On 9 June 2013, an Australian-registered Cessna 206 aircraft, registration VH-JIA, was extensively damaged in an accident while attempting to land on a beach strip near Bukaua River, Papua New Guinea. The pilot reported that during the landing roll, the nose landing gear fork had failed, allowing the aircraft to dig into the soft sand and flip over.
The Accident Investigation Commission (AIC) of Papua New Guinea was responsible for investigating this accident. As part of its investigation, the AIC requested technical assistance from the Australian Transport Safety Bureau (ATSB), in the metallurgical examination of the failed landing nose fork and the download and analysis of the pilot's navigational GPS unit that was recovered from the accident site. To provide the necessary protections for the GPS information and the findings of the landing gear analysis, the ATSB appointed an Accredited Representative to the investigation in accordance with clause 5.23 of Annex 13 to the Convention on International Civil Aviation (ICAO Annex 13), and initiated an investigation under the Australian Transport Safety Investigation Act 2003.
Landing gear analysis
The characteristics of the nose landing gear fork failure revealed during the ATSB laboratory examination were consistent with fracture occurring from a pre-existing manufacturing condition that predisposed the fork to brittle fracture along the forging seam (parting) lines during conditions of elevated lateral stress (such as sustained during beach or other soft-surface landings). The fracture surfaces showed no evidence of fatigue cracking, stress-corrosion cracking or other progressive failure mechanisms. Cracking and failure of Cessna nose forks has been an isolated but recurrent problem for Cessna 100- and 200-series aircraft, and a supplemental inspection ('32-20-01 Nose Landing Gear Inspection') has been promulgated by the manufacturer to address the issue. In light of the history of related failures contained on the Australian record, the Australian Civil Aviation Safety Authority (CASA) is considering a review of their existing Airworthiness Bulletin, AWB 32-016 Cessna Single Engine Nose Landing Gear Forks, with respect to this issue.
GPS download
Following recovery and preliminary examination of the GPS track data, it was evident that the most recent information stored on the device was recorded approximately twelve months prior to the accident. As such, the ATSB concluded that the unit had not been in use during or immediately prior to the accident flight, or the track recording functionality had been switched off.
Provision of information to the AIC:
The findings of the ATSB's examination of the nose landing gear and GPS examination were provided to the PNG-AIC on 7 January 2014, and the components were subsequently returned to the AIC investigator in-charge. The AIC is responsible for releasing a final investigation report into this occurrence.
On the afternoon of 28 June 2014, the 327 m long bulk carrier Julia N entered the port of Port Headland, Western Australia, and was manoeuvred alongside Anderson Point number two berth by the pilot with the assistance of four tugs.
At 1521[1], when it had been confirmed that the ship was in position, the pilot called the master of the tug at the stern of the ship to come in and retrieve its tow line (Figure 1 and Figure 2). When the tug was in position, the pilot asked Julia N’s master to instruct the aft mooring team (second mate and two seamen) to let go the tug’s tow line.
Figure 1: Approximate position of the tow line during retrieval[2]
Source: Jens Boldt – Shipspotting with annotations by ATSB.
Figure 2: View of Julia N from the tug’s bridge window
Source: Teekay Australia.
Figure 3: Crew and messenger line positions
Source: Julia N with annotations by ATSB
Seaman 1 (Figure 3) ran the messenger line[3] over the drum end of the mooring winch, while seaman 2 operated the winch to pull about 2 m of tow line inboard. The second mate wrapped the rope stopper around the main tow line while the messenger line was taken off the drum end and the eye of the tow line off the mooring bits. The messenger line was then put around the forward post of the mooring bits to assist with the controlled lowering of the tow line.
On board the tug, the general purpose hand was standing forward of the winch (Figure 4) ready to guide the tow line onto the winch drum and the engineer was at the remote winch controls inside the bridge.
The general purpose hand signalled to the engineer that he could begin heaving in the tow line but the engineer waited until he saw the tow line being lowered.
Figure 4: Position of the general purpose hand and the engineer.
Source: ATSB.
As the tow line was retrieved, seaman 2’s right leg somehow became entangled in the messenger line. He was then dragged about 4 m across the deck and into the rollers of the fairlead. When his legs entered the fairlead the messenger line came under tension and it severed the seaman’s right foot.
As the eye splice of the tow line reached the fendering on the bow of the tug, both the general purpose hand and the engineer saw the line go tight. The general purpose hand signalled to the engineer but he had already stopped heaving.
Julia N’s second mate ran to the ship’s rail and signalled to the general purpose hand to slacken the line. Then, on the general purpose hand’s signal, the engineer paid out about 2 m of line.
At 1524, the pilot advised Port Hedland Vessel Traffic Service (VTS) that there was a medical problem on board the ship and instructed the tug’s master to hold position with a slack line as there had been a problem on the aft mooring deck with the line. A short time later, after receiving more information, the pilot advised VTS what had happened. He also requested medical assistance from the terminal operator.
Between 1545 and 1555, two launches arrived with first aid personnel and, at 1601, a helicopter with two paramedics landed on board Julia N.
At 1644, the helicopter departed with the injured seaman. He was taken to the Port Hedland Hospital, where he was provided with medical treatment.
At 1750, the pilot reported to VTS that Julia N was all fast alongside the berth and he was departing the ship.
The injured seaman continued to receive treatment in the Port Hedland Hospital until he was repatriated on 12 July.
ATSB comment
From his position at the port bridge console, the tug’s engineer could see the tow line, the winch and the general purpose hand. However, due to the freeboard of the ship, no one on board the tug could see past the ship’s main deck hand rails. As is usual, the tug’s crew had no direct radio communications with the ship’s aft mooring team, and were therefore reliant on visual contact with the mooring team for all communications.
There were three crew members (second mate and two seamen) on the aft deck for mooring operations and it is likely that the second mate felt that he needed to assist the two seamen when releasing the tugs line from the bits. However, when doing so, he was not at the ship’s side where he had a clear line of sight of the tug, and as such had relinquished his supervisory role. Then, when the seaman became entangled in the messenger line, there was no one on the aft deck of the ship in a position to signal to the tug’s crew to stop retrieving the line.
The investigation was not able to interview the injured seaman, and from the evidence provided, was not able to ascertain how the seaman’s leg became entangled in the messenger line while it was being retrieved on board the tug.
There is no clear evidence to determine the actions of the second mate and how they were interpreted by the tug’s crew as a positive signal to retrieve the tow line.
Safety action
Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following safety action in response to this occurrence.
Teekay Australia
A Safety Alert was sent to all of its managed ships advising of the accident, the safety message and safety actions to be taken.
Neu Seeschiffahrt
Each managed ship received a Corrective and Preventative Action Report which contained the company’s internal investigation report, references to various procedures related to mooring and tug operations as well as corrective actions and long term preventative actions.
Safety message
Mooring operations are often seen as a routine task but contain dangers that are often not realised until it is too late. As they cannot be directly observed, the forces that can be exerted on mooring and towing lines, even by their own weight, are often underestimated by those working around them.
Serious injury is likely when there is an incident during tug and mooring operations, but the likelihood of such an occurrence can be managed through effective risk assessment, training, supervision, communications and good housekeeping – both prior to and during berthing operations.
