Lockheed 286L from Witte Helicopters

Lockheed 286L from Witte Helicopters

My trip to Rotor Live proved expensive because that is where I first saw Stefan Witte with his beautiful Lockheed 286L – I just had to buy one! The model is supplied without mechanics, so I needed to decide on what mechanics to fit, and at the same show I saw the PSG scale mechanics… This proved to be a VERY expensive trip! It transpired that one of Stefan’s customers had fitted the PSG mechanics and was able to supply a set of carbon fitting plates, but I am jumping ahead of myself…

Many years ago models of the Lockheed 286L could be bought and I remember seeing photos of those produced by Kavan and Graupner in the 1980’s. These models used .60 i.c. mechanics turning 66 – 68 cm wood rotor blades – yes these were very exotic machines and a far beyond me both in cost and certainly skill…

A Little History

The Lockheed 286L was developed from the XH-51 that was an experimental program to explore rigid rotor technology and high speed flight. It was a single engine machine with retracting skid undercarriage and 4 seats, originally fitted with a 3-blade rigid rotor head and later a 4-blade rotor head. The XH-51A had a rotor diameter of 12.4 m (40’ 9”) and was a mere 2.5 m (8’ 2.5”) tall, it was powered by a Pratt & Whitney Canada PT6B-9 turboshaft engine developing 550 HP (410 Kw) giving it a maximum speed of 151 knots (160 mph/257 km/h), although other records suggest the top speed was 280 km/h (174 mph).

The XH-51 program also produced the XH-51A Compound that had an auxiliary side mounted 2,900 hp Pratt & Whitney J60-2 engine. In May 1965, a newsreel film showed it flying at 240 mph and reported an earlier run of 272 mph, while other records state it achieved an unofficial speed record for its class of 486.9 km/h (302 mph). To put that in context and show what a truly remarkable achievement it was (and is), 48 years later in 2013, the Eurocopter X3 hybrid was recorded to achieve 293 mph…

The 286L I chose to model was built in 1966 as one of 2 demonstrators (XH-51N configuration) that had 5 seats and the 4-blade rotor head. These were taken to many air shows across the US where flight displays included loops and high speed runs, but did not lead to commercial sales. The 2 demonstrators were then used as executive transport and eventually sold to a collector but unfortunately were later destroyed in a fire.

If this has excited your interest, a Google search will reveal lots of interesting information on the XH-51 program including links to original footage of the experimental machines flying. Even if you are not interested, it is still worth a look because the videos take your breath away.

Witte Helicopters

Witte Helicopters (http://www.witte-helicopters.de) produce a very limited range of helicopter fuselages and a range of rotor blades. Stefan Witte is the man behind the business and his products are hand made to the very highest quality. The current range covers the Hughes 500 D and E versions in 1:5.8 and 1:4 scale, a 1:5.3 BO 105 CB and the 1:5.3 Lockheed 286 I have here. He also offers a Lockheed XH-51A with winglets to make a ‘Compound’ that will carry a small turbine or ducted fan.

Stefan’s scale rotor blades include 630, 680 and 777 mm symmetrical blades and specific blades for the fuselages he offers including 900 mm for the Lockheed. All blades are available in matched sets to suit your needs.

The Model

The Lockheed 286L is at a scale of 1:5.3, which gives it a rotor diameter of 2.0 m, it is 1.86 m long and a mere 0.275 m wide. It’s designed for electric mechanics and a 3 or 4 blade rotor head. It is available with the retracting undercarriage pre-fitted and tested. The version I ordered is an epoxy/glass moulding supplied in 2 sections and had the u/c installed. A full carbon fibre fuselage is also available. The kit includes the windows, which can be tinted, as well as carbon fibre formers for the tail section and some fittings.

The fuselage is in 2 parts; the main body and the tail section. The tail section has a flange to match the one on the main body and holes are drilled ready for them to be joined with screws. The canopy frame is very strong and was a perfect fit to the main body. The end section of the tail pylon is a separate piece to allow access for fitting the intermediate gearbox and carbon formers are included for this join. The horizontal tail plane is a one-piece moulding and designed to fit through the tail section.

