ATSB

Grounding of the Tassos N

Final report

Summary

At 0500 on 10 January 1997, the 39,630 tonne Cypriot flag bulk carrier Tassos N departed the Alcoa wharf at Kwinana W.A., bound for Ferndale in the USA with a cargo of 37,775 tonnes of alumina. The weather was fine and calm and the visibility good. With a Fremantle Pilot on board, the ship safely negotiated the Calista Channel and then the Stirling Channel.

As it entered the Parmelia channel, however, a steering gear fault occurred which resulted in the ship not responding properly to the movements of the helm. The ship's head swung either side of the intended track. As the Pilot attempted to arrest the swing, the bows swung sharply to starboard. The Master switched from No.1 to No.2 steering systems but then, seeing no response from No.2, he immediately switched back to No.1. In spite of the Pilot's helm and engine orders, and dropping the port anchor, the ship grounded in the channel on a heading of 032 with 'L' beacon abeam and only 30 metres from the bridge.

The vessel had grounded only forward and was refloated later that day with the aid of tugs and a change of trim through ballasting by the stern. Damage was confined to the paintwork on the ship's bottom.

The incident was investigated by the Marine Incident Investigation Unit under the provisions of the Navigation (Marine Casualty) Regulations.

Conclusions

These conclusions identify the different factors which contributed to the circumstances and causes of the incident and should not be read as apportioning blame or liability to any particular organisation or individual.

Tassos N grounded as a direct result of the failure of the steering gear.
The steering gear failed following the perishing and breaking-up of the rubber dust seal within an actuating solenoid on the servo-control hydraulic power unit. As a consequence of this failure, small pieces of rubber jammed the movement of the solenoid causing the failure of No.1 steering system.
It is specifically mentioned in the manufacturer's manual, relating to the servo-control hydraulic power unit, that regular inspection or maintenance of the power unit, of which the solenoid was a component, is not necessary.
On account of the short time available following the steering gear failure, neither the Master nor the Pilot could have taken action, beyond the measures which were taken, to avoid the grounding.
Although the Master changed over steering systems to the No.2 (stand-by) system at the steering console and then changed back to the faulty system, the time available was such that the grounding was inevitable, even had he realised that No.2 system was operational.
The Master and other members of the ship's complement were showing signs of fatigue both before and after the grounding. It is not considered, however, that fatigue was a contributing factor in this incident.

Occurrence summary

Investigation number	107
Occurrence date	10/01/1997
Location	Kwinana
State	Western Australia
Report release date	20/02/1998
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Marine
Marine occurrence category	Grounding
Occurrence class	Incident
Highest injury level	None

Ship details

Name	Tassos N
IMO number	709928
Ship type	Bulk carrier
Flag	Cyprus
Departure point	Kwinana
Destination	Ferndale USA

British Aerospace Plc BAe 146-300, VH-NJL

Summary

The aircraft was observed to become airborne from runway 33 and then to lose altitude with the landing gear extended. The descent was continued, causing concern to the tower controller who activated the crash alarm. After the crew were asked and had confirmed that operations were normal the aircraft landing gear was retracted, and it began to climb.

The investigation found that the flaps had been retracted at the time when the landing gear is normally retracted. Neither pilot had any recollection of making the selection, nor were they aware that the flaps were retracting, until after the stall warning activated during the climb after take-off.

Occurrence summary

Investigation number	199704041
Occurrence date	11/12/1997
Location	1 km NNW Cairns, Aero.
State	Queensland
Report release date	15/08/1999
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Aviation occurrence category	Incorrect configuration
Occurrence class	Incident
Highest injury level	None

Aircraft details

Manufacturer	British Aerospace
Model	BAe 146
Registration	VH-NJL
Serial number	E3213
Sector	Jet
Operation type	Air Transport High Capacity
Departure point	Cairns, QLD
Destination	Ayers Rock, NT
Damage	Nil

Hughes Helicopters, 269C, VH-UOS, 7.5 km south-west of Orroroo, South Australia

Summary

The helicopter operator was hired by a government organisation to assist with locust plague control. The helicopter pilot was required to fly at low level to assess locust numbers in areas identified by ground personnel. When the pilot or his observer reported adequate densities of locusts, the area locust plague controller would dispatch a fixed wing agricultural aircraft to spray the locusts with insecticide.

The accident occurred on the pilot's second day on task. Flying commenced at about 1000. The pilot ferried his helicopter from Quorn to Orroroo, a distance of 42 km, and landed. Then he flew a solo reconnaissance flight for approximately 35 minutes, before returning to Orroroo airstrip. There, an observer boarded for a flight expected to last about 10 minutes. When the helicopter had not returned to the airstrip after about 20 minutes and there was no radio contact, the pilot of an agricultural aeroplane commenced an airborne search. He soon found the helicopter, crashed and on fire in an oat crop.

Evidence at the crash site showed that the helicopter had been tracking approximately south when it collided at about 90 degrees with a single power line, 27 ft above the ground. The wire snagged on the forward crossbeam of the skid landing gear. The wire stretched but did not break as it pulled the helicopter to the ground in a nose low attitude. At impact the main rotors struck the ground, and the instrument console shattered the forward portion of the Perspex windshield. The still unbroken powerline then flipped the helicopter backwards along its flight path where it impacted the ground inverted. During the impact sequence the muffler was dislodged and the fuel system ruptured. A nearby farmer reported that she heard the helicopter's engine continue to run for a short time after the unexpected loss of her household electrical power. Aviation gasoline (AVGAS) was ignited, and the aircraft was consumed by fire. The three strand, high tensile, steel wire comprising the powerline did not break until it was weakened by the intense heat of the post impact fire.

The pilot was suitably qualified to conduct the flight. He was not considered to have been suffering from fatigue, nor was he subsequently found to have been suffering any medical problem which may have contributed to the accident.

