Shipbucket

I echo this criticism (of the design, not the drawing!) with a question: why are the mains even this long? Rough pixel-counting would suggest a nearly 2m prop clearance on the ground, which seems excessive in light of the compromises it forces on loading and unloading.

Can it be due to the under the wing-wheels, that they can't be shorter for the spring to work as attended. If it's mounted where I think it is mounted...

Great additions.

As a minimum-change design the modifications were all to the tail section for the loading system, so the main undercarriage remained the same as the standard Hastings. Building in a completely new undercarriage leg system to allow raising and lowering was probably not in any way feasible with the design brief or resources and time frames available.



With a tailwheel aircraft, the ground attitude and the flight, take-off and landing attitudes are completely different. To get airborne the aircraft must raise the tail until the whole aircraft is close to horizontal before unsticking. The picture above shows the approximation of that, showing that the change in attitude brings the propeller discs closer to the ground. Factoring in compression of the shock struts on the landing gear that work to absorb impacts, and the factoring in of additional clearances in case piloting is not at test pilot standards - nose too low or excessive wheel braking causing the nose to dip below the optimal - and the +/- 1 metre prop clearance can't be reduced any more.

H.P.79 Hermes III

Before the design of the Hermes II was even finalised, a turbo-prop Hermes with Theseus engines was considered for an additional prototype.



At this stage the Hermes II was still a tailwheel design, so the initial Theseus engined Hermes would also have mounted a tailwheel, and would still have been no more than another variation to the Hermes II design.
Later that year with the change to a nosewheel design for the Hermes, the Theseus engined model's design was also upgraded to a nosewheel with the same long nose gear with the engines being mounted underslung on the wing.
In June the Theseus Hermes was allocated its own model number and name, becoming the H.P.79 Hermes III.
With further development of the basic airframe to become the Hermes IV, the engine system development of the III was later used to create the Hermes V.

Specification 2/47 Hermes variants

In September 1946 the designation H.P.81 Hermes IV for the advanced Hermes II for BOAC was allocated and design work commenced, and in January 1947 the H.P.82 turbo-prop Hermes V was allocated. While this design work was only just started Specification 2/47 was issued for a Constellation replacement for BOAC, tenders for which had to be submitted by April 1947. HP initially submitted three variants of the Hermes, but apart from HP model numbers none were allocated names.



The H.P.83 was a Hermes with Bristol Centaurus 663 piston engines, and a new double slotted wing flap.



The H.P.84 was a Hermes with Bristol Proteus turboprop engines and the double slotted flaps.



The H.P.85 was the most advanced model. It featured a new single-spar wing with the double slotted flaps, and two Coupled Proteus engines, of the type developed for the Bristol Brabazon Mk.II and Saro Princess.



When HP discovered that Bristol was also submitting a design for a Constellation with Centaurus engines, they then urgently drafted a Hermes design with the new single spar wing of the H.P.85 and the Centaurus engines of the H.P.83, to become the H.P.86.
In the end, the HP designs were beaten by Bristol with their 175 which became the Brittannia. However aspects of these designs were applied into the Hermes IV and V, especially the reductions in weight and improvement in performance.

Excellent additions!

H.P.81 Hermes IV

The Hermes IV was offered to BOAC in September 1946 as an improvement on the Hermes II. BOAC agreed to the nosewheel layout, but required twin mainwheels and nosewheels, and also requested the turbo-prop version as the Hermes V. Another requirement was for a forward galley, which necessiatated moving the wing 20 inches forward to maintain balance.



Due to the required modifications, the original batch of Hermes IV aircraft were too heavy and BOAC initially declined acceptance. Eventually BOAC agreed to take the aircraft on the proviso that weight reductions were achieved before acceptance for fleet service. After the problems with the Avro Tudor, BOAC had now adopted a hard line with new aircraft types. Finally the 10th production aircraft was accepted in July 1950 to become the flagship "Hannibal", with the rest of the fleet being allotted names originally bestowed on the pre-war H.P.42's.
The rejected Hermes aircraft were leased to Airwork for trooping contracts, primarily to the Suez. For political reasons these aircraft were allocated military serial numbers.
With difficulties obtaining 115 octane fuel, Hermes aircraft were gradually re-engined with Hercules 773 engines able to take 100 octane fuel, and were then renamed as Hermes IVA. As fuel supplies after 1957 most aircraft reverted back to Hermes IV standard.
Charter operators acquired the Hermes IV as it was phased out of airline service, being operated by several British charter companies. Several aircraft were also subcontracted out to smaller airlines in other countries on short term contracts, but all aircraft returned to Britain.

H.P.81 Hermes IV last surviving airframe

With airline consolidation in Britain, Airwork became British United Airways, then British Caledonian Airways, before finally becoming a part of British Airways.



The last operational Hermes IV was inherited with these developments, but once it had finished its flying career it was not scrapped. Instead it had its wings removed and was turned into a cabin crew trainer, and was continually repainted in fleet colours as its corporate identity evolved. Finally retired, it has now been repainted in classic BOAC colours and is in museum storage.

Splendid additions.