The ATSB has released its final report on an incident involving a Cessna A188B/A1 Agtruck that collided with terrain shortly after take-off while conducting aerial spraying operations.
On September 14 2010 the pilot of a Cessna A188B/A1 Agtruck, registered VH-KZF, was conducting aerial spraying operations about 25km east of Geraldton Airport, Western Australia.
The pilot commenced the take-off from an elevated, 700m long gravel airstrip on the 11th of 12 flights, during which the aircraft did not achieve the required take-off performance. In an attempt to become airborne before the end of the useable runway surface, the pilot elected to dump some of the chemical load and continued the take-off.
The diminished aircraft performance was such that, despite the reduced chemical load, the aircraft did not accelerate to the required take-off speed before the runway overshoot area. The aircraft made contact with a tree stump that was embedded in thick weed and likely further reduced the aircraft’s ability to sustain flight.
The aircraft subsequently collided with terrain a short distance from the departure end of the airstrip. The pilot was fatally injured and the aircraft was seriously damaged by the impact forces and an intense post-impact fire.
History of the flight
At about 1000 Western Standard Time the pilot of VH-KZF departed Geraldton Airport for an airstrip about 25km to the east, which was to be the base for the pilot’s aerial spraying operations in the local area. The pilot was met at the airstrip by an assistant (loader) with a truck that contained the chemical, mixing equipment and refuelling supplies for the planned spraying activities.
Each flight that day required the aircraft’s spray tank (hopper) to be loaded with a combined 600 L of water and chemical that was pumped from the loader’s truck. At about 1100, the loader mixed the required chemical and commenced loading it into the aircraft’s hopper in preparation for the first flight. The quantity of chemical loaded was monitored by the pilot via a fluid quantity sight gauge that was visible from inside the cockpit.
After loading, the pilot commenced the initial take-off from the loading point in a south-easterly direction. Nine subsequent flights were successfully completed using the same runway and loading process. At about 1500 the aircraft was shut down for about 30 minutes to enable the pilot to refuel and for the loader to replenish the aircraft’s hopper. As the loader replenished the hopper with the chemical mix, the pilot refuelled the aircraft’s left wing fuel tank. The exact quantity of fuel uplifted could not be determined.
The refuelling was finished before the required hopper load volume was reached, and the loader stopped the chemical resupply to replace the fuel hose onto the load truck. That allowed the pilot time to enter the cockpit, start the aircraft’s engine, and to monitor the remaining chemical load.
It was reported by the loader that, as he could not see the fluid level in the hopper while it was being replenished, he relied solely on the pilot to tell him when the desired load volume was reached. The pilot was observed looking down in the cockpit before signalling to the loader to stop filling the hopper. The investigation could not determine the exact amount of chemical mix loaded into the hopper prior to the flight or if, during that time, the pilot was monitoring the load.
Shortly after the aircraft was replenished, the pilot commenced the take-off. Moments later, the loader heard a loud noise followed by an “almighty crack” and observed smoke to the right of the extended runway centreline. The loader used the load truck’s communications radio to alert anyone in the vicinity of the accident, and immediately drove to the departure end of the runway. He located the aircraft, which was on fire and inverted, in a treed area beyond and below the end of the airstrip.
The pilot was fatally injured and the aircraft was seriously damaged by impact forces and an intense post-impact fire.
Pilot
The pilot was issued a CPL in 1992 and was appropriately endorsed for the operation. He had a total of around 10,750 flying hours, including 8840 hours on agricultural-type aircraft. He held a Grade 1 Aeroplane Agricultural Rating and had operational approval to act as Chief Pilot for a Geraldton-based aerial agriculture company. An Aerial Agricultural Association of Australia (AAAA) Spray Safe Pilot Accreditation was issued to the pilot in January 1995 and he held a valid Class 1 Aviation Medical Certificate with nil restrictions.
It was estimated that the pilot accrued about 60 hours of duty time and conducted about 44 hours of aerial spraying in larger, turbine-powered agricultural aircraft in the 14 days prior to the accident. Additional, unrecorded flying was also reported to have been conducted by the pilot in VH-KZF during that time.
Loader
About three weeks prior to the accident, the loader undertook one day of initial loader training, where he was shown by the operator how to use the company’s chemical loading equipment. During that training, the loader completed eight aircraft replenishments under supervision. The following day, the loader successfully completed a further six replenishments for the accident pilot in VH-KZF. The loading throughout the day was the third time that the loader had performed loading duties in support of an actual aerial spraying operation.
Aircraft information
The aircraft was a single piston-engine, propeller-driven, low-wing aircraft that had seating for one pilot and was primarily used for aerial spraying activities. It was manufactured in the US in 1978 and according to maintenance records the total aircraft time in service was about 5200 hours.
An overhauled Teledyne Continental Motors IO-520D engine was installed in the aircraft in May 2010, coincident with the conduct of a 100-hourly inspection. Since that time, the aircraft had been operated for about 50 hours. It was reported that, about 45 hours after the 100-hourly inspection, the aircraft’s engine underwent an oil and oil filter change, which was not recorded in the aircraft’s maintenance documents.
