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no flaps; heresy or lunacy

delusional

Well Known Member
Yes, I know flaps can be a great convenience, but my question is simply this: If I built my 9 with no flaps, would Vans support it, and how much work would be added and/or saved over the plans?

Please feel free to tell me I'm an idiot, but I'd also love to know if it would be supported.

Since I'm at the fringe already here, why not throw out this one?; With FI and LOP ops practical and even leaner engines possibly on the horizon, do I really "need" two tanks? Wouldn't a much simpler fuel system be an improvement. Up here in the northeast one is never more than minutes from a fuel stop. And my bladder range is not improving lately, either. 4.5 hours seems excessive...

Maybe less really _is_ more, no?
 
Interesting

Richard,

No flaps would save a few lbs. and sure make things less complicated. You would get a "cleaner" wing without the flap brackets hanging in the breaze and the bottum of the wing would be flush. Yo would certainly gain one or two kts. Take off without flaps is fine, but I have not made any non-flap landings yet. Full flaps lower the stall speed and slow her down on final as well.

My tanks hold 200 ltr. (53 gal.). I am not planning on 8 hr. flights, but have you ever been to a fly-in and had to cue-up behind 20 planes for fuel? I can fly there and back without having to fill up in between or even at the destination, before I return. I heard people telling stories about having to wait 2 hrs. at some airfield in France for fuel, because they could not find the keys to the fuel pump!

With two tanks you can run out of fuel twice! Having a tank only in one wing is not an option due to the imbalance. A tank in the fuselage will mean more load on the wings (or you have to carry less passenger and/or luggage).

Regards, Tonny.
 
would Vans support it
Well, in what way do they support any RV? They certainly won't be too enthusiastic/helpful ;)

and how much work would be added and/or saved over the plans?
Added -lots, Saved - none!

Please feel free to tell me I'm an idiot
Wouldn't dream of it, but now you mention it :D

but I'd also love to know if it would be supported
As above, what do you mean by "support"? You'd be on your own, but then isn't that the basis of the US Experimental scene anyway?

do I really "need" two tanks?
No - I suppose you could just build the Left one... or the Right one? I'd think fitting an aileron trim would be a good idea. NB:
  1. Early RV-3s had a fuselage tank.
  2. Where are you going to put your 1 tank? Needs to be near CG fore/aft, and preferably in wing(s) for bending relief.
You would certainly gain one or two kts
Yes - but if you wanted "speed" you'd not be building an RV-9 in the 1st place, but a 7/8 + mod cons. Main thing is why are you building an RV-9? It's characteristics seem less suited to "no flaps" than the others - my limited experience is the **** thing floats so much on landing with flaps, without them it will get very interesting!

Overall my "advice" would be stick to the plans unless you have a really good reason. Flaps and 2 fuel tanks are well proven in most similar designs for good reason/experience. Modifications usually take 3x the time/cost/effort you might think, for 1/3 the benefit :eek: The (very) few exceptions are minor, and well known/discussed on here...

Andy
 
no flaps

I'm in New England too and flying a 9a. No flaps would limit the fields you fly into. One of the great things about the 9 is coming in slow and being able to land on very sort fields. Can't imagine why you would want no flaps.
 
I have taught many no-flap landings...

,,,during transition training other RV builders/buyers, and to a man, they all were very impressed by the simple, plain flaps on the 6 and -7. With no flaps, the airplane is even more difficult to slow down, the over-the-nose visibility is lousy on final and you'll use at least twice the runway. You'll be relegated to the same airports that Long-Eze's and Cirrus pilots have to use...long runways.

Not having two tanks is just beyond me! You can't have a "Both" selector either.....but that's been discussed before.

Best,
 
Anyone who has received training in a 172 must have gone through the scenario of using no flaps to land. The 172 does not want to land and floats down the runway in ground effect for what seems to be a long time and and uses up a lot of runway doing so. An RV-9 will do the same only better because of the low wing position. Unless, a sideslip is employed!

When using the lost art of side slipping, the aeroplane can be made to touch down on any part of the runway that the pilot desires when used effectively. Landing runs will be longer without flaps as there is less aerodynamic drag but with a safe, proper technique landing runs need not be that much longer.

