West Cape Ferries SW4 at Lanseria on Jun 13th 2010, gear up landing
Last Update: November 7, 2012 / 16:48:04 GMT/Zulu time
The pilot executed a belly "wheels up" emergency landing after the left main landing gear failed to extend.
The new tyres installed on the main landing gear wheels were not in compliance with the instructions of the Fairchild Service Letter 226-SN-131.
The aircraft actually was on approach to Polokwane's runway 05 when upon extending the gear the left hand main gear indicated unsafe prompting the crew to abort the approach, tower suggesting they should perform a low approach instead to have the gear inspected from the ground. Tower subsequently reported that the left main gear doors were partly open but the gear had not extended. The crew entered a holding for about 15 minutes to work the relevant checklists and attempt an alternate gear extension which also failed to lower the left gear strut. After a high gravity maneouver also failed to lower the left main gear the crew decided to return to Lanseria and entered a hold near Lanseria again attempting all emergency maneouvers to lower the left main gear strut, which all failed to get the gear strut out of the wheel bay. About 2.9 hours after departure from Lanseria the crew conducted another low approach to Lanseria's runway 06L to have the gear again inspected, which again confirmed the left main gear doors were partially open but the gear strut had not extended. The crew retracted the gear for an intentional wheels up landing, flew a tear drop procedure turn and positioned for a landing on runway 24R. On short final the crew shut both engines, feathered the propellers and switched off all electrical power, which also shut all radios on board of the aircraft down. The aircraft gradually slowed on its belly and came to a stop on the runway center line. There were no injuries, the aircraft sustained substantial damage.
The captain (37, ATPL, 6,900 hours total, 400 hours on type) was pilot monitoring for the sector to Polokwane, but took control from the first officer (55, CPL, 1,630 hours total, 35.4 hours on type) when the gear did not fully extend at Polokwane and assumed role of pilot flying for the remainder of the flight.
The aircraft had accumulated 27,532 flying hours in 27,353 cycles.
After the aircraft was lifted onto jacks, all gear extended freely after a damaged nose landing gear door had been freed, cockpit indications showed three greens.
The following day, after first repairs to the hydraulic lines damaged in the belly landing had been made, the aircraft was again jacked up, the hydraulics activated and gear swings were attempted. The gear retracted cleanly with all gear doors closing properly, however, only the nose and right main gear extended after the gear was selected down. The left main gear was blocked from extension by jammed gear doors, the SACAA determined however the doors jammed as result of damage sustained during the belly landing. The doors were removed, after which the gear swung up and down freely without any further fault.
The SACAA thus analysed that there was no mechanical defect with the landing gear. Due to the damage all gear doors received during the belly landing the rigging of the doors could not be verified however. There had been prior occurrences where gear struts did not extend due to incorrectly rigged gear doors leading to a reduced distance between tyres and gear door, several of the occurrences also revealing larger than required tyre dimensions contributing to the occurrence.
The tyres on ZS-ZOC had recently been recapped, the diameter of the tyres were 19.5 inches and a shoulder width of 6.75 inches with a maximum diameter of 19.2 inches and should width of 6.35 inches permitted.
Service Letter 226-SN-131 indicated that newly capped tyres exceeding dimensions could cause interference problems in the wheel wells, particularly main wheel wells, the tyre should not exceed a diameter of 19.7 inches and a shoulder width of 6.6 inches. The letter warned, that a newly fitted tyre will increase its dimensions once in use.
The SACAA reported that the Aircraft Maintenance Organisation (AMO) having installed the tyres was "reluctant" to assist the investigation, the management did not voluntarily provide maintenance documentation and in general did not want to cooperate with the investigators. The AMO has been reported to the regulator as a result. The investigation determined that the AMO did not have the experience, necessary equipment and qualification to conduct maintenance it has been certified for on May 1st 2010.
The aircraft had not yet been included on the operator's certificate (AOC), an application to include the aircraft on the AOC had been filed on Jun 4th 2010, the application reached the SACAA on Jun 8th 2010. SACAA's Airworthiness Department was still reviewing the application when the accident occurred. The operator was thus found in violation of applicable regulations.
The SACAA analysed that the crew did follow the checklists which recommended to perform a gear up landing in case of a main gear strut not extending. Lanseria aerodrome had been informed and was prepared for the emergency wheels up landing. The tyre diameters were found within the maximums given in the service letter, the shoulder widths however exceeded the maximums provided.
The SACAA analysed that the aircraft had been used unlawfully as the aircraft had not been approved onto the operator's AOC. The SACAA stated however, that regulations require the SACAA to complete the airworthiness assessment within 2 business days which had expired leading to the misconception by the operator, that they were now free to use the aircraft. The application however was found on the table of one of the inspectors and had not been completely approved by the time of the accident. The SACAA reserves the right by provision in the regulations that an application to include an aircraft with the AOC may take longer if not all information was provided or information provided did not verify correct. The operator was aware of this provision but believed everything was in order. The SACAA nonetheless maintains the point of view that the aircraft was illegally used at the time of the accident.
The investigation further analysed: "It appears as though the application could not be approved, due to the unavailability of airworthiness personnel. The application was put on someone table and left not being processed. The SACAA did not communicate with the Operator informing them of the reason for the delay. The evidence shows that the responsible department did not comply with internal procedures of two days to approve the application."
No safety recommendations were released as result of the investigation.
This article is published under license from Avherald.com. © of text by Avherald.com.
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