Too Hot, Too High & Too Short

The following story describes the activities involved in the investigation of a light aircraft accident. Such investigations are usually conducted by the Field Offices of the Bureau located in the State capitals. Major accidents, especially those involving airline aircraft, are carried out by the Canberra-based Central Office of the Bureau. Completed accident investigation reports from the Field Offices are reviewed by Central Office staff. The data from these reports is entered in the Bureau’s computer and, as required, forwarded to ICAO. This information then forms the basis of accident prevention programs, which include amongst other things the Aviation Safety Digest.

It was 4. 30 on a Friday afternoon. The accident investigator, having just finalised a difficult investigation report put his feet up on his desk with some satisfaction and contemplated what he would do during the forthcoming long weekend. Weather reports indicated fine and hot weather. He was rostered for ‘on call’ Home duty that night and Monday, so he had two full days for leisure – barring accidents!

“What are you going to do this weekend John?” The enquiry came from a man who now leaned on the doorway to his office.

“Well Ray, we’ve got a gun club shoot tomorrow, and if the weather holds I think I will go to the beach on Sunday, maybe . . . ”

He was interrupted as the familiar voice of the Boss sounded out. “John, Ray come in for a moment please.”

Seated in the Superintendent’s office they waited as he ran his finger down the duty roster. He addressed John, an experienced investigator.

“Now as you know, Ray has had a couple of months here to learn our procedures. It’s time for him to go out in the field under instruction. John, you are the next one out for an accident so if you get one over the weekend take Ray with you. ”

The rest of the briefing was largely for Ray’s benefit involving the logistic support for an investigation. Later, at home, Johr mentally reviewed the arrangements as he mowed the lawn. The outside telephone bell sounded over the noise of the lawnmower Anticipating his wife’s summons he shut off the mower and answered the phone.

“Senior Operations Controller – Adelaide, John. I’ve got an accident notification for you.”

The investigator recorded the details on his notification pro forma and obtained a contact number for the pilot. The accident site was in the mid-north of the State and he made mental notes of travelling times and planned the route.

After speaking to the pilot by telephone he now had a clearer picture of the circumstances. The pilot had been taking off a ‘bush strip’ and approaching the end of the strip had lifted the aircraft off the ground, raised the undercarriage and then settled back onto the ground wheels up. No injuries to the four or board. Substantial damage. No reported engine malfunction. The pilot had agreed to meet him at the nearest town at 9. 30 a.m. next day to direct him to the site.

Armed with this information he rang the Superintendent and was relieved when he found him at home.

“All right, John,” said the Boss after listening to the details. “I’ll notify Central Office and arrange a police guard for the aircraft Contact Ray and make arrangements. What time will you go away?”

“It’s about a four-hour drive so I’ll leave at 5.30 a. m. and pick Ray up on the way. We won’t need an engineer at this stage as there are no reported malfunctions or failures.”

Next morning, after being dropped by the taxi at the city office he felt for the light switch in the dark and, with practised experience, quickly unlocked the cabinets and collected the investigation kit and camera. The car keys were his last item and he made his way to the garage.

Ray was waiting outside his home – sleepy but eager.

“I’ll drive for a couple of hours and then you can take over, Ray. Should take us about four hours. Grab a map out of the kit will you please? We have to go out through Jamestown.”

The early-hour drive through the city was pleasant and they made it in silence. As they hit the open country Ray said, “Why aren’t we taking an airworthiness engineer with us?”

“Well, on all fatal accidents and when there is an initial indication of a failure or malfunction – we do. In this case the pilot reported there were no engine problems. Often the engine can be test run after recovery and there is a danger of disguising a fault if you do too much dismantling in the field. We’ll check the fuel quantity, and quality, test for water in the fuel – check the main filters and so on, but leave any deep investigation till the plane is recovered! In this case it is easily recoverable and probably repairable. Up in the Territory, of course, and with more damage to the engine, you might have to do extensive on-site checks – especially during the wet season when you can’t move on the roads. ”

The sun was climbing in the east and the dust from the car hung in the air.

“Going to be a scorcher today!” commented John, “40 degrees forecast for Adelaide – a bit warmer where we’re going – sure wish we had an air-conditioned car.” He was glad of Ray’s company. The conversation would keep him alert – especially on the return trip after a long day in the field.

“One of the things you should not do in an investigation is to prejudge the causes or be influenced by a ‘blinding glimpse of the obvious’ as they say. However, I’m willing to wager that, after my talk to the pilot, one of the factors in this accident will be that the strip was too short for the aircraft operation. Four persons on board – nearly full fuel – hot day!” said John.

