Critical design review could provide answers for fighter

Lockheed Martin is reviewing options to tackle signs of weight problems with the F-35 Joint Strike Fighter, one of which includes delivering a first batch of aircraft overweight.

The study is being conducted in the run-up to the F-35 Air System critical design review (CDR 1) in April/May 2004 as weight issues continue to dog the baseline configuration.

While most of the open items from last April's preliminary design review (PDR) are now closed, Lockheed Martin says it is "right in the middle of weight review number four" and adds: "It is no secret we've got tough challenges."

Lockheed Martin F-35 programme general manager Tom Burbage says it is unclear whether weight targets will be achieved by CDR. Although less than 15% of the detailed design of the conventional take-off and landing (CTOL) version by structural weight has been "released", Lockheed Martin expects to reach around the 60% mark by early December and "based on parametric estimates that looks good", adds Burbage.

The company is using a parametric process to predict structural weight and gradually converting it to a known-weight through a series of "bottom-up" reviews, beginning with the CTOL aircraft. After December, the study is expected to include the F-35 short take-off and landing (STOVL) and carrier variants.

If weight remains a problem, Lockheed Martin has the option of an "optimisation design pass". This enables the company to pass initial Block 0/1 flight-test aircraft for assembly at higher than optimum weight to allow flying qualities, flight loads and static tests to begin on time. In addition, "we would know specifically what parts didn't meet the target", says Burbage.

The company is also looking at related options such as an "optimisation design pass" for the STOVL version only, he adds. Lockheed Martin still aims to achieve 80-85% design release by CDR and says first flight of the CTOL remains on track for early November 2005.

Schedule is viewed as a dominant factor for the F-35 Joint Program Office. Program executive officer Maj Gen John Hudson says: "We want to stay on our schedule or close to it."

Some engineers within the F-35 effort are believed to be pushing for a slide in the schedule, estimated at around two to three years overall.


Source: Flight International