Above: An F-35B Lightning II short take-off/vertical-landing (STOVL) variant of the Joint Strike Fighter is currently undergoing climatic testing at McKinley Climatic Laboratory (MCL) at Eglin AFB. An icing cloud test calibration fixture has been installed within the climatic chamber
Since December 2006, the F-35 Lightning II has surpassed 25,000 combined flight hours with 16,200 hours in F-35 military fleet aircraft and 8,950 hours of system development and demonstration testing. Much of that testing has been conducted by the F-35 Lightning II Integrated Test Force (ITF) assigned to Air Test and Evaluation Squadron (VX) 23, based at Naval Air Station Patuxent River, Maryland.
Operating at a high tempo is routine for the Pax River ITF’s cadre of military, government and contractor testers. In the span of less than six months, they successfully conducted two high-profile test evalutions on opposite coasts of the USA and began preparations for additional high-visibility testing, yet again on both sides of the country.
On September 29, 2014, the ITF deployed a team of 40 testers to the McKinley Climatic Laboratory (MCL), the world’s largest environmental testing chamber. The 96th Test Wing, a US Air Force Materiel Command unit, operates the MCL at Eglin Air Force Base in Fort Walton Beach, Florida. For six months, the Pax River ITF Climatic Test team and key members of the Edwards ITF have capitalized upon the MCL’s proven capability to recreate nearly every weather condition on Earth as they assessed the performance of aircraft BF-05, the short take-off/vertical landing (STOVL) variant, in a wide array of temperatures and meteorological conditions. Testers put the aircraft through extremes such as -40°F/C up to 120°F (48.8°C) and featured wind, solar radiation, fog, humidity, rain intrusion/ingestion, freezing rain, icing cloud, icing build-up, vortex icing and snow.
By placing BF-05 onto a purpose-built frame, test pilots were able to ‘fly’ a standard profile in accordance with defined test sequences. This profile featured a normal start-up, a VSBIT (vehicle systems built-in test) to check the onboard systems, a simulated short take-off, a climb out, full afterburner runs in conventional mode, and a simulated vertical landing. Each meteorological condition was fully tested and featured 60% ground operations and 40% flying, including engine runs and simulated flight in both conventional and STOVL modes. Testers also ensured the collection of accurate and representative data during the icing evaluation by installing additional F-35A and F-35C icing detector probes according to each variant’s design.
“This type of testing doesn’t happen every day,” says US Navy test pilot Cdr Tony ‘Brick’ Wilson. “What the McKinley team has pulled off at Eglin is a real feat of engineering; it’s been a very surreal experience to walk from normal Florida weather into the hangar where it’s like the Arctic and test the F-35. We’ll complete our testing at the end of March 2015 and I’m pleased to say that the findings have been very positive to date.”
Above: CF-05 lands aboard the USS Nimitz during the initial shipboard trials. The F-35C performed its first set of arrested landings and catapult launches
Onboard trials
While some of their teammates were in Florida, an ITF detachment traveled to Naval Air Station North Island in Coronado, California, to board the USS Nimitz (CVN 68) in November 2014. Led by Cdr Wilson and Thomas Briggs, the ITF’s lead flight test engineer for DT-I, their test objective was to conduct a three-week initial shipboard developmental test (DT-I) trial of the F-35C Lightning II, the carrier variant of the Joint Strike Fighter (JSF).
During DT-I, F-35C test pilots and engineers tested both the suitability and integration of the aircraft with carrier air and deck operations in an at-sea environment. The F-35C demonstrated exceptional performance both in the air and on the flight deck, accelerating the team’s progress through the DT-I schedule and achieving 100% of the threshold test points three days early. Test pilots and engineers credited the F-35C’s Delta Flight Path (DFP) technology with significantly reducing pilot workload during the approach to the carrier, increasing safety margins during carrier approaches and reducing touchdown dispersion.
“The engineers responsible for the aircraft’s control laws did a phenomenal job designing this aircraft from the pilot’s perspective,” Wilson explains. “The control schemes of the F-35C provide a tool for the below-average ball flyer to compete for top hook.”
“My major takeaway was that the F-35C is very good at flying behind the ship,” notes Lt Cdr Ted Dyckman, a VX-23 test pilot at the ITF. “Any deviation that someone gets themselves into, they can correct fairly quickly and accurately. In fact, it’s a three-wire machine,” he added, referring to the optimal arresting wire aboard an aircraft carrier.
The DFP capability allowed for 124 arrested landings with zero unintentional hook-down missed attempts to catch an arresting wire on the flight deck, otherwise known as ‘bolters’. (Two hook-down intentional bolters were conducted as part of the DT-I test plan.)
