Plessey Dynamics Solent Gas Turbine MK101 Austin 250 Gas Turbine Perkins Mars Gas Turbine

British Gas Turbines

Plessey Dynamics Solent Gas Turbine Starter MK101-

Plessey Solent Solent Specification
Power Output....................................….…………..........70 Bhp (1 minute duration)
Rpm................................….………..............…..…….................Centrifugal Impeller
Combustion Chamber..........….……......Reverse flow Annular with 8 Simplex Burners
Gas Generator Turbine...........….….....….……………………..………….................Axial Flow
Power Output Turbine..................Axial Flow with 11:1 epicyclic reduction gearbox

Layout............................Twin shaft, spring-loaded angular contact main bearings
Starting.......................................................….…………............DC Starter Motor
Ignition.........................................................................Two HT Igniter Plugs
Fuel System................Gear Pump with Centrifugal Governor, Acceleration Control
Lubrication...............................One-Shot pump powered by compressor bleed air
Application..........................MD Phantom F4 GTS, Experimental Ground Power unit


Austin 250 Industrial Stationary Gas Turbine Engine-

Austin 250 Gas Turbine Specification
Power output..............................................….………………………………….....250 Bhp
RPM...................................................….……………………………………............29,200
Compressor...........................................….……………….........Centrifugal Impeller
Combustion Chamber...............................….…………….......Side Entry, Single Can
Turbine...................................................….………………………….......2 Stage Axial
Layout.................................................................Single Spool with reduction gearbox, non axi-symmetrical
Starting...................................................….……………….......Lucas Starter Motor
Ignition....................................................….……………........High Energy Igniter
Fuel System.........................................................Gear Pump with Centrifugal Governor or Natural Gas System
Lubrication...........................................….………..........Dry Sump with oil cooler
Applications...........................................….…….........Stationary Engine, Water Pump or Generator


Perkins Mars Stationary Gas Turbine-

T41/Mars Specification

Power Output....................….……………….…….………………………..........50 hp
Rpm.....................….…………………………….…...……........................40,000
Compressor..........….…………….………………................Centrifugal Impeller
Combustion Chamber..….………….……….................Single Can Combustor
Turbine.....................….………………………................Single Radial Inflow
Layout...........................Overhung, Single Spool, non axi-symmetrical
Starting......................….………...........Hand Crank or Starter Generator
Ignition..............................….……………..........High energy or Magneto
Fuel System..............................Gear Pump with Centrifugal Governor
Applications.................Water Pump, Ground Power Unit, Airborne APU
instructional engine


Perkins Gas Turbines Advert Continueous-run Solent Gas Turbine Perkins Gas Turbines LTD Peterborogh Mars Gas Turbine Engine

The Plessey Dynamics Solent Mk101 gas turbine starter(GTS). A small turbo-shaft gas turbine engine (microturbine) developed as the “starter motor” for the McDonnell Douglas Phantom jet fighter aircraft and is rated at some 70HP. This twin shaft unit is mounted on the accessory gearbox of the Rolls Royce Spey 200 series low bypass turbofan engine. A clever design keeps the Solent compact and simple. It is believed the Solent gas-generator section is descended from the Microturbo Saphir series of engines. Examining both engines, a number of similarities are apparent.

The Solent engine comprises of a centrifugal compressor feeding a classic wrap around reverse-flow combustor fitted with eight burners. A single axial flow turbine wheel drives the compressor and it is mounted on a shaft supported by spring loaded angular contact ball races. Hot gases from the gas-generator section are exhausted on to a second axial flow turbine wheel. The turbine wheel drives in to a two stage epicyclic gearbox with a ratio of some 11:1. An output shaft speed of up to 5000 rpm provides the driving force to start the aircraft engine. The exhaust gases are directed around the gearbox housing and discharged downwards via a vaned duct.

The Solent features spill type simplex atomising burners that are fed from a gear type fuel pump. The pump delivers a fuel flow in excess of the engine requirements and control of fuel metering is effected by an acceleration control valve. The acceleration control valve is activated by compressor delivery pressure, as the Solent is started, lights and accelerates, building air pressure opens the valve and greater fuel flow results. The Solent is governed by a simple fly-weight centrifugal governor mounted on top of the fuel pump shaft. When the gas generator reaches 60,000 rpm the governor spill valve opens under the action of centrifugal force and the speed is held constant at 60,000 rpm. The burners are also calibrated to open in pairs at increasing fuel pressure so as the engine accelerates good atomisation and combustion is maintained across the fuel flow range.

The Solent accessories consist of the simple gear fuel pump and a starter motor driven from the compressor shaft. The starter motor and fuel pump are mounted at the front of the engine (Compressor air-intake end) together with a bevel gearbox containing the necessary reduction gears. The engine is only rated for operation for one minute (the time it is expected to start the main aircraft engine) and so the starter motor is driven continuously from the compressor shaft after the Solent start cycle is complete.

A clever feature of the Solent gas turbine is the oil system. The engine uses a simple one-shot for lubrication of the bearings. When the engine is stationary a small chamber fills with oil from a reservoir and becomes pressurised with compressor air when the engine runs, a moving ball meters a quantity of oil on to the bearings. After one minute the Solent is shut down and the cycle resets itself. The accessory gearbox and output reduction gearbox are splash lubricated.

The engine is fitted with two high-tension igniter plugs to ensure a rapid light-up during starting. The plugs are mounted adjacent to the two burners set to open at minimum fuel pressure i.e. they open first.

The output reduction gearbox is fitted with a special cutout mechanism. A second flyweight governor opens a set of electrical contacts to signal to the aircraft starting system that the Spey engine has successfully started reached self sustaining speed and so the starter may be shut down. If the Spey engine fails to start, it will not reach self-sustaining speed, the starter shaft will not exceed 5000 rpm and so the Solent is shut down by an automatic timer circuit.

The Phantom aircraft are retired now, it must have been quite a spectacle to watch and hear a Solent in action! This small engine will spin up very quickly and howl away as the big Spey engine catches up. I understand the Solents were prone to various failures, malfunction of the electrical control circuits or the cut out switch could result in the power turbine over-speeding and bursting with catastrophic results! Repeated start attempts could overheat the Solent causing lubricating oil fires.

For hobby and experimental use the Solent can be fun but a challenge to accomplish useful tasks. They have been fitted to go-karts and used as small turbo-prop engines for micro-lights. The Solent may also be made in to a turbo-jet engine but weight and bulk are against it!  The intermittent rated nature of the Solent may be an obstacle to successful deployment in vehicles, aircraft etc. The oil system, starting, fuel system and burners may all require modification.

Having built the intermittently rated Solent, Plessey did investigate modifying it (with the addition of various oil pumps) for use as an APU generator. A white paper was written that describes how it was done. I understand only one prototype (pictured above) was ever built.



Thanks to www.aviationancestry.co.uk for the Solent Advert

The Perkins Mars gas turbine is a British licence built version of the American Solar T41. A very simple stationary unit featuring a centrifugal compressor, radial inflow turbine and can type combustor. A rival to the Rover 1S60 producing 50HP. These engine could be found in use driving water pumps, electrical generators and also as instructional sets for colleges and universities. This type of engine was built long before the smaller rc-model type turbojets that may be adapted for laboratory use today.

A hand crank unit requiring some considerable effort to achieve self-sustaining speed. A simple magneto created sparks to light the engine as the crank handle was turned.

LINK to Perkins History Site

From the 1980s white paper engine illustration

In use in 2016 the surviving gas turbine design

Unusual small Microturbine by R H Philips and Son/Normalair Garrett/Holset

Normaliar Garrett Prototype Turbojet Engine

In the 1980s Belfast Queens University embarked on a research project to develop a low cost disposable turbo-jet engine in partnership with Normalair Garrett, although Holset may also have made a contribution. A simple unit derived from a turbo-charger rotating core with re-worked vanned diffuser and a vanned turbine nozzle. A pioneering idea at the time as it was unlikely much work like this had been done before. Now helped by the Internet enthusiasts all around the World have built many demonstration engines and have even powered go-kart like vehicles to amazingly high speeds with turbochargers.

The engine has been developed in to a stationary unit for use as a smoke generator and air compressor. The use of a turbo-charger core keeps costs down and ensures a tough and robust unit for military use.

Engine sets were built up in enclosures by R H Philips and son of Sussex.


Normalair Garrett Microturbine Microturbine test bench run Plessey Solent Mk101 Microturbine Schematic

LINK: University white paper “The development of an expendable gas turbine engine” Dr D W ARTT and Dr N F ADAMS   (pdf)

Around 1950 the Austin car company experimented with gas turbines and initially developed a unit for fitment to a car. This wasn’t really successful so they turned to the development of a stationary engine and the “Austin 250” model was produced. The simple engine consisted of a single stage centrifugal compressor driven by a two-stage turbine. The layout and components seem to resemble some industrial turbo-charger components.  An external single can combustor was fired with either liquid fuel or natural gas. An unusual feature of the burner system was the igniter plug was built in to the burner head. The engine featured a heavy duty helical cut gearbox with accessories mounted on it. The engine used a large diesel type starter motor and the whole engine assembly sat on a large flat oil-tank. Kerosene burning engines were fitted with a simple gear pump and governor arrangement, gas burning engines would have a governor valve and an external gas compressor.


Engines were mostly used for power generation and were fitted to a 200KVa alternator, a few were also tried as fire-fighting pumps.


A gas fired unit was found a few years ago that had been decommissioned from a power station. No liquid fired unit in working order has been seen to date.


Link to Austin Memories Site


A natural gas fired auxiliary unit salvaged from a power station. It is possible to test run the engine using a supply of propane gas without the use of an external gas compressor.

Back To HOME page

R H Philips Gas Turbine Microturbine engine

Turbo-charger based gas turbine started with a simple bendix type engagement