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Psion posted:I doubt anyone with actual knowledge of the reqs would say, but thankfully I'm a fully qualified armchair poster: Getting shot at while in a helicopter has always seemed like a real bad plan to me.
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Jan 31, 2022 20:25
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but my armchair posting ...  Seriously though, good find. I wonder how many of those bullet points were copy/pasted from the program which didn't end up producing the Comanche? it's not like building some LO characteristics into helicopters is a new idea.
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Jan 31, 2022 20:28
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Psion posted:but my armchair posting ... I only skimmed it but I thought it was funny that most of the 30 pages of requirements and performance criteria seemed like pretty basic stuff because if they don't say an attack helicopter needs to fly and shoot things they'll get sued by a company pitching a kite. Reminds me of when the Royal Navy wanted catapults on their new carriers and the shipbuilder basically said "You were serious about that? I mean, we can put them in, but it would be cheaper to build a new carrier"
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Jan 31, 2022 20:45
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Jonny Nox posted:Sitting at the gate in a MAX in 45kph winds. 24 knots? pfeh, i've landed a 152 in that steady and straight down the runway
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Jan 31, 2022 21:21
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Cat Hatter posted:I only skimmed it but I thought it was funny that most of the 30 pages of requirements and performance criteria seemed like pretty basic stuff because if they don't say an attack helicopter needs to fly and shoot things they'll get sued by a company pitching a kite. Not making assumptions about what is obvious to everyone is systems engineering 101. Poorly developed requirements are a huge problem in defense contract though getting much better in the past 15 years.
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Jan 31, 2022 22:33
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MrYenko posted:I’d love to hear thoughts from Ambilical Hexnut, but I’d bet a dollar that Defiant is combining a coaxial rotor system with multi-speed rotor systems that have started to gain traction. Lower rotor rpm is surely going to lower the speed at which retreating blade stall happens? It will however increase the speed at which advancing blade tip goes supersonic
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Feb 1, 2022 01:46
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I thought the whole point of coaxial helicopters is that you don't need to worry about retreating blade stall because there's an advancing blade right above or below it?
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Feb 1, 2022 02:02
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Cat Hatter posted:I thought the whole point of coaxial helicopters is that you don't need to worry about retreating blade stall because there's an advancing blade right above or below it? I thought the point of coaxial rotors was so that you weren’t torqued around by the rotor spinning in one direction?
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Feb 1, 2022 02:30
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Murgos posted:I thought the point of coaxial rotors was so that you weren’t torqued around by the rotor spinning in one direction? In a broad sense, yes thats why something like a Chinook has two rotors. I should have said "in the context of this competition to make faster helicopters" where to get around retreating blade stall you have the option of two rotors so each side has advancing blades or a tilt-rotor so there isn't a retreating blade.
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Feb 1, 2022 02:40
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I wanna see the tail-boom on the worst Chinook, where both main rotors spin the same way.
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Feb 1, 2022 02:48
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Murgos posted:I thought the point of coaxial rotors was so that you weren’t torqued around by the rotor spinning in one direction? Based on DCS blackshark and huey it’s actually because sometimes the designers don’t think there are enough ways to kill you.
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Feb 1, 2022 05:12
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Cat Hatter posted:In a broad sense, yes thats why something like a Chinook has two rotors. I should have said "in the context of this competition to make faster helicopters" where to get around retreating blade stall you have the option of two rotors so each side has advancing blades or a tilt-rotor so there isn't a retreating blade. Coaxial rotors eliminated the need for a tail rotor. You still have issues with RBS and compressibility. The tail-pusher means you can have a completely different blade profile and I assume, rotorhead/swash assembly, which creates a profile that largely eliminates RBS and delays compressibility....I think. Or maybe they can run much lower RRPM and again delaying all the issues?. I got a frigging CPH(H) and I have no clue 
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Feb 1, 2022 05:52
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hobbesmaster posted:Based on DCS blackshark and huey it’s actually because sometimes the designers don’t think there are enough ways to kill you. I love that the Ka-52 has an ejector seat because why the hell not  Just pray those charges to blow the blades off work!
