intended fix is yet, but for those who are still building, I would recommend that you not directly attach the heater boxes to the firewall, as they and the firewall are just acting as heat sinks for the hot air. Stand them off with spacers, maybe phenolic, and I think that should help.
As for the CG loading, I'm assuming you have the metal prop, but you didn't mention it. I have the MT prop, which is supposedly lighter. Whatever the reason, I do not appear to have the cg issues. I have flown it solo with full fuel, and at gross with 4 adults, and have enough elevator authority to trim it hands off on final. I also went with the heavier pc 925 battery. I'd rather carry something useful rather than ballast.
there's lots of ways to fix these problems.
As for the speed, I seem to true out at those same airspeeds, 162-167 kts. We did a side by side comparison with the factory airplane last week at 8500' and FT and 2500 rpm. If anything, the factory plane was 1 mph faster. However, IF I have the horsepower that I am supposed to have, Van seems to think mine is about 12 mph slower. Who really knows without taking a hartzell prop and putting it on my airplane, or putting the MT on the factory.

Please don't hesitate to give me a call. I'm in Georgia, and might even have time to come down and help. You are certainly welcome to come here, GA04, and fly mine.
Vic
404-307-5133 cell
770-898-2222 home

Gross weight

Hey Vic, I did get a copy of your weight and balance spreadsheet from Mike Stewart. Thanks.

The concerns raised in the original post of this thread was one of the reasons I asked. From looking at your spreadsheet and the specs on Van's website it looks like the RV-10 is a four place for 4 "FAA adults". Not that that's a bad thing. I went back and looked at the specs for the Piper Arrow that I flew a few years ago and they compare pretty close. I know I've had 4 pretty good size people in one of those, but it must have been with reduced fuel.

I did notice that you placed your gross weight at 2850, which helps since your empty weight was higher than Van's "spec". I know the builder sets this, but I was wondering what Van's thought of it. I thought they were being pretty hard nosed on any "mods" such as this as well as larger engines.

Ken

Thanks Vic...

vic syracuse said:

OK, let me see if I can help. That's what all of us are here for. Right ow I could have, but don't know for sure, more hours on my 10 than the factory. I jsut crossed 126 yesterday.
The tunnel is extremely hot. I think I maight have addressed this in an earlier post. I disconnected the scat tube to the heater boxes completely. I mentioned it to Van while at the factroy last week and they agreed that there is a problem. I don't know what their intended fix is yet, but for those who are still building, I would recommend that you not directly attach the heater boxes to the firewall, as they and the firewall are just acting as heat sinks for the hot air. Stand them off with spacers, maybe phenolic, and I think that should help.
As for the CG loading, I'm assuming you have the metal prop, but you didn't mention it. I have the MT prop, which is supposedly lighter. Whatever the reason, I do not appear to have the cg issues. I have flown it solo with full fuel, and at gross with 4 adults, and have enough elevator authority to trim it hands off on final. I also went with the heavier pc 925 battery. I'd rather carry something useful rather than ballast.
there's lots of ways to fix these problems.
As for the speed, I seem to true out at those same airspeeds, 162-167 kts. We did a side by side comparison with the factory airplane last week at 8500' and FT and 2500 rpm. If anything, the factory plane was 1 mph faster. However, IF I have the horsepower that I am supposed to have, Van seems to think mine is about 12 mph slower. Who really knows without taking a hartzell prop and putting it on my airplane, or putting the MT on the factory.

Please don't hesitate to give me a call. I'm in Georgia, and might even have time to come down and help. You are certainly welcome to come here, GA04, and fly mine.
Vic
404-307-5133 cell
770-898-2222 home

Click to expand...

Ok first, I believe this is no more than a MAYBE a 195 MPH plane. To even get 5 more MPH out of this plane, well, will be very difficult. Second, nope we have not tried any aft CG work yet, I want to FULLY explore the entire fwd CG envelope first. OBVIOUSLY any aft CG condition will slightly speed up (I guess maybe 1 or 2 mph) this plane. The CG empty is essentially at the fwd CG set by Vans. It has been flow with passenger ballast, pilot and full fuel, with a very slight increase in the elevator authority issue. Very slight. 331JH has the Hartzell prop specifically supplied by vans. The engine is a Schmidt Aviation rebuild O-540, chrome cyl, new rods, yellow tag crank, balanced within .1 grams dynamicly by juan Jarrod, rated at 260 HP with an MA 4-5 carb. New mags, Vetterman Exhaust, all vans FF.
So now you all know the powerplant, you can also see that all fairings are installed, so I cannot see where we will get any more appreciable speed, like at least 10 more MPH! VEERRRRYYY difficult.
As a side note, anybody looking for an engine should contact Schmidt Aviation at Opa Loka airport in Fl. He built this engine, delivered as described above, with 2 hrs break in time, w/o governor (Jim bought his governor on Ebay for 75 bucks, works great!) for $19,000 !!!!!!!!!!!!!!!!
I have turned one guy from England onto (Tom) Schmidt, he saved 50% over what an engine was going to cost him in England! Schmidt builds a lot of engines and has cheap cores and can do certified for a little more money. Awsome deal...

Glen

yes

glenmthompson....First, the tunnel is EXTREMELY hot! We took the rear cabin heat scat tube and blasted the rear cabin heat fresh air directly into the tunnel.
(More insulation?)

....The highest TAS I am able to obtain is 191 MPH TAS.
(Van's aircraft has a history of publishing very accurate specs for all their aircraft. Do you have a 3 blade MT prop? Subtract 5-8 mph for this option alone. There are cases where builders of other RV models where slow by 10mph, but that is rare. Most RV's meet or exceed the factory specs. Let's assume it is your plane for a while and figure out what the difference is between your plane and the factory plane.)


....There is definitely not enough elevator authority.
(I can tell you many factory planes exhibit CG issues when flown solo. From what you said it sounds like you don't have enough TRIM AUTHORITY. I assume you could fly with the stick or could even stall by pulling back. My early days of flying freight and 135 charters in Seneca II's, I recall needing a few cases of oil in the aft baggage compartment. Also my first RV was a RV-4 with constant speed prop, solo was nose heavy and needed full up trim on approach and it was just enough. My trim required several adjustments to get right, at a loss of some down trim, which was not needed. Not enough elevator authority? What does that mean really? That implies you can not flare when you land? Sounds like a minor problem of adjusting your trim tab or putting some oil in the trunk.)

