The Bristol Beaufighter G6A/350254 Turn & Slip Indicator is probably one of the rarest and earliest WWII aircraft instruments you'll find on the Recovery Curios website.
Built in Australia under licence from the British Air Ministry at the Commonwealth Aircraft Corporation (CAC) in Victoria, it features the RAAF stamp and G6A/350254 serial number just below the British Crown and was initially only installed in Australian designed and built WWII aircraft such as the CAC Boomerang single-engine fighter and the rugged two seater trainer/fighter/bomber, the CAC Wirraway.
Later it was also installed in Australian built versions of the Bristol Beaufighter and Bristol Beaufort - all built by the CAC under licence.
A home grown solution...
The creation of the CAC is arguably one of the most critical and strategic moves made by the Australian Government leading up to WWII, when it was feared that with the onset of a global conflict, supplies of both aircraft and parts to Australia could well be delayed or prevented altogether.
It was to prove an inspired decision, as events turned out to be exactly as feared with the supply of both British and US aircraft being directed to RAF units in Europe and the Middle East and US naval forces in the Pacific region.
This left Australia particularly vulnerable as the RAAF scrambled to secure what spare aircraft they could from the British and US which consisted mostly of P-39 Airacobras, P-40 Warhawks along with a small number of early Spitfires.
Later as the war in Europe and the Pacific began to slowly turn in the Allies favour, Australia began to receive more British and US built aircraft as the focus moved toward defeating the Japanese in the South Pacific and Australia found itself hosting a number of forward US airbases across its northern regions.
Interestingly enough, with original instrumentation in short supply, a number of damaged British and US designed aircraft such as the Spitfires and P-40 Warhawks based in Australia’s Northern Territory and Papua New Guinea would often be serviced with Australian produced spares so it was not uncommon to find an eclectic mix of instrumentation in the cockpits of aircraft that managed to survive the war in these regions.
One of the most important of these cockpit instruments was the Turn & Slip Indicator.
Sometimes called the Turn & Bank Indicator, the unit was effectively two flight instruments in one and usually mounted near the centre of the pilot’s main flying panel.
One component indicated the Rate of Turn or the ‘rate of change' in the aircraft’s heading and is based around a small gyro built on a gimbal. As the aircraft yaws or swivels on its central axis, the gimbal and gyro rotate against a calibrated spring. Usually measured in degrees per second or minutes per turn, the unit alerts the pilot to the speed of his turn.
Into the turn...
In later units and predominantly USAAF instrumentation, the Rate of Turn featured ‘Hash' marks spaced on either side of a central mark. Known as ‘Dog Houses’ for their shape, when the needle was aligned with the central mark, the aircraft was said to be performing a ‘Standard Rate Turn’ which is roughly equivalent to three degrees per second or equivalent to two minutes for the completion of a 360 degree turn or full circle.
Being a much earlier model, the RAAF unit featured here does not have the ‘Dog House’ Hash marks of later units and instead the ‘Rate of Turn’ is simply measured in minutes of turn from 1 to 4 minutes across the bottom of the face.
A 4 minute turn would have a relatively slow and wide turning circle where as a 1 minute turn, would indicate a fast and tight turn.
For modern civil aviation aircraft beginning their runway approach, their pilots would be implementing a slow and comfortable turn to ensure passenger comfort and safety rather than risk plastering passengers up against the cabin walls.
The other component is the Inclinometer located at the top of the instrument face.
Again, in later and predominantly USAAF instrumentation this usually consists of a small ball inside a sealed curved glass tube, filled with liquid for damping but in this early RAAF unit, the instrument uses a simple pendulum needle and spring dampener rather than the later ‘ball in a glass’
Operating much the same as a spirit level, the ‘ball’ or in this case, the ‘pendulum needle’ gives an indication of whether the aircraft is slipping, skidding or in coordinated flight.
The ball or needle’s movement is caused by the force of gravity and the aircraft's acceleration around its central axis.
When they are centred in the middle of the dial, the aircraft is said to be in coordinated flight. If they are on the inside (wing side down) of a turn, the aircraft is said to be ‘slipping’. If on the outside (wing side up) of the turn, the aircraft is ’sliding’.
When an aircraft is in a balanced turn, pilot and passengers experience a slight increase in gravity directly inline with their seat and in a well balanced turn, might not even realise the aircraft is turning unless they are looking out the window.
Slip sliding away...
Slipping or Sliding within a turn are sometimes referred to as a sloppy turn due to the apparent discomfort it can cause to the pilot and passengers but the manoeuvre does have some pratical implications.
Intentionally putting an aircraft into a forward or side slip by applying opposite inputs of the aileron and rudder controls is often used by the pilot to either, allowing the aircraft to drop altitude without gaining unnecessary speed (a forward slip) or utilising the aircraft’s sideslip to counteract a crosswind landing.
What a unique and unforgetable gift for the aviation enthusiast in your life! - An original, WWII Bristol Beaufighter G6A/350254 Turn & Slip Indicator mounted in its 100yr old Mango Wood Display Stand with engraved plaque, printed and laminated Fact Sheet plus a highly detailed, custom built Scale Model of this iconic Australian built fighter/bomber, perched atop its magnetic display arm.
This Bristol Beaufighter Instrument comes complete with detailed Scale Model, Mango Wood Stand & Plaque plus Printed Fact Sheet featuring photo of instrument in aircraft cockpit.
Return to Bristol Beaufighter MAIN PAGE