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Damage to foot box? RV4

https://photos.app.goo.gl/GiAoq4tirNHzbrAg2


This is some damage from a previous accident 25+ years ago that is left on an RV4 I'm looking at. The owner claims this area is non structural and it passes air worthiness. What say you RV experts? The wings were replaced at the time of the accident so I have to question why this was not repaired even IF its non structural and deemed air worthy.

Thanks!
 
Pretty common.

There are lots of threads on this, some fairly recent. Early -4's have a weaker weldment at the lower forward longeron where it attaches to the firewall, and later models have a large gusset. This can be upgraded, and many -4's have wrinkles (like yours) or repairs to the firewall/footwell. The firewall itself is not significantly structural, but the longeron connection is. Search the forums and you will see others remedies. Based on your where your located, there is a gentleman with an RV repair/build shop at Raliegh Executive KTTA I recently visited that may be able to guide you on your particular questions. Hopefully, you get this plane and enjoy it..several -4's in NC, 2 at my airport. Come see us at 8A7.
 
Bill, Thank you for the fast response. Per your recommendation I did a quick search to look at some of the older threads regarding the footwell/firewall. I feel based on what I've seen out there that I'll probably pass on this airplane. They want fairly top dollar for the aircraft and with previous damage history etc I'm worried about what might be hiding underneath. I just cannot understand why the previous owners would not have addressed and fixed this even if it's purely cosmetic. I guess that's the difference between air worthy by the books and air worthy in my own opinion. I feel like for 50 thousand dollars there is a much better candidate out there, just gotta wait for it.
 
Bent!

Damage unrepaired takes away from the value. Damage repaired takes away value too!
 
firewall wrinkle

My RV-4 developed a wrinkle such as the one in your photo (but on the starboard side) at about the 3hr mark (I think as a result of a hard landing)...:-( I was concerned at first but now have 750hrs on the plane. There has been absolutely no adverse effect to the structure......it just looks kinda ugly. The plan is to fix it up when the engine comes off for a rebuild one of these days...
 
Bill, Thank you for the fast response. Per your recommendation I did a quick search to look at some of the older threads regarding the footwell/firewall. I feel based on what I've seen out there that I'll probably pass on this airplane. They want fairly top dollar for the aircraft and with previous damage history etc I'm worried about what might be hiding underneath. I just cannot understand why the previous owners would not have addressed and fixed this even if it's purely cosmetic. I guess that's the difference between air worthy by the books and air worthy in my own opinion. I feel like for 50 thousand dollars there is a much better candidate out there, just gotta wait for it.

Damage unrepaired takes away from the value. Damage repaired takes away value too!

Agree with both. There are nice airplanes out there for better prices. Unfortunately not able to point you to one. I have another friend that has been looking for an RV-4 180 CS for two years now that is in great shape and a good price.
 
https://photos.app.goo.gl/GiAoq4tirNHzbrAg2


This is some damage from a previous accident 25+ years ago that is left on an RV4 I'm looking at. The owner claims this area is non structural and it passes air worthiness. What say you RV experts? The wings were replaced at the time of the accident so I have to question why this was not repaired even IF its non structural and deemed air worthy.
For my money, if the price was reasonable, this wouldn't deter me from buying it. Here's why: It has flown 20+ years like this, presumably without incident. It is passed as airworthy. Other than you, no one would ever know about it, ,it isn't structural and finally, if it was my RV-4, I wouldn't bother with it, for each of these reasons.

As to why it hasn't been repaired, that would presumably involve removing the engine, a not-insignificant task for something that does not render the plane unairworthy.

I have several faux-pas on my -9, the worst a ding on the underside of the left elevator where I was back-rivetting and went off the end of the plate on the last rivet. It's still flying, and on my 'to monitor' list, but I am not going to replace the elevator just because of this ding that no one can see. By the same token, I am not going to replace the aft deck skin just because I dinged it on one of the very last rivets I was setting there.

