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	This schematic drawing of the lifting device shows auxiliary reels for electric power cords and air hoses (red), and the ball-and-socket support frames (blue) that attach to ordnance hard point located on the bottom of the wing.

A U.S. Air Force program, known as Falcon STAR, requires every F-16 in the fleet to undergo a series of maintenance operations. One major operation involves replacing the wing attachment fittings that mount the wings to the fuselage.

Background

The previous wing removal and installation process used a mobile crane and a three-point sling to lift and support the wing from overhead when it was detached. The sling arrangement was rigid — the lengths of the cables were fixed — but the suspended wing swung freely and had to be maneuvered into place by moving the crane.

A team of engineers from Southwest Research Institute (SwRI) and Hill Air Force Base and mechanics from the Ogden Air Logistics Center (OO-ALC) developed a new, mechanized system of suspending and transporting the wings that not only eliminated the need for a crane, but also saves time and requires fewer personnel during the attachment and removal procedures.

SwRI engineers responded to a request from engineers and mechanics at Hill Air Force Base, Utah, for a process analysis study and a conceptual design for a new wing manipulation tool that would eliminate the need for a crane to remove and install F-16 wings.

Wing Removal/Installation Solution

	Finite element analysis of main load bearing element.

The SwRI and Hill AFB team conducted a cost analysis based on data from time studies of the existing processes.

With input from Hill AFB and associated personnel, the SwRI team designed a manipulator tool that would feature:

• Six degrees of freedom

• Electrically powered movement in two directions

• Fine positioning capability using hand cranks

• High maneuverability

• Fail-safe operation

The team considered factors such as:

• Controllability

• Cost

• Manpower

• Operator skill level

• Process improvements

• Technical risk in the design phase

The final design addressed the established system requirements.

Results/Outcome

	The manipulator tool successfully removed and installed the wings of the F-16 airplane. View the video Windows Media or QuickTime

At Hill AFB, the manipulator tool successfully removed and installed several wings in a fraction of the time needed with the crane and sling. The new manipulator tool supports the wing so accurately that, when the final bolt is removed from the fuselage and the sealant is removed, the wing stays perfectly stationary. With the sling method, the crane operator had no feedback to indicate how much of the wing's weight was being supported during removal, and when the last bolt was removed, the wing would often pinch the bolt in the hole, causing potential damage to fracture-critical parts.

For wing installation, the manipulator tool allowed alignment of the wing to the fuselage so accurately that the attachment bolts could be pushed through the holes with very little effort. In fact, the wing may now be dry-fitted and aligned to the fuselage prior to applying sealant. This eliminates another common problem of the sling method, involving the creation of fuel leaks due to smearing of freshly applied sealant during wing installation. In addition to the above process improvements, quality and safety have been improved by removing the crane from the process.

Early indications are that the SwRI-developed wing installation and removal tool has provided improvements in time, precision, labor and safety compared to the existing method. Once the evaluation of the initial tool has been completed, additional units will be ordered from independent manufacturers using design documents supplied by SwRI under terms of the project. With minor modifications, the system also could be applied to aircraft other than the F-16, increasing the utility of the new manipulation tool for both military and civilian applications.

For more information about wing removal/ installation tool capabilities at SwRI or how you can contract with SwRI, please contact Clay Flannigan at wflannigan@swri.org or (210) 522-6805.
 

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Southwest Research Institute^® (SwRI^®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 12 technical divisions.

November 12, 2009