The ATSB’s SafetyWatch highlights the broad safety concerns that come from its investigation findings, and from the occurrence data reported by industry. One of the ATSB’s current SafetyWatch concerns relates to marine work practices. Readers are encouraged to examine the information and experiences presented at the web link below, and relate those to the context of their own duties.
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
[1] All times referred to in this report are local time, Coordinated Universal Time (UTC) + 8 hours.
[2] Photo is for illustrative purposes. At the time of the incident, Julia N’s draft was less than shown in the photograph.
[3] The messenger line was a 25 mm diameter rope attached to the eye of the main tow line by a short flat webbing sling. It was measured at 21.7 m long after the incident.
On 13 December 2013, a Hughes 500D helicopter, registration ZK-HNA, was flying from Rat Point on Lake Wakatipu, 16 km South West of Queenstown, New Zealand, to Dumpling Hut on the Milford Sound walking track. When the helicopter did not arrive at its destination, the alarm was raised, and after a short search, the wreckage of the helicopter was found near the top of the Glade Burn Valley. The pilot, who was the sole occupant of the helicopter, had been fatally injured.
The Civil Aviation Authority of New Zealand (CAANZ) is undertaking a formal investigation into this accident. As part of that work, the CAANZ requested technical assistance from the Australian Transport Safety Bureau (ATSB), in the recovery of data from a damaged navigational GPS unit recovered from the accident site. To protect the information supplied by the CAANZ, and any data recovered from the GPS unit, the ATSB initiated an investigation under the provisions of the Transport Safety Investigation Act 2003.
Following examination and disassembly, it was evident that the GPS unit had sustained circuitry damage sufficient to prevent its download by conventional means. Subsequently, the discrete device (chip) containing the track memory was identified, removed, and a raw data file downloaded using specialised techniques. Decoding of the raw information showed that the entire track memory had been recovered, including the accident flight and several previous flights. The data and a report detailing the download procedure was provided to the CAANZ on 26 June 2014 for use in their investigation.
On the morning of 29 June 2014, the pilot of a de Havilland Canada DHC-1 T Mk 10 Chipmunk aircraft, registered VH-UPD, was taking a passenger for a brief, private flight over Coffs Harbour Regional Airport, New South Wales.
According to pilot and passenger reports, after conducting a series of aerobatic manoeuvres, the pilot climbed to about 3,800 ft and accelerated to about 85 kt. The pilot then made a short dive to build up speed to about 120 kt before commencing a loop.
At the top of the loop, the aircraft stalled while inverted, most likely as the result of excessive elevator input. The aircraft rolled and entered an upright spin, which became flatter as it developed. Later, the pilot reported that attempts to recover were unsuccessful. The spin continued until the aircraft impacted terrain. The pilot and passenger sustained serious injuries and the aircraft was seriously damaged. There was no fire.
What the ATSB found
The pilot reported undertaking training to conduct loops, but there was no record of an endorsement and the instructor did not recall approving the pilot to conduct loops. As a result, at the time of the accident, the pilot likely did not possess the necessary skills and judgement to conduct the manoeuvre safely and consistently.
The pilot probably did not apply and maintain the spin recovery control inputs appropriate for a fully-developed spin in a Chipmunk aircraft. Furthermore, the pilot was taught a spin recovery method that was not effective for recovering from such spins in the aircraft.
In addition, the accident aircraft’s flight manual had not been approved by the Civil Aviation Safety Authority and did not include advice on spin recovery. The mandatory, Civil Aviation Safety Authority-approved flight manual contained spin recovery advice.
What's been done as a result
The flying school that provided the pilot’s aerobatic training reported that a briefing process was undertaken with all current aerobatic instructors to ensure that consistent terminology is used to describe and teach aerobatic manoeuvres. It also reported that a programme of standardisation flights for all current aerobatic instructors will include the training of spin and unusual attitude recovery for aerobatic students.
Safety message
Pilots and instructors, particularly those intending to conduct or teach aerobatic manoeuvres, should be familiar with any special handling requirements for a particular aircraft type as well as recovery from both incipient and developed spins. Furthermore, they should ensure that they hold the appropriate aerobatic endorsement before attempting a manoeuvre.
VH-UPD accident site
Source: ATSB
The occurrence
On the morning of 29 June 2014, the pilot of a two-seat de Havilland Canada DHC1 T Mk 10 Chipmunk aircraft, registered VH-UPD (UPD), was making a series of short, private flights in the vicinity of Coffs Harbour Regional Airport, New South Wales. The pilot carried a different passenger on each flight, and flew the aircraft from the front seat.
After about three or four flights, and with a new passenger on board, the pilot requested and received air traffic control clearance to conduct ‘airwork’ over the airport, not above 4,000 ft above mean sea level.[1] The pilot took off at about 1127 Eastern Standard Time[2] on what was the first flight of the day that was intended to include aerobatic manoeuvres.
After climbing to about 3,800 ft, the pilot conducted a series of manoeuvres. The aerobatic sequence usually flown by the pilot consisted of a shallow dive to accelerate to about 120 kt, followed by a loop, an aileron roll and two wingovers (the latter manoeuvres were each commenced at 100 kt). The pilot reported that the sequence usually finished about 1,000 ft lower than the initial height.
The pilot reported that he subsequently climbed back to 3,800 ft and accelerated to about 85 kt. The pilot then made a short dive to again build up speed to about 120 kt before commencing a second loop. The aircraft’s height during the manoeuvres could not be confirmed with any accuracy but, based on the pilot’s report and calculations derived from witness reports, the entry height for the second loop was probably higher than 3,000 ft.
Witnesses reported that while inverted at the top of the manoeuvre, the aircraft stalled and rolled to the right. The aircraft then entered an upright spin to the right which became flatter as it developed. The pilot reported being aware of the spin and feeling ‘panicked’, finding that his attempts to recover from the spin were unsuccessful. The pilot tried different control inputs in an attempt to recover, including right and left rudder and applying left and right aileron, but did not recall moving the control stick forward. The passenger later reported that during the descent, the pilot was manipulating the controls and talking, but the passenger could not recall how the controls moved.
Video footage taken by witnesses showed the last 15 seconds of the flight with the aircraft established in a slow, upright spin to the right from about 1,200 ft. The aircraft’s pitch attitude was about 30° nose-down during the spin. The spin continued until the aircraft impacted terrain at about 1136, in a narrow strip of forested land between the airport and the beach. The airport’s air traffic controller observed the spin and immediately initiated emergency and rescue procedures.
The pilot and passenger sustained serious injuries and the aircraft was seriously damaged. There was no fire.
The pilot held a Private Pilot (Aeroplane) Licence that was issued in 2004, and a valid Class 2 Medical Certificate with a condition to have reading correction available when exercising the privileges of the licence. The medical certificate was valid until May 2016.
The pilot’s logbook indicated a total aeronautical experience of 155.7 hours, not including the four or five brief flights on the day of the accident. The pilot last completed an aeroplane biennial flight review on 24 May 2014.
The pilot later reported feeling well rested, healthy and in a good mood on the day of the accident. He had no significant medical conditions and had not taken any medications or consumed any alcohol.