No fault was subsequently found with the helicopter airframe or engine which may have contributed to the accident.

Personnel who arrived at the crash site within minutes of the accident reported that the weather was fine. Visibility was excellent, the wind was almost calm, the sun was high overhead, and there was no cloud. The absence of splattered locusts on recovered unburnt pieces of the Perspex windshield/canopy found near the first point of ground impact, indicated that the pilot's forward visibility was probably not significantly obstructed by the windshield immediately prior to the accident.

The power line struck by the aircraft was an east/west spur line spanning 400 m between poles. The nearest pole to the crash site was 186 m to the west. This pole was also supporting a prominent powerline parallelling a gravel road heading south-west. In contrast, the pole at the eastern end of the spurline was near a farmhouse and outbuildings, 214 m east of the accident site. The farmhouse was close to another gravel road heading south but there was no powerline associated with this road.

On the morning after the accident, investigators noticed many locusts within the oat crop and on the ground but few in the air. Later in the day the locusts became airborne, and the enormity of their numbers became obvious. To locate and assess the density of locusts the task often required the helicopter pilot to fly low. There may appear to be few if any locusts in a suspected plague area because they could be within the pasture or crop, or on the ground. When the helicopter collided with the powerline, the pilot was probably in the process of descending low over the crop, expecting the rotor downwash to disturb the locusts enough to prompt them to take flight.

The helicopter was not equipped with any form of wire strike protection system (WSPS) or warning device to detect a powerline. A WSPS was not a requirement in the contract. No known WSPS exists for the Hughes 300. In this occurrence, a WSPS fitted helicopter would probably have cut the wire and survived with little damage to the airframe and no injury to personnel. In previous years, helicopters contracted for the same work had been fitted with WSPS.

A WSPS does not eliminate the possibility of an accident or injury as a result of a wire strike by a helicopter, but it reduces the risk. The safety value of the WSPS has been recognised more in recent years; WSPS is now routinely fitted to military, firefighting, search and rescue, police and ambulance helicopters.

Electronic powerline detection devices are being developed for aircraft. They may enhance safety for future low level operations by providing pilots with warning of a powerline ahead of the aircraft. Some successful trials have already been conducted in Australia.

The pilot would probably have had difficulty detecting the powerline due to the long span of the single wire. It is possible that he either did not see the wire at all, or he may have seen it too late to successfully achieve avoiding action.

Occurrence summary

Investigation number	199703877
Occurrence date	27/11/1997
Location	7.5 km south-west of Orroroo
State	South Australia
Report release date	22/04/1998
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Aviation occurrence category	Wirestrike
Occurrence class	Accident
Highest injury level	Fatal

Aircraft details

Manufacturer	Hughes Helicopters
Model	269C
Registration	VH-UOS
Serial number	500927
Sector	Helicopter
Operation type	Aerial Work
Departure point	Orroroo, SA
Destination	Orroroo, SA
Damage	Destroyed

de Havilland Canada DHC-8-102, VH-TQN

Safety Action

The Bureau of Air Safety Investigation is investigating a number of safety deficiencies relating to aircraft operations in non-controlled airspace with a view to reducing the reliance on the unalerted "see-and-avoid" principle as the primary means of separation for fare-paying passenger flights.

For example, the Bureau issued Interim Recommendation (IR) 970155 to the Civil Aviation Safety Authority on 30 January 1998, which resulted from the analysis of a similar occurrence.

The interim recommendation stated in part:

"The greater use of larger and faster aircraft for RPT flights in non-controlled airspace increases the need for the adoption and use of "separation assurance" techniques in conjunction with "alerted see-and-avoid" procedures by all flight crews.

"Although the inclusion of "separation assurance" techniques in airline flight operations manuals would address the deficiency to some extent, procedures for other IFR and the majority of visual flight rules (VFR) flights are also essential. Many pilots may require guidance and training on "separation assurance" techniques.

"Alerted see-and-avoid" procedures used in conjunction with "separation assurance" techniques provide a fail-safe method of self-separation which enhances safety.

"The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority in conjunction with Airservices Australia:

"Review aviation regulations and instructions, with the aim of maximising the use of "separation assurance" procedures in conjunction with "alerted see-and-avoid" procedures by pilots of flights in Class G airspace.

'The Bureau of Air Safety Investigation further recommends that the Civil Aviation Safety Authority:

"Implement an education program for pilots to promote the use of "separation assurance" procedures in Class G airspace".

The first part of the recommendation was sent to Airservices Australia as IR970175.

Significant Factors

The crew of the Dash 8 did not hear the departure report by the pilot of the Chieftain or if they did, they did not appreciate that there was a potential for conflict.
The crew of the Dash 8 did not include their position when they requested traffic information from flight service prior to leaving FL180.
The pilot of the Chieftain did not hear the descent report from the Dash 8 crew.
The track of the Chieftain in relation to the early morning sun limited the pilot's ability to scan for other traffic.
A reflection off the Chieftain alerted the Dash 8 crew to the presence of the aircraft.

Analysis

Reports

The reason why the crew of the Dash 8 did not hear the Wee Waa departure report by the pilot of the Chieftain, or if they did, why they did not appreciate that there was the potential for conflict, was not determined.

The crew of the Dash 8 had previously reported their position and estimate for Narrabri on first contact with flight service. The reason the crew subsequently did not comply with AIP and company operating procedures, regarding a position report prior to descent, was also not determined.

The monitoring of the Tamworth ATIS transmission by the pilot of the Chieftain may have prevented him from hearing the Dash 8 crew report on descent. Consequently, he was unalerted to the Dash 8. If he had heard the transmission he may have initiated communication to ascertain if there was the potential for conflict. Under the current VFR procedures there was no third party, such as flight service, to alert the pilot to the position of conflicting traffic.

