Boeing's 737 programme is facing a new challenge to return to full-rate production, after it confirmed that thousands of small pieces of structural hardware must be replaced because of a lack of corrosive coating.

The airframer says the components, known as nutplates, do not present "an immediate safety of flight issue". But the non-conforming nutplates have been fitted in aircraft delivered over the last 15 months.

This problem impacts "thousands" of nutplates in each 737 fuselage. The company explains that about 30% will require replacement, a number that runs about 3,000 to 4,000 nutplates per fuselage according to a programme source, although the number varies depending on the model of 737.

Boeing is currently ramping up 737 production to its normal rate of about one per day, after a 57-day strike by machinists ended earlier this month. The nutplate quality issue, however, means assembly workers must scramble to replace the parts before each aircraft now on Boeing property can be delivered.

 737 production
 © Jon Ostrower

The company emphasizes that no 737 will be delivered unless it meets proper conformity standards. The company declines to specify what impact the nutplate replacement would have on the pace of production and deliveries, but Boeing says it is devoting significant resources to solving this problem quickly.

Spirit AeroSystems is responsible for development of the 737 fuselage at its Wichita, Kansas facility. Once completed, the green 737 fuselage is shipped by rail to Renton, Washington, for final assembly. After final assembly, aircraft are flown to Boeing Field near downtown Seattle for delivery to customers.

Boeing says that one of three of Spirit's nutplate suppliers had been delivering parts lacking anti-corrosion material, adding that a root-cause analysis will be undertaken in conjunction with Spirit to prevent the problem from recurring. Spirit is unavailable for comment.

All non-conforming nutplates that have yet to be installed at Spirit have been returned to the supplier, says Boeing.

Staff from Spirit have been dispatched to the Seattle area to help identify and fix fuselage sections that are not yet in the final assembly phase. However, the problem is not limited to only those aircraft waiting for assembly and delivery.

According to Boeing, 737s delivered to customers since August 2007 contained non-conforming nutplates. Boeing's delivery website says that 394 737s were delivered between August 2007 and October 2008.

The company is working with the FAA to address the in-service fleet. Boeing says that only areas exposed to moisture could potentially present problems in the long-term by corroding prematurely.


Source: Air Transport Intelligence news