George

Hi Glen--I'm not picking here, just trying to help, so please take no offense

..The highest TAS I am able to obtain is 191 MPH TAS. This is off the Efis one which appears to be right on. This is far below the Vans advertised numbers of 201. and max cruise of 211, well, just not gonna happen. This plane is 35 lbs lighter than the prototype, and Specs are as follows: Pilot 175 lbs, 20 gallons fuel, no paint, interior only seats. 8000?feet, 2300 RPM, 21.5 IMAP. Tas 191 MPH. ( I have found 2300 gives the best IAS vs 2400.

Click to expand...

A couple of things come to mind here. First, as has been mentioned elsewhere, have you calibrated your EFIS readings yet? I'm using the EFIS/One as well, and intially had airspeed indications about 4% high, which turned out to be a static leak (since fixed). Kevin Horton's RV-8 site has excellent articles with Excel spreadsheets to help calibrate the airdata instruments.

To determine your TAS, ignore the indicated airspeed, just hold a constant altitude and fly four legs in smooth air at a constant power setting and orthogonal headings (i.e. 360, 90,180,270). Note the ground speeds on each leg. (you can write it down or take a series of digital photos, but the simplest way is to download the EFIS file). Plug the numbers into Kevin's spreadsheet and you can determine the TAS and the winds. He also has a spreadsheet you can use to determine what your CAS was at that altitude/temp.

I don't have a power chart for the o-540 handy, but I'm assuming that the 260 hp rating is WOT at sea level and 2700 RPM. On my IO-360, your power setting of 21.5 MAP and 2300 is about 63% power at 8000' with an OAT of 5 degrees C. Van's spec at 55% power is 181mph and at 75% power is 201mph.

It looks like your airplane is within 0.5% of the published spec, and a little on the high side.

To get 75% power at 8000', you need WOT, 2700 RPM, and leaned for best power.

Also, you need to check the tach with a good optical tach. Mine initially read 7% high. This is a very easy fix in the EFIS.

Hope this helps

James Freeman

glenmthompson said:

So now you all know the powerplant, you can also see that all fairings are installed, so I cannot see where we will get any more appreciable speed, like at least 10 more MPH! VEERRRRYYY difficult.

Glen

Click to expand...

I am not saying that it is surely the case here without being able to inspect the airplane. I have seen many RV's "with all the fairings installed", but not properly aligned. They can be missaligned enough to easily lose 5 MPH and more. I think you should verify some of these type of issues before proclaiming the published perf. figures false.

By the way ... on the elevator issue, have you ever flown a C-182 solo and landed with full flaps???

Scott

When I examined the heater valves supplied with the -10 kit, the first thing I thought was that they don't seal tight and the air would get mighty hot wafting slowly through the muffs, SCAT and tunnel. Guess I was right.

If you use the stock valves, maybe add a foam ring to seal the doors better. Then use SCEET hose and wrap with insulation of some sort to reduce radiation into the tunnel. You'll probably have to add a small scoop to duct cool air into the tunnel as well. With the pumps here, it gives me the willies to think about vapor lock.

As far as the lack of elevator/ trim authority has been noted in the last full flight test in Kitplanes on the -10 with full flaps and forward C of G. My -6A is little different under these conditions but I rarely use full flap because the aircraft lands much better with no flap or half flap. I've never understood why so many RV pilots insist on using full flap for every landing- even on 3000+ plus runways. They are pretty piggy feeling in that configuration. Van's certainly couldn't have made the elevator, stab and trim tabs much bigger on the -10, they look like something off a Navajo!

listed speeds vs. actual.

There are several items that need mentioning about a "slow" -10. First; isn't the O-540 10-15 HP down on the IO-540? I seem to remember 240 or 235 as a listed output. That will make some difference. A 3 blade Mt will also be slightly slower than a 2 blade Hartzel. Since the 10 is a larger plane than the other RV's MINOR alignment problems will cause a larger deviation from spec.
That said I would suggest that you check horizontal stab incidence. If your CG is so forward that you are flying with signifigant up trim you will increase your drag and slow the plane down. Van provides a great kit, but there are always some variations possible. Have someone watch, or better yet photograph the elevator position in cruise. Is the elevator directly in trail or deflected? A small deflection makes a big difference at almost 200 MPH! These are just suggested checks, so hope things work out well for you. Try a little ballast to see if there's a difference. Fly safe.
Bill Jepson

Great responses....

Rotary10-RV said:

There are several items that need mentioning about a "slow" -10. First; isn't the O-540 10-15 HP down on the IO-540? I seem to remember 240 or 235 as a listed output. That will make some difference. A 3 blade Mt will also be slightly slower than a 2 blade Hartzel. Since the 10 is a larger plane than the other RV's MINOR alignment problems will cause a larger deviation from spec.
That said I would suggest that you check horizontal stab incidence. If your CG is so forward that you are flying with signifigant up trim you will increase your drag and slow the plane down. Van provides a great kit, but there are always some variations possible. Have someone watch, or better yet photograph the elevator position in cruise. Is the elevator directly in trail or deflected? A small deflection makes a big difference at almost 200 MPH! These are just suggested checks, so hope things work out well for you. Try a little ballast to see if there's a difference. Fly safe.
Bill Jepson

Click to expand...

Thnx for the great responses guys. For all's consumption:

