ESM PC-21

What a plane! This is a great flyer which can be presented and flown in a very realistic scale manner. Testimony to this are the many accolades bestowed on this ESM model aircraft at many fly-in’s around the country.

To me it was beyond question, there was only one way to power this bird, and that was by using electric power. This is the closest and most cost effective way in which one can get to mimicking the full size in terms of sound. In terms of performance, there is no shortage of oomph from the Turnigy 260kv motor matched to an APC 18x10 electric prop. Using Turnigy’s 120A HV (high volt) speedo and two 5 cell LiPo packs completed the electric setup. The front end of the PC was finished off with a True Turn 4” “Ultimate” shaped spinner.  The PC needs a long pointed spinner therefore I chose the Ultimate shape. True Turn make a quality product which spins very true!

I also opted for the optional pneumatic retracts. Although these are quite a bit heavier that the standard fixed landing gear, the extra weight is carried without effort by the PC. This optional extra includes three quality split aluminium rims, tyres, scale oleo undercarriage legs and all the necessary bits to complete the job. I believe that the pneumatic setup has now been changed to electric by ESM. This eliminates all the pneumatic plumbing and potential leaking problems. I did not experience any leakage although I did replace the standard control valve with a 5 way control valve from Robart.  Subsequent to that I converted my PC-21 to Lado electric retracts. These offer more scale like operation and have added benefits of not slamming open and shut submitting your airframe to shock treatment. The power consumed by the electric retracts is minimal. I used a 2100mAh Lipo, regulated down to 6.5v, to power the radio gear and retract system .

The quality of ESM kits are fantastic. The fuselage shows off panel linedetail and pre applied decals. The wings and tail feathers are covered with a clear shrink coat which is then sprayed the same colour as the fuselage by the factory. After the decals are applied at the factory, they spray the wings, tail feathers and fuse with a clear coat. This gives an excellent durable and shiny finish. The workmanship inside the airframe is of a high standard, all formers are glued in properly with no gaps being left. The wings are also of solid construction and offer excellent strength in the retract mounting areas.
Building this kit does require some work. One has to join the wing, glue in the ailerons and flaps, glue in the stabilizers and then attached the elevators as well as the rudder. Using the supplied cyano plastic fibre hinges for the ailerons and elevator proved fine as I didn’t experience any problems. Because I opted to use electric power there was one big mod I made to the airframe so as to provide access to the batteries without having to remove the wing. The mod was to cut out the cockpit which comes glued into the airframe. The fuselage has a moulded recess into which the canopy is seated and screwed down with self-tappers. Mount the canopy with the self-tappers making sure that it fits properly. Then remove the canopy, and using a Dremel with cutting wheel, cut along the bottom edge of the moulded recess line. This will release the cockpit area and provide you with a canopy frame. You can then screw the canopy back onto the cockpit and frame using the same holes you made earlier in the process. When performing the cut out work of the cockpit, be careful not to grind away the sides of your cut but rather to cut forward, remember that you are losing material as you cut and if you grind away at the edges you will have a sloppy fit between the canopy/cockpit and the fuselage. I secured the rear of the cockpit/canopy with a spring loaded hatch latch mounted in the fuselage and pinning into the canopy frame. At the front end I glued 2 dowels to the underside of the cockpit dash. These stop the cockpit/canopy from popping open. It is also advisable to glue 2 blocks at the front end of the hatch opening, inside the airframe to help to locate the dowels and stop any side-ways movement of the cockpit/canopy.

The PC has a nice sleek fuselage, but it is wide enough to accommodate a 5 cell Lipo pack transversely. The balancing the plane out showed that the two 5 cell Lipo packs had to be mounted on the CG. I had to extend the mounting tray in the fuselage forward of the front former to accommodate the second Lipo. The first Lipo has adequate locating area behind the first former, on the current tray. To extend the tray was very easy as there are already two ply longerons running forward of the mounting tray area to the front of the fuse. All I had to do was cut out a piece of 3mm ply and epoxy it to the longerons, voila! To hold the Lipos in place I used two clever releasable 10mm wide cable ties, and they work like a charm. These were purchased from a local 4x4 accessoriesshop.

