Flight 2120: Neglected Low Tyre Pressures and Altered Records

On July 11, 1991, Nigeria Airways Flight 2120, a McDonnell Douglas DC-8-61 operated by Canadian Nationair, departed from Jeddah-King Abdulaziz International Airport, Saudi Arabia, en route to Sokoto, Nigeria. The aircraft carried 247 passengers and 14 crew members. Shortly after takeoff, the plane experienced a catastrophic failure, resulting in a crash that claimed all 261 lives on board. Investigations revealed a chain of maintenance oversights, falsified records, and non-compliance with critical technical requirements that directly contributed to the disaster.

Pre-Flight Maintenance and Tyre Pressure Issues

Prior to departure, the aircraft's left main landing gear tyres (#2 and #4) were found to be significantly under-inflated, with pressures below the minimum required for safe flight dispatch. The lead mechanic identified this issue and attempted to inflate the tyres but was unable to do so due to the unavailability of nitrogen gas, which is necessary for inflating aircraft tyres. The only other source of nitrogen was Saudi Arabian Airlines, but the inevitable delay in obtaining it was unacceptable by the project manager, who lacked the technical qualifications to assess the safety risks. He insisted on proceeding, and the aircraft was cleared for departure without the low tyre pressures being corrected.

Alteration of Maintenance Records

In an attempt to conceal the under-inflated tyre pressures, a mechanic altered the maintenance records. The original tyre pressure readings, which were below the required minimums, were changed to reflect acceptable values. This falsification of maintenance records misrepresented the aircraft's airworthiness and bypassed necessary safety checks that could have prevented the flight from departing in an unsafe condition.

Sequence of Events

Approximately 15 seconds after brake release during the takeoff roll, an oscillating sound was heard in the cockpit. The first officer remarked, "We got a flat tyre, you figure?" Shortly thereafter, the #1 tyre on the left main landing gear failed, followed by the #2 tyre. The #2 tyre stopped rotating for reasons not fully understood, leading to excessive friction between the wheel assembly and the runway surface. This friction generated sufficient heat to ignite a fire in the wheel well.

As the aircraft continued its takeoff, the fire spread, compromising hydraulic and electrical systems. The flight crew experienced a loss of pressurization and hydraulic control, leading to further system failures. Despite these escalating issues, the crew attempted to return to the airport for an emergency landing.

The fire within the wheel well intensified, eventually breaching the cabin floor. The intense heat caused seat harnesses to burn through, leading to passengers falling from the aircraft mid-flight. The aircraft's structural integrity deteriorated, and control was lost. The aircraft crashed approximately 2.8 kilometers short of the runway, resulting in the deaths of all 261 occupants.

Findings from the Investigation

The investigation into the accident revealed several critical findings:

• The aircraft was dispatched in an unairworthy condition due to the under-inflated tyres.

• Maintenance records were falsified to conceal the tyre pressure deficiencies.

• The project manager, lacking the necessary qualifications, authorized the flight despite known safety issues.

• The flight crew was not informed of the tyre pressure issues, depriving them of critical information needed to make informed decisions during the flight.

• The aircraft was not equipped with fire detection or suppression systems in the wheel well, allowing the fire to escalate unchecked.

Conclusion

The crash of Nigeria Airways Flight 2120 was not caused by a single error but by a series of preventable failures, most notably the neglect of tyre pressure requirements. Equally serious was the falsification of maintenance records, which gave the flight crew no indication of the low tyre pressures. The disaster underscores the profound responsibility of airlines, maintenance personnel, and management to ensure that aircraft are technically fit for flight.

Numerous industry and regulatory actions both preceded and followed the 1991 accident. Next week, we’ll cover how EASA, in a comprehensive response to multiple incidents and accidents of this type, amended CS-25 in 2020 to require new large aircraft to ensure no tyre operates below its minimum serviceable pressure, and CS-26 to extend this requirement to operators of existing aircraft through mandatory tyre pressure tasks in the Aircraft Maintenance Program (AMP).

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