Monday, 29 October 2007

DECISIONS,DECISIONS


Cherokee Six 300. Bougainville Island 1965


It was a short twenty minute flight from the small town of Buin at the southern end of the big island of Bougainville in pre-independence Papua New Guinea to Kieta further up the coast.

I was expecting no surprises over this familiar route and with no passengers or cargo the powerful 300 HP Lycoming easily lifted the lightly loaded Cherokee to a safe 3000 feet and I throttled back for the few minutes' level flight remaining before descent into Aropa Airport.

The late-afternoon weather was the usual mixture of scattered showers near the coast and a line of big cu-nims to port where the terrain rose steeply to five thousand feet or more culminating in the seven thousand foot extinct volcano, Mount Taroka with it's crescent shaped hanging lake at the five thousand foot level.

Below, a uniform carpet of thick jungle covered every inch of ground right down to the coast. Typical New Guinea conditions with nowhere to even consider a survivable forced landing. The few sandy beaches were too narrow and short and the only options after an engine failure were to ditch into shallow water near the coast or onto the just-covered barrier reef a few miles out to sea. neither of these was an attractive prospect, but better than flying into the solid jungle below.

The big Lycoming purred contentedly away for a few minutes more and I reached for the throttle to reduce power as the last ridge loomed ahead.

Suddenly, the smooth hum from the engine changed to a shudder which shook the whole aircraft; revs dropped and manifold pressure followed. Full rich mixture had no effect; a quick cycle through left,right and back to both magnetoes changed nothing, neither did switching fuel tanks and bringing the electric fuel pump on line.

First things first. I banked hard right and headed for the coast away from the forbidding terrain below while considering the possibile causes of the rough running. Dropped valve? Tip missing on a propeller blade ? Timing gear slipped? Plug lead fallen off? Ran over a black cat on take-off? "Aviate,navigate,communicate"… The first two disposed of I called Flight Service at Rabaul, far away on the other side of the Solomon Sea and advised them of my situation.
"Are you declaring an emergency?"
" No, but I'm tracking coastal to Aropa for a straight in approach and will call on final"
"Roger"

I was, by then, level at 1500 feet with the steep coastal hills to port and a reassuring light green band of shallow water under the wings.

The vibration got no worse and I made a straight-in approach to Aropa, landed without incident and taxied up to the one and only hangar where engineers, one carrying a CO2 extinguisher at the ready who had heard the whole thing on their hangar radio surrounded the aircraft making throat-cutting gestures which I interpreted as "shut it down NOW."

The reason was soon clear; from both sides of the long engine cowling, a vivid green stain spread fan-like along the fuselage. Avgas. The entire engine compartment was a bomb waiting to explode.

A quick inspection revealed a broken high-pressure injector fuel line which had produced a spray of 100/130 Avgas, filling the cowled engine compartment with an explosive mixture of vaporised fuel and air which neither the hot exhaust manifold nor electrical discharges from the magnetoes and alternator had ignited.

Even now, after a lapse of 30 years I like to think I would have immediately shut the engine down and ditched in the shallows had I known the cause of the rough running, and not continued flying to a safe landing at Aropa.

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