What advantages do flaps give us? Well firstly, flaps increase lift and as more flap is employed, then drag increases. Secondly, the straight and level attitude of the plane is more nose down for the same given aispeed, when flaps are deployed, enabling a better view forward and downwards.

Disadvantages are a slight increase in airframe weight, a more complicated wing structure in the flap area and a slight drag penalty from gaps and dangly bits (dangly bits is a technical term for bits that jutt out in the breeze and confer drag).

Lets look at the issue from another angle. Nearly 7000 RVs of various types have been built and are flying, 99.999% with flaps (Someone somewhere must have built one without flaps). If you decide to build one without flaps, who will want to buy it, should you complete the project and decide to sell it? You will have a more individual aeroplane, but one that will probably have less resale value. An RV was designed to do many aspects of flight very well. Not incorperating flaps into your project will undoubtably reduce the capability of your finished plane. 7000 people cannot be wrong, in this context.

As for tanks. Keep em in the wing and use two as designed. There are very good reasons why two wing tanks are used that have already been dicussed. Fuselage tanks are more dangerous as they are closer to the pilot.

(Just my 2 rappens worth)
 
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Yes, I know flaps can be a great convenience, but my question is simply this: If I built my 9 with no flaps, would Vans support it, and how much work would be added and/or saved over the plans?

Please feel free to tell me I'm an idiot, but I'd also love to know if it would be supported.

Since I'm at the fringe already here, why not throw out this one?; With FI and LOP ops practical and even leaner engines possibly on the horizon, do I really "need" two tanks? Wouldn't a much simpler fuel system be an improvement. Up here in the northeast one is never more than minutes from a fuel stop. And my bladder range is not improving lately, either. 4.5 hours seems excessive...

Maybe less really _is_ more, no?

Why are you asking the question here?

Send your query to www.vansaircraft.com

Beyond that, what is the advantage of a no flap RV? Sure, they will take off and land without flaps but that cuts into the total performance aspects of the airplane very much. Why fly a RV?

Some day your airplane may be up for sale - a no flap RV - really cheap.

If using flaps is against your model, don't use them. Building the airplane without flaps makes not sense at all.
 
An excellent point, David

I will pose the flaps question to Vans.

But at the risk of hijacking my own thread, does anyone have performance tables without flaps? Are slips used routinely in RVs? Any reason a full slip would not be an option to offset the lack of flaps?

I've never heard of a 172 "floating" in any configuration other than the ever-popular "excessive airspeed on final" mode.

Thanks for the feedback, guys. As usual, I will probably just conform to the norm, but it doesn't hurt to ask. I love this forum!
 
I have a -9A and the difference is small between power off stall speeds, with and without flaps is 45 vs 51 respectively. However, the difference in landing is huge. With full flaps, I can fly a nice tight pattern and slow down on final. Without flaps, I pulled the power midfield and fly a bomber pattern and look like a primary student, it takes binoculars to see the runway. I float 1/3 of the way down the runway and all my friends tease me (is it you or the airplane that is afraid of the runway) for not being on speed and stabilized on final. But the more important thing, when you go to sell it, what will be the discounted price for lack of flaps and no cross country range? What will you tell the FSDO inspector when he asks "did you make any major modifications to the airplane or did you build it to plans"? Dan
 
I seldom use full flaps, partial flaps or no flaps. It's always a combination of one of the above. Having that option is great. The RV9 does NOT slip very well. You can't gain a significant amount of rate of descent in a full slip. At least not compared to other aircraft I have flown.

As far as fuel, I have standard tanks and it seems like I always need gas. I wish I had about 10 more gallons. I certainly wouldn't want less.
 
That's good know, Tony. You're saying even with full rudder at approach speed your vs doesn't change much?

Correct. If you have flown a cub, a citabria, or 172, it's easy to get 1500 ft/min rate of descent in a full flap, full fwd slip. I struggle to get 800. The wing is just too efficient at producing lift. If you had a C/S prop that would help (I don't have one). There is just not a lot of surface area in the slip to produce enough drag. I still slip nearly every landing, just don't get the result I have seen in other aircraft.

