Wind in the wires

I had the good fortune to go to the RAAF Museum Air Pageant at Point Cook in February. There, standing in a hangar, was the recently completed replica of a Bristol Boxkite the Central Flying School flew at Point Cook in 1914. The replica was built to commemorate 100 years of continuous military flying in Australia on March 1, 2014 – one for the calendar.

What a huge, fabulous machine. It has a wingspan of 14. 17m, is 11. 73m long and 3. 61m tall and also has the extended upper wingspan.

Built as a two-seat trainer by the Bristol and Colonial Aeroplane Company at Filton, Bristol in England, 76 Boxkites were built between 1910 and 1914.

Sixty were of the military version with the extended upper wings and a 50hp (37kW) Gnôme rotary engine. The replica is powered by a 110hp (82kW) Rotec R2800 radial engine.

Construction was all wood with fabric surfaces and a mass of struts, booms and bracing wire. The gross weight of the Boxkite is 522kg and it had a maximum speed of 40mph (35kt). Little wonder that flight training was done when the wind speed was low or nil, typically at dawn or dusk.

The Boxkite was truly a calm weather aeroplane.

From a flying training point of view, as seen by this 2012 flight instructor, the instructors and trainees who flew these machines in 1914 have my full admiration. There was no floor or cockpit to give the feeling of security as in a modern aircraft.

The two seats were in tandem and truly out in the slipstream.

Seat belts you ask? Doubtful.

Communication was by shouting and hand signals. It was not until 1917 that Major Robert Smith-Barry introduced the Gosport system of speaking tubes at the RFC School of Special Flying at Gosport, Hampshire where a formal method of flying training was developed.

There was one tall control column in front of the forward pilot. For a flight trainee getting into this machine must have been a daunting sensation for a person used to a horse and cart. Nevertheless, the CFS did produce graduates using the Boxkite.

There was only one instrument in the original Boxkite, a barometer. The replica is decked out with more instruments than a Cessna 150. One thing that the Cessna 150 did not have is the long strand of wool taped to the trailing edge of the forward mounted elevator.

In modern terminology that is the balance ball.

There are ailerons on all four wings but they differ from modern aircraft in that there is no return control cable. The ailerons simply droop until there is sufficient air speed to bring them up to the same angle of attack as the wing they are mounted on.

To make a turn the pilot had to move the control column to pull the ailerons down on the outside wings of the turn. No differential aileron here. Given the speed of the machine this caused adverse yaw with drag wanting to pull that wing back.

To counter this the pilot had to lead with a good measure of rudder – and there are three rudders on the replica with no fixed vertical surface. The wool strand mounted in front of the pilot would have been his method of making a balanced turn. Now you know where the expression ‘stick and rudder’ came from. In a glass aircraft of today, the skid bar on the AH barely moves, even if your feet are on the floor in a turn.

Film clips of the Shuttleworth Collection Bristol Boxkite replica in flight show it to have a tendency to Dutch roll when the pilot applies aileron control, no doubt caused by the aileron drag and rudder application.

In military service the Boxkite proved cumbersome to fly and by 1915 the majority had ceased to operate. Of the two CFS machines CFS 3 soldiered on until 1917 when it was disposed of due to wear and tear.

Today, we look at flying training from a different perspective.

We have aircraft that have reliable engines, communication and navigation systems and cockpits that are user friendly and comfortable. We also have proven techniques for safe flight training. All a far cry from those pioneering wind-inthe- wires days.

Given the changes to aircraft and flight training over the past 100 years, one can only speculate what the next 100 years will bring.

Contact Dave by email at flyer02@optusnet. com. au