The majority of gyroscopic instruments in today's modern aircraft, particularly military and larger commercial aircraft such as the Turn/Bank, Directional Gyro and Artificial Horizon indicators rely on a vacuum generated by an independent electrical pump or vacuum pump driven by the aircraft’s main engines, but this wasn't always the case.
Early vintage aircraft instrumentation achieved their vacuum power source through the use of a simple Venturi Tube mounted on the fuselage or wind strut parallel with the longitudinal axis of the aircraft.
The Venturi tube works on the same scientific law known as the Bernoulli Effect as an airfoil.
The pressure in a stream of fluid is reduced as the speed of the flow is increased. When that fluid is air passing over the cambered upper surface of an airfoil, the result is lift. When it flows through a Venturi tube, the result is suction.
As air passes through the narrow throat of the tube, its speed increases and its pressure drops. A small port inside the constricted area taps this pressure to create suction in a line connected to the port. The line is plumbed back to the gyroscopic instruments.
With no moving parts and no power-source other than a slipstream it is still used today, as relatively inexpensive way of producing the vacuum needed to suck air into the instruments’ inlet port to spin the gyro rotor activating the instrument for smaller recreational and vintage aircraft.
It’s only downside is that it requires a slipstream to operate and is ineffective until the aircraft gains enough speed to create a flow through the tube.
Venturi tubes can be seen in some of the most recognised and popular biplane and monoplane aircraft such as - the De Havilland Tiger Moth, Ryan ST Sports, Boeing Stearman and Avro Anson, although both the Tiger Moth and ST Ryan were tradionally fitted with the smaller 2" Venturi.
As a participant in the Empire Air Training Scheme (EATS), Australia had committed to supplying 11,000 aircrew each year for the RAF, Fleet Air Arm and the RAAF and by June 1944 had trained over 37,800 personnel with 27,899 graduating as aircrew.
Many of these trainee pilots would have commenced their initial flight orientation in the single engine De Havilland Tiger Moth before graduating to smaller twin-engine trainers like the Avro Anson.
First introduced into the RAF in 1936 as a light bomber and maritime reconnaissance aircraft, the Avro Anson was the first monoplane to attain squadron status with the RAF and the first aircraft with a retractable undercarriage but whilst it soon became apparent that it was no match for the enemy's more advanced fighters like the Messerschmitt Bf 109 and 110, it was however, ideally suited as a twin engined trainer.
Between 1936 - 1944 some 1028 Ansons were shipped to Australia for use by the RAAF as coastal patrol aircraft and flight crew trainers. Many others were also sent to Canada, South Africa and New Zealand - all participants in the collaborative EATS program.
By 1938, Australia’s home grown Commonwealth Aircraft Corporation (CAC) had already commenced manufacture of the Australian designed single-engined fighter, the CAC Boomerang and the light CAC bomber, the Wirraway.
The Australian government's move to established the CAC was also successful in galvanised the nation's electronic, automotive and communications industry to create and supply key aviation components such as flight instruments, radio communications equipment and flight control components.
Many of these were built under licence from British and US manufacturers, with the traditional British AM & Crown markings replaced with the RAAF & Crown or an additional RAAF & Crown data plate being attached to the original.
By the time the CAC were building their own Bristol Beauforts, Bristol Beaufighters and even P-51 Mustangs toward the end of the war, the RAAF & Crown logo had replaced the Air Ministry 'AM & Crown' with wartime repairs to existing equipment also displaying the Australian data plate.
One such component supplier to the CAC was Australia’s Amalgamated Wireless Asia (AWA) who produced a wide range of radio and aircraft componentry for the war effort.
One of these was the 4” Brass Venturi Tube built under licence to Sperry and fitted to the British Avro Anson shown here.
Complete with its original RAAF & Crown data plate on one side of its mounting base and the AWA Data plate on the other,
This beautiful brass Venturi Tube, mounted on its 100yr old Mango Wood stand with a highly detailed, hand built scale model of this iconic wartime, twin-engine trainer would be the perfect gift for any aviation enthusiast.
Here is an amazing opportunity to secure a rare piece of early RAF WWII aviation history with an original Avro Anson 4" Brass Venturi Tube mounted in a stylish 100yr old Mango Wood Display Stand with engraved plaque and a highly-detailed 1/72 or 1/48 scale model of this classic early RAF coastal patrol/trainer perched above, on its magnetic display arm.
Your Recovery Curios, Original Vintage Aircraft Instrument Collectable also comes with a detailed, printed and laminated Instrument Fact Sheet with a history of the aircraft and photograph of the instrument in the aircraft cockpit. What a fantastic gift for the aviation enthusiast in your life!
This Avro Anson Instrument comes complete with detailed Scale Model, Mango Wood Stand & Plaque plus Printed Fact Sheet featuring photo of the instrument in the aircraft cockpit.
Your Avro Anson, RAAF 4" Brass Venturi Tube, Original Recovery Curios Warbird Collectable includes:
*An upgrade to the larger and more detailed 1/48 scale model is also available in the hand-built and airbrushed plastic version for an additional $45 (Click on the 1/48 scale option)
Both the 1/72 & 1/48 scale hand-built and airbrushed plastic models are available with 'wheels & flaps up or down' and 'canopy open or closed' options with a choice of two Squadron markings and camouflage.
Upon order placement you will receive an email asking for your preferred configuration.
Your complete Recovery Curios Original Instrument Collectable is securely packed and delivery normally takes between 6 - 8 weeks approx.
Did you fly, crew or maintain an Avro Anson or have a friend, colleague or family member who did? Check out our PERSONALISED ORIGINAL INSTRUMENT COLLECTABLE OPTION here.