Summary: Todays interview is with Mike Sharples who has designed and built a light aircraft called the Avocet at his property in rural South Australia. Mike first appeared on the podcast on episode 3 where we talked about Kit Building.
Show Notes – Interview
Mike had previously had a J-230 aircraft and wanted space to include a motorbike so he could get around once he flew to destinations.
Mike notes that the aircraft is still in the prototype stage and has flown 60 hours in the aircraft so far.
Description of the Aircraft – It looks like a miniature C-17, high wing, turret mounted pusher prop driven by the 6 cylinder Jabiru Engine. Mike notes it looks like a lake amphibian with a high wing and high tail to allow a low slung cargo section at the back.
The Avocet on Mikes Strip.
Amphibian – Mike said it could be converted to an amphibian at a later stage and has some designs drawn up for this.
An example of a ‘Lake’ Amphibian to illustrate the likeness of the two aircraft.
Category of Aircraft – It was designed based on a proposed weight limit increase to which did not get approved. At the moment the aircraft could only be registered as an experimental (VH registration) which would require a pilot to hold a PPL to fly.
Other potential missions – Mike notes it could be a single bed ambulance but it would be difficult to get certified. Mike notes it is quite a good STOL aircraft and you could operate out of a strip around 400 meters long.
First Step in the design process – Draw it out in a side profile view and tried to fit in a 6 foot tall person in. Mike did a theoretical weight and balance and it seemed to all work at each stage. Mike drew the pan, side and front elevations and his son-in-law built it as a 3D Model.
Making the Plug – Sectioned off each that plan view to every 400mm and take a front elevation (like the ribs on a spine) and filled it full of foam and put on the fibreglass. The plug took around 3 months and probably another 3 weeks to make the moulds. Then he waited until it was cooler to do the layups (where you make the part in the mould), putting on a gel cage, layer of resin, layer of cloth, wetted out with a roller, more cloth and core mats. It takes about 10 hours to do half a fuselage. It all hardens up and you pop the part out.
Purchasing the Jabiru Parts – Mike purchased the wings, wheels ($40k of Jabiru parts in the kit – 20k of that for the engine).
Mounting the Engine – first time using four pillars angled in with a chromolly frame for the engine. Later on Mike made a turret for the engine (like a wing on its side). The advantages are that the engine is off the ground for bush and secondary strips and is safer for ground running of the engine.
Wingtips for the J-230 wing – provides greater handling at lower speeds.
Test Flying – Mike used the same techniques used for any new aircraft. Mike noted it flew quite well, it does not need much control input having the engine on top of the Centre of Gravity. Mike notes that first flights can be very risky.
In turbulence – Mike noted it had a ‘dutch roll’ in turbulence which meant the aircraft would scribe a figure 8 in the air, Mike had to try 3 tails to remove this characteristic from the aircraft. Mike notes that some larger aircraft such as the B-17 had similar issues in their development.
Explanation of a ‘Dutch Roll’ to explain the problems that Mike encountered and fixed with the Avocet
Showing the Aircraft at Airshows – Mike noted he was keen to fly to Avalon but he noted that Ultralights can be damaged in the summer storms.
Feedback on the aircraft – Rod Stiff from Jabiru noted the aircraft was ‘well done’ and Howard Hughes from Australian Lightwing was impressed with it.
Uses for the aircraft – Mike notes the aircraft could have many uses including to go camping, to move stores on a farm and to hold a motorbike. He notes it like a Sky Ute and was thinking of naming it the ‘Skute’. He noted it would be a nice twin but this can’t be flown under the ultralight rules.
Specifications – 408kg empty, MTOW 700 kgs, single seater under the ultralight class, it cruises at 100 knots with a 62 inch prop with a 54 inch pitch running a Jabiru 6 cylinder engine with liquid cooled heads and – fuel injection. It also has a fuel injected throttle body and two alternators (20 amps and a 30 amp). It has two batteries (one is for ballast on the front). It has two separate and complete electrical and fuel systems. The redundancy has already saved Mike on one flight where he had contaminated fuel and the motor died at 200 feet. Mike notes it could be made 20 kgs lighter without the redundancy, the idea is to be able to operate the aircraft in remote areas. Mike knows what it is like to have fuel and electrical system failure out in rural areas and that is why he has built the Avocet with redundancy.
The first iteration of the Avocet (Note the rear cargo area)
Next Steps – Have a qualified test pilot explore the envelope to check if the aircraft has nasty habits around the stall. He is tweaking some elements such as getting the venting right in the turret to improve reliability. Mike is looking to take the Avocet around the Airshow circuit in the future.
An Aerial view of Mikes Property.
What do you think of the Avocet? What other uses can you see it being utilised for in the future?
Announcements in the show:
Two listener achievements:
– Scott has passed his flight test
– Terry has soloed in the A22 Foxbat
The Podcast has passed 10,000 downloads!