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Retro-fit Update - TOSG - Pt 1

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Guest TOSGcentral

Of late I have been deluged with enquiries regarding retrofit parts for Thrusters. This report will tell readers where we are up to and hopefully cut down a bit on my one-on-one question answering. It has to be in two parts because of available message space



OVERVIEW. A long term objective of TOSG has been to make the Thruster two seaters more practical and versatile trainers as well as more useful and satisfying sports aircraft – fitting in more with changing expectations in Recreational Aviation and meeting the challenge of a higher required skills base but doing so with a very low cost aircraft.



Progress has been somewhat pedestrian as I have been funding development personally and am quite poor. Anyway, we are getting there!



The full concept was to have a R582 engined, fully enclosed trainer capable of 70 knots cruise at around 16 ltrs per hour with flaps, aerodynamic trimmers, and the wing incidence reduced to tame some of the Thruster’s diabolical landing characteristics that make it a challenge for instructors and students alike.



In addition I wanted to lift the max. permitted MTOW to reduce strain on inspectors and owners alike but max. rough air speed of 70 knots and Vne of 80 knots would remain. This may be slow for a lot of expectations today but is hardly a 50 knot ‘putt-putt’!



A key factor is that an existing second hand Thruster can be fully renovated to as new condition for a total aircraft value of $20,000 to $25,000 as the aircraft have no fatigue lives and are really just big mecanno sets that put even extensive repairs within reach of the ‘do it at home’ owner.



The costing factors enable full ownership for a small school while containing sell out hourly rates for students – and importantly, take off a lot of insurance pressure as it is difficult to do more damage to a Thruster than the cost of an annual insurance premium (if you can get cover at all) if you fix it yourself (and most people can).



The overall scheme enables continuation of the central ethic of ‘affordable, safe, fun flying’ for the average Joe in the street!



The following is what we have been up to in order to fit those parameters together. They have greatly been enabled by the fact that Thrusters (in later years) were mainly built by sub-contractors and effectively just assembled by the Factory with minimal jigging.



FIBRE GLASS ENCLOSURES. Replacement pods have always been a hassle. The factory used at least 3 sub-contractors who had made their own moulds but I was unable to buy one of these moulds when supply dried up. I therefore took an existing production T300 pod and had a mould made from it.



However in the design I introduced a forward inspection hatch to at last get inspection/servicing access to the rudder pedal assembly and pitot head, fluted the pod for stiffening, built-in the side streamling flares (that had been add-ons) as part of the shell, discarded the factory horrible internal stiffening thing on the floor (that did little except make cleaning a ghastly task) and put in moulded GRP hoops which were considerably stronger and made cockpit cleaning much easier. All of this for a very similar weight to the originals and they will go on any Thruster two seater but still are ‘original’.



The roof and rear bulkhead panels were moulded from T500 originals just as the original sub-contractors did. These (as per the originals will only fit T300/T500 style pods – not Gemini or TSTs – both types of which are commonly retrofitted with the later pod).



The cockpit lower rear bulkhead has now been slotted so that you can get it out without dismantling the entire aircraft. This at last enables regular inspection of the critical rear bulkhead frame that carries the fuel tank, cantilevered floor tubes, rear A frame and rear wing spar connection, and gives the entire cockpit full boxed rigidity.



The factory doors were a disaster! Although only secondary structure, they were flimsy, weak, shoulder constraining and usually never sealed at all well. In addition they hit the bottom of the wing and you could never get them fully open. These were redesigned into GRP mouldings that fitted in frames and could give a total comfort and aerodynamic seal to any Thruster with a T300 model pod cockpit. The ‘bulging’ for shoulder room was controlled by internal stiffening that is also used as map pockets so you can carry maps and documents securely that you are legally required to do!



That lot gave us a stronger, more efficient, sealed cockpit with spin-off benefits of higher orders of inspection/servicing and easier to keep clean internally but with hardly any weight penalty above a standard T500 with doors.



The ‘anti-interference drag’ mouldings above the cockpit roof still have to be designed and certified as they were never produced by the Thruster factory.



I am most grateful to Wally Rudin for the initial financing of this project but all of the moulds are now owned by myself/TOSG.



NOTE. Most of the following revolves around the Bilby – an extensively modified T300 in 19 Amateur Built category – created and owned by the late Rusty Jenkins. This aircraft has been used as the TOSG flying test bed for new systems.



If the Bilby can be used for test flying of the wing incidence modification then concurrently with that we can do the test flying for the flaperon and aerodynamic trim systems at the same time. This will mean four new Engineering Orders (if my dollars can stretch that far) but will be far cheaper in the long run.



FLAPS. (More accurately – flaperons, as the Thruster has full span ailerons). There is a long history on flaperons fitted to Thrusters. Back in 1986 the Thruster factory fitted this system to a Gemini A. This was not continued with, or certified, as those early Geminis with their big barn door ailerons did not need flaps.



In New Zealand flaperons were certified and have been fitted to most NZ Thrusters for many years.



The Bilby carries a four stage flaperon system that works well, and the intention is to modify this to a production, retro fit kit 5 stage system – Neutral, take off, landing and full flap plus a one stage negative (reflex) setting for cruise. This will fill all training and private usage demands.



The modification is simple, can be applied easily by the home builder and will not be expensive.



AERODYNAMIC TRIMMERS. The Bilby carries both aerodynamic elevator and rudder trims. This enables the aircraft to be flown hands off at any airspeed. The rudder trim is really just a bonus to get rid of the torque effects of the R582 engine but the elevator trim is excellent – particularly for training as the original Thruster system is not only pathetic but also works in ‘sense reverse’ so is not a good training tool.



The systems are very simple, will be therefore cheap and can be easily fitted in an hour or so with simple hand tools and a set of directions.



Continued in Part 2



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