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Feb 1, 2022 06:28
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priznat posted:I love that the Ka-52 has an ejector seat because why the hell not if you're at the point of having to use it, your odds aren't really worse if they fail, right? but yeah I first heard about that and thought "that's cool!" and then "wait a minute...only if it's reliable..."
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Feb 1, 2022 08:02
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Psion posted:if you're at the point of having to use it, your odds aren't really worse if they fail, right? True, if you’re crashing anyway.. Or about to explode, I wonder if autorotation might be preferable in most cases.. Tougher without the tail rotor for yaw control in a coaxial setup I believe?
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Feb 1, 2022 08:16
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priznat posted:True, if you’re crashing anyway.. Or about to explode, I wonder if autorotation might be preferable in most cases.. Tougher without the tail rotor for yaw control in a coaxial setup I believe? Not really. You still 2 big spinning things on top.
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Feb 1, 2022 08:36
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Some good aeronautical insanity https://twitter.com/Reuters/status/1488526300692115456 *extreme making GBS threads noises*
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Feb 1, 2022 20:32
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Bit of a tail strike too. Could have done without the color commentary tho. OOOOOOH MA GAWWWWDDDD EAAASY!!! EASSSSY!!!!! e: https://twitter.com/BGrueskin/status/1488585647132610560?s=20&t=YCVuK6ESCaE6PXMsjevRRQ slidebite fucked around with this message at 21:43 on Feb 1, 2022 |
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Feb 1, 2022 21:05
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I think that guy is what train engineers call a "foamer."
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Feb 1, 2022 21:44
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To be perfectly frank, if I wasn't already an air and space dork who had read articles about it, and somebody came up to me right now and said "yeah I'm in the military, I'm a Guardian in the US Space Force" I would probably be like lol yeah bro I play Halo too
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Feb 1, 2022 21:47
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ImplicitAssembler posted:Coaxial rotors eliminated the need for a tail rotor. You still have issues with RBS and compressibility. The tail-pusher means you can have a completely different blade profile and I assume, rotorhead/swash assembly, which creates a profile that largely eliminates RBS and delays compressibility....I think. I'll admit that practically everything I know about helicopters I learned from Smarter Every Day and am welcome to being schooled on helicopter design. They have a short video about how helicopter speed is self-limiting (link to the spot: https://www.youtube.com/watch?v=_pbdwueqGp4&t=203s) and have a throwaway line at the end about how yes, the main reason a helicopter would have a second rotor is to eliminate the tail rotor, but it has the side effect of allowing the helicopter to have a higher top speed and you end up with a cargo helicopter (Chinook: 196mph) that can go faster than an attack helicopter (Apache: 182*). If you're actually designing for top speed, you can add the pusher prop and you get the Sikorsky X2 prototype that can do 290mph because, as you said, it lets you do weird poo poo with slowing down the main rotor but they're both important pieces of the puzzle. I see Sikorsky had a similar prototype in the 70s but with a pair of turbojets instead of a pusher prop that could do 303mph but suffered from "excessive fuel consumption". Also, while looking all that up, I read that the rotor hub itself has 10-20 times the drag of the blades, so the big/weird hubs on the Defiant are supposed to reduce that by 40% and I thought that was neat. *I'm using Wikipedia's "Maximum Speed" because I don't have a better source and they don't list a "Never Exceed Speed" for a Chinook. Cat Hatter fucked around with this message at 22:42 on Feb 1, 2022 |
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Feb 1, 2022 22:37
