Sikorsky begins CH-53K structural integrity testing

Structural integrity testing on the CH-53K heavy lift helicopter’s airframe has commenced as part of a three-year programme to validate the aircraft’s ability to operate safely over its entire flight envelope of 44,000 pounds empty gross weight up to its maximum gross weight of 88,000 pounds with external load.

The tests are being conducted by Sikorsky as required by the Naval Air Systems Command. Sikorsky is developing two non-flying CH-53K test articles, five prototype and four production-representative heavy lift helicopters as part of a $3.8 billion System Development and Demonstration (SDD) contract for the US Navy.

Mike Torok, Sikorsky's CH-53K program vice president, said: ‘The Static Test Article will enable Sikorsky to replicate the many stresses, strains and aerodynamic forces the CH-53K helicopter will experience during all aspects of flight, whether the aircraft is empty, filled with cargo, or carrying up to 36,000 pounds of gear suspended beneath the aircraft by an external sling.

‘By placing incrementally heavier static loads on various parts of the airframe assembly - including those well beyond the airframe's analytical design strength - we can measure structural integrity, airworthiness and crash worthiness, and verify safety margins for all expected operational conditions.’

The Static Test Article consists of the cockpit, the cabin, fuel sponsons, a transition section and the tail rotor pylon. The complete airframe assembly is suspended off the ground by the shaft of its main rotor gearbox. Surrounding support beams hold the numerous hydraulic cylinders that apply the flight and inertial loads to parts of the airframe assembly. Also attached to the STA structure are component-representative weights that simulate the presence of the engines and landing gear, among other key subsystems and components.

Six test conditions on the Static Test Article have been completed during 2013 and 2014.

The first four test conditions satisfy pre-flight requirements ahead of a CH-53K flight test aircraft taking its first flight later this year. Replicating the maximum load conditions encountered while in flight, the four pre-flight tests measured the structural strength of the tail rotor pylon during high and low speed flight manoeuvres, the landing gear during impact with the ground, and the full airframe structure while under maximum rotor power. 

Sikorsky will continue to test the structural integrity of the CH-53K Static Test Article for another two years to validate the effects of aerodynamic forces and weight distribution on different sections of the airframe.