Rolls-Royce Vulture

Rolls-Royce Vulture. The Vulture was a British 24-cylinder X-24 configuration piston engine developed during the late 1930s. Intended to power a new generation of heavy bombers, it suffered from persistent reliability problems that severely hampered its operational service. Its failure led directly to the development of the highly successful Avro Lancaster and the abandonment of the X-24 engine concept by Rolls-Royce Limited.

Development and design

The engine was conceived in 1935 to meet Air Ministry Specification P.13/36, which demanded a high-power engine for twin-engine bombers. The design team, led by Ernest Hives, adopted an unconventional X-24 engine layout, essentially coupling two Rolls-Royce Peregrine V12 engines onto a common crankshaft. This complex arrangement promised the power of a larger engine in a compact format, aiming to produce around 1,750 horsepower. The project was pursued aggressively by Rolls-Royce Limited amidst intense competition from rivals like Bristol Aeroplane Company and their Bristol Hercules radial engine. However, the intricate gearing and shared crankshaft created fundamental mechanical weaknesses. Critical issues emerged with the big-end bearings, which failed under high loads, and inadequate lubrication to the lower cylinder banks. Despite efforts by engineers at the Derby and Crewe factories, these design flaws proved insurmountable within the wartime timescale.

Operational history

The engine entered service exclusively with the Avro Manchester, the Royal Air Force's first heavy bomber designed to the P.13/36 requirement. Operational history with No. 207 Squadron RAF and other units was disastrous. The engines were chronically unreliable, suffering frequent in-flight failures that led to numerous aborted missions and crashes. The poor serviceability crippled the Avro Manchester's effectiveness during raids over targets like Bremen and the Battle of the Ruhr. The crisis prompted a major investigation by the Ministry of Aircraft Production and forced a fundamental redesign of the airframe. The replacement of two troublesome engines with four reliable Rolls-Royce Merlin units transformed the failed Avro Manchester into the legendary Avro Lancaster. This switch, orchestrated by figures like Roy Chadwick and Ernest Hives, ended any further operational use of the engine and cemented its reputation as a notable failure.

Variants

Few distinct variants were developed due to the engine's short service life. The primary production model was the Vulture I, which powered early production Avro Manchester Mk.I aircraft. The marginally improved Vulture II incorporated design changes in an attempt to address the bearing failures, but it offered no significant increase in reliability. A proposed Vulture III with a two-stage supercharger was tested but never entered production. Another experimental project, the Vulture IV, was intended for the Hawker Tornado fighter, but the program was cancelled in favor of the Hawker Typhoon with the Napier Sabre engine. The lack of successful variants underscored the fundamental unsoundness of the core design.

Applications

The only aircraft to use the engine in operational service was the Avro Manchester. Its installation was also planned for several other ambitious designs that were either cancelled or modified. The Hawker Tornado, a contender for Fighter Command, was designed around it but never entered production. The Vickers Warwick prototype initially flew with the engines before being re-engined with Bristol Centaurus engines. A proposed naval fighter by Blackburn Aircraft, and early concepts for what would become the Avro Lincoln bomber, also considered the powerplant before the focus shifted entirely to the Avro Lancaster and its Rolls-Royce Merlin and later Rolls-Royce Griffon engines.

Specifications (Vulture II)

* Type: 24-cylinder X-24 engine liquid-cooled piston engine * Bore: 5.0 in (127 mm) * Stroke: 5.5 in (140 mm) * Displacement: 2,590 in³ (42.5 L) * Length: 108.5 in (2.76 m) * Diameter: 46.5 in (1.18 m) * Dry weight: 2,450 lb (1,111 kg) * Valvetrain: Overhead camshaft * Supercharger: Single-stage centrifugal supercharger * Fuel system: Float carburetor * Cooling system: Liquid-cooled, ethylene glycol * Power output: 1,750 to 1,980 horsepower at 3,000 rpm at 11,000 ft * Specific power: 0.76 hp/in³ * Compression ratio: 6.0:1 * Power-to-weight ratio: 0.8 hp/lb

Category:Aircraft piston engines Category:Rolls-Royce aircraft engines