I would think that a -4, -6, -7 or -8 would be a better candidate for a no flap design. I have flown lots of different airplanes, and still mine is the most challenging to get it to slow down some times.. You have to figure that you might be out cruising around at 135 KIAS and come in to the pattern and have to transition to a 41 KIAS stall speed. That's 94 KIAS of speed management. I don't know of any other airplane with that sort of performance envelop. You will want flaps to help with that.
 
To build without the flaps, you would have to make new skins, top and bottom. You would have to buy additional ribs and then put that darn wedge all allong the trailing edge. While possible, it would be a real pain to do it that way and get a straight trailing edge.

My first plane ('41 T-Craft) didn't have flaps and I've flown a LOT of planes without them, the RV-9 is very clean and no flap landings, while possible tend to have very low shallow approach angles. Slipping it in w/o flaps is easy enough but you can't come in high and slip it down like you can a cub/t-craft/champ/stearman/etc. simply because the thing is so clean.

Also, you will wind up spending a bunch of money on an odd RV and would take a hit on the resale value, if you ever plan on selling it.

As for the single fuel tank idea. 18 gallons isn't enough. You will still need a fuel valve (on-off only), electric and mechanical fuel pumps, this is a low wing after all. All you are adding by building the second tank is the fuel cap, fittings, vent line, and fuel line from the second tank to the left-right-off fuel valve. Oh, if you leave off the second tank, you will have to either make a new skin or patch the hole for the fuel cap that is pre-punched in the skin included in the kit.

One other thought, an O-320 is supposed to burn around 9.6 GPH based on the Lycoming engine manual with higher fuel flows for takeoff power settings. All the low fuel burns you read about are typically at less than 75% power. BTW, you are not supposed to run LOP unless below 65% power.

As for ease of construction, I would think it is MUCH easier to build it per the plans than to make any of these modifications.
 
Without flaps RVs fly at a very high AOA when slow. When I say high I mean you can't see the horizon. Humble opinion: It's a pointless mod with absolutely no advantage.
 
You can do what you want...but

Do you really want to build an aircraft that has less performance than it is capable of with the original design? Usually when someone wants to make a significant change to a proven design they are trying to increase the performance. If you do not have any significant experience landing with and without flaps in an RV I would not recommend building without flaps just on a whim.

From my experience in an RV-6 the flaps are a must to slow down with a fixed pitch prop. It takes a long time to slow down but as soon as I get down to 100 kts and put out even10 degrees of flaps the speed slows down much quicker. Another issue is when trying to fly at 80 to 90 kt into OSH the flaps are needed to lower the nose to a reasonable level.

As to your question about eliminating one fuel tank, are you talking of still leaving the one in one of the wings? If so, don't do it. Fuel on only one side will produce a significant imbalance that will be extremely hard to trim for. Again, stay with the proven design, even with two tanks it is simple, proven and safe.
 
Landing an RV with no flaps is no big deal, I do it most of the time, you just use a lot more runway and you'll be limited to longer runways and have to plan your descent to landing more carefully. Flaps give you a lot more options.

You won't save time or money, maybe a bit of weight. Resale would be less for sure if that is important.

I'd stick with the stock fuel setup too.
 
!no mas!

Okay, you sold me. I had sort of assumed (oops) that slipping could compensate and maybe have the advantage that it can be deployed at a higher speed than Vso. But based on Tony's comments, that seems like a mistake. Like Tony said, lots of designs do real well in slips, but I'm guessing there just isn't enough vertical surface to make the drag needed....

Also, I hadn't thought too much about the forward vis on approach, which is definitely a safety factor.

I think I'll do some more work on figuring out the safest control layout to avoid accidental flap operation. I like the simple, panel-mounted momentary switch and an airspeed inhibitor switch for the down position. I'm very suspicious of the flaps on stick concept, though CWS would be a nice touch if Trutrak or other AP suppliers support it... And maybe a GoAround button by the throttle for raising flaps hands-free and setting the flight director in the missed scenarios...

Thanks to all who posted.
 
if you want to beat to a different drummer why not install a set of spoilers and have some real fun. wham, get that clearance to drop like a rock no problem, full spoilers at cruise speed and down you go. no need to reduce power either. maybe add a little wing and you could turn into a glider too. enjoy the build. RVG-12 coming soon, no flaps.:D
 
Resale would not be so good.....

