Ecureuil .. at last a true rival for the Jetranger

Mouille makes no bones about the Ecureuil concept, it wasn’t easy – it took two years’ hard yakka by Aerospatiale’s joint design/production team to come up with even a preliminary project definition.

But what they emerged with was something really different, an exciting exercise in cost-cutting, economy and outright efficiency.

It was, in Rene Mouille’s own words,” . . . an example of an aeronautical product where a systematic endeavour has been made to maximise cost efficiency by decreasing production costs, by improving performance – particularly as regards the payload carried – and minimising the operating costs by keeping maintenance outgoings as low as possible. ”

In April 1973 the actual project development job began jelling. The Ecureuil’s maiden flight took place on June 30, 1976, with first production deliveries following rapidly at the end of ’77.

World acceptance has been enthusiastic despite some adherence to traditional markets. The machine is currently deep into market exposure at the hands of AGA’s Helicopter Division in Australasia, having just concluded a demonstration tour of Papua New Guinea where it attracted more than just polite attention by virtue of its extensive polycarbonate construction and simplified elements.

So what’s so new and great about the little Squirrel?

• Transmission; the Ecureuil is powered by a free turbine (Turbomeca Arriel with 640shp) needing no clutch unit. As the engine output gear is offset, says Mouille, it’s been possible to dice a pair of bevel gears in the main gearbox; likewise one drive shaft section plus the angled gearboxes needed to route it under the engine.
• Savings have been accomplished in evolving simple pressing stressed structural components; the canopy structure itself boasts a lot of heat-formed polycarbonate panels assembled by hot bonding.
• But the biggest thing to emerge from the Ecureuil exercise has been the main rotor system.

Normal practice when designing helicopter rotor heads is to embody several hinges to get freedom of blade movement in flapping, feathering and drag axes.

There’s also the question of blade damping to consider. Aerospatiale came up with a completely new type of rotor head built around a Starflex head – a virtually maintenance-free head, the central component of which is a “star” built of glass doth and epoxy resin.

Housing spherical thrust bearings, the head masterminds this new radically-efficient assembly.

The Ecureuil’s tail rotor is a continuous-beam moulding, 40 per cent lighter than that worn by the Alouette.

Mouiffe’s eyes literally shine when he describes what has been accomplished by the design team: “The new head contains only 70 parts as against 377 in the Afouette weight has been reduced by 45 per cent and the cost divided by about four . . . the Ecureuif’s main gearbox is much simpler than the Alouette’s, about 12 per cent heavier but with a component reduction of 60 per cent . . . manufacturing time has been cut by 40 per cent.

“Thanks to the generous dimensions of gear teeth and bearing, a virtually indefinite service life and a considerable reduction in maintenance costs are possible. ”

Ansett General Aviation Helicopter Division sales and demonstration pilot Dick Snell (ex-military, as is his Division’s sales engineer David Klein) took up the Ecureuif story at Bankstown during an AADR evaluation mission.

Dick pointed out the various Ecureuif features and filled in Rene Mouille’s gaps as we eyeballed and pre-flighted VHSRA, AGA’s current demonstration Aerospatiale Ecureuil AS- 350ab, worth $32,000 on the day of testing.

Sierra Romeo Alpha bears factory serial No. 1034 – the 34th Ecureuil off the production fine. She was containerised out to Australia after flying at Marignane.

Points made during a walkaround included:

• Solid metal underneath with plenty of polycarbonates above, helping the low weight/added strength equation through infinite-fife materials.
• A no-pillar cabin big enough for six p.o.b. , or two stretchers plus a doctor and in-flight attendant, or a mountain of freight thanks to a QC capability.
• Many automotive-type components in accessories; oil cooler and radiator as used in trucks, thermostat and fan from car production lines, hydraulic pump priced at one-third that of an aeronautical pump . . . and a car’s fuel locking cap.

The Ecureuil’s gearbox section, already robust, is currently being strengthened and simplified to the point where it will only need a boroscope and oil analysis on odd occasions.