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A Little Gear That Could Reshape the Jet Engine
- JSeymourATL 11y ago“The Silicon Valley guys seem to have the attention span of 3-year-olds.”
- GauntletWizard 11y agoIt's a bit easier to be blasé about testing when your worst-case-scenario is that somebody misses a ride, vs when you kill ~150 people. The rapid cycle of innovation