By Simon Hradecky, created Thursday, Nov 15th 2018 19:07Z, last updated Monday, Jul 20th 2020 13:30Z A PAL Airlines de Havilland Dash 8-300, registration C-FPAE performing flight PB-1922 from Churchill Falls,NL to Deer Lake,NL (Canada) with 47 passengers and 4 crew, was on approach to Deer Lake when the crew received an unsafe nose gear indication and went around at about 11:40L (15:10Z). The crew performed a low approach to Deer Lake to have the nose gear inspected from the ground, which showed the nose gear was not down. Due the present weather at Deer Lake the crew decided to divert to Stephenville,NL (Canada) where the crew performed a nose gear up landing at 12:30L (16:00Z). There were no injuries, the damage to the aircraft is being assessed.



The airline reported the aircraft "had an indication of a potential nose landing gear issue. The crew followed prescribed procedures including a flyby of the Deer Lake control tower for a visual indication of the nose gear position. Given adverse weather in Deer Lake, the aircraft proceeded to Stephenville for landing as the nose gear could not be confirmed as locked. Stephenville Airport rescue vehicles met the aircraft on landing. The aircraft landed without the nose gear locked in position and came to a stop on the runway."



On Jan 10th 2019 the Canadian TSB reported on approach to Deer Lake the nose gear did not completely extend when the crew selected the gear down. The aircraft entered a hold for about one hour while the crew was working the checklists to resolve the problem, then the crew declared emergency and decided to divert to Stephenville due to deteriorating runway conditions in Deer Lake. The aircraft landed in Stephenville with partially extended nose gear and came to a stop about half way down the runway. There were no injuries. The TSB opened a Class 3 investigation.



On Jul 20th 2020 the TSB released their final report concluding the probable causes of the accident were:



Findings as to causes and contributing factors

These are conditions, acts, or safety deficiencies that were found to have caused or contributed to this occurrence.



- For undetermined reasons, a previous repair to the inner cylinder of the nose landing gear shock strut was not designated with a specific permanent marking as required by the approved component maintenance manual, resulting in the installation of a standard size bearing where an oversize bearing was required.



- The reduced sealing force caused by the smaller-than-required bearing installation likely allowed the nose landing gear shock strut to leak.



- The reduced hydraulic fluid volume, in addition to a possible nitrogen leak, reduced the internal static pressure of the nose landing gear shock strut and allowed it to partially compress when it was in the up position.



- The airflow encountered in flight when the nose landing gear was lowered further compressed the nose landing gear shock strut and allowed the tires to impinge on the aft landing gear doors, thereby jamming the nose landing gear in a partially extended position.



Findings as to risk

These are conditions, unsafe acts, or safety deficiencies that were found not to be a factor in this occurrence but could have adverse consequences in future occurrences.



- The absence of formal in-flight procedures for flight crews to consult third parties using smartphones increases the risk of distraction, leading to a breakdown in crew resource management during critical phases of flight.



- If crew members are unable to communicate effectively with each other, they are less likely to anticipate and coordinate their actions, which could jeopardize the safety of the flight.



- If pilots delay making a decision to divert, there is a risk that the fuel remaining will be insufficient to provide the flight endurance required to mitigate unforeseen circumstances at the diversion airport.



- If aircraft are operated beyond airspeed limitations, there is a risk of compromising flight safety, resulting in injury to the occupants or damage to the aircraft.



- If manufacturers require an aircraft inspection of items critical to the safety of flight without providing a checklist of items and inspection criteria, there is a risk that operators will not identify unserviceable items or conditions.



- If voice recordings and cockpit sounds are not available to an investigation, the identification and communication of safety deficiencies to advance transportation safety may be precluded.



Other findings

These items could enhance safety, resolve an issue of controversy, or provide a data point for future safety studies.



- Because the nose landing gear had already moved from the uplocked position and was jammed in a partially extended position, pulling the nose gear release handle had no effect.



The TSB analysed:



The NLG shock strut was repaired at its first overhaul at an unknown facility by a previous operator in the United States, and no records were available from that overhaul event.



In 2014, the NLG shock strut was overhauled by Safran Landing Systems, Canada Inc. This was the second overhaul, and no rework or repair to the lower bore of the inner cylinder was conducted. Because the interface between the inner cylinder bore and lower bearing is a static joint, dimensional checks would normally occur only if an unserviceable condition such as wear or corrosion is observed. Any repair requiring oversize parts requires identification of the rework to be permanently identified on the reworked component.



For undetermined reasons, a previous repair to the inner cylinder of the NLG shock strut was not designated with a specific permanent marking as required by the approved component maintenance manual, resulting in the installation of a standard size bearing where an oversize bearing was required. This resulted in excessive clearance between the installed bearing and the lower bore of the inner cylinder. The reduced sealing force caused by the smaller-than-required bearing installation likely allowed the NLG shock strut to leak.



