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Roger Moore
10-13-2005, 08:42 PM
For those of you currently flying the RV4 please check your aft gusett/weldments on upper engine mounts. In my annual airworthyness inspection I found both left and right cracked. I have a new xp360 on the aircraft with 105 hours on it and had approx 400 hours on an 0-320 prior to that for a total of 500 hour on the aircraft. Vans says they have never had this problem with the upper mounts onlu on the lower of early aircraft. I do aerobatics regularly but generally pull 3 g's or less in all manuvers. The most I have ever pulled is 5 g's on one ocassion. My flying backround is 26000 hours total with 500 in RV4's and 2000 tailwheel so I do not fatigue is pilot induced. Vans Aircraft is very intrested in this and I will follow up. Roger Moore

andrsnj
10-14-2005, 11:17 PM
I wrote a reply yesterday but I don't see it so here it is again. I am wondering exactly where the cracks are. Are they in the flat part of the mount where the engine mount bolt goes through? I have already installed my brackets but if there is some way I can make them stronger now to avoid a problem when I start flying then I want to do that. I know that there was a redesign of these brackets at some point but I'm not sure what was done to make them stronger. My brackets have doubler plates where the engine bolt goes through, does yours? If you could explain where the crack is then I could get a better idea about the stresses that caused it. I was also under the impression that most of these bracket failures ocurred on the lower brackets and that the landing gear was part of the issue. I can remember watching an early RV4 taxiing down the runway and the wheels were oscilating back and forth, front to rear, which I'm sure must have stressed out something.

gmcjetpilot
10-15-2005, 06:11 PM
I had a RV-4 and never had the cracking problems, but at my air-field we had about 10-15 RV's at one time or another, most RV-4's. Two RV-4's developed the cracks on the lower mount attach fittings. These planes where used in mostly for aerobatics, dog-fighting and formation flying. They all had 180hp c/s props.

I also never heard of the upper ones cracking. I can't give you more info. Van did change the design of the lower ones for sure but don't recall if there was a design change to the upper ones.

The repair involved removing the engine mount with engine still attached. Drill out the mounts and install new ones (easier said than done). Sorry I can't help or lend a hand, but at least there is a data point or two. G

Wicked Stick
10-16-2005, 07:43 PM
For those of you currently flying the RV4 please check your aft gusett/weldments on upper engine mounts. In my annual airworthyness inspection I found both left and right cracked. I have a new xp360 on the aircraft with 105 hours on it and had approx 400 hours on an 0-320 prior to that for a total of 500 hour on the aircraft. Vans says they have never had this problem with the upper mounts onlu on the lower of early aircraft. I do aerobatics regularly but generally pull 3 g's or less in all manuvers. The most I have ever pulled is 5 g's on one ocassion. My flying backround is 26000 hours total with 500 in RV4's and 2000 tailwheel so I do not fatigue is pilot induced. Vans Aircraft is very intrested in this and I will follow up. Roger Moore

Roger,

If possible, please take and post a picture of the cracks so we can better see where it is cracking. I think a picture would be very beneficial for everyone who owns and flys an RV4.

Roger Moore
10-17-2005, 05:54 PM
Guys and gals I have talked and sent pictures of my weldment breakage to Van's and they say this is the first case of upper weldment breakage. We found them after finding a small crack in the firewall so they would not have been noticed on preflight. both sides were broken clear through the bolt hole. I have a friend with a lab so the welments will be completely through microscope. Vans reps feel they were started as cracks which eventually resulted in complete breakage. Again this aircraft has never had a "Bad Landing" and was never over stressed. Roger Moore RV4DRVR@aol.com

Roger Moore
10-19-2005, 03:54 PM
Just talked to Vans and they said there was a service bulletin out in 1989 or 1990 to add a doubler on the upper weldments of the RV4. My aircraft did not have this doubler. I have also found cracks in the lower firewall. So at this point both upper weldment which Vans say are much more substantial and total firewall replacement. I recommend if your RV4 does not have the doubler on the upper mounts that you inspect carefully. Roger Moore RV4DRVR@aol.com

Roger Moore
10-28-2005, 05:30 PM
In my prior post I said the service bulletin advised on a doubler on the upper mounts, this was incorrect the bulletin advised a doueler in the lower mounts. I currently have my airplane apart and can compare the pre 1988 weldment to the new ones and I can say the early ones are very flimsy. They went from .050 to .065 sizes and significantly beefed up the structure. My aircraft had never had a hard landing flew off concrete runways and was never over stressed. Van's had the pictures but conviently deleted them so I sent them new ones. The weldments were not just cracked but broken completely through. If you are currently flying a pre 1988 RV4 I recommend you ask Van's for the pictures and inspect your weldments. Roger Moore