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'Mer Island: a short strip with unsround conditions.

WHAT WENT WRONG

DENINEDIN PAR-After take-off from a remote island in the TorresStrait, this pilot heard a dull thump. Wrapped aroundthe wheel and the strut was a liana vine.

David W Mathison

0 N A TROPICAL FRIDAYEVENING ATabout 6 o'clock, I landed on MerIsland in the Torres Strait in myfour-seater Cessna 172. The flight fromThursday Island had been uneventful.

My w ife and land two high school studentswere delighted at the prospect of a weekendaway from the m ore comm ercialised life onT hursday Island.

W e were met by the families of the studentsat the strip.

O n the trip down the hill the height of thestrip above sea level was brought home to me.I had been told that one of the hills on theisland had been bulldozed to create a wide,grassy airfield and that at both ends of this,the island fell away withsteep and rugged slopesinto the sea.

But the strip regularlytook a two-enginedIslander which madecommercial runs aroundthe To rres Strait, so I w asnot overly concernedabout take-off.

By 7 pm, my wife and Iwere ensconced in a roo m full of shadows, lis-tening to the sea outside lapping on the sand.T he weekend was a sublime dream. R ecentrains had taken the edge off the heat. WhenSunday afternoon arrived w e felt cheated that

time should intrude on "paradise".The trailer was loaded. We hopped on

board and the students and their familiesjoined us for the ride up to the strip.

A fter sincerely felt farewells, the four of usboarded the plane taking with us some smallgifts and a few coco nuts.

I w as satisfied that we were well w ithin thetake-off parameters of the Cessna as w e hadburnt off considerable fuel. I rememberthinking as I was taxiing out that a short-fieldtake-off might be appropriate as I had a fullcomplement of people aboard. It was not a

long strip, and I was not completely sure of

the ground conditions. Also, I was not anexperienced pilot and I had only recentlybought the aircraft, so I think there was a cer-tain desire to prove myself a responsible andthoughtful pilot - even at the risk of beingover cautious.

I aligned the nose of the plane with the centreof the strip and did the pre-flight checks. Ithen put dow n flap, stood o n the brakes andapplied full power. I distinctly rememberrolling forward and waving to the familieswaiting by the edg e of the airstrip.

My initial confidence disappeared in thenext few seconds. I remember turning to mywife and saying, "I'm not getting enough speed "I could see the end of the strip looming ahead

with only sky beyo nd it.A lthough I was not yet

at lift-off speed I was veryclose to it, so I chose topull back on the controls.The plane lifted off andthen, unnervingly, settledback on to a fast disap-pearing airstrip. I thoughtof trying to stop, but Iknew it was too late.

I could do nothing else but pull back againon the controls. The end of the airstrip wasimmediately in front of us, then suddenlybelow the plane. We were airborne and wewere sinking.

T here, right in front of me, was a ridge ofstone and grass topped with tall trees. We werein a sort of valley or hollow h eading directlyfor dense timber. I remember thinking - withabsolute clarity - that to pull back excessivelyon the controls would be fatal; we would cer-tainly stall. But I had to lift the nose.

I kept forw ard pressure on the controls fora few more seconds to gain airspeed, then Ipulled back firmly, but gently - overriding thefatal instinct - and almost at that mo ment, attree top level, I heard a dull thump.

W e were flying away normally, it seemed,

and gaining height. I then looked out m y side

of the plane to see what the noise had been.W rapped around the wheel and its strut wasa liana vine.

After checking thoroughly, I determinedthere were no other problems. We were safeenough in the air, but I was left with a nagging

concern about landing with a vine around awheel. Further inspections of the wheel con-vinced me we could land safely as the vine wasnot likely to present a serious problem.

T his has been my only close encounter withthe prospect of catastrophe.

But why had I got into this predicament inthe first place? There were a number of nowobvious reasons which at the time seemed rel-atively unimportant. The brief showers thathad fallen over the previous days had softenedthe ground. The well-rolled soil of the airstripdid not escape this softening. T his was pro-

nounced in the centre of the strip. The tyrepressure of the C essna wheels was not as highas it should have been for the co nditions (yetI carried a hand pump with me). A nother sig-nificant factor was the increase in grassgrowth o n the strip over the previous days.

The plane liftedoff and then,unnervingly, settledback onto a fast dis-appearing airstrip.

10 FLIGHT SAFETY AUSTRALIA AUTUMN 1997

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FLIGHT SAFETY AUSTRALIA AUTUMN 1997 11

N U S ISUimportance of thor-ough pre-flight

preparation, especially when operating onunfamiliar grassy strips. It also em phasises theneed to have a sound knowledge of your air-craft and of the factors affecting the aircraft 'sperformance . It can sometimes be difficult toswitch from a relaxed, holiday mode to thedisciplined, professional attitude requ ired forflight operations. How ever, flying is not likedriving a car; we can't simply hop in or go o nthe hunch that we are well within the take-offparameters .

Before take-off, the pilot should have com -pleted a weight and balance sh eet for the air-craft and calculated his take-off distance usingthe appropriate performance charts in theCessna 172 flight manual. His calculationshould have taken into account all factorsaffecting the performance of the aircraft , inthis case, density height (warm day, high fieldelevation) and the type of runway surface(grass strip, soft/short field). The pilot shouldalso have selected an abort point before tak-ing-off. This would have ensured that therewas no hesitation in making a decision toabort if the aircraft has not reached take-offspeed by the predetermined point.

While it is true that most light aircraft, suchas the Cessna 172, can take-off in less than

500m, it must be remembered that perfor-

mance ch arts are based on the following con-ditions:

ea level.Standard temperature (15°C).Hard level runway o r short dry grass.Nil wind.New aircraft with the engine in excellent

condition.Any ch ange in these conditions can increase

the take-off distance required quite substan-tially. For exam ple, for each 1,000 feet abovesea level, most light aircraft handbooks will rec-omm end adding at least 10 per cent to the take-off distance required. An increase o f 10°C canadd 20per cent to thetake-off run. In addi-tion, the take-off dis-tance can be increasedby a further 25 per centfor operations in longor wet grass, or whentaking-off from a softfield (see diagram).

The pilot indicatedthat he put downflap , but he does notsay what flap setting heused. While the Cessna172 pilot operatinghandbook states that10° of flap should beused for short or softfield take-off, it must

be remembered that

the use of excessive flap, in this case more than10° during take-off, can greatly deteriorate

climbing performance.Finally, the pilot may also have succumbed

to the subtle pressures of showing h is friendshe was a skilled new aircraft owner.

This, coupled with a lack of adequate pre-flight preparation, can easily trap the unwarypilot.

Prue Anderson and Irene Henley depar tment ofaviation studies University of W estern SydneyMacarthur.