damage that was inflicted by heavy landings on carrier decks: a problem that continued even with the strengthening introduced by the Mk II. The Seafire had a narrow undercarriage track, which meant that it was not well suited to deck operations. The many modifications had shifted the centre-of-gravity aft, making low-speed control difficult and the aircraft's gradual stall characteristics meant that it was difficult to land accurately on the carrier, resulting in many accidents. Other problems included the basic Spitfire's short range and endurance (fine for an interceptor fighter but not for carrier operation), limited weapons load and that it was dangerous in ditching. The first Seafire variant to overcome many of these problems was the Mk XVII with its new undercarriage design, reinforced structure and extra fuel tanks, although there were still some compromises and it entered service well after the war was over. The low point of Seafire operations came during Operation Avalanche the invasion of Salerno in September 1943. Of the 106 Seafires available to the British escort carriers on 9 September only 39 were serviceable by the dawn of D-Day plus Two (11 September). Part of this was attributed to the flat, calm conditions present, which meant that there had not been enough headwind in order to adequately slow down the Seafires on landing. Many aircraft missed picking up the arrestor wires and flew into the crash barriers while others had their arrestor hooks pulled off the fuselage because they caught the wires at too high a speed. In spite of these problems, the Seafires (especially the L Mk IIs and L Mk IIIs, with their low altitude rated Merlin engines) were used to patrol the vicinity of the carrier fleet as protection against low altitude attackers, while the longer ranging fighters, such as the Grumman F6F Hellcat, took on a similar role further out and at higher altitudes. The Seafire II outperformed the A6M5 Zero at low altitudes when the two types were tested against each other. Contemporary Allied aircraft which had been specifically designed for carrier use, such as the Grumman F6F Hellcat, were considerably larger, more robust and generally more powerful. The more powerful Seafire III enjoyed better climb rates and acceleration than these other fighters. Late-war Seafire models equipped with Griffon engines enjoyed a considerable increase of performance compared to their Merlin-engined predecessors. The Griffon-powered Seafires had some serious faults, the main