Aerobatic training and flying history
To be authorised to conduct aerobatics as pilot-in-command, a pilot must hold a logbook endorsement for spin recovery and a logbook endorsement for the aerobatic manoeuvres to be conducted.
The pilot’s aerobatic and spin recovery endorsement training was conducted in another de Havilland Canada DHC-1 T Mk 10 Chipmunk operated by a flying school. The flying school’s syllabus estimated 1.0 hour’s instruction each for unusual attitude recovery, aileron rolls, wingovers and loops, and 1.5 hours for spin recovery. According to the syllabus, unusual attitude recovery and spin recovery competency were prerequisites for aerobatic endorsements. All of the pilot’s spin training was to the left.
According to the pilot’s logbook, endorsements for wingovers, aileron rolls and spin recovery were approved on 7 July 2013, after 3.5 hours of aerobatic instruction. There was no recorded endorsement for loops and the flying school instructor later reported that he had probably demonstrated a loop but that he did not formally endorse the pilot to conduct them as pilot in command. The pilot thought he held the appropriate endorsement to conduct loops.
The pilot’s logbook recorded an instructional flight on 1 February 2014 that was labelled ‘aerobatic sequence’. This brought the pilot’s total dual aerobatic instruction time to 4.4 hours.
The combined total dual and solo time recorded in the pilot’s logbook for aerobatic flights in the Chipmunk was 10.2 hours, all of which was in UPD and the flying school’s Chipmunk. Of those flights, two also included circuits.
The most recent recorded aerobatic flight in a Chipmunk was on 22 March 2014.
Prior to their Chipmunk training, the pilot had conducted spin recovery training in a DH-82 Tiger Moth and an American Champion Citabria. The pilot reported that those aircraft were more responsive to spin recovery control inputs when compared with the Chipmunk.
An instructor who had flown with the pilot reported that the pilot’s flying was ‘hard to fault’ and ‘diligent’.
Spin recovery training
The pilot reported that his actions for spin recovery were normally to apply full opposite rudder and a small amount of opposite aileron, and to centralise the elevators. The method did not vary between any of the aircraft types flown by the pilot.
Two instructors were recorded in the pilot’s logbook as having taught the pilot aerobatics in the Chipmunk. Both instructors were suitably qualified and approved to conduct aerobatic training. The flying instructor who endorsed the pilot for spin recovery reported using and teaching the following method for spin recovery in the Chipmunk:
throttle closed
full opposite rudder
neutral aileron
move the elevators about two thirds of the way from full back towards the central stick position but not all the way.
The instructor stated that the aim was to place the flight controls in a position that produces maximum lift, and that this helped stop the stall that would otherwise sustain the spin. The instructor stated the elevator control should not be put fully-forward to prevent entering an inverted spin.
The second instructor could not specifically recall teaching the pilot, but described a similar spin recovery method with the exception that the pilot should continue pushing the control stick forwards (elevators down) until the rotation ceases. The flying school’s chief flying instructor reported that forward stick should be applied during spin recovery.
The pilot and first instructor reported that during instruction and evaluation in the Chipmunk, spin recovery action would commence after about one or one and a half turns (that is, 360°–540° from the original heading). They reported that the spin would cease after a further one or one and a half turns. The flying school’s operations manual did not include instructions on the appropriate number of turns in a spin before recovery should be attempted, and the chief flying instructor advised that spin recovery would normally be initiated within about two turns.
The flying school did not maintain records of aerobatic and spin recovery training and approvals unless a student had already obtained a licence through the school. The instructor who signed the pilot’s logbook endorsements for wingovers, aileron rolls, and spin recovery held the appropriate Civil Aviation Safety Authority (CASA) qualifications to do so.
Aircraft information
General
The aircraft, a de Havilland Canada DHC-1 T Mk 10 Chipmunk, was built in the United Kingdom (UK) in 1950 with the constructor’s number C1/0111. It was first registered as a civilian aircraft in Australia in 1956 (Figure 1).
The Chipmunk was designed for ab initio military flight training. It is a two-seat, low-wing, single engine aircraft with a mainly light aluminium alloy sheet airframe and fabric covered wings and control surfaces. The aircraft was powered by a de Havilland Gipsy Major 10 Mk 2 four cylinder piston engine driving a two-blade wooden Hoffman H0.21198B/140L fixed-pitch propeller.
The ATSB assessed that the aircraft was within its weight and centre of gravity limits at the time of the accident, with the centre of gravity towards the rear limit.
Figure 1: DHC-1 Chipmunk, registered VH-UPD, in 2009
Source: Recreational Pilots
Maintenance
A current maintenance release was not carried in the aircraft and was later provided to the ATSB by the owner. It recorded that the aircraft’s most recent inspection was completed on 26 June 2014 at 5,129.25 hours time in service, with no outstanding defects.
Wreckage and impact information
The accident site was located about 400 m east of the Coffs Harbour Regional Airport runway 03[3] threshold (Figure 2).
The main wreckage was in an upright position, oriented towards the east (Figure 3). The damage to the aircraft and impact marks on the surrounding foliage and the ground indicated that the aircraft impacted terrain in a near vertical descent while yawing from left to right and in a slightly nose-low attitude. The fuselage and undercarriage absorbed much of the ground impact forces, as did the foliage and relatively soft, sandy ground.
All of the aircraft components were accounted for in the immediate area of the accident site. There was no evidence of any pre-impact failure.
Flight control continuity was established. The flaps appeared to be retracted at the time of impact. The elevator trim position could not be accurately determined due to the structural deformation of the fuselage.
A loose washer was found in an area behind the rear control box. Visual examination of the washer revealed no damage that would indicate that it had been jammed in the controls.
Both fuel tanks were compromised and there was a strong smell of fuel in the area underneath the tanks, indicating that fuel had drained from the tanks into the ground. The carburettor bowl was drained of about 80 mL of fuel, which was free from water and visible debris and had the appearance and smell of aviation gasoline.
Propeller damage was indicative of rotation without significant power. A limited on-site examination found that the engine rotated freely with good compression on the two undamaged rear cylinders and spark plugs indicating normal combustion. There was no evidence of oil contamination or oil leaks.
Figure 2: VH-UPD accident site location
Source: Google earth, modified by the ATSB
Figure 3: VH-UPD accident site
Source: ATSB
Survivability
The pilot sustained serious head, pelvic and leg injuries requiring hospitalisation. The passenger had a compressive back injury requiring hospitalisation. Both occupants were wearing four-point harnesses, which were reported to be fastened securely. Neither occupant was wearing a helmet.
ATSB analysis based on estimates of aircraft speed and rate of descent, impact angle, and energy absorption indicated that the impact forces imparted to the occupants would normally be expected to result in moderate to serious injuries.
Weather information
An automatic terminal information system (ATIS)[4] report for Coffs Harbour Airport at 1039 indicated a north-easterly wind at 5 kt, more than 10km visibility and few[5] cloud at 5,000 ft. At 1116, as part of normal air traffic communications, the air traffic controller informed the pilot that the surface wind was 8 kt from 100 °M.