**** The plane has the Vans Hartzell prop made exclusively for the 10. 2 blade.
**** Took out the 1/4" shim under stab LE and installed 1/8" to help with elevator authority. Can see elev. in cruise. The leading edge of the counter balance (perfect reference on any Vans), is up 3/16 (elev. down) in level flight and 180 MPH indicated. So we are getting a "tail up effect". Should be good for TAS?
**** As previously stated, we have not moved the CG aft yet until we are satisifed and comfortable with a nice, safe fwd CG flight regime. Still have not been over 205 MPH indicated BTW.
**** This is my 6'th plane I have worked on/helped finish, built 2, 100% by myself, and I am a Sun N Fun best workmanship award winner, so I feel I am qualified to say the fairings are on straight, and confirmed so. BTW, there are 2 entry steps installed, this is quite a bit of drag. Any comments on this step thing?
**** If the RPM is moved up to 2700 RPM, I lose around 5 MPH indicated,... at cruise, high HP is not equated to high speed. Torque and propeller efficiency is. Just ask any RV racer. As previously stated I have played around and found that 2300 gives the best indicated speed. Efis one not calibrated? Hmm, good idea, but....My Wag of the GS I am getting along with the winds aloft confirm my findings of aroung 190 TAS.
**** Are there any other 10 flyers that have TAS calcs that they would like to share? Maybe a 10 in south florida that I can fly with? (West Palm Beach)
**** Yes, I have flown a 182, fwd CG with full flaps. Heavy on the controls, not alot of authority in the flare, but can trim it hands off at pattern speeds.
****Three of us have flown this plane and all agree 100% that there is not enough elev, authority in the landing phase. One of the pilots is an EAA flight advisor with dozens of first flights under his belt.
**** The stab trim control surface is HUGE! The authority is limited by the cables that "feed" the tab. I have set the trim tab/motor to take the full travel of the cables. Now, if we maybe set the "neutral" of the tab on the up trim side, that will give more nose up authority yes, of course, BUT....As you add nose up trip remember, you are effectively lowering the stab authority due to decreased area as the trim tab is moved downward to give you more trim authority in the pattern. Great idea, but I believe this will worsen the "not enough elevator" on landing issue with full flaps. BTW, there is a noticable increase in elev. authority if the plane is landed with nose down trim and heavy stick forces, this lends credance to my theory. (Nose gear retracted landing technique, trim full nose down for landing)
**** Did a simulated engine failure on short final today, and found very quickly that you need around 10 deg. nose down RIGHT NOW, just as in other RV's. But, The "RV sink" just was not there, very easy, as long as A/S was maintained, in this case I used 85 MPH. In this case, no flap, it was a very easy and intuitive.
**** As far as more insulation in the tunnel, remember, the fuel pump, FF transducer and filter are all mounted on the lower skin, and all suck up huge amounts of heat. Yep, good idea, but I think to be effective, we might need to elevate all fuel items. and add a huge amount of insulation, maybe as much as we have in the floor under our feet???
Keep it coming, this is new to all of us, and we are all learning, even Vans!
Glen

My observations after 94.7 hours.

Well the discussion about the amount of elevator on the 10 is not new. When I flew for the first time I had 100 lbs. of balast in the baggage comp. That was the recommondation of Van and Ken Kruger. If you have 1 or 2 people aboard you should have at least 25 lbs of lead shot in the back. It will land much nicer. The statement that you don't have enough trim with full flaps is not something I have experienced. I have enough to fly hands off at 80 mph but then again I carry 25 lbs of shot unless I have baggage in board. I was fully loaded this this last weekend with 4 aboard and full fuel. Almost no trim is needed during landing. This plane is designed for 4 people and baggage and it really likes flying with that load.
The point about speed. Here is what I have done. I flew with Ken Kruger from Van's and we did the normal speed box. This was done at about 5700 ft to adjust for temp. to equal 8000ft. The power setting that I have from Lycoming matched the settings we used. 75% power = 2500 rpm. WOT and leaned to 100 deg rich of peak. Ken crunched the numbers a few days later and I caught up with him at OSH. He said that I might have a rigging problem because my top speed was 198 mph. He speculated that my ailerons may be set to low. Well on the way back home I had 1400 miles to look at the aileron position in the cruise configuration. As it turned out my ailerons were down almost 3/8" on each side. I must not of had my flaps all the way up when I made the initial adjustment. Well I have not done another speed run but the plane is noticably faster. Ken also said that 2 other builders also did the speed boxes a came in at 208 mph.
My tunnel does not seem to get that hot. It gets warm but never hot. It may be due to having a blast tube that runs from the front of my engine to a cover around the fuel pump. The cover came with the engine I bought. After It cools the fuel pump the air comes back towards the firewall. That my be the reason I am not experiencing the high tunnel temps. One more thing. I am running the older Hartzell and AWI exhaust not the Vetterman. Van's thinks that my plane should be 2 to 4 mph. slower than the newer 2 blade and the vetter. exhaust. Van's has wanted to do a retest of my planes speed but I been having way to much fun flying to set up the test time. I should happen this month. Randy N610RV

Yep, remembered something

Randy DeBauw said:

Well the discussion about the amount of elevator on the 10 is not new. When I flew for the first time I had 100 lbs. of balast in the baggage comp. That was the recommondation of Van and Ken Kruger. If you have 1 or 2 people aboard you should have at least 25 lbs of lead shot in the back. It will land much nicer. The statement that you don't have enough trim with full flaps is not something I have experienced. I have enough to fly hands off at 80 mph but then again I carry 25 lbs of shot unless I have baggage in board. I was fully loaded this this last weekend with 4 aboard and full fuel. Almost no trim is needed during landing. This plane is designed for 4 people and baggage and it really likes flying with that load.
The point about speed. Here is what I have done. I flew with Ken Kruger from Van's and we did the normal speed box. This was done at about 5700 ft to adjust for temp. to equal 8000ft. The power setting that I have from Lycoming matched the settings we used. 75% power = 2500 rpm. WOT and leaned to 100 deg rich of peak. Ken crunched the numbers a few days later and I caught up with him at OSH. He said that I might have a rigging problem because my top speed was 198 mph. He speculated that my ailerons may be set to low. Well on the way back home I had 1400 miles to look at the aileron position in the cruise configuration. As it turned out my ailerons were down almost 3/8" on each side. I must not of had my flaps all the way up when I made the initial adjustment. Well I have not done another speed run but the plane is noticably faster. Ken also said that 2 other builders also did the speed boxes a came in at 208 mph.
My tunnel does not seem to get that hot. It gets warm but never hot. It may be due to having a blast tube that runs from the front of my engine to a cover around the fuel pump. The cover came with the engine I bought. After It cools the fuel pump the air comes back towards the firewall. That my be the reason I am not experiencing the high tunnel temps. One more thing. I am running the older Hartzell and AWI exhaust not the Vetterman. Van's thinks that my plane should be 2 to 4 mph. slower than the newer 2 blade and the vetter. exhaust. Van's has wanted to do a retest of my planes speed but I been having way to much fun flying to set up the test time. I should happen this month. Randy N610RV

Click to expand...

