SF34, Canberra Australia, 2022

SF34, Canberra Australia, 2022

Summary

On 10 November 2022, a De Havilland Canada DHC8-200 started engines with the left engine propeller restraint strap attached and as it became airborne from Sydney, the strap was thrown free from the propeller, impacted the fuselage and the associated securing pins penetrated the fuselage, one injuring a passenger. The aircraft returned. The Investigation attributed the occurrence to a comprehensive failure of both pilots to follow relevant standard operating procedures within a context of regular related procedural non-compliance. The operator’s failure to properly involve their contracted airport handling agent in effective management of operational safety matters was also noted.

Event Details
When
10/11/2022
Event Type
GND, HF
Day/Night
Day
Flight Conditions
On Ground - Normal Visibility
Flight Details
Aircraft
Type of Flight
Public Transport (Passenger)
Intended Destination
Actual Destination
Take-off Commenced
Yes
Flight Airborne
Yes
Phase of Flight
Take Off
Location - Airport
Airport
General
Tag(s)
Copilot less than 500 hours on Type, Inadequate Aircraft Operator Procedures
HF
Tag(s)
Flight / Cabin Crew Co-operation, Flight Crew / Ground Crew Co-operation, Flight Crew Visual Inspection, Procedural non compliance
GND
Tag(s)
Ramp crew procedures
Outcome
Damage or injury
Yes
Aircraft damage
Minor
Non-aircraft damage
No
Non-occupant Casualties
No
Occupant Injuries
Few occupants
Off Airport Landing
No
Ditching
No
Causal Factor Group(s)
Group(s)
Aircraft Operation
Safety Recommendation(s)
Group(s)
None Made
Investigation Type
Type
Independent

Description

On 10 November 2022, a Saab 340B (VH-VEQ) being operated by Link Airways on a scheduled passenger service from Canberra to Sydney for Virgin Australia departed with the remains of a propeller restraint still attached after starting the engines in normal ground visibility. With the flight crew unaware, the restraint was then severed as the engine was started and as the aircraft subsequently rotated, part of it was ejected into and through the fuselage with one of its attachment pins penetrating the cabin and injuring a passenger. When the cabin crew advised the Captain of a passenger problem which would require a return to land and an ambulance but not the origin of the problem, he advised ATC and the return was made as requested after which the context for the passenger injury became apparent.

Investigation

An Investigation into the event was carried out by the Australian Transport Safety Bureau (ATSB) and included reference to relevant recorded data downloaded from the aircraft CVR and FDR and from relevant airport CCTV footage. It was noted that the Captain had a total of 4,836 hours flying experience which included 1,423 hours on type. The First Officer had a total of 834 hours flying experience which included 436 hours on type. 

What Happened

Prior to what was to be the first flight of the day, both propellers had been restrained overnight to prevent windmilling using propeller straps that secured a propeller blade to the engine cowling. In accordance with the FCOM, the First Officer was instructed to carry out the external element of the ‘Daily Aircraft Inspection’ which involved removing both propeller straps, inspecting the engine and then “dressing” each propeller by rotating it 45° from its restrained ‘T’ position to an ‘X’ position to confirm it was free to rotate.

The First Officer carried out this procedure for the right propeller before continuing around the rear of the aircraft to conduct the same procedure on the left propeller. However, he then reattached the strap “so that passengers could safely board without the propeller windmilling”, which also required the attachment of a strap extension linking the propeller strap to the airstairs used to board the aircraft which was designed to prevent passengers from walking under the aircraft. When fitted, it also prevented the cabin door from being closed without first removing it. However, the strap extension remained in its normal stowage on the flight deck and was not fitted.

