F-35 test pilots have begun testing the aircraft’s ability to carry asymmetric external loads in powered-lift flight. The trials are one of the final hurdles before the aircraft embark on the USS America at the end of October for at-sea developmental testing phase 3 (DT3) – the last of three maritime trials that will give the green light for the Marine Corps F-35Bs to deploy onto amphibious assault ships. The trials will explore the aircraft’s ability to operate safely onto decks with a 1,000-lb. asymmetric load as an external store under one of the wings, but not the other.

“In normal high-speed flight we deal with asymmetric loads by adjusting the flight controls,” says BAE Systems test pilot Pete Wilson, but this is not as straightforward when the aircraft enters the powered lift stage of flight just before recovering onto the deck.
Tests have already begun in no-crosswind conditions, and the team are now beginning to test what may occur when stronger crosswinds are introduced. During most carrier landings, ships will point into the wind and the aircraft will be able to recover safely, but at times the ship may be constrained by geography, forcing aircraft to recover with a crosswind component.

The F-35B’s vertical landing crosswind limits is currently 15 kt., although the aircraft can translate at speeds of 20-25 kt. The team want to confirm computer models and prove how the aircraft will operate in such conditions. The issue was rarely a concern for older generations of STOVL, as they did not often bring back such high-tech munitions.

The DT-3 trials have been timed so that the test team can take advantage of rougher seas several hundred miles off the Pacific West Coast to test the aircraft’s ability to operate onto the deck in high-sea states.
The plan is to be able to operate in conditions up to sea state six, equivalent to wave heights of 13-20 ft.
The DT-3 tests will involve several two instrumented aircraft, likely BF-5 and either BF-1 or 4.

The Marines will support the DT-3 trials with a deployable version of Lockheed Martin’s Autonomic Logistics Information System (ALIS) marking the deployable system’s debut on a naval ship. Previous DT trials on the USS Wasp used a less operationally representative version of ALIS system normally used at shore bases.

“This is the first opportunity we have had to actually take it [the deployable ALIS],” said Lt. Col. Richard Rusnok, commanding officer of the Marine Corps’ VMX-22 operational test and evaluation squadron.
“We have used the deployable kit – shore based – and we have an expeditionary environment out to Twentynine Palms, California, and that kind of stuff, but we are going to actually be able to take this deployable kit, load it up and do it like we would for a real deployment.”

With Britain wanting to rebuild its carrier strike capability, the UK plans to begin maritime flight trials of the F-35B from the new HMS Queen Elizabeth in late 2018.
“This will not be a DT phase,” said Wilson.
“Testing on the Queen Elizabeth will be like DTs 1, 2 and 3 combined.”

“We don’t need to use fully instrumented aircraft; we already understand most of the loads on the aircraft systems, as we have tested that during earlier tests,” added Wilson. The trials, off the East Coast of the U.S., are expected to take several months.

The ship rolling vertical landing process, developed for the UK to increase bring-back capability, will also be tested during the 2018 trials. In the first quarter of 2017, a major project will be conducted to “produce a body of work to prove whether or not SRVL is fundamentally safe procedurally,” Wilson says.

The program will fully occupy BAE Systems’ simulator in Warton for between two and three months. Up to 10 STOVL-qualified pilots will be flying simulated SRVLs in combinations of “every load you can fly, day and night, every ambient temperature, pressure, all the wind conditions and ship speeds,” Wilson says. Simulated failures – to brakes, nose gear, computers and helmet-mounted display – will also be included.

The developing SRVL conops involves the jet maintaining a speed of 35 kt. relative to the carrier, which permits bringing the aircraft to a halt with the toe brakes inside 200 m (657 ft.). Wilson expects the difficult parts of the envelope to be aircraft approaching at lower airspeeds in asymmetric configurations. “If we come out of that [simulator trial] looking good, then we know that we’re ready,” he says. “And if we don’t, then we may have more work to do.”