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Tiger Moth Bi-Plane "Flying high"

Leonardo da Vinci said. "when once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you will always long to return."

04 Jul 2010

Dr Clive Fraser

Leonardo da Vinci said, “When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.”

Leonardo never got to fly, but he must have dreamt that as our roads become increasingly congested that there would still be plenty of space left in the sky above.

And for about the same price as an above-average car, it is possible to buy a plane that is easy to fly and relatively cheap to run.

Top of my list would be a Tiger Moth for somewhere between $70K to $110K depending on its condition.

From 1931 to 1944 some 8,868 Tiger Moths were built under licence from the De Havilland Aircraft Company with about 1,085 being built at Bankstown, NSW.

933 remain airborne around the world today, which isn’t a bad effort for a machine approaching its 80th birthday.

In its original form the Tiger Moth’s wings were clad with linen, but modern versions wear ceconite, a type of polyester, which is shrunk by heat over the tubular frame.

The wing configuration differed from the Gypsy Moth in that the wings were moved forward on the fuselage to give the occupants more headroom under the overhead fuel tank.

Unfortunately, this arrangement also moved the centre of lift forward from the plane’s centre of gravity leaving it unbalanced.

In a stroke of genius the designers swept the wings back like a modern jet fighter and also up-swept the lower wings at the tip to provide more ground clearance on bumpy paddock runways.

Mostly powered by a Gipsy Mark 3 motor the Tiger Moth is capable of about 75 knots in level flight and anything up to 130 knots on a downhill run.

My colleague who owns one told me that at that top speed a certain level of divine re-assurance was essential as it does feel close to breaking up in flight.

Thrust in the Australian produced DH-82A is provided by an inverted 4 cylinder engine made in the 1940’s by GMH at Lidcombe in Sydney.

My colleague tells me that the spark plugs are even sold in Kmart as they are the same as those found in many old Holden engines.

The inverted design placed the crankshaft at the top of the engine and provided three benefits.

Firstly, the propeller was lifted further from the ground meaning that the under-carriage can be shorter.

Secondly, there was a better view from the cockpit, as the cylinder heads were no longer obstructing the pilot’s forward vision.

Finally, the higher position of the propeller better aligned the thrust down the centre of the airframe making Tiger Moths more stable in flight.

On the down side an inverted engine did lead to prodigious oil consumption of up to four pints every hour.

An 86 litre fuel tank means that you can be as free as a bird for over two hours with fuel consumption of 30 litres per hour.

This gives a range of about 325 km and averages out at about 21 litres per 100 km.

Excluding any head winds this is about the same fuel economy as a V8 Landcruiser.

One point to note is that when the Tiger Moth is fitted with a wing walker attachment the drag increases by 27%, lowering the top speed back to 58 knots.

And if you are ever asked to wing walk on a Tiger Moth it is important to remember to keep your feet apart to avoid “rudder buffet” which may cause the pilot to lose control.

The Tiger Moth was used to train nearly every RAF Spitfire pilot in WW2 and is still regarded as one of the best ten planes ever made.

 

DH-82A Tiger Moth

For: Simple, reliable mechanicals.

Against: Low thrust, high drag and parachutes were an optional extra.

This plane would suit: Flying doctors.

Specifications:

Inverted 8 valve 4 cylinder Gipsy Major

73 octane ULP

130 hp (97 kW)

Compression ratio 5.25:1

Maximum 2100 rpm on take-off.

21 l/100 km combined.

Cruising speed 75 knots

Stall speed 40 knots

Empty weight 1180 lbs

Gross weight 1825 lbs

$70K to $110K second hand.

$20K for an engine re-build every 1500 hours.

Built – Bankstown, NSW.

 

Safe flying,

Doctor Clive Fraser

doctorclivefraser@hotmail.com.


Published: 04 Jul 2010