Once the passengers had boarded, the First Officer carried out a final external check of the aircraft, to confirm that it was prepared for flight including that all hatches were closed and all ground service equipment no longer required had been removed. They then closed the cargo bay door and re-boarded the aircraft using the airstairs and instructed the SCCM to close the cabin door. The left propeller strap was “inadvertently not removed”. The Dispatcher overseeing the departure subsequently stated that they had seen the First Officer closing the cargo bay door and entering the aircraft and this was confirmed by recorded CCTV footage which showed the Dispatcher near the cargo bay door at the time. However, they had not followed the First Officer for the whole of their inspection as they had then moved to a position ahead of the nose of the aircraft in order to be ready to signal the Captain that it was safe to start the engines. The Dispatcher stated that they had not looked for or noticed the strap still fitted to the left propeller.

Both engines were then started and CCTV showed that the left propeller then moved only slightly before stopping instead of beginning to rotate as it would normally do. Neither the Captain nor the Dispatcher noticed this brief movement or that the propeller was not initially rotating. As engine power was then increased in preparation for taxiing with the left propeller still restrained, 33 seconds after the initial slight movement, the pins securing the strap to the engine cowling failed and the strap remained secured to one of the blades. In a subsequent interview, the Dispatcher stated that although they had regarded the delay between the ‘cleared to start’ signal and the propeller’s rotation as unusual, they were aware that “pilots would sometimes complete other tasks in between signalling an engine start and commencing it”. Once the propeller was rotating at speed, it was impossible to see that the restraint was still attached to it.

The aircraft taxied to the runway and took off. The SCCM recalled that at about the time the aircraft had become airborne, “the propeller strap was thrown free of the blade and into the fuselage” partially entering the cabin as the two failed cowling pins that were attached to it disintegrated (see the illustration below).

SF34-Canberra-2022-propeller-strap-cabin

Part of the left propeller strap which entered the cabin at seat 2A. [Reproduced from the Official Report]

One pin fragment struck the leg of the passenger seated in 2A causing a minor injury (bruising). Passengers reported having heard “an extremely loud bang” and some of them were able to see at once that an object had penetrated the cabin. The pilots remained unaware until the SCCM recognised the propeller strap and realised what had occurred. After about half a minute airborne, the SCCM called the flight deck using the emergency call button and once in contact was recorded on the CVR as saying “Emergency, somebody…we need to get back to the airport”.

ATC were informed of the need to return and gave the necessary instructions. After 2½ minutes, the SCCM was called to ask if emergency services were required to meet the aircraft and said “yes… a passenger was hit”’ Further communication with the SCCM on the interphone then followed in relation to taxi procedures and provision of emergency services but there was no mention of the nature of the emergency and the flight crew were left with the impression that the emergency was only related to a passenger’s medical condition.

On reaching the assigned parking position, the passengers were disembarked and the injured passenger was assessed by the emergency services. A remnant of the propeller strap was recovered from the fuselage where it had caught on a stringer and the two cowling pins were no longer attached to the strap but sections of both were found still attached to the cowling (see the illustration below) whilst other parts had breached the fuselage and were recovered from the cabin floor. A small section of one cowling pin was not located.

SF34-Canberra-2022-propeller-under

Parts of the cowling pins found still attached to the engine and the remains of the propeller strap still attached to the propeller blade. [Reproduced from the Official Report]

SF34-Canberra-2022-cowling-pins

Parts of the two shattered cowling pins after recovery. [Reproduced from the Official Report]

Why It Happened

The failure of the First Officer to remove the left propeller restraint in accordance with routine everyday procedures could not be explained and neither could their earlier failure to fit the strap extension linking the left propeller restraint and the airstairs handrail. This latter strap was, according to the operator’s FCOM, intended to provide not only a visual indication of a restricted area around the propeller but also to function as a “safety mechanism restricting the passenger door stairs from being closed without removing the extension and propeller strap”. Had the required fitting of this extension not also been omitted, the failure to remove the propeller restraint itself would have been obvious to both the First Officer when re-boarding the aircraft and in the unlikely event that this was overlooked at that point, the SCCM would have subsequently been unable to close the door.