Environmental aspects

The Chieftain pilot reported that he was using the visor in the cabin but that he did not believe that his view from the aircraft was impaired. However, the fact that he was using the visor would indicate that the rising sun was of some concern and this aspect, in conjunction with the hazy conditions, probably limited his ability to sight potentially conflicting aircraft in his forward field of vision.

Unalerted "see-and-avoid" principle

Despite the Chieftain pilot's departure report, which was additional to that required for VFR flights, the crew of the Dash 8 remained unalerted to the pending conflict. This may have been due to the difficulty of assessing the potential conflict of other traffic from the limited details included in departure reports. In the dynamic aircraft operational environment, even with multiple flight crew, it is not an easy task to develop a situational awareness of all potential conflicting aircraft.

The provision of a position report by the crew of the Dash 8 prior to commencing descent would have been the main opportunity for the pilot of the Chieftain to be alerted to the potential conflict. However, the report did not contain a reference to the position of the Dash 8 and the Chieftain pilot was unaware of the location of the Dash 8. Additionally, it was possible that the pilot of the Chieftain may not have heard or appreciated the significance of the Dash 8 pre-descent position report even if it had been provided, as he was probably monitoring the Tamworth ATIS at the time. Consequently, in either situation, separation was solely reliant on the pilots' ability to sight other aircraft and to manoeuvre their aircraft in sufficient time to avoid a conflict.

The limited radio reports required from pilots operating VFR flights place an over-reliance on the unalerted "see-and-avoid" principle to maintain separation from other aircraft. This aspect was one of the conclusions in the Bureau's research report titled "Limitations of the See-and-Avoid Principle" (1991) which stated, "Unalerted see-and-avoid has a limited place as a last resort means of traffic separation at low closing speeds but is not sufficiently reliable to warrant a greater role in the air traffic system. BASI considers that see-and-avoid is completely unsuitable as a primary traffic separation method for scheduled services". In that research report BASI recommended that "the CAA should take into account the limitations of see-and-avoid when planning and managing airspace and should ensure that unalerted see-and-avoid is never the sole means of separation for aircraft providing scheduled services".

Summary

A DeHavilland Dash 8 was conducting an instrument flight rules (IFR) Air Transport flight from Sydney to Narrabri and tracked via Richmond direct to Narrabri at flight level (FL) 180. The flight was conducted in controlled airspace until approximately 130 NM north-north-west of Sydney. The remainder of the flight was then conducted in Class G non-controlled airspace. The crew of the Dash 8 contacted Sydney Flight Service (FS3) at 0721 Eastern Summer Time (ESuT) and reported that the aircraft was maintaining FL180 with an estimate for Narrabri of 0745. (All times are ESuT unless otherwise stated.)

At 0732 the pilot of a Piper Chieftain conducting a visual flight rules (VFR) flight from Wee Waa to Tamworth made an all-stations broadcast on the FS3 frequency. The pilot reported departing from Wee Waa at 0730, tracking 113 (degrees M) and climbing to 7,500 ft. The pilot addressed the report to FS3 and to any other traffic in the Wee Waa area. There was no acknowledgement or response to this report by other aircraft or ground stations. The pilot was rated and licensed for IFR flight but elected to operate VFR for this flight and therefore FS3 was not required to take any action in response to his broadcast.

Approximately 4 minutes after the Chieftain pilot's departure report, the crew of the Dash 8 requested traffic information from FS3 for their descent into Narrabri. FS3 advised that there was no known IFR traffic. The crew acknowledged this advice and reported that the Dash 8 had left FL180, but they did not include their position relative to Narrabri in the transmission.

The track of the Chieftain crossed the track of the Dash 8 approximately 12 NM south-southeast of Narrabri.

As the Dash 8 was passing 8,000 ft, the crew saw a reflection to the left of the nose of their aircraft. Subsequently, they saw a twin-engine aircraft and manoeuvred their aircraft to avoid it. The twin-engine aircraft passed from left to right approximately 300 m in front of them and at about the same level.

The crew of the Dash 8 queried FS3 regarding the other aircraft but were advised that there was no IFR traffic. The crew of the Dash 8 then made an all-stations area broadcast in an attempt to establish communications with the other pilot. The pilot of the Chieftain acknowledged the call and advised the crew that he was tracking from Wee Waa to Tamworth at 7,500 ft and that his aircraft was a Chieftain.

Further discussion established that the pilot had neither seen the Dash 8 nor heard the crew reporting on descent. The crew of the Dash 8 did not remember hearing the departure report from the pilot of the Chieftain.

Traffic information

In non-controlled airspace, flight service are required to provide information to all IFR-category aircraft on other IFR flights to assist crews in determining any conflict situations. However, the flight service information system does not cover VFR traffic. Therefore, in this instance FS3 was not required to provide information on VFR flights to the crew of the Dash 8.

Aircrew are responsible for maintaining their own separation in non-controlled airspace. IFR pilots use known position reports of other aircraft to gain an appreciation of the disposition of traffic and whether there is a need to arrange separation. Pilots of VFR flights are only required to make a limited number of position reports and generally rely on the unalerted "see and avoid" principle to maintain separation from other aircraft; that is, they maintain a continuous lookout for other aircraft.

Radio frequency monitoring

The Chieftain was fitted with two very high frequency (VHF) radios. The pilot selected one to the common traffic advisory frequency (CTAF) and one to the FS3 area frequency while in the Wee Waa CTAF area. After leaving that CTAF area, he changed from the CTAF to the Tamworth automatic terminal information service (ATIS) frequency on one radio while continuing to monitor FS3 on the second radio.

The investigation estimated from aircraft performance data that the Chieftain would have reached the planned level of 7,500 ft just prior to the Dash 8 crew requesting traffic information from flight service. The Chieftain pilot reported that at about that time he was probably listening to the Tamworth ATIS in preparation for requesting a clearance to enter controlled airspace from air traffic control.

