LOCKHEED MARTIN has installed a stick shaker on the C-130J because of undesirable stall characteristics caused by the improved Hercules' new propulsion systems.
Micky Blackwell, president of Lockheed Martin's Aeronautics sector, says attempts to find an aerodynamic solution to the problem have been shelved after "extensive testing", but will be resumed following US civil certification of the transport aircraft, now scheduled for September.
Blackwell says the unplanned flight tests of "vortex generators, fences and stall strips" are partly responsible for the year-long delay in certification of the C-130J. The programme was already behind schedule because of delivery problems with some subcontractors.
The Lockheed Martin executive cites a "serious setback" with the liquid-crystal displays (LCDs) for the new digital cockpit. Lockheed Martin has switched LCD suppliers, from Litton Systems Canada to ADC of Atlanta, Georgia.
Blackwell says the stall problem is caused by interaction of the wing with the C-130J's new six-bladed Dowty propellers. The flow field from this propeller is "very different" to that produced by the Hamilton Standard four-blade unit on previous Hercules, he says.
"The interaction is far more extensive than was thought, and the stall characteristics are very different," he says. Efforts were made to fix the problem but, because of the earlier delays, "...we did not have time to get there aerodynamically. We put a stick shaker in instead, but are committed to come back to the issue later, after certification."
Blackwell says negotiations continue with the UK and Australia on compensation for the late delivery of their C-130Js.
Initial deliveries are scheduled immediately following US certification.
See News Analysis, P28.
Source: Flight International