Each one of those little imperfections is a result of a screwup on my behalf to be sure, but they are also a reminder that, though the plane is not perfect (indeed, far from it) it is mine, and something to be proud of. The same for this -4, for whoever ends up buying it, a bloke built it in his back shed, and here we are, nearly 30 years since it was introduced, and you still can't buy an equivalent factory-built plane.
 
Previous Discussion

This type of deformation is fairly common in RV-4's and is typocally the result of a hard landing. The firewall is non-structural, so if there is no other damage to the mount, gear legs or airframe (including the weldments at the forward end of the fuselage longerons) replacing the lower firewall is optional. Even without visible deformation, you may find cracking of the firewall in the lower corners, depending on how the firewall was originally installed. This type of cracking may or may not be visible with the engine mount attached to the firewall.

Here are some previous discussions that might clarify this:

http://www.vansairforce.com/community/showthread.php?t=100765&highlight=firewall+wrinkle

http://www.vansairforce.com/community/showthread.php?t=154654&highlight=firewall+wrinkle

http://www.vansairforce.com/community/showthread.php?t=100765&highlight=firewall+wrinkle

http://www.vansairforce.com/community/showthread.php?t=50838&highlight=firewall+damage

http://www.vansairforce.com/community/showthread.php?t=28481&highlight=firewall+damage

http://www.vansairforce.com/community/showthread.php?t=13342&highlight=firewall+damage

I purchased a previously flying airplane and replaced the lower firewall on mine several years ago; but only when I removed the engine for overhaul. If you do replace the firewall, it helps to compress the new stainless with bolts and fender washers before drilling and riveting the lower portion in place--this "pre-load" helps mitigate future cracking. If you do have any small cracks, they should be sealed properly (high temp silicone, etc.).

Another resource are the great folks working in Van's Tech Support--an email with a photo or two will always elicit sound advice...those folks are the RV experts.

A search will also turn up plenty of discussion regarding the forward fuselage/longeron weldments, engine mount cracking, uneven wing tip height and other topics that folks run into when they buy a used RV-4.

RV-4's are great airplanes!

Best of luck,

Vac
 
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I believe there will be a very nice (O-320) coming up in Fredericksburg, VA very soon.
Built by an A & P, nice clean machine. Don't know the price, but reasonable.

PM me if you want more details.
Daddyman
 
The damage is from a significant ground loop after a hard landing. The wings were replaced. It was 20+ years ago. If he and I can agree on a price I'm still strongly considering the airplane.
 
What is flexing to cause this to happen. Until that is resolved this deformation will occur again.

There was a design change of the steel weldment in the four corners of the firewall longeron attachment located in the cockpit. (Wd-402L, Wd-402R, Wd-403L, and Wd-403R) It deals with early RV-4s. Later kits were shipped with an improved part. I thought there was a SB for it but cannot find it. The change was published in the early RVators. If you really want to know more, I will dig through my early paper copies of the RVator and email it to you.

Google search found this.


"Engine Mount Bracket Reinforcement"
"[1988]"
"Several RV-4 pilots have reported cracking failure of the engine mount brackets (WD-402 & 403) in the forward fuselage. Usually this has resulted from continued operation from rough airstrips or one or more extremely hard landings. Regardless, these brackets seem to be the structural Achilles Heel of the RV-4 airframe."
"Some time ago, we altered the bracket design by increasing the thickness of the attachment arms from .050 to .065". However, many RV-4s now flying have the .050 brackets. We have developed a couple of relatively simple mods which can be added during or after construction."
 
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There was a design change of the steel weldment in the four corners of the firewall longeron attachment located in the cockpit. (Wd-402L, Wd-402R, Wd-403L, and Wd-403R) It deals with early RV-4s. Later kits were shipped with an improved part. I thought there was a SB for it but cannot find it. The change was published in the early RVators. If you really want to know more, I will dig through my early paper copies of the RVator and email it to you.

Google search found this.


