L-19 Speed 400 Bird Dog

Model Airplane News, Aug 2002 by Fey, Tom

The distinctive Cessna L-19 Bird Dog was purposely built as a military liaison and artillery-spotting aircraft. It first flew In December 1949, barely six months before the Korean War began. Blessed with good pilot visibility, simple maintenance requirements, reasonable performance and outstanding flaps for getting Into and out of tight places, the Bird Dog served a vital milltary role. During the Vietnam War, the L-19 became the 0-1 and was used as a forward air controller (FAC). Armed with a courageous pilot and white phosphorous ("willy pete") rockets, the 0-1 identified targets for the fast-moving F-105s, F-4s and A-4s to attack. The plane and its pilots both proved to be noble, bare-knuckle warriors.

FLYING THE BIRD DOG

With the control movements and CG set as noted on the plan, the 0-1 climbs smartly from a flat-footed, medium-strength hand launch. The plane is stable but responsive, with moderate flight speeds-characteristics that are ideal for a trainer. Level flight can be maintained at roughly 1/2 throttle. The rudder is responsive, so hammerheads are very enjoyable, and loops can be completed from level flight. Stalls are mild and straight-ahead with no tendency to drop a wing or to enter a spin. The suggested aileron throws are good for general flying, but larger throws improve the roll rate. Once power cuts off, the nose drops about 15 degrees, but a little backpressure on the elevator makes for a flat glide. Landing the Dog is very easy, with or without power; however, the small-diameter wheels need a flat (or at least, a very well-groomed) surface to prevent nose-overs.

Note: the 0-1 won't maintain altitude in knife-edge or inverted flight. It takes a while to get around a roll, and it slops through snap rolls, but this utilitarian Cessna is not really designed for these tasks.

The popularity of Speed 400 aircraft and the soundness of the Bird Dog design were a combination that designer Gus Morfis really embraced. In addition to the jaunty good looks, there is plenty of room for 4-channel operation, and the external battery well makes battery changes fast and uncomplicated. Building the Cessna is pleasantly straightforward, but weight control is essential, so use lightweight balsa to ensure good performance. Except where noted, we used aliphatic glue (Pica Gluit) to build the model.

First, build the fuselage bulkheads over he plan from 1/16-inch sheet and the motor mount from 3/32-inch plywood. The battery floor is a lamination of 1/32-inch plywood over 1/16-inch balsa sheet using thick CA for good coverage without warping. With the plan as your guide, use a felt-tip pen to mark the bulkhead positions, the battery floor and the fuselage doublers on the fuselage sides. For those who haven't made this mistake yet, be sure to make one left side and one right side. Glue the upper gear rail onto the 1/32-inch plywood fuselage doubler and then glue the doubler to the fuselage side with thick CA. Use aliphatic glue to attach the triangle stock, 1/4-inch stock and longerons to the sides. Test fit (don't glue!) bulkhead nos. 2 and 3 into their slots on the fuselage sides. Once you've achieved a good fit and accurate alignment, glue the fuselage sides and bulkheads 2 and 3 together, and let them dry.

Next, glue the battery floor into place (plywood surface facing down), and then add vertical grain 1/32-inch balsa to the inside of the battery well as shown on the plan. After that, epoxy the motor mount into the nose and glue bulkheads 4 and 5 into place. Leave an 1/8-inch gap at the fuselage end, as it will later accept the rudder tail post. We used two balsa rails mounted across the fuselage to hold the rudder and elevator servos. Install your elevator and rudder-control pushrods and then sheet the upper and lower fuselage surfaces with cross-grain balsa sheet.

Bend the landing gear from 3/32-inch-- diameter music wire, and use steel wire to "sew" it to the 3/32-inch plywood gear mount. We used Dave Brown 1 1/2-inch foam wheels shimmed with aluminum tubes to mate the wheels to the wire axles. The gear will later be epoxied onto the upper rails and secured by gluing in the lower plywood rails; this is almost the final step after the fuselage has been covered with MonoKote. Build the tail feathers from 1/8-inch sheet and square stick stock. We used MonoKote hinges on all the control surfaces and made control horns from ihe-inch plywood.

THE WINGS

The wing is built in two panels, so remember to tilt the center rib of each panel about 1 1/2 degrees to incorporate the wing dihedral. The trailing edges of the outer three ribs are shimmed up as noted to provide washout. The wing is constant chord in the center section, but it tapers after mid-span. We simply cut through the leading-edge stock on a diagonal and then sanded in the proper angle to get a close, strong fit. The taper for the trailing edge is accomplished by varying the chord on the ailerons as shown on the plan. The forward section ahead of the spars is sheeted with 1/32-inch balsa. We used some 1/8-inch-square stock to fatten the upper perimeter of the fifth rib where the wing chord starts to taper; this provides a solid area to butt-join the upper wing sheeting.