When it comes time to sell your pride and joy, I would think you'd find a very difficult market for the airplane.
 
There are some designs with just one wing tank. But maybe the relatively short span and light controls conspire against us in this case.

Still it's interesting to consider what we would do if, as in wild fantasies, we had a good engine that burned only 4 gph at normal cruise. Then would you still want eight hours plus of fuel? Hypothetical, I know, but I predict it will eventually come to pass, probably too late to help me out, but maybe some of the younger participants...
 
Tony, how about a cruise descent? Roughtly what sort of vs do you get with descent power clean at the bottom of the yellow with a fp prop?

Sure, spoilers or dive brakes would be cool but now you get into a _real_ engineering project which makes skipping the flaps look like nothing. I'm guessing the smart money would be on maintaining proficiency planning descents...
 
"I think I'll do some more work on figuring out the safest control layout to avoid accidental flap operation. I like the simple, panel-mounted momentary switch and an airspeed inhibitor switch for the down position. I'm very suspicious of the flaps on stick concept, though CWS would be a nice touch if Trutrak or other AP suppliers support it... And maybe a GoAround button by the throttle for raising flaps hands-free and setting the flight director in the missed scenarios..."




Go for mechanical flaps and there will be no accidental flap operation.
 
I can't believe this thread has gone on this long. I miss the old VAF of a few years ago, the one that had useful and meaningful threads.
I want that old forum back, this one seems to be devolving into "idiocy", "lunacy", and "delusions"! Jeez!
 
I can't believe this thread has gone on this long. I miss the old VAF of a few years ago, the one that had useful and meaningful threads.
I want that old forum back, this one seems to be devolving into "idiocy", "lunacy", and "delusions"! Jeez!

Hey Jon - I thought you were minding the store while the rest of us were at LOE....;)
 
What a relief!

I can't believe this thread has gone on this long. I miss the old VAF of a few years ago, the one that had useful and meaningful threads.
I want that old forum back, this one seems to be devolving into "idiocy", "lunacy", and "delusions"! Jeez!

Phew! I feel better, I thought I was turning into a curmudgeon. :rolleyes:

John Clark ATP, CFI
FAA FAAST Team Member
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
 
AMEN again to last few messages....

Richard may well be building the wrong airplane.

I noticed he learned to fly in cubs and his questions go back to that type of flying. He apparently misses it.

On face value, the thread is delusional and a challenge to respond to in civil terms, if responding at all is appropriate. To modify a great flying airplane to piper cub characteristics is mental anguish to say the least.

Maybe the answer for Richard is sell the 9 tail kit and build what he really wants.
 
BTW, you are not supposed to run LOP unless below 65% power.


Not really the point of this thread, but this is not accurate. You want to avoid peak EGT's unless below 65%. LOP operation can be safely done at higher power settings so long as you are lean enough to stay out of the "Red Box" where detonation can occur, which is centered on peak EGT and extending both lean and rich of that point to a certain range, depending on power setting. The idea of LOP only below 65% is based on the fact that you can't hurt your engine with ANY mixture setting at or below 65% power. Above 65% power you CAN do damage if you don't lean it correctly.
 
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There are some designs with just one wing tank. But maybe the relatively short span and light controls conspire against us in this case.

Still it's interesting to consider what we would do if, as in wild fantasies, we had a good engine that burned only 4 gph at normal cruise. Then would you still want eight hours plus of fuel? Hypothetical, I know, but I predict it will eventually come to pass, probably too late to help me out, but maybe some of the younger participants...

Sounds like you'd really rather be building an RV-12.
 
I think I'll do some more work on figuring out the safest control layout to avoid accidental flap operation. I like the simple, panel-mounted momentary switch and an airspeed inhibitor switch for the down position. I'm very suspicious of the flaps on stick concept, though CWS would be a nice touch if Trutrak or other AP suppliers support it... And maybe a GoAround button by the throttle for raising flaps hands-free and setting the flight director in the missed scenarios...

Thanks to all who posted.

