Unreliable Altitude Indications, 737 Freighter (Bad Day)
A 737 freighter had contaminated pitot tubes before unreliable airspeed indications.
The flight crew of a 737 freighter was presented with unreliable flight data information two days after the aircraft’s pitot probes were contaminated during maintenance, an ATSB (Australian Transport Safety Bureau) investigation details.
The Airwork-operated Boeing 737 freighter, with four crew on board had departed Perth on June 10, 2022, for a freight service to Christmas Island, via Port Hedland.
As the aircraft was leveling off at 33,000 ft, the flight crew observed a 340 ft. discrepancy between the altitude displayed on the captain’s altimeter and the altitude on the first officer’s altimeter, which was connected to the autopilot.
What happened to uncover the discrepancy of the 737 freighter?
On June 10, 2022, the flight crew of a Boeing 737-476SF freight aircraft, registered ZK-TLJ, noted a 340 ft. discrepancy between the captain’s and first officer’s altitude when operating in reduced vertical separation minimum airspace after departing Perth Airport, Western Australia. They had also observed an airspeed and Mach number difference, but this was within the manufacturer’s stipulated limits. The aircraft descended and the flight crew completed the Quick Reference Handbook – Airspeed Unreliable procedure. It was determined that the first officer’s instruments were reliable for a return to Perth. After landing, ground crews found foreign residue adhered to the lower surfaces of all 4 pitot-static probes.
Read the rest of the ATSB report here, including what the ATSB found and recommendations made.
Content and photo source/credit: ATSB, “Unreliable altitude indications, Boeing 737-476SF, ZK-TLJ 167 km west of Meekatharra Airport, Western Australia on 10 June 2022,” occurrence date: 10/6/22, investigation number: AO-2022-033. Final report.
Opt into the best RCA training — TapRooT® Root Cause Analysis
Sign up today for a 2-day or 5-day course, an Equifactor course, or an on-site course led by TapRooT® Instructors at your company. You may also browse all TapRooT® courses to ensure you will find the training to meet your needs.
TapRooT® RCA has been designed for investigating seemingly simple problems that could have been worse (precursor incidents) by using a simple 5-step process.
TapRooT® RCA can also be used to investigate major accidents by using the complete 7-step process.
- The 2-Day TapRooT® Root Cause Analysis Course teaches the essential techniques for investigating precursor incidents and fixing them to prevent major accidents.
- The Equifactor® Training Course also teaches how to use the TapRooT® techniques and Equifactor® Troubleshooting Tables to stop equipment problems.
- The 5-Day TapRooT® Advanced Root Cause Analysis Team Leader Training teaches the complete 7-step TapRooT® process and techniques to investigate major accidents, serious environmental releases, fatalities, major plant upsets, and serious injuries, as well as simple incidents.
TapRooT® is global to meet your needs. If you need specific course times or locations, please see our full selection of COURSES.If you would like for us to teach a course at your workplace, please reach OUT to discuss what we can do for you, or call us at 865.539.2139.
