It is reported that the most common cause of claims on the MAAA Insurance Policy is members getting their fingers into propellers. If you add to these accidents the more minor injuries and the near misses, propellers are the greatest hazard that we face when enjoying flying model aircraft. Of course we all believe that we are very careful ourselves, but the reality is that too many experienced modellers have had a problem, including some resulting in partial amputations.
Many clubs require that a model is restrained during the starting process and this does help a little. Accidents still continue to happen including when the model, with the engine running, is either lifted off or over a restraint. From personal experience, watching someone else’s model spinning round toward you at full power, with a tool box restraining one wing after the pilot’s leg did not hold the other one, is very alarming. My own models also suffer premature ageing at the front end of the fuselage where I hold them whilst pushing back with an electric starter.
Electric models have similar issues. Have any of us honestly not knocked the throttle forward by accident when picking up the transmitter? Even worse, unlike an internal combustion engine, an electric motor does not stop when it hits you.
Is there a better method?
Enter the Airopult. This product has been in development for two years and is now available commercially.
In concept it is simple and elegant, and the engineering is superb.
The unit consists of a Release Assembly with hinged restraints for the horizontal tail. There are then four extension arms which plug in it to allow for different fuselage lengths. The undercarriage restraint adjusters slide onto these and lock.
The undercarriage height adjusters have two optional lengths depending on the height of the wing and these parts are fitted using a simple spring clip. Using a similar clip, a horizontal arm can also be fitted to either length height restraint for use with vertical main undercarriage legs. This is often the case with retractable or tricycle undercarriages.
The unit is set up by fixing the Release Assembly to the ground. For grass and dirt the instructions say use 150mm x 6mm and 80mm x 5mm flat head nails, although I prefer to use 220mm x 6.5mm tent pegs for both positions. These are not only a little longer for extra security but are easier to remove when pushed fully in. For hard surfaces they recommend using 8mm x 100mm coach bolts into pre-drilled holes. Although I have not had the opportunity to test this, I see no reason why it would not work well.
The aircraft is then positioned so that the horizontal tail is pushed up behind the hinged restraints. The extension arms are then locked at the correct angle to get the undercarriage restraint adjusters in the correct position and the right number of extensions are just pushed into place. The undercarriage restraint adjusters are then secured so that they are directly behind the legs with the hinged restraints able to fall forward. For additional security these front restraints can be pegged into position. The aircraft is then firmly restrained in both directions. The main hinge restraints stop it moving forward under power and the undercarriage restraints stop it moving back when an electric starter is applied.
Once the engine is running and adjusted the pilot moves to the back of the aircraft and releases the safety latch on the Release Assembly. After doing that he pushes the foot pedal and the tail restraints drop forward. The aircraft can then be pushed or powered forward,depending on the local club rules. If the tail hits the undercarriage restraints these just drop forward and the aircraft continues to pass over them. A nice touch is that after release the safety latch automatically returns to the safe position.
Once the unit has been set up for a particular aircraft, to set the aircraft up for the next start is extremely simple. The undercarriage restraints are raised to the vertical position and the aircraft pushed back against them. After that it is just a matter of raising the tail restraints till they latch and all is ready again.The question of course is how well does it work in practice? The answer is exceptionally well. The initial set up is extremely quick after the first couple of times.
Several of my fellow club members have also used it and the initial comment is always how well it is engineered. After starting an engine using it, there is a great increase in enthusiasm. It surprises everyone how firmly fixed the aircraft is. The starting process can definitely be one handed, or even better using both hands on the starter to give more control. I have done multiple successive start attempts on a temperamental engine and put the starter straight back on without any concern or hesitation. My fellow club members have sometimes initially commented that it would be most useful on a particular type of aircraft but, once they have used it, realised that it is almost universal in application and quickly get great confidence in it. The unit has been tested with engines up to 160cc and so it should handle all but the largest model aircraft.
I have no commercial association with this product, but as you can probably tell I am very enthusiastic about it. I have read a review that said it is the next major advance in model aviation after the 2.4 GHz revolution. I would not go quite that far myself but I do believe that it contributes to a significant increase in safety for those who use it. Although it is not currently available from an Australian distributor, it can be ordered from the producer in Spain through their web page http://www.airopult.com/en/ and with minimal carriage costs. For me it is now an essential part of my field equipment.