Thankd Randy,ya just jogged my memory on something. The ailerons are at least 3/8" below the trailing edge of the tips inflight. This makes that much difference? It should act kind of like flaps, move the cg affectively fwd, and add induced and parasitic drag. HHHMMM How much faster do you think it really is?
Is your hands off flying at 80 mph with full flaps? We get hands off trimming up to about 25% to 1/3 flaps.
One other problem I forgot to mention, we have a very hot #5 cylender, 40 deg hotter in cruis, and up to 50 in climb. We are going to try to either swap or calibrate #5, next time the cowling is off, heck, time to do the first erl change any way.
I still love to fly this plane, and cannot wait to expand the box away from the feild! See you guys out to Clewiston and up to Okeechobee!
Glen

RV-10 excess floor heat

glenmthompson said:

**** As far as more insulation in the tunnel, remember, the fuel pump, FF transducer and filter are all mounted on the lower skin, and all suck up huge amounts of heat. Yep, good idea, but I think to be effective, we might need to elevate all fuel items. and add a huge amount of insulation, maybe as much as we have in the floor under our feet???
Keep it coming, this is new to all of us, and we are all learning, even Vans!
Glen

Click to expand...

After thinking about this while installing the ailerons on my -9 I'm confused about the excess heat that is coming up from the floor of the -10's. Is it coming through the heater vent or through the floorboards via the exhaust?

If the heat is entering the center console via the heater vent I have no ideas. However, if the heat is coming trough the floor from the exhaust I have two possible solutions. (Since I have never seen a -10 in person, please take these ideas with not a grain of salt but a block.)

Suggestion one: Can you install some vortex generators under the cowling, in front of the where the exhaust stacks exit? The idea is to keep (get?) the prop wash attached to the fuselage and provide a boundary of cool air that either mixes with the exhaust or just simply keeps it away from the fuselage.

Suggestion two: Add augmenters to the exhaust stacks. I have read this will help get the exhaust out of the engine better and, more importantly, move the exhaust down and away from the bottom of the aircraft. (See the article on Jawbreaker, page 54, in the April 2004 issue of Sport Aviation. It's the one with with the RV-10 on the cover, I'm sure you have it laying around.)

These are just the thoughts of some guy who isn?t even building a -10 so take them for what they are worth.

Been there done that...

N941WR said:

After thinking about this while installing the ailerons on my -9 I'm confused about the excess heat that is coming up from the floor of the -10's. Is it coming through the heater vent or through the floorboards via the exhaust?

If the heat is entering the center console via the heater vent I have no ideas. However, if the heat is coming trough the floor from the exhaust I have two possible solutions. (Since I have never seen a -10 in person, please take these ideas with not a grain of salt but a block.)

Suggestion one: Can you install some vortex generators under the cowling, in front of the where the exhaust stacks exit? The idea is to keep (get?) the prop wash attached to the fuselage and provide a boundary of cool air that either mixes with the exhaust or just simply keeps it away from the fuselage.

Suggestion two: Add augmenters to the exhaust stacks. I have read this will help get the exhaust out of the engine better and, more importantly, move the exhaust down and away from the bottom of the aircraft. (See the article on Jawbreaker, page 54, in the April 2004 issue of Sport Aviation. It's the one with with the RV-10 on the cover, I'm sure you have it laying around.)

These are just the thoughts of some guy who isn?t even building a -10 so take them for what they are worth.

Click to expand...

Yep, added the 6' exhaust extensions today before flying, they were supplied by Vettermans. They point out and down and keep the exhaust 100% from contacting the CS (center section) bottom skin now. Still pretty warm, but now at least I can touch and leave my hand on the side of the center section near the floor. Before, I could not leave my hand for more than a couple of seconds.. Yes gentlemen, it was that hot!
To reiterate, we have insulated the bottom skin for 3 feet aft of the firewall. Insulated the firewall back side, inside the center section. We now have BOTH heater valves wired open with only the fresh supply air entering the CS full time. Nope, sorry guys, this problem is NOT the heater valves leaking air/not closing properly. Wish it was.
On a previous flight with just one fresh air vent venting, I felt hot air, and stuck my sandaled foot under the rudder pedal to see where it was coming from. Burned my foot, red like a sunburn, ouch! ( No peanut gallery comments on the benefits of wearing shoes, hey, I live in FL. haha.) It was a blast of super hot air leaking out around the front heater vent (Heater was not hooked up to muffler header), the air was CS air escaping and venting out quite briskly through the gap between the heater vent tube and the CS sidewall.
Yep, I'd say Vans has a problem here, But ya know what. I LOVE THIS PLANE!!!! This too shall pass!!! Rock on Jim!!!!! Long live 331JH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Next, autopilot tweaking and higher speed testing!
Glen

RV-10 Info

glenmthompson said:

.......I LOVE THIS PLANE!!!! This too shall pass!!! Rock on Jim!!!!! Long live 331JH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Next, autopilot tweaking and higher speed testing!
Glen

Click to expand...

Great info Glen...I'm sure this will most certainly be helpful information for the other RV-10 builders out there. Only one question.....what the hell are you doing up at this hour reading and writing about airplanes....get a life, huh?

Brent

Just to clearify.

Glen I wanted to crearify my statement on 3/8". It was the ailerons being down lower than the flaps. So you could imagine a pair of outriggers out there adding a lot of drag. The airlerons are even with the flaps now but you are correct that the tips are down about 1/4 inch when in cruise flight. I will tackel the repositioning of the tips this winter. Randy

Ok , clarification...

Randy DeBauw said:

Glen I wanted to crearify my statement on 3/8". It was the ailerons being down lower than the flaps. So you could imagine a pair of outriggers out there adding a lot of drag. The airlerons are even with the flaps now but you are correct that the tips are down about 1/4 inch when in cruise flight. I will tackle the repositioning of the tips this winter. Randy

Click to expand...

So Randy, Do you think we have issues in the 10 with the tips being out of rig by design or out of the mold??? I know the rocket guys have this problem. I need to talk to Brent, as I was not there when they rigged the ailerons and flaps, so as far as the rigging technique, I admit my ignorance.
PS, how do your flaps fit re. the fuselage bottom?
Also, Brent, airplanes is an awsome life! Well, ok maybe a legal addiction.

glenmthompson said:

So Randy, Do you think we have issues in the 10 with the tips being out of rig by design or out of the mold??? I know the rocket guys have this problem. I need to talk to Brent, as I was not there when they rigged the ailerons and flaps, so as far as the rigging technique, I admit my ignorance.
PS, how do your flaps fit re. the fuselage bottom?
Also, Brent, airplanes is an awsome life! Well, ok maybe a legal addiction.

Click to expand...

Glen,
with reguard to my earlier post about elevator in trail. If you are holding down elevator (or trim) in cruise flight wouldn't you want to go to a BIGGER shim rather than a thinner one? This wouldn't help the elevator athority problem, but the ballast would help there. It would also improve trim/trailing elev. situation. I believe you need to put the bigger shim back in and ballast to see what you get. The bigger battery suggestion somebody made also makes a lot of sense.
Bill Jepson
Rotary10-RV

Sorry, but nope...

