Cessna 210N, VH-LDC

The Cessna 210 was involved in a geophysical survey task west of Emerald. The survey task included flying a number of pre-planned survey lines. A line number identified each line. The survey lines to be flown on the day of the accident were a block between lines 11118 and 11125. Line 11127, south of this block, was to be re-flown as previous data collected on the line was flawed. The lines were oriented 070/250 degrees M and were about 110 km (60 NM) long. From the southwest, the lines traversed flat, open terrain initially, and then crossed the Drummond Range. The range rises about 400 m above the level of the surrounding terrain and is a rugged area, which includes a number of narrow valleys.

The aircraft was equipped with a satellite navigation system, which provided information on the track to be flown to the pilot via a display on the glare-shield above the instrument panel. A radio altimeter provided aircraft height above ground level. Survey lines were to be flown at 140 kts indicated airspeed and, where possible, at 80 m above ground level. Accuracy in horizontal track keeping had priority over vertical navigation accuracy. For considerations of safety and ease of flying, the flying technique over rough terrain involved "smoothing" of the flight path rather than attempting to follow terrain contours.

The aircraft departed Clermont at 0638 EST. Because radio transmissions interfered with the recording of survey data, none were normally made during survey operations. Consequently, no contact was expected from the aircraft until about 1130, when it was due to return from the survey task. When no communication had been received by this time, the company reported that the aircraft was overdue and a search was commenced. Three days later, the burnt wreckage of the aircraft was located in the Drummond Range approximately 58 NM west of Emerald. The wreckage was about 30 m below the top of a ridge, which formed the southern side of the same valley followed by survey line 11124. It was approximately 400 m south of that line.

There were no witnesses to the accident.

In the absence of any witnesses or recorded flight data, the events leading to the accident could not be determined. However, the right turn the aircraft was apparently performing at impact could indicate that the pilot had been flying towards the northeast, into the valley (perhaps following survey line 11124) and was attempting to turn back down the valley. It is possible that the wind and turbulent conditions in the valley affected the climb performance of the aircraft sufficiently to create doubt in the pilot's mind that the aircraft possessed enough residual performance to outclimb the valley floor.

Cloud on the range may have affected visibility and limited or delayed the pilot's appreciation of the terrain ahead. Similarly, if the weather was clear, the elevation and azimuth of the sun relative to the aircraft's track may also have affected the pilot's perception of the terrain ahead. Either of these possibilities may have caused him to attempt to turn back.

The outcome of a turn in the valley would have depended on the aircraft's speed and altitude when the turn was initiated, its position in the valley (that is, the manoeuvring area available), and the pilot's skill level, as well as any turbulence and/or windshear which was present. A comparison of turn radii at various bank angles against the width of the valley indicates that the aircraft could have been in a position where there was insufficient room in which to safely complete a turnback.

The completion by the pilot of only the "Aircraft handling" section of the Aerial Stock Mustering Syllabus may have influenced his actions in the events leading to the accident. However, the limited information available concerning the final stages of the flight made any meaningful assessment in this regard impossible.

The factors contributing to this accident could not be conclusively determined.

Pilot-in-command

The pilot-in-command had a total flying experience of 1,445 hours, of which about 450 were on Cessna 210 aircraft on low level survey tasks.

Aircraft information

The aircraft was manufactured in the USA in 1982 and was entered on the Australian register in 1983. In 1994, it was fitted with approved specialist equipment for geophysical survey operations. The certificate of registration and maintenance release was valid at the time of the accident. The weight and centre of gravity (CG) were within limits.

Meteorological information

A Bureau of Meteorology post-analysis of the weather conditions in the survey area at the time of the accident, indicated that the surface wind was easterly at 5-10 knots. The wind at 2,000 feet was 070 degrees at 25 knots, causing a wind shear of approximately 20 knots between that level and the surface. There was likely to have been significant mechanical turbulence in the Drummond Range area. There was a broken layer of stratiform cloud with a base of 2,000 to 3,000 feet. Visibility beneath the cloud was good and there was no evidence of precipitation in the area. Similar conditions existed on the day following the accident when search aircraft reported severe mechanical turbulence at low level in the area.

Position of the sun

Sunrise at the accident location was 0637. Between 0700 and 0800, the elevation of the sun was between 4 and 16 degrees above the horizon. The azimuth of the sun during that time was between 061 and 068 degrees M.

Examination of the wreckage

Evidence at the accident site indicated that the aircraft had struck several trees while in an 85-90 degree angle-of-bank descending turn to the right. The aircraft heading at that time was about 240 degrees M. Fifteen metres after the initial tree contact, the right wingtip struck the ground. The aircraft then cartwheeled before coming to rest inverted. The wings separated from the fuselage as a single unit and continued beyond the main wreckage. The fuselage remained substantially intact during the impact sequence but was destroyed by the post-impact fire.

Examination of the airframe and powerplant did not reveal any abnormality that might have contributed to the accident. The nature and extent of damage to the propeller indicated that the engine was producing power at impact. The wing flaps were in the retracted position and there was no evidence that the aircraft had suffered a birdstrike. The extent of damage to the survey equipment on the aircraft precluded the recovery of any recorded data that might have assisted in determining the flight path of the aircraft.

