ME-246 - modified Pica Duellist
The balsa airframe was covered with one layer of 0.6 oz. fiberglass cloth and epoxy laminating resin, followed by an automotive spray primer. Cheveron Perfect paints were applied using a spray gun for the basic colors and an airbrush for the camouflage mottling on the fuselage sides and vertical stabilizers. Insignia and lettering were masked with a
frisket, and then airbrushed. Panel lines were drawn in using a flexible straight edge, and a medium, .05 mechanical pencil. Oil stains and rust streaks and general wind blown weathering and grime were airbrushed in artist's acrylics. In retrospect, the airbrushed weathering was applied too liberally for close inspection - better to view it when it's in flight. "Chipped paint" is painted on with a fine tipped brush before the final clear coat. Unfortunately, the nitromethane has crazed the primer in the areas immediately surrounding the engine cowlings. An epoxy primer would have been a better choice here.
This pic of a single engined fly-by was taken by Chris Rampoldt at the B.A.R.C.S field. This was the 4th single engined flight.
Single engine performance is quite good, somewhat like an under-
powered sport model. To date, the model has flown on a single engine four times
The first time was on final approach when both engines were at or near idle. There was no noticeable change in flight behavior since the engines were providing minimal thrust when the left engine quit. The model was already established in a stable glide. Cause: idle set too low.
The second time was during a 1/3 throttle fly-by at an altitude of about 8-10 feet. The right engine had quit on the downwind leg of the pattern (altitude of about 20 feet), but went un-noticed until after right turns to the base leg and the final upwind leg. After a gradual throttle-up to full with no ill effects, the model was nervously turned right (away from the pits area, but towards the dead engine) and back to the downwind leg. At full throttle, the Me-246 was able to climb back up to a decent altitude to set up for a landing. Turns towards a dead engine are generally not advised, but in this case, the model was well above it's minimum single engine controllable airspeed and a turn towards and over the pits area was not an option. Cause: both the center main tank and right header tank had run dry - fuel starvation.
The third time was scary. The model was approximately 100 yards out, 150 feet up and in a slow, steep and decelerating climb at 1/3 throttle. When I opened the throttles to 100%, the left engine blew out it's glow plug (found out later). First indications of a problem was slight nose up pitch coupled with a pronounced yaw to the left. This quickly developed into a left-handed spin with a nose down attitude of approximately 45 degrees. The throttles were immediately brought back to idle and the control surfaces released to neutral. -no change, model completes 2nd revolution. Down elevator was applied, no change, model completes 3rd revolution. Opposite rudder was added, model exits spin after completion of 4th revolution. Recovered from the dive with less than 15 or 20 feet to spare (I think). Airspeed looked good, so the throttle was opened enough to stretch the glide to the runway although I was prepared to set her down short out in the brush.
The fourth time was similar to the second time. Cause: fuel starvation.
The cause of the 4 engine out situations have been determined and have all been situations easily avoided (set idle stop correctly, land before you run out of fuel, re-tighten new glow plugs after 1st run). This model has flown countless times now. There're many myths and theories floating around about twin engined models, some encouraging, some discouraging, most true - if they are taken in full context.