Rotary10-RV said:

Glen,
with reguard to my earlier post about elevator in trail. If you are holding down elevator (or trim) in cruise flight wouldn't you want to go to a BIGGER shim rather than a thinner one? This wouldn't help the elevator athority problem, but the ballast would help there. It would also improve trim/trailing elev. situation. I believe you need to put the bigger shim back in and ballast to see what you get. The bigger battery suggestion somebody made also makes a lot of sense.
Bill Jepson
Rotary10-RV

Click to expand...

Thanks for the suggestion,, but less trim under the front elev spar, equals more full time elevator tail down momentum to help the elevator in the flare.
And believ it or not, that 1/8 inch less of shim only caused a barely noticeable change in the cruise setting of the elevator, while giving us oh, maybe 10 more available flaps with the available trim, full nose up trim.
We have a bigger battery, and Jim is considreing moving the battery further back some time, after for CG exploratoin.
Keep it coming!!!!!!!!!
Glen

Hi folks:

I guess I'll pop in here since I have just logged my first two hours in a locally built RV-10. I'll be on of 2 pilots doing the 40 hour flight test period on this airplane. Currently this -10 has 10 hours total time. 260 hp, Hartzell prop, all Chelton EFIS.. a really nice airplane.

I have flown all the RVs and it certainly is not as peppy as an RV-4. It is just what Van designed it for: a stable, comfortable, cross country airplane. Here are my quick observations in only 2 hours of familarization.

1. Elevator trim position is important for T/O. You have to definitely rotate the airplane. But if one rotates at 60-65 mph, it flies right off and climbs out smartly.

2. Ailerons are heavier that RV pilots are used to. It is a big long wing. I think it flies a lot like a 182 or some similar type airplane. Very stable in turbulence.

3. You do need to trim off elevator pressures. Elevators are heavier than other RVs which is what you would expect.

4. The other test pilot has flown in formation with a RV-6 to compare IAS. While definitive values are not yet available, the IAS seems accurate. If so, I think the airplane will perform as advertised. I had a 170 mph IAS at 3000' msl at 23" and 2350 rpm.

5. Yes, slow flight and stalls are great. Very stable with flaps down. Very gentle stall (power off).

6. Glides very well on approach. Not at all like my 180 hp, C/S RV-4. This airplane can make a power off Cessna-like approach. Reminds me of a big RV-9.

7. I found 80 mph final approach speed just right. You do have a fair amount of up trim in there (with fwd CG), but I had plenty of elevator authority and was able to hold the nose off certainly as well as a RV-7A.

So I'll be learning more as I get more time in this airplane over the next month or so. BTW, this is the 10 that lost its door last Sunday. New hinges and some small fiberglas repairs and all is well. But DOORS-CLOSED and LOCKED is a very important checklist item.

More 10 numbers

Got the following numbers on my last flight day before yesterday:

****600 foot altitude loss with 85 mph simulated takeoff and engine failure. This includes cutting the engine, turning 180 deg, and a simulated flare, all done at 30degs of bank. Obviously this will take more altitude in an emergency with obstruction clearings, the fact that it really is MORE than 180 deg to actually line up on runway, etc...
****500 foot loss per 180 degree turn at 85 mph, flaps up and 30 deg of bank for what it is worth gentlemen.
****With full fuel, 175 lb pilot, and a 30 lb tool box strapped into the rear seat, I can now get level flight at 90 mph, power on, and full nose up trim. This lends credence to those who say weight/cg is definately a big factor here. PS, still BARELY enough elevator to flare without crashing nose gear! Previous ldgs were on grass, these today were the first asphalt ldgs. I had a suspicion that the grass added drag causing the nose to come down fast, but it appears it IS an elevator issue.
**** Noted the following numbers in cruise. 1000 feet, 75 deg, 80% humidity. All numbers were at the above described weight, TAS in MPH per Efis one, and 2300 RPM:
18 in.....136
19 in.....141
20 in.....149
21in......151
22in......158
23in......161

At 2400 RPM, 26 in, 178 MPH TASat 1000 feet.
Will try next run at 2400 RPM and see if these slower speeds are better at a slightly higher RPM for the same MAP.
I gave Jim the owner a hard time because at the 18 in setting, is the speed which my Kitfox flies, and with my Lyc IO290, he is getting a lower fuel flow than me at the same speed! Man, not fair !!! haha
Glen

RV10 speeds

I found it a bit discouraging after reading these reports of RV10 speed.
It seems at least 10 mph slower than advertised numbers based on the reported results of the currently flying 10s. single pilot 26 in 2400 rpm 178 mph TAS does not sound too good. Vic's MT prop RV10 also reported similar results.
Son
flying RV6A....RV10 emp. completed....working on fuse...QB wings ordered

I just got back from LOE today, via Kansas City over the week end. What a great event at LOE, especially once the weather decided to cooperate! It was really great putting names with faces. For those who are interested, The Garmin 430 trip totalizer recorded 2581 nm at an average groundspeed of 171.5 kts. This trip was from Atlanta to LOE, with a stop an overnight in Abilene due to the weather around El Paso, and then on to Kansas City and back to Atlanta. I flew the trip mostly between 10k and 12k feet. WOT and 2360 to 2370 rpm. So, I don't know what all of this noise is about slow RV-10's. Yes, we lucked out and had tailwinds in all directions, and I've never had that happen before! It also included 2 flights with 3 takeoffs and landings while giving rides at LOE. Fuel flow average about 13.5 gph. We came straight back from Kansas City (actually K81, Miami County) all the way home in 3:30, and still had 1:54 fuel remaining. Love the tip tanks!
We now have 142 hours on the airplane. For the 500 or so people working on their kits, keep going. You won't be dissappointed. Yes, there is some noise now about speeds, tunnel heat, doors falling off, etc., but they will all be worked out. Latch the doors before takeoff and do a visual check, and they will stay on. There is absolutely no bowing of these doors in flight at all speeds that I have seen. Remember, all are individually built, so while there might be some minor differences between them due to engines, props, etc, they will propably most likely have somewhat similar characteristics.
Vic

Vic,

Interested in what your tunnel temperatures are like and what you have done there. Also what are you able to true at 8-9000 feet WOT?

