21 Jun 98 - Further comments from flights. 21 Jun 98 - Further comments from flights.
This will be a review of the assembly and flying of the Flitecraft A-36 Bonanza. It will not go into every action just the good and bad design and production points and problems found during assembly. I decided to follow the instructions exactly as written to make sure the review is as fair as possible.
Assembly
Poor Production Point 1 - The flat on the nosewheel leg was ground in the wrong place. I had to remove the leg again and grind a new flat on the shaft. This added about 5 minutes to the assembly time.
Poor Production Point 2 - The 'Z' bends on the control rods were more like lazy S bends. I didn't trust them to stay in place so I had to remove each and rebend them. This added about 15 minutes to the assembly time.
Problem 1 - The engine would not fit in the mount supplied. This is covered in the instructions but not until the nosewheel is assembled - strip it down again. The Dave Brown mount recommended by Flitecraft is not available in the UK. I spent quite a time locating a mount that would fit with little modification. I had to make up a spacer between the mount and firewall to get the nosewheel in the right place. The modification of the new mount and manufacture of the spacer added about 45 minutes to the assembly time.
Problem 2 - I had to cut the top of the fuselage around the engine bay to be able to drill the engine mounting screws. Even though my engine mount is slightly larger than normal I can't see access being possible for any engine / mount combination. I also had to trim the fuselage around the nose to give clearance around the carburettor. This added about 5 minutes to the assembly time.
Problem 3 - My muffler doesn't fit - it interferes with the fuselage in a big way. The only solution is to get a different muffler for my engine - in the end I bought an OS 40-46SF, FX series muffler which has the same bolt hole spacing and fits the model superbly. I had to buy an alternative muffler to suit the model. This is not really a problem with the model itself as the muffler supplied with the MDS 48 Pro is a little unusual. There was no time penalty due to this & I have added no time to the assembly process. With a different engine & muffler the problem may not arise. However, this did stop the project for a few days whilst finding and obtaining a suitable alternative.
Problem 4 - The throttle linkage was too short. I had to make a new linkage for the radio bay end because of this. This added about 10 minutes to the assembly time.
Problem 5 - There is no direct mention of using an extension lead on the aileron servo lead. It is mentioned that the servos, switch and extensions are plugged into the receiver but it doesn't say what the extensions are for. This would mean having to remove the RX from the foam every time the model is rigged. It will also wear the RX pins and risks damaging them.
Problem 6 - The radio bay is extremely cramped and fitting long servos horns is not possible. This means that the push-rods are located in holes close to the control surface which tends to increase play in the control system. This also meant that there would be no way of achieving the stated 30° nosewheel movement due to the large radius of the arm on the leg. In practice only 15° could be achieved given the space in the radio bay.
Problem 7 - The starboard wing suffered some minor damage in transit. The covering at the trailing edge at the wing root was slightly detached and had to resecured with a little epoxy. The starboard wing tip had also become partly detached and required reattaching. This added about 10 minutes to the assembly time.
Problem 8 - The instruction book has several incorrect photographs in places. Having joined the wing earlier the photographs suddenly show you applying epoxy to one side of the spar joiner again instead of fitting the leading edge cap.
Good Design Feature 1 and Problem 9 - The moulded servo stilts for the aileron servo are a great idea. However, there is no mention in the instructions that the rear stilt has to be cut down to get it to fit within the depth of the wing. This added about 5 minutes to the assembly time.
Problem 10 - I was very careful in orientating the aileron servo in respect to the stilts as shown in the photographs. Later it transpires that the stilts are on the wrong way around and had to be swapped over - the first 2 photographs were wrong. This added about 10 minutes to the assembly time.
Problem 11 - The push rods for the ailerons were too short. I had 2 options, fit longer push rods or mount the servo around the other way (As I originally had it). I choose the later option as I don't like long push rods. This added about 15 minutes to the assembly time.
Problem 12 & Poor Design Feature 1 - The list of tools required to assemble the model in the front of the manual is incomplete. All of a sudden the manual calls for a 1/4-20 tap to cut the threads for the wing bolts. As American thread forms are rare in the UK I couldn't easily get a suitable tap. I decided to replace the bolts with M5 which are readily available. The design uses two 1/4-20 steel bolts to hold the wing on - these would hold a truck off the ground. In the event of a ground loop considerable damage is likely to the wing locations as nothing can give. If the bolts were nylon they would snap minimising damage to the rest of the model. Further, the frequent removal of the steel bolts from the wooden retaining plate will wear it out in a relatively short time. If the nylon bolts are used little wear will occur to the model and the bolts can be replaced much more easily than inserting liners or captive nuts to the retaining plate. This added about 15 minutes to the assembly time.
