GRAHAM WARWICK /WASHINGTON DC
Modification promises to improve climb performance of heavily loaded Hercules gunshipUS Air Force special operations forces are to evaluate wingtip tanks as a means of improving the performance of its heavily armed Lockheed Martin AC-130 gunships. The tip tanks have been designed by Hercules modification specialist Snow Aviation, which has received a $5.9 million contract to modify and flight test an AC-130H.
The tip tanks replace the AC-130's underwing tanks, providing the same fuel capacity, but improved aerodynamics. "The tank hangs below the tip and acts as an endplate for the wing," says president Harry Snow. The tanks reduce induced drag and improve climb performance, he says. Moving the tanks outboard also provides greater wing bending relief.
Funding will allow Columbus, Ohio-based Snow to complete computational fluid-dynamics modelling and perform windtunnel and flight testing of the wingtip tanks. The USAF will provide an AC-130H for modification. Baseline flying is scheduled for February, with tank installation and flight testing to be completed by the end of June.
Snow says installation of the wingtip tanks requires extension of the ailerons, to restore roll control power; and the rudder, to provide adequate yaw control in the event of an outboard engine failure on a heavy take-off.
The tip tanks are part of Snow's "C-130M" modification package, which includes a new two-crew cockpit, fuselage stretch and re-engining with 3,780kW (5,070shp) Pratt & Whitney Canada PW150A turboprops. Snow says a potential customer is looking at the C-130 re-engining, which requires substantial modification of the wing due to the higher power and new eight-blade propellers. The new nacelle is shorter, and a 1.5m (60in) fuselage plug forward of the wing restores balance while housing a sixth cargo pallet.
Snow is continuing work on a programme to re-engine the Cessna T-37B twinjet trainer. Although the company has yet to secure a customer, Snow says Williams International FJ33 turbofans will be installed in a T-37 for flight testing. "Williams has just finished certification of the FJ33, which is what we were waiting for," he says. "First flight is at least a year away."
Meanwhile, Lockheed Martin has completed "austere field testing" of the CC-130J Super Hercules transporter. The CC-130J, an extended- fuselage version of the C-130J, conducted the tests at Tyson Airfield in Yuma, Arizona, which was selected as it is considered representative of war zone landing conditions. The aircraft landed at a weight of 61,300kg (135,000lb) on dirt runways in less than 610m (2,000ft).
Source: Flight International
