From The Cockpit – DHC Chipmunk

As its training base, the AAC flies Chipmunks (its basic trainer), A1 Mk1 Turbine Islanders and Lynx helicopters from Middle Wallop. It used to operate Beavers until their recent replacement. At Middle Wallop, only the takeoff and landing direction of the day is laid out on the grass. The field surface is roughly undulating, not only providing a test of an aeroplane’s undercarriage suspension but also providing an experience which can not be dissimilar to that of the field operations of the earliest aeroplanes.

Although the ‘Chippie’ continues to be a great training aircraft after more than forty years, the majority of remaining aircraft find themselves in private or recreational use. De Havilland Aircraft of Canada Limited was established in 1928 as a sales and servicing company for its parent company, De Havilland Ltd of Hatfield, England. World War II saw the commencement of aircraft manufacture at DHC, while after the war the company continued with aircraft production, commencing their own designs starting with the DHC-1 Chipmunk. Although the initial production run was completed in 1951, the type went back into production in 1955 in order to meet new RCAF requirements. Total Canadian build was 218; sixty were also built under licence in Portugal. However the real boost to the type came back at Hatfield. Construction started there after the DHC-1 was selected to replace the DH82 Tiger Moth as the standard ab initio trainer for the RAF Volunteer Reserve squadrons. Designated the T. 10, it was powered by the Gypsy Major 8 of 145bhp. The 1,000th Hatfield built Chipmunk was completed in February 1956; by that time it had entered service as a trainer in 22 of the world’s air forces. As a low time PPL I did my tailwheel endorsement on Chipmunk VH-RSK, then owned and operated by the Aero Club of Point Cook, the RAAF’s primary training base which has a history nearly as long as that of Middle Wallop in England.

The Gypsy Major 8 is an inverted inline straight four. On unmodified T. 1 Os it is either cartridge started or propeller swung. In both cases, a cold engine should first have its cylinders primed by pulling through the propeller about six revs after the carburettor has been flooded. The cartridge starter is energised by pulling the control to its full travel, about nine inches. The control is located on the far right side of the front panel. Pulling it indexes and fires the cartridge. For cartridge starting both magnetos are switched on, whilst the prop is hand swung with only the starboard (impulse) magneto switched on.

The engine is supplied with fuel from two flexible 9imp gal tanks, mounted one in each wing. Fuel is simply routed via nonreturn valves to a T-junction and through the fuel cock and two engine driven fuel pumps (ENFP) to the carburettor: Each ENFP has a hand priming lever. The rear pump lever is extended so that, for start, when the carb flooding device is held out, the lever can be operated until fuel drips from the overflow vent at the bottom of the engine. Engine start should not be attempted until fuel has ceased draining. The trick with this procedure is to prime the engine with the correct amount of fuel without over-priming, which will prevent starting.

If the Gypsy Major’s starting procedure is touchy, then the rest of the aeroplane’s operations are straightforward. After start checks consist of setting and uncaging the direction indicator (DI), checking the horizon, radio checks and setting the QNH. An engine driven vacuum pump provides the suction power for these and the two needle turn-and-slip indicators (front and rear). Likewise an engine driven generator and a battery power the 24 volt electrical system. Electrical services are limited – radio, oil temp gauges and lights are about it. The master electrical switch has a nuance – it is marked Flight er Ground. In the latter position the battery is isolated from the busbar, which is however powered from the generator when the engine is running. Flight is therefore the normal position selected before engine start, thereby connecting both battery and generator to power the electrical services.

The Chipmunk’s wing material is a mixture. The single spar is all metal, stiffened by a semi-monocoque metal D-section leading edge, while aft of the spar, covering is fabric. Similarly, the ailerons are metal framed and fabric covered,while the slotted flaps on the other hand are all metal. The D-section incorporates increased camber (ie drooped leading edge) towards the wingtips, varying the wing section from the modified NACA 2415/ USA 35B at the wing roots:

The fuselage and tailplane are all metal, semi-monocoque design. The main landing gear struts have rubber compression type shock absorbing struts. The tailwheel is level suspended on a strut. The mainwheel brakes are operated by a manual lever on the left side of the cockpit. The brake lever is pawl locked in position using a sliding collar for the lever grip. Brake lever position is changed by releasing the pawl with slight backward movement of the lever.

Taxying the Chipmunk is straightforward. The top of the (albeit slim) cowling does obstruct forward view on the ground, a small weave is necessary to clear the nose. The brake lever is set about halfway back, providing differential braking. Fully back it stops and holds the aircraft. The single sliding canopy can be locked in either of two intermediate positions, or to the fully open position. Although the canopy cannot be jettisoned, the port sidepanels may be, in the event of an emergency. On VH-RSK, with instructor Dave Burley onboard, I had the disconcerting experience of the front panel loosening and blowing out in flight – to flutter down unobtrusively upon a market garden near Werribee.

Takeoff can be made with either flap up or lowered fifteen degrees. The aircraft tends to swing to starboard with throttle opening – readily controllable with rudder. Lift off at 45 knots, climb at 70 knots after flap retraction, with full throttle and mixture full rich. Maximum rate of climb airspeed is 65 knots.

If there is a word for the Chipmunk’s handling I suggest it is ‘gentlemanly’. The flying controls are well harmonised. Although I do not think the aircraft is highly manoeuvrable, it is pleasant and responsive in the pitching and rolling planes. Elevator trimming is readily effected using the trimmer wheel located forward and to the left of the seat base. The Chipmunk maintains its stability down to low flying speeds – endurance speed is 60-65 knots, best range speed is 90-95 knots (at 5,000ft). Fuel consumption at this speed and altitude is 6. 5imp gal per hour, giving two hours endurance with 45min reserve.

Flap Up, stalling speed is 45 knots; in the flap Down approach configuration it is 35 knots. The stall is characterised by some elevator buffeting onsetting at about 3 knots before the stall. Power off, the nose drops at the stall, to be followed by a pitch oscillation tendency. Held in the stall with a backstick, buffet level increases, and then wing droop occurrence is likely. Power on, the buffet level and wing drop tendency are greater.

Depending upon CG position (solo is from the front seat only), the Chipmunk may be difficult to spin. Out-of-turn aileron assists entry into a stable spin. VH-RSK was fitted with the de Havilland tailplane root strakes which, by the application of controlled vortices flow, were designed to ensure rudder and elevator effectiveness are both maintained at the high angle-of-attack of the spin. However with due regard for RSK’s longevity, the Point Cook Club had restricted its envelope to incipient spins only. Held in however, the Chipmunk will tend to flatten its spin. Recovery is predictable, taking up to 11/2 turns, depending upon the state of the spin. Basic aerobatics can be readily performed by the DHC-1, and still are by the RAF Elementary Flying School fleet. An entry speed of 130 knots will see the aircraft around a loop, whilst rolls can be happily performed at 120 knots. These speeds hold a good margin from the Vne of173 knots. lnflight the canopy can be opened ifrequired (has no associated change), although it should be closed for spinning.

In the circuit, flaps 15 can be lowered at 93 knots. Extension is accompanied by slight nose-down change of trim. An initial approach speed of 60 knots should be reduced to a threshold speed of 55 knots on a normal approach. In smooth air, a precautionary landing speed of 50 knots can be employed.

The Chipmunk can only be considered as a sport. However it is a prestige one. With the last remaining service Chipmunks from various parts of the world now being retired, it is likely that we shall see a slightly increased number on the local register. Let’s hope