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RV-10 Heavy Stick

T

ten4teg

Well Known Member
I had the opportunity to fly an RV-10 today. On landing, I was surprised by the heavy stick to get the nose up to flare. I had the trim all the way, but the stick was still very heavy. I and the owner were in the front seat. No others. He said that the CG is very far forward with just two people in the front and that he puts 50 pounds in the baggage compartment when he flies it without back seat passangers.

Is this normal? Is this related to the unequal trim travel issue? Also, this RV-10 trues out at 191 MPH. He said it is slower because of the AC condenser on the belly. Any comments?

Thanks
 
RV10

yes to the forward center of gravity

my unpainted RV10 with IO540 and 3 blade MT prop ...TAS 164 kts
 
hey tom. i never told you that the cg was VERY far forward. i said it was forward. call van's and they'll tell you that there rv10 has a fwd cg as well. you need to stay away from that feller who told you that you get wing twist due to the trim tabs. you need to call the source, ie: van's for cg and airflow for scoops. you can call bill over at airflow systems for more input on the scoop. you'll probably find that 191mph tas is great, considering that i do have the a/c scoop on the bottom. i sincerely believe that i'd break the van's 200mph mark if i didn't have the scoop. bill at airflow will argue that point with ya. good luck with your build :) jeff
 
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Hmmmm.....I weigh in at about 170lbs and don't have ANY landing issues with my RV10 when solo and couldn't imagine having to put ANY ballast in the back to fly/land it. It does take all the nose up trim I have but I can fly it all the way to the flare hands off. BTW, this is with full fuel on board or as low as about 15 gallons. Let me add that I shortened my sticks as far as I could to enable full travel with my Infinity Grips and the offset instrument panel (read: no additional leverage). I figure I'm at the 'worst' case scenario unless Olive Oil borrows the plane from me :) .

Normal? I doubt if Van puts ballast in the back of his 10 :). I also don't consider the 'unequal trim travel' an 'issue'....it's part of the design and works fine IMO. Last time I checked (GRT) I saw right at 188tas (that's kts not mph) down low at ~2500'msl. That tells me that Vans numbers are somewhat conservative....a good thing. My plane weighs right at 1618lbs and does not have AC.....as you know, once you start adding weight and extra 'scoops' for AC it's not going to make the plane go any faster.

http://rv6rick.tripod.com/ohiovalleyrvators/id19.html
 
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yea, it was a trip. when i 1st flew the thing. the nose was hard to get up on landing, so i called van's and they told me that their rv10 had a fwd cg and told me that they placed 2 25lb shot bags in the baggage compartment whenever they gave rides in it with no one in the back seats. if you look at the sample cg form from the vans rv10 paper work, it actually shows the cg being about 1/4" fwd of the envelope....empty that is. they actually pointed that out to me in the sample cg form. anyway, it's been nice arguing with ya, hehe. ps- that was a joke:) jeff
 
To be honest with you, I have not found the support at Van's to be forthcoming about issues like this. All they will say is that it must be the builder, ours works fine.
 
Well...keep searching and ASKING RV10 owners that are FLYING. It's apparent that some of them behave differently......surely due to engine/prop combinations as well as battery/ahrs/etc locations.

Not sure if you are buying, building, or dreaming but....find someone who has a combination that you want and see what issues they may or may not have.

http://rv6rick.tripod.com/ohiovalleyrvators/id19.html
 
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FWIW,

When I took my demo ride, Ken took the 50 ln bag of lead out of the back seat so my better half could sit there.....really, a 50 lb bag of lead shot.
 
188 kts RV

When I flew the factory demo plane Ken had 50 lbs of ballast in the back
I weigh 152 lbs. 188 kts TAS.!!!!????...are you sure about that....that is truly amazing ...you have the fastest RV of any model ....you are approaching plastic plane speed...
 
