Gazelle
Napier Gazelle at the Royal Air Force Museum London
Type	Turboshaft aero engine
Manufacturer	D. Napier & Son
First run	December 1955
Major applications	Westland Wessex Bristol/Westland Belvedere

The Napier Gazelle is a turboshaft helicopter engine that was manufactured by D. Napier & Son in the mid-1950s. In 1961 production was nominally transferred to a joint venture with Rolls-Royce called Napier Aero Engines Limited.^[1] But the venture closed two years later.^[2]

Variants

NGa.1

Emergency rating 1,260 shp (940 kW) at 20,400 rpm, 1 hour rating 1,100 shp (820 kW) at 19,800 rpm, Max continuous rating 920 shp (690 kW) at 19,000 rpm^[3]

NGa.2

Emergency rating 1,650 shp (1,230 kW) at 20,400 rpm^[3]

NGa.2(R)

^[4]

NGa.2 series 2

NGa.3

Emergency rating 1,800 shp (1,300 kW) at 20,400 rpm^[3]

NGa.4

Emergency rating 2,000 shp (1,500 kW) at 20,400 rpm^[3]

NGa.13(R)

^[4]

NGa.13 series 2

NGa.18

NGa.22

Mk.101

^[4]

Mk.161

^[4]

Mk.162

(NGa.13 series 2)^[4]

Mk.165

^[4]

Gazelle 501

^[4]

Gazelle 503

^[4]

Gazelle 512

^[4]

Gazelle 514

^[4]

Gazelle E.219

^[4]

Applications

These helicopter engines were used on the Westland Wessex HAS 1 and HAS 3 (other versions of the Wessex had two Rolls-Royce Gnome engines) and the Bristol Belvedere (later Westland Belvedere) transport helicopter.

Engines on display

A preserved Napier Gazelle is on display at the Royal Air Force Museum London. A preserved Napier Gazelle from a Westland Wessex helicopter is on display at the Queensland Air Museum, Caloundra, Australia. A Napier Gazelle is on display at the South Yorkshire Aircraft Museum, Doncaster A further Napier Gazelle is displayed at the Solent Sky Museum, Southampton

Specifications (Gazelle 501 / Mk.101 / NGa.2(R))

Data from Jane's All the World's Aircraft 1962-63 and Flightglobal archive.^[4][5]

General characteristics

• Type: Turboshaft
• Length: 70 in (1,778 mm)
• Diameter: 33.5 in (851 mm)
• Dry weight: 830 lb (376.5 kg)

Components

• Compressor: 11-stage axial flow
• Combustors: 6 flame tubes
• Turbine: 2-stage gas generator power turbine + 1-stage free power turbine
• Fuel type: Aviation kerosene
• Oil system: Pressure spray / splash with gear pump and dry sump

Performance

• Maximum power output: 1,650 hp (1,230 kW) + 260 lbf (1.2 kN) thrust at 3,000 output shaft rpm, maximum rating for 2.5 minutes
• Overall pressure ratio: 6.25:1
• Air mass flow: 16.8 lb/s (7.6 kg/s)
• Specific fuel consumption: 0.688 lb/(hp h) (0.4185 kg/(kW h))
• Power-to-weight ratio: 1.458 hp/lb (2.397 kW/kg)