September 6, 2001 (by Lieven Dewitte) - Lockheed Martin Aeronautics Company recently completed the first phase of flight testing of its new conformal fuel tanks (CFTs) for its F-16 multirole fighter.
Conformal Fuel Tank (CFT) testing (#87353). [LMTAS photo]
Flight testing with aerodynamic shapes was conducted on an F-16C at Eglin Air Force Base, Fla., from March through August. A total of 24 test flights and 65 flight test hours were accomplished, and testing involved loads, flutter, and stability and control.
Lockheed Martin puts a lot of effort to it in response to international market demands for more range and payload. CFTs have become a very popular option in recent orders and new business pursuits.
Lockheed Martin began F-16 flight demonstration of an initial CFT shape in 1994 to investigate performance and handling quality characteristics. Subsequent wind tunnel testing led to the current external lines, which were initially validated in flight testing of high angle-of-attack handling characteristics at Edwards AFB
, Calif., last year.
"The flying qualities of the F-16 with CFTs are essentially unchanged when compared to a non-CFT equipped airplane," said Stephen W. Barter, chief F-16 test pilot and company CFT project pilot. "For most combat flight conditions, it's as if the CFTs are not even there. The surest way for me to tell if CFTs are installed is to look over my shoulder."
"The CFTs have very little adverse affect on the F-16's renowned performance," said Maj. Timothy S. McDonald, U.S. Air Force project pilot for CFT testing at Eglin. "The aircraft retains its full 9-g capability and flight envelope with the CFTs installed. The drag impact is very small - less than one percent in combat configuration at cruise conditions."
Barter and McDonald will be presenting results of the CFT flight testing at the annual Society of Experimental Test Pilots symposium in September in Los Angeles.
A shipset of two CFTs provide a total of 440 U.S. gal, or approximately 3,000 lbs of additional fuel for the F-16. The extra fuel can significantly extend mission range, time on station or time engaged in combat. This range/persistence enhancement is very valuable for countries that do not have tankers for aerial refueling. For countries that do have tankers, CFTs can reduce the tanker offload demand and extend the fighter's penetration distance
CFTs also increase the F-16's payload flexibility. For medium range air-to-surface missions, CFTs can eliminate the need for wing tanks. This allows doubling the F-16's primary weapon capacity and flying with two, rather than one, types of large weapons in a balanced configuration.
F-16 CFTs are located on the upper fuselage surface, which significantly reduces stores recertification requirements and the associated costs. The upper surface arrangement allows the CFTs to be relatively light weight because nothing is suspended from them. The CFTs do not interfere with daily inspections and servicing and can be removed or installed in about two hours.
The test aircraft has been returned to Fort Worth and has been fitted with the first functional set of CFTs. Ground systems testing of fuel transfer will begin this month, and functional flight testing is scheduled to begin in late October. Flight testing will be conducted at both Fort Worth and Eglin.