Jump to content

Thruster 2 Seat CAO95.25 Compliance & Modifications.

Guest TOSGcentral

Recommended Posts

Guest TOSGcentral

The prime purpose of this post is to provide guidance to assist buyers in unknowingly contracting for illegally modified and non-compliant aircraft offered for sale, and therefore the consequent criminal and civil litigation that could result – or – a substantial financial loss when it is found the aircraft cannot be registered or easily resold other than for parts.


The bulk of the list given below is extracted from a manual “Thruster 2 Seat Identification Guide For Owners and Inspectors” that is available from TOSG at a cost (inclusive of postage) of $32.00. Firstly, some notes to put the situation in clear context.


COMPLIANCE BASIS. The 2 seater Thrusters (other than the exclusions given below) were built under CAO 95.25 as a basic form of design and operation. This means that they may not be operated legally other than in the same format as they left the factory – or – under modification or retrofit options that have approval under a CAR35 Engineer and this will be recorded in the aircraft’s documention.


In addition the aircraft must be currently registered with RAAus and the pilot be a current financial member of RAAus and suitably certificated to fly the aircraft in the mode being adopted on individual flights. The exceptions to this is if the aircraft is operated only and entirely within the confines of the owner’s property (eg the aircraft is no different from a non-registered motor bike or other farm vehicle on a large property).


‘CULTURAL’ ATTITUDES & PROBLEMS. Typically many aircraft have virtually NO documentation at the point of sale and the attitude of the ultralight movement generally to formal log book keeping has been/is so poor that this is the central cause of non-compliance issues.


The Australian Thruster factory is, to all intents and purposes, totally defunct and no support is available from there to assist owners either actual or prospective. In addition – neither RAAus nor CASA apparently has retained compliance records for reference. That itself is further confused by the fact that across the entire Thruster marque there are nearly 60 identifiable models, marks and prototypes – plus considerable hyridisation. That is a massive number of variants in a single ultralight type range!


The result, in conjunction with the age of the Thruster range, has resulted in ‘culturally induced’ attitude changes to compliance and therefore legality. There are two extremes to this.


At the user level an attitude has crept in that the 95.25 Thrusters are really now no different from aircraft built under 95.10 and you can do much as you wish with them. This is compounded a by a very open responsibility ‘system’ where L1 & L2 Maintenance Authority holders have carte blanche to rebuild and reinstate certified aircraft. This may include re-manufacturing major components and this is quite legal and there is no harm in it if the task is discharged responsibly from correct base materials.


Where the problem arises is if the re-builder includes a modification and assumes that it is authorised because it has been seen, or heard of, on another similar type aircraft – or – very simply thinks it is a ‘good idea’!


At the other end of the scale inspectors and authorities may give owners an unreasonably hard time by insisting on ultra-strict adherence to compliance at ridiculous extremes! This is primarly caused by an insufficient knowledge of the aircraft types even if the inspector may have considerable experience on a couple of Thruster types.


Current examples of this situation are a senior RAAus official stating that the R582 engine cannot be fitted to the Gemini because it was never produced by the factory with an R582 motor and anyway the engine will ‘shake the aircraft apart’! Firstly, the R582 engine was not available when the Gemini was built so could hardly have been fitted! Secondly, the R582 is about the best thing that could happen to a Gemini (if the weight and balance is suitably adjusted) and DOES NOT shake the aircraft apart if fitted correctly!


Another instance is complaint about an ex-military seat harness being fitted to a T500 that is far superior to standard ultralight harness and uses exactly the same mountings. The reason given was ‘the factory never fitted those so it is an illegal modification’.


The compliance issue does require some rational thinking but where you draw the dividing line is presently down to ‘opinion’. TOSG has put in years of work to draw that line responsibly so that the design ethic and purpose of 95.25 is preserved, but owners have the safety and protection of advancement over the years by improvements that were not available when the aircraft were first built.


AUTHORITY. TOSG is NOT an Airworthiness Authority! It is however the closest thing that Thruster operators have to an informed ‘authority’ by virtue of the 13 years research and practical experience conducted on the marque.


In addition – the listing that follows has been cleared by the RAAus Tech Office and the current Tech Manager (Chris Kiehn) is taking a most pro-active and rational view of the area.


Any items marked with an asterisk either have some form of ‘cloud’ over them or are items that are currently under development and awaiting their individual Engineering Orders. I will progressively edit this post by removing the asterisks as each area is cleared up.


EXCEPTIONS. The following list does not encompass the 95.10 single seaters, the pre- 95.25 certified two seaters (the Thruster 84 TPT & Utility ‘Glasshouse’ & Gemini X), the Prototype Thrusters (with the exception of the Gemini Prototype in its latest configuration), or the developmental models that are now registered, or eligible to be registered, in RAAus 19 series registration (Flying Fox, Flash & Bilby).


RETROFITTING. With the 95.25 two seaters (Gemini A & B, TST, TST L, TST E, T300 & T500) they may be more clearly seen as not individual types but as successive marks of a core type. Their size and geometry, wing sections, design parameters etc have not changed from the first approved Gemini Prototype.


The evolution of the Thruster two seater has therefore been one of progressive strengthening, efficiency and drag reduction. The present T500 may be more clearly seen as actually a Gemini Mk 4 rather than as an entirely new type when it was first produced.


This does not strictly apply to the T600/Vision 600 that were manufactured under a different design order and are substantially different (few ‘600 parts are interchangeable with earlier models) but retained the original Thruster two seat size and design construction etc.


Therefore retrofitting of later improvements is an option that may be applied. There was only a 2 year time interval between the 95.25 Gemini Prototype flying and the introduction of the T500 but much happened in those two years and owners should have access to the improved safety that resulted from that time period.




