Loss of control

Interim factual report released 25 July 2008

On 9 April 2008, a Fairchild Industries Metro III aircraft departing Sydney, NSW was observed on radar to be turning contrary to air traffic control instructions. The pilot reported that he had a '...slight technical fault...'. Recorded radar data showed the aircraft then completed a turn to the left before turning back to the right and disappearing from radar at an altitude of 3,900 ft. Searchers later discovered a small amount of aircraft wreckage floating in the ocean, south of the last recorded radar position. The pilot was fatally injured, and the aircraft was destroyed.

On 29 November 2006, an Australian Army Black Hawk helicopter, A25-221, crashed during a training flight. The helicopter was attempting to land on HMAS Kanimbla located in international waters off Fiji. Onboard the helicopter were 10 army personnel - four aircrew and six soldiers. Of those onboard, eight survived and two were fatally injured.

The helicopter sank in deep water and the flight data recorder (FDR) was recovered in March 2007 after a salvage operation. The Australian Department of Defence was responsible for investigating this accident and appointed a Board of Inquiry. The Department of Defence requested ATSB assistance in the recovery of data from the FDR. The Executive Director of the ATSB approved the request. To protect the information supplied by the ATSB to Defence and investigation work undertaken to assist Defence, the ATSB initiated an investigation under the Transport Safety Investigation Act 2003.

The solid-state memory was successfully downloaded and a copy of the data file was provided to a representative from the Directorate of Defence Aviation and Air Force Safety.

Information publicly released by the Board of Inquiry is available on the Department of Defence website: http://www.defence.gov.au

During an approach into Cairns Airport, Qld in overcast conditions late on the morning of 2 December 2006, the pilot of a Piper Navajo aircraft, registered VH-BTD, lost control of the aircraft and entered an uncontrolled descent. Control of the aircraft was regained shortly before the pilot became visual below the cloud base, and the pilot continued to Cairns.

The loss of control was the result of the pilot's inexperience with respect to the effects of spatial disorientation and with flight in instrument meteorological conditions (IMC).

This occurrence reaffirms the potential for spatial disorientation, if not recognised and recovered from appropriately, to result in the loss of aircraft control.

On 2 November 2006, the pilot of a Bell Helicopter Company 206A helicopter, registered VH-AAL, departed Coffs Harbour, NSW, on a private flight to a property located at Palmers Island, near Yamba, NSW. On board the 206A were the pilot and one passenger in the front left seat.

On arrival in the vicinity of Palmers Island, the pilot commenced a downwind turn into a strong quartering tailwind and the helicopter began an uncommanded right yaw. The pilot attempted to regain control, but the helicopter continued to yaw and to descend until it impacted the ground. The pilot and passenger sustained serious injuries and the helicopter was destroyed.

There was no evidence found of any mechanical or systems failures that may have contributed to the accident. The reported local conditions and nature of the loss of control were consistent with a loss of tail rotor effectiveness (generally referred to as LTE).

While a serviceable emergency locator transmitter was fitted to the helicopter, it had not been 'armed' prior to the flight and did not activate as a result of the impact.

Preliminary report released 31 October 2006

On 31 October 2006 at 1955 Eastern Standard Time, PA31-350 aircraft, registered VH-ZGZ, was on descent to Gladstone Airport, Qld when its radar track disappeared from the air situation display in the Brisbane Air Traffic Control Centre. Subsequently, the aircraft was found to have impacted terrain approximately 9 km south-east of Raglan, Qld. The pilot and two passengers were fatally injured. The aircraft was destroyed by impact forces and post-impact fire.

Interim Factual report released 22 September 2006

At 0728 Eastern Standard Time on 31 March 2006, an amateur-built Lancair 320 aircraft, registered VH-BST, departed Townsville, Qld, on a private flight to Archerfield Aerodrome, Qld. The pilot, who owned the aircraft and was the sole occupant, had earlier submitted a visual flight rules (VFR) flight plan for the flight.

At 1048.30, the pilot contacted the Archerfield Aerodrome Controller and reported that he was 19 miles (35 km) from the aerodrome and inbound. He said that he was new to the area and would appreciate any help. The controller advised the pilot to report at the TV towers, a VFR reporting point 13 km north-west of Archerfield. The aircraft was maintaining about 3,700 ft AMSL (above mean sea level).

The pilot reported at the TV towers but had difficulties finding the aerodrome. Radar data showed that the aircraft was 2 km north of the aerodrome at 1,700 ft AMSL, and tracking south-south-east. At 1058.11, the controller asked the pilot if he had the aerodrome in sight. The pilot said that he did not, and said 'I feel I've overflown it'. The controller advised that radar information indicated that the aircraft was north of the aerodrome, and he suggested that the pilot continue to turn left. The pilot then acknowledged that transmission. No further radio transmissions were received from the pilot.