Not to sound like an ***... but:

Why in the world would you retract that flaps on a go around? Maybe once you've established a stable climb, and are safely away from whatever situation caused the go around, but to retract them automatically at full power is setting yourself up for failure in a big way. It's an RV, not an airliner. You don't retract the flaps upon commencing a go-around, slow and low to the ground. In anything. (Multi engine a/c experiencing and engine failure not withstanding.)

As far as speed brakes/spoilers/whatever idea... why would you do this either? You planning on staying high as long as possible and shooting a hi-approach? You'll shock cool your engine to death. I actually have a GIANT speed brake, and we don't even do this flying fighters. Speed brake accuation is a result of poor decent planning and a waste of fuel. (Unless shooting a hi-approach). I plan my decent as close as I'm able to provide an idle power C/Lmax decent to maximize every bit of gas I have.

As far as landing a 9 with no flaps, all the time... I can only relate to my -6 experience. While you CAN do it, why would you? You're landing speeds are faster, attitude is flatter, for a tail dragger you'll have a higher risk of nosing over if you find yourself needing to stop quickly, go around capability is reduced, runway requirements are longer, and you'll eat up brakes and tires a lot faster.
 
Easy, on delusional. He has honest questions and ideas. I don't thick we need to burn him at the stake.
 
Easy, on delusional. He has honest questions and ideas. I don't thick we need to burn him at the stake.

But it's been so LONG since we had a good beating!

I think the last really good one was a few years back when I got my head handed to me for asking about liquid engine cooling using the wing skin as a radiator...:(
 
But it's been so LONG since we had a good beating!

I think the last really good one was a few years back when I got my head handed to me for asking about liquid engine cooling using the wing skin as a radiator...:(

LOL! Yep, I remember that one. I am pretty sure you got whipped really good for that one.
 
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Not to sound like an ***... but:

Why in the world would you retract that flaps on a go around? Maybe once you've established a stable climb, and are safely away from whatever situation caused the go around, but to retract them automatically at full power is setting yourself up for failure in a big way. It's an RV, not an airliner. You don't retract the flaps upon commencing a go-around, slow and low to the ground. In anything. (Multi engine a/c experiencing and engine failure not withstanding.)...

I wouldn't dream of raising the flaps without establishing a positive climb rate, naturally. And just as with the airspeed interlock for down, why not another inhibitor based upon vertical speed and airspeed when in go-around mode. Workload can be reduced nowadays using cockpit automation to help with various critical phases of flight. We have altitude capture and can even fly holds on autopilot. I haven't heard of auto-braking in light singles yet, but maybe in some real fast and bigger ones it would be practical, just as for the airlines. For single-pilot IFR ops, any way to reduce workload should be examined, at least. Why not set flaps to "auto-down" when you full brief the approach and then as you decelerate nearing the glide path, get an annunciation "flaps down in 5 seconds", and concentrate on flying the airplane to intercept. Ditto for the go-around.

Let the FMS know what you plan to do and let it free your hands by flipping some switches for you at the appropriate time, informing you of these actions, like a good FO. Even professional pilots need to focus more on flying the airplane, and having to flip lots of levers when you are already very busy does not help.

Personally, I take no offense at the debate and in the case of a go-around, I normally hedge the issue by using minimal flaps on approach, which of course is easy for me to say since I fly spam cans and a three degree path can be easily done under most such circumstances with no flaps at all, leaving you in a good configuration for a go-around. Of course there are exceptions, but I've gone on enough for now...
 
Anyone who has received training in a 172 must have gone through the scenario of using no flaps to land. The 172 does not want to land and floats down the runway in ground effect for what seems to be a long time and and uses up a lot of runway doing so. An RV-9 will do the same only better because of the low wing position. Unless, a sideslip is employed!

When using the lost art of side slipping, the aeroplane can be made to touch down on any part of the runway that the pilot desires when used effectively. Landing runs will be longer without flaps as there is less aerodynamic drag but with a safe, proper technique landing runs need not be that much longer.

What advantages do flaps give us? Well firstly, flaps increase lift and as more flap is employed, then drag increases. Secondly, the straight and level attitude of the plane is more nose down for the same given aispeed, when flaps are deployed, enabling a better view forward and downwards.

