Why did we design it this way?
To start with, this project is designed to meet the new CAA regulation (CAA General Exemption 633) which limits us to a single seat aircraft of less than 115 kg empty weight and under 10 kg/m2 wing loading.
We start from the low weight and wing loading. That means a lot of wing area!
We soon discovered that a canard gives the best solution for these requirements:
- 1.We can minimise the wing area, as a canard has a lifting foreplane.
- 2.The canard leads us to a pusher layout, with the engine mounted quite high up to provide prop clearance.
- 3.It provides an excellent position for the pilot, who is forward of the wing, maximising visibility and providing easy access.
We decided to go for less than the maximum weight in order to reduce the wing area (we’ve gone for 114 kg and 11.3 m2 total area; 9.6 m2 wing and 1.7m2 canard).
The all-carbon structure enables us to provide an exceptional finish with complex contours, and hence low drag.
To minimise wing weight, we’ve gone for a low aspect ratio, and this also enables us to put the fins/rudders outboard with negligible weight penalty. (A fin above the engine would greatly restrict access.) The fins also increase the effective aspect ratio and thus reduce induced drag.
The target engine is a wankel engine from Aixro which produces 40 hp – about the best power/weight ratio available. It is water cooled and comes with an electric starter. TBO is supposed to be 500 hours with ceramic tips. It’s being converted for aircraft use by two UK outfits, Parajet (Rotron) and Escapade (Aero 40), so we’re following both closely.
Noise is minimised in several ways. The engine is positioned above the wing, which shields much of the engine noise from the ground. The exhaust silencer exhausts upwards and the cowl is acoustically lined. The propeller is designed to minimise tip vortices.
The canard is fixed but it has a large, full span elevator to give plenty of control force and a high maximum lift.
No wing flap is needed, and this removes one problem with canards – pitch control during landing.
We’ve put in large, balanced ailerons to provide light controls and a fast roll rate.
This layout gives us a simple, light structural layout and a good c.g. range.
The pilot is forward of the wing where he/she gets fabulous visibility and easy access.
Engine maintenance should be very easy as the e-Go has a large engine cowl, which also encloses the accessories and fuel tank.
The structure is monocoque, with a thin skin, reinforced with webs, frames and stringers to distribute point loads. Carbon fibre sheet is used for skins. The wing spars, ribs and fuselage frames use a carbon fibre/ honeycomb or foam sandwich.
We owe a debt to Dyn’Aero where Christophe Robin has shown how to design an exceptionally light, fast, responsive plane using similar materials. Though the e-Go goes much further, with even better materials and a far lighter structure.
The fuselage has a singly ply skin in most areas, and a beam each side (glued to the skin and frames) to carry loads between the foreplane, undercarriage, wing and engine. The pilot seat forms one of the fuselage frames.
The wing also has a thin skin, plus two spars (slightly lighter than one). Rib and internal structure may be patentable – so no more for now!. The wing has simple attachments to the fuselage, via carry-through spars.
We’re focussing also on a very small parts count, to minimise cost.