Vickers Vellore. The Vickers Vellore was a large biplane designed as a freight and mail carrier, in single-engined and twin-engined versions, which saw limited use as freighters and long-range experimental aircraft. A final variant with a broader fuselage, the Vellox, was completed as an airliner.

Development
The Vickers Vellore, named after the Indian city of Vellore, was a response to Air Ministry specification 34/24, which called for a civil mail and freight carrier. It was a very large single-engined two-bay biplane, metal framed and fabric covered. The wings were of equal span with a slight stagger and sweep and braced with parallel interplane struts. Both upper and lower wings carried balanced ailerons. There were gaps both above and below the fuselage, whose diameter increased behind the radial engine. The crew sat side by side in an open cockpit just in front of the wings, giving an excellent view. Behind them was the cargo hold, with the fuselage tapering towards the biplane tailplane which was fitted with balanced elevators. There were four slender finless rudders, roughly equally spaced between the two tailplanes. The undercarriage was a simple fixed split-axle arrangement, plus a sprung tailskid.

The Vellore I, fitted with a  Bristol Jupiter IX, flew for the first time on 17 May 1928. It appeared at the RAF Hendon display in June that year, then went on to RAF Martlesham Heath for tests in October. These it passed with flying colours, its performance better than predicted and it demonstrated good reliability. In early 1929 the Vellore was fitted with an Armstrong Siddeley Jaguar VI and extra fuel tanks in the freight compartment for a flight to Australia. Leaving Lympne on 18 March 1929 with a full  load including the extra fuel, the Vellore II (or Jaguar-Vellore) made Benghazi in stages before engine trouble caused a forced landing. After spares arrived, the flight continued until the engine malfunctioned again over the Timor Sea, and the Vellore was wrecked in trees near the Cape Don lighthouse at the western extremity of the Cobourg Peninsula on the Australian mainland. The two Australian crew were unhurt.

The Vellore III was a twin-engined development that was fitted with a pair of  Jupiter XIFs with Townend rings and mounted in nacelles cowlings midway between the wings. 

The lower wing was slightly decreased in span so the outboard interplane struts leaned outwards. The other alteration was to the main undercarriage, which was now mounted under the engines, providing a wide track . The Vellore III could also be operated as a seaplane with single-step floats replacing the wheels. A second twin-engined Vellore was built, differing only in having slightly higher compression Jupiter IX engines and eventually known as the Vellore IV. This aircraft was in use until early 1935, transporting troops and stores between Martlesham and nearby Orfordness.

The last aircraft of the series was based on a partially completed third twin-engined Vellore airframe, fitted with a new, broader fuselage with an enclosed cockpit, and cabin windows for the passenger compartment, and was powered by  Bristol Pegasus IM3 radials. This variant was renamed the Vickers Vellox, flying for the first time on 23 January 1934 in the hands of Mutt Summers.

Operational history
Vickers had hoped to sell the Vellox as a ten-passenger airliner and the new fuselage had five windows per side in front of large starboard side freight doors at the wing trailing edge, but the sole example was used by Imperial Airways as a freighter, mailplane, and for testing Lorenz beam. The Vellox crashed shortly after takeoff from Croydon Airport in August 1936 due to a loss of power possibly as a result of a fuel problem. The crew of two pilots and two wireless operators was killed.

Variants
Vellore I (Type 134)
Jupiter-powered single-engine freighter, one built.
Vellore II/Jaguar-Vellore (Type 166)
Jaguar IV-powered single-engine freighter for Australia flight, one built.
Vellore III (Type 172)
Jupiter XIF-powered twin-engine freighter, one built.
Vellore IV (Type 173)
Jupiter XIF-powered twin-engine mailplane, one built.
Vellox (Type 212)
Pegasus-powered twin-engined airliner, one built.

Specifications (Vellore III)

References

Citations

Bibliography
 
 
 To Australia in a fortnight

1920s British civil aircraft
Vellore
Biplanes
Aircraft first flown in 1928
Single-engined tractor aircraft
Aircraft with fixed conventional landing gear