Birthday outing

Proving you’re never too old for aerobatics, ACDC celebrates her seventieth with some loops and rolls. By Nick Bloom.

THE OLDEST TIGER Moth still flying – the third built – has just turned seventy. It was registered on 6 February 1933. For her first dozen years G-ACDC was a trainer, first with the de Havilland School, then, when war came, with the RAF. After that she had a good long rest: her second dozen was spent in storage. The Tiger Club got her back in the air and has operated ‘ACDC’ ever since... for a staggering 46 years. If this isn’t the longest continuous operation of any aircraft by a flying club, it must be a strong contender.

Little if anything remains of the original airframe. Jerry Knight, the club’s manager, thinks the most likely candidate for a survivor would be the elevator spar. The wings, engine, rudder, fuselage tubing and undercarriage are all know to have been replaced, inevitable in an aircraft that has flown over 13,000 hours. However, no one knows for certain, and any number of components that have flown through all seven decades might be buried in the structure. Not that it’s the bolts and split pins that count – it’s the continuity and the provenance. For the romantic among us it’s also the aircraft’s soul, which if an inanimate object can have such a thing, lives on through repairs and even major part replacements.

I joined the Tiger Club in 1981. Then as now, applicants had to satisfy a check pilot that they could master ACDC. I flew just enough hours in her to be signed off, and moved on to easier aircraft. In the twenty years since then I have flown aerobatic biplanes from Pitts Specials to Stampes, but a Tiger just once. The club allows ACDC to fly standard level aerobatics and I can think of no quicker way to get the measure of an aircraft (providing it’s cleared for it, of course).

To refuel a Tiger you climb up to stand on the reinforced top to the cowling, unscrew a brass filler cap in the tank, and pour. As the Tiger has a skid at the back, you move it by hoisting the tail. Struts supporting the tailplane give you something solid to lift by, and the tail was surprisingly easy to lift, and ACDC to move, as I pulled it away from the pumps.

This impression of lightness grew while I made my walk-round: the fittings and wires all seemed to be about half the expected diameter. The wings looked thinner, the undercarriage smaller and the struts where they attached at each end, less substantial than on other biplanes. The Tiger ought to be lighter, because the standard engine is 10 hp less than a Stampe’s.

In some ways the aeroplane was delightfully simple - no brakes, no mixture or carb heat controls, no tailwheel, only one set of ailerons, and no adjustment mechanism for the seats (or airstart mechanism, the bane of Renault-engine Stampes). In other ways it was unnecessarily complicated. I disliked the hefty springs that were attached to the control stick via a giant trim lever. The arrangement looked both heavy and superfluous: surely the stick forces would be light. I also had my doubts about the slats in the leading edge of the upper wing that have to be locked for taxying and aerobatics by means of another lever. The idea is that near the stall the slats float out and re-attach the airflow, but in an aircraft with so much wing area I’d expect the stall to be benign.

There was a P-compass in each cockpit. Apart from being the size of a saucepan, these seem designed to confuse by working in the opposite sense to today’s compasses.

Finally anti-spin strakes had been fitted down the fuselage. I believe these w