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USAF Strategy for Aging Aircraft Subsystem Research and Development

Like many other nations today, the United States A_ir Force (USAF) is retaining their existing 
aircraft longer than planned. It is estimated that the current average age ofaircraft in the USAF 
inventory today is 22 years old. By 2005, 75% of the USAF inventory will be over 20 years old. 
As the age of our fleet continues to rise, aircraft mission capable rates degrade and there is a 
potential for increased risk to safety of flight should the aircraft not be properly maintained. 
Maintenance data indicates that air vehicle subsystems are one of the largest contributors to 
aircraft downtime due to in-service failures. Fortunately aircraft typically are not lost due to the 
subsystem failures. However, if one is not careful, this aspect can tend to foster an attitude that 
we should accept these failure rates. What this approach fails to recognize is that we no longer 
have the budget or the number of available aircraft to support this level of maintenance. The 
purpose of this paper is to discuss aging aircraft concerns found in air vehicle subsystems and the 
approach that the USAF is using to alleviate these concerns. 
BACKGROUND 
Philosophically, the USAF aging aircraft program began in the late 1950's followihg an in-flight 
structural wing failure of a B-47 aircraft [l]. As a result, the USAF developed the Aircraft 
Structural Integrity Program (ASIP) [2]. The ASIP [3] is a disciplined engineering process that 
defines all of the tasks necessary to ensure the structural integrity of the air vehicle airframes. 
ASIP is a cradle-to-grave process and has become the basis for our aging aircraft programs. 
ASIP has evolved over the last 40 years into a very effective and widely accepted processthat is 
used extensively throughout the USM. There is an Air Force Policy Directive [4] that requires 
implementation of the ASIP on all the USAF aircraft programs. The process has been very 
effective and we have not lost a USAF airgran due to an inherent structural failure for over ten 
years [5].