Workshop

July 12, 2009

Sunday began with final checks of the plane and the canopy task. these were finished up and Ben arrived to do some engine things.

The engine was programmed and Ben let it through the process and got the starter to turn the turbine up.

The batteries were then charged and the engine test was done with the result that the engine ran fine and the main tank has a leak in the cap. The plane had to be dismantled and the tank removed, repaired and the entire thing put back together. This seemed to work very well and then we found a large problem.

There was some setting in the transmitter that caused the throttle trim to move the elevator and the elevator trim to move nothing at all. We set about finding the problem and through some tricky team problem solving we discovered that this transmitter has the ability to assign the trim to any function you want. Why would anyone want to do that and more importantly, why did someone do that ??? We corrected the problem and all seemed to be ready.

We arrived at the lovely Valley field late in the day and set up the plane. We ran all the tests and pumped up the air systems in preparation for the first flight.

The motor was run up and all looked good to go.

And we were off as George pulled the plane out on the runway and ran the big turbine up to power. The plane ran down the runway and took to the air.

It climbed out in a shallow climb as George let it gain speed before gaining more altitude. The left hand turn was completed and the plane began a run back in our direction. The wings began to rock at about 1/2 throttle and the rocking increased to an oscillation. George realized there was a problem and throttled down and gave an up command to gain altitude. The plane did not answer and dove to mother earth. In this case it was the river -- what a mother. It went in to the river and completely destroyed the plane.

I have looked over the junk we managed to get back out of the river and it seems that there are several possible causes

1. The receiver, we now find out, was one that Futaba has had problems with and is now upgrading to make it work better ---- this one had not been upgraded. Who knew there was an upgrade??

2. The elevator servo and one of the aileron servos were recovered and they were both stripped out. Were they stripped on impact with the water, or in the air?? They were not metal gear servos and turbine planes do get right with it.

3. Was the transmitter somehow intermittent??

 

What was not a problem in the crash seems to be

a. The plane itself did not fail or come apart in the air. I paid close attention to the plane and it was in one piece al the way to impact. The way this plane is build, I was frankly surprised that it flew well and CG and trim were all in good order.

b. While this design is prone to wing walking and that could be contributory to the loss of the plane, the speed of the plane rules this out as a cause. The wing walking happens at slow speeds with the nose up. This was not what happened to the plane.

c. Pilot error was not a factor in that George flew it well and the telling point is that when he gave it up elevator the plane made no response. The wing rock could have come from many causes but when the plane did not respond to the up command and the down throttle command, we have to give the pilot a clean report ---- just not his fault

 

My sincere regrets go to Ben and I hope the turbine can be reworked and fly again. This is a bad way to go and we all feel terrible about the accident.

 

 

 

July 11, 2009

Saturday was a 1/2 day session and it saw a great many items improve on the plane.

The long awaited air connections arrived and were installed. Both air systems were charged up and checked out. We got 10 cycles of the landing gear on one charge of the tank and more brake cycles than I could count. These systems look good.

The last of the assembly was done on the equipment and all servos and systems are working. I adjusted the ATV on the flaps, ailerons, and elevator. Everything looked good on the servos.

I went over the plane for cosmetic issues and corrected all items. There were some unsightly holes in the covering where the booms are attached and since the booms will be left on the wings, I covered over those areas.

As you can see below, I covered the tips with white to help distinguish the bottom of the plane

There were other holes and dings that needed attention and, while it is an ARF, it came out looking better than expected. The final stickers will be up to Ben tomorrow morning.

Since the plane is nearing completion, I took a photo trip around the plane and the shots are below.

The CG is at 10.25" back from the leading edge at the root and this seems OK for the first flight.

The canopy mounts were glued in place as the session ended and tomorrow we will test run the engine and final inspect all of the plane. If it passes, we will fly it in the afternoon.

July 10, 2009

This was the day that will tell if flying on Sunday is in the cards and it went pretty well.

Flap servos were replaced and tested

The turbine was mounted using custom made blocks of hard wood.

The blocks were painted black and then mounted to the plane. The turbine was then mounted to the blocks and aligned to be straight with the center line of the plane.

The down thrust was set at 5.25 degrees from the flat deck at the rear of the plane. The system was then wired and fuel lines run to the turbine and the upper control board. All of this took time and came out very well.

 

The plane was reassembled and checked for fit.

The fuel system was installed per the instructions from the turbine and the experience of Ben. There is a small bubble tank that feeds the fuel pump to the turbine. The vent line from the bubble tank goes to the clunk of the 2 L bottle we are using for the main tank. The vent line from the big tank goes to a select valve that can select vent to overboard or the remote tank. The turbine burns 8 OZ per minute so even with 2L onboard it is not a lot of time. The large tank had brass lines drilled through the cap and epoxy used to plug the air leaks. All the plumbing was put in place and will be tested with the engine.

