As part of its continuing ageing-aircraft initiative, the US Federal Aviation Administration has ordered new inspections or modifications of fuselage skin-panel lap joints on 33 US-registered Boeing 737-100/200s with more than 60,000 flights.

A further 34 737s owned by foreign airlines are affected by the airworthiness directive (AD), and aviation authorities responsible for those aircraft have been notified of the FAA action. Operators of 737s which exceed the 60,000-flight mark in the future must also comply with the directive.

The AD, covering lower lap joints, complements one issued three years ago, involving upper lap joints. Cracks in the joints - where skin panels overlap - could cause rapid aircraft-decompression. The latest AD results from reports of cracking in the lower-fuselage skin-panel lap joints.

The US inspection order affects 17 aircraft with more than 60,000 flights. The modification order affects 16 737s which have completed more than 70,000 flights. The FAA says that seven aircraft have already been modified.

Modifications must be completed within 600 flight cycles or 80 days. The preventative measure must be taken regardless of whether cracks are found. The maintenance work is expected to cost $30,000-95,000, and each inspection $14,000-37,000. Most of the major US network carriers are affected, as well as low-cost operators, such as AirTran Airways, Frontier, Pan Am and Vanguard.

Source: Flight International