The Weekly Reflektion Week 30 / 2019

This week’s Reflektion is based on Nigeria Airways Flight 2120 that crashed shortly after taking off from Jeddah, Saudi Arabia on 11 July 1991.

Would you let commercial pressures compromise the safety of your operation? Where is your limit for taking chances?

Nigeria Airways Flight 2120 was a chartered passenger flight from Jeddah, Saudi Arabia, to Sokoto, Nigeria on 11 July 1991. The aircraft was a Douglas DC-8 operated by Nationair for Nigeria Airways. The flight was chartered to take pilgrims visiting Mecca back to Nigeria.

During take-off the crew heard a banging sound while the plane was taking off. One of the crew questioned whether it could have been a tire blowout, however since the air operating manual did not state that a tire blowout was cause to abort take-off the captain continued.

Shortly after take-off the flight attendant reported smoke in the cabin. The crew then experienced difficulties with the plane hydraulics and the cabin and cockpit pressurization. The captain decided to land and started to prepare the aircraft for an emergency landing. Unfortunately a fire had broken out that rapidly engulfed the centre section of the plane and spread rapidly. Passengers fell from the plane as it gradually broke up. The first officer bravely tried to land the plane however, it crashed about three kilometres from the runway. 261 people were killed.

Prior to departure, the lead mechanic had noticed that two of the tyres were below the minimum pressure for flight dispatch. There was in fact evidence that the tyres were known to be under-pressured from flights over the previous 4 days. An urgent note had been sent to the maintenance crew requesting replacement of the tyres due to wear and damage. The mechanics had attempted to inflate them, but no nitrogen gas was readily available, and the project manager, unwilling to accept a delay, disregarded the problem and readied the aircraft for dispatch. The plane had, after all, taken off a number of times with the tyres at a low pressure. The mechanics entered false pressure readings into the tyre log sheet so the flight crew were unaware of the problem.

The aircraft had travelled 5 km to the runway with air temperatures in excess of 40 C. When the aircraft was taxiing, the transfer of the load from the under-inflated No. 2 tyre to the No. 1 tyre on the same portside axle resulted “in over-deflection, over-heating and structural weakening of the No. 1 tyre. The No. 1 tyre failed very early on the take-off roll, followed almost immediately by the No. 2. The latter stopped rotating “for reasons not established”, and the subsequent friction of the wheel assembly with the runway generated sufficient heat to start a self-sustaining fire. When the landing gear was retracted the fire spread in the wheel compartment and quickly affected the hydraulic and pressurisation systems located nearby.

Nationair had a poor reputation for on-time service and mechanical problems. The project manager that authorized the flight was concerned that a delay in the flight could have led to the loss of the contract with Nigerian Airways. The project manager was under pressure from the Nationair executives to maintain schedule and keep costs under control.

Commercial pressures can cause people to push the limits on safety. The first time the limits are exceeded there may not be negative consequences. This can create a false sense of safety that the limits are not so important, and maybe things will be OK after all. A change in circumstances, in this case the hot conditions and the long journey to the runway, were enough to tip the balance and the Major Accident occurred.

Do you let commercial pressures compromise the safety of your operation?