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Disciple of Pain posted:You can google RTO procedures where they get the plane at max weight to takeoff speed and then use ONLY the brakes to stop. That is "difficult" to stop (the brakes will catch fire, tires explode, etc - but the plane has to be able to sit/taxi for 5 minutes without having a major fire) Actually, the brakes shouldn't catch fire, and aircraft tires really don't blow up. When that test is done, the brakes will be glowing white hot, and there may be some grease briefly burning off, but the brakes and wheels aren't actually on fire. Large aircraft tires are normally fitted with fusible plugs that melt at a certain temperature to deflate the tires in a controlled manner, since the tires are inflated to around 200PSI, which makes a blowout insanely dangerous. Here's the video of a 777 doing a rejected takeoff during certification in the 1990's http://www.youtube.com/watch?v=wXpjBxD0Rhg
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Nov 11, 2009 03:55
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Plinkey posted:The other thing to consider is that they've got a bunch of planes mothballed for spares because they are so old. The 33 B-1's that got mothballed (representing 1/3 of the entire production run) were actually retired as a cost cutting measure, since programs like the F-22 and F-35 were running massively over budget and grounding some of the B-1 fleet freed up enough money to keep operating the remaining aircraft. Currently, the B-1 is slated for retirement somewhere around 2038 (although the Pentagon is discussing retiring the whole B-1 fleet sooner to save money), which means the B-1 will likely cease flying earlier than the B-52 (scheduled to be serving until at least 2040) it was supposed to replace.
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Sep 1, 2010 05:53
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The Scientist posted:How common is that sort of thing? It sounds like you lucked the gently caress out. Is it common for cars to get repaired free of cost for problems inherent in the design even when not under warranty? Anecdote ahoy! I got the center differential on my Forester replaced under warranty, despite the vehicle being well outside the normal warranty time and mileage. I had taken the Forester into the dealer a few times (when it was still under warranty) for the center diff binding up when it got hot, but the dealer gave me a "couldn't reproduce the problem" excuse, and refused to remove the differential and see if it was showing signs of wear. Some time after the warranty expired, the problem started occuring pretty much constantly, and Subaru of America agreed to cover the work under the warranty if it turned out to be a problem with the differential. After a dealer determined that the problem was indeed the center differential binding up, Subaru covered the entire cost of the replacement without any attempts to backtrack or otherwise aviod paying for the work.
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Jul 12, 2011 04:54
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CommieGIR posted:I picked up a red top gel cell 1000 CCA battery for my Jetta about a year ago, I love the damned thing. I've had one in my Forester since 2005, and it's still working perfectly despite having spent five years in 110F summers and -40F winters. So far, the battery has outlasted a center differential, one set of accessory belts, two sets of tires, three windshields, and a set of front brake pads, so I'd say the extra $40 that battery cost was probably worth it.
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Mar 18, 2013 03:52
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Slavvy posted:How is 'mileage' measured on aircraft tyres? As in, is that tyre failure something that could've been prevented by inspecting/testing thge tyre or is it just one of those things? Aircraft tires are generally replaced on an "as needed" basis, usually once the tread has worn past a certain point or if there are visible signs of flat spotting or abnormal wear on the tire. Generally, tires are pretty reliable (most blown tires are due to something puncturing the tire, or pilot error or an anti-skid failure locking the brakes on landing) as long as they're properly inflated, but underinflated aircraft tires have a nasty habit of blowing out at high speed on takeoff and causing all kinds of mayhem and accidents.
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Jul 31, 2013 21:32
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Budget Monty posted:So I heard a loud crash outside our shop today. I go outside to see what it was, and look across the alley that divides our shop from the Hyundai dealership shop... The car clearly wants someone to give it a belly rub, so I fail to see the problem here.
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Oct 2, 2015 08:10
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cakesmith handyman posted:I'm not a plane-haver, what's the critical engine? (Yes I could Google it but goon answers are either better or funnier) It's the engine that most adversely affects the handling or performance of the aircraft if it fails. For various aerodynamic reasons, propeller driven twins that have both engines rotating clockwise will be slightly harder to control if the left engine fails (due to the nose wanting to yaw towards the dead engine), which makes the left engine critical. If the engines rotate opposite directions (normally clockwise on the left side, counterclockwise on the right), neither engine is critical. The University of North Dakota has a pretty nice interactive Flash tutorial on single engine aerodynamics, if you want a more detailed explanation. http://media.avit.und.edu/f4_Inop%20Engine%20Trainer/f1_Inop%20Engine/060302/mainmenu.php
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Feb 18, 2017 21:46
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Breakfast Feud posted:Yeah sure this thing was cool in the peacemaker, but check out the stratocruiser and it's Hawaiian lounge! The Stratocruiser was also prone to horrible mechanical failures. Of the 55 Stratocruisers built, 13 were lost in accidents for various reasons, including several cases where a propeller blade would become unbalanced, which often resulted in the blade (and occasionally the entire propeller and engine) being torn from the aircraft.