My rv7 does 180 knots tas. At 2500 feet. Flat out. Max rpm and MP, about2700/28. Cant recall fuel burn. I think the 10 should be a bit faster in the same configuration, so 188knots should be doable, maybe?
If it does that in cruise though ,ill eat my VAF cap.
EJ
RV7
 
great points!!!!!!! and i question the rv10 at 188 kts tas as well????? must be in a dive :)
 
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I've seen 185kts TAS at least before. No CG problem on mine but I have
some mid-ship batteries to help, and a larger rear battery. I can hold the nose off the runway for a long long time on rollout, and don't need full trim on landing. The factory -10 is a bit more nose heavy.
Tim
 
Rick's 10 is the fastest buffalo in the heard

I am a little skeptical too. Do you have more HP, James' Holy Cowl, slicker paint? How is it that you can get over 216MPH?

Hank
 
CG Stuff

The Cessna 182S that I flew had the same issue.
Had to remember to hold the nose up with trim when landing.

I am putting my ELT in the tail under the fiberglass empenage fairing to compensate a bit on the CG. Hope the FAA doesn't say No....
 
I added a second battery, put the EFIS/One and some other stuff in the back. I also plan to carry a tool bag when I am not flying three or four people. I also have a little more weight out front than others.
 
Seems to me that this is not a problem. It is going to be difficult on an aircraft of this size and weight to always have it perfectly balanced considering the variable (and considerable) payload capabilities. The issue comes with only one or two pax ie when payload is not critical. Hence a few pounds of ballast in the baggage compartment is neither here nor there. If the balance was out fully loaded and you had to reduce payload to put in ballast, then it WOULD be a problem. Or am I missing something.........
 
paul330 said:
Seems to me that this is not a problem. It is going to be difficult on an aircraft of this size and weight to always have it perfectly balanced considering the variable (and considerable) payload capabilities. The issue comes with only one or two pax ie when payload is not critical. Hence a few pounds of ballast in the baggage compartment is neither here nor there. If the balance was out fully loaded and you had to reduce payload to put in ballast, then it WOULD be a problem. Or am I missing something.........
Click to expand...

It depends if you want to use weight or aerodynamics to balance the plane in flight. To compensate for the forward or aft c.g. you will have to use more elevator to balance the plane which increases drag. Ideally you want the plane to have a neutral elevator position, less drag. The problem is your c.g. will move backwards as you burn off fuel. To plan for the least amount of drag the plane should be perfectly balanced at the midpoint of your flight. You will have to use up elevator trim for the start and ease into neutral trim as you reach the midpoint. Once past the midpoint and going to an aft c.g. you have to use down elevator trim. Keeping the plane out of c.g. balance either way increases the drag, slows your cruise speed and sucks down fuel. You have the choice of adding ballast to neutralize the c.g. or you can **** your fuel and speed away. Obviously this really has no bearing on short trips, except for a heavy stick, but on x-country flights it can make a big difference.
 
A lot less than you think------------

Todd, actually the fuel usage has an surprisingly small effect on the C/G.

The C/G is very far forward in this airfoil, fuel tank C/G is right in the middle of the range. Ahead of the spar. Not the 25--30% MAC most wings use.

Stand out from a wing tip, and take a look at the airfoil from 10' away or so, it reminds me of something I am used to seeing on a R/C flying wing.

Mike
 
Not really

TSwezey said:
. Once past the midpoint and going to an aft c.g. you have to use down elevator trim.
Click to expand...

Todd,
If the CG moves rearward as your flight progresses, the slightly downward elevator actually reduces drag and you'll go faster. Whatever load the tail carries, the wings are relieved of and a lesser angle of attack results, creating less drag as well. Try it sometime...it works...a rearward CG for more speed...within limits, of course.

Regards,
Pierre
 
pierre smith said:
Todd,
If the CG moves rearward as your flight progresses, the slightly downward elevator actually reduces drag and you'll go faster. Whatever load the tail carries, the wings are relieved of and a lesser angle of attack results, creating less drag as well. Try it sometime...it works...a rearward CG for more speed...within limits, of course.

Regards,
Pierre
Click to expand...
Pierre,

I should have also realized (sorry it was early in the morning and I was killing time) as you burn fuel off you don't need as much lift (less weight.) Really it is the loss of weight that increases you speed. The more lift you need the more drag you create. Or in the case of fuel burn the less lift you need the less drag you create (To a point). Speed increases if all other things remain the same only to a point that the thrust of the engine is equal to the drag at the new speed. Sorry it has been 22 years since my last dynamics class.
 
