UniWest Tie Bolt Inspection System Outperforms Other Testing Methods For Aircraft

Aircraft wheel tie bolts are extremely safety-critical, as they hold the two halves
of the wheel together and must withstand the stress of landing. The landing of
the aircraft, as well as the loosening and tightening of the bolts over time, can
cause them to stretch and eventually crack. Broken bolts on the flight line often
cause delays of departure. That is why airlines continually strive to employ the
best available test methods to locate potential problems in the tie bolts.

Recently introduced, UniWest’s Tie Bolt Inspection System using eddy current
testing (ECT) is now being used by major airlines as well as numerous aircraft
wheel and brake shops that perform testing of aircraft landing gear.

The Tie Bolt Inspection System—which includes UniWest’s US-454A eddy
current instrument, the UniWest Tie Bolt Scanner (US-1779), and specialty probe
US-1839—is used to perform eddy current inspection of the threaded area of
the tie bolt and the underside of the bolt head.

Traditionally, both steel and inconel boltshave been inspected with magnetic
particle or penetrant testing Non-Destructive Testing (NDT) methods. However,
UniWest’s eddy current system was recently adopted by a major wheel and
brake shop in place of three other inspection methods. Independent testing
proved that UniWest’s Eddy Current Tie Bolt Inspection System could detect
smaller flaws than other methods.

Eddy current testing of the threads using the US-1779 also proved more
reliable than some Ultrasonic Testing (UT) methods because of bolt
deformation. That is, since not all bolts are the same, this caused inaccurate or
unreliable readings on certain bolt types.

UniWest’s US-1779 Tie Bolt Inspection System offers other advantages as well.
The twin-roller flatbed allows quick inspection cycles for each bolt. The eddy
current probe included in the system was designed to detect flaws in both steel
and inconel bolts. No other probe is required. The robust probe tested more
than 12,000 bolts during its field trials.

The system also features a go/no-go alarm set that is not dependent on the
operator. The robust and highly sensitive UniWest eddy current probe also has
been proven to detect smaller defects than the other methods of NDT for this
application.

The US-1779 Tie Bolt System also takes up less space in wheel and brake shops
than magnetic particle and penetrant testing systems, enabling the operator to
perform the inspections in the production line, where it best fits for
productivity. A modest 2-foot × 3-foot area with AC power is all that is
needed. Productivity can be increased, smaller flaws can be detected more
reliably, cost is lower, there are no chemicals to be disposed of, and bolts can
be discarded during inspection instead of on the ramp while in service. Finally,
since eddy current testing alone is required, training need only be done for one
method of NDT.

"As of now, the Tie Bolt System is in demand in commercial and military aircraft
industries, as well as wheel and brake shops," noted Mark Gehlen, President of
UniWest, "but this system certainly can be used for other applications requiring
testing of bolt threads."

To learn more, visit www.uniwest.com or call Bryan Leach at UniWest, 509-544-
0720.