Boeing 737: More than 300 jets to be checked for suspect parts

Key components ‘may have been improperly manufactured and may not meet all applicable regulatory requirements for strength and durability’, says the FAA

More than 300 Boeing 737 jets are being checked for a defect that could cause further mayhem for operators of the aircraft type.

The Boeing 737 Max has been grounded worldwide for 12 weeks following two fatal crashes in which 346 people died. Both tragedies involved an anti-stall system installed to counteract a tendency for the nose to rise in some circumstances.

Now the Federal Aviation Administration (FAA) has warned that key parts “may have been improperly manufactured and may not meet all applicable regulatory requirements for strength and durability”.

The assemblies in question are the slat tracks. They guide the slats on the aircraft’s wings that adjust the leading edge. Deployment of the slats allows an aircraft to fly safely at lower speed.

The FAA says: “We have determined that up to 148 parts manufactured by a Boeing sub-tier supplier are affected.

“The affected parts may be susceptible to premature failure or cracks resulting from the improper manufacturing process.

“Although a complete failure of a leading edge slat track would not result in the loss of the aircraft, a risk remains that a failed part could lead to aircraft damage in fight.”

The regulator says it will issue an “airworthiness directive” to require airlines with the suspect parts to replace them within 10 days.

Crucially the problem affects not just Boeing 737 Max jets – which are currently all grounded – but also the older NG type, as flown by many airlines including Ryanair, Norwegian, Jet2 and Tui Airways.

Boeing says it has identified 21 737NGs that are “most likely” to be fitted with the suspect parts. But it is also telling airlines to check an additional 112 NGs.

The planemaker says: “One batch of slat tracks with specific lot numbers produced by a supplier was found to have a potential nonconformance."

It is sending replacement parts to the bases of affected aircraft. Boeing estimates: “Once the new parts are in hand, the replacement work should take one to two days.

“If operators find the parts in question, they are to replace them with new ones before returning the airplane to service.”

Boeing says it is unaware of any “in-service issues related to this batch of slat tracks”.

Kevin McAllister, president and CEO of Boeing Commercial Airplanes, said: “We are committed to supporting our customers in every way possible as they identify and replace these potentially non-conforming tracks.”

With the summer season now under way, airlines in Europe and North America are at full stretch. There is very little slack in the system – mainly due to the grounding of nearly 400 Boeing 737 Max jets, and the non-delivery to airlines such as Ryanair.

Removing more aircraft from fleets for replacing the parts could lead to further cancellations.

Boeing says that 20 737 Max aircraft are most likely to have the parts in question, and that an additional 159 of the type should be checked. As all Boeing 737 Max jets are grounded, current operations will be unaffected.