The Dash 8 was also fitted with two VHF radios. While operating in controlled airspace, the crew selected the air traffic control frequency on one radio while the other was selected to the aviation emergency frequency. Prior to leaving controlled airspace, the crew selected the FS3 area frequency while continuing to monitor the emergency frequency on the second radio.

Reports

The Wee Waa departure report from the pilot of the Chieftain was recorded on the flight service automatic voice recording (AVR) system and was clear and understandable. This departure report was additional to the mandatory reports for VFR flights detailed in the Aeronautical Information Publication (AIP) RAC 64.

AIP RAC 42 paragraph 32.2 required the crew of an IFR aircraft to report their aircraft's position to flight service prior to changing levels. Company operating procedures for the Dash 8 required the crew to make a position report prior to descent when operating in non-controlled airspace. The AVR did not record a position report from the crew of the Dash 8 prior to their commencement of the descent.

Environmental aspects

The visibility was reported as hazy but in excess of 10 km. The sun was low in the sky and the pilot of the Chieftain had lowered the sun-visor in the aircraft cabin to shield his eyes.

Occurrence summary

Investigation number	199703850
Occurrence date	24/11/1997
Location	25 km SSE Narrabri, Aero.
State	New South Wales
Report release date	01/11/1998
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Aviation occurrence category	Near collision
Occurrence class	Incident
Highest injury level	None

Aircraft details

Manufacturer	De Havilland Canada/De Havilland Aircraft of Canada
Model	DHC-8
Registration	VH-TQN
Serial number	062
Sector	Turboprop
Operation type	Air Transport Low Capacity
Departure point	Sydney, NSW
Destination	Narrabri, NSW
Damage	Nil

Aircraft details

Manufacturer	Piper Aircraft Corp
Model	PA-31
Registration	VH-LTU
Serial number	31-7405462
Sector	Piston
Operation type	Private
Departure point	Wee Waa, NSW
Destination	Tamworth, NSW
Damage	Nil

de Havilland Canada DHC-6 SERIES 320, VH-HPY

Summary

The crew were operating a de Havilland Canada DHC-6 Twin Otter aircraft in Exercise Highland Pursuit 2/97. The purpose of the exercise, which was conducted by No. 173 Surveillance Squadron, 1st Aviation Regiment, Australian Army, was to provide tropical mountainous flying training in Papua New Guinea. There were three trainees and one training pilot on board the aircraft.

On Sunday, 9 November 1997, the third day of flying operations in Papua New Guinea, the crew were conducting a flight from Madang and return via a number of airstrips in the central highlands. When haze and cloud prevented them flying the flight-planned direct track between the Koinambe and Simbai airstrips, they decided to fly north-west via the Jimi River valley and one of its tributaries. Two of the trainees were occupying the cockpit seats, one as flying pilot and the other as navigating pilot using a 1:1,000,000-scale chart. When the crew turned the aircraft to follow a tributary off the Jimi River, the training pilot was in the aircraft cabin.

A few minutes later, their discussion regarding the progress of the flight attracted the attention of the training pilot. By this time, however, the position of the aircraft in the valley, and its available performance, were such that an escape from the valley was not possible. The aircraft collided with trees before impacting steeply sloping ground.

It was subsequently established that when the crew turned from the Jimi River, they entered the wrong valley. Calculations based on the manufacturer's performance data showed that the aircraft did not have sufficient performance to outclimb the increase in terrain elevation from the Jimi River valley to cross the Bismarck Ranges via this valley. There was a low level of experience and corporate knowledge within the Army regarding the operations of fixed-wing aircraft such as the Twin Otter in tropical mountainous areas.

Against this background, deficiencies were identified in the planning and preparation for the exercise, including risk assessment and the selection and briefing of the training pilot.

Occurrence summary

Investigation number	199703719
Occurrence date	09/11/1997
Location	9 km SW of Simbai in the Bismarck Ranges - Papua New Guinea
State	International
Report release date	25/07/1999
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Aviation occurrence category	Collision with terrain
Occurrence class	Accident
Highest injury level	Serious

Aircraft details

Manufacturer	De Havilland Canada/De Havilland Aircraft of Canada
Model	DHC-6
Registration	VH-HPY
Serial number	706
Sector	Turboprop
Operation type	Military
Departure point	Madang
Destination	Simbai
Damage	Nil

Boeing 747-438, VH-OJB

Analysis

In this occurrence, the crew of the aircraft was aware at the time of flight planning that a change in the direction and strength of the wind was expected before their arrival at Sydney. However, this change did not present problems for the crew at the flight planning stage, as the forecast conditions were still acceptable for a landing on runway 34L. During the flight, the changes in the wind direction and strength were still acceptable for the aircraft to use runway 34L until the change in wind velocity which was notified at 0426.

Until that time, the forecasts previously available to the crew contained errors of up to 70 degrees in wind direction. The only forecast which indicated a possibility that the wind would be southerly was the Sydney Airport Weather Briefing supplied to the operator on 14 October 1997.

The investigation was unable to determine why the crew did not act upon the change in wind information, or upon the implications of the resulting excessive downwind component for landing on runway 34L, before passing the DPA. By that stage little time remained in which to initiate a diversion to a suitable alternate airport. The crew did not request a diversion to Brisbane, and this, coupled with the ATC's delay in handling the aircraft after the DPA, eroded the time remaining in which a diversion was feasible.

At all times during the occurrence the aircraft had sufficient fuel to complete the flight to Sydney, and the aircraft landed with more than the minimum fuel reserves in accordance with company policy.

Summary

The aircraft, operating a scheduled passenger flight from Singapore to Sydney, landed at Sydney on runway 16R at 0525 Eastern Standard Time (EST) during curfew hours (All times are EST unless otherwise stated).

The Bureau of Meteorology (BOM) issued a terminal area forecast (TAF) for Sydney Airport at 2051 on 14 October 1997 for a 24-hour period commencing at 2200. The forecast indicated that the weather at Sydney would be suitable for an approach and landing, with the wind from 290 degrees at 8 kts. The forecast also indicated that from 0400 the wind would change direction to 240 degrees and that the strength would increase to 15 kts with gusts to 25 kts.