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Jan 22, 2018 23:03
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Another fun "plane parts are expensive" story: The Q400's I fly are fitted with a HUD for use by the captain, which is projected onto a fold-down piece of glass that's roughly the size and thickness of a paperback novel. If that piece of glass is damaged, it's something like $20,000 to replace, despite the fact that it contains zero moving parts or electronic components.
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Jan 23, 2018 06:04
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BlackMK4 posted:Synergistic blockchain and aerospace technology, built to leverage millenial based organic growth through trickledown economics Will there be an app? Will said app "disrupt" air travel?
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Jan 23, 2018 23:56
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Cojawfee posted:It's surprising more people didn't die in the shuttle era. It was a big colossal gently caress up. The quest for a reusable spacecraft that ended up being massively more expensive than they ever imagined and barely reusable. The shuttle kind of fell into a weird gap where some parts of it (relatively lightweight, reusable, throttleable engines, the fly-by-wire system and computers) were pushing the limits of technology when it was designed, but other parts (using solid fuel boosters and discarding the external tank) weren't really that advanced (or were a step back), so the end result was a huge compromise between the original "giant reusable booster launches reusable orbiter" concept and what could be done cheaply and reliably to keep the costs from getting even more out of control. When the Shuttle program was originally started, the idea was that there could be around 20 launches a year, and each orbiter would be in service for about 10-15 years before it was replaced with something newer. Once the development costs started going through the roof and it became clear that the launch rate would be substantially lower (and funding for a Shuttle replacement never really happened), NASA was forced to extend the life of the orbiters to somewhere around double what was originally intended, so managed a pretty decent record when all of that is taken into account. azflyboy fucked around with this message at 06:33 on Jul 13, 2018 |
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Jul 13, 2018 06:20
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Unfortunately I have no pictures, but we had someone make a very impressive (and expensive) noise at work by backing a running turboprop into a ladder. Apparently the ladder was under the wing for maintenance, and a ground crew was going to reposition the airplane by taxiing it, and failed to see the ladder before they pushed the airplane back with an engine started. At idle, the propeller isn't spinning terribly fast (maybe 400RPM), but it's 13.5' in diameter, so the blades still have a lot of energy behind them. When the prop hit the ladder, it drat near launched bits of the ladder into orbit (since the blades move upwards on that side), accompanied by large chunks of a propeller blade that had shattered when it whacked into the ladder. The propeller was a total loss, but since the propeller gearbox isn't directly attached to the power section of the engine, they just had to swap the gearbox instead of pulling a $1.3 million engine for overhaul.
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Apr 29, 2020 03:31
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Beach Bum posted:By "power section" do you mean the gas generator section? My layman's understanding is that the power turbine is what powers the propeller gearbox. I'm not criticizing your terminology, merely trying to wrap my head around it. You actually work on the drat things so please forgive any ignorance or lack of understanding on my part, I merely watch a lot of AgentJayZ Yeah, I meant to write "gas generator, but had a complete brain fart and typed something else. My bad.
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Apr 29, 2020 16:18
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Tomarse posted:So if the power turbine is stopped suddenly does the resulting reduction in fluid(air) movement not still get transferred back to the compressor parts and cause them to suddenly slow due to the reduced flow? It does, but since air compresses and the engine isn't a sealed container, the compressor blades slow down (relatively) gradually, so that alone won't cause damage. However, disrupting the airflow through the compressor is a good way to set off a compressor stall or surge, and depending on how hard the engine is working at the time, the resulting spike in temperature (since airflow isn't going the right way), compressor speed (which accelerates because the stall suddenly removes a lot of load from the turbine), and vibration (due to disrupted airflow inside the engine) can easily cause serious damage if the FADEC system doesn't cut back on the fuel flow quick enough.
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Apr 29, 2020 20:22
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Godholio posted:Well poo poo, I always assumed it was a physical connection. Sometimes it is. The Pratt and Whitney PT6 and PW100 families (which make up a majority of the civil turboprop market) are all free turbine designs, but there are also "single shaft" or "direct drive" engines where the prop gearbox is connected directly to the hot section of the engine. Free turbines have the advantage of requiring far less energy to start (since the starter just has to get the gas generator spooled up), generally being quieter (the propeller can rotate slower because the gas generator and power sections don't have to rotate at the same speed), and they're generally harder to break if the pilot is kind of hamfisted. Single shaft engines have the advantage of using fewer moving parts and responding faster to rapid power changes (although FADEC has reduced this difference), and they can also be more fuel efficient since there isn't the losses associated with having an extra turbine in the engine.