Disadvantages are a slight increase in airframe weight, a more complicated wing structure in the flap area and a slight drag penalty from gaps and dangly bits (dangly bits is a technical term for bits that jutt out in the breeze and confer drag).

Lets look at the issue from another angle. Nearly 7000 RVs of various types have been built and are flying, 99.999% with flaps (Someone somewhere must have built one without flaps). If you decide to build one without flaps, who will want to buy it, should you complete the project and decide to sell it? You will have a more individual aeroplane, but one that will probably have less resale value. An RV was designed to do many aspects of flight very well. Not incorperating flaps into your project will undoubtably reduce the capability of your finished plane. 7000 people cannot be wrong, in this context.

As for tanks. Keep em in the wing and use two as designed. There are very good reasons why two wing tanks are used that have already been dicussed. Fuselage tanks are more dangerous as they are closer to the pilot.

(Just my 2 rappens worth)

I dont entirely agree that a 172 or any plane floats for ever. I think its more a function of too much speed to bleed off at landing. My 7 floats quite a way when I carry too much speed with flaps. I have often landed with little or no flaps when expediting at a large airport and no more float than usual. Just my 2c .
I wouldnt ruin the 9 by making it flapless. Trying to resell one day will be a bear. Kinda like selling a RV with a non Lyco type engine.
 
well, actually...

...what he really wants.

Hah. We could start a whole section. Gimme a Citation X, a Twin Otter, a Super Cub, and an RV-3.

But then, life is full of compromises. I think the 9 is a real good compromise, especially when economics are considered, as they must be... My garage is ample for a 9, but I don't think even one wing section of a Twin Otter would fit...

But, please continue trying to dissuade me; it's inspirational.
 
And just as with the airspeed interlock for down, why not another inhibitor based upon vertical speed and airspeed when in go-around mode. Workload can be reduced nowadays using cockpit automation to help with various critical phases of flight. We have altitude capture and can even fly holds on autopilot. For single-pilot IFR ops, any way to reduce workload should be examined, at least. Why not set flaps to "auto-down" when you full brief the approach and then as you decelerate nearing the glide path, get an annunciation "flaps down in 5 seconds", and concentrate on flying the airplane to intercept. Ditto for the go-around.

Let the FMS know what you plan to do and let it free your hands by flipping some switches for you at the appropriate time, informing you of these actions, like a good FO. Even professional pilots need to focus more on flying the airplane, and having to flip lots of levers when you are already very busy does not help.

Airspeed interlocks, inhibitors, go around mode, flight directors, flaps "auto-down", FMS... huh? Are you building an Airbus or an RV?? It's an RV, a simple airplane, why spam it up with all that extra unnecessary stuff? Put the flaps on it, put a toggle switch on the panel (near the throttle), and go fly it. It ain't rocket science, it's an RV... I fly a 737 for a living and my RV-8 for fun, and IMHO there's just no need for all that extra junk. Just fly the plane.
 
I already surrendered above, but...

Airspeed interlocks, inhibitors, go around mode, flight directors, flaps "auto-down", FMS... huh? Are you building an Airbus or an RV?? It's an RV, a simple airplane....


That sounds like good advice. I'l keep it simple. No unnecessary systems to get into trouble with (well, okay, maybe flaps and a good AP ;) ). Once it flies, maybe I'll decide to build wings with no flaps, but then I can do it with more experience, perspective, and more scrap materials, like the stabilizer spars which now make passable shelves for small jars of rivets since I countersanked the wrong side...

Recreation and education, indeed....
 
Two Tank Requirement...

Since I'm at the fringe already here, why not throw out this one?; With FI and LOP ops practical and even leaner engines possibly on the horizon, do I really "need" two tanks? QUOTE]

Two points to make here: a). Just remember that experimentals seem to have about the same accident rate as certified aircraft when it comes to "fuel mismanagement"...about 30-35% I believe; so if you just keep plenty of fuel onboard the aircraft you will have eliminated about 1/3 of the risk of flying.

b). As the old aviation saying goes..."the only time you have too much fuel is when your on fire!"...nuff said! :)

Blue skies...

Doug Lomheim
RV-9A
OK City, OK
 
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