Pressurization System on Aircraft Boeing 737-300F, Aircraft MSN: 28567 During Flight Hanoi to Bangkok: Problem Solving and Root Cause Analysis

Pressurization system uncontrollable Root cause analysis and problem solving Corrective Action & Preventive Action


November 12, 2022


The aircraft, with type Boeing 737-300 freighter, Serial Number: 28567, Flight number: TMG-918, with a flight route from Hanoi International (HAN) to Bangkok International airport (BKK) on the date of 12 April 2021, with a take-off time of 22.00 UTC and landing time 22.25 UTC, is operated by PT XYX Airlines on a non-schedule flight. After taking off from Hanoi to Bangkok (HAN – BKK), with an altitude of nearly 10.000 ft flight level, the aircraft got a problem with the pressurization system in auto mode (auto system), and the cabin altitude indicator was shown 10.000 ft; cabin rate altitude indication at 2000 – 300 ft/minute (in normal rate 200 – 300 ft/minute). The pilot was unable to control the pressurization system in the auto system; in this condition, the Pilot followed the procedure for selecting the pressurization system from auto mode to manual mode, and after that, the cabin altitude indicator suddenly was shown fluctuated or became unstable. After the pressurization system operates in Manual mode and all conditions control by the flight crew, the captain makes the decision to aircraft return to base (RTB) flight back to Hanoi International airport (HAN) and land safely at 22.25 UTC.  The author wants to analyse the root cause of the pressurization system problem by using several methods, as per 5 whys, fishbone diagrams, and fault tree analysis. Then the author compares the root cause results of each method to take corrective and preventive actions to solve the problems. All these cases were in Reference to SDR Report Control Number: 012/SDR-YGH/TMG/IV/2021. The report submitted by PT.Tri M.G. Intra Asia Airlines on 12 April 2021 and the Flight Log Manual (FML) Page No: 03232, dated 12 April 2021. The purpose of this research is to identify the problem and determine the root cause of the problem's inability to control the pressurization system and make a plan for corrective action and preventive action; then, the team will implement the corrective action and preventive action. Quality Division will check and monitor the effectiveness of corrective and preventive action in three months. After that, the team & Quality Division create the procedure and policy for the company standard. The author and team used the methodology 5 why (cause and effect diagram), Fishbone diagram (Ishikawa Diagram), and Fault Tree Analysis (FTA), and from each method will be found the root cause analysis. Then the author combines all root cause analyses to identify the problem and create problem-solving. The main result of this research was that the company was able to determine and implement the corrective action and preventive action for the uncontrollable problem pressurization system. The problem of the pressurization system that cannot be controlled causes the aircraft to return to base or cancel a flight to be expected not to happen again in all aircraft operated by PT. XYX company in the future.