Door lights.

rv6ejguy said:

Vic,

Interested in what your tunnel temperatures are like and what you have done there. Also what are you able to true at 8-9000 feet WOT?

Click to expand...

Just got back from Jim's and his #15 RV 10. He just got today in the mail, a door light indicator kit sent from Van's. This was sent from them un-asked for.
Appears to be a very well thought out kit that includes 4 magnetic switches, 2 30 amp relays, wire, 2 panel lights, mounting hardware, and of course directions.
I religously check the doors every takeoff, and have done so even before the door incident on another 10. BUT, this is a mandatory install IMHO. If the door closes with the rear latch outside the door frame, it is a one finger operation to pull the door open, and of course this is not a good thing with 200 MPH of wind passing outside.
Yes I have also observed that the doors are rock solid in flight, absolutely no deformation. I beleive it is pretty much impossible for a properly installed and latched door to come off/open inflight. PLEASE guys, do not worry about the doors, with the warning lights, all will be very safe and secure.

As far as the speeds...well, during the first couple of flights, another test pilot (EAA flight advisor) did an airspeed check with a friend's aircraft at about 160 mph. The speeds were within 1 mph, sooooooo, sorry guys, but at least on #15, unless something drastic happens, this is a 191 MPH plane as it stands. BTW, still need a little tweaking on ailerons (down just a little), need to fare windows in a litttle better when we paint, engine is strong with all compression #'s at or above 74 after 16 hours.
Please, I am not seeing the 211 max speed and 201 cruise speeds that Vans is advertising, at least here. I'd like to invite as many 10 owners as possible to publish what they are getting. Actual numbers, not general cross country WAGS. We all need to learn by this and see why some things are not as they should be.
Parting comment, my best numbers once again are at 8000' 2300 RPM, WOT, 80 deg ROP 191 MPH TAS on a very near standard day. Plane is: Kit built, external vor antenna and 2 VHF antennas on bottom of fuselage. No paint yet, 2 entry steps, 0-540 rebuilt, Vans recommended hartzell 2 blade CS prop, and 35 lbs lighter than Vans plane due to the Efis one's light weight and only seats for interior.
I do not want to worry the new 10 builders nor future builders, cuz I DO LOVE THIS PLANE! But, the real numbers builders are getting should be a matter of public record.
Glen

Please, I am not seeing the 211 max speed and 201 cruise speeds that Vans is advertising, at least here

Click to expand...

Glen, again I'm not trying to pick on you, but the numbers you are seeing are in excellent agreement with Van's advertised claims.

With 260 HP, Van claims 201mph TAS at 75% power and 8000', and 180 TAS at 55% power. You are seeing 191mph true at 65% or so, which is exactly Van's predicted performance.

The 75% number at 8000' is commonly used by aircraft manufacturers because it sounds good, but few people actually operate that way. The Mooney 201 was named "201" because that was the maximum speed it could touch under optimum conditions (I can't recall if it was max cruise or Vmax). Few Mooneys ever saw that speed in the real world, but it was an honest number.

James Freeman

Once again ladies and gentlemen...

How can for example, 211 be an honest number if it is not acheivable? or even 201? Max cruise (ie 211) by my understanding is what the plane should cruise at if you operated like the plane was a rental and you hated the owner, ie wide ass open and leaned to abusive, life robbing power settings. Normal cruise is what we all ( well most) fly to OSH with at 8000' and brag upon arrival that our plane made the vans #'s at xxx fuel flow.

Remember ladies and gentlemen, that of course I can get 75% or so, at arund 7000 or 8000 feet, BUT, this involves turning up the RPM and this makes ANY CS propeller airplane slow down! This plane slows down by 5 mph at WOT and 2700 RPM, or 75% power more or less, as well does any plane. Why, may I ask, do the Reno racers not run at max RPM when racing? Cuz propeller effeciency near supersonic speeds at the tips drops off dramatically. Large bore engines such as these, rely quite a bit on their torque they put out, at least as much as they rely on HP. If you take my little 1.5 liter honda engine, and super charge it up to 260 HP, like some racers have been able to, you will get significantly lower cruise speeds in this plane. Why? Because the torque output will be dramatically lower than our big bores.
Ok, so If these are the speeds that vans is advertising, please give me info on how to achieve them, at ANY altitude. I need power settings and rpms, cuz I have tried them all and I cannot get 201/211 at any altitude or power setting. I have taken the plane to 13,000' and experimented all the way down. If this is truely an "honest number", then I should get at least very close regardless on whether it is a realistic cruise power setting or not.
Vans usually gives good numbers that builders are able to acheive. I am not seeing them. As an engineer by education, I like to deal with numbers. I would very much like cold hard facts on how this plane can acheive the advertised speeds, and not an assumption based on extrapolation as James seems to be indicating.
If we take an EXTREMELY BASIC, simplified assumption of the square of the speed increase is equal to the amount of HP necissary to get that speed, well at the 5 % increase in speed ( we need 10 MPH from 191 to 201, hence 5% increase in speed) this will require 25% more HP! That is 42 more HP to get this extra speed to advertised numbers! (Like I said this is VERY simple only to demonstrate an order of magnitude) Or, this is a GREAT deal of drag reduction to gain that extra 10 MPH.
Its all about the numbers, price, speed fuel flow,TAS etc.... Is that not why we are all RV addicts?
Glen

Cruise speed question

vic syracuse said:

I just got back from LOE today, via Kansas City over the week end. What a great event at LOE, especially once the weather decided to cooperate! It was really great putting names with faces. For those who are interested, The Garmin 430 trip totalizer recorded 2581 nm at an average groundspeed of 171.5 kts. This trip was from Atlanta to LOE, with a stop an overnight in Abilene due to the weather around El Paso, and then on to Kansas City and back to Atlanta. I flew the trip mostly between 10k and 12k feet. WOT and 2360 to 2370 rpm. So, I don't know what all of this noise is about slow RV-10's. Yes, we lucked out and had tailwinds in all directions, and I've never had that happen before! It also included 2 flights with 3 takeoffs and landings while giving rides at LOE. Fuel flow average about 13.5 gph. We came straight back from Kansas City (actually K81, Miami County) all the way home in 3:30, and still had 1:54 fuel remaining. Love the tip tanks!
We now have 142 hours on the airplane. For the 500 or so people working on their kits, keep going. You won't be dissappointed. Yes, there is some noise now about speeds, tunnel heat, doors falling off, etc., but they will all be worked out. Latch the doors before takeoff and do a visual check, and they will stay on. There is absolutely no bowing of these doors in flight at all speeds that I have seen. Remember, all are individually built, so while there might be some minor differences between them due to engines, props, etc, they will propably most likely have somewhat similar characteristics.
Vic

Click to expand...