The upper board was mounted and all equipment was checked for proper installation.

July 9, 2009

There is a lot of talk about flying the plane this Sunday and since I am taking Saturday off, this will be close indeed.

Yesterday we stripped one of the flap servos while setting the ATV. This is the only downside to having alum servo arms and bullet proof linkage. I ordered new servos for the flaps and they are metal gear this time as the plane will not land well if the flaps would strip out in the air. They will arrive tomorrow and I will solder new leads on them and the problem will be cleared.

The second problem discovered in the morning is that the retract valve is operated by a mini servo to save space and it failed under the load of the valve. As noted before, this is a process with some error in it and I am thankful that it failed in the initial testing and not in the air. I took time to rebuild the mount and install a larger servo that is known to have the power to run the valve.

The upper board was completed and all the turbine components were mounted and the plumbing was done. The board was fitted in place and it looked good. Mounting of the board will wait for final assembly. It appears that all the equipment will fit in the fuse, an outcome that I had my doubts about. Final checks are still to be run, but it looks like this just might work. I still have concerns about the quality of the construction holding up under the force of this big turbine and I hope we do not have an ugly surprise waiting for us on the first day out.

The servo to run the nose wheel was hooked up and tested. I installed the pull-pull system and the steering looked minimal but OK. The problem with most of these systems is getting the wires tight enough to have predictable steering. I added links that will allow us to tighten the lines in the future. This is difficult in such a small space, but worth the performance improvement.

Before time ran out I began to install the turbine. It is a very large unit and so I began by opening up the tail end of the fuse to allow the turbine to sit on the mounts. It has a screen over the front of the unit and that prevents the usual solution of sticking the starter unit up inside the back of the fuse.

July 8, 2009

The first task of the day was the final hook up and testing of the flaps, Ailerons, Elevator and rudders. The rudder has two servos plus one additional servo for the nose wheel. All this work was done and everything checked out. The nose wheel servo is shown below and the brake valve and servo is at the bottom of the photo. This is the lower board as there will be another board fitted above the one shown. The upper board will have the main switches and all the various stuff for the power plant.

The nose wheel cover was a problem Ben and I had worked on the previous day and they all needed to be finalized. They were glued in position and sealed with striping tape. The areas where the retracts mount to the plane still need attention.

The wiring needed some final solder joints and they were all made up and tested. I then continued the work on the lower board by mounting the nose wheel servo and the turbine battery. The receiver also went on the board along with the flaps alignment control. All of this was completed and the board fitted to the plane.

The retracts were completed and the servo installed as shown below.

July 7, 2009

I began with the completion of the large tank retaining system. I installed the tank and inspected the location to be sure it was in line with the CG The hard mounts for the main former as shown below

Below you can see the front part of the compartment with the lower board in place and the servo for the nose wheel in position. The second air tank is under the board and other components will be added to the board later. The nose wheel retract was mounted and tested.

Before continuing with the equipment, I wanted to assemble the plane and run the wires and tubes to determine the best equipment layout.

Above you see the left wing with the boom and the stab attached and the wires and air lines in position in the root of the wing. There were large problems encountered setting the booms as 3 of the 4 blind nuts were defective and had to be replaced. The holes in the wing did not line up and the fasteners were not the correct length.

After the booms were attached and the wires run, the rest of the assembly continued.

The assembled wing was then attached to the fuse. the wings come with hex head bolts that are driven from inside the equipment compartment near the floor. This is a bad system so I replaced it with posts that allow wing nuts to be applied from inside the fuse. The holes did not line up and some cutting was required to fit the wing up to the fuse.

The same process was used to assemble the other wing and the plane was together for the first time. The wires were then run from the wing root to the equipment compartment as well as the air lines for the retracts and brakes. All electronics were tested to be sure the surfaces worked. directionality and throws will be set later.

July 6, 2009

The day began continuing to work on the equipment compartment problem. This plane was just not made for this much equipment and the giant fuel tank that we are using. Problems like this require innovative solutions or smaller equipment and so I am going to try some innovative stuff. Since this is a blog, I will show you the steps even though most of them will not work and will be removed later. The problem is that there are things that just must be on board and room is at a premium.

FIRST - the retract and brake valves require a lot of space because they use the valve and a servo to drive it. We looked into digital switches for these 2 functions and they are not reliable enough for us. I decided to build a mockup of the retract valve and a really mini servo. The mockup is shown below and it actually worked quite well.

After some thought on the subject, I decided to try to hide it behind the tank former in some space that was not going to be used. The valve was mounted behind the former and I will find a way to mount the servo in front. The problem here is that the wing bolts will pass through the bottom of the compartment where you see the wing shaped piece of ply glued to the wall. During assembly the bolts will go in there and be tightened with a wrench so I have to leave access to the bolts.

