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Retractable RV-4

pierre smith

Well Known Member
Mornin' all,
My stepson has the local hangar for his A@P/IA business and a friend of mine brought his retractable -4 ,in yesterday because the gear wouldn't retract.

I've seen pictures of this airplane before and now it's housed in my hangar, here at 2J3, in central Georgia. The airplane is 20 years old and the gear looks to me, to have been adapted from an existing airplane.

If you any of you old timers know anything of the origin of this airplane, kindle PM me.

Thanks,
 
Who built it? The only one I am familiar with of the few that where built was built in Hillsboro OR by Dave Lewis Sr.
I know little about the gear set up. At one time, the rib forms for the modifications where sitting on a bench in our hangar. I moved away, Dave passed on, and the forms disappeared.
This was about 25 years ago. At the time, this was the only RV retract. If I recall, it was painted gray, but a bit fuzzy in my memory.
Dave?s opinion was for the little gain in speed, a few knots, and the extra weight and complexity in the build, it wasn?t worth it and no others where built from these forms.
 
Only the mains

It's quite a piece of work. The fuel tanks were moved out around three feet so the gear could have space to retract into. The inboard three feet of leading edge was also swept forward (Like a P-51), ostensibly to create a space for the mains to retract into.

This airplane has an angle valve IO-360/200 HP and cruises near 200 knots..pretty fast and right at or above Van's recommended VNE.

The battery is in the rear baggage area to maintain a correct CG.

Best,
 
Here's some information that has at least some truth to it, and I don't know how much...
* There was a retractable gear RV-4 that landed wheels up at Oshkosh one year (no NTSB report, apparently);
* There was a retractable gear RV-4 under construction in Prescott, AZ that I don't think was built by Dave Lewis;
* One builder's name that turned up was Klaus Roth in Germany. It's in the forums, but the links appear stale;
* Wiki states that there were at least two retractable RV-4s built;
* Kitplanes has a picture of one at Oshkosh with a three bladed prop.

Ed
 
It's quite a piece of work. The fuel tanks were moved out around three feet so the gear could have space to retract into. The inboard three feet of leading edge was also swept forward (Like a P-51), ostensibly to create a space for the mains to retract into.

This airplane has an angle valve IO-360/200 HP and cruises near 200 knots..pretty fast and right at or above Van's recommended VNE.

The battery is in the rear baggage area to maintain a correct CG.

Best,

This sounds like the one Dave Lewis built at HIO, The one Jon also mentioned. There have been several built though so a picture or N number would go a long way toward finding someone who knows anything about it. I believe the one Dave built was Black and silver, his Son, also Dave flew it in to LaCenter View several times back in the early/mid 90s to visit Lee McDaniel when I was working with him.
 
JonJay

I was the one who got the rib forms from Mr. Lewis senior. (a real gentleman).

I have built two RV-4 retracts and know of three others.

Klaus Roth used a completely different gear than the Lewis ones.

The one that did the wheels up at Oshkosh was my first one . I believe it was repaired and is now flying.

Pierre, there is a sensor switch on the mains that will not allow the retraction
unless the oleos are fully extended.
 
Let's add a bit more conjecture to the fire.

The OSH gear-up was four (maybe three - I disremember) AirVentures ago this coming July. It was trailered home to Boise (an odyssey in itself) and repaired. Last year I watched it die on touchdown. The left axle bracket weld to the gear leg failed. The ensuing dig in and twisting damaged just about everything. The aircraft has been scraped.

My friend has sworn off retracts and is building a Glastar.

John Siebold
 
JonJay

I was the one who got the rib forms from Mr. Lewis senior. (a real gentleman).

I have built two RV-4 retracts and know of three others.

Klaus Roth used a completely different gear than the Lewis ones.

The one that did the wheels up at Oshkosh was my first one . I believe it was repaired and is now flying.

Pierre, there is a sensor switch on the mains that will not allow the retraction
unless the oleos are fully extended.

That is fantastic! I assumed they had been ?lost?. Dave was my mentor and friend. Way too many stories to share here about his work as a test pilot for North American during the war, working for Fairchild, saving the F46 prototype which eventually was found again and restored with the help of the pop singer Edwin mcCain, his 14 plus RV builds, on and on.... it?s been some 20 years since his passing and I still think of him often. He taught me so much.
Without him I am not sure I would have ever built an RV.
Anyway, I am glad the forms found a good home and where used to build others. Dave would be thrilled.
 