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Apr 29, 2020 22:10
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SlowBloke posted:Isn't the fuel tank pipe width bigger on diesel than gasoline in the US? Here in the EU it is and that is enough to discourage local idiots The same thing is present on airplanes, and people still screw it up. Jet-A nozzles are wider than 100LL nozzles, and are actually rectangular, so it should be impossible to fit them into the smaller, round filler ports on non-turbine airplanes. Despite that fact and airplanes having very obvious placards next to the filler openings saying what fuel to use, a couple of pilots every year manage to carefully fuel their piston airplane with Jet-A, which usually ends badly. Recently, there have been issues where a fueller will accidentally put DEF into a container on a jet fuel truck that's intended for an anti-icing additive, which then results in the DEF crystalizing in the fuel at altitude and blocking fuel filters.
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May 14, 2021 03:54
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There's also the fact that something like 30% of the piston engine GA fleet uses about 80% of the total avgas, and since those airplanes run turbocharged engines that absolutely require the higher octane rating, it's historically been easier to just grandfather 100LL in whenever environmental/emissions standards change than to put all the time and money into finding a universal replacement for lead. On the subject of mechanical failures and airplanes, I'd like to mention the Porsche PFM 3200. The PFM 3200 was Porsche attempting to re-enter the aviation engine market in the 1980's with an engine derived from the one used in the 911, and despite the company throwing a reported $75 million into the program, they only ever built about 80 engines, 41 of which were used on Mooney M20L's built in 1988. Porsche surrendered the type certificate for the engines in 2007 and stopped providing any support at the time, and while the FAA has said airplanes using the engines are still airworthy if maintained as required, the complete lack of factory support or any kind of stock of parts makes that part tricky. azflyboy fucked around with this message at 03:25 on Jan 6, 2022 |
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Jan 6, 2022 03:22
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kastein posted:Yeah, but the TBOs on aircraft engines are in the 4 figure hour range, not "you overhaul it when it ends up on a tow truck", so there are ample opportunities in between the 70s and now for each aircraft to have had upgraded parts put in that wouldn't need 100LL. Depending on how well the airplane is maintained, a 2000hr TBO can easily cover an airplane for 20 years or more, and since private owners aren't required to follow TBO schedules, it can take decades for something to trickle down to most of the GA fleet if the FAA doesn't force an "immediate" change. With ethanol, the issue is with seals and lines in the fuel system (which typically aren't replaced until they fail or show signs of wear), as well as the fact that a lot of airplanes spend a lot of time sitting, so ethanol degrading some kinds of rubber and turning into varnish means that airplanes were always going to need some other kind of additive. Plus, avgas sales are miniscule in comparison to gasoline or diesel (about 200 million gallons of avgas are sold per year, versus 120some billion gallons of auto gas), so the economic incentive to come up with something different than lead wasn't really there either.
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Jan 6, 2022 04:04
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kastein posted:Well goddamn that was a hell of a story. He should try it again with all alloy block LS motors. The Unlimited class is basically dead at this point in terms of competition or development, since the core airplanes are too expensive for an event that happens one weekend a year, and the really fast airplanes are all retired to museums or grounded for various financial reasons. As someone put it; "You buy a P-51 for $2 million, spend another $1 million modifying it, and now it's maybe worth $1 million because no one wants a modified Mustang". For the last few years, the Unlimited Gold race was basically Voodoo or Strega showing up, running something like 100mph faster than everyone else on the first lap, and then backing way down on the speed for the remaining seven laps to keep their engine from exploding. The Bronze and Sliver classes are basically just rich people flying warbirds in circles without really pushing the airplanes, so there's basically zero competition involved. Where the interesting racing and building is happening is the Sport class, since the rules are simply that the airplane has to be an FAA certified, kit, plans, or amateur built airplane, using a piston engine (or engines) with no more than 1000 cu. in. total displacement, capable of at least 200mph. Since those rules are deliberately vague, the class has a ton of people entering everything from an RV-7 that'll do maybe 250mph to a heavily modified Lancair or a Glasair that run massively boosted engines (and occasionally nitrous oxide) and can crack the 400mph mark. The number of entrants means the racing is usually a hell of a lot better than the Unlimited airplanes, and since the airplanes are significantly more affordable, it's also a class that has a future, whereas the Unlimiteds are basically a dying breed.
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Jan 26, 2022 05:04
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