Like James said to me, I honestly am not picking aither, but Vic, I have a question. You said that you had an average speed of 171.5 K with a tail wind in every direction. Right? Well, assuming calm air and conservatively taking out the wind, you achieved a GS of 197.2 MPH. Still below the vans numbers with a tail wind no less. I realize you were high, but did you get any TAS calcs so I might compare our plane at 12k feet also?

Actually it's the cube of the speed increase but it must be expressed in decimal, ie. 1.05^3 = 1.158 or about 16% more power for 5% more speed (all other things being equal of course).

glenmthompson said:

Like James said to me, I honestly am not picking aither, but Vic, I have a question. You said that you had an average speed of 171.5 K with a tail wind in every direction. Right? Well, assuming calm air and conservatively taking out the wind, you achieved a GS of 197.2 MPH. Still below the vans numbers with a tail wind no less. I realize you were high, but did you get any TAS calcs so I might compare our plane at 12k feet also?

Click to expand...

I thought I had mentioned this before, but it appears that our TAS for our airplane usually sits between 164-168 kts. It is pretty well nailed there. The Chelton constantly displays TAS, so I don't have to calculate it. I have checked it numerous times, and the Chelton calc's appear to be accurate. Yesterday, at 9000' MSL, and WOT and 2360 RPM, I had 168 kts TAS. I haven't seen 200 mph, and don't think we will.

Vic

emember ladies and gentlemen, that of course I can get 75% or so, at arund 7000 or 8000 feet, BUT, this involves turning up the RPM and this makes ANY CS propeller airplane slow down! This plane slows down by 5 mph at WOT and 2700 RPM, or 75% power more or less, as well does any plane.

Click to expand...

Glen, I wonder if something is wrong with your prop. Most of my flying time is behind six-cylinder TCM engines, but in my experience more RPM always means more TAS if all else is equal.

You are right about props losing efficiency as the tips reach high mach numbers, but I have always found this to be more than offset by the increase in available horsepower.

I can't really speak to the larger warbird racers at Reno, as I don't have any direct experience except in the AT6/SNJ, where more RPM definitely means more speed. I have read that the smaller "sport class" racers (e.g. Lancairs, Glasairs. etc.) commonly tweak their prop governors to allow greater than stock RPM for greater horsepower/TAS.

I have posted some small panel photos of my RV-8 here:

http://homepage.mac.com/flyeyes/PhotoAlbum23.html

(I can't apparently attach photos to this forum from a Mac)

In the aircraft I currently fly, RPM is clearly related to speed

James Freeman

The Sport Class Reno guys are running 2700rpm ++ and special props, twin turbos, ADI and spray bar cooling, not much relation to a stock 540 I'm afraid. The turbo Contis don't sound like your father's Oldsmobile.

Speed varies as the cube of the hp.

A 260hp Honda driving a prop through a proper redrive will pull your aircraft at the same speed as a 260hp Lyc. HP is work, torque is force.

It does seem that some people are a bit short on Van's numbers which is unusual. How easy would it be to climb onto the wing without those steps? I was considering leaving mine off for a couple more knots.

Horsepower, Torque, and RPM

Oops just saw that rv6ejguy beat me to the punch, but here goes anyway...

There is a defined relationship between power, torque, and RPM.

Power = Torque * Rotational Rate (i.e. RPM)

This means that if two engines develop the same output shaft horsepower at the same RPM, they necessarily deliver exactly the same torque.

Perhaps the confusion arises when people are talking about engine X with a peak power that occurs at one RPM compared to engine Y with the same peak power, but at a different RPM. In this case the torque at peak power will be different, because the RPM at peak power is different.

There is a duality between torque and power defined by the above relationship. When looking at the physics involved in aircraft performance, you can analyze in terms of torque or you can analyze in terms of power. Certain problems are easier to understand when you use one approach rather than the other. However, it is absolutely incorrect to say that in one flight environment or aircraft the propeller is being driven by torque, and in another it is being driven by power.

Ok...

Alex said:

Oops just saw that rv6ejguy beat me to the punch, but here goes anyway...

There is a defined relationship between power, torque, and RPM.

Power = Torque * Rotational Rate (i.e. RPM)

This means that if two engines develop the same output shaft horsepower at the same RPM, they necessarily deliver exactly the same torque.

Perhaps the confusion arises when people are talking about engine X with a peak power that occurs at one RPM compared to engine Y with the same peak power, but at a different RPM. In this case the torque at peak power will be different, because the RPM at peak power is different.

There is a duality between torque and power defined by the above relationship. When looking at the physics involved in aircraft performance, you can analyze in terms of torque or you can analyze in terms of power. Certain problems are easier to understand when you use one approach rather than the other. However, it is absolutely incorrect to say that in one flight environment or aircraft the propeller is being driven by torque, and in another it is being driven by power.

Click to expand...

Thanks guys, I stand corrected. The cube of the increase in power...Thanks, This Still amounts to way more HP than we can get to get to 201 MPH. Thanks Vic, you are getting 193.2 MPH..A lot closer to our numbers and leads me to believe we have only minor tweaking to goto get to realistic numbers.
Nobody is considering prop efficiency. Why has Jims RV 6, this 10,my Kitfox every otner CS prop plane I have flow, slowed down with a significant increase in RPM? More power, torque, what have you, yes propeller efficiency is the key guys. I think our prop is fine. As well as other planes I have flown.
Glen

I'd agree that prop efficiency is the big unknown. A friend with a -6A Hartzell C/S O-360 and I did a head to head comparison for max speed at 9000 feet. His best TAS and GPS was obtained at slightly less rpm and more pitch.

Other combinations I have seen are fastest at higher rpms and less pitch, presumably because more power is being developed. every airframe, engine, prop combo is slightly different.

If you are pulling the same power setting as Van's, there is a bit of mystery in the speed differences. This aileron rigging issue is interesting. Am I to understand that it is incorrect to rig the ailerons level with the wing tips?

The C177 I fly generally picks up only a knot or two between 2500 and 2700. I'm wondering if the induction system isn't flowing enough air for your engine? Something is a little weird with that setup. If the prop efficency is that close to the edge it may be time to find a better prop. I want to know that I'm getting best power with everything forward, just for emergencies.