The Investigation examined the context for these failures and the subsequent missed opportunities to detect them. This revealed that failure of the operator’s pilots to fit the florescent webbing strap extension to the left propeller restraint was not unusual and this fact had been either unrecognised or alternatively recognised and ignored. The illustration below shows the extension in use.

SF34-Canberra-2022-strap-extension

The strap extension attached to the propeller strap. [Reproduced from the Official Report]

It was also found that the propeller restraint involved (and several others used by the operator) did not comply with the manufacturer’s design in that it did not have a visibility aid in the form of a high visibility streamer marked ‘Remove Before Flight’ attached (see the illustration below). Other streamers on restraints in regular use were found to be “discoloured with age and not effective”. It was also found that the orange-coloured webbing of many of the operator’s in use propeller restraints was “dull or faded with age”.

Data from the CVR also showed that despite a procedural requirement for the pilot responsible for the final external inspection and therefore propeller restraint removal to confirm by statement to the other pilot upon re-entering the flight deck that it had been stowed, no such statement had been made and its absence went unchallenged. The FCOM requirement that “the left seat pilot shall check the (left) propeller area is clear, the prop tie has been removed and fuel cap is on” before requesting a “clear left” confirmation from the ground crew overseeing the start was also ignored by the Captain. The Captain claimed that he had visually checked that the left engine was “safe to start” but had “not noticed” that the propeller strap was still fitted.

SF34-Canberra-2022-streamer

The propeller strop loop showing the attached high visibility streamer fitted to it. [Reproduced from the Official Report]

Finally, the contracted ground handling agent staff present as the First Officer completed their pre-flight check shortly before departure had not noticed the failure to remove the left propeller restraint and the same person when subsequently supervising the left engine start, had not noticed that the left engine propeller restraint was still fitted before confirming the engine was “clear to start”. The Investigation examined the ground handling arrangements for the departure and found that as the flight involved was being operated by Link Airways on behalf of Virgin Australia, ground handling support was being provided by Swissport under contract to Virgin Australia through a slightly modified IATA Standard Ground Handling Agreement (SGHA).

It was found that Article 5 of the SGHA as applied stated that Swissport “shall carry out all technical and flight operations services as well as other services having a safety aspect ..... in accordance with the carrier’s instructions” and that relevant “safety measures” included the performance of visual external safety/ground damage inspection of doors and panels and their immediate surroundings and such other inspection items as specified in Carrier's Manuals “immediately prior to departure”. It also stated that “in the case of absence of instructions by the Carrier, the Handling Company shall apply its own standard practices and procedures”.

The Investigation found a considerable degree of ambivalence in the effectiveness of the relationship between Link Airways and Swissport in respect of handling Saab 340 aircraft rather than the Airbus A320 operations which represented the bulk of their responsibilities at Canberra under the Virgin Australia SGHA. It was noted that guidance provided by Link Airways to Swissport to enable them to ensure their ramp staff supporting Saab 340 operations were appropriately trained and their activities effectively routinely audited stated that “the propeller strap was an item that the flight crew fitted prior to passenger disembarkation” and “did not include any further information about propeller straps”. One Swissport trainer stated that they had been told by Link Airways staff that “walk-arounds were the duty of the flight crew and not dispatchers”. Another Swissport trainer remarked that “while they knew that the Saab 340 had some form of propeller restraint, they assumed that the propeller strap and strap extension were inseparable and therefore that the cabin door could not be closed while the propeller strap was in place (so) did not consider the strap an item that should be checked by dispatchers”.

