# Hurel-Dubois Miles HDM.105

The Hurel-Dubois Miles HDM.105 was a transport aircraft fitted with very high aspect ratio wings for research purposes, building on research carried out with the Hurel-Dubois HD.10, and a stepping point to the planned production HDM.106 Caravan. The HDM.105/HDM.106 provided the starting point for the design of the Short SC.7 Skyvan.

## Design and development

Maurice Hurel [fr], a French aircraft designer, became a champion of very high aspect ratio wings in a bid to significantly reduce induced drag, similar to the "Davis wing" of the Consolidated B-24 Liberator, but with much higher aspect ratios. After testing his wing design on the diminutive HD.10, Hurel was ready to progress to a full size transport aircraft, a joint venture between F.G. Miles Ltd. and Hurel-Dubois [fr], fitting a Miles Aerovan with a very high aspect ratio wing and carrying out comparison tests.
The HDM.105 utilised the fuselage, tail unit and engines from Miles Aerovan Mk.4 G-AOJF, fitted with a Hurel designed 75 ft 4 in (23 m) span 20.5:1 aspect ratio wing of NACA laminar flow sections, supported on aerofoil section lifting struts. The wings were fitted with double-slotted flaps actuated by Miles electric actuators from the original Aerovan. Roll control was by differential ailerons and inter-connected upper-surface spoilers. With no room for fuel in the slender wings, 13 imp gal (16 US gal; 59 L) fuel tanks were fitted in the vertical undercarriage strut fairings.

## Operational history

The HDM.105, with B-class registration G-35-3 (subsequently re-registered G-AHDM), was first flown on 31 March 1957 by I.A. Forbes, but was later damaged beyond repair in a landing accident at Shoreham on 28 June 1958 and dismantled.

## Variants
### HDM.106 Caravan

Following the successful testing of the HDM.105 the joint company H.D. et M (Aviation) Ltd, was established to exploit derivatives. The HDM.106 Caravan was to have been an all-metal 8,000 lb (3,629 kg)transport aircraft, with 75 ft (23 m) span wings, powered by 2x 290 hp (216 kW) Lycoming GO-480, 2x 340 hp (254 kW) Lycoming GSO-480B or 2x 320 hp (239 kW) Turbomeca Astazou I engines, but the HDM.106 did not progress beyond the drawing board with H.D. et M (Aviation) Ltd.
The design for the HDM.106 was sold to Shorts who developed it into the very successful Short SC.7 Skyvan, but with a much reduced, moderately high, aspect ratio of 11:1.

### HDM.107 Aerojeep

The H.D.M.107, known as the Aerojeep, was a military version of the HDM.106 to a STOL light transport requirement of the US Army, to be powered by two 800 shp (597 kW) Lycoming T53 turboprop engines.

### HDM.108

An enlarged HDM.106 designed by Hurel-Dubois.

### Miles M.111

The Miles M.111 was proposed as a light single-engined transport utilising the outer wings and struts of the HDM.105, powered by a single 320 shp (239 kW) Turbomeca Astazou turboprop engine.

## Specifications (HDM.105)

Data from Flight : Foretaste of the Caravan - HDM.105 handling HDM.106 prospects, Jane's All the World's Aircraft 1958-59, Miles aircraft since 1925
General characteristics
* Crew: 2
* Capacity: up to 9 passengers or freight
* Length: 10.46 m (34 ft 4 in)
* Wingspan: 22.96 m (75 ft 4 in)
* Height: 4.24 m (13 ft 11 in)
* Wing area: 25.7 m$^2$ (277 sq ft) wings only, 36 m$^2$ (390 sq ft) including struts
* Aspect ratio: 20.5:1
* Airfoil: root: NACA 63$_4$-420; tip: NACA 63$_1$-412
* Empty weight: 1,460 kg (3,219 lb)
* Gross weight: 2,799 kg (6,170 lb)
* Fuel capacity: 120 L (26 imp gal; 32 US gal) in left and right vertical undercarriage strut fairings
* Powerplant: 2 × Blackburn Cirrus Major III 4-cylinder inverted air-cooled in-line piston engines, 116 kW (155 hp) each
* Propellers: 2-bladed Fairey fixed-pitch propellers
Performance
* Maximum speed: 204 km/h (127 mph, 110 kn) at sea level
* Cruise speed: 187 km/h (116 mph, 101 kn) at 3,000 ft (914 m)
* Service ceiling: 4,900 m (16,200 ft)
* Rate of climb: 3.34 m/s (657 ft/min)
* Rate of climb on one engine: 0.3 m/s (59 ft/min)
* Take-off run: 260 ft (79 m) minimum
* Take-off distance to 15 m (49 ft): 590 m (1,940 ft)