The successful
German Jacobs Weihe sailplane of 1938 strongly influenced several
wartime and postwar designs such as the
Italian CVV-6 Canguro and the
British Slingsby Gull 4 and
Sky. The Arsenal 100 was also Weihe based, with the intention of improving on that design. Work began before the war within a small design group named the Groupe de l'Air, led by Raymond Jarlaud. The wings of the two aircraft are similar in design and construction. Both have spans of and are straight tapered with rounded
wing tips, although the Air's taper ratio (
wing root chord to tip chord) is higher, resulting a slightly greater
aspect ratio. Some later Air 100s have squared-off tips terminated in streamlined "salmons". Both wings use the Göttingen 549
airfoil inboard of the tips, though the Air's roots have a thickened version. They are wooden single spar structures,
plywood covered ahead of the spar and
fabric covered behind. The Air 100 has slotted
ailerons to improve roll rates and, inboard, has Schempp-Hirth parallel-rule
airbrakes mounted immediately aft of the main spar; the Weihe's DFS style brakes had never been very effective, largely because their design placed them further aft on the wing where space did not allow them to open fully. The tail units of the two types are also similar, with ply covered fixed surfaces and fabric covered control surfaces. The Air 100 has a broader chord fin and there are detailed differences in shape, but both place a broad, curved
rudder on a hinge roughly in line with the
elevator trailing edge. There are significant differences in the fuselages, though both are rounded, ply covered structures. The Weihe has a relatively slender rear fuselage, achieved by placing the wing high on a pylon behind the cockpit. In order to improve the aerodynamics of the wing-fuselage junction the Air's designers deepened the fuselage and mounted the wing at
shoulder height. The prototype had no
dihedral but this is used on production aircraft. The cockpit canopy is higher, more curved and with fewer frames on the post-war design. Originally the Air 100 landed on a skid and tail bumper but on production aircraft there is a fixed
monowheel under mid-chord, with the rear part of the skid removed. The Air 100 flew for the first time on 10 June 1947. The production aircraft that followed the two prototypes were 43 kg (95 ) heavier empty. ==Operational history==