Guys,

I was very lucky yesterday when I had problems with my elevator on my aermachi, I just wanted to give you guys the heads up.

Yesterday my new aermachi was test flown by one of Florida's best jet pilots. During take-off everything seemed to be okay. A couple of passes later Robbie went full vertical and did a split-S. As the plane passed us over the runway we heard a fluttering sound. At first I thought it was the engine flaming out, but Robbie recognized the sound to be elevator flutter. He immediately brought the engine back to idle and slowed the plane to a crawl and was able to execute a picture perfect landing. We could not immediately identify the problem because the servo's and elevator push rods were all okay. On close inspection, we found that the elevator seemed to be trimmed in a downward position (approx 1/2 inch). When I dismantled the back end of the plane, I realized the horn/torque rod that connected the elevator surfaces was bent. Robbie tried to straighten the arm, and even applying only minimun effort, it broke in two places. We rebuilt the part and I will post pictures soon.

Could this be the reason for so many of the elevator related crashes of this jet?

The bent "thrust plate" (do you mean the horn/torque rod that connects the elevator halves??) is likely the result of the flutter not the cause. You have just experienced the 99th percentile reason Aermacchi's are lost on the first couple flights. It's not new news, stab flutter is very common in this plane.

Have you done all the mod's - installed the carbon fiber rod across the back of fuselage anchoring the stab halves. Glued the stabs down tight (after sanding off ALL the paint) and reglued on the inside with something like Aeropoxy. Do you have a dead tight, no slop elevator linkage?? Hinges nice and tight? I hope by "When I dismantled the back end of the plane" you only mean you took the thrust tube out. I know Tam likes removeable stab halves but that scares me.

Don't know your situation but those are the places to start.

Sorry i mean (horn/torque rod). All surface sand and glued with aerpoxy. The good thing is the plane came back in one piece so we could find and fix the problem. My thing is the (horn/torque rod) should not bend in flight thats scary

The first one I built following the instruction. I experience same kind of problem. That why I make some mod on the stab. I change the carbon rod with bigger diameter aluminum or stainless steel shaft. I also glue the brass tube go from one side to another. This brass tube join the two stab shaft together.
This kind of method been done on kangaroo and hospot plug in wing.
Why not using on the stab. Since I built my stab are removeable.
I using two servos for elevator. The linkage are the direct set up.

All the kits I built for customer with removeable stabs and fin. None of them experience this kind of problem again.
The proto type Viper Jet stab was done kind like the MB339. I rebuilt the stab just like I'm doing with the MB339. Now I got 9 flight on my Viper Jet. Average speed 192mph. Everything holding together.
I request Cermark make this chance on the Viper Jet before going to any customer hand.

Brg,
Tam

Hey tam i am willing to trade you my aermachi for one of your viper kit . I like the look of the viper, think i will order one from you.

I hope they listen to you this time.

Matt,
Yeap. They made a change on the stab. That is why there are some delay in getting the kit in.
Brg,
Tam