The Tern high perfomance single-seater was designed by Mr W. Terry Miller of Furlong, Pennsylvania, for amateur construction and the prototype, which was built in a total of 1,180 working hours, made its first flight in September 1965.
An improved version, known as the Tern II, made its first flight in August 1968; this featured a wing span increased by 4 ft 6 in to 55 ft 6 in, increasing the aspect ratio from 20 to 22, and giving an improved best glide ratio and minimum sinking speed. During 1968 brake parachutes were fitted to the prototype Tern, and two types of these were later made available for installation in both versions of the Tern in the base of the rudder, namely a 6 ft diameter cross parachute or a 5 ft diameter guide surface parachute.
By May 1970 nearly 100 Terns and 12 Tern IIs were under construction not only in the USA, but by amateurs in Africa, Australia, South America and Canada.
Of conventional all-wood construction, the Tern has unswept cantilever shoulder wings which are two piece two-spar spruce structures, entirely plywood covered. There are no flaps and the plain ailerons are also all wood; there are wooden spoilers in the wing lower surface used for approach and glide slope control. The semi-monocoque wooden fuselage has a plastic-reinforced glassfibre nose and plywood skinning aft of the cockpit. The cantilever all-wood tail unit has modified NACA laminar flow sections and special hinge-line contours to reduce drag and increase control effectiveness at large angles of deflection; there are no elevator or rudder tabs. Landing gear consists of a non-retractable monowheel forward of the eg housed in a streamlined pod, and skids under the nose and tail; there is a brake lever for applying pressure directly to the tyre. The pilot sits in a semi-reclining seat under a three piece canopy, the centre portion of which hinges sideways for entrance and exit, and radio can be fitted.
One Tern belongs to the National Soaring Museum.
Miller Tern 2
Wing span: 15.54 m / 51 ft
Wing area: 12.08 sq.m / 130 sq.ft
Empty Weight: 215 kg / 475 lb
Payload: 102 kg / 225 lb
Gross Weight: 317 kg / 700 lb
Wing Load: 26.24 kg/sq.m / 5.4 lb/sq.ft
L/DMax: 34 93 kph / 50 kt / 58 mph
MinSink: 0.64 m/s / 2.1 fps / 1.24 kt
Aspect ratio: 20
Airfoil: Wortmann 61 Series
Span: 55 ft 6 in
Length: 21 ft 3.5 in
Height: 5 ft 0 in
Wing area: 140 sq ft
Aspect ratio: 22.0
Empty weight: 550 lb
Max weight: 800 1b
Maxspeed: 120 mph (smooth air)
Max aero-tow speed: 88 mph
Min sinking speed: 1.95 ft/sec at 48 mph
Best glide ratio: 38:1 at 60 mph