Test Report Points to F-35’s Combat Limits
With thanks to:
Aviation Week & Space Technology
The Block 2B version of the F-35 Joint Strike Fighter, which the Marine Corps declared operational in July last year, is not capable of unsupported combat against any serious threat, according to Michael Gilmore, the Pentagon’s director of operational test and evaluation (DOT&E). In a 48-page annual project report to be published shortly, a copy of which was obtained by Aviation Week, the DOT&E states that “the F-35B Block 2B aircraft would need to avoid threat engagement… in an opposed combat scenario, and would require augmentation by other friendly forces.”
Most of the same limitations will apply to the U.S. Air Force’s initial operational capability (IOC) version, the F-35A Block 3i. “Since no capabilities were added to Block 3i, only limited corrections to deficiencies, the combat capability of the initial operational Block 3i units will not be noticeably different.”
The report is “factually accurate,” the F-35 Joint Program Office concedes in an official response, but “does not fully address program efforts to resolve known technical challenges and schedule risks.”Lockheed Martin said it endorsed the program office’s views.
Giving more details on the software deficiencies mentioned in a December memo, Gilmore says 11 out of 12 weapon delivery accuracy (WDA) tests carried out during Block 2B developmental testing “required intervention by the test and control team to overcome system deficiencies and ensure a successful event,” Gilmore says that the F-35’s performance in combat “will depend in part on the operational utility of the workarounds” that were used in testing.
At the root of the difficulties in the WDA tests, Gilmore said, was that component tests in the run-up to the WDA events were focused “on contract specification compliance, instead of readiness for combat.” Those tests required only that the subcomponent should work. The actual WDA tests involved the entire kill chain and “highlighted the impact of deficiencies.” The F-35 program leadership altered some of them to achieve a “kill” – for example, by restricting target maneuvers and countermeasures.
Also, the Marines accepted several substantial flaws in their IOC standard, causing problems with the way that the “performance and accuracy of mission systems functions,” including the aircraft’s data fusion system and radar performance, were displayed to the pilot.
Specific technical problems continue to impose speed and maneuver limitations on the F-35, the report says. The weapon bay temperatures exceed limits during ground operations at on days warmer than 90-deg. F, and at high speeds below 25,000 feet, if the weapon bays are closed for more than 10 min. (The F-35 is not stealthy with the doors open.) On the F-35A, the time limit is applied at speeds from 500 to 600 kts, depending on altitude.
Heating issues were identified several years ago, but were said to have been addressed with a more efficient fuel pump and other changes: the F-35 uses the fuel as a heat sink to cool the airframe interior and systems, but runs short of cooling capacity under some circumstances. When Air Force operators at Luke AFB, Arizona, announced in December 2014 that they had painted fuel trucks white to reduce the heating problem, the program office stated: “This is not an F-35 issue. There are no special restrictions on the F-35 related to fuel temperature.”
All F-35s are currently subject to g restrictions with full internal fuel. This is due to a problem where air enters a siphon fuel line and causes pressure in an associated tank to exceed limits. A repair scheme is in the works.
Overall, the report says, “the rate of deficiency correction has not kept pace with the discovery rate” – that is, problems are being found in tests faster than they can be solved. “Well-known, significant problems” include the defective Autonomic Logistics Information System, unstable avionics and persistent aircraft and engine reliability and maintainability issues.
Combined with poor aircraft availability, this record leads DOT&E to conclude that the program cannot speed up flight testing enough to deliver Block 3F – the IOC standard for the Navy and export customers and the exit criterion for the systems development and demonstration (SDD) phase – on schedule. Block 3F developmental flight testing started 11 months late, in March 2015. The planned 48 WDAs in Block 3F – most of them more complex and challenging than the Block 2B weapons tests – cannot be accomplished by the May 2017 schedule date “unless the program is able to significantly increase their historic completion rate.”
Moreover, DOT&E predicts, the fleet of production-representative, instrumented aircraft required for initial operational test and evaluation (IOT&E) – the service-led testing that follows SDD and precedes the declaration of operational capability – will not be ready before August 2017. The IOT&E force will then use these for “spin-up” and training before IOT&E starts, which Gilmore does not now expect to happen before August 2018.
An essential element of IOT&E is a high-fidelity simulation of threats and scenarios too complex to be addressed in live testing. Gilmore has been warning for several years that the program’s own Verification Simulation (VSim) subsystem was flawed and behind schedule. In August 2015, in an unannounced move, VSim was cancelled outright (after $250 million in added investment from 2010 onwards) and will be replaced by a government-led Joint Simulation Environment. But this will not be ready in time for IOT&E, so testers will either have to skip those scenarios or add costly and time-consuming live tests to the program.