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Cat Hatter posted:I'll admit that practically everything I know about helicopters I learned from Smarter Every Day and am welcome to being schooled on helicopter design. They have a short video about how helicopter speed is self-limiting (link to the spot: https://www.youtube.com/watch?v=_pbdwueqGp4&t=203s) and have a throwaway line at the end about how yes, the main reason a helicopter would have a second rotor is to eliminate the tail rotor, but it has the side effect of allowing the helicopter to have a higher top speed and you end up with a cargo helicopter (Chinook: 196mph) that can go faster than an attack helicopter (Apache: 182*). If you're actually designing for top speed, you can add the pusher prop and you get the Sikorsky X2 prototype that can do 290mph because, as you said, it lets you do weird poo poo with slowing down the main rotor but they're both important pieces of the puzzle. I see Sikorsky had a similar prototype in the 70s but with a pair of turbojets instead of a pusher prop that could do 303mph but suffered from "excessive fuel consumption". Many helicopters are designed so they're hanging off the rotor like a giant clothes hanger and if they ever do a negative-g maneuver it'll just lift itself off the closet rack and fall on the floor. Here's Aldi-brand Lindsey Graham to tell you more: https://www.youtube.com/watch?v=_QkOpH2e6tM
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Feb 1, 2022 23:26
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MrYenko posted:I’d love to hear thoughts from Ambilical Hexnut, but I’d bet a dollar that Defiant is combining a coaxial rotor system with multi-speed rotor systems that have started to gain traction. Okay the first thing everyone needs to understand is that in any army unit, hangaring all of the helicopters at once in the face of inclement weather requires packing them in so tightly that all the main rotor blades of different aircraft are intermixed above/below each other, with crew chiefs pulling out seat cushions to shove in between two stacked blades from adjacent aircraft. Doubling the amount of main rotor blades is going to make this a nightmare. Aside from that, I have no involvement in FVL and am only speculating: a single oversized engine (instead of two), a pusher prop, and a fully rigid rotor system is a hype formula we've seen before in the Cheyenne prototype. The straight and level speed of the defiant is insane compared to the conventional fleet. It is entirely reasonable to assume that they moderate the drivetrain RPM while increasing pitch on the pusher to let it soak up horsepower when operating above some design speed to avoid RBS or excessive flap, but there could be some other engineering solution too. I think in the Cheyenne the way they did it was just to reduce collective pitch as the wings took on lift, though with a regrettable outcome at the limits of rigid blade flap. Kesper North posted:Am I right in assuming the stacked rotor configuration will have 2x the maintenance hours and costs of a conventional design? Not necessarily. Hopefully the aircraft system is being designed with a modernized/RCM/etc maintenance regime as well, as even current aircraft are (mostly) doing phase maintenance. CarForumPoster posted:Are there "stealth" RCS/IR requirements for this thing? It seems like there are a decent number of features to reduce the from the ground IR and forward RCS. Wish I could see the CFD/thermal model for the exhaust heat. Dropping bombs from up high or being a swoopy operator necessitates a stealth design because operating up in the rare air means accepting that radar can spray indiscriminately. For conventional helicopters this is not necessarily a primary concern. Psion posted:from what I know helicopter survivability in a shooting situation involves not being seen so as not to get shot at, so anything to stack the deck in favor of not being detected = good Terrain flight. Cat Hatter posted:I'll admit that practically everything I know about helicopters I learned from Smarter Every Day and am welcome to being schooled on helicopter design. They have a short video about how helicopter speed is self-limiting (link to the spot: https://www.youtube.com/watch?v=_pbdwueqGp4&t=203s) and have a throwaway line at the end about how yes, the main reason a helicopter would have a second rotor is to eliminate the tail rotor, but it has the side effect of allowing the helicopter to have a higher top speed and you end up with a cargo helicopter (Chinook: 196mph) that can go faster than an attack helicopter (Apache: 182*). If you're actually designing for top speed, you can add the pusher prop and you get the Sikorsky X2 prototype that can do 290mph because, as you said, it lets you do weird poo poo with slowing down the main rotor but they're both important pieces of the puzzle. A Chinook goes faster than an Apache not from its tandem design but because if you take a 10,000hp aircraft that's designed to carry its weight in cargo with enough tip speed headroom but don't put any cargo inside it can instead spend that energy pushing itself forward. In practice, attack aircraft with lower cruise speeds have all flown faster than any cargo aircraft because attack aircraft perform steep dives right up against vne and lift aircraft don't. Top speed is sort of an irrelevant metric for comparing helicopters, but dramatic cruise speed improvements are very