The retractable undercarriage operates by 4 servos housed in carbon compartments glued to the body and the holes for the skids to retract into are pre-cut. I tested these by using a servo ‘Y’ lead in a switched channel and they worked perfectly locking up and down. I had chosen tinted windows and these arrived ready to cut. Other parts included the exhaust pipes, fixings and scale strakes that fit each side of the retracted skids.

Building the Model

As mentioned mechanics are not supplied although Stefan can advise on what he and other customers have fitted, which include, Vario electric, Thunder Tiger E820, Henseleit TDR2 and PSG Scale mechanics. Note that the model is aimed at electric power… An intermediate 45º/50º tail gearbox is needed as is a tail gearbox and the builder is left to choose their own components and how to fit them.

I had set my heart on using the PSG Dynamics Scale mechanics, choosing the Pro Scale TT version – you may have read about these in the June 2016 issue of RC Heli Action. As it happens, Stefan was able to supply a full set of carbon frames for these mechanics, which I ordered, making life a lot easier. I also ordered the PSG 4-blade rotor head, the swashplate and their Angular Gearbox. PSG offer 6 and 8 mm tube tail drive components so I added a 25 mm boom, 8 mm tube and support bearings, and their heavy duty Claw Couplings, including 6 mm couplings to suit the Vario tail gearbox I intended to use.

I wish I had done my homework better as when I received the fuselage, I realised the PSG Angular Gearbox was too wide to fit inside the fuselage and the Vario metal tail gearbox would stick out both sides. I have since learned that some builders have fashioned side covers to fit over the protruding sides of the Vario gearbox. One again I am jumping ahead in the story, but I want to make the point that with a project like this, you should think the whole thing through and not make any assumptions…

The frame fitting set for the PSG mechanics includes a number of carbon fibre formers that have to be glued into the fuselage. Four 90º carbon ‘L’ sections are then used to support the mechanics.

You will see in the photos that 2 lower carbon formers are pre-fitted between the u/c housings, the front of which supports the centre of the base plate using M3 tapped aluminium blocks. A shaped plywood former has to be glued to the fuselage floor and the base plate also screws to this using M3 insert nuts glued into the former. The base plate locates against the pre-installed front former and so sets the position of the second former, which also has to be glued to the body and the u/c housings. All this has to be done very accurately with the floor laterally and lengthwise parallel to the cockpit, which acts as the datum line for the mechanics. Thus the front mechanics former is glued in place so it is 90º to the floor. I needed to ease this former to fit in the desired position and I then roughened the fuselage surface and removed the shine from the former where the glue would be. I always use cyano with a filling compound to ‘tack’ formers in place so I can double check the position before using Loctite Hysol (9466 A&B in this case) for the permanent bond. Next the rear mechanics former is installed with its 2 spacer plates that ensure the correct spacing, again make sure this it is parallel to the front former!

Four 90º carbon brackets are used to secure the mechanics to the formers using M3 screws and nyloc nuts. These needed to be at their highest and I needed to drill corresponding holes in the side frames to secure them. I have gone into some detail here to make the point that it took a lot of time lining up and double checking before drilling because the mechanics must be parallel to the floor and the main shaft in the correct place!

Tail Drive

Having found that the PSG Angular Gearbox was too big, I searched for a suitable alternative, bearing in mind that it fits inside the very narrow end of the tail section. I decided on the Vario 50º ‘open’ metal gearbox Order #1054, which includes an adapter to fit to a 25 mm tail boom, while the output is an open shaft to take a drive adapter.

Two carbon formers are included in the fitting kit to support a 25 mm tail boom, one is fitted behind the mechanics and can support the tail servo mount, while the other fits in the tail section. The exact position of these formers is determined by the position of the gearbox, bearing in mind that the tail boom with the 8 mm drive shaft needs to be at 90º to the rear of the mechanics. So the whole tail drive train has to be positioned before gluing the formers in place, which led me to the tail gearbox and the pitch mechanism.

First job is to cut off the top of the tail pylon so a gearbox can be fitted! The position of the output shaft is marked, so that marks the cut line – the top section then has to be glued to the rear cover, which I left until later.