The Sydney Airport Weather Briefing issued to the operator by the BOM at 1745 on 14 October 1997 covered the TAF period from 1600 for 24 hours and indicated that there was a 20% chance that the change in the wind would be to a southerly direction.

The crew was aware of the TAF information at the pre-flight briefing at Singapore. As the available forecasts indicated that conditions would be acceptable for the aircraft to make an arrival at Sydney using runway 34L, there was no requirement to carry additional fuel other than company required variable and fixed fuel reserves. This was in accordance with normal company operating procedures and fuel planning policy.

The flight departed Singapore at 2217 (2017 local time) and the flight plan indicated that the aircraft would arrive in Sydney at 0456. During the flight, the crew monitored the hourly meteorological information broadcasts (VOLMET) and received routine meteorological (METAR) reports, which were based on Trend Type Forecasts (TTF), through the Aircraft Communication Addressing and Reporting System (ACARS) to keep themselves appraised of current and projected weather conditions at Sydney.

Trend Type Forecasts consist of aerodrome weather reports which contain a statement of trend. They are issued at 30-minute intervals and describe significant changes expected to occur during a 3-hour period. TTFs supersede aerodrome forecasts and the VOLMET information.

From 0130 the TTF for Sydney Airport included details of the south-westerly change expected at 0400. At 0333 a TTF was issued which indicated that the wind at Sydney was 200 degrees at 14 to 18 kts. This TTF, which the crew received via the ACARS, was appended with the term NOSIG, which indicated that there was no significant change expected within the next 3 hours. The TTF issued at 0403 indicated that the wind was 190 degrees at 7 to 12 kts and again included the term NOSIG.

The 0431 TTF reported the wind as 190 degrees at 17 to 24 kts. These conditions were unacceptable for a landing on runway 34L as the maximum certified tailwind of 15 kts for this aircraft would be exceeded. A special aerodrome forecast was issued 3 minutes later which reported the wind strength as 21 to 31 kts, with a resultant increased downwind component for a landing on runway 34L.

During aircraft operations, a point in the flight is reached where the crew need to make a decision to continue to the destination airport based on the weather and other conditions prevailing at that time. If conditions are not acceptable for arrival at the destination airport, the aircraft must proceed to an alternate airport. This point is usually designated as the decision point alternate (DPA). The DPA for this flight was Parkes NSW, with the alternate aerodrome nominated in the flight plan as Melbourne. At 0422, Melbourne Air Traffic Control (ATC) identified the aircraft's position on radar as 173 NM from Parkes.

The automatic terminal information service (ATIS) for Sydney was updated at 0424. This update reported that the wind direction was from 170 degrees and the strength was 10 to 20 kts with gusts to 25 kts and a maximum downwind component of 25 kts on runway 34L. This change in the ATIS was passed to the crew at 0426 and to two other international aircraft approaching Sydney.

The crew of the incident aircraft acknowledged that they had received this information. Shortly after, the crew advised ATC that their latest approach time to Sydney would be 0540. They also advised ATC that they had insufficient fuel to hold until 0600. The aircraft reached Parkes at 0444, 18 minutes after the new ATIS was broadcast, and continued towards Sydney.

In response to a query from ATC regarding diverting to Brisbane, the crew re-calculated the fuel status of the aircraft. Because the aircraft had passed the DPA, Melbourne was no longer a suitable alternative destination as there would be an excessive headwind en route. The crew advised ATC that if they proceeded to Brisbane immediately, they would have sufficient fuel. ATC asked the aircraft to stand by. Over the next 4 minutes ATC coordinated other traffic including aircraft entering holding patterns at Bindook. ATC subsequently asked the crew whether they intended to divert to Brisbane and the crew advised that they were now unable to do so as they had insufficient fuel. The fuel required to divert to Brisbane from this point was calculated by the crew to be 14,000 kg and there was only 13,200 kg remaining on board.

The crew informed ATC of the aircraft fuel status and that they would be proceeding to Sydney. ATC advised the crew that if they could not hold until 0600 and would therefore land during the curfew, they would have to declare an emergency. ATC then asked the crew to confirm that this was what they wished to do, to which the crew agreed. ATC then processed the aircraft ahead of the other preceding aircraft. The crew did not use the standard international phraseology to declare the emergency.

The crew again notified ATC that they could hold until 0540. ATC advised the crew that there would be no difference if they landed before this time as they would be landing on runway 16R prior to the lifting of the curfew.

During descent into Sydney, the crew assessed the possibility of making an approach to runway 34L, as the wind information from the aircraft Flight Management System (FMS) indicated that the wind still favoured an approach to runway 34. Information provided from Sydney Tower on the actual wind at the runway threshold precluded a landing on this runway. The aircraft landed on runway 16R at 0525, with more than the minimum fuel reserves in accordance with company policy.

Occurrence summary

Investigation number	199703429
Occurrence date	15/10/1997
Location	Sydney Airport
State	New South Wales
Report release date	01/11/1998
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Occurrence class	Incident
Highest injury level	None

Aircraft details

Manufacturer	The Boeing Company
Model	747
Registration	VH-OJB
Serial number	24373
Sector	Jet
Operation type	Air Transport High Capacity
Departure point	SINGAPORE
Destination	Sydney, NSW
Damage	Nil

Boeing 737-377, VH-CZH

Summary

During take-off from runway 17 at Melbourne the Boeing 737-300 aircraft experienced a single, rapid, right rudder deflection. This occurred when the aircraft was accelerating between V1 (135kt) and Vr (141kt). The co-pilot was handling the aircraft and was able to apply left rudder and arrest the developing yaw. The co-pilot advised that he applied between 2 and 3 inches of left rudder movement. The take-off and climb were completed without further problems and the flight proceeded normally to Adelaide.