Spins and spin recovery
Overview
An aerodynamic spin is a sustained spiral descent in which an aircraft’s wings are in a stalled condition,[6] with the outer wing producing more lift and less drag than the other wing. The associated forces sustain the rotation and keep the aircraft in the spin. A spinning aircraft will descend more slowly than one in a vertical dive and it will have a low airspeed, which may oscillate. The pitch angle can also vary considerably.
Intentional spins are normally entered from a stall in straight and level flight, and the application of full back elevator and full rudder in the intended direction of rotation at the moment of stall. The circumstances of a spin entry near the top of a loop may be very different. If a loop is not carried out correctly, the aeroplane can flick-roll[7] or stall at the top of the loop and, if not in balanced flight, may enter an upright spin.
When entering a spin, an aircraft’s motion through the air is irregular at first. This is known as the incipient phase of the spin. Though the nature of the incipient spin is heavily dependent on the aircraft type and the manner of entry, recovery may be more rapid and require less control input in this stage compared with recovery from a developed spin.
After a number of rotations and depending on the aircraft type, loading, and control inputs, an aircraft in an incipient spin may then settle into a regular rotating descent, known as a developed spin. A spin may steepen (nose down) or flatten (nose more horizontal) as it continues, potentially requiring different recovery techniques. Flight test reports indicate that a Chipmunk that enters a spin from a straight and level stall normally takes about three full rotations to enter a fully developed spin.
CASA Civil Aviation Advisory Publication (CAAP) 155-1(0) outlines the following standard spin recovery method, which ‘should be applicable in most situations and aircraft, but the procedure specified in the aircraft's flight manual is the ultimate authority’:
Close throttle;
Centralise ailerons;
Identify if the aircraft is spinning, the direction, and whether upright or inverted;
Full rudder opposite to rotation (opposite to yaw);
Pause;
Elevator forward [nose down] for upright and back for inverted as required to unstall;
When rotation stops - centralise rudder;
Roll wings level and recover to level flight.
With regard to elevator input in an upright spin, Stowell (2007) recommends pushing the elevator control forward using whatever force is necessary until either the spin stops (which may occur with the control stick between fully aft and neutral in aerobatic designs) or the forward control limit is reached.[8] Some publications recommend letting go of the control column, especially if the pilot is unsure whether the spin is upright or inverted, but in some aircraft types this may not result in recovery.
Chipmunk spins and recovery
The UK Civil Aviation Authority (UK CAA), Civil Aircraft Airworthiness Information and Procedures CAP 562 dated 29 November 2013, Leaflet B-250, Chipmunk Spinning and Aerobatics[9] gave the following instructions to recover from a spin in a Chipmunk:
Spin Recovery must be started at least 3,500 feet above ground level, in order to retain level flight by 1,500 feet, consistent with a height loss during recovery of up to 2,000 feet.
a) check throttle CLOSED;
b) check ailerons CENTRAL;
c) apply full OPPOSITE RUDDER;
d) PAUSE;
e) move the stick firmly FORWARD against the increasing stick force and stick buffet, IF NECESSARY TO THE FRONT STOP and hold it there until rotation ceases;
f) when rotation ceases CENTRALISE the rudder control and ease out of the ensuing dive.
In June 1960 the Australian Department of Civil Aviation (DCA)[10] published a report that addressed contemporary concerns about the behaviour of the Chipmunk during spin recovery (refer Appendix A – Aviation Safety Digest No.22 extract – The CHIPMUNK SPIN THE FACTS). The report stated that ‘the point at which pressure is felt in the forward travel of the stick varied considerably and is occasionally almost at the fully forward position’ and could be heavy or light.
The ATSB reviewed several documents dating from 1958 onwards, including flight test reports and correspondence between UK authorities and the aircraft manufacturer and type design organisation. These documents addressed the spin and spin recovery behaviour of the Chipmunk. Collectively, the evidence indicated that Chipmunks always recovered from spins using the UK CAA-suggested recovery method described above.
The documents reviewed by the ATSB were consistent in their emphasis on the importance of forward stick movement, with more force than is normally used, and in maintaining full opposite rudder and increasing forward stick (up to the stop if necessary) until rotation ceases. This could take between one and four and a half turns after the application of correct control inputs. Stowell (2007) stated that ‘it is vital, therefore, to maintain spin recovery inputs for as long as is needed throughout the entire recovery process; otherwise, recovery could be delayed even longer.’
The training material used by the flying school did not contain spin recovery advice specific to the Chipmunk aircraft type. With regard to elevator control position, the ‘standard’ spin recovery method provided by the flying school’s training material did not emphasise the need for forward control stick movement against the control force (as opposed to neutrally forward from the rearward position).
Chipmunk semi-stalled spiral dive
A Chipmunk may enter a state known as the ‘semi-stalled spiral dive’ that may be confused with the spin. In this case, the aircraft’s attitude is steeply nose-down, with higher airspeed and, according to UK CAA Leaflet B-250, ‘upon releasing the controls the aeroplane will recover by itself, or with some opposite rudder, after rotating through one quarter to one half [of] a turn.’
The Australian DCA 1960 report stated that, in most cases, the aircraft will first spiral from the stall and that two or three turns may result before the spin proper is entered. The report stressed the need to differentiate between the semi-stalled spiral dive and the spin and emphasised the importance of using correct recovery procedures in each case.
A 1958 flight test report by the aircraft manufacturer stated that:
Recovery from the spiral dive is easy and quick whereas recovery from a spin requires deliberate and positive control for a longer time. Anti-spiral dive control will not result in recovery from a spin. When pilots, who have been used to spiral dives, find themselves in a spin they tend either not to apply adequate anti spin control or not to persist with the correct control movements for long enough.
Anti-spin strakes
The Chipmunk could be fitted with strakes on the rear fuselage that were intended to aid the recovery of the spin. According to the 1958 report, the strakes produce a ‘small but definite improvement in spin recovery’ but do not affect the aircraft’s ability to enter a spin. Despite this, they were commonly referred to as ‘anti-spin strakes.’
For UK-registered aircraft, an airworthiness directive[11] mandated fitment of strakes for aircraft approved for aerobatic manoeuvres and spins, along with a placard advising that ‘SPIN RECOVERY MAY NEED FULL FORWARD STICK UNTIL ROTATION STOPS’. Aircraft without strakes were required to display a placard stating ‘AEROBATICS AND SPINS PROHIBITED’.
In Australia, neither strakes nor related placards were mandated through an airworthiness directive; however, the strakes and placards were a requirement in accordance with the appropriate Australian flight manual (see Aircraft flight manuals for the DHC-1 Chipmunk). UPD and the other Chipmunk aircraft that the pilot flew were not fitted with anti-spin strakes.
Aircraft flight manuals for the DHC-1 Chipmunk
Aircraft flight manual for VH-UPD
The accident aircraft was a DHC-1 T Mk 10, a military variant, which was not issued with a civil type certificate[12] and, originally, had no civil aircraft flight manual (AFM).[13]
In Australia prior to 2002, CASA and its predecessors prepared, approved and issued AFMs for light civil aircraft. The flight manual in use for UPD was one such manual, approved specifically for that aircraft by CASA’s predecessor in 1988. It did not include guidance on spin recovery. It permitted any combination of various manoeuvres including spins and inside loops.