I'd love my 8 to be an RG but simply not worth the negatives, I'd only do it if I was losing my marbles and my money was annoying me in my pocket:D but man would it look sexy or what?:)
 
Retract 8

Here you go Capt.... This from 2008 RViator.
Apologies to Pierre for thread drift.

f9l26u.jpg
 
no - find a Falco. You won't suffer for speed... or handling.

Tempting, but kinda like buying an EZ type a/c; much harder to know every laminate and joint in a plane where you don't know the builder. I'm actually shopping right now for something sbs to fly until I finish my -7, and I keep looking at the Falcos listed on Barnstormers. Any advice? We can take it off-forum; email me at
[email protected]

Thanks,

Charlie
 
no - find a Falco. You won't suffer for speed... or handling.

I just did a performance comparison between an F8L Falco 180 hp and an RV-7A 180 hp. The Falco is MAYBE 12 mph faster maximum, cruise is the same and the RV stalls about 4 mph slower. Weights are nearly identical.

RV has about half the takeoff and landing distance and a slightly better rate of climb.

The Falco is a beautiful airplane (as is the RV), but I don't think the complexity (retract gear) is justified by the performance.
 
IIRC, the RV-4RG out of Germany was the focus of an EAA article years ago. The builder had built a standard RV-4 and then built an RV-4RG. The RG required full engineering analysis for the German authorities before it could fly. No TLAR engineering. Even the tailwheel retracted, which had to take a lot of work.

Here's the thing, it was something like 80 (or was it 40) pounds heavier and only four knots faster than his fixed gear RV-4.

Hardly worth the effort.
 
IIRC, the RV-4RG out of Germany was the focus of an EAA article years ago. The builder had built a standard RV-4 and then built an RV-4RG. The RG required full engineering analysis for the German authorities before it could fly. No TLAR engineering. Even the tailwheel retracted, which had to take a lot of work.

Here's the thing, it was something like 80 (or was it 40) pounds heavier and only four knots faster than his fixed gear RV-4.

Hardly worth the effort.

Bill,
I remember that article. The RG ended up being over 80 pounds heavier, it took almost a year and a half longer to build, cost about 30% more than the FG, and (as you stated) was only 4 knots faster on the top end. I also remember the builder stating that, while it was an interesting project from an engineering perspective, in the end it wasn't worth the effort and he wouldn't do it again.
 
Charlie - sent you an email off line.

Others: hp for hp, Falco slightly faster [given equal build quality/ finish]; as an AMT i would agree that the complexity is an issue... Newest designs prove out that retraction does not 'pay out' at less than about 250 mph.
Not interested in flames -- 'ya pays yer nickel, ya takes yer choice: not everybody likes coconut'
 
Something like 12lbs on the tailwheel. Might be a factor in the prop strike? :eek: Also, you do know Vne is 212mph?
I know this mod has been discussed, but spar loads, fuel tank moments, etc.
You are definitely a test pilot with this one.
Looks cool though!
 
You are definitely a test pilot with this one.
Looks cool though!

Not to argue your point, my good friend and mentor who built it was a test pilot. He flew P51?s and a host of other models fresh off the production line at the North American Plant in Texas during WWII. The test regimen was one hour. He said very few had any squawks. They where prepped and shipped out. I can?t remember how many he flew in a day but it was impressive, as I recall, four or five.
Although his job was stateside, I still consider him, and all those of ?The Greatest Generation? to be hero?s.

This aircraft has withstood the test of time.
 
Would be sweet but doubt it's got any useful load?
Useful load or max gross is what ever you (the builder) calls it... Experimental. Not saying that is OK, just I have seen arbitrary increase in weights before. These are no longer RV's due to the extensive modification. Not disagreeing but I bet you will find all these planes have higher magical gross weights.
 
Dave Anders does not have a stock air frame.

Skylor
What do you mean by stock. I am no Dave Anders expert but met him once and followed all his work for a long time. First the plane is impeccably built. Air frame has custom cowl, cowl inlets, induction scoop, gear leg fairings, wheel pants, turtle deck mod, wing tips.... and every detail is tweaked for min drag. The basic structure however is stock as far as I know.