Also I know the Lancair at Reno was turning 3200RPM LAST year. I don't know what he was spinning this year, but I'd think it's probably more

glenmthompson said:

Thanks guys, I stand corrected. The cube of the increase in power...Thanks, This Still amounts to way more HP than we can get to get to 201 MPH. Thanks Vic, you are getting 193.2 MPH..A lot closer to our numbers and leads me to believe we have only minor tweaking to goto get to realistic numbers.

Click to expand...

With all of the HP/Speed talk, what about the 10 with the 325HP motor? It would be interesting to hear what kind of numbers he will have. I know it it won't be as much as you might think, but do any of you physics majors know how much of a speed increase you might see?
Thanks,
Mark

>Remember ladies and gentlemen, that of course I can get 75% or so, at arund 7000 or 8000 feet, BUT, this involves turning up the RPM and this makes ANY CS propeller airplane slow down! This plane slows down by 5 mph at WOT and 2700 RPM, or 75% power more or less, as well does any plane.

Click to expand...

Whoa! Where did that generalization come from? This has not been my experience flying CS prop planes. Look at the power charts in the back of Cessna manuals and it clearly shows higher RPM correspond to higher speeds. How much of your 12,000 has been flying behind props? With constant speed or fixed, higher RPM translates into higher power which usually translates into higher speed. The only downside to higher RPM is increased noise and vibration. You throttle back you RPM and you are throttling back your power. Something is definitely wrong if your higher RPM is resulting in slower speed.

w1curtis said:

With constant speed or fixed, higher RPM translates into higher power which usually translates into higher speed....Something is definitely wrong if your higher RPM is resulting in slower speed.

Click to expand...

Not necessarily true. With constant throttle, there is an optimum RPM that produces the highest ratio of thrust:drag. A higher RPM will decrease this ratio so that the prop acts like somewhat of a speed brake.

flyeyes said:

...(I can't apparently attach photos to this forum from a Mac)...

James Freeman

Click to expand...

Actually, James, I don't think anybody can directly attach photos here except maybe Doug.
There is a procedure for getting photos to show up and it involves inserting a link to a site/url that hosts the photo.

I think...

-mike

If you go to this link from another post, it guides you thru posting pics. I am strictly Mac (print shop). On the Mac, I think it lists a link to the photo instead of including it in the post.

How To Insert Images Into Your Posts
------------------------------------------------------------------------
http://www.vansairforce.net/article...rums/images.htm

Derrell
RV7A Finish

Great discussoin guys!

Brian130 said:

Not necessarily true. With constant throttle, there is an optimum RPM that produces the highest ratio of thrust:drag. A higher RPM will decrease this ratio so that the prop acts like somewhat of a speed brake.

Click to expand...

I love all this interaction, we all learn a lot.
I will be very happy to send anybody a short video showing this plane slow down with a change from 2300 2750 RPM at WOT at ANY altitude.

And BTW....PS, I have about 3000 hours flying behind CS propellers. Rest is in Jets. Seen this phenominon happens in every prop plane I have flown.
Glen

glenmthompson said:

I love all this interaction, we all learn a lot.
I will be very happy to send anybody a short video showing this plane slow down with a change from 2300 2750 RPM at WOT at ANY altitude.

Click to expand...

I learned it in practice when I'd be exactly on speed and proud as a peacock in the King Air... and then lose 5-10 kts immediately when I pushed the props full forward on short final. DOH!

I'm curious about this. Do you think the RPM to speed issue is a constant so to speak or could it be dependant on the particular prop/engine. I can't say that I've ever noticed it myself but then again I'm ashamed to admit I never looked close enough. In everything I've flown so far I'd set things according the book and take what I got. I never thought that much to muck with the settings. Then again most of my hours were crawling down the beach pulling signs behind supercubs with FP props and after that dropping jumpers out of turbo props but there it's all up and down so you don't really pay much attention to cruise speed. In fact I have no idea what the Porter would cruise at.

Anyway wouldn't seem logical that you would be able to match prop efficiency to engine output so in a given installation more RPM would give you more speed throughout the usable range of power? I'm not building yet but I'm curious about this none the less.

glenmthompson said:

I love all this interaction, we all learn a lot.
I will be very happy to send anybody a short video showing this plane slow down with a change from 2300 2750 RPM at WOT at ANY altitude.

And BTW....PS, I have about 3000 hours flying behind CS propellers. Rest is in Jets. Seen this phenominon happens in every prop plane I have flown.
Glen

Click to expand...

Glen,
Most, but not all piston engines produce max power short of maximum recomended RPM. You certainly might be turning back to your power peak. I am going to run a Rotary engine in my RV, and they (rotaries) love RPM, so this will probably be the exception to your experience. Provided that the efficiency of your prop is good all the way to Mach 1 your speed should increase with RPM until you exceed the engines max power RPM. So what you are noticing may be true. With a Lyc and the standard camshaft your max power at about 8000' probably ISN'T at max RPM. If you have good ram air or a modified engine things would probably change in a hurry!
Bill Jepson
Rotary10-RV

RPM vs. TAS

OK, I read the post on how to insert photos, so I'll try here:







James Freeman

joe gremlin said:

Anyway wouldn't seem logical that you would be able to match prop efficiency to engine output so in a given installation more RPM would give you more speed throughout the usable range of power?

Click to expand...

If you are seeing an increase in cruise speed at maximum RPM compared to cruise RPM, then you are not optimized for the full range of flight ops. Your maximum RPM (lowest pitch) should give you maximum thrust/drag at low airspeed (takeoff, climb). A lesser RPM (higher pitch) should give you maximum thrust/drag at higher airspeed (cruise).

That's why a fixed climb prop is pitched lower - more thrust/drag at low speeds, but its efficiency suffers at higher speeds.

A fixed cruise prop is pitched higher - more thrust/drag at higher speeds but decreased takeoff performance

It is all dependent on application. Here's a very intense mathematical discussion. http://www.allstar.fiu.edu/aero/BA-Background.htm

Here is an article and excel spreadsheet using that same method that talks about optimizing.
http://naca.larc.nasa.gov/reports/1936/naca-tn-579/naca-tn-579.pdfhttp://naca.larc.nasa.gov/reports/1936/naca-tn-579/
http://www.avweb.com/news/airman/182418-1.html
http://www.avweb.com/newspics/bootstp2.xls

Does that just confuse things further??

Brian130 said:

Does that just confuse things further??

Click to expand...

No that helps. I just never thought about it. Thanks.