significant. But having tandem doesn't necessarily mean you can't have a little attack, as a treat:  shame on an IGA posted:Many helicopters are designed so they're hanging off the rotor like a giant clothes hanger and if they ever do a negative-g maneuver it'll just lift itself off the closet rack and fall on the floor. In conventional helicoptering the chocolate and vanilla of main rotor systems are 'semi-rigid underslung' where the entire aircraft hangs underneath a trunnion joint that allows two opposing blades to flap in opposition to each other, and 'fully-articulated' where individual blades are hinged to a hub at their root and they flap independently as they go around the disc. Fully rigid rotor systems are that center lever on the ice cream machine where you have blades rigidly fixed to a central hub which flap by flexing along their spans. Semi-rigid rotors exposed to low-g loading will find themselves a new job and leave the aircraft in flight, while most aerobatic helicopters have traditionally employed fully articulated systems. The defiant seems to use coaxial fully rigid main rotors. Ambihelical Hexnut fucked around with this message at 03:43 on Feb 2, 2022 |
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Feb 2, 2022 03:32
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Ambihelical Hexnut posted:
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Feb 2, 2022 04:28
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I get fully rigid when people start start talking about helicopter mechanics. Paging Tetra... Tetroupadus?
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Feb 2, 2022 05:22
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slidebite posted:Bit of a tail strike too. Could have done without the color commentary tho. Plane spotters like him at major airports are there for the same reason people go to NASCAR races. They're AvGeeks for sure, but they're all also actively or passively playing the world's most ghoulish lottery in the hopes they get the best footage to peddle to international news organizations for profit if a passenger jet eats it on takeoff or landing.
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Feb 2, 2022 06:09
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EvenWorseOpinions posted:If your school has a flight program too you can probably help with annuals and 100hrs, which is a great opportunity to be around some (hopefully) seasoned mechanics I'm an almost 50-year-old dude that is finally leaving the corporate world and going back to my roots turning wrenches. I applied to MIAT, but the community college suggestion is a good idea. I haven't signed anything yet.
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Feb 2, 2022 15:15
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PhotoKirk posted:I'm an almost 50-year-old dude that is finally leaving the corporate world and going back to my roots turning wrenches. I applied to MIAT, but the community college suggestion is a good idea. I haven't signed anything yet. I went to BCC’s Part 147 school, and it was pretty excellent. Cost all of $5000 IIRC. We were mostly teenagers and college kids, but we did have a guy in his late fifties with a GLORIOUS combover who wanted his A&P so he could buy a UH-1 and go dusting. He drove from northern Martin county to North Perry every day for two years; I still can’t believe it. He was changing the oil on his Dodge Caravan literally every week. He also brought in a super-scabby 50’ radio mast part-by-part to use the blast cabinet over the course of like three months. He was a weird dude. I hope he got his Huey and went screaming off into the central Florida sunrise, spraying noxious chemicals on oranges or whatever he wanted.
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Feb 2, 2022 15:45
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slidebite posted:I can't imagine that came off easily. Most commercial airplane doors are designed to come off relatively easy, just in case something like this happens. All you gotta do now is fix the broken shear pins and put the door back on. If they're REALLY well-attached, then something like this bends the fuselage.
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Feb 2, 2022 16:59
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Oh they're on shear pins? I didn't know. Makes sense too.
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Feb 2, 2022 17:03
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All I'm going to say about CAP is that, as a former member, I don't recommend touching it with a ten foot pole. There's a lot of stuff going on under the surface that is impossible to see unless you take an active interest from the inside - sometimes including violence, sexual crime, and active cover-ups of the aforementioned. Hypothetically, of course. Not that I ever witnessed such. I just wouldn't be surprised if something like that ever came to light.
