Last week the Pentagon’s Office of the Director, Operational Test and Evaluation (OT&E) released its annual report that contains critical findings on the progress of several key military rotorcraft programs including the Boeing-Leonardo MH-139 Grey Wolf, Boeing CH-47F Block II Chinook, and Sikorsky CH-53K King Stallion.
On the MH-139, OT&E noted that only three of the necessary eight STCs required for full military flight test had been received, limiting testing prior to a key program milestone decision early this year. What testing that has been performed has raised concerns at OT&E. Specifically, “MH-139A deficiencies identified in ground and flight testing to date continue to represent a risk to MH-139A meeting operational effectiveness requirements. Newly identified concerns include the certified envelope of the automatic flight control system not matching the expanded envelope of the aircraft, sensor display availability to the crew in the cabin, and intercommunication system deficiencies.”
Previous year OT&E concerns remain unresolved including “capability of the cabin layout to support employment of armed tactical response forces, as well as flight manual restrictions
on takeoffs in crosswinds or near obstacles.” The report also noted that, “International users of the AW139 recommended changes including the type of hoist, the location of the fast-rope insertion/ extraction system bar, and other cabin configuration changes.”
OT&E also warned that “the [USAF] program office needs to address several challenges for the MH-139A to be operationally suitable” including “expansion of the MH-139A operating envelope relative to the commercial AW139 baseline may stress powertrain components and increase maintenance requirements” and act upon “collected observations from international users of the AW139 recommending routine corrosion-prevention measures to minimize long-term airframe maintenance” and “potential reliability shortfalls of the installed hoist system.” Other deficiencies included the “contractor-provided mission planning system” and an “original contractor-proposed fuel cell design [that] did not meet the required military standard for vendor qualification against a particular threat.”
The revised Boeing CH-47F Block II program will not meet its high/hot performance goals, according to OT&E, largely because Boeing and the Army have been unable to fit the helicopter with advanced rotor blades due to “unresolvable vibration issues.” However, the program is progressing utilizing the legacy fiberglass blades and a “number of system improvements including an improved power train and rotor system, software and avionics upgrades, and a redesigned lightweight fuel system.”
OT&E concluded that, “the CH-47F Block II should be able to improve performance at lower altitudes and cooler temperatures using the fiberglass rotor blades. Current analysis shows that the CH-47F Block II will not be able to meet its performance requirements at high altitudes and in hot conditions in this configuration.” It also encouraged the Army to perform dynamic ballistic testing of the legacy rotor blades, originally planned in 2003, but never conducted.
OT&E summarized that, although the future of the program was “uncertain,” test working groups continue to meet but have not resolved several key outstanding issues including ballistic testing of the new lightweight, self-sealing fuel system. “The fuel cell failed qualification testing and experienced other issues during testing in FY21,” OT&E said.
While the Sikorsky CH-53K King Stallion’s “testing was adequate [for] operational effectiveness and suitability, aircraft survivability equipment testing was not adequate” and “the Navy’s test design was insufficient to acquire the necessary data,” OT&E said, adding, “Without additional data pertaining to the simulated threats and system performance, aircraft survivability cannot be determined.”
Among other things, OT&E found that, although the aircraft has been flying since 2015 and has been operational since last year, “operations did not assess CH-53K secondary missions ofair evacuation, forward arming and refueling point operations, air delivery, or rapid insertion and extraction operations.” That testing is scheduled for later this year. Other items noted by OT&E include the fact that the program will not deliver a structural repair manual until FY2025 and that troop transport missions with 30 combat-equipped troops was not conducted down to minimum fuel due to “incomplete aircraft center of gravity developmental testing.”