The following engines are certified for the various models of 95.25 Thrusters:


ROTAX - R503, R532, R582 & R912.




(a) R912. A provision of the certification of this engine was (apparently) that the factory had to fit them due to aircraft weight and balance issues and the radically different engine bearers. As the factory is now defunct it means that this engine is no longer an option.


(b) Jabiru 2200. This engine is certified for the T600 and Vision 600 models but NOT for the 95.25 Thrusters. There is no reason that the engine cannot be fitted but will have to be certified for the type via Engineering Order and that has not yet been done. A very different engine mount is required. RAAus are likely to decline applications for registration or re-registration.


© Rotax R618. This engine is a beefed-up R582, is heavier and has more horsepower. It fits the standard mount so can be installed easily. It is NOT yet certified for 95.25 Thrusters. RAAus is likely to decline applications for registration or re-registration.


(d) BMW R100/R80. TOSG is currently getting Thruster installation of these engines certified but that process is not yet finished.




The following propellers are certified for the various models of 95.25 Thrusters:


(a) Catto 2 blade wooden. (These propellers are not currently available new in Australia)


(b) Sweetapple 2 blade wooden is seen by RAAus as an acceptable alternative to the Catto.


© Aerofibre Brolga ground adjustable 3 blade in various diameters.


(d) Aerofibre Brolga ground adjustable 2 blade in various diameters.


(e) Propeller spinners if securely mounted as designed.




A trap on compliance and buying is when a currently registered aircraft is modified and RAAus are not informed. This does happen and quite frequently! The crunch comes when the mandatory UACR/UAR is conducted and the situation may then come out and you will be declined registration – you therefore cannot legally fly the aircraft!


Normally it is the responsibility of the seller to obtain these reports but, once again, the eager buyer agrees to have the inspection done – after buying the aircraft, that they are now stuck with!


This may be quite innocent because neither seller nor buyer has any clue about compliance. But the Tech Manager does and it can come as a bit of a shock when you find out!




The following is a list of options which may be put on Thruster two seat types up to and including the T500 – providing the aircraft stays within permitted Centre of Gravity Range from any original configuration (i.e. a retrospect re-build) and/or security of any such option is satisfactory to an inspector’s scrutiny under accepted aeronautical practice. Full weight and balance survey results should be demonstrated consequent to any changes and especially with the fitting of larger fuel tanks.


T600 and Vision 600 aircraft will develop their own option and modification lists as production continues. The following list does not apply to these aircraft.


Cockpit Enclosure................ Overhead roof panel in conjunction with a cockpit rear bulkhead.


Cockpit Doors..................... Fitting of cockpit doors to totally enclose the cockpit.


Rear Fuselage Enclosure....... Rear fuselage enclosed aft of cockpit.


Eyebrow Instrument Panel.... A sub-panel above eye level


Instruments & Avionics......... Owner’s choice within space & weight limits


Heavy Duty Undercarriage Insert Chromium-molybdenum steel beam inside alloy axle beam


Alloy Wheels........................ Fitted new to later models and should replace existing plastic wheels


Wheel Brakes...................... Mainly for operations on paved surfaces


Wheel Spats......................... Reduces drag and mud spattering under wings


U/C Leaf Springs................. Single, double and triple depending on use


Pneumatic Tailwheel............. Reduces tail vibration and shock damage on rough airstrips


Pod Fairings......................... Drag reducing side strakes or mouldings. Reinforcing mouldings


Top Mouldings..................... Fairings between cockpit roof and wing on enclosed models


Strut Fairings........................ Plastic aerofoil sections held by hose clamps – watch orientation


Aerodynamic Lift Struts........ Same material as Jabiru, Skyfox with Thruster ends


*Aerodynamic Trimmers...... Bowden operated elevator and/or rudder trimmer replacing bungy system


Fixed Trimmer...................... Elevator and Rudder fixed trimmer installations


Tail Unit Formers................. Foam insert ‘ribs’ to tension skins on tail unit components and increase control effectiveness


GRP Wing Tip Formers........ Replacements for TST L onwards chromium-molybdenum steel formers


Fuel Tanks........................... GRP barrel to 45 ltrs; Alloy barrel to 75 ltrs; Stainless oblong to 60 ltr


Ultralam Skins...................... Alternative to Dacron skins


Engines................................ Rotax 503, 532, 582 & 912


Propellers............................. Two Blade Wood, Catto 2 Blade Wooden, & Aero-Fibre Brolga 2 and 3 blade composite.


Engine Off Set Bearers……Introduced with the R582 and counter engine torque effects through the rudder circuit.


*Flapperons The Gemini A was tested with flapperons and flapperons on Thrusters have been approved for many years in NZ. Technical data no longer exists in Australia. TOSG is having this missing technical data replaced by CAR35 Engineers. It is anticipated that an approved modification will also be made to Visions for flapperon inclusion – but that cannot be documented at this stage.


*Single piece chromealloy undercarriage carry beam. A one piece replacement for the previous two piece assembly that is now no longer available.


*Pods. Early development Swift pods are available from TOSG and are legal on any two seater. The more advanced ones are under development and await Engineering Orders.


*Reduced Angle of Incidence wing spar front mounting bracket. Under development and awaiting Engineering Orders.


*Reduced Interference Drag fairing above cockpit and revised cockpit panel roof assembly. Under development and awaiting Engineering Orders,


*450 kg MTOW upgrade modification. Under development and awaiting engineering orders.


CONCLUSION. Please post questions or queries on the ‘Compliance & Modifications Q & A thread.


TOSG will willingly give individual and confidential advice on type identification and compliance issues.



Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...