Problem 13 - The is no mention in the manual of the Centre of Gravity (CofG) position range. The advertising flyer says that balancing problems are all but eliminated when standard radios and engines are used. I consider that this is a major oversight by Flitecraft. I sent them a fax (on 27 May 98) requesting an urgent e-mail or fax answer of the CofG position but have received no response 16 days later. The model actually balances at the 30% mean aerodynamic chord position which doesn't seem unreasonable. I intend to fly the model in this condition and see what happens.
Poor Design Feature 2 - The RX antenna is routed along the fuselage and exits slightly below but on the same side as the elevator snake. As speed the RX antenna may end up whipping against the elevator control horn. It would have made no difference to the cost of producing the model and would have been much more sensible to have the RX antenna exiting on the opposite side from the elevator snake.
Total time to assemble the model was about 5 hours, of this the time due to problems was 2 hours and 15 minutes.
As Flitecraft say, the model could easily be built and flown in a day. However, there are a lot of small, niggling, problems with the assembly process that could easily be resolved.
Flight
The motor was new and had not yet been run so I ran about 1/2 a tank through on the ground to bed it in a little. The mixture was adjusted and set a little rich to protect the new motor during the running-in phase.
Wind almost steady and at approximately 10 mph from the North. The surface of the strip was damp grass at about 1/2" long.
A short taxi test was conducted to see what effect the reduced travel of the noseleg. The model was taxied out cross wind and needed rudder input to maintain track. The model was very responsively and would complete a 360° turn with about a 3m diameter.
The throttle was advanced and the model tracked straight and rotated away after about 15m. I needed to correct by about 6 clicks left aileron and 2 clicks down elevator for level flight at full throttle. The alignment of the ailerons is difficult to judge due to the moulded end caps on the wings. It would appear that these are attached at slightly different alignments to the wing.
I completed a couple of circuits to familiarise myself with the control responses. The model has little tendency to drop it's nose in a turn, requiring only a slight amount of up elevator to maintain height. I decided to start with a single axial roll, which the model completed very well with little deviation from a straight line.
I then completed several loops at varying speeds and radii. I discovered that if full up elevator was applied at high speed the model screwed out of the manoeuvre. This must be due to the high g-forces that are being applied causing a high speed stall. If the stick movement is reduced at high speeds the model completes the loops very cleanly with no tendency to screw out.
I climbed little and cut the throttle and let the speed bleed away with the nose held at 10° above level until full up elevator and a stall was achieved. The model nodded forward and stayed straight. I repeated the exercise with the nose about 30° above level I also held in full right aileron as the nose dropped. The starboard wing dropped and the incipient spin commenced from which I centralised the ailerons and eased the stick forward to recover.
I was just about to climb again to test the spinning properties when the motor stopped. I landed just short of the strip in the rough grass, slightly bending the noseleg.
I had trouble starting the motor and then noticed a small piece of plastic stuck in the fuel tube. It must have been loose in the fuel tank a been sucked up. This was removed and the motor started without a problem.
It then started to rain and flying had to be abandoned for the rest of the day. When I next get a chance I will try out spins and other more strenuous aerobatic manoeuvres.
The weather has been great this weekend except for a gusty wind with a speed of about 15 - 20 mph. I managed to check out the model's spinning characteristics. When slowed down to the stall and full up elevator, aileron & co-ordinated rudder applied the model spins very easily in either direction. When the rudder is release the model continues to spin at the same rate. Centralising the controls stops the spin after about 1/2 a turn. I am still developing the technique of stopping the spin on the required heading.
If full up elevator, aileron & co-ordinated rudder are applied above the stall the model pitches up slightly and commences a superb flick roll spin entry. This has to be seen to be believed.
Very little down elevator is needed to maintain height inverted due to the symmetrical wing section.
Problem 14 - I have been experiencing engine cuts in flight. I removed the fuel tank and pipework to determine the problem. The problem was the clunk weight in the fuel tank. It moves easily from side to side and up and down but won't move fore and aft. This means that any prolonged period nose down (e.g. spinning) with less than 2/3 of a tank starves the engine of fuel. The tank was preassembled and I didn't check it out as it was already in the fuselage. I'll have to strip the tank down and rectify this problem with some better tubing or heavier clunk weight.