I didn’t like the cross mounting bracket that came with my Turnigy motor, so I had a 3mm aluminium motor mount made with cooling holes matching those located on the rear of the motor. The motor was mounted to this plate and then mounted to the firewall using 4mm threaded bar. Threaded bar works like a charm as fine adjustments are easily made when you want to “fine tune”the fit between your spinner and cowling. One word of advice. Don’t use the factory markings on the firewall to locate you motor’s mounting position, these are wrong! I found this out after mounting the motor and then trying to fit the cowling. Rather use the cowling to gauge the location of the motor by first fitting the cowling. The cowling has a handsome scoop at the bottom front. Mount you speedo as close to this mouth as possible, but without it sticking out. This will provide good cooling. It is required that you glue the scale turbine exhausts to the cowling. If you look at scale pictures of any turbo prop engine, taken from the front, you will notice that one the one exhaust points upwards and the opposite one points downwards. Do the same with your PC’s exhausts. The exhausts also aid cooling of your motor as it provides an escape route for hot air from the cowling.

When it comes to fitting the retracts, all fits well. Just make sure that align the retract accurately so that these can retract and deploy without their movement being interfered with. The kit provides one with plastic red preformed wheel wells. These work great and allow you some measure of tolerance to accommodate the undercarriage in the retracted position. Don’t glue these into place. Rather use red electrical insolation tape and tape the perimeter of the wheel wells down to the wing. This makes life a lot easier when you have to remove the retracts for maintenance. Do not route your retract plumbing/wiring inside the wheel well where it can get caught onto the retract legs but rather use the wheel well to separate the plumbing/wiring from the retract legs. Looking at the full size, red hub caps were required. As the kit does not have any I used the bottom of 2 aerosol deodorant cans, sprayed them red and glued into place with 3 blobs shoegoo. The shoegoo holds them nice and firmly in place but can be popped off when needed. The full size also sports white undercarriage which can be achieved by sparying the u/g and inside of gear doors with a gray primer and then satin white.

As for servos, I used normal analogue plastic gear 7.8kg servos from Power HD on all surfaces except for rudder where I used 9.6kg metal gear Power HD servo. The radio I used was the Spektrum 7 channel. The PC does use a lot of servos and I ran out of outputs on my receiver. I therefore had to use y leads on flaps and rudder. The nose wheel and rudder use two separate servos. After I had installed the rudder and nose wheel servos, I discovered that one of the two had to be reversed. This is a bit difficult to achieve with a y lead, so I had to reverse one of the servos by swopping the wires on the motor and pot. If you know how you too can do it, otherwise there are servo reverse units available from your local hobby shop that plug in line and do the job for you.
Flying the PC 21 is awesome. She is an absolute pleasure to flyer and as mentioned is easy and very rewarding  to fly in a scale like manner. Slow your movements down, especially aileron and you will woe those at your flying field. High speed low passes are a must, slow rolls will present the plane like no other manoeuvre.  With her dolphin like shape the PC-21 has presence in the sky. She is a slippery ship and consumes the airspace rapidly. I clocked my PC-21, using a gps placed on board, at 222km/h. Because of her shape, the PC-21 assumes a nose down flying attitude. Don’t let this confuse you when you fly her inverted, you will need to hold that nose up with down elevator. She performs a flat spin just like the full size and is very aerobatic. Deploy the flaps and she will slow right down, the turned up wing tips induce a flat stall so she doesn’t throw a wing. On landings keep the nose pointed down, balance her on elevator and a touch of throttle, and then flare her to perform a graceful touch down. Fly her as described above and she will be on her way to becoming your favourite!

Enjoy!
Stan Hausmann

PS on Sept 11 I crashed my PC-21 into a tree. The plane was totally pulverised beyond repair. It was a very sad day. The crash was caused by pilot error in that I lost orientation in a manoeuvre. My next PC-21 will be even better!