In 2002, changes to Australian regulations meant that aircraft owners needed to replace any flight manuals prepared by CASA, or its predecessors, with a type design organisation-approved flight manual. Until that date, the Chipmunk type design organisation had not produced, and had not been required to produce, a flight manual for civil operation of the military T Mk 10 variant. The type design organisation satisfied the CASA requirement and produced a flight manual for that aircraft type for use in Australia only. It included specific precautions for the operation of ‘Aircraft NOT Fitted with Anti-spin Strakes’. CASA advised that operators of civil T Mk 10 aircraft were required to use the 2002 flight manual.
According to the aircraft type design organisation, the owner of UPD did not purchase the newer flight manual. CASA records indicated that the aircraft’s owner made an application for approval of the 1988 flight manual in 2002. A subsequent letter from CASA advised the owner of ‘approval of the aircraft manufacturer’s flight manual for VH-UPD’; the accompanying approval form gave the reference number of a 2002 flight manual (see the next section), not the older flight manual. Records held by CASA did not contain evidence that the Civil Aviation Authority (Australian CAA)[14] produced AFM, dated 1988, had been approved as the aircraft’s AFM in 2002.
Aircraft type design organisation’s flight manual
The type design organisation’s 2002 generic[15] aircraft flight manual produced specifically for Australian-registered T Mk10 Chipmunks contained more information than the 1988 flight manual, including type-specific handling techniques that were not required under the CASA regulations. On spin recovery, it provided similar advice to the Leaflet B250 (see the section titled Spins and spin recovery).
The flight manual also stated that all civil Chipmunks cleared for aerobatics must display a cockpit placard with the following information: ‘SPIN RECOVERY MAY NEED FULL FORWARD STICK UNTIL ROTATION STOPS (also see Flight Manual)’. Aircraft not cleared for spins and aerobatics were required by the type design organisation’s flight manual to display a placard prohibiting aerobatics and spins.
Training aircraft
A flight manual for the Chipmunk used by the pilot’s flying school was a reprint of a 1966 UK military flight manual and was not specifically approved for, or tailored to, the flying school’s Chipmunk. On spin recovery, it gave similar advice to the Leaflet B-250 (see the section titled Spins and spin recovery).
An ‘aircraft information booklet’ (not an approved flight manual) for the Chipmunk that was used by the flying school recommended a loop entry speed of 130 kt.
Prior to publication of this ATSB report, the flying school ceased using the Chipmunk for flying training.
Related occurrences
The first fatal spin accident in a Chipmunk in Australia occurred on 19 January 1957 near Goulburn, New South Wales, and the reasons for the accident were not determined. After this accident and three other fatal Chipmunk spin accidents (in 1959 and 1960) for which the reasons were not determined, the Australian DCA conducted a detailed set of test flights to determine whether the Australian Chipmunk had suitable spin recovery handling characteristics. The results were disseminated in the 1960 DCA report discussed previously (see the section titled Chipmunk spins and recovery).
There were four other spin-related accidents involving Chipmunk aircraft in Australia between 1961 and 1968. While the last accident in January 1968 involved spin training, this accident was due a coin obstructing the elevator control system, which deprived the pilot of the elevator movement necessary to recover from the spin.
There were no other reported spin-related accidents involving Chipmunk aircraft in Australia between 1969 and 2014.
Based on the pilot, passenger, and witness reports, the aircraft stalled at or near the top of an attempted loop, rolled upright and entered an upright spin that then became flatter. The pilot’s control inputs are not known with certainty, but the stall was most likely initiated by too much elevator (stick back) control input for the aircraft’s relatively low speed at the top of the loop.
If an aircraft’s speed is too low when approaching the top of a loop, a pilot can mistakenly apply too much elevator (stick back) control when trying to correct for the low speed. The subsequent increased angle of attack could then produce a stall. There can be several reasons for a low airspeed at the top of a loop, such as:
low entry speed
insufficient throttle increase during the first part of the loop
too little g[16] throughout the loop, increasing the loop circumference and resulting in excessive altitude gain
too much g load throughout the loop, producing increased induced drag.
A single-propeller aircraft in a powered stall would be expected to roll. The direction of UPD’s roll and spin was consistent with its natural tendency to roll and spin to the right (opposite to the direction of propeller rotation) in a positive-g, inverted stall. Control authority would have been greatly reduced by the low airspeed and any excessive application of aileron or rudder would have increased the risk of the roll developing into a spin.
The pilot reported receiving training to conduct loops and thought that he held the appropriate endorsement to do so as pilot-in-command, but did not have documentary evidence of it. The pilot’s instructors reported that the pilot had not yet demonstrated the required skills to be endorsed to conduct loops as pilot-in-command. This indicated that the pilot had not demonstrated the necessary competence required to perform a loop consistently or execute a recovery from an unsuccessful loop.
Unsuccessful spin recovery
According to the results of numerous flight tests, a Chipmunk can be recovered from a spin if there is sufficient recovery height available, and the ATSB estimated that the aircraft had enough height for a successful recovery in this case. Both UPD and the flying school’s Chipmunk were used for aerobatic flight without being fitted with anti-spin strakes. According to most reports, a Chipmunk without strakes will recover from a spin but somewhat more slowly than one fitted with that capability. If anti-spin strakes had been installed on UPD, they may have assisted a recovery if the correct flight control inputs were made and held for a sufficient length of time. Additionally, the Chipmunk T Mk 10 (Australia Only) flight manual specifies greater heights above ground level for spinning manoeuvres.
The pilot later reported that, at the time, he recognised that the aircraft was in a spin but did not have a complete recollection of how he attempted to recover from the spin. It was not possible to conclusively determine why the recovery attempts were unsuccessful but it is likely that correct control inputs (particularly opposite rudder and progressively forward control stick) were not made, or not held for long enough to be effective. However, there are a number of factors which probably had an influence.
The method of spin recovery taught by the pilot’s flight instructor, and practised by the pilot during training, was to apply opposite rudder and approximately central control stick. The application of central control stick allows recovery in some Chipmunks, particularly from an incipient spin or semi-stalled spiral dive. It also works for some newer aircraft types that are designed to exhibit more benign spin behaviour. However, it does not work for all Chipmunks, especially once a spin has fully developed. The method of spin recovery described by the pilot would probably have been ineffective once the spin was fully developed. The aircraft also might have entered a fully-developed spin more rapidly than during the pilot’s training because of the unusual manner of entry, or as the result of weight and aerodynamic differences between it and the training aircraft.
To recover from a fully-developed spin in a Chipmunk, it is important to push the control stick forward – fully forward if necessary – after applying full opposite rudder. The pilot’s training apparently did not emphasise full forward movement of the stick against any resistive control force, a degree of movement that was recommended by the aircraft type design organisation for this particular aircraft type. It is also possible that, in attempting to apply central control stick, the pilot unwittingly held a more rearward stick position than intended due to the control forces. This is a hazard highlighted by the 1960 Australian Department of Civil Aviation flight test report, which stated:
Frequently the resistance encountered as the stick moves forward will be high and this could be confused with the stick having reached the forward limit of travel. A conscious effort is necessary to avoid this confusion.
