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The whole purpose of this series of tests was to try to exercise the arresting gear in the most punishing ways. One way that's usually done is to try to arrest
by euler_angles 3y ago
The whole purpose of this series of tests was to try to exercise the arresting gear in the most punishing ways. One way that's usually done is to try to arrest far off the centerline (where the arresting force will be applied far more intensely to one side) and also to try to have the arresting hook grab the wire while the jet is still wheels above deck (this slams the aircraft down, HARD)
After this incident it was determined that we had fulfilled the intent of the test plan.
Also, instrumented aircraft capable of doing arrestments were in short supply: the program only had two of them, and we pushed one to its very limit.
- jessriedel 3y ago> After this incident it was determined that we had fulfilled the intent of the test plan. Ok, so it was considered good enough? (This quote made it seem like the testing had failed and they were giving up: "The program decides to officially stop trying to chase the off-center arrrestments and wire only arrestments.) Also, I still don't understand what wire-only arrestments are. Aren't all arrestments wire only? Thanks.
- hbrav 3y agoI think "wire only" means the hook catches while the wheels are still off the deck. I suppose that hard landing might have, in some ways, replicated the hard slam-down this would produce. Author, is that the case? Was the hard landing judged to have been a decent proxy for the wire-only arrestment?
- bronson 3y agoSeems unlikely. One is slamming due to a heavy glideslope. Two is slamming due to a serious yank on the rear section. The airframe stresses and flight dynamics will be different.
- euler_angles 3y agoYeah, dynamics will be different, though caveat I am not a structures/loads engineer. I just don’t think anyone had the risk appetite to chance a test asset against a very difficult to achieve test point.
- hef19898 3y agoIt is also fair to assume the decision to not do additional testing of wire-only arrests was well analyzed by the respective engineering teams. Program management does not take decisions like this by themselves.
- euler_angles 3y agoAbsolutely. We had a whole carrier suitability team full of people who lived and breathed this stuff. It was just my responsibility to make sure the aircraft instrumentation system got them the data they needed, at a high enough quality, to empower their analyses and decision making process.
- werrett 3y agoBased solely on the above description -- wire-only is when you don't have wheels on deck, also slowing the craft down.
- jessriedel 3y agoGot it, thx!
- ferfumarma 3y ago> Ok, so it was considered good enough? (This quote made it seem like the testing had failed and they were giving up: "The program decides to officially stop trying to chase the off-center arrrestments and wire only arrestments.) Kind of both: it was too dangerous to test a wider range of parameters, and the testing was therefore "successful" because it was crystal clear that going beyond the point where they had the problem would not be safe. So in this case "giving up"/stopping and "determining the limits of the landing envelope, were reached at the same time.
- bombcar 3y agoI assume wire-only means no reverse thrust and no brakes.
- jessriedel 3y agoNo, aircraft land on carriers while applying full forward thrust and (I am 99% sure) no wheel brakes. The idea is that if the wire fails to catch they "bolter", i.e., do a touch-and-go, so they can come around for another landing attempt. (If they stopped or reversed thrust and the wire didn't catch, they'd end up in the drink.) Based on other comments (or re-reading the authors comment carefully), it turns out that "wire only" mean that the wire catches before the wheels touch the ground. (This puts additional strain on the wire and airframe.)
- wolverine876 3y ago> no wheel brakes There are brakes on the wheels (that can slow a plane moving at flying speed)? That's a lot of force. I assumed the wheels merely prevent friction between the plane body and the deck, and the engines and control surfaces, and the wire, did the braking.
- ambichook 3y ago"no wheel brakes" here means that the brakes aren't engaged, as stated so that if the aircraft misses the wires it can touch and go without drowning the pilot and destroying an $80m aircraft
- jki275 3y agoAll planes have wheel brakes, including naval aircraft. But in an arrested landing the wire stops the plane, not the brakes.
- jki275 3y agoYou're correct, no wheel brakes and throttle to full as soon as the wheels touch. If the cross-deck pendant snaps, the engines don't have time to throttle up before you go over the edge. And of course if you don't catch a wire you really don't want to be trying to stop. No reverse thrust in carrier aircraft.
- jessriedel 3y ago(BTW, the twitter link on your blog is mistakenly going to twitter.com. I think you meant to link to your account: https://twitter.com/the_engi_nerd https://twitter.com/the_engi_nerd Cheers!)
- euler_angles 3y agoOh, thanks for the spot. Not sure why it's doing that...
- euler_angles 3y agoFixed