Similar to a previous occurrence involving partially extended nose landing gear on a Dash 8 aircraft (TSB Air Transportation Occurrence A98W0008), it was determined that the reduced hydraulic fluid volume, in addition to a possible nitrogen leak, reduced the internal static pressure of the NLG shock strut and allowed it to partially compress when it was in the up position. The airflow encountered in flight when the NLG was lowered further compressed the NLG shock strut and allowed the tires to impinge on the aft landing gear doors, thereby jamming the NLG in a partially extended position.



In normal operations, pulling on the nose gear release handle unlocks the NLG forward doors and unlocks the NLG from the uplock position. In this occurrence, because the NLG had already moved from the uplocked position and was jammed in a partially extended position, pulling the nose gear release handle had no effect.



With respect to Cockpit Resource Management the TSB analysed:



Standard operating procedures are developed to optimize communication, and therefore crew resource management (CRM) for the flight crew. Having a third party provide input during an emergency can be helpful. However, PAL had not developed procedures for such third party input to flight crew using smartphones. As a result, including the PAL personnel at CYYT (the CYYT team) as an additional channel of communication for an extended period of time decreased the crews shared situational awareness during critical phases of flight, and therefore disrupted checklist flow and coordination normally required to complete checklists effectively. The absence of formal in-flight procedures for flight crews to consult third parties using smartphones increases the risk of distraction, leading to a breakdown in CRM during critical phases of flight.



Additionally, the flight crew improvised communication by having the captain call the CYYT teams phone using his Bluetooth headset, and the first officer (FO) use a smartphone application to connect to a smartphone in that same room. During the descent and approach phases, the FOs smartphone connection was lost while the captain continued the conversation with the CYYT team. This led to breakdowns in communications in the cockpit, with the captain having 2 conversations at once, and requiring the FO to prompt the captain several times during critical phases of flight.



If crew members are unable to communicate effectively with each other, they are less likely to anticipate and coordinate their actions, which could jeopardize the safety of the flight.



https://flightaware.com/live/flight/PVL1922/history/20181115/1255Z/CZUM/CYDF

https://flightaware.com/live/flight/PVL1922/history/20181115/1440Z/CYDF/CYYT



Metars Deer Lake:

CYDF 151700Z 29012G27KT 190V350 6SM -SN BLSN FEW010 BKN022 BKN150 M02/M07 A2980 RMK SF2SC3AC2 /S02/ PRESRR SLP093=

CYDF 151600Z 29019G46KT 250V310 4SM -SN BLSN FEW010 SCT018 BKN160 M03/M07 A2972 RMK SF2SC2AC2 SLP066=

CYDF 151528Z 29023G38KT 2 1/2SM -SN BLSN FEW007 SCT017 BKN160 M03/M07 A2970 RMK SF2SC2AC2 SLP060=

CYDF 151500Z 28021G38KT 1SM -SN BLSN SCT010 BKN019 BKN160 M03/M06 A2970 RMK SN2SF2SC2AS1 SLP059=

CYDF 151400Z 28022G33KT 1SM -SN BLSN SCT010 BKN022 BKN160 M03/M06 A2969 RMK SN2SF2SC1AS1 /S01/ SLP058=

CYDF 151300Z 28016G32KT 1SM -SN BLSN SCT009 BKN020 BKN160 M03/M06 A2965 RMK SN2SF2SC2AC1 PRESRR SLP044=

CYDF 151244Z 29017G30KT 1SM -SN BLSN SCT009 BKN017 BKN160 M03/M06 A2964 RMK SN2SF2SC1AC1 PRESRR SLP038=

CYDF 151225Z 28021G32KT 3/4SM -SHSN BLSN SCT007 BKN017 BKN160 M03/M06 A2961 RMK SN2SF2SC1AC1 PRESRR SLP030=

CYDF 151200Z 28020G36KT 5/8SM -SN BLSN SCT007 BKN017 BKN160 M03/M06 A2958 RMK SN2SF2SC1AC1 /S04/ PRESRR SLP020=

CYDF 151131Z 29022G44KT 3/4SM -SN BLSN SCT008 BKN017 BKN160 M03/M06 A2953 RMK SN2SF2SC2AC1 PRESRR SLP003=

CYDF 151100Z 29022G39KT 1/2SM -SN +BLSN VV007 M04/M06 A2946 RMK SN8 PRESRR SLP980=



Metars Stephenville:

CYJT 151800Z 32015G25KT 290V350 15SM BKN023 M02/M08 A3000 RMK SC7 SLP162=

CYJT 151700Z 33016G30KT 7SM BKN021 M02/M08 A2998 RMK SC7 SLP154=

CYJT 151600Z 33019G27KT 15SM BKN021 M03/M07 A2994 RMK SC7 SLP141=

CYJT 151500Z 31022G32KT 15SM BKN021 M03/M08 A2991 RMK SC7 SLP132=

CYJT 151400Z 31019G31KT 12SM BKN021 M03/M08 A2987 RMK SC7 SLP119=

CYJT 151300Z 31021G37KT 12SM BKN021 M03/M08 A2983 RMK SC7 SLP104=

CYJT 151200Z 31021G35KT 280V340 12SM BKN021 M03/M08 A2979 RMK SC7 PRESRR SLP089=



The aircraft sitting on its nose:





The aircraft seen on the runway (Photo: Toby Lucas):