As mentioned I had bought a Vario metal tail gearbox but decided this was too big – the top of tail section is 30 mm wide and the Vario unit is too boxy, so another had to be found. A friend, Peter Wales, came to rescue by sending me an X-Cell gearbox that would be far more elegant! I made up a carbon plate to fit into the top of the tail mounding with suitable holes to fit and secure the gearbox. Drive from the intermediate gearbox was a short 8 mm tube with the PSG drive coupler at the bottom and the X-Cell drive adapter at the top.

Next came the tricky part of positioning all the components and gluing in the formers. First the intermediate gearbox was screwed to the boom, which was inserted into the boom from the rear and the smaller former roughly positioned inside the tail section. Next the tail section was screwed to the front using the supplied M4 fixings and the front former was also positioned. The formers were then positioned so the boom was at 90º to the back of the mechanics – note the height of the boom relative to the mechanics did not matter as the PSG tail output shaft can be slid up and down – another benefit of using the PSG mechanics! Having checked the alignment again, I glued the 2 formers into the fuselage.

Positioning the tail gearbox was more straightforward as the angle of the short tail drive shaft was now fixed so it was a matter of positioning the tail gearbox perpendicular to the shaft and gluing the homemade former place.

The tail components were then removed so I could permanently glue the formers in place, again using Hysol. With the tail drive positioned I was able then able to cut the drive tube to the correct length and then the short tube drive to the tail was cut.

Then came the one-piece horizontal stabiliser, position lines are scribed in the fuselage, so I cut these out only to find the boom was in the way! I removed the boom and saw that if I removed the upper surface of the stabiliser, the boom should fit… I did this and glued the stabiliser in place and then used a rounded rasp to enlarge the cut-out until the boom would slide over it.

Carbon formers are supplied for the tail end cap; the one in the end cap can be permanently glued in place, while its mate in the tail pylon has to be removable. I glued small wood blocks to the fuselage to secure the removable plate and added magnets to help hold the tail cap in place.

Another detail that needed thought was securing the tail boom in place and the tail pitch control. The 50º gearbox is a tight fit in the pylon so I simply trimmed the carbon end plate to fit around the gearbox preventing it from rotating. Also a carbon plate is glued to the front of the boom that is then screwed to boom support – this was the very last job because once done, you cannot remove the boom… For the tail pitch, I used Vario boom servo supports to mount the servo on the boom, along with a pitch rod support. A Vario bell crank was fitted to the 50º gearbox to take the pitch control up to the X-cell gearbox.

The previously removed top of the pylon has to be glued to the endcap, which is a fiddle and you have to think about how to hold it in place. I added small guide tabs to hold everything in line and finally fitted a screw in the bottom for extra security.

Other Bits

With so much tricky but satisfying work done, it was a pleasant change to tackle some more straightforward stuff. The canopy frame outline matched the fuselage perfectly and Stefan included some hardware for attaching it, namely some aluminium locating cones and other small fixings. I securely clamped the canopy frame in place and drilled pilot holes for the cone locators. The holes were then opened up so the cone was an interference fit on the body, but oversize in the canopy frame. I then used some plywood plates to locate and glue the cones in place.

A pair of M4 pan head locating screws are then fitted to the bottom face of the fuselage and corresponding slide and lock plates glued to the frame – the photo shows how it works. Finally, and for good measure I fitted magnets to the vertical face of the frame.

Exhaust pipes are supplied, but I decided these would be fitted after painting, so it was now a matter of stripping everything out ready for painting.

Painting and Finishing

There are not many options for colour schemes and as I had chosen the demonstrator to model, that was the colour scheme. With so little original data to work from – essentially a few scanned photos from around 1966/67, the colour and some detail had to be guessed, which I left to the painter, Keith Crawley of P. P. Paintwork (Tel: 07957 968455). I gave Keith a free hand and he made a fantastic of job of adding the final U/C fairings plus some detail that he discerned from the photos, and of course the fantastic paint job.

I had given the final assembly a great deal of thought and all went well, although the tail pitch mechanism caused a few headaches before it operated smoothly and reliably. The windows were carefully cut out and glued in place from the inside. Keith had painted the exhaust for me, so once the mechanics were in place I glued them in place using plywood rings to secure them from the inside.