“The flight control system is precise, stable and responsive, and provides carefree handling in all flight regimes,” says Cdr Christian Sewell, the VX-23 F-35 operational test liaison officer/ITF operations officer. “We’ve tested right up to the edge of the envelope and the aircraft handles amazingly. In general, the pilot workload required to fly the F-35 is less when compared with legacy aircraft, which allows the pilot to focus on the operational mission.”
Above: The F-35 Lightning II Pax River Integrated Test Force from Air Test and Evaluation Squadron (VX) 23 has ferried aircraft BF-05 to Eglin AFB to undergo climatic testing
Tailhook design
The three-wire landings during DT-I also demonstrated the successful redesign of the F-35C’s tailhook and supporting structural interfaces. The joint contractor and government team consisted of engineers from NAVAIR’s Systems Engineering, Air Vehicle Engineering and Support Equipment & Aircraft Launch & Recovery Equipment departments, the Atlantic Test Range (ATR) and Pax River ITF, and Lockheed Martin Aero, Northrop Grumman, and Fokker Landing Gear.
The tailhook redesign effort, like the flight control system, is an example of the power of collaboration between government and industry engineers. In both cases, industry was able to leverage NAVAIR’s decades of experience in carrier-based aircraft design to build an outstanding product for the warfighter.
“Since beginning shore-based carrier suitability testing in January 2014 with the redesigned hook system, test results have been positive, with the ultimate proof coming in the success of DT-I,” says Bryan Racine, F-35 ship suitability team lead.
“We had stricter weather requirements when we were here. As we got into testing, the weather started coming down,” Dyckman says. “We had such confidence in how the airplane was flying that we lowered the weather minimums to what the fleet is actually using, knowing that when I lower my hook and come into the groove, I’m going to trap.”
Dyckman adds that the test team’s confidence level in the aircraft was so high that they were ready to evaluate the aircraft for night operations. “It flew very well behind the ship, even
on the darkest night,” he says. “Two hook-down passes and two traps: that says it all right there. It’s unheard of to conduct night ops on the first test detail.”
During DT-I, F-35C maintenance and ground operations integrated well with standard Navy carrier procedures aboard Nimitz.
“All of the flight deck crew members involved in DT-I were assigned to Nimitz, some of whom went to NAS Patuxent River in mid-October for training,” Wilson explains. “They returned to the ship and prepared the remainder of their crew for the arrival of the F-35C. The initial ship trials of the F-35C would not have been possible without the cooperation of Nimitz.”
After all test points are collected, analyzed and assessed, the DT-I data will be used to advise the Navy of any adjustments necessary to ensure the fifth-generation fighter is fully capable and ready to deploy to the fleet.
“Our main testing points were to verify that the approach handling qualities were satisfactory across a variety of wind conditions; to determine the launch characteristic and performance from the ship’s catapults across a variety of wind conditions; to look at the integration of the aircraft with the ship, both on the flight deck and in the hangar bay; and to test the ability of the F-35C to use other ships’ flight systems to perform inertial alignments, instrument approaches, and basic navigation to and from the ship,” says Cdr Shawn Kern, the director of test and evaluation for F-35 naval variants. “We also performed some aircraft functions in and around the shipboard environment, including use of various sensors and fuel dump testing.”
Above: The F-35C Lightning II carrier variant conducted its first carrier-based night flight operations aboard a US Navy aircraft carrier in November 2014
Runway trials
As team members returned to the ITF from their highly successful detachment aboard the Nimitz, they began to finalize preparations for wet runway and crosswind testing at Edwards Air Force Base and Naval Air Weapons Station China Lake in March 2015; and ski jump testing at Pax River in May 2015.
To date, 158 F-35 pilots and more than 1,650 maintainers have graduated from training at Eglin AFB, while the F-35 has completed multiple weapons tests as well as F-35B and F-35C first-life durability testing.
Additionally, the program has conducted two F-35B DT shipboard trials aboard the USS Wasp (LHD 1) and two more shipboard trials are anticipated in 2015 – the F-35B will conduct its first operational test and the F-35C will conduct its second DT event. As the F-35 progresses through all of these test events, the initial operational capability (IOC) milestone dates published in 2013 continue to be on target. The F-35A is set to reach its IOC milestone by December 2016; the F-35B is expected to reach its IOC milestone by July 2015; and the F-35C is anticipated to reach its IOC milestone by February 2019.
Sylvia Pierson is the F-35 Lightning II Patuxent River Integrated Test Force (ITF) public affairs officer
