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Yesterday at 12:21 PM
The Navy’s F-35C Has A Major Nose Gear Problem
related:the background: Today at 8:22 AM
The Navy’s F-35C Has A Major Nose Gear Problem
source:More than a decade, the Navy’s catapult launch and barrier recovery (CATOBAR) variant, the F-35C, remains mired with teething issues. Now, one problem appears to be more debilitating than previously realized, and it’s rearing its head at a critical phase of flight for any Navy fighter—the catapult launch.
The issue occurs when a lightly loaded F-35C’s landing gear nose strut is compressed while the jet throttles up, right before launch. As the catapult fires and the hold back bar is released, the jet is rapidly pulled forward, during which time the strut oscillates violently up and down. The bouncing continues as the aircraft proceeds down the catapult track at increasing speed.
The problem was vividly demonstrated among a group of F-35C’s participating in the type’s third set of sea trials aboard the USS George Washington last summer, giving pilots a wild and potentially dangerous ride down the deck.
The airplane seems to be able to take the hammering, but the pilot sitting over the strut can be severely affected by the ordeal. The movement sends their already-heavyand oxygen mask flopping up and down, applying pressure to the pilot’s jaw. The erratic oscillations also keep the pilot from being able to read critical info on their helmet-mounted display, an anomaly that can persist sometime after the jet has departed the deck and entered smooth air.
The issue itself is not new—it has been identified for nearly three years—but that the problem is so persistent and potentially detrimental that a red team has been assigned to address it. So far their recommendation is ominous: If fixes cannot be found, the C model’s nose gear should be redesigned altogether.
The C model is the most expensive of the F-35 clan—costing anywhere from roughly $150 million and $337 million each depending on how you look at it—and it’s the smallest planned production run of the three variants. With the Super Hornet still in production, the Navy never hot on the F-35 idea in the first place, the C model will be the last F-35 to enter service, supposedly in 2019. This date, even if it’s not delayed, isand
Inside defense quotes a Navy document detailing all the factors that have caused the debilitating situation:
"The Red Team believes multiple factors are contributing to the problem, including the pilot's seat restraint and hand-hold (grab bar) locations, the mass and center-of-gravity of the F-35 helmet and display unit, the physical characteristics of the nose landing gear strut (load vs. stroke, damping), and the length and release load of the repeatable-release hold-back bar (RRHB)."
Although catapult launches are already a violent affair, pilots who have been shot off the deck in an F-35C have detailed how disorienting and even painful the whole affair can be.
During at sea trials in August, fleet pilots from VFA-101 evaluated their experience on the “cat” with the F-35C using a rating system, here is what they found out:
“After each catapult operation pilots were asked to assess their pain level on a scale from one to five. Out of a total of 105 catapult shots 74 of those caused pilots "moderate pain" or a three rating. 18 catapult shots caused pilots "severe pain" or a four rating. One catapult shot was deemed a five rating or "severe pain that persists" with the pilot suffering from neck pain and a headache, and 12 catapult shots scored a two rating or "mild pain." None of the 105 catapult shots received a one rating of "slight discomfort" or a zero rating of "no discomfort or pain…” The oscillations shake the pilot's head sufficiently to impair their ability to consistently read flight critical data, which poses a safety of flight risk."
A similar scale of zero to four was used for helmet mounted display readability during each catapult launch. 51 of the launches rated a three where it was difficult viewing anything in the display. Nine received a two rating, where only critical data was able to be viewed. Seven shots received a four rating for not being able to view anything at all inside the helmet mounted display and none got a one or zero rating for being able to easily see all the data or most of the data.
During testing, pilots have had to lock their harnesses tight for launch—not a safe procedure as it could impair their ability to reach the ejection handle should something go wrong during launch, like a “cold” or underpowered catapult stroke.
Obviously all of this is a huge problem in a critical phase of flight, and the Navy’s red team, made up of military and industry personnel, realizes this. Short-term, medium-term and long-term actions, or at least requests for action, are supposedly underway. Short-term recommendations include changing how pilots strap themselves into the jet, and how they hold their straps during catapult launches. Not too enticing of a fix, if you are hurtling yourself off the deck of a carrier at 150 miles an hour in a 25 ton machine, at night, over frigid water.
Medium-term actions include small modifications to the nose gear and HMD symbology, such as simplifying what is displayed in the helmet during catapult launches. These alterations are not set to begin for about another year, after which they will take at least six months to accomplish, and the HMD software may take much longer to change due to the restrictions of the
Long-term actions are not slated to begin until 2019—the same year the jet will supposedly be declared operational—and would take between one and three years to complete. These include changes to the hold-back bar design, and could include alterations to the carrier’s catapult systems themselves to change the amount of compression the nose strut experiences prior to launch. Finally, if these measures don’t fix the problem, a full redesign of the nose gear assembly would be needed. Currently a redesign isn’t being pursued due to development time restraints, and would likely take years to achieve once the process begins. Dramatically retrofitting existing F-35Cs—there will be squadrons in service by that time—would also be a costly affair to say the least.
Since this problem has been an acknowledged issue since 2014, it’s absurd to think that the jet could—and at this point almost definitely would—be declared operational despite such a fundamental flaw. With the F-35 program trying to stick to its timeline and meet goals without asking for another major budget expansion, it seems that major problems are being put off until development has been completed. This completely contradicts the whole purpose of a test and development program, but
Chalk it up as just one of many unsolved mysteries that continue to plague the Joint Strike Fighter family of jets.
