H.P.82 Hermes V
Ordered and completed simultaneously with the initial piston engined H.P.81 Hermes IV, were two prototype turbo-prop H.P.82 Hermes V. These aircraft were not a continuation of the Hermes III design, but a new development of the Hermes IV.
The Hermes V was basically a Hermes IV with new engines and nacelles. Deicing was planned to be from heat exchangers from the engines, but as the output was insufficient, the first prototype reverted to the deicing sleeves fitted to the Hermes IV.
The second prototype differed from the first by being fitted with the double slotted flap, designed originally for the Constellation-replacement designs, and being fitted with a new thermal de-icing system.
The Hermes V was the largest and fasted turbo-prop airliner, but ongoing problems with the engines and exhausts led to the crash of the first aircraft which was unrepairable and written off. The technology of the engine systems was just too unreliable (the propellers were limited to 10 hours in service) for the Hermes V to be a viable airliner.
As the Theseus engines were the weakness of the Hermes V, having a high fuel consumption, low reliability and doubtful production status, an alternate engine was essential. Several variants were investigated, with two reaching design status. With the Napier Eland engine, the design became the Hermes VA, and an enlarged version with Proteus engines becoming the Hermes VB.
The VB was designed as the heaviest Hermes, fitted with large diameter propellers (requiring taller landing gear), increased wingspan and an enlarged tail.
With the development of the Britannia interest in the turbo-prop Hermes waned and the designs were not progressed.