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538pg

Member
I wasn't sure where to post this because I want to reach out to all RVer's. I've got a 4 and just recently finished a new strip at my home. It is really pretty smooth, was built of clay and rolled wet. But it is not an asphalt runway. I'm an ag-pilot and I am aware of problems with spring steal gear on rough surfaces. Are there going to be problems with the RV gear, should I replace them every so often, beef up the support areas. I have read post of cracks on the 4's in the mount area's. Just wondering if these harsh conditions have been addressed by others. Any thoughts.
 
Rough strips and RV 4's

RV 4's in particular are prone to firewall damage. It doesn't take that much compared to a,let's say a Cessna 170. The original engine mounts, up until about 1990 were prone to cracking. That problem was rectafied by using heavier sheet metal in the weldament. When an RV4 does a hard landing, lets say 3 g's +, the gear will bend, the engine mount will bend and the firewall will bend, and maybe the prop will hit. As far as crash worthiness this is a good design. As far as making repairs are concerned, the design doesn't help that much. You will find that a lot of flying RV 4's will have a little bent metal on the lower corners of the firewall. Usually you would not need to repair that, just keep it on your inspection list. I have flown my 4 to many unimproved strips in California, Idaho, Oregon, Baja and several other states. The only time I bent anything is when I broke the rules. DON'T ASK WHY I'M SO KNOWLEDGABLE ABOUT BENT METAL.

Steve Barnes "The Builders Coach"
 
Thanks Steve, Don't think I'll be doing any 3 g landings. Was wondering about the weldments on the mount. Has anyone done anyhting to beef up these areas,
 
Alan, I'm also an ag pilot and my buddy has a -4.

As you know, you can grease a wheel landing on more consistently than a three-pointer and that's what I do when I'm flying the -4. If you're the 'best-in-the-world' 3 pointer, then go for it:)

BTW...are you going to be in Savannah next week? If so, PM me your cell and I'll buy you a few.

Best,
 
Thanks Pierre. I tend to wheel land most of the time also. Heck, I didn't even know how to do a 3 point till a few years back. I won't be in Savannah due to surgery on my neck. Seems like wearing that helmet for so many hours has collapsed a couple of discs. I'll run into you somewhere down the road.
 
Ernst,

Mexico has states also! Baja is actually two states (kind of like Carolina and Dakota, or really more like the Virginias).

greg
 
Just to clarify for those not familiar with the RV-4, the engine mount has no problem it is the firewall corner brackets that are mounted to the longerons at the four corners of the firewall that the engine mount bolts to that where deficient and where changed about 1990. I know this is probably what Steve meant but people who don?t know might be lead to miss inspecting there brackets if they did not know where the potential problem lies.

We just changed out the bottom brackets on my dad?s -4 at 900 hours, it?s a big job but he did it in 7 days with a little help from me.

Very hard landings/crashes will cause problems no matter what brackets you have, the new brackets are tougher though. Landing on turf is the hardest normal operation on these parts but the newer brackets will hold up fine on grass. And yes dropping the aircraft 10? will also bend the engine mount, otherwise the -4 is fairly durable but it?s not a Cessna 150.
 
Hard Landings

Russ, the engine mount does bend and was repaired by the manufacturer twice. In 1500 hours I had to rebuild my RV4 twice. The first time was an engine failure into a vineyard. Fire wall bent and replaced, longeron bent and broken, engine mount bent (repaired), gear legs bent (straightened), and had to rebuild internal structure where the two center motor mount bolts were attached, and replaced 4 corner steel engine mounts. The second time was landing on a 1400' uphill strip into rising terrain with a strong tail wind over a row of trees. (Dumb) Prop bent in the turf, gear legs bent, engine mount slightly bent, and gear legs slightly bent. Corner engine mounts OK, and center engine mounts OK. This was on an Island by Vancouver Island B.C.. Two days of field repairs and I was able to ferry it home to California.

Steve Barnes "The Builders Coach"
 
I agree and stated that the engine mount can be bent under extreme landing/crashing conditions, but to answer 538pg?s question it is the fire wall brackets that where changed in 1990 to increase there durability and the old ones can crack out with ought making bad landings or bending the engine mount especially when used on turf and should be inspected every year and any time your in a position to look at them. We also did change the engine mount in the 90s but not to make it stronger but rather to make changes to accommodate the longer gear legs.

Long story short, turf is fine but know what brackets you have and keep an eye on them.
 
Agreed

Russ, There probably a few light engine mounts still out there. When the issue first came up, I was still working on my 4. I went to visit Ed Wischmeyer who was doing a lot of work on a 4 he purchased. His front deck had been removed so I proceeded to inspect his engine mounts by feel. I could actually feel the cracks in the mounts. If memory serves me three were badly cracked. I do not recall seeing any of the typical lower firewall buckling in his four either. Another friend of mine was flying to OSH in the 80's and noticed his prop spinner had dropped significantly. One of the top mounts had nearly seperated.

Steve Barnes
 
Sounds like I need to watch this closely. I bought my 4 and it was first flown in 92. I don't have a builders log or any other info to let me know if I have the beefier mod or not. Can I tell by looking. Comparing photos or something.
Considering the timeline of a build, what are my chances of having it or not.
 
Inspection

Alan, it's pretty easy to do a visual. Take a bright light inside the fuselage and visually check the four corner engine mount from the back side. The cracks are easy to see around the bolt head.

Steve Barnes
 
If the bracket is made out of three bent pieces of sheet metal welded together and is open between the two that come back along the longerons then you have the old ones, the new ones still have the sheet metal triangle that is against the firewall but welded to it is a squairish piece of 1/8” thick plate that the bolt goes thru and welded to those pieces is a bent almost 1/8” plate that comes back along the longerons.

As Steve said these are easy to inspect for cracks and easy to tell witch ones you have, your aircraft completed in 92 could have either the old or new brackets. If you can’t tell just send me a picture and I can help you identify them.
 
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