Firewall forward it's a masterpiece of engine technology, electronic fuel injection and ignition, tuned exhaust, tuned induction plenums and runners, custom engine build and min drag cooling aerodynamics. Not stock. It is a very light plane (dispute angle valve Lyc). This is just the bigger stuff. A lot of speed and efficiency can be had by many fine details.
 
-4 Mods

What do you mean by stock. I am no Dave Anders expert but met him once and followed all his work for a long time. First the plane is impeccably built. Air frame has custom cowl, cowl inlets, induction scoop, gear leg fairings, wheel pants, turtle deck mod, wing tips.... and every detail is tweaked for min drag. The basic structure however is stock as far as I know.

Firewall forward it's a masterpiece of engine technology, electronic fuel injection and ignition, tuned exhaust, tuned induction plenums and runners, custom engine build and min drag cooling aerodynamics. Not stock. It is a very light plane (dispute angle valve Lyc). This is just the bigger stuff. A lot of speed and efficiency can be had by many fine details.

For starters, it has a counter-balanced rudder which is not stock on -4's. In addition, his fuselage is a fastback which increases stiffness of the tail moment appreciably. I'm sure there are probably other mods that I'm not aware of but these are the two that stood out when I looked at his plane a few years ago.

Skylor
 
The RV4 retract has a similar profile in flight as Ken Rands KR1 RG.

The standard RV4 gear standing still, looks like it's approaching Vr and it's as sexy as gears get. I'd love to get some ACM stick time against this RG -4 with my standard Lyc 0-320 FP.

Now if you want to drool and admire engineering and a fast plane with retracts, check out the "Polen Special".

Cheers, Hans
 
For starters, it has a counter-balanced rudder which is not stock on -4's. In addition, his fuselage is a fastback which increases stiffness of the tail moment appreciably. I'm sure there are probably other mods that I'm not aware of but these are the two that stood out when I looked at his plane a few years ago.

Skylor


For starters? I have a long list of modifications, and you mention two, one of which I mentioned. :D Not an expert but I got the big stuff.

Yes RV-4's don't have counter balanced rudders, but starting with RV-6's Van's started offering counter balanced rudders. Vertical/rudder with balance weight have been retrofitted to many RV-4's, not just Dave's. But good to know, I did not notice it.

I mentioned the turtle deck. Where did I say it did not add strength? I worked as aircraft (stress) structures engineer. Yes it may add strength, but it's a glorified fairing, considering Van's aft fuselage is not weak. It's done for looks and maybe a tad less drag (at the expense of wetted area parasitic drag and weight). Look at Lancair, glider's, most fast planes have very skinny aft fuselages that taper fast aft of the cockpit. Look at P-51D no turtle deck. I've never seen a RV-4 turtle deck modification, but that does not make the wings, vertical or horizontal stab stronger. Over all Dave's RV-4 is "Stock". It's not radically modified as far as I know. I believe the wing is standard span (except for custom wing tips).

You are right there is stuff we don't know about. However Dave is a very generous guy sharing his knowledge, will tell what he has done, especially during cocktail hour before an Oshkosh dinner. :rolleyes:
 
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Now if you want to drool and admire engineering and a fast plane with retracts, check out the "Polen Special". Cheers, Hans
That was a one off built by a corporate pilot I recall. It was sold and never heard of it again. Do you know where it is? I would love to see it in person. Remember seeing it magazines way back when.
 
That was a one off built by a corporate pilot I recall. It was sold and never heard of it again. Do you know where it is? I would love to see it in person. Remember seeing it magazines way back when.

I raced in the Airventure Cup Race 1999 to 2004, most years the Polen Special was in the race, it is now owned by Dick Kyte, and his wife Deb (I hope I spelled his name right) They are both great people, and it is a very fast airplane. I believe he is based in Texas.
 
Tough crowd here...

I guess I'd better keep my project to myself...RG system...supercharged engine...electronic fuel and ignition...turtledeck w/interior mods...tougher empennage...maybe even a fabric rudder...

Oops..:D
 
Yes RV-4's don't have counter balanced rudders, but starting with RV-6's Van's started offering counter balanced rudders.

Not true.

The RV-6 was introduced in 1986 with a vertical stab and rudder that looked very similar to an RV-4 (and had no counterbalanced rudder).