The point is that you simply can't have an aircraft perfectly aerodynamically in trim (ie neutral elevator) under all conditions - it has to be a compromise. Ideally, this would be at a "normal" cruise weight, speed and loading.

In an aircraft of the capability and variable loading of the RV10, this simply isn't possible so there are going to be occasions where trim drag is a factor. However, I refuse to believe it would make a significant difference to consumption/speed.

When it comes to controllability, I stand by what I said - if you have to ballast, it makes sense to design the aircraft so that it is needed at light weights when payload is not a factor. Otherwise you do things like moving the battery aft to compensate and then have an aft CG problem fully loaded - then it's strap a dumbell to the engine mount and ditch the missus's make-up case because you are at MAUW - not popular, I'll warrant.......

The only other way to fix it is either to increase the moment arm by lengthening the fuselage or by using bigger elevators - both of which give you weight/drag penalties IN ALL CONFIGURATIONS.

Of course, there are other solutions. I fly the Airbus A330/340 and that pumps fuel back and forth to the stab tank - might be somewhat advanced engineering for an RV10!! As an aside, the burn penalty if this system is u/s is quoted at 1.5% (a bit less in reality) which brings me back to the effect of trim drag on a light aircraft being negligible.....
 
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paul330 said:
When it comes to controllability, I stand by what I said - if you have to ballast, it makes sense to design the aircraft so that it is needed at light weights when payload is not a factor. Otherwise you do things like moving the battery aft to compensate and then have an aft CG problem fully loaded - then it's strap a dumbell to the engine mount and ditch the missus's make-up case because you are at MAUW - not popular, I'll warrant.......

Of course, there are other solutions. I fly the Airbus A330/340 and that pumps fuel back and forth to the stab tank - might be somewhat advanced engineering for an RV10!!
Click to expand...
I would agree with you 100%. But the fuel tank in the rear would be pretty cool for load balancing!
 
Heck yeah!!

Todd,
You might just have hit on something. Wow, a tank in the back! It'd be so easy to mount behind the baggage area and 50 lbs is a little over 8 gallons for a good 30 minute reserve! You could, with a little plumbing work, pump fuel back there in the event that it was empty and you needed ballast. Who'd a thunk....usable ballast :)

Regards,
Pierre
 
Fuel Ballast

Sorry, Pierre, think I see a fatal flaw in your plan.

The Airbus uses fuel in the stab to control CofG in the cruise - aft CofG = less trim drag = better fuel consumption. All computer and FBW controlled. It all comes forward before descent.

It is bad design to have reserve fuel in a tank not directly feeding the engines. If you have to use a transfer pump to get it forward again, you rely on that pump for your fuel. Also, if you divert or hold and need to burn that fuel, then you are back to the same CofG problem.

5 gallons of water weighs close to 50lb. Fill up a plastic jerry can and load it in the baggage compartment when you need it, empty it when you don't. Simple, cheap, effective CofG control.

Nice try though.
 
And if you use one of the collapsible 5 gal containers, it will not use up an appreciable amount of baggage space.

Mike
 
I woundn't do it.

I would not add any weight in the back of this plane that I could not take out if I was flying four people anywhere. My CG is .75" more aft than 410RV and sure it feels a little nose heavy on landing with only two people up front but it still lands 100% nicer than any Piper or Cessna I have flown. When you put two people in the back and any baggage that nose is just bouncing as you taxi along a bumpy taxiway. On rotation the stick forces to get the nose off the ground go from 5-10 lbs of pull with two people, to .5lbs of pull with four people. And remember, there have been a few of us that have had the plane fall on its tail during loading. The way most of load now is one in the back, and then one on the front, one in the back, then pilot. No more problems. The reason for the falling is that the passengers sit behind the rear wheel and the step is located near the baggage compartment. If you two people step on the step at the same time while two are in the back, it is like having two people in the baggage compartment and two in the rear seats. Now, as you burn fuel (even in 410RV) and you have four people in the plane, you can get outside the rear CG limit.

I never put any lead or anything in the back and have never had a problem. I also have not checked TAS vs. CG.
 
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