Marsden Skylark


Design of the all metal, T tail, side by side two place Skylark began in January 1999, with the first flight on 10 March 2000. After the first flight, all that was required was a change to the incidence on the horizontal tail.

The Skylark is basically a 6061-T6 aluminium structure aircraft with 0.016 2024-T3 Alclad in the control surfaces. Winglets, engine cowling, tips and main landing gear legs are composite. The wing is tapered with the same wing section across the entire span. A channel type spar, located at 38% chord, is 9 in high and reinforced at the root. It tapers to 7 in at the tip. Each wing panel is fitted with six ribs stamped from 0.025 in 6061 sheet and has three full span skins. Wings are bolted to the fuselage carry-through spar.

Seven foot span, 7.25 in flaperons actuate the flap function mechanically by a handle below the centered throttle quadrant. They reflex (move up) 10 degrees for cruise.

The wing employs an IARV 419 airfoil that was designed by Stephen Marsden. It is a high lift, laminar flow profile specifically designed not to be sensitve to surface roughness due to ice, rain, and snow.

The fuselage is a semi-monocoque structure with three formers aft of the cockpit, which is 43 in wide and has dual controls. A 4.25 cu.ft baggage area is behind the seats. The stabiliser and elevator have a 9 ft span each.  A 48 in electrically operated trim tab is installed on the left side of the elevator. The fin is reinforced at the root. Rudder height is 50 in. All of the tail control surfaces are D-cell structures with ribs but no spars. The elevator has six ribs, and the rudder has three.

Main gear legs carry Cleveland wheels and brakes, with 5.00x5 McClreary tires. The nosegear castors, employing a 4130 square steel leg with a spring shock absorber and a 5.00x4 Lamb tire. Main gear tread is 79 in, and wheelbase is 48 in.

Two 14.5 USG welded aluminium fuel tanks are located behind the wing spar, starting at the root and extending 35 in.

Skylark has double tip winglets. As part of the development program, a single winglet was added after the first flight, positioned at the front of the tip. It did assist tip airflow and split the vortices  in two parts. Marsden deduced that dual winglets would work better. He added a second winglet, canted out at 45 degrees, that splits the vortices into three parts. This increased effectiveness about 50% over the single winglet.

For takeoff, flaps are set 10 degrees down. On approach, 20 degrees flap are set for landing for better visiblity. The aileron differential is 10 degrees up and 15 degrees down from whatever the flap angle is set.
Downwind approach is at 80 mph, reducing to 70 on base and final, with a touchdown speed of 54 mph.

Engine: Rotax 912, 80 hp
Prop: CSC wood, ground adjustable 68 in
hp range: 85-150
Wingspan: 22 ft
Wing chord: 48 in
Wing area; 92 sq.ft
Empty weight; 655 lb
MAUW: 1200 lb
Fuel capacity: 2 x 14.5 USG
Max level speed; 130 mph
Stall 20 deg flap: 50 mph
Cruise 75%: 120 mph
Fuel burn at 75%: 4 USGph
Econ cruise: 90 mph
Fuel burn at econ cruise: 2.5 USGph
Stress: +6 / -4
Takeoff run; 500 ft
Takeoff speed: 52 mph
Climb rate: 650 fpm at 75-80 mph
Vne: 210 mph
Range at 120 mph: 700 mile
Landing distance: 500 ft