Ray didn’t reply immediately. “But,” he said, “the pilot has ready access to the aircraft’s flight manual. It contains charts for him to calculate the take-off distance required – and surely he knew how long the strip was!”

“You’d think so, but in all too many accidents of this type the pilot doesn’t check his performance charts or get an accurate report of the strip length. I don’t know why – I’m still trying to find out if it’s a fault in the training system – not enough emphasis on Authorised Landing Area operations – maybe complacency – or a pilot’s false understanding of how much strip length he needs. Anyway, I’m prejudging the issue – something one must not do. Get you into bad habits won’t I?”

Ray took over the driving and John studied the aircraft service manual and operating handbook he’d brought from the office library.

They reached the town for the rendezvous with the pilot and pulled up outside a beautiful turn-of-the-century pub.

“I’ll see if he’s ready,” said John, eager to stretch his legs. To his delight the pilot was waiting and they were soon underway at his directions.

As John had told Ray earlier it is important to put the pilot at ease so they listened as he recounted his story.

“. . . came from interstate with my three passengers who were buying stock. I dropped them at the town airfield and arranged to pick them up at the property as we were running behind schedule.

“At the airfield, I got directions to the strip on the property and learned that the owner flies an 182 out of there – no, I didn’t find out the length of the strip – just formed the impression that it would be suitable for my Arrow.

“I eventually found the strip and waited for a couple of hours. When the passengers arrived, I started up – did a full engine check and taxied to the end of the strip. There was a slight crosswind. I used no flap for take-off, ran up on the brakes and early in the take-off run eased back on the stick. I saw the stall warning light flicker at one stage and eased forward. The end of the strip seemed to be getting close so I pulled her into the air and to increase my acceleration, pulled up the gear. The plane just settled back onto the strip on its belly. I guess it was a case of too short a strip on a hot day with a high strip altitude! – My fault I guess.”

“Could be,” said John in a non-committal tone. “The reason we investigate accidents is for accident prevention – not to apportion blame. We want to determine what happened and more importantly why it happened. Then we can use this information to prevent further accidents from similar causes.”

“Take the next turn left,” said the pilot, “you’ll be able to see the strip’s windsock over the next rise.”

They drove alongside the plane at the edge of the strip. A uniformed policeman came over from his tent. After introductions, John thanked him for his assistance, yarned for a short while and excused himself to start work.

“The first thing we’ll do,” said John, addressing both Ray and the pilot, “is to photograph the plane and all the ground marks. Then we’ll do a complete crash site survey before looking at the plane. You can never take too many photos, Ray! I suggest you make an independent site sketch while the pilot and I use the distance measuring wheel to check the strip length – it’s still reading in feet by the way.”

Starting at the end of the strip the plane’s wheel tracks were obvious.

“Set the wheelcounter to zero and we’ll start from here,” directed John.

Following the tracks, it was clear that the plane was rolling normally – no apparent binding of the brakes and as they progressed they got fainter.

“I think it was about here I applied back stick,” commented the pilot.

A bit further along the right wheel track was very faint and John stopped at a scrape mark between the mainwheel tracks – it was not the nosewheel track.

As if to answer John’s unspoken query, the pilot said “One of my passengers reckoned he heard the tail scrape on the ground but I didn’t think the nose was that high!”

“Well,” replied John – “with both mainwheels down the only thing on centre line, apart from the nosewheel, that could contact the ground would be the tail skid. ”

As they continued, measuring and sketching, the ground marks told their own story.

It became evident where the plane had lifted off, skipped, become airborne again and then settled on its belly. Gouges made by the aircraft entry step and finally propeller slashes and scrapes of the belly and aerials led up to the aircraft wreckage.

“We’ll continue on and measure the strip length,” said John. At the end of the strip the distance measuring wheel indicated 2112 feet.

“All right,” said John, “let’s have a look at the weight and balance, and take-off performance. ”

With the pilot supplying details from the flight manual and weights of passengers’ baggage and fuel (cross-checked from a visual inspection of the tanks) the all-up-weight of the aircraft was soon derived.

“2571 lbs,” exclaimed John, “what’s your maximum allowable all-up-weight?”

After replying “2650 lbs”, the pilot paused. “That means I must have been over max after my last refuelling stop. ”

“Okay,” said John, “now let’s have a look at how much real estate you required – I checked the strip on the inclinometer as having a zero gradient overall and it’s a smooth dirt surface. Let’s assume a temperature of 30°C and zero headwind. The airfield height from the altimeter is 1560 ft. What do you calculate to be the take-off distance required?”

