to cope with the greater weight. On subsequent Mk XVs a new form of "sting" type arrestor hook was used; this version was attached to the reinforced rudder post at the rear of the fuselage and was housed in a fairing below the base of the shortened rudder. A vee-shaped guard forward of the tailwheel prevented arrestor wires getting tangled up with the tailwheel. 390 Seafire XVs were built by Cunliffe-Owen and Westland from late 1944. Six prototypes had been built by Supermarine. One problem which immediately surfaced was the poor deck behaviour of this mark, especially on take-off. At full power the slipstream of the propeller, which swung to the left (as opposed to the Merlin, which swung to the right), often forced the Seafire to swing to starboard, even with the rudder hard over on opposite lock. This sometimes led to a collision with the carrier's island. The undercarriage oleo legs were still the same of those of the much lighter Merlin engined Spitfires, meaning that the swing was often accompanied by a series of hops. As an interim measure it was recommended that pilots avoid using full power on take-off (+10 lb "boost" maximum was recommended). There were also problems involved with this swing being strongly accentuated in the event of an asymmetric firing of the RATOG equipment. In the event, none of the "first generation" Griffon-engine Seafires were to use RATOG at sea unless they were ranged forward of the first crash barrier on deck. The Seafire F Mk XVII was a modified Mk XV; the most important change was the reinforced main undercarriage which used longer oleos and a lower rebound ratio. This went some way towards taming the deck behaviour of the Mk XV, reduced the propensity of the propeller tips "pecking" the deck during an arrested landing and the softer oleos stopped the aircraft from occasionally bouncing over the arrestor wires and into the crash barrier. Most production XVIIs had the cut down rear fuselage and teardrop canopy (the windscreen was modified to a rounded section, with narrow quarter windows, rather than the flat windscreen used on Spitfires) and an extra 33 gallon fuel tank fitted in the rear fuselage. The wings were reinforced, with a stronger mainspar necessitated by the new undercarriage, and they were able to carry heavier underwing loads than previous Seafire variants. 232 of this variant were built by