AVRO VULCAN, SMITHS KAE 0701W ACCELEROMETER

Each of the Avro Vulcan’s four 4 × Bristol Olympus Mk.101 / Mk.102 / Mk.104 twin-spool turbojet engines could deliver over 17,000 lb of thrust giving it a climb rate of 6000 ft/min to a service ceiling of over 55,000 ft with a maximum speed in excess of 646 mph or Mach 0.96. In a dive, this would be far greater.

The G forces exerted by such rapid acceleration on both crew and aircraft can be enormous and need to be constantly monitored to keep within the limitations of the human body’s tolerance and that of the jet's airframe.

Military pilots have long worn pressurised G suits which work to counteract the acceleration forces on their bodies but an aircraft’s components and airframe has no such protection and are rated for operation within defined parameters.

Too high a G force can cause a pilot to loose consciousness whilst continual and constant G forces on an airframe will rapidly deteriorate its service life and at worse, cause a catastrophic break up of the aircraft in midair.

To monitor the stresses imposed on both pilot and airframe, an Accelerometer is mounted at the pilot’s eye level on the main flying panel  

Whilst primarily used to monitor the forces acting on the airframe, accelerometers are also used as part of the aircraft’s inertial reference navigation system.

Most accelerometers are mechanical with direct-reading instruments calibrated to indicate force in Gs. One G being equal to one times the force of gravity and the dial face of an accelerometer is scaled to show both positive and negative forces on the aircraft.

When an aircraft is put in a rapid climb, a positive G force pushes the pilot back into their seat. The faster the climb the greater the G forces exerted. A rapid descent will apply force in the opposite direction resulting in a negative G force.

The accelerometer operates on the principle of inertia. A mass, or weight, inside slides freely along a shaft in response to the slightest acceleration force in either direction. When a manoeuvre creates an accelerating force, the aircraft and instrument move, but inertia causes the weight to stay at rest in space. As the shaft slides through the weight, the relative position of the weight on the shaft changes. This position corresponds to the G force experienced. 

Through a series of pulleys, springs, and shafts, the instrument’s pointers are moved around the dial to indicate the relative strength of the acceleration force. Although most cockpit gauges are of the single-axis type. Inertial reference navigation systems make use of multi-axis accelerometers to continuously, mathematically calculate the location of the aircraft in a three dimensional plane

Most accelerometers like this Smiths KAE 0701W, have three pointers. One is continuously indicating the acceleration force experienced. The other two contain ratcheting devices. The positive G pointer follows the continuous pointer and stays at the location on the dial where the maximum positive force was experienced. The negative G pointer does the same for negative forces experienced. Both max force pointers can be reset with a knob on the instrument face.

The instrument’s ability to capture the highest and lowest G load during the Avro Vulcan’s long missions, was critical to monitoring the stresses on the aircraft, never more so than when carrying a full load of nuclear armaments and fuel. 

This Smiths KAE 0701W Accelerometer has a rating between 5 and minus 2 G and was installed at the bottom left of the pilot’s main flying panel just above the aircraft's Rate of Climb Indicator. Service markings on its rear casing indicate it had an operational life of approx. 6 years, being serviced annually. 

With a clear glass face and relatively unmarked casing, this Smiths KAE 0701W Accelerometer appears to be in full working order after we mounted it on the dash of our trusty Nissan X Trail and floored the pedal before then stomping on the brakes. No chance of loosing consciousness from an over abundance of G forces but all the needles moved in the right directions and pressing the reset button took them back to zero again.

If anyone would like to loan me their Maserati Levante sports car, I’d be quite happy to take it for a spin and tell you it’s G force readings!

With a highly detailed 1/72 scale model of the Avro Vulcan perched atop its hand crafted mango wood stand, this would make a fantastic gift for any aviation enthusiast.

This Avro Vulcan Instrument comes complete with detailed Scale Model, Mango Wood Stand & Plaque plus Printed Fact Sheet featuring photo of instrument in aircraft cockpit. 

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