The pilot worked uncertainly at the performance chart from the flight manual.

“Hell! I make it 3300 ft!”

“What about a 5 kt headwind component?” said John, biting into his sandwich.

“I still make it 3000 ft under those conditions,” replied the pilot shaking his head in disbelief.

“Even excluding the factoring incorporated into the charts you would not have been able to make a safe take-off,” John responded.

“Well,” John continued, “we’ll check the actual performance figures with our performance engineers and match them up with our ground marks. At this stage we are assuming no engine problems and a cross-check on performance will give us a guide as to whether we’ll have to do an engine run and strip inspection.

“However,” said John, pausing for another draught from the water container, “we seem to have found most of the answers to our what question and some of the why questions.”

“I always thought I’d be below max-all-up-weight with full fuel and four on board,” said the pilot before taking his turn at the offered water bottle, “. . . and I used a short field take-off technique!”

“It’s not our job to comment on a pilot’s technique- the Flight Standards boys are the experts in that field,” said John. “However, all of our investigators are very experienced pilots and we were able to comment generally. You’ve got about 200 hours flying under your tail now, and a commercial licence. The circumstances of the accident, however, suggest there is room for improvement in your professionalism. With all the time you had available while waiting for your passengers, you could have done your performance calculations and measured the strip. You should, in fact, have done that before you even flew in here to see if you could conduct a safe operation. Pre-flight preparation is the basis of professionalism in flying. Anyway-enough preaching-we “got to get your story in detail your own words as to what happened.” John wrote as the pilot recalled his flight from the outset.

Later, they dropped the pilot off at his hotel.

As John drove he was silent for a while as he mentally checked off the post-inspection requirements – aircraft was released to the owner’s representative telephone contact for the pilot.

“Say again!” said John, as Ray’s voice broke into his thought.

“I was saying,” replied Ray, “that, looking back to when I was young pilot of the same experience, I probably would have fallen into the same trap. I can’t recall being taught much about ALA operations – it was only when I went to New Guinea that I was forced to be ever-conscious of a strip length and performance.

“We’ll need to talk to a couple of his passengers-especially the one who reckoned he heard the tail scrape during take-off. Then we’ll get a hind-cast of the weather conditions at the time of the accident. The strip itself was within ALA standards-except for length no problems there. It was a simple job in this case for us to survey the strip but in some cases, we would ask for a full survey from the Airport’s Surveyors. No Air Traffic Control involvement to investigate. No additional human factors to consider -the pilot was well rested, had proper meals, no long period of duty or apparent fatigue. No misleading visual cues or illusions to consider, no personal worries.

“It amazes me sometimes,” John continued, “that a lot of people still think that when you investigate the human factors involved you’re trying to find excuses for the pilot! If the engine was suspected of being below par in performance they would expend a full performance check and strip examination to find the reason for it. The same principle applies in the investigation of the performance of the operator-pilot, controller, and engineer, whoever Eighty per cent of accidents are caused by human factors. We have got to find out what happened and then if a person’s substandard performance contributed, why this occurred.

“Anyway,” said John, realising he was preaching again, “when you do your training course they give you an insight into human factors-pity we didn’t run a similar course for pilots!”

Before changing drivers, John recapitulated on all the full aspects of the investigation with Ray.

The tyres crunched the gravel as they turned into the car park of Bentley’s pub in Clare for a comfort stop.

“Let’s have a Squash while we rest and you then can drive.

Their sweaty shirts chilled their backs as they sat in the back.

“When we get back to work on Tuesday, I’ll get you to draft the preliminary accident report and I’ll check it. I’ll also get you to complete the rest of the final report and then I’ll give you my draft analysis of the accident for comment. This is a report we should be able to complete quite quickly no waiting for any specialist reports – even if we have to do an engine test run it’ll only delay us a couple of weeks. This will be an ideal accident to feature in the Digest!”

John savoured the last iceblock as they hit the scorching air in the carpark.

The sun was low in the sky and he was mentally relieved that they were driving south not west!

For the first time today, John allowed the conversation to drift over to generalities and gave accident prevention a rest.

It was dark when they arrived in the city and Ray dropped himself off first.

“See you Tuesday,” said John, as he drove off. “Barring accidents,” he thought to himself

Editor’s Note: Readers of Eject, Eject, Eject which featured in our June issue would be interested to know that John Downing was the pilot of the referred to Canberra which was shot down over the north-westerly sector of South Vietnam on March 14th, 1971. John Downing is now an aircraft accident investigator with the Adelaide field office of the Bureau of Air Safety Investigation