The counterbalanced rudder wasn't introduced to the RV-6 until somewhere around 1998.
It wasn't done because of a perceived need. It was done for parts commonality (for the benefit of reduced parts inventory), and to update the RV-6 kit to benefit from some of the pre-punch advancements that had been made in newer kits.
 
I guess I'd better keep my project to myself...RG system...supercharged engine...electronic fuel and ignition...turtledeck w/interior mods...tougher empennage...maybe even a fabric rudder...

Oops..:D

IIRC, Dave Anders? RV-4 suffered airframe damage from flutter at 270 MPH. It was a wheel pant.

If you think this group is tough, consider the laws of aerodynamics...

:)
 
Not true.

The RV-6 was introduced in 1986 with a vertical stab and rudder that looked very similar to an RV-4 (and had no counterbalanced rudder).

The counterbalanced rudder wasn't introduced to the RV-6 until somewhere around 1998.
It wasn't done because of a perceived need. It was done for parts commonality (for the benefit of reduced parts inventory), and to update the RV-6 kit to benefit from some of the pre-punch advancements that had been made in newer kits.

This is very accurate, I finished my RV6 in 1997 it does't have a counterbalanced rudder, and I don't see a need to change it. Some people do upgrade to the counterbalanced rudder. I don't see a need to. If it ain't broke don't fix it.
 
This is very accurate, I finished my RV6 in 1997 it does't have a counterbalanced rudder, and I don't see a need to change it. Some people do upgrade to the counterbalanced rudder. I don't see a need to. If it ain't broke don't fix it.

They biggest advantage is ease of build.
My RV-6A has the RV-8 vertical stab and counterbalanced rudder because the airplane had been damaged in an accident when I bought it, and it need an all new empenage.
Even though I am an experienced builder, using the P.P. parts made it quite a bit simpler.
Secondary benefit is that it adds just a bit more vertical tail area which in theory would slightly reduce tail wag in turb. I have flown both versions and feel there is that noticeable of a difference.

The down side is that the tail is heavier which can influence baggage utility. My airplane is fine with a fixed pitch metal prop, but I wouldn't be happy with a wood or composite one.
 
Polen

Polen Special is in the Fort Worth area I think Pecan Plantation Airport. There was a second Polen airframe built but it was nene finished. It was for sale in St Augustine, don't know where it is now.
 
Not true.

The RV-6 was introduced in 1986 with a vertical stab and rudder that looked very similar to an RV-4 (and had no counterbalanced rudder).

The counterbalanced rudder wasn't introduced to the RV-6 until somewhere around 1998.
It wasn't done because of a perceived need. It was done for parts commonality (for the benefit of reduced parts inventory), and to update the RV-6 kit to benefit from some of the pre-punch advancements that had been made in newer kits.
Yep you are right. I bought and built a RV-6 kit in late 80's (drill your own holes). I finished and owned a RV-4 and currently a RV-7. The RV-6 did not come with rudder counter balanced. I got confused with my RV-7 (pre-punch) kit which does have balanced rudder. As far as reason one might think flutter. It makes sense that Van would try and make parts common with pre-punch production. A google image search of RV-4's shows some with counter balance other than Dave Anders -4. Cheers

Um, no. Many things not stock.
There is a long list I posted above. However as far as the air frame (primary structure not fairings), except for the turtle deck and rudder balance, it is at the core a stock RV-4. Of course your fantastic SDS electronic FI and E-ignition system is on the engine. Dave's installation of the SDS engine FI + EI on his RV-4 is typical, impeccable. Dave has a series of articles in Kit Plane in the last year, about developing tuned induction. His observation, optimal solution is a variable geometry induction. That would be hard to do. I'm sure Dave is thinking about it. In the meantime he is designing a fixed tuned induction based on well known wave propagation and pressure pulse data, which Cafe Foundation investigated when evaluation different exhaust for a 4-cyl Lyc (4 into 4, 4 into 2, 4 into 1, Y, cross-over). What you do in the exhaust side affects the induction of course, since they both join in the cylinder combustion chamber. There is a limited amount of tweaking you can do with normally aspirated aircraft engines. If you need or want boost you need turbo or super charger. Personally for daily flyer aircraft I'm a fan of simple and reliable, to keep prop turning making thrust.