Medical and pathological information

There was no evidence of any physiological condition concerning either crewmember that may have contributed to the accident.

Survival aspects

The severity of the impact and subsequent fire were such that the accident was not survivable.

Emergency locator transmitters

The aircraft carried two emergency locator transmitters. One of these was a fixed installation and the other was a portable unit that was normally located under the crewmember's seat. Both units were recovered. The nature and extent of damage sustained by each precluded normal operation.

Other information

Pilot training

At the time of the accident, there was no regulatory requirement which specifically addressed low level survey operations. However, the instrument of approval for low level survey operations issued to the company by the Civil Aviation Safety Authority (CASA) required pilots employed by the company to have either undergone a course in low level flying, or to hold or have held an agricultural rating or an aerial stock mustering approval. This was standard CASA procedure for such approvals.

Civil Aviation Order (CAO) 29.10 addressed low level flying for aerial stock mustering operations. Appendix 1 to the order detailed the syllabus of training. Paragraph 2 referred to aeroplanes and gyroplanes and stated:

Aircraft Handling:
1. level, climbing and descending turns up to 60 degrees angle of bank;
2. review of stalling symptoms and recovery in both wings level and turning flight up to 60 degrees angle of bank (Aeroplanes);
3. recovery from high rates of descent at speeds below minimum straight and level speed (Gyroplanes)
4. slow flying (including use of flap and the effect of changing flap settings);
5. methods of losing height;
6. manoeuvring at varying airspeeds and angles of bank.
7. Note: Before starting low flying training the student is to demonstrate safe aircraft handling of sub-paragraphs (i), (ii), and (iv) below 300 feet but not below 150 feet.
Low Flying:
1. low flying (below 100 feet above ground level);
2. slow flying (including use of flap);
3. effect of wind (apparent change in speed in head/tail winds and apparent slip and skid in cross winds);
4. action in the event of engine failure at low level;
5. method of losing height;
6. procedure turns, steep and climbing turns from a fixed ground reference combined with descending turns back to the reference. The obstructed viability inherent in manoeuvring high-wing aeroplanes in descending turns to be a fixed ground reference shall be demonstrated;
7. low flying in hilly terrain;
8. effect of false horizons;
9. effect of the sun, under certain conditions, on visibility;
10. approach to high ground - use of escape routes; and
11. avoidance of obstacles."

The pilot's records indicated that he had completed sub-paragraph (a) "Aircraft Handling" training in August 1995. This indicated that the pilot had completed the section of the syllabus relating to aircraft handling. There was no record of him having completed the sub-paragraph (b) "Low Flying" section of the syllabus.

Additional information and training provided by the company to pilots

The survey company issued to all its pilots, a publication titled "The Survey Pilots Guide". The guide outlined the techniques and procedures to be used when flying survey operations. Some of the topics covered included hazards such as the sun, terrain, and powerlines. Paragraph 3.1.4 of the Guide addressed "Terrain". Paragraph 3.1.4(b) was titled anticipation and stated:

"Due to the aircraft's speed and inertia it is vital to anticipate commencement of climb and descent when following terrain. Terrain over 1,500 feet above normal survey level needs further anticipation as the inertia dissipates above this height, the aircraft relies on climb performance alone. For example approaching a hill of 2,500 feet commence climb at five nautical miles before the base of the hill."

Paragraph 3.1.4(a) stated that "kinetic energy of the aircraft provides some assistance when flying over terrain up to 1,500 feet above ground level".

There was no information in the guide, nor was there training provided to pilots, on specific manoeuvres such as minimum radius turns which might need to be flown as an escape manoeuvre from a valley.

For any aircraft flying at an airspeed of 140 kts, the radius of turn for a constant altitude, steady turn, is as follows:

Angle of bank (degrees)	Turn radius (m/ft)
30	915/3000
45	518/1700
60	305/1000
80	94/310

The elevation of the wreckage was between 2,100 ft and 2,250 ft above mean sea level. The width of the valley at this elevation was between 500 and 850 m. The valley width at 2,000 ft elevation was 300 m, and reduced to about 200 m at 1,800 ft elevation.

The investigation identified a perceived safety deficiency. The safety deficiency related to the lack of provision of a low-level survey rating for pilots.

Low-level operations generally involve either agricultural operations, or survey operations. Agricultural operators undertake an agricultural rating, which provides training to operate at low level. A syllabus exists to provide approval for pilots to conduct mustering operations and the low-level training segment of this syllabus is normally required for low flying permission to be granted for other low level flying operations.

No low-level endorsement exists at present. However, as part of the Regulatory Framework Program, the Civil Aviation Safety Authority is developing Civil Aviation Safety Regulation part 137, which will address the training and qualification requirements of all pilots undertaking aerial work at low level. The Bureau will monitor progress of this issue.

Any safety output issued as a result of this analysis will be published in the Bureau's Quarterly Safety Deficiency Report.