Finally, it is uncertain whether the pilot actually applied positive spin recovery control properly, or for long enough for it to be effective. The pilot learned about spin recovery under controlled and relatively predictable conditions, as well as receiving a pre-flight briefing and discussion regarding the spin training flight. In these circumstances, the spin entry is relatively smooth, consistent and expected. In contrast, about a year after having learned and practised how to manage spins (only to the left), the pilot encountered an unexpected spin to the right from an attempted loop. This can be disorienting and slow the identification of the problem and application of the correct control inputs, especially if the responses were not recently practiced. Infrequently used knowledge and infrequently practiced skills degrade over time, and in an emergency the ability to recall them rapidly and accurately is generally impeded further. Regularly reviewing important knowledge and skills, particularly as part of self-briefing prior to a flight, may facilitate a more rapid and accurate recall ‘in the heat of the moment’.
Instructor training
The pilot’s flight instructor taught and used a method for Chipmunk spin recovery that was reasonably effective in the early stages of a spin, but would become less effective as the spin developed. It was different to the standard method of spin recovery recommended by the Civil Aviation Safety Authority, and to the Chipmunk-specific method recommended by the type design organisation. The flying school’s training materials did not include Chipmunk-specific spin recovery methods, and did not clearly emphasise the forward control stick movement necessary for some aircraft.
Civil Aviation Order 40.0 stated that a flight instructor must be ‘…satisfied that the holder can safely recover an aeroplane from a fully developed upright spin’ (emphasis added), but the pilot was taught to recover from an early-stage and possibly incipient spin rather than when fully developed. Although modern aircraft may recover from a spin using less than optimal control inputs, it is important to teach and demonstrate competence in recovering from spins in the manner most appropriate to the aircraft type that the student pilot intends to fly, especially if aerobatic manoeuvres are planned.
The instructor’s objective of using a more central elevator position was to put the control stick in a position that would allow a stalled aircraft to un-stall, as described in Civil Aviation Advisory Publication 155-1(0). That is:
The fore and aft position of the control column determines the angle of the aircraft's wings to the airflow. For example, the stick positions for cruise, glide and the stall move progressively aft. Once the stick position for the stall has been determined (and remembered), it can be used as a measure of whether an aircraft's wing is stalled or not. If the stick is forward of the 'stalled stick position', the aircraft will always be in unstalled flight, regardless of aircraft attitude or airspeed.
While this concept may be correct under most conditions, it is not generally the case in situations such as a spin, where elevator authority is reduced and rotational forces become significant. As stated elsewhere in the advisory publication, it is important to use the aircraft’s approved documentation as the primary and most reliable source of information.
Aircraft documentation
The Civil Aviation Safety Authority advised that the flight manual originally produced by the aircraft type design organisation in 2002 was the only currently approved manual for the T Mk 10 Chipmunk in Australia. Records show that the aircraft’s flight manual approval lapsed in 2002 and that the newer flight manual was not obtained by the owner. Consequently, pilots of UPD were using information that was out of date. Although there was no requirement for spin recovery guidance to be included, the approved flight manual provided by the aircraft type design organisation did include such guidance and would have provided a reliable source of valuable information for the pilots of UPD to follow.
The flying school had a different flight manual for its Chipmunk aircraft, which was also not approved. Although that flight manual contained generally appropriate spin recovery advice, it did not incorporate the latest approved information. There are variations between aircraft of the same type, often due to modifications and repairs, and using an unapproved flight manual increases the risk that the information within it is not appropriate for that particular aircraft.
From the evidence available, the following findings are made with respect to the collision with terrain involving de Havilland Canada DHC-1 Chipmunk, registered VH-UPD, that occurred at Coffs Harbour, New South Wales, on 29 June 2014. These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Safety issues, or system problems, are highlighted in bold to emphasise their importance. A safety issue is an event or condition that increases safety risk and (a) can reasonably be regarded as having the potential to adversely affect the safety of future operations, and (b) is a characteristic of an organisation or a system, rather than a characteristic of a specific individual, or characteristic of an operating environment at a specific point in time.
Contributing factors
The pilot attempted to conduct a loop without the required qualification.
The aircraft entered an upright spin after a stall or flick-roll at the top of an attempted loop.
The pilot probably did not apply and maintain the spin recovery control inputs appropriate for a fully developed spin in a Chipmunk, and the spin continued until impact with terrain.
Other factors that increased risk
The flight instructor who taught the pilot spin recovery did not teach the method to recover from a developed spin that was appropriate for the aircraft type.
The spin recovery methods taught by the flying school were inconsistent across instructors and training material, and were not always appropriate for the Chipmunk aircraft type used by the school. [Safety Issue]
The approval for the accident aircraft’s flight manual had been revoked, and the flight manual in use lacked the spin recovery instructions that would have been present in a flight manual issued by the aircraft type design organisation.
The flying school’s Chipmunk aircraft was used for aerobatic instruction and endorsement without having a current, approved flight manual that contained spin recovery instructions.
Safety issues and actions
The safety issues identified during this investigation are listed in the Findings and Safety issues and actions sections of this report. The ATSB expects that all safety issues identified by the investigation should be addressed by the relevant organisation(s). In addressing those issues, the ATSB prefers to encourage relevant organisation(s) to proactively initiate safety action, rather than to issue formal safety recommendations or safety advisory notices.
All of the directly involved parties were provided with a draft report and invited to provide submissions. As part of that process, each organisation was asked to communicate what safety actions, if any, they had carried out or were planning to carry out in relation to each safety issue relevant to their organisation.
The initial public version of these safety issues and actions are repeated separately on the ATSB website to facilitate monitoring by interested parties. Where relevant the safety issues and actions will be updated on the ATSB website as information comes to hand.
Flying school spin recovery training
The spin recovery methods taught by the flying school were inconsistent across instructors and training material, and were not always appropriate for the Chipmunk aircraft type used by the school.
The sources of information during the investigation included:
the pilot and passenger
the flying school and instructors
the aircraft owner
the air traffic controller
air traffic recordings
a number of witnesses
de Havilland Support Limited (type design organisation)
Civil Aviation Safety Authority (CASA)
the Bureau of Meteorology.
References
United Kingdom Civil Aviation Authority. (2013) CAP 562 Civil Aircraft Airworthiness Information and Procedures, Leaflet B-250, Chipmunk Spinning and Aerobatics.
Stowell, R (2007). The Light Airplane Pilot's Guide to Stall/spin Awareness: Featuring the PARE Spin Recovery Checklist. Rich Stowell Consulting Ventura.
Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.
A draft of this report was provided to the pilot, aircraft owner, United Kingdom Air Accidents Investigation Branch, type design organisation, flying school and CASA.
Submissions were received from the United Kingdom Air Accidents Investigation Branch, type design organisation and CASA. The submissions were reviewed and where considered appropriate, the text of the report was amended accordingly.
