| Author | Message | ||
     larry davis New member Username: Larry_davis Post Number: 1 Registered: 03-2006 |
We have just finished our FT 2000 -we have the newer straight tail - and are finding an issue with the rudder action {lack of authority } have we made a mistake or is anyone else having this problem? thanks ,larry davis - phx., az. | ||
| doug dhell New member Username: Rv76 Post Number: 1 Registered: 03-2006 |
larry do you mean in flight authority, or just range of motion on ground | ||
| larry davis New member Username: Larry_davis Post Number: 2 Registered: 03-2006 |
Doug - The problem is primarily with low speed control, so I'm assuming that an increase in rudder travel might be a solution. I'm looking for info that someone else might have as to their experiencs and solutions. ljd | ||
| doug shell New member Username: Rv76 Post Number: 2 Registered: 03-2006 |
larry by the way i will be in phoenix gyr on 4/15/06 would like to see your plane and maybe we can compare notes at that time. by the way ive built 5 ap, and flown many others, the express, in my opinion is the best by far. doug | ||
| doug shell New member Username: Rv76 Post Number: 3 Registered: 03-2006 |
larry ive noticed that when i slow down to around 80kts i also experience slow yaw response in fact i call it wallowing in the air i try to keep my approach speed up to 80 or above and it appears to be much more stable, i have afull 25 degrees of rudder travel both directions. even at 80kts i touch down at about 65-70 i regularly fly out of a paved rwy that is 2630', even at 90kts i still dont have to use brakes except for turnoff. ive learned to live with low speed yaw control which on the express is better than i had on the velocity xlrg. read the cafe report before you decide to increase rudder travel. even in strong ie 25kt crosswind i have had no problem with rudder authority. it might help you if you read some of bill copeland's newsletters there i beleive if memory serves me correctly there was some discussion in the past of the problem you mention. i know not much help but my 2cts. doug | ||
| Bruce Newlan New member Username: Bnewlan Post Number: 3 Registered: 09-2002 |
Hi Larry, We have tested the estimated ACTUAL rudder travel by attaching a fish scale to the trailing edge of the rudder and then pushing on the rudder pedals as you would in flight. Once the rudder is at full defflection start pulling against the deflected rudder with the fish scale and note the relation of flex back angle to the pounds of pressure exerted by the fish scale. We have found in testing that many design factors combine to result in considerable "FLEX" in the rudder control system that limits actual rudder travel in the actual flight loaded condition. Some factors are the vey small span of the rudder control horn, highly disadvantaged rudder pedal torque tube horn ratio, many twists and turns in the cable routing, and highly dissadvantaged ratio of pedal travel to rudder position. We finaly had to redisign the rudder control system to connect directly to the rudder pedals and then route the cables down each side of the cabin to a redisigned rudder horn to obtain real world rudder travel. All other Express pilots just get used to vey limited rudder control. Regards, Mike Mc Daniel | ||
| Bruce Newlan New member Username: Bnewlan Post Number: 4 Registered: 09-2002 |
Hi Larry We found that ACTUAL in flight rudder travel was far lower than you might have when you check the travel in your hanger. The main problem is that the rudder control horn has a very small span and the rudder pedal travel is ver short as well resulting in a highly disadvantaged control system, We found that if you block the rudder pedals and load the trailing edge to as little as 25 lbs of force to simulate air loads that the rudder can be deflected at will. The undesireable condition is the result of poor linkage design and far too little cable travel copuled with too many pullys that introduce backlash and "softness" in the system that renders it less than ideal. We installed a new wider rudder control horn and rerouted the cables down each side wall of the cabin and connected the cables at the pedal Brake hinge bolt pivot point therby increasing the cable travel by over 400% . While the rudder is still not perfect it is vastly improved. Good Luck. | ||
| AndyFawcett New member Username: Drew Post Number: 12 Registered: 03-2003 |
Any chance Mike & Bruce could publish pictures & drawings for their rudder mod? Modifications to the aft bellcrank would be very costly after close-out of the tail. Before that a redesign which rotates the bellcrank so the arms are vertical (& longer) would reduce the spongyness due to cable stretch/linkage play. We considered doing away with the aft bellcrank altogether & just having big control horns on the outside of the rudder (but this would look a bit too much like an RC for my liking). By-the-way: does anyone have similar issues with the flaps? I have moved my flap motor into the cabin under the pax seat, but i still get a lot of deflection from a moderate amount of force applied to the flaps when the are fully deployed. Thanks - AndyF | ||
| doug shell New member Username: Rv76 Post Number: 4 Registered: 03-2006 |
larry, bruce brought up some interesting points which raises some questions, 1. do you have the original cable, and pully system or, the later version of the shielded cable, i have the newer cable system with the cables running along side the pushpull tube for elevator, no pulleys, no twists, and only gentle turn at front brkt, and rear brkt. in flight i can push rudders stop to stop so i would guess bruce makes a very good point, it appears a lot of authority you may lose depends on configuration and type of cable design. also it would be interesting to fly another express to compare. doug | ||
| Jim Ward New member Username: Jehward Post Number: 48 Registered: 02-2000 |
Bruce/Mike: Do you have any pictures that you can share? Are the "cables" that you ran down the sides of the cabin sheathed "push -pull" cables, or the original aircraft twisted cable? Thanks, Jim | ||
| Gary H. Wolfelt New member Username: Wolfelt Post Number: 43 Registered: 11-2003 |
Marshall Whitt (Composite Air, Toledo, WA) has redesigned some of the factory parts/procedures and has fixed all of these problems. He has had the required parts manufactured and is presently installing them on three Express projects (one of them is mine) as of this writing. I have passed the last few posts onto him by e-mail to see if he would like to make a mod kit available for anyone else that is interested. Wait and see what he has to say. GHW | ||
| Tom Ware New member Username: Thomas Post Number: 5 Registered: 11-2005 |
i too would like to know more about the rudder problem fix, since i'm in the middle of building my rudder and installing the original ct tail cables? | ||
| David Rowe New member Username: N12ex Post Number: 3 Registered: 05-2005 |
The rudder control or yaw stability is the one thing I would like to change on my CT. I'm guessing that is the reason the airplane has a tendency to wander a little in turbulence. Holding my feet on the rudder pedals helps, but not as much as I feel that it should. It would be nice to get that straight tracking sensation that an RV8 or Comanche has. | ||
| Bruce Newlan New member Username: Bnewlan Post Number: 5 Registered: 09-2002 |
Hi Guys: Some have asked for some more detail on how we changed the rudder cable system on my Series 90. I know that some of this could apply to the CT design, however, my comments and pictures are for the Series 90. Rudder authority is more demanding with a tail dragger, like mine, however I know the tri-gear could use some more help. In my previous postings I stated that rudder FORCE is more important than just deflection. You may have 25 degrees of deflection on the ground, however, the air loads can easily reduce this to just a few degrees. Try the fish scale test I mentioned before. I now have 17 degress of travel each way, but with tremendously more force. With my setup I could have opted for more travel by moving the cables in (shorter rudder horn) but with a lower resulting force. My fix improved the situation immensely, and it increased cable travel 3 or 4 times, however, I would prefer even more travel. This would require changing the rudder pedal system entirely. The next project is a potential change to the tail itself to improve handling. Bruce    |