An inspection of the aircraft failed to find any airframe or engine anomalies that could have contributed to the reported event.

After consultation with the manufacturer, it was determined that there was two possible causes for the right rudder deflection, namely a gust or a short duration rudder pedal pulse. Accordingly, the rudder power control unit (PCU), the standby rudder power control unit (SPCU), and the digital flight data recorder (DFDR) were removed for examination.

The DFDR recorded a maximum right pedal deflection of 0.17 inch. Because the DFDR only samples rate of pedal deflection twice per second it is possible that the maximum right pedal deflection recorded was not necessarily the peak of that particular deflection. The manufacturer advised that simulation of the event showed that a 3.3 inch right pedal pulse with a duration of 0.5 seconds would be needed to generate the lateral acceleration and heading changes recorded by the DFDR. This equates with the crew's report of between 2 and 3 inches of corrective rudder movement being applied.

The PCU was bench tested in accordance with the manufacturers requirements and found to be serviceable.

The manufacture advised that an identified cause of involuntary rudder movement was the binding of the input lever on the SPCU resulting in pedal feedback if the input lever binding force is sufficient to overcome the feel and centering unit restoring forces. Previous analysis of the SPCU input lever binding conditions indicates that approximately 20 lb resistive force at the input lever is required before any measurable uncommanded rudder pedal movement would occur. A mechanical binding force of this magnitude would be repeatable and would worsen over time. A limit of 1 lb binding force on the input shaft has been mandated. The removed SPCU was tested and the input lever binding force was found to be below the mandated limit. All other test requirements were found to be satisfactory.

A comparison of the airspeed and ground speed recording on the DFDR showed a fluctuation of airspeed at the time of the event accompanied by a fluctuation in the angle of attack vane. This suggests that a wind gust could have affected the airspeed and contributed to the yawing motion experienced by the aircraft.

The take-off had been commenced from intersection C on runway 16 with a reported surface wind of 10 to 15 knots from 130 degrees. Four minutes prior to the B737 take-off a B747 aircraft had departed using the full length of the same runway. The parameters for the B737 take-off would normally preclude wake turbulence from the B747 being considered as a factor.

The investigation was not able to determine if the gust that affected the aircraft was due to a local atmospheric disturbance or was as a result of lingering wake turbulence from the departing B747.

Occurrence summary

Investigation number	199703237
Occurrence date	06/10/1997
Location	Melbourne, Aero.
State	Victoria
Report release date	23/07/1998
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Aviation occurrence category	Control - Other
Occurrence class	Incident
Highest injury level	None

Aircraft details

Manufacturer	The Boeing Company
Model	737
Registration	VH-CZH
Serial number	23660
Sector	Jet
Operation type	Air Transport High Capacity
Departure point	Melbourne, VIC
Destination	Adelaide, SA
Damage	Nil

Bell 206B (III), VH-WCF, 204 km north-north-east of Geraldton, Western Australia

Summary

The helicopter was landed on an uneven 2 to 3 degree slope to offload two surveyors and their equipment. The forward sections of the skids were in firm contact with the ground, but because of the uneven surface the rear of the left skid was not in firm contact. After landing, the pilot lowered the collective and moved the cyclic control to confirm the helicopter was firmly seated on the ground before he allowed the passengers to disembark. The engine was running and the rotor was turning at 100% of operating RPM. There was a gusty 15-20 kt wind from 30 degrees to the right of the nose.

The rear seat passenger disembarked from the left (downhill) side, unloaded his equipment, and moved away from the helicopter towards the front as briefed. The front seat passenger disembarked from the left side, unloaded his equipment, climbed back on to the left skid, and reached into the cockpit through the door. The pilot said that he had been observing the site to his right to ensure it was clear, and when he looked back towards the front he realised the right skid was just off the ground. The pilot said he noticed a cool strong wind coming through his open window when the helicopter started to roll. He moved the cyclic control to the right but this had no effect. The pilot said he then pulled in collective but the helicopter continued to roll to the left and the left skid did not leave the ground. He then noticed the passenger on the top step on the left side. The pilot said he yelled at the passenger who immediately jumped off the step, closed the door and faced the helicopter with his arms outstretched. The helicopter continued to roll to the left and the passenger ran away directly to the left of the helicopter. As the weight came off the skids, the helicopter began to slide sideways down the slope. The slide was stopped, half a metre later by a partially buried stump and the helicopter rolled over. The pilot was unable to recover control before the rotor blades made contact with the passenger and the ground. The passenger was struck by at least one main rotor blade and was fatally injured.

It is probable that the helicopter very rapidly entered a condition known as dynamic rollover, where the only possible recovery action was to fully lower the collective. However, it is unlikely that the pilot had sufficient time to recognise the developing the situation and to take the appropriate action before the rollover became unrecoverable.

Occurrence summary

Investigation number	199703335
Occurrence date	12/10/1997
Location	204 km north-north-east of Geraldton
State	Western Australia
Report release date	25/02/1998
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Aviation occurrence category	Loss of control
Occurrence class	Accident
Highest injury level	Fatal

Aircraft details

Manufacturer	Bell Helicopter Co
Model	206
Registration	VH-WCF
Serial number	3134
Sector	Helicopter
Operation type	Charter
Departure point	108 NM NNE Geraldton WA
Destination	110 NM NNE Geraldton WA
Damage	Substantial

Mooney M2OJ, VH-KUE

Safety Action

Following a fatal accident involving a Cessna 310, the Bureau issued Interim Recommendation IR960059 on 21 October 1996. The recommendation stated "the Civil Aviation Safety Authority (CASA) ensure appropriate maintenance policies are developed for all general aviation aircraft pneumatic vacuum system components".