Seven Contributing Factors were formally documented based on the Findings of the Investigation as follows:

  • The aircraft was released for flight with the propeller strap still attached to the left propeller. Parts of the strap assembly subsequently penetrated the fuselage during take-off, injuring one passenger.
  • The First Officer did not remove the propeller strap as part of the final external check (walk-around) of the aircraft.
  • The Captain did not notice the propeller strap or the incorrect propeller position prior to engine start.
  • The Dispatch Coordinator did not notice the propeller strap or, during the engine start, the unusual propeller motion.
  • On one-third of the Link Airways Saab 340B flights for which video surveillance was examined, including the occurrence flight, the flight crews did not fit the strap extension between the propeller strap and the airstairs. As the cabin door could not be closed with the strap extension in place, its correct fitment would almost certainly prevent a flight from proceeding with a propeller strap fitted. [Safety Issue]
  • The propeller strap did not have a high-visibility streamer attached and Link Airways did not effectively manage the condition of propeller straps for its Saab 340B fleet. This affected the visibility of the straps during ground operations. [Safety Issue]
  • Guidance provided by Link Airways for training of Swissport Dispatch Coordinators did not explain the appearance, function and importance of the propeller straps. [Safety Issue]

Two Other Factors that Increased Risk were also identified:

  • Swissport did not ensure that the implemented training and audits for Link Airways’ Saab 340B dispatches incorporated all of the elements required in its Ground Operations Manual for pre-departure walk-arounds. [Safety Issue]
  • The cabin manager did not tell the flight crew that an object had penetrated the fuselage. While this had no bearing on the outcome, it limited the information available to the flight crew if aircraft systems had been damaged.

Safety Action taken by Link Airways to address the Safety Issues identified was noted as:

  • Amended the Cabin Crew Operating Manual to require: 
    • a check by the cabin manager to confirm that the strap extension is fitted before passenger boarding can commence. 
    • a check by the cabin manager that both propeller straps have been removed and that the propellers are dressed prior to engine start.
  • Amended the FCOM to require:
    • an explicit check in the engine start checklist that both propellers are ‘crossed’ [i.e. dressed] and clear’
    • the PF to confirm propeller rotation prior to the introduction of fuel.
  • Enhanced its Line Operational Safety Program in respect of ground pre- and post- flight inspections and confirmed training standards.
  • Rectified inadequate oversight of the condition and of its propeller straps to ensure they are all visually similar and include a high visibility streamer.
  • Amended the FCOM to include a check of propeller strap serviceability, along with that of other ancillary equipment.
  • Declared an intention to add regular inspections of aircraft protective equipment to the Maintenance Schedule and to provide technical guidance to maintenance personnel on how to correctly construct/maintain propeller straps.
  • Updated its Scheduled Air Transport Ground Handling Manual (SATGHM) - to be used by Swissport for training Dispatch Coordinators - to include more details on the use of the propeller strap and strap extension and on the Dispatch Coordinator’s responsibilities in ensuring they are removed before engine start.
  • Conducted audits on Swissport dispatches to ensure that the aircraft operator’s procedures as contained in the SATGHM were being correctly implemented.
  • Initiated an ongoing Safety Action Group meeting with Swissport and other ground stakeholders to provide assurance and risk management oversight to common identified hazards and occurrences.
  • Developed a Ground Operational Safety Programme designed to conduct random surveillance observations on ground handling activities to identify deviations from standard operating procedures and validate training standards.

In Conclusion, a Safety Message based on the Investigation Findings was as follows:

For those directly involved in aircraft operations, this occurrence highlights the importance of vigilance. When there are multiple risk controls in place and multiple responsible parties, it is easy to become complacent from an expectation that earlier checks have been done correctly and that future checks elsewhere in the system will likely catch anything missed.

From an organisational perspective, the occurrence illustrates the importance of strong communication and harmonised procedures. The use of external ground handling services has become increasingly common in aviation. The relationship between carrier and ground handler can add complexity to ground handling operations. In this instance, differences in expectations and understanding of ground handler responsibilities led to a dispatch procedure that was not effective in confirming that the aircraft was clear for engine start-up. It is critical that all involved parties have a complete understanding of their roles and responsibilities, and how they fit together to create a safe and functional operating environment.

The Final Report was released on 9 May 2024. 

Related Articles

SKYbrary Partners:

Safety knowledge contributed by: