ABOUT

Aircraft have been exhibited in the Science Museum since the earliest days of powered flight, initially as a special exhibition in 1912. The permanent collection has occupied various locations before finding its current home on the third floor of the museum’s Centre Block in 1963.

The Flight gallery contains 21 full-sized aircraft, most of which are suspended from the ceiling. Visitors have found it challenging to identify the aircraft high above their heads so I was tasked to produce accurate and detailed illustrations of each aircraft which are prominently displayed on new signage throughout the gallery.


Thanks to Hetty Tapper, Becky Jarvis-Stiggants, Emma Ellis and Catherine Cooper at the Science Museum and to Mash Chudasama of Mash Design for his layout and design skills. I should also like to acknowledge Benjamin M. Regel of Imperial College London for his PhD thesis “The Conservation of Doped-Fabric Aircraft at the Science Museum, London” (2019) for some of the technical details noted here.

The comments and opinions stated here are entirely my own, as are any errors.

The exhibits include:

1783 Montgolfier Balloon

1842 Aerial Steam Carriage

1891 Lilienthal Glider

1903 Wright Flyer-two versions

1909 Roe I Triplane

1909 Antoinette VII

1910 JAP-Harding Monoplane

1910 Beta II Airship Car

1912 Cody V

1915 Fokker E.III

1916 SE5a-two versions

1917 Vickers Vimy-two versions

1925 De Havilland DH.60G Gypsy Moth

1926 Westland-Hill Pterodactyl 1A

1931 Supermarine S.6B

1934 Cierva C.30

1935 Douglas DC-3

1935 Hawker Hurricane Mk Ia

1936 Supermarine Spitfire Mk Ia-two versions

1941 Gloster E.28/39

1944 V-1 Flying Bomb

1944 Pitts Special S-1S

1948 Saunders-Roe Skeeter AOP.12

1949 de Havilland Comet-The size of the Comet rules out one being on display in the gallery, but as the first jet-engined airliner, deserved to be included in the timeline display.

1960 Hawker Siddeley P.1127

1962 Hawker Siddeley 125

1969 Schempp-Hirth Standard Cirrus
1969 Boeing 747

1984 Meggitt Banshee 300

It was also thought desirable to improve the STEM educational aspect of the signage and I produced a number of illustrations to explain various aspects of aeronautics, including flight control surfaces and engine types.
Lighter-than-air
A lifting gas is one that has a density lower than normal atmospheric gases and rises above them, enabling them to lift lighter-than-air aircraft. Dry air has a density of about 1.29 grammes per litre and so lifting gases must have a density lower than this.
A quantity of air expands as it is heated, so it’s density decreases as the temperature rises, the typical operating temperature for a hot-air balloon is 121ºC.
Hydrogen, being only 7% the density of air, was widely used for lighter-than-air craft, but is extremely flammable. Disasters such as the loss of the Hindenburg demonstrated the safety risks associated with this gas.
Helium is the second lightest gas and, being non-combustible, is an attractive lifting gas. However, it is expensive to produce with only a handful of reserves trapped in natural gas wells. When released into the atmosphere, helium eventually escapes into space and is lost.
Aerofoil

An aerofoil is a streamlined shape that is capable of generating significantly more lift than drag using Bernoulli’s principle.

The airflow over the wing increases its speed, reducing its pressure, thereby generating lift which acts perpendicular to the aerofoil. The airflow under the wing moves more slowly, generating greater pressure and less lift (negative lift).

Forces of Flight

An aircraft is acted upon by four forces: lift, weight, thrust and drag.

Thrust acts in a forward direction for the purpose of overcoming drag and is generated by an engine.

Lift acts perpendicular to the velocity relative to the atmosphere.

Drag acts parallel but opposite to the velocity and resists motion through the air.

Weight acts through the aircraft’s centre of gravity towards the centre of the Earth.

Control Surfaces

Roll is controlled by moveable sections on the trailing edges of the wings called ailerons. These move in opposite directions causing differential lift on each wing and thus a rolling movement.

The three axes of rotation are pitch (movement of the nose up or down), roll (rotation around the longitudinal axis) and yaw (movement of the nose left or right around the vertical axis).

Pitch is controlled by a moveable elevator attached to the rear of the horizontal tailplane. Moving the control column backwards raises the elevator and the downward force on the horizontal tail is increased, raising the nose.

Yaw is induced by a moveable rudder–this changes the orientation and magnitude of the force produced. Because this occurs at a distance behind the aircraft’s centre of gravity, the sideways force exerts a yawing motion.

Piston Engines

Unlike automotive nomenclature, in aviation terms a linear (“inline” or “straight”) engine also includes engines that have more than one bank of cylinders and covers a variety of engine configurations, such as V-, U-, X- and H-types. The term also includes horizontally opposed (“flat” or “boxer”) types.

In a rotary engine the cylinders are arranged around the crankcase, with the propellor fixed to it. The crankshaft is fixed to the airframe, so the whole engine (and the propellor) spin. This results in a good power to weight ratio, but consumes great deal of oil and the gyroscopic effect of a large rotating mass produces handling problems in aircraft.

Radial engines also have a number of cylinders arranged around the crankcase, but in this case the crankcase and cylinders are fixed to the airframe, only the crankshaft rotates and spins the propellor which is attached to it.

Both radial and rotary engines generally have an odd number of cylinders in order to ensure smooth operation. In the five-cylinder engines shown the firing order is 1, 3, 5, 2, 4 and back to 1 – every other piston fires in turn. The one-piston gap between compression and combustion helps to compress the next cylinder to fire, making the motion more uniform.

Superchargers

In an internal combustion engine, a supercharger (“blower”) compresses the fuel/air mixture, forcing more air into the engine to produce more power. A supercharger is mechanically driven by a chain or belt from the engine’s crankshaft. A turbocharger does the same job but is powered by the kinetic energy of the exhaust gases.

The Roots-type is a positive displacement pump and delivers a fixed volume of air per revolution.

The centrifugal-type is a dynamic compressor that accelerates the air to high speed and then exchanges that velocity for pressure by diffusing or slowing it down.

The twin-screw-type has asymmetrical rotors unlike the identical rotors in a Roots blower. This enables the air to be compressed within the housing as it moves through the device.

Jet Engines

A turbojet consists of a compressor to draw air in and compress it, a combustion chamber where the fuel is added and ignited, turbines that extract power from the exhaust gases to drive the compressor, and an exhaust nozzle that accelerates the exhaust to produce thrust.
A gas turbine engine offers significant advantages of high power and low maintenance over piston engines. In applications that do not require high speeds, the gas turbine can be used to drive a conventional propellor. A turboprop features a gearbox to reduce the speed of the shaft so that the tips of the propellors do not exceed the speed of sound.
A turbofan is much the same as the turbojet, but with an enlarged fan at the front that provides thrust in much the same way as a propellor. Bypass air passes through the fan, but around the core, is not mixed with fuel and is not ignited. Air passing through the core is ignited as in the turbojet.




Photographs: © The Board of Trustees of the Science Museum under licence CC-BY-NC-SA 4.0 and © Hetty Tapper, Gallery Project Manager.