Appendices
Appendix A – Aviation Safety Digest No.22 extract
Purpose of safety investigations & publishing information
Purpose of safety investigations
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
Occurrence summary
Investigation number
AO-2014-114
Occurrence date
29/06/2014
Location
Coffs Harbour Airport, SE 1 km
State
New South Wales
Report release date
04/02/2016
Report status
Final
Investigation level
Defined
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
The pilot of a Bell 206 helicopter, registered VH-NKW, was tasked to drop equipment bags for seismic operations by using a magnetic bag runner connected to the helicopter by a 100 ft long-line.
The helicopter lifted off with seven bags loaded on the runner. During the flight of about 2 NM, the pilot observed that the bag lanyards became tangled. The pilot manoeuvred the bags onto the ground and using dual switches on the cyclic control, released the two solenoids to drop the first bag. The lanyard was tangled around the others and the released bag remained hanging and entangled with the other bags. The pilot then released the second bag and attempted to make the bags drop. He then repeated this for six bags and eventually one bag remained connected to the runner with the other bags entangled and hanging from it.
The pilot elected to land the helicopter to untangle the bags. He manoeuvred the helicopter backwards down the slope to land on a more suitable site. When about 10 ft above the ground, the pilot manoeuvred slightly further to the right however the long-line became fully extended. As the line pulled taut it came directly out the left side of the helicopter from under the centre of the left skid. This caused the helicopter to roll to the right.
The main rotor blade collided with the ground before the pilot reached the long-line release switch. The helicopter rolled over and came to rest inverted, resulting in substantial damage.
This incident demonstrates the importance of using equipment in accordance with established best practice. The operator advised that the bag runner is no longer to be used for bag layout operations; it is only to be used for bag retrieval/pick-up.
On 17 June, 2014 a PA28RT-201, Piper Arrow aircraft registered VH-ADU was returning to Mangalore Airport, Victoria for the final leg of a dual navigation exercise.
The straight in approach onto runway 18 went as planned, although there was some turbulence from a line of trees, late on the approach.
During the flare the aircraft ballooned, and the instructor called ‘taking over’. The student relinquished his control prior to the instructor gaining full control of the aircraft. The incorrectly trimmed aircraft rapidly dropped its nose. The instructor used a great deal of force in an attempt to bring the nose back into the landing position. Just as he got the nose level, the aircraft landed heavily on all three wheels.
The aircraft bounced so the instructor initiated a go-around. The student, flew part of the circuit, but was apprehensive about landing. The aircraft again ballooned in the flare. The instructor took control and landed without incident.
The United States Department of Transportation, Federal Aviation Administration Aviation Instructor’s Handbook 2008 (p 8-9) devotes a section to the Positive Exchange of Flight Controls.
This publication states that numerous accidents have occurred due to a lack of communication or misunderstanding regarding who had actual control of the aircraft, particularly between students and flight instructors. It goes on to say that during flight training, there must always be a clear understanding between students and flight instructors about who has control of the aircraft.
The Civil Aviation Safety Authority (CASA) Flight Instructor Manual (2) (2007)– Aeroplane, directs instructors to repeatedly practice the “handing over and taking over” drills, in the early air sequences, to prevent any confusion on who is manipulating the controls.
The CASA Flight Instructor Manual is available at:
On 26 May 2014, a Virgin Australia Boeing 737 aircraft, registered VH-YIR, was being loaded at Bali International Airport for a flight to Melbourne, Victoria. The flight had been delayed due to a series of disruptions following the cancellation of the previous day’s flight to Melbourne. A breakdown of the baggage belt at Bali airport exacerbated the difficulty in loading and reconciling passenger baggage. A scheduled airport curfew created time pressure for the ground staff who had to manually re-tag bags on the airport apron.
The load controller assessed that a total of 93 bags had been loaded onto the aircraft and the flight documents were produced using that figure. About 30 minutes after the aircraft departed Bali, the ground handler advised network operations and load control that the final baggage numbers were incorrect. The total number of bags loaded onto the aircraft was 189 instead of 93, with an estimated additional weight of about 1,600 kg. The load control team leader elected not to advise the flight crew of the discrepancy.
It was later determined that, based on estimates, the aircraft remained within the weight and balance limitations throughout the flight and the additional weight would have had a negligible effect on the aircraft’s take-off performance.
On 15 June 2014, a Virgin Australia Airbus A330 aircraft, registered VH-XFE, was being loaded for a flight from Perth, Western Australia, to Brisbane, Queensland. The load coordinator printed and distributed the outbound load instructions, on which no outbound items were allocated to the forward hold, but omitted to print the inbound load instructions. The forward hold was not opened or inspected at any time while the aircraft was on the apron at Perth Airport.
The flight departed at about 2245 Western Standard Time and landed in Brisbane without incident. The flight crew were not aware of any loading or weight and balance issues during the flight. During offloading, ground staff at Brisbane Airport found a crate of freight weighing 1,467 kg in the forward hold that had not been manifested and was supposed to have been offloaded in Perth prior to departure.
Accurate weight and balance information is essential for the safety of every flight. These incidents demonstrate the impact distractions such as time pressure and equipment malfunction can have on the accuracy of that information. Following standard procedures and checklists may minimise the potential for error.
On 10 June 2014, a Boeing 737 aircraft, registered ZK-ZQB and operated by Jetconnect Limited landed at Sydney Airport, New South Wales. During taxiing, the crew felt a slight shuddering from around the main landing gear; they also observed that they required a higher-than-normal thrust to taxi the aircraft. At the crew’s request, personnel in the Air Traffic Control tower and a passing aircraft observed ZK-ZQB, but did not see anything abnormal. The crew then requested that Rescue and Fire Fighting Services conduct a close-up inspection. They advised the crew that pieces of metal had fallen onto the runway and that the right, outer main wheel was leaning over. After parking the aircraft, an examination by Licenced Aircraft Maintenance Engineers confirmed that the inboard wheel half-hub had fractured into several pieces and that the wheel bearings were intact.
Inboard wheel half remnant
Source: Aircraft operator
Wheel hub failure
The wheel hub consisted of an inboard and outboard section (Figure 1).The inboard wheel half on ZK-ZQB was part number 2612462 and serial number B3902.
Figure 1: Schematic diagram of wheel hub with the failure location circled
Source: Honeywell
After removal of the bearing cup, the aircraft operator inspected the bore and reported that there was no sign of bearing cup rotation. A visual inspection of the fracture surfaces was then performed by the operator’s maintenance organisation that indicated the origin of the failure to most likely be in the area of the bearing bore radius (Figures 2a and b). However, that area had been damaged, following the final fracture. From the point of origin, a series of cracks grew both axially (Figure 2b) and circumferentially around the inboard hub (Figure 3). In the axial direction, chevrons on the fracture surface radiated from the radius area. Circumferential crack growth occurred partly by joining a series of smaller, tertiary cracks on the hub’s outer diameter. The surfaces of that circumferential crack showed the joining process as a series of ratchet marks. This earlier part of that fracture surface was burnished as the two faces of the crack had rubbed together over a period of time, obliterating some detail. The crack then became a singular front with beach marks, an indicator of fatigue cracking. The area of ultimate failure changed from fatigue to the more rapid, overload mode.
The wheel manufacturer also examined the failure. They concluded it was likely that the fatigue crack initiated in the stress-concentrated, transition region between the bearing bore wall and the circumferential radius. Ultrasonic testing of this area detected possible small fatigue cracks or origins.