Witnesses reported seeing the aircraft's left wing drop and the aircraft appeared to enter a spin before descending straight down, colliding with a tree and then a creek running parallel to Kessels Road, Coopers Plains. The aircraft was destroyed and the impact was not survivable.

Preliminary report released 11 April 2006

A turbine-engined PZL-Warszawa-Okecie M-18A Dromader aircraft, registered VH-FVF (callsign Bomber 223), was conducting fire suppression operations on a bushfire in the vicinity of Mount Ulandra, near Bethungra, NSW. At 1921 Eastern Daylight- saving Time, the aircraft was seen by fire fighters to make a low pass over the fire ground area and commence a left turn. Another fireman reported seeing the aircraft in an almost vertical left bank before losing sight of it. None of the other firemen continued to watch the aircraft but, moments later, they reported that they heard a loud noise. When they looked again, the aircraft had hit the ground. The pilot was fatally injured, and the aircraft was destroyed by impact forces. There was no fire.

The crew of a helicopter engaged in fire bucket operations on the same fire ground reported hearing the Dromader pilot broadcast that he was 'lining up for a drop'. A short time later, the helicopter crew reported that they heard the pilot transmit three short expletives. After unsuccessfully attempting to contact the pilot, they commenced searching and located the wreckage of the aircraft a few minutes later, where fire fighters were already in attendance.

The aircraft had impacted open, rising terrain in a nose-down, slightly right wing-low attitude. Examination of the impact marks and the wreckage indicated that the aircraft had been travelling at low forward speed and with a high rate of descent. The ground around the wreckage was covered with a considerable amount of chemical retardant from the ruptured hopper (Figure 1).

Figure 1: Aerial view of wreckage

The aircraft was manufactured in Poland in 1988 and placed on the Australian register in March 1999. In November 2003, the aircraft was modified from the original design in accordance with an approved Supplemental Type Certificate (STC), number SA09039SC, which permitted the replacement of the original reciprocating (radial) engine and the 4-blade propeller with a Garrett TPE 331-12U gas turbine engine and a Hartzell 5-blade constant speed propeller. The modification also incorporated other changes that included the replacement of the hopper with a larger, 800 US gallon (3,030 L) hopper. Additionally, servo tabs were added to the primary flight control surfaces, flap travel was increased and vortex generators were installed on the wings and tailplane.

The aircraft was operated in the restricted category ¹ that permitted flight at weights up to 5,300 kg during agricultural operations, which was 1,100 kg in excess of the certified maximum aircraft weight. Flights at those weights restricted the aircraft's maximum speed and, during fire suppression operations, manoeuvring was limited to a maximum angle of bank of 30 degrees.

The pilot held a commercial pilot licence, endorsed for the aircraft type, and a valid Class 1 medical certificate. The pilot also held a Grade 1 Agricultural Rating and had been issued a Night Visual Flight Rules Agricultural Rating on 19 December 2004. The test for that rating met the requirements of the Aeroplane Flight Review, the biennial proficiency check required of pilots. The pilot had in excess of 4,000 hours in agricultural flying operations, of which 127 hours were flown in fire suppression operations over a period of six seasons. Although the pilot had only 4.7 hours on the aircraft type, he had flown over 400 hours on the unmodified radial-engine Dromader aircraft type, and had over 600 hours on other turbine-powered aircraft. The pilot had commenced fire bombing operations two days before and was reported to have been well rested and in good health.

The investigation is continuing and will include the following aspects:

• analysis of data downloaded from the aircraft's Global Positioning System navigation receiver to determine the actual flight path
• testing of the switches controlling the hopper gate
• examination of other aircraft components
• a review of maintenance documentation and records of modification made to the aircraft
• an appraisal of flight characteristics of the modified aircraft during operations at higher gross weights.

1. Restricted category aircraft are certified by the Civil Aviation Safety Authority to conduct certain special purpose operations.

During a charter flight from Broome, WA to Cone Bay, WA, the pilot of an amphibious (float and landing gear equipped) Viking Air Ltd DHC-3-T 'Turbo-Otter' aircraft (VH-OTV) reported an unusual movement within the control system, followed by a sudden downward pitching motion, leading to a rapid and uncontrolled descent.  With the assistance of the front seat passenger, the pilot was able to arrest the descent and regain control of the aircraft, before making a precautionary landing at Lombadina Station, WA.

An engineering assessment of the aircraft found that the right elevator servo tab had broken away from the control rod and horn at the outboard end.  Damage to the elevator trailing edge and tearing of the tab through the mid-span was consistent with gross oscillatory movement (flutter) of the tab after it had become disconnected from the rod and horn.