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Feb 2, 2022 19:58
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The USAF Museum has decided to start showing plane porn: https://www.youtube.com/user/USAFmuseum/videos
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Feb 4, 2022 08:55
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Feb 4, 2022 13:36
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https://www.youtube.com/watch?v=WMwcIXVdois
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Feb 4, 2022 13:40
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To clarify two things about the Defiant X. A) what makes it different than a conventional coaxial rotor is that the rotor is rigid. There are two main benefits to this. The first is that blade flapping is severely reduced, so that the rotor system can be relatively closely spaced to reduce hub drag without a high risk of the blades contacting each other (the flap response to a gust is opposite on both rotors, so the tips tend to move toward each other on one side). The second main benefit is that the rotors can carry a hub moment, that is to say, that the aerodynamic loads do not need to be balanced across the advancing and retreating sides. This allows the retreating blades to be unloaded somewhat to delay stall at high speed. The total amount is not that much, I’m not sure where they ended up (if they’ve even decided, since it’s up to the FBW system), but people have spent a lot of time looking at the 10-30% “lift offset” range to give a sense. The downside to carrying those moments will be stronger hub loads and potentially vibration issues. But these are both much better understood today than they were when the first rigid rotors were flown. B) There is some rotor speed reduction as flight speed increases. This is done entirely by reducing the turboshaft RPM. They claim about a 15% reduction using the T55s in the current prototype, which have been modified a bit as they weren’t designed to operate like that. The plan is to develop new engines for the aircraft, so I’m not sure if they plan to get a bigger reduction in the production aircraft. The focus may just be at operating efficiently at that reduced speed. Anyway, the advert is cool. They’re clearly trying to sell up the “low speed maneuverability” and small footprint of the Defiant versus Bell’s V-280. The question is really whether the Army wants something that still operates like a helicopter, or if they’re willing to give some of that up to get more speed and range.
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Feb 4, 2022 15:58
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PhotoKirk posted:I'm an almost 50-year-old dude that is finally leaving the corporate world and going back to my roots turning wrenches. I applied to MIAT, but the community college suggestion is a good idea. I haven't signed anything yet. I went to A&P school at a community college as a mid 20s guy, had a couple ~50 year olds as colleagues at the time. I stopped back in to do some recruiting for my employer last year and there were maybe 2 to 3 older guys between the 1st and 2nd year courses. My intuition is that that probably isn't atypical for part 147 schools. My experience is if you show up, pay attention, do the work, and don't do stupid things, it's really easy and you end up learning a lot; the people who had trouble in the program were the kids fresh out of high school who wanted the rewards but weren't able to demonstrate the baseline responsibilities of showing up to class, turning in homework, or not repeatedly getting in trouble for smoking pot inside of their dorm room, for instance. In other news, I'm told (I tried to validate this but I don't know Russian) that the new TU-160M has a rear facing radar that it can use to fire air to air missiles, as well as the forward facing radar that it already had. The missiles will not be rear facing, instead the missiles will launch as normal, then do a 180 turn to track targets. EvenWorseOpinions fucked around with this message at 21:21 on Feb 4, 2022 |
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Feb 4, 2022 19:14
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Oh poo poo, I had no idea that was hanging out over at Redstone. I'll have to try and go see it the next time I'm back home. Warbird fucked around with this message at 19:37 on Feb 4, 2022 |
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Feb 4, 2022 19:34
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https://i.imgur.com/PrIhWrf.mp4 from: https://www.reddit.com/r/vtolvr/comments/sbxcly/yall_asked_for_recoil_here_it_is/
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Feb 5, 2022 10:17
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Just casually using solid rocket boosters for ballast.
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Feb 5, 2022 14:51
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BIG HEADLINE posted:Plane spotters like him at major airports are there for the same reason people go to NASCAR races. They're AvGeeks for sure, but they're all also actively or passively playing the world's most ghoulish lottery in the hopes they get the best footage to peddle to international news organizations for profit if a passenger jet eats it on takeoff or landing. That sounds like worse odds than an actual lottery, given safety numbers. And that bad weather is involved in most incidents nowadays, which is also bad spotting weather.
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