The PSG mechanics were fitted with a KONTRONIK PYRO 850-50 and geared for 1130 rpm for the rotor head and 5932 rpm at the tail rotor, using 12S LiPo power. The KONTRONIK KOSMIK 200 ESC fits to the underside of the mechanics, so the motor wires could be connected direct to the KOSMIK (I did need to reverse the motor rotation using the KOSMIK software). As usual I fitted an EMCOTEC Safety Power Switch (SPS), in this case a 18V to 70V 100A/200A which was wired direct to the KOSMIK and placed under the mechanics. A serial lead using XT90 connectors was then made to plug into the SPS input and the XT90s locate in the holes in the floor, which is very convenient for connecting the OptiPOWER 6S 8000 mAh LiPo packs I would use.

The mechanics are fitted with XPERT SM-5401 HV servos and I’m using a Bavarian Demon 3X gyro with a JR RG812BX receiver. Before fitting the mechanics, I had set up the controls etc., making sure everything was correct and I was very careful about orientating the gyro. I test fitted the OptiPOWER 6S 8000 mAh packs using the Velcro straps in the pre-cut holes. The CG was a bit rearward so I slid the LiPo packs as far forward as possible and then added some lead weight under the carbon floor plate.

I had ordered a set of Witte 900 mm rotor blades that gives a rotor diameter of 1950 mm. These blades are worth a special mention because they are superb quality being perfectly balanced and finished – I added the aluminium carry case to look after them. In fact, I was so impressed with the blades I later ordered a set of 777 mm for another helicopter! I added a pair of NHP 120 mm tail rotor blades to finish the model. Total flying weight came out at 9.98 Kg.

Flying

First flights were on a very blustery day, and I was pretty nervous, but the sun was shining and Denis was there with a camera. Spooling up showed no vibrations and in fact it was very smooth running and very quiet. Tracking looked good and I sensed the tail control was good, so a little more collective and the Lockheed took its maiden flight. The blustery wind was pushing it around quite a bit, so I landed and increased the rotor head gyro gain, which improved handling – I ended up with the gain at maximum. These first 2 flights proved the integrity of the model and how good it looked in the air with the skid up and down. I did notice that the PYRO and KOSMIK both seemed quite hot to the touch, so this was something to monitor.

The first public outing was the end of June at the Helipad scale fly-in, but with winds over 15 mph, I decided not to fly it. I was then away for a couple of weeks and the next occasion was later in July at the Southwest Heli Fest where I asked Kevin Lever to fly it for me so I could get more photos… The only problem was that he enjoyed it so much I didn’t get chance to fly it myself, but I did get lots more photos and it has his seal of approval, which is good…

This a model that needs a lot of space to fly in – like the original it is potentially very fast, and so can use up a lot of space, which unfortunately has limited my flying time with it. So, to date it has had several test flights including larger circuits, all of which have proved faultless. It to be a lovely model to fly, it looks great in the air and the retracting undercarriage works faultlessly. It is also an eye catcher with many people not knowing the story of the full size machine, while others talk of the early models from the 1980’s – I quickly explain that this a totally new and up to date model – the only similarity is the shape!

I mentioned that the motor and ESC felt hot, so I checked the KOSMIK data that showed the FETs reached 59ºC, which seemed high, but the average battery current draw was 35.5 A. This suggests there is not enough cooling air getting through the model, but I do not want to start cutting holes in the lovely fuselage, so at first I will replace the KOSMIK with a Cool KOSMIK 200 with the fan attached. If it still runs hot, I will need those cooling holes!

Conclusions

Building the Witte Lockheed 286L requires a lot of detailed thought and planning because you are using your choice of mechanics and it is likely to involve using parts from different manufacturers. In my case, PSG mechanics, rotor head and tail drive components, an intermediate tail gearbox from Vario and an X-Cell tail gearbox. This means a lot of trial fitting and as you solve one problem, another tends to appear. This makes it time consuming so it is a big undertaking that culminates in a unique model that will have a lot of ‘you’ (the builder) in it.

This is the first project of this type that I have undertaken and to be honest at times I found myself asking myself if I had the skills and necessary knowledge to do it. However the finished model performs really well and looks stunning so, for me, the model is very special and worth all the time and commitment. I guess it is a bit like flying model helicopters, if it was easy, we would not do it!