Aerodynamic flutter within the elevator trim and servo tabs of the DHC-3 aircraft type had been known since the 1960s, however the development of turboprop engine conversions for the aircraft had resulted in an increased potential for tab failure as a result of the increased airspeeds and control surface loads associated with the re-engined aircraft.  A series of engineering solutions to the flutter problem had been subsequently developed, and in April 2004, a US Federal Aviation Administration airworthiness directive (AD) mandated the modification of the DHC-3 elevator tab assembly for US registered aircraft.

At the time of the occurrence, VH-OTV had not undergone the elevator tab modifications.  The maintenance organisation stated that it was unaware of the FAA actions and had not received any information as to the availability of flutter prevention modifications from the aircraft type certificate holder or the certificate of registration holder.

Safety action taken by the maintenance provider after the occurrence included the implementation of systems to more adequately alert the organisation to the existence of important safety bulletins and airworthiness directives affecting the aircraft.  An airworthiness directive for the elevator tab modifications issued by Transport Canada the month before the occurrence, became effective on 31 March 2006 and, on 1 March 2006, the Civil Aviation Safety Authority (CASA) introduced an AD to mandate the prospective Transport Canada requirements from 31 May 2006.

On 12 February 2006, the pilot of a Robinson Helicopter Company R44 Raven II Newscopter, registered VH-WYS, was conducting aerial filming of a banner towing helicopter in the vicinity of Williamstown, Vic. On board with the pilot were a photographer in the front left seat and a gyro-stabilised camera operator in the rear left seat.

While in a turn at low airspeed, and with a quartering tailwind, the helicopter began an uncommanded yaw to the right. The pilot attempted to regain control, but the helicopter continued to rotate to the right and descended approximately 1,800 ft before control was regained. The helicopter was flown to a nearby beach and landed.

The reported ambient conditions and nature of the loss of control were consistent with the pilot report that the helicopter had suffered a loss of tail rotor effectiveness (LTE). It was possible that the onset of vortex ring state had contributed to the high rate of descent during the pilot's recovery from the LTE.

Helicopter manufacturer

On 19 December 2005, the helicopter manufacturer advised the Australian Transport Safety Bureau (ATSB) that the procedure for setting the autorotation rotor RPM contained in the Kawasaki Heavy Industries BK 117 B-2 (BK 117 B-2) maintenance manual did not cover operation of the helicopter at high gross weight. In order to correct that procedure, the manufacturer advised the operator to re-set the helicopter's collective pitch setting in accordance with the relevant procedure in the BK 117 C-1⁸ model helicopter's maintenance manual, which can be used to set the helicopter's autorotation rotor RPM at high gross weight.

On 20 December 2005, the helicopter manufacturer advised the ATSB that it intended amending the BK 117 B-2 maintenance manual to reflect the procedures detailed in the BK 117 C-1 manual, and that it would advise all customers who operated the BK 117 B-2 helicopter of the change to the maintenance manual. A temporary revision to the manual was subsequently issued by the manufacturer. On 20 January 2006, the maintenance manual was amended to include the procedure for setting autorotation rotor RPM in the BK 117 B-2 at high gross weight.

Australian Transport Safety Bureau

The ATSB provided an initial alert to the Civil Aviation Safety Authority (CASA) of this safety deficiency on 15 December 2005. Further information on the progress of the ATSB investigation was provided to CASA technical staff on 19 December, with notice of the likelihood of the ATSB issuing a safety recommendation provided later that day. On 21 December 2005, CASA technical staff met with ATSB investigators and, following a briefing, advised the ATSB that CASA would alert operators about this safety deficiency.

On 22 December 2005, the ATSB issued the following safety recommendation R20050014 to CASA. That recommendation stated:

The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority alert Australian operators of the Kawasaki BK 117 B-2 helicopter to the discrepancy with respect to the procedure for adjusting the collective pitch settings in the maintenance manual.

On 22 December 2005, CASA wrote to all Australian owners and operators of the BK 117 B-2 helicopter and recommended that, pending advice from the helicopter manufacturer, operators of the BK 117 B-2 should:

• reduce exposure to conditions of high-density altitude and atmospheric turbulence, especially if the aircraft is at high gross weight
• if such conditions were encountered, reduce airspeed and torque settings while hand flying the aircraft with SAS [Stability Augmentation System] mode engaged.

On 7 February 2006, CASA advised the ATSB that the helicopter manufacturer had provided all Australian operators of the BK 117 B-2 helicopter with the amended procedure for setting the collective pitch setting.
In response to the safety action undertaken by CASA and the helicopter manufacturer, the ATSB has classified safety recommendation R20050014 as 'Closed-accepted'.

8. The BK117 B-2 helicopter type certificate also included the BK 117 C-1 model helicopter.