The Bristol Type 170 Freighter is a British twin-engine aircraft designed and built by the Bristol Aeroplane Company as both a freighter and airliner.
Its best-known use was as an air ferry to carry cars and their passengers over relatively short distances.
A passenger-only version was also produced, known as the Wayfarer.
The Freighter was developed during the Second World War, having attracted official attention from the British Air Ministry, which sought the development of a rugged vehicle capable of carrying various cargoes, including a 3-ton truck.
Various changes to the design were made to accommodate their requirements but being completed too late to participate in the conflict, the majority of sales of the Freighter were to commercial operators.
In response to customer demand, an enlarged version to maximise vehicle-carrying capacity, known as the Bristol Superfreighter, was developed.
The Bristol Type 170 Freighter was a twin-engine, high mounted-wing monoplane that was developed specifically for the economic carriage of freight by air.
It was a visually distinctive aircraft, possessing a ‘boxy’ fuselage, rounded nose, and a high-set flight deck.
In order to maximise the economic performance of the Freighter, compromises were implemented on other aspects of performance, resulting in a relatively low cruising speed; this was not viewed as being of importance to the role of a freighter and thus not a major diminishing factor.
According to aviation publication Flight, the economics of the Freighter were judged to be a major factor of its market appeal, as well as the wider economic situation of the UK at this time.
Operationally, the Freighter was intended to be employed upon high-frequency short distance routes as opposed to long-haul routes.
Being flown at the low speeds and short ranges for which the aircraft was intended, the fuel economy improvements that would be provided by a retractable undercarriage was outweighed by the increase in structural weight; therefore, it was decided that a fixed undercarriage would be used, which also had the benefits of reduced production and maintenance costs.
The combination of a high-mounted wing and fixed undercarriage was considered to be atypical for the era, and resulted in greater drag than a low-mounted counterpart would have.
The main gear legs, which featured Dowty-built shock absorbers, were supported by an arrangement of strengthened vertical struts, positioned beneath the aircraft’s engines and horizontally from the lower edge of the fuselage.
The lower nose of the Freighter was covered by a pair of large clamshell doors, for easy access to the main hold; as a direct consequence of this arrangement, the unpressurised fuselage was somewhat breezy during flight.
The doors, which are hinged outwards, led into a main hold that had an internal volume of 2,020 cu ft; it was capable of being loaded with heavy payloads, up to a maximum of 350 cu ft per ton.
To better facilitate loading, a built-in hoist is installed on the fixed upper surface of the nose, which reduced the need for airport-based infrastructure.
Fixed restraining points to secure payloads are present throughout the internal space.
On the passenger-carrying Wayfarer variant, the nose-mounted doors were substituted by a fixed shell and the area immediately behind would be used either as a cargo hold or galley.
The flight deck of the Freighter was positioned in an elevated position, directly above the clamshell doors.
In addition to providing a good all-round view for the flight crew, this placement kept the flight deck clear of the loading activity below.
Flight stated of the cockpit: “The control and instrument layout is quite the best we have seen in any Bristol aircraft”.
The major controls are typically comfortable and smooth, while each pilot is provided with a standard blind-flying panel.
Instrumentation fittings differed dependent upon customer specification, but a Sperry Corporation-built autopilot would typically be installed.
The flight deck was typically operated by a two-man crew, a first pilot and second pilot or radio operator; in addition, space was provided at the rear for a third crew member.
The Bristol Hercules 734 radial engines that powered the type, along with all of its major subsystems such as the cowling, oil tank, cooler and control cables, could also be easily detached for servicing; an entire engine replacement could be performed within 90 minutes.
The fuel system is uncomplicated, being contained within a pair of 300-gallon fuel tanks positioned in the interspar bays of the wings; neither fuel tanks or hydraulic pipelines were present in the outer wings.
The only elements needing hydraulic systems were the clamshell doors and flaps.
The electrically controlled carburetion system had three different intakes, each suited to starting the engine under different conditions – these being hot, sub-zero, and temperate climates.
