Final Investigation Report by Safety Investigation Board (SIB) on Pakistan Civil Aviation Authority (CAA) website:
https://www.caapakistan.com.pk/Upload/S ... IB-417.pdf
4.1 Findings.
4.1.1 The aircraft was grounded on 31 August 2018 (since last 84 days) primarily for Check'A' maintenance which takes generally 02 working days to complete.
4.1.2 During this grounding of the aircraft, components including engines, propellers and brake assemblies etc were taken out to fill up deficiencies on other aircraft in PIAC.
4.1.3 The engineering staff towed the aircraft and conducted this high performance ground run with major deficiencies in maintenance as well as documentation.
4.1.4 Non-standard / incompatible set of wheel chocks (smaller than recommended) were placed for nose, left and right wheels. The wheel chocks used for the nose wheel were meant to be used for a GPU and not for the aircraft ground run. No chocks were placed behind the main wheels. The chocks recommended by the OEM were never demanded / procured by PIAC since induction of the ATR.
4.1.5 The High Pressure hydraulic lines were required to be subjected to bleeding / purging after replacement of brake assemblies. The activity was documented but was either not performed at all or was performed in an inadequate manner.
4.1.6 The hydraulic lines remained filled with air and there was very little hydraulic fluid in the system. Consequently, the normal as well as emergency brakes were not effective.
4.1.7 The brake pressure throughout engine performance run-up was recorded between 39-45 psi whereas it was required to be 3000 psi.
4.1.8 Nose wheel steering was not made available.
4.1.9 The aircraft initially moved rearwards by 10 feet during a planned maintenance task of Thrust Reversal Check.
4.1.10 Seeing this reanruard movement of the aircraft, the ground run operator (being in panic) shifted the power level to Flight ldle position instead of moving it to Ground ldle or moving Condition Lever to shutoff position.
4.1.11 In the absence of effective wheel brakes, proper sized wheel chocks, and nose wheel steering; and in the presence of designed thrust at Flight ldle position, the ground run operator could not control the aircraft. The aircraft continued forward movement for about 450 ft, and came to a stop after colliding with two dormant aircraft belonging to SAL
4.1.12 The evidence of low hydraulic level in the reservoir was found alleviated next morning. A strainer in the filling neck of hydraulic reservoir, which was missing after the accident, was found to be in place next morning.
4.2 causes of occurrence. The occurrence was caused due to: -
4.2.1 Non-adherence to the laid down maintenance procedures by PIAC - in which important task of bleeding / purging of brake system was either not performed or was performed in an inadequate manner.
4'2.2 Deficiency in required maintenance support equipment at the organization level - in which recommended wheel chocks were not procured and therefore were not available for use.
4.2.3 Lack of professionalism of maintenance crew of PIAC in which the maintenance engineer was unable to judge situation correctly and could not
initiate a corrective action at an early stage.
4.2.4 lnadequate assessment process for authorization of technical personnel for engine ground run-up of ATR aircraft.
5. SAFETY RECOMMENDATIONS
M/s PIAC is required to ensure compliance of OEM requirements and approved company procedures in letter and spirit essentially required for conducting high performance grou nd run-ups.
M/s PIAC is required to ensure an immediate procurement of the OEM recommended chocks in adequate quantity at all applicable stations for the ATR aircraft.
M/s PIAC is required to revisit the in-vogue procedure for issuance of the license for ground run-ups for the engineers. ln this regard, it is recommended that practical evaluations may be done on the aircraft prior to issuing ground run permits.
All currently licensed ground run-up operator's of PIAC may be re-assessed by including practical evaluations on the aircraft.
M/s PIAC is required to ensure that in the event of any serious incident / accident, the evidence is adequately preserved and secured.
Directorate of Airworthiness, PCAA is requested to undertake an audit of PlAC maintenance of ATR aircraft specifically for availability of support equipment, spares, maintenance practices, documentation and competence of personnel to perform critical maintenance tasks.
Abbas