Figures 2a and b: Fractured hub from the inboard wheel half and chevrons leading from the damaged, radius-area origin; the arrow shows the direction of crack growth from that area
Source: Aircraft operator
Figure 3: Secondary, circumferential crack showing, from left to right, the damaged origin area, ratchet marks/burnishing, beach marks and ultimate failure by overload
Source: Aircraft operator
Related manufacturer’s and operator’s service information
Due to previous failures of the wheel hub, service bulletins and requirements for inspection were issued by the aircraft and wheel manufacturers. These included a Boeing Service Letter,[1] which indicated that there was a known failure mode of the wheel hub, which was related to a loose or spinning bearing cup in the hub bore. As noted earlier, inspection of the bore, post-cup removal, found no indication of bearing cup rotation. The Boeing Fleet Team Digest[2] noted that failures could also occur from fatigue initiating in the bearing bore radius area (as was the case in ZK-ZQB); however, those failures had primarily occurred in the redesigned wheel hubs that superseded the 2612462 part number i.e. from PN 2615480.
In 2010, Boeing also issued a Special Attention Service Bulletin[3] covering 737 wheel failures. That bulletin recommended ultrasonic inspection, in accordance with the wheel manufacturer’s service bulletin[4], of relevant part and serial numbers, whenever a wheel was removed from the aircraft. For part number 2612462, the wheel manufacturer recommended non-destructive testing (NDT) at each overhaul interval. In ZQB’s case, this averaged approximately 180 landing cycles per interval. That inspection required[5] visual examination of each component, measurement of specific parts/areas and ultrasonic inspection of the hub outer diameter of both wheel halves to detect bearing-bore cracks at every tyre change and wheel overhaul. However, if the bearing cup had been removed, other NDT methods (eddy current, ultrasound or fluorescent penetrant inspection (FPI)) were to be used to inspect the bearing bore’s internal diameter and corner radius. The component maintenance manual also noted that visual inspection of the wheel halves was to investigate for damage to paint or corrosion-protection coatings, as stress concentrators in corrosion could also initiate fatigue cracking.
In summary, note that for PN 2615480, serial number (SN) B15418 and prior and SN H0483 and prior wheel halves, mandatory annual NDT inspection was required. For PN 2612462 and PN 2615480, SN B15418 and above and SN H0483 and above wheel halves, compliance with the NDT recommendation was optional.
Maintenance
Examination of the maintenance records, from the 15 months before the inboard wheel-half failure, found that the wheel manufacturer’s recommended inspections had been performed whenever the wheel had been removed from the aircraft. Although the March 2013 major service specified non-removal of the bearing cup and, consequently, ultrasonic inspection, all services since then used eddy current inspection. The wheel manufacturer’s service bulletin specified that such a test could only be done if the bearing cup and sleeve assembly had been removed. No discrepancies were reported for the visual, ultrasonic, eddy current and FPI methods used as part of these inspections. The most recent record that included landing cycle data (February 2014), noted that 84 cycles had occurred in the two months since the last service (December 2013) and that the total time since new (TSN)/ time since overhaul (TSO) hours were 22901/1803 respectively. In March 2013, a major service was carried out and the tie bolt hole radii were shot peened. This shot peening was restricted to this area and did not include the bearing bore radius.[6]
Safety action
The ATSB was advised by the aircraft operator that they are upgrading their fleet with carbon brakes from a different manufacturer. As a result, all current main wheel assemblies will be replaced with wheels from that manufacturer; hence, those wheels will have a different part number. The modification program of fitment with new wheels and brakes commenced in February 2015 and will be completed by the end of May 2015.
The objective of a safety investigation is to enhance transport safety. This is done through:
identifying safety issues and facilitating safety action to address those issues
providing information about occurrences and their associated safety factors to facilitate learning within the transport industry.
It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action.
Terminology
An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue.
Publishing information
Released in accordance with section 25 of the Transport Safety Investigation Act 2003
Ownership of intellectual property rights in this publication
Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia.
Creative Commons licence
With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence.
Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work.
The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau
Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.
On 5 June 2014, the pilot of a Beechcraft 200 aircraft, registered VH-NMW, conducted a private flight from Narrabri to Sydney Airport, New South Wales, with two passengers on board.
During the cruise, the pilot entered the arrival and approach into the flight management computer. The pilot was advised by air traffic control (ATC) to expect an instrument landing system (ILS) approach to runway 16 Left (16 L).
The pilot was cleared by air traffic control (ATC) to descend to 3,000 ft and while on descent, was given radar vectors to intercept the localiser for runway 16 L. The pilot selected approach (‘APP’) mode on the flight guidance panel (FGP) and confirmed that the aircraft had intercepted the localiser. About 2 minutes later, the aircraft was cleared for the instrument landing system (ILS) approach on 16 L however the pilot did not observe that at this stage, the aircraft was below the glideslope.
The pilot was then temporarily distracted by explaining the multi-function display to the passenger seated in the front right seat. The controller queried whether the aircraft was on the glideslope and the pilot realised that the aircraft was below the glideslope. The aircraft then maintained the current altitude until intercepting the glideslope. Prior to intercepting the glideslope, ATC advised the pilot that the aircraft was at 1,500 ft and below the lowest safe altitude. As the aircraft was established on the localiser and about 8 NM from the runway, the applicable minimum altitude was 1,700 ft AMSL.
This incident highlights the importance of continuously monitoring aircraft and approach parameters and the impact distractions can have on maintaining a stable approach profile.
At 2245 on 5 June 2014, the crew on Pacific National (PN) coal service ER64 reported that flames were emanating from the top of the fourth locomotive, 8221, on their train. At the time, ER64 was near Awaba in New South Wales enroute to unload at the Eraring power station. The crew stopped the train and assessed the extent of the fire while also calling for fire brigade assistance. The fire was declared extinguished at 0139 on 6 June 2014. It caused substantial damage to the locomotive.
There were no reported injuries as a result of the incident.
What the ATSB found
The ATSB found that the fire was most likely caused when the clevis clamping one of the fuel sight glasses to the fuel filter assembly disengaged, allowing fuel under pressure to spray throughout the engine bay and ignite probably on either the hot exhaust manifold or from within the main generator. The sight glass assembly disengaged because its clevis had compressed, bending inwards, and allowing sufficient lateral movement for it to release from the clevis bolts in the sight glass aperture. The procedures for locomotive inspection and maintenance were not effective at identifying and addressing continuing fuel leakage problems on this type of fuel filter assembly.
What's been done as a result
Pacific National informed the ATSB that an immediate inspection of all locomotives fitted with the sight glass arrangement was conducted to ensure clevis assemblies conform to original equipment manufacturer specifications and requirements. It also informed the ATSB that an amendment was made to current maintenance procedures increasing the inspection requirements for the sight glass assembly including the clevis and clevis bolts.
Safety message
This incident illustrates the importance for locomotive maintainers to maintain vigilance and ensure adherence to current maintenance procedures when conducting maintenance on locomotive fuel systems to minimise the risk of fuel leakage and consequent potential for fire.