In its response to this recommendation, CASA undertook to prepare an article for inclusion in the journal Flight Safety Australia. This article, titled "The Silent Emergency", was published in the March 1998 issue and is an extract from the United States General Aviation Maintenance Administration's and Federal Aviation Administration's accident prevention program. The article deals with the hazards of flying in conditions of reduced visibility and encourages aircraft owners to consider the installation of a backup or standby pneumatic system for gyroscopic instruments.

CASA also undertook to prepare and issue an Airworthiness Advisory Circular (AAC 1-97). This AAC, issued on 21 May 1998, is titled "Functional Testing Aircraft Vacuum/Pressure Systems". The AAC highlights the manufacturer's recommended maintenance requirements for vacuum manifold systems.

AAC 1-98 titled "Dry Vacuum Pumps" has also been released. This AAC explains why dry vacuum pumps fail and outlines a pump replacement checklist. AAC 1-87 titled "Gyro Failures and How to Identify Early Failures" was also issued some time ago.

The Bureau identified a similar safety deficiency following this accident and will be investigating further aspects of vacuum pump maintenance.

Significant Factors

Vacuum pump failure during flight resulted in the loss of suction to the air-driven gyroscopic instruments.
Erroneous attitude and heading indications from these inoperative flight instruments.
Dark sky conditions with no discernible horizon.
The pilot had limited recent experience flying in conditions of reduced external visual reference.
Inability of the pilot to control the aircraft by sole reference to the remaining flight instruments.

Analysis

The circumstances of this accident were consistent with a loss of control by the pilot at night, resulting from inoperative attitude and directional indicators. The combination of a dark night, high level cloud, and limited ground lights would have provided the pilot with few external visual cues. This would have required him to quickly modify his instrument scan to allow him to control the aircraft by sole reference to the remaining flight instruments. One of those instruments, the electric turn coordinator, was probably the 'electric backups' that the pilot referred to in his call to FS.

To achieve a desired flight performance, the aircraft is placed in a particular attitude, together with an appropriate power setting. Precise attitude information can either be gained by reference to the natural horizon, or to a gyro-stabilised attitude indicator, when external indications are either not available or are unreliable. The altimeter, air speed indicator and vertical speed indicator can, in combination, also provide limited attitude information.

The loss of vacuum to the air-driven gyroscopic flight instruments would have resulted in those instruments providing erroneous aircraft attitude and heading indications to the pilot. It is possible that the pilot did not mask the failed attitude and directional indicators. Consequently, the pilot may have inadvertently continued to respond, however briefly, to the erroneous indications from the failed instruments. His instrument scan proficiency, with the attitude indicator as the primary focus, would have been developed over several years. Such a scan could not easily have been modified to ignore the very powerful stimuli from erroneous attitude indications.

The pilot was dependent on alternative instruments for aircraft attitude information and it is likely that while attempting to control the aircraft as well as calculate flight time and distance to Mildura, the pilot became spatially disorientated and lost control.

Summary

The aircraft was being flown from Adelaide to Dubbo in accordance with instrument flight rules. At 1921 EST, the pilot reported over Mildura maintaining 9,000 ft, and estimating abeam Griffith at 2026 on a direct track to Dubbo.

The weather in the area was clear, with no restrictions to visibility, and scattered cloud at 30,000 ft. Sky conditions were dark, with no moon.

At 1958 the pilot made a routine frequency change, and 8 minutes later advised Melbourne Flight Service (FS) there had been a loss of vacuum and that he was returning to Mildura. In response to enquiries from FS the pilot advised that he had 'electric backups' and felt it safer to return to Mildura. He also confirmed his approach and landing would not be affected, and that his estimated time of arrival would be 2029. At 2007 FS asked the pilot for his approximate distance from Mildura. The pilot asked FS to repeat the request, but subsequently failed to reply. Further attempts to contact the pilot were unsuccessful. The last recorded radio transmission from the pilot was at 2007:49.

An uncertainty phase was declared after communication and ground checks failed to establish the location of the aircraft. A local resident reported seeing the lights of an aircraft shortly after 2000, and then hearing the sounds of an impact. The wreckage of the aircraft was subsequently found some hours later. The accident was non-survivable.

An examination of the wreckage indicated the aircraft had impacted the ground at high speed, in a steep nose-down attitude, consistent with loss of control. With the exception of the vacuum system, the aircraft was considered to have been capable of normal operation prior to impact.

The aircraft was equipped with an attitude indicator and a directional indicator, each reliant on air-driven gyroscopes. An electrically powered turn co-ordinator was also fitted. Examination of the attitude indicator showed evidence of a witness mark consistent with the gyro-rotor being stationary at impact. The turn coordinator gyro-rotor was recovered and showed evidence of rotation at the time of impact.

The engine-driven vacuum pump and drive coupling were recovered from the wreckage. The impact resulted in separation of the pump body from its base. Only a few large pieces of the rotor and vanes were recovered. The frangible drive shaft coupling had sheared at some time prior to impact. A specialist examination considered that either the carbon rotor, or one or more of its vanes, had failed, resulting in pump seizure and consequent shearing of the drive coupling.

An entry in the aircraft logbook indicated that the vacuum pump was installed in September 1991. From that date, until the last periodic inspection in August 1997, the pump had operated for some 1,248 hours. No evidence was found of vacuum pump replacement during that period.

The Mooney 20J Service and Maintenance Manual recommends that the schedule for the primary vacuum pump replacement be either on condition or at 500 hours, and at engine overhaul. The Civil Aviation Safety Authority provides no additional requirements regarding maintenance of the vacuum pump.

The pilot held a Private Pilot licence with a valid medical certificate. His command instrument rating had expired 3 days prior to the accident. Although no evidence could be found of the pilot having flown in instrument meteorological conditions in the previous 12 months, the pilot had conducted a night flight six weeks prior to the accident. A passenger on that flight reported they did not encounter cloud.