The airframe itself is deliberately simple in its construction, while the use of maintenance-intensive components was kept to an absolute minimum and, where necessary, these were made as accessible and readily serviceable as possible.
Manufacturing of the Freighter was eased by many components being standardised and identical where feasible; this ideology was also applied to elements of the internal structure, such as the longerons, frames, and skin.
The floor of the main hold is covered by wooden panels, designed to be easily replaceable in the event of damage; these were supported by a floor structure of deep transverse beams with a pair of longitudinal strips, strengthened by a support beam.
Another ease-of-maintenance decision was to use cables for the control system where practical, while all flight control surfaces had fabric coverings, which was both light and easy to replace.
Variants
Freighter Mk I Utility transport Series I or Freighter with a strengthened floor and hydraulically operated nose doors. Freighter Mk IA Mixed-traffic variant with 16-passenger seats Freighter Mk IB Variant of Mk I for British European Airways Freighter Mk IC Variant of Mk IA for British European Airways Freighter Mk ID Variant of Mk IA for British South American Airways Wayfarer Mk II Airliner (passenger variant) Series II or Wayfarer.
The nose doors were omitted and additional windows were added. Wayfarer Mk IIA
Variant of Mk II with 32 seats Wayfarer Mk IIB
Variant of Mk IIA for British European Airways Wayfarer Mk IIC
Variant of Mk II with 20 seats and baggage hold Freighter Mk XI
Variant of Mk I with 108 ft (32.92 m) wing and extra tankage. Freighter Mk XIA
Mixed-traffic version of Mk IX Freighter Mk 21
More powerful-engined version. Freighter Mk 21E
Convertible version of Mk 21 with 32 removable seats Freighter Mk 31
Variant of Mk 21 with larger tailfin. Freighter Mk 31E
Convertible version of Mk 31 Freighter Mk 31M
Military version of Mk 31 with provision for supply dropping Freighter Mk 32
Higher-capacity version with fuselage lengthened by 5 ft (1.52 m). Type 179 Freighter
Replacement for Freighter with a twin boom tail, not built. Type 179A Freighter
As Type 179 but with an upswept rear fuselage and a ramp-loading door, not built. Type 179B Freighter
Version of Type 179 with standard tail and powered by Centarus engines, not built. Type 216
Freighter / car ferry replacement of Freighter.
It was intended to be powered by a pair of Rolls-Royce Dart turboprop engines, Not built. Specifications Crew
3 Capacity
22,300 cu ft (630 m3) cargo hold,
16,184 lb (7,341 kg) payload inc fuel Length
68 ft 4 in (20.83 m) Wingspan
108 ft 0 in (32.92 m) Height
21 ft 8 in (6.60 m) Wing area
1,487 sq ft (138.1 m2) Airfoil
RAF 28 (modified) Empty weight
26,910 lb (12,206 kg) Gross weight
44,000 lb (19,958 kg) all marks Fuel capacity
1,170 imp gal (1,410 US gal; 5,300 L) total Powerplant
2 × Bristol Hercules 734 14-cylinder air-cooled radial piston engines,
2,000 hp (1,500 kW) each Propellers
4-bladed de Havilland constant-speed fully feathering metal propellers,
14 ft (4.3 m) diameter Performance Maximum speed
225 mph (362 km/h, 196 kn) at 3,000 ft (910 m) Cruise speed
164 mph (264 km/h, 143 kn) recommended, at 5,000 ft (1,500 m) Range
820 mi (1,320 km, 710 nmi) with 12,000 lb (5,400 kg) payload Service ceiling
23,000 ft (7,000 m) at max. continuous power and 38,000 lb (17,000 kg) Rate of climb
250 ft/min (1.3 m/s) on one engine at fully loaded weight Time to altitude
10,000 ft (3,000 m) in 10 minutes at max continuous power Power/mass
11 lb/hp (6.7 kg/kW) Take-off distance to 50 ft (15 m)
2,500 ft (760 m) in a 5 mph (4.3 kn; 8.0 km/h) wind Landing distance from 50 ft (15 m)
2,300 ft (700 m) in a 5 mph (4.3 kn; 8.0 km/h) wind.
