During a post flight check on Nimrod XV227 on 22 November 2004, it was discovered that a portion of Supplementary Cooling Pack ducting had failed. A unit inquiry was held which concluded that it was caused by pitting and cracking corrosion leading to failure. The unit inquiry made the following recommendations and the table identifies actions taken in response.
Recommendation Action taken The ruptured duct is replaced with new manufactured items on a fleet-wide basis as soon as possible. Recommendation closed. All such ducts fitted to in-service aircraft have been replaced with newly manufactured items. A lifing policy is introduced for the ruptured duct and all similar ducts. See comments on maintenance policy recommendation. Action ongoing. A maintenance policy should be instigated for the ruptured duct and all similar ducts. A study into the need for a preventative maintenance/lifing policy for this and similar ducts has been concluded by the Designer (BAE Systems). Their report, which is due to be issued imminently, is based on the results of a detailed analysis of a sample of ducts taken from a number of MR2 aircraft. This analysis has taken time to complete, but the report is expected to recommend that a lifing policy be introduced. Ducts due for replacement would be replaced during scheduled maintenance activities and it is anticipated that such a duct replacement programme would be in place by December 2007. Action ongoing. The extent of the hot air leak warning system is reviewed to ensure that all possible duct failures are covered. Recommendation closed. A review of the aircraft warning systems revealed that the affected Supplementary Cooling Pack Duct was the only duct whose failure would not have been detected. A hot air leak warning system is introduced for the ruptured duct and cross-air bleed ducts. Recommendation rejected. The duct failure was an isolated incident and was in the only part of the system where a leak would not have been detected. All of these ducts have been replaced with newly manufactured items that, based upon the previous 25 fault-free years that the original duct had been fitted, are expected to last well beyond the planned MR2 Out of Service Date (early part of the next decade). Moreover, fitting a discrete hot air leak warning system would be a complex modification that would have to be embodied across the fleet during its maintenance cycle and therefore take several years to embody. Considering the Out of Service Date of the Nimrod MR2, the fitting of such a system was not considered to be practicable. Action closed. This incident is highlighted as a training point for Air Engineers. The incident was immediately publicised through the Air Engineer command chain at RAF Kinloss. Action closed. The Aircrew Flight Reference Cards (FRC) regarding Supplementary Cooling Pack malfunctions are amended to reflect the information in the aircrew manuals. Amendments were made to Aircrew Flight Reference Cards and Aircrew Manuals to reflect the incident. Action closed.