The loader reported that the aircraft was refuelled from drums that were previously used to store aviation oil. The drums themselves had been refuelled on the morning of the accident from a Geraldton fuel facility. The pilot was reported to have refuelled the aircraft’s left wing tank from those drums three times prior to the accident. Fuel sample tests of the drum stock fuel after the accident indicated higher-than-normal gum levels.
The aircraft was fitted with a Robertson short take-off and landing (STOL) kit that incorporated a modification to the wing flap and aileron systems. The flaps were manually operated and, when they were extended from the 0° position, both ailerons were also mechanically displaced downwards (commonly called ‘droop’) to increase the effective flap area. That increased the effective camber of the wings and overall lift generated by the wings at a given speed, thus reducing the aircraft’s take-off distance.
The investigation could not determine if the supplemental take-off and landing information (flight manual supplement) relating to the STOL kit was included in the aircraft’s flight manual. If included, that supplement would have provided pilots with amended take-off performance planning data and configuration information applicable to VH-KZF. The STOL flight manual supplement recommended the 20° flap setting for take-off, but it was reported that the pilot did not always use that setting in VH-KZF.
Aircraft performance
The expected distance to lift off was estimated using information provided by the aircraft manufacturer and derived from the STOL manufacturer’s supplementary take-off and performance charts. That estimation showed that, with an MTOW of 1905kg, a zero headwind component and a flap setting of 0°, adequate runway existed for take-off within the available runway length.
It was reported by other pilots, and described in the AAAA’s Aerial Application Pilots Manual, that Ag pilots were trained to recognise and address a number of other factors that affect aircraft performance that may result in the need to dump a chemical or other load. Those factors included: poor judgement, miscalculation, unexpected meteorological variations or a combination of these and other factors. Pilots were cautioned in the AAAA’s manual that if any doubt existed as to an aircraft’s performance then the pilot should, without hesitation, dump the entire agricultural load to allow the aircraft time to accelerate within the remaining runway.
Meteorological information
The airstrip did not have, and nor was it required by regulation to have, a weather-reporting facility or a windsock to assist pilots in determining the wind direction and strength. The nearest aerodrome with recorded observed weather data was at Geraldton. The Geraldton 1400 METAR indicated a wind from 130° true (T) at 11 kts and a temperature of 23°C. The Geraldton 1530 METAR was issued at about the time of the accident and indicated CAVOK conditions, that the wind was from 170° T at 16 kts and that the temperature was 21°C.
Airstrip information
The 700m gravel airstrip was aligned in a south-east to north-west direction of 130/310° magnetic (M) along a plateau. The departure end of Runway 13 was elevated about 20m above the accident site. Pilots who had previously operated from the airstrip reported that rocky areas protruded through the surface, making the runway rougher than normal. That resulted in increased vibration through the aircraft during the take-off roll. The loader reported that prior to the accident, the pilot commenced the take-offs from the loading point and that the aircraft used about two thirds of the available runway before becoming airborne. Runway 13 was reported used for all take-offs and landings that day.
During the investigation a 15m long area of dried, white crystalline deposit was observed about 90m before the end of the runway. That deposit was consistent with the dried chemical being used on the day. The spread of the chemical deposit was indicative of the pilot activating and then stopping a chemical dump from the aircraft’s hopper. More of the dried chemical was identified around the accident site, indicating that the entire hopper was not dumped on the runway.
Wreckage and impact information
The wreckage was located about 100m from the end of the runway in a treed area that was about 20m below the airstrip and 25° to the right of the extended runway centreline. Ground scars made by the aircraft during the impact sequence indicated that the leading edge of the aircraft’s right wingtip impacted the ground first. Compression damage to that wing and the inverted aircraft wreckage indicated that the aircraft collided with the ground in an estimated 90° right wing-low, nose-down attitude. The confined wreckage distribution indicated a relatively low horizontal velocity at that time.
An intense post-impact fire consumed the fuselage and the inboard sections of the left and right wings. The tailplane, which included the vertical and horizontal stabilisers, sustained minimal damage. The flight control systems were determined to have been capable of normal operation pre-impact. The flap lever was engaged in the 20° flap position. Both flap surfaces were also at a flap setting of 20°. The position of the elevator trim tab was close to full aircraft nose-down deflection. Given the design of the trim system, and the relatively undisrupted rear fuselage, that trim tab position was likely consistent with its setting at impact.
It was reported by a pilot with experience in VH-KZF that the nose-down trim position that was used for landing was also used as a reference setting prior to commencing a take-off. If required, the aircraft’s trim could be adjusted during the take-off roll. It was also considered by that pilot that adequate control authority would exist during take-off in the event that the trim was inadvertently positioned in a full nose-down position.
On-site examination of the propeller indicated that the engine was producing a degree of power and that it was rotating at the time of impact. The amount of power could not be determined. A number of aircraft components, including the engine, propeller, and brake discs were recovered from the accident site for later technical examination. Those examinations found no evidence of any mechanical malfunction that might have contributed to the development of the accident.
