Incident Description
On 1 May 2022 at 15:28 UTC, a Bombardier Q400 (registration SP-EQC) was on approach to runway 29 at Wrocław Airport (EPWR) when, during landing gear extension, the crew noticed that the left main gear indication showed an unsafe (RED) position and the left landing gear door was open (L.DOOR). The landing gear control lever was not illuminated. The crew aborted the approach, requested clearance from air traffic control to climb to 6000 feet, and entered a holding pattern to troubleshoot the issue.
The crew then checked the alternate landing gear extension panel, which displayed three green lights confirming all gear was locked down. The flight attendants visually confirmed that the left main gear was extended but the door remained open. The pilots performed the "Alternate LDG Gear extension" checklist, but the indications remained unchanged. Due to easterly winds, the crew decided to land on runway 11 at EPWR. The captain briefed the cabin crew for an emergency landing. The crew declared an emergency to air traffic control, requesting ground assistance, although they did not use standard PAN or MAYDAY phraseology. The landing on runway 11 was completed without incident.
Cause
The Polish State Commission on Aircraft Accident Investigation determined that the direct cause of the incident was an incorrect operation of the left main gear proximity sensor, which resulted in an error in the Proximity Sensor Electronics Unit (PSEU). This error caused the Landing Gear Control and Indication Panel (LGCIP) to display a LEFT MAIN GEAR unsafe indication. The primary cause of the incident could have been contamination of the proximity sensor. No contributing circumstances were identified.
Actions Taken
After the incident, the crew adjusted the sensor and performed tests, which confirmed normal system operation. The aircraft was returned to service. The incident was recorded in the operator's Safety Management System (SMS) database and classified according to the operator's criteria. It was discussed during a Weekly Safety Review meeting involving operations, flight, and maintenance departments. The operator made several updates to the Quick Reference Handbook (QRH) and other documentation:
- The "ALTERNATE LANDING GEAR EXTENSION or LDG GEAR INOP" checklist was amended to note that illumination of a green light on either the Primary or Alternate system is sufficient evidence that the respective gear is down and locked.
- The "LANDING GEAR INDICATOR MALFUNCTION" checklist was updated to address failures of light bulbs or sensors when primary green lights fail to illuminate despite red unsafe or amber door open indications.
- The LOT AOM (Aircraft Operating Manual) was revised with similar clarifications.
- The Director of Flight Operations published a reminder that MAYDAY or PAN PAN calls should be used immediately when an emergency or urgency situation occurs.
- The Fleet Chief Pilot for the DHC8 issued a Crew Info bulletin emphasizing that three green lights on either system confirm the landing gear is down and locked, and such landings should be considered normal.
No additional safety recommendations were formulated by the Commission.