Here is the broken rudder control horn......

I needed to remove the turbine and pipe to access the fin retaining bolt.

I am sure glad I took the time to plan my install so that it made maintenance easy. Here you see the connection for the rudder servo under the fin.

Mask off the area of the broken horn and then mill it out with your Dremel tool.

Here is the new carbon fiber control horn. Mill the slot in the rudder to fit the new horn. I made a whole new linkage and dry fit the whole assembly.

Satisfied with the fit, I mixed up some 30 min epoxy and micro balloons and glued the new horn in place.

Painting the linkages...

The completed repair....

Next up is to improve the flap linkages. The problem is that the flap servo cutout from the factory has the servo almost flush with the upper wing skin. This forces you to use a long servo arm or cut a longer channel in the skin for your push rod as it seeks a hole in the servo arm closer to the spline.

Since I already had my slots cut out, I decide to raise the servo by opening the pocket toward the bottom wing skin.

I also decided to upgrade my flap servos. The 645MG have served me well in the past on flaps, but were not up to the task in this model. I installed Futaba 9155 digital s in their place. This is a 192 ounce servo. By raising the servo as I did , I was able to mount the push rod two holes closer in to the spline giving me a much better mechanical advantage over the previous setup.

Well she is all ready to fly again and I can hardly wait. Just need some good weather and a flying partner at the field. I am on vacation this week so I am hoping to get out soon!!

Wow, you didn't waste any time getting that fixed! Nice job, have fun this week!

Scott

Well it was a very bad day at the field yesterday. It started out great. The Hawk looked just beautiful on the tarmac and in the air. I had two perfect flights with amazing landings. This jet just flies itself to the runway every time! On those flights I heard some very mild buzzing.I do not think it was control surface flutter, I think it was the gear doors that stay open but I will never know for sure. On the third flight, I was going through my normal aerobatic routine and the jet felt rock solid as usual. This was flight number 8 on the jet. I did a knife edge from right to left with the canopy facing me. Right rudder was used and the plane tracked in Knife edge like it was glued to a wall. I rolled out of the maneuver and immediately felt something was not right. The plane felt very odd to control. In fact it wanted to fly on its side! Turning was difficult. Very wide and lacking a solid groove through the turn. I managed to get her on the down wind and dropped the first notch of flaps and the gear. While looking for the switch to drop the last notch of flap (I just moved the flap control from the left slider switch to a 3 position switch on the transmitter), I took my eye off the jet for a second. In that time, it rolled inverted. When I put my eye back on the jet, I was disorientated and quickly drove the jet into the woods below. Pilot error for taking my eye off the jet. The jet needed constant input because of the odd control situation and would not fly hands off. I feel I had things somewhat under control and could have landed it if I had not taken my eye off the jet. What I found out back home when I plugged things back in and turned on the radio is that the rudder was locked to the full right position. Why it did this I do not know. The fin was not damaged in the crash and the rudder and linkage were intact. The rudder was moving freely through its range of motion but when I turned on the system, went hard right. I have a lot going through my mind right now having just returned to turbines after leaving them due to the frustration I was having with them a year and a half ago. At over $8500 per jet (remember I bought bran new everything for both the F-4 and Hawk) I just cant afford to replace it. In fact the Hawk still isn't paid for and now its gone. My F-4 might be up for sale. I need a day or two to completely think about it.

Damn Dom, that just plain sucks. Wish I had some encouraging words, but I am at a loss. Was looking forward to seeing the Hawk at Ky Jets. Your thought and the extra attention to detail in putting these models together is over the top, and then have something like this happen surely makes you want to backup and re-evaluate. Sorry for the loss.

Dom, I am very very sorry for the loss of your jet, when I received the call yesterday I actually got a stomach ache!

You have put so must time and effort into these jet to have something like this happen, it is unmanageable.

One question did you check your servo arm, did it slip on the spline?
What model number of servo was it?

OMG Rich. I just came up here to post my findings and you guessed it. The Dubro Super strength servo arms slipped on the spline! I checked my 425oz elevator servo and it is slipping there too. This is what led to my crash. Ultimately the crash was my fault but this was the major contributing factor.

Very sorry for your loss. Hopefully you have discovered the cause.

During the knife edge, the servo arm slipped on the spline. When I went to neutral, the rudder was now offset giving me that yaw and making the jet difficult to turn and keep level.

My F-4 is setup the same way! If I sell it, the new owner must switch to aluminum arms. If I keep it it will not fly with anything less than aluminum.

Wow, I have used these arms for years in all my jets...hundreds of flights between them. Never an issue. Blows my mind.

After working the Dubro arm a bit on the servo spline, the arm became almost smooth inside...the grooves for the splines completely worn down. Scary.

Dom,
I know you fly both Futaba and Hi-Tec servos, is there a chance you used the wrong arm on the servo?
They are very different splines....[&:]

Oh no Dom. I'm so sorry. Give yourself some time to think before you sell stuff. Really sorry to hear this. Hang in there.

Scott

Not a chance. The arms are different colors and you know I have then neatly organized and labeled in my parts box!

Thanks for the kind words.

Just about everything is reusable so far. All my equipment stayed on the boards.....secured. The trees...ripping the wings off absorbed a lot of the force. The turbine is messed up however. I am packing it now to send it in for evaluation. Whether this can be fixed may be the deciding factor for me not selling my stuff.

I just had the same issue on a Panther, the right flap would not work and upon inspection I found the dubro arm was slipping on the spline. Fortunately for me it happened on the taxi in from a flight.