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New Huey completes 20k-hr fatigue test

NAVAIR Release

Release Date: 8/01/2003

Press Release Number: E200308011

By John C. Milliman, PMA-276 Public Affairs Officer

NAVAIR PATUXENT RIVER, MD - The Corps' newest utility helicopter, the UH-1Y Huey, attained a rare and important helicopter milestone July 17 - 20,000 hours of fatigue testing.

Representing twice the required 10,000-hour fatigue life of the SuperCobra and Huey, the test took place at the Bell Helicopter test facility at Fort Worth, Texas.

The AH-1Z SuperCobra completed its 20,000-hour test in November.

"This rigorous testing program is required because the new Huey, under the familiar silhouette, is a vastly improved aircraft structurally," explained R. L. Hauk, consulting engineer to Bell's New Product Development Center. "With the addition of the SuperCobra drive train, power plant and rotor system, the aircraft has an additional 1,200 pounds of fuel and maximum useful load of an additional 4,000 pounds. To handle the additional loads, the airframe features full-length, one-piece 'high speed' machined main beams and bulkheads. This feature reduced the part count, fabrication time and distributes additional loads in the airframe structure."

The fatigue testing included low-cycle, or ground-air-ground, tests by placing the structural test article in a fixture and using actuators to place stresses on it in various places to reflect actual load extremes the airframe will experience in flight.

"In the GAG testing, we go to the extremes of the load cycle," explained Bell's Bill Evans, an airframe stress engineer. "From sitting on the ground, to full 3G maneuvers and then back to a hard landing. We essentially ran the most extreme normal flight maneuvers back-to-back for 20,000 (accelerated) hours."

"We started the test April 25, 2001," explained Mark Woods, a Bell structural test engineering specialist. "We used 24 hydraulic actuators, six to position the aircraft in the test fixture and 18 to input the loads to the airframe. During the course of the test, we applied 1.2 million load conditions while monitoring 192 strain gauges."

The purpose of all this testing is determining the life and durability of the aircraft, explained Evans, as well as determining inspection intervals. And proving all of it to the Fleet.

"We want to find out where the problems are, and when they occur," he said. "That way, we'll fix them in production so they won't be problems out in the Fleet. To prove to the Fleet that the aircraft is good for 10,000 hours, we go to 20,000."

Other engineers agree this extensive testing provides real benefit to the Fleet as aircraft platforms are increasing being asked to soldier on long beyond their originally envisioned lifetimes.

"What we have seen out in the fleet," said Bob Ernst, head of NAVAIR's Aging Aircraft IPT, "is that we are charting new waters -- we're going where we've never been before in structures and fatigue life. By investing in proactive approaches like fatigue testing, we can remove some of the wizardry and fix potential problems at a fraction of the cost. This platform will age better and a heck of a lot more gracefully than any of its predecessors because we've been to the back side of the age curve, fatigue-wise, before it's even in production."

Bell Helicopter officials were quick to give credit where it was due.

"This achievement would not have been realized without the hard work of the engineers, mechanics and lab personnel on the floor, maintaining, designing, repairing, and inspecting these test articles," said John Busch, Bell's H-1 Structural Test Articles IPT leader. "These guys have truly taken on a personal attachment to these articles, have worked as a real team and have gained much knowledge for the future."

The team now is in the planning stages of preparing the test article modifications and repairs for the next stage of the UH-1Y's fatigue testing -- high cycle testing, according to Hauk.

The H-1 Upgrades integrated test team here currently has achieved more than 1,284 flight test hours with five aircraft (three AH-1Z and two UH-1Y test aircraft, of which all but one AH-1Z are production representative). Four of the aircraft are currently undergoing modification to incorporate the moveable elevator and the Thales Top Owl helmet mounted display.

H-1 aircraft have totaled more than 27 million flight hours since Oct. 20, 1956 when the "granddaddy" of all H-1's, the XH-40, made its first flight. Since then, more than 16,000 H-1 helicopters have been produced by Bell and its licensees -- making it the most successful military aircraft in aviation history.