Below is a shot of the valve and the brake valve will be on the other side ( bottom of the shot). This will work well because all of the air lines will stay aft of the former except the supply and fill lines. If this works it will be a neat looking installation.

Leaving that part until the brake valve arrives, I turned my attention to the front of the plane and, as you can see below, one air tank was fitted into the nose area and both of the main batteries were padded and worked into the area ahead of the equipment.

I then completed all the structure work in the nose and tail of the fuse and applied Aeropoxy to all the joints. Aeropoxy is the choice of all who try to glue wood to fiberglass as it really works, wont run, and takes all night to set up. I usually leave the gluing to the last thing of the day and it is all set by the next session. Below you can see the white material reinforcing all the joints. I use thick CA to hold the parts in place until I get the Areopoxy to it.

At this point I have the tank, batteries, retracts, retract valves, brake valves, batteries and one of the air tanks in the plan. There will be many other things to fit in there and oh yes,,,,,, a big old turbine will go aboard too. Lots to do another day.....

July 5, 2009

The completion of the booms was first for the building session. The elevator and both rudders were fitted with control horns in the same way as the elevator and the servos were mounted on blocks. Linkage was made for each servo and wires were extended to reach to the wing core. Each servo was then plugged in to the receiver and tested after adjusting the length of the linkage. The booms were then reinforced and set aside.

I then completed the setup of the wings by installing control horns in the ailerons and making linkage. More detail on the linkage is available at the tips and tricks section of this site. Once the ailerons were complete the hinges were glued in place.

The flaps were then hooked up using bolt on control horns. This will be sufficient for the load the flaps will see. The linkage was completed and the last flap was glued in place.

The fuse was next and I began by removing the center of the formers in the aft section to allow for the gas tank. I will add reinforcement to the structure at a later time as the large tank needed to be positioned first.

Once the tank was in position I cut a paper template for the former at the rear of the cockpit and discovered that the tank position would be too far aft. I moved the former foreword to position the center of the tank over the CG.

Below you can see the first cut of the former and the tank in position. The former will be fitted, lightning holes added and it will bolt in position to hold the tank and yet be removable when needed.

The equipment compartment will be quite full, and the planning for the boards seemed like the next thing to get done. The shot below shows the front of the compartment with the nose wheel in position.

As the session ended, I made plans for the inside of the compartment. There will be a upper and lower board and formers at the front and back.

July 4, 2009

The session began with the booms. Each boom will have a rudder servo in it and one of the booms will have and elevator servo attached on the inside of the boom. Since the boom is too thin for a servo, I had to cut the holes and then make blocks to build up the thickness to accept the servos and to give a proper mount. The holes provided were for mini servos and were undersized for our needs.

I reinforced the area under the blocks with 1/8" ply and mounted the servos with wires extended to reach through the booms and the wing.

The elevator servo is shown above and the rudder servos are done the same way. The servos were screwed to the blocks and the aluminum control arms were added to the servo. The linkage was then build from 4-40 rod and c/f tubes for strength. This makes the strongest linkage I have ever seen at a reasonable cost.

With the forces this plane will be seeing, the control surfaces need to be moved with authority.

Next I worked on the stab and elevator. The control horns are not close to strong enough, so I replaced them with the post type shown below. The elevator had to be strengthened to accept the post style control horn. I drilled the elevator and installed a 5/8 hard wood dowel and then drilled out for the post. I saved the covering from the servo cutouts and recovered the end of the dowels.

The finished control horn is shown above and it will work well at the speeds this plane will see.

July 2, 2009

I met with Ben Yesterday and we discussed the plane and his needs for the build. Since this is an ARF, I will give brief notes on the actions taken to put the plane together assuming you have done some ARFs before.

There is an extensive thread on RC Universe on this plane and it has lots of detail on the build. Since this was designed to be a prop driven plane, we have some concerns regarding the strength of the plane and some of the components. I will show the things done to increase the strength and counter some questionable glue spots in the plane.

I began with the wings. The covering was pretty good and there are 2 wing tubes and 2 bolts holding the wing to the fuse. I opened up the servo bays for the ailerons and the flaps as well as the retracts. This gave entrance to the inside of the wing and I re-glued all the joints I could get to before I did anything else to the plane.

 

Next I decided that the servo wires will have plugs at the joint of the wing and the fuse as threading the wires to the receiver would not be good form. I do not like extensions for servo wires so I soldered additional wire to the aileron and flap servos to just let the plug extend from the plane. I set up all 4 servos at one time and they are shown above.

Next the servos went in the wing and the retracts were fitted to the wing and the mounts altered to take the mounts. The gear mount was attached to the hard wood mounts with machine screws and blind nuts. The tubing for the air retracts and the brakes were run and attached in a packet with the servo wires. this will make the wing simpler to hook up during assembly.