Aerospace Systems Engineer

Life Cycle

Life Cycle Engineering

The SFR, PDR, CDR cycle makes good engineering sense even if the traditional “waterfall” timeline is approached as the more realistic spiral or iterative development life cycle.

SFR is the culmination of requirements analysis. SFR confirms that the contractor understands the basic functions that the system needs to do and has decomposed them across a notional functional architecture.


After SFR the design work begins with each segment, element and component designing implementations that fulfill their allocated requirements.


PDR season generally is executed as a bottoms up proposed design presentation with each successive layer showing how the component design flows up to fulfill the requirements allocated to their level.
NOTE: If the requirements analysis and allocation was not done, or done poorly, the bottoms up PDR process doesn’t work.

The culmination of PDR is acknowledgement that the proposed preliminary design appears adequate and is authorization to move forward towards CDR where the decision to “build the beast” is made. After CDR “we’re bending metal”