"Engine Mount Bracket Reinforcement"
"[1988]"
"Several RV-4 pilots have reported cracking failure of the engine mount brackets (WD-402 & 403) in the forward fuselage. Usually this has resulted from continued operation from rough airstrips or one or more extremely hard landings. Regardless, these brackets seem to be the structural Achilles Heel of the RV-4 airframe."
"Some time ago, we altered the bracket design by increasing the thickness of the attachment arms from .050 to .065". However, many RV-4s now flying have the .050 brackets. We have developed a couple of relatively simple mods which can be added during or after construction."


As mentioned in the previous posts the original poster is asking about the footwell deformation which is NOT a weldment crack. This is a deformation of the stainless footwell due to a hard landing (or ground loop) which is a different issue. If the price and craftsmanship are right and there are no other signs of damage around the gear intersection, motor mount and no weldment cracks then buy it and fly it!
 
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Footwell

See the other post on this page entitled Firewall wrinkle. I think it's important to squash the heavy landing/grounloop theory. It could cause the problem, but I had the cracks without either. It's a structural design problem, which can be cured, I hope, with gussets to brace the 3/4 x 3/4 verticals as per the RV7. Very complex loads in those front corners and not enough rigidity. Build accuracy helps too.
 
Hey guys. New RV-4 owner. Just closed last week. Was trying to track down a nuisance oil leak last night and found slight deformation to the firewall in the bottom left and right corner. After further inspection I realized the firewall is actually cracked underneath the plane just infront of the rivet attachments. Is this an airworthiness concern, or just a blemish to an otherwise decent airframe? Don't want to pull the engine without serious need. Thanks
 
Are the aluminum angles around the firewall 'straight', and the steel weldments inside the fuselage + the motor mount crack free? If so, the only danger is CO entering the cockpit if the cracks allow exhaust gasses to come in.

I had a hard landing several years ago on my purchased (2002) 1991 -4, and when I pulled the engine to do the prop strike AD, I found some firewall wrinkles, and cracks that were obviously very old (they got extended slightly by my incident). The plane always flew fine before my incident, and flies fine now.

Charlie
 
Thanks Charlie. Everything looks good... engine mount welds, attach points inside, etc, at least to my untrained eye. The crack is underneath where the firewall wraps under and is riveted to the fuselage. I was thinking about having someone more skilled than me bend and rivet in a doubler to cover the crack and reinforce it. I have a theory I haven?t found online about the light bends in the firewall foot well... when I move the rudder pedals my heel can hit the firewall if I?m not paying attention. I wonder how many have bent their firewall taxiing or spinning at full deflection? Just a theory. Seems like a thin piece of metal.
 
Thanks Charlie. Everything looks good... engine mount welds, attach points inside, etc, at least to my untrained eye. The crack is underneath where the firewall wraps under and is riveted to the fuselage. I was thinking about having someone more skilled than me bend and rivet in a doubler to cover the crack and reinforce it. I have a theory I haven?t found online about the light bends in the firewall foot well... when I move the rudder pedals my heel can hit the firewall if I?m not paying attention. I wonder how many have bent their firewall taxiing or spinning at full deflection? Just a theory. Seems like a thin piece of metal.

When you say the crack is 'under' I'm picturing bottom skin aluminum rather than stainless steel firewall. Can you help with a picture?

Congrats on your new RV4 and grin!

Stan
 
Firewall cracking in the lower corners is common in the RV-4. As Stan said, there are complex loads there during takeoff, landing and ground operations. The stainless is hardest material in a matrix that flexes during operation, especially in the event of hard landing. A wrinkle in the firewall may result in the event of a hard landing, but cracks in the lower corners may appear during general use as there is still flexing occurring, which causes the stainless to fatigue and crack.

My -4 had slight wrinkling and cracks when I purchased it. I replaced the lower firewall when the engine was removed for overhaul, and haven't had any subsequent wrinkling, but the lower corner has cracked. As a matter of fact, the new firewall cracked almost immediately, but stop drilled and sealed, it hasn't progressed in the subsequent 600 hours.

As I fly off a grass strip, I'm careful to also frequently check the weldments for cracking around the gear sockets and lower firewall attach points, and had to re-weld the gusset at the left socket at the 1200 hour point.

Enjoy the new airplane!

Cheers,

Vac
 
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