News / B737 problems could hit freighter conversions if not quickly resolved

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The latest incident involving a Boeing 737-9 MAX has resulted in the temporary grounding of 171 aircraft, but if the problem is not resolved soon, it could also have repercussions for freighter conversions.

On Friday, Alaska Airlines’ flight 1282 was forced to return to Portland International Airport for an emergency landing shortly after take-off, after part of the fuselage fell off as the plane was climbing.

The ‘plug’, a panel inserted into the frame to fill an opening for an additional exit door, required for higher capacity configurations, was later found in a garden in Portland.

The following day the US Federal Aviation Administration (FAA) issued a directive ordering the immediate inspection of 737 MAX aircraft with plugs.

“Boeing 737-9 aircraft will remain grounded until operators complete enhanced inspections, which include both left and right cabin door exit plugs, door components, and fasteners,” said the FAA. “Operators must also complete corrective action requirements based on findings from the inspections prior to bringing any aircraft back into service.”

The European Union Aviation Safety Agency (EASA) has adopted the FAA’s emergency airworthiness directive. But, according to EASA, no European airlines operate MAX equipment with the configuration covered in the inspection order.

In recent years, conversions of 737NGs have increased vastly, but the current market conditions of cooling demand and lack of affordable feedstock, owing to rampant demand for passenger planes have put the brakes on this.

Bob Convey, SVP sales & marketing at narrowbody conversion specialist Aeronautical Engineers, is concerned about the repercussions of lengthy MAX groundings.

“Our view is that if the issues are not quickly resolved, and all the aircraft returned to service in a week or two, it will have an impact on feedstock availability and pricing. This would add insult to injury to both the A321 and 737-800 programmes and extend the recovery period even further.”

About 171 out of 218 MAX aircraft delivered to date are subject to the inspection order. These include Alaska’s 65,  about 20% of its fleet, and United Airlines’ 79 units. Other airlines affected include Turkish, Aeromexico and Copa.

United told The Air Current on Monday it had found multiple issues when inspecting its aircraft, including loose bolts and “installation issues in the door plug”.

Boeing has issued an inspection menu to customers, detailing the steps to be taken, and the FAA estimates it takes up to eight hours to perform the mandated inspection of an aircraft.

Alaska Airlines expressed confidence it could complete the checks within “the next few days”.

The US National Transportation Safety Board (NTSB) began an inspection of the Alaska aircraft, flight 1282, at the weekend, including the problems reported with pressurisation warning lights. Alaska pilots reported these had lit up on three previous flights, which were registered as “benign occurrences”. The airline said it had planned further maintenance checks into the matter and restricted deployment of MAXs to routes over land.

NTSB chair Jennifer Homendy said on Saturday: “It’s certainly a concern, and one we want to dig into and look at what occurred there, and if there is any relation at all or correlation on this event. It may have nothing to do with the auto-pressurisation system, it could be something just wrong with the light.”

In the worst case, this could be yet another problem in a string of issues that have plagued Boeing’s marquee narrowbody, which began with fatal crashes of 737 MAX aircraft of Lion Air and Ethiopian Airlines caused by software in the steering system that the manufacturer had not disclosed. This grounded the MAX for nearly two years.

Last year, the FAA instructed pilots to limit use of an anti-ice system on the aircraft type, because of concerns that inlets around the engines could overheat and break away. And in December, Boeing advised airlines to inspect the aircraft for a possible loose bolt in the rudder control system.

The separation of the plug from the fuselage on flight 1282 is not a matter of age. The plane was delivered to Alaska at the end of October and had flown 134 cycles by the end of 2023.

There have been no previous problems with plugs reported. According to one source, they have not only been used on MAX aircraft but also on its predecessor, the 737NG.