Spitfire Mk IX b
Spitfire IX: Fourth major production fighter variant (Supermarine
Type 361), combining Mk VC airframe with two-stage two-speed Merlin 60
series engine but lacking other improvements designed for (later)
Supermarine Spitfire VIII. Early Merlin 60 and 61 flight-tested in
Supermarine Spitfire III (from August 19, 1941) and a Supermarine Spitfire
IA, followed by conversion by Rolls-Royce of two Mk VCs to Mk IX
prototypes with Merlin 61s early-1942. Further 282 conversions of Mk V
airframes by Rolls-Royce; production totals 5,095 by CBAF and 561 by
Supermarine. Service use began June 1942 in No 64 Sqn. Early standard
aircraft had 'C' wing armament, standard wing span, Merlin 61 and
provision for wing and fuselage bomb racks. Later, designations used to
differentiate altitude rating of engine: Supermarine Spitfire LF Mk IX
with Merlin 66, Supermarine Spitfire F Mk IX with Merlin 61 or 63 and
Supermarine Spitfire HF Mk IX with Merlin 70. Broad-chord, pointed-tip
rudder became standard later, as did compact Aero-Vee tropical filter.
Late-production CBAF Mk IXs had cut-down rear fuselage with 360-deg vision
canopy, and Supermarine Spitfire IXE designation (with LF, F or HF prefix)
indicated new wing armament of two 20-mm cannon and two 0.50-in (12.7-mm)
machine guns. More than 50 RAF and Commonwealth squadrons flew Supermarine
Spitfire IXs, primarily in European theatre, and 1,188 Mk IXs were
supplied to the Soviet Union in 1943-44; at least one Mk IX was modified
in Russia to two-seat training configuration. A small number of
Supermarine Spitfire IXs supplemented Mk Vs in USAAF service in Twelfth
Air Force. Max speed, 408 mph (657 km/h) at 25,000ft (7,620 m). Time to
20,000ft (6,100 m), 5.7 min. Initial climb, 3,950 ft/min (20.1 mlsec).
Service ceiling, 43,000 ft (13,106 m). Range, internal fuel, 434 mis (698
km). Empty weight, 5,634 Ib (2,556 kg). Gross weight, 9,500 Ib (4,309 kg).
Span, 36 ft 10 in (11.23 m) or 32 ft 9 in (9.80 m). Length, 31 ft 1 in
(9.47 m). Wing area, 242 sq ft (22.48m2).