BACK TO TOPIC, RETRACT....
Mr. Van addressed this in writing years ago why no Retract RV. Fixed gear is light, simple, and only losses a few (handful) of MPH in the up to 200 mph range, with good gear leg fairing and wheel fairings. Many retracts in the retracted position are not perfect and don't get the full drag reduction and the added weight cost speed.

CONS OF RETRACT GEAR:
  • Adds Weight (negating some speed advantage)
  • Complexity
  • Drag in retracted position, if doors not riged perfectly (negating some of the speed advantage)
  • Wheel-up landing possible by accident or malfunction
  • More maintenance

If you are going to go fast, well over 200 MPH retract gear starts to pay for itself, at the expense of all the Cons above.

For people with fixed gear who want retract, I was thinking of developing a fake gear selector. The fake gear switch in the panel would have gear up and gear down locked lights with appropriate timing. When activated you would get a sound affect into intercom of gear retracting, extending and locking. If you forgot to put gear down and it detects a slow airspeed (pressure switch in pitot) you get a gear warning..... :D (This is a joke but some small Part 135 charter airline in the day with a mixed fleet of fixed gear and retracts made all pilots treat all planes like retracts with checklist and verbalizing gear down (and welded). Still to this day I do "GUMPS" and state "Undercarriage" Gear DOWN, in my head.... It is my goal to never have a land gear up or ground loop in my RV. Ha ha. Batting 100 on that goal; don't get complacent.
 
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Anders RV4

Dave Anders RV4 was built in 1991. It had a angle valve 360 with Hartzell two blade constant speed prop. The airframe was structurally stock. I don't remember the year but Dave won Oshkosh Reserve Grand Champion. For several years the airplane was polished.
In 1997 Dave set a new record in the CAFE Triaviathon.
The outstanding Kitplanes series of articles details much of the speed and performance modifications. The only visible structural modifications are the raised turtledeck and counterbalanced rudder.
Recent efforts have been improved efficiency and the Kitplanes articles discuss this in detail.
I have seen a recent picture with a three blade pro-p that appears to be a Whirlwind.
 
Polen Special

For those who mentioned the Polen Special:
It is registered to the Dennis Polen Educational Foundation at Pecan Plantation Airpark, SW of Ft Worth.
Built in 1972
1976 Oshkosh Reserve Grand Champion
2001 500 Km world speed record 307.4 m/h
During the era when the airplane was actively racing the metal rudder fluttered and was totally destroyed. The rudder was replaced with a composite rudder.
The airplane has a parallel valve turbocharged Lycoming 360.
 
For those who mentioned the Polen Special:
It is registered to the Dennis Polen Educational Foundation at Pecan Plantation Airpark, SW of Ft Worth.
Built in 1972
1976 Oshkosh Reserve Grand Champion
2001 500 Km world speed record 307.4 m/h
During the era when the airplane was actively racing the metal rudder fluttered and was totally destroyed. The rudder was replaced with a composite rudder.
The airplane has a parallel valve turbocharged Lycoming 360.
Good summary. Designer Dennis Polen passed in 2008: http://www.vansairforce.com/community/showthread.php?t=27431

This is what we are talking about for those who did not google it.
url


https://www.google.com/url?sa=i&sou...aw3jlYj1gauHgYTyXlsjdHu9&ust=1572817455456443
 
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For people with fixed gear who want retract, I was thinking of developing a fake gear selector. The fake gear switch in the panel would have gear up and gear down locked lights with appropriate timing. When activated you would get a sound affect into intercom of gear retracting, extending and locking. If you forgot to put gear down and it detects a slow airspeed (pressure switch in pitot) you get a gear warning..... :D

Still to this day I do "GUMPS" and state "Undercarriage" Gear DOWN, in my head.... .

Cirrus has stolen your idea, and is now marketing an SR20 ?trainer? which has a gear lever and lights, but otherwise is still a fixed gear. (I too have thought about this. But I would have added an audio feature - if the plane were landed gear handle up, a horrible scrapping noise would come from the speaker/headset!.)

I also still do a full gumpC check, and when I get to ?undercarriage?, I look out at the wing (I learned in a 172RG). Now, in the RV, I can?t see the wheel, but I still look!
 
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