Occurrence summary

Investigation number	199703221
Occurrence date	03/10/1997
Location	113 km NNE Balranald, Aero.
State	New South Wales
Report release date	01/11/1998
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Aviation occurrence category	Collision with terrain
Occurrence class	Accident
Highest injury level	Fatal

Aircraft details

Manufacturer	Mooney Aircraft Corp
Model	M20
Registration	VH-KUE
Serial number	24-1030
Sector	Piston
Operation type	Private
Departure point	Adelaide, SA
Destination	Dubbo, NSW
Damage	Destroyed

Ayres Corp S2R-T34, VH-OCR, 8 km south-east of Yenda, New South Wales, on 29 September 1997

Safety Action

As a result of this occurrence, the Bureau of Air Safety Investigation is assessing safety issues related to the following:

the design and use of the GPS "light-bar" used in agricultural operations; and
the overturn protection provided in two-place Ayres Thrush aircraft.

Significant Factors

The following factors were determined to have contributed to the accident:

The glare of the sun shining through the aircraft's windscreen may have partly obscured the tree from the pilot's field of vision.
The use of the Satloc light bar indicator may have resulted in the pilot focussing his eyes, for at least some of the time, on a close object causing distant objects, such as the tree, to be out of focus and thus more difficult to see.
The failure of the cockpit truss to remain in position when the aircraft struck the ground inverted made the accident unsurvivable.

Analysis

Manoeuvring the aircraft to commence the next swath run was a high workload period for the pilot, requiring precise flying to position the aircraft accurately in both lateral and vertical planes. As the pilot was lining the aircraft up to conduct a swath run in a westerly direction in the late afternoon, the sunlight coming through the windscreen would have created glare in the pilot's field of vision, partly obscuring the tree. When using the Satloc system's light bar indicator to align the aircraft with the line of the next swath run, the pilot's vision would have been focussed, for at least some of the time, on the light bar. When the pilot's eyes were focussed on the light bar, more distant objects, such as the tree, would not have been in focus and would therefore have been harder to see. Although the pilot must have been aware of the tree's presence, the high workload, the glare from the setting sun and the pilot focussing on the light bar indicator all contributed to the pilot temporarily being unaware that the tree infringed his intended flightpath.

The damage to the left wing when it struck the tree would have resulted in a loss of lift and an increase in drag from this wing. This would have caused the aircraft to roll rapidly to the left and, as the ailerons had jammed, the pilot would have been unable to stop the roll. Thus, after impact with the tree, the aircraft was most likely uncontrollable.

When the cockpit truss was tom from the aircraft, the space remaining between the ground and the pilot's seat was too small for the accident to have been survivable.

Summary

The aircraft took off from a private airstrip on Farm 1303 at Whitton NSW on a flight to spray chemical on two paddocks at Farm 2339, Dalton Road, Yenda. Eyewitnesses reported watching the aircraft spray the first paddock using north-south oriented runs. When the first paddock was completed, the pilot commenced spraying the second using east-west oriented runs, starting at the northern end of the paddock. After making several spray runs, the pilot finished a run heading in an easterly direction. He pulled the aircraft up and commenced a right procedure turn to line up for the next run in a westerly direction. While lining up for this run, the left wingtip struck the upper branches of a large dead tree which was located close to the boundary of the paddock being sprayed. The point of impact was approximately 0.5 m inboard of the left wingtip. A piece of branch, 200 mm in diameter, broke off the tree. The left wingtip and several small pieces of wing material separated from the aircraft at impact.

Eyewitnesses reported that the aircraft immediately rolled to the left and impacted the ground inverted. The aircraft slid along the ground before coming to rest inverted. The aircraft did not catch fire but was destroyed by impact forces. The pilot received fatal injuries. Witnesses advised that the weather conditions at the time of the accident were clear skies and light winds. Being late afternoon, the sun was visible in the western sky.

Examination of the accident site revealed that the aircraft had struck branches about 20 m above ground level with its left wingtip. The wingtip and several pieces of the wing landed up to 180 m west of the tree. Ground scars indicated that the aircraft impacted the ground inverted. The fuselage, wings and empennage remained relatively intact and were located approximately 41 m south of the initial ground-impact marks. Propeller slash marks indicated that the engine was producing power at ground impact. The cockpit truss had separated from the fuselage and was located about 22 m from the aircraft's final resting position. The ailerons were jammed in the neutral position.

Examination of the wreckage did not reveal any pre-existing defects or malfunctions that would have precluded other than normal operation. An inspection of the maintenance records showed that all required maintenance had been completed.

The pilot was the holder of a commercial pilot licence and was appropriately qualified for the flight. He had held a Grade 1 agricultural rating since 11 September 1985 and had flown 14,816 hours. At the time of the accident, the aircraft's calculated weight was 2,876 kg, less than the maximum weight authorised for agricultural operations of 3,042 kg. The aircraft's calculated centre of gravity was within limits.

The aircraft was fitted with a Satloc navigation system, which provided the pilot with guidance commands to fly accurate spray patterns. The guidance indications were displayed on a light bar which was mounted on top of the fuselage in front of the aircraft windscreen. The display was approximately 1 m in front of the pilot's eyes. Witnesses suggested that the pilot normally used the Satloc system and its light bar indicator during spraying operations.

Occurrence summary

Investigation number	199703150
Occurrence date	29/09/1997
Location	8 km SE Yenda
State	New South Wales
Report release date	01/11/1998
Report status	Final
Investigation type	Occurrence Investigation
Investigation status	Completed
Mode of transport	Aviation
Aviation occurrence category	Collision with terrain
Occurrence class	Accident
Highest injury level	Fatal

Aircraft details

Manufacturer	Ayres Corporation
Model	S2R
Registration	VH-OCR
Serial number	T34-135DC
Sector	Piston
Operation type	Aerial Work
Departure point	Farm 1303, Whitton NSW
Destination	Farm 1303, Whitton NSW
Damage	Destroyed

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