Additional information – Spraying operations
It was reported to be common for pilots to use their past agricultural spraying experience and knowledge of an aircraft’s performance when determining the load limit for a particular take-off. Pilots stated that to establish the maximum load that could be uplifted from an airstrip, they would often commence operations using a fuel and chemical load that they knew would allow for a successful take-off. If, after the first take-off, the full length of the runway was found to not be required, there was the option to increase an aircraft’s load on the next flight. That ensured the use of the maximum available runway and time spent in the air spraying.
It was reported that, prior to pilots exiting an Agtruck aircraft, it was common practice to retract the aircraft’s flaps and apply the park brake. Retracting the flaps allowed easy access to the cockpit via the wing, and the application of the park brake ensured that the tail of the aircraft did not move and collide with the load vehicle, which was parked nearby during reloading/refuelling.
Additional information – Life event stress
The pilot was reported to be a very busy person who had various stressors in his life. Those included new career aspirations and personal and life stressors. ‘Life event stress’ can be defined as stress resulting from significant life events such as divorce, financial worries and the like which can reduce general wellbeing and increase the susceptibility to some illnesses.
ANALYSIS
Aerial spraying operations are, by their nature, often conducted from remote locations that provide for limited forecast weather information, airstrip data and obstacle information. As a result, agricultural pilots need to remain vigilant both during the spray application and while preparing the aircraft for the next flight. Regular monitoring and assessment of the factors that influence operations will determine the success of a flight. Failure to do so can increase the risk of error in an environment that already has reduced error margins.
There was no direct evidence as to why the pilot was unable to achieve the same take-off performance that was achieved on the previous flights that day. This analysis will explore some of the factors that existed on the day of the accident and any effect they may have had on the flight.
Aircraft configuration and airstrip characteristics
Examination of the aircraft identified that the aircraft flap lever was captured in the 20° flap-down position at impact. However, the pilot might have adjusted the position of the flaps throughout the take-off sequence and it was not possible to establish when the flap was selected during that sequence.
The take-off performance had been sufficient for the previous 10 take-offs and was estimated to have been more than adequate for the weight of the aircraft, the runway characteristics, and the reported weather conditions. On that basis, the investigation concluded that, if the aircraft had performed normally and was handled appropriately, the pilot should have been able to avoid the tree stump and other obstacles.
Aircraft weight
It was probable that the pilot intended to take off with a combined water/chemical load of 600L, as was the case for the remainder of the day. The action by the pilot to signal the loader to recommence loading suggested that the pilot had identified the amount of water/chemical in the aircraft’s hopper, and that the target load of 600L had not yet been reached.
The pilot’s mobile phone records suggested that the pilot may have been making phone calls at about the time that the loading was taking place. Had that been the case, the associated distraction could have adversely affected the pilot’s monitoring of the replenishment and resulted in the hopper being inadvertently filled to more than 600 L. Any additional load would have decreased the aircraft’s take-off performance and increased the runway required.
The action by the pilot to dump some of the water/chemical load in the last 90m of the runway indicated that the pilot was aware of the diminished take-off performance. Had the pilot dumped the entire load at that time, the resulting additional take-off performance may have enabled the aircraft to clear the obstacles at the end of the runway.
Engine power loss
Due to the extensive impact and fire damage, it was not possible to determine if the engine was capable of developing the power required for a successful take-off. However, the damage to the propeller, which was probably in part due to contact with the tree stump, and lack of any evidence of a mechanical engine malfunction, indicated that at least a degree of engine power was available at that time. Any damage to the propeller would have decreased its propulsive efficiency relative to the engine power being developed, further reducing the aircraft’s take-off performance and ability to climb away.
Fuel storage
It could not be determined why the fuel samples from the load truck’s fuel hose returned higher-than-recommended gum levels. The use by the pilot of fuel that had been stored in disused aviation oil drums increased the risk that the fuel would not be suitable for the intended application.
Distraction
While the effect of mobile phone use in this instance could not be determined, research has indicated that phone usage does affect attention, especially during routine tasks such as driving. Therefore, it could be expected that the use of mobile phones by pilots during aerial application would similarly impact on those operations and should be discouraged.
In this instance, any distraction could have: impacted on the pilot’s ability to monitor the chemical load; have affected or interrupted his preparation for the take-off, including flaps selection and the release of the handbrake; and have impacted on his monitoring and consideration of the effect of the changing weather conditions. The life stresses affecting the pilot at the time increased the distraction risk.
Conclusion
The investigation did not identify any organisational or systemic issues that might adversely affect the future safety of aviation operations. However, the accident does provide a timely reminder of the need for performance planning and the continual assessment of the effect of changing conditions on that planning.
Contributing safety factors
- There was insufficient aircraft performance to successfully take off within the available runway distance.
- The aircraft contacted a number of obstacles beyond the useable runway surface, which diminished the available take-off performance and the ability to sustain flight.
Other safety factors
- The aircraft was refuelled from drums that were not recommended for the storage of aviation grade fuel.
- The pilot was not wearing a helmet.