RV-9A steps

Guys: MY -9A is two years old and 320 hours TTSN. Today I was cleaning the bugs off and rubbing on the right step when I noticed a crack in the paint on the forward and aft edges next to the mounting plates, where the vertical leg is welded to the mounting plate. Upon further inspection, I found the crack extended from the front radius inboard to the aft radius just outside the weldment. I checked the left step and it is also cracked but only about 3/8" in the middle inboard just outside the weldment. I use the left step every day, flying or mx and the right step is hardly ever used except for my 120# wife. They both seemed to have failed in compression and I have no clue why. Both steps are painted not plated. I wonder if this is a fatigue crack caused by propellar resonnance? What do you guys think? Anyone else experienced this cracking of the step in this particular area? Dan.

Known issue, has happened to many.

One of the "theories" is that when people turn around, facing aft, and step off on to the step, they tend to add a shock load, causing the cracks. If people dismount backwards, the gently feel for the step and slowly add their weight to it, they don?t crack.

Other than that, this is a common problem.

Here is what I did. I am not a materials engineer. Reinforcing plates on inner and outer surfaces. It is not pretty but hopefully functional.

Initial crack on inboard



Inboard repair and reinforcement



Outboard reinforcement

I am not a materials engineer either, but my father was an aircraft welder and I saw how he handled this sort of problem. If I had known about this problem when I built, I would have heated the area from the welds out 2-3" to a dull red and let them cool slowly. This type cracking can be caused by quick welds with very concentrated heating. Annealing the area spreads the stresses and removes some of the brittleness near the weld line. MIG welds are affected more by concentrated heating than acetelene welds. At least that is how I understand the problem. Since I didn't do that, I am glad I installed the steps with screws instead of rivets...

Bob Kelly

Thanks Bob, I don't know the difference between the welding methods you mentioned (I could google it), but that may offer an option for people to try before installing the steps.

I did not use screws to install my step but did install nutplates on the baggage floor so getting back in to remove the step was easier. I had to drill out rivets on the baggage floor initially since my step installation was a retrofit. If I install a step on the pax side I will use screws/bolts as appropriate, anneal the step as you suggested AND reinforce both sides.

It may be a few years before I know if my fix worked. Even then. I have minimized using the step when in the hangar so overall step usage is down compared to before the initial crack developed.