the starboard upper engine cowling. The carburettor air intake on early to mid-production Spitfire IXs was a different shape from those of single-stage engined aircraft; they were shorter and had a wider air inlet. From 1943, an "Aero-Vee" tropical filter in a long, streamlined fairing was introduced for the carburettor air intake. This was fitted as standard to all Mk VIIs, VIIIs, PR Mk Xs and Mk XVIs, on mid to late production Mk IXs, and to most PR Mk XIs. A new 10 ft 9 in (3.27 m) diameter four-bladed Rotol propeller was fitted, housed in a pointed spinner. The exhaust units were changed to six "fishtail" stacks per side. Under the nose, the three piece cowling was changed to a one piece layout. The oil tank was no longer a part of the cowling structure. Early Mk IXs had a teardrop shaped blister (a bulge) for a Coffman engine starteron the lower starboard side cowling, just behind the propeller. This was replaced by an improved electric starter on most two-stage Merlin powered Spitfires and, from late 1942 the blister like bulge was seen on only a few aircraft. The Type C wing was fitted as standard. Some mid and most late production Spifire Mk IXs and all Mk XVI were fitted with the Type E wing. While Spitfire IXs converted from Mk Vcs had the large teardrop fairings on the upper surfaces, on the majority of Mk VIIs, VIIIs, IXs and XVIs the teardrop shaped blisters covering the Hispano feed motors were reduced in size and more streamlined than those on the Mk Vc. According to A.P 1565J P & L (Spitfire IX, XI and XVI Pilot's Notes) the red painted undercarriage indicator rods, which projected through the tops of the wings when the undercarriage was down, were used only on early production Mk IXs. When fitted these rods supplemented an "Electric visual indicator" mounted on the instrument panel. The indicator rods seemed to be fitted on all Mk VIIs and VIIIs, supplementing the electric visual indicator. A light for the retractable tailwheel was mounted on the instrument panel, just below the main visual indicator. Because the intercooler required a radiator, the radiator under the starboard wing was halved in size and the intercooler radiator housed alongside. Under the port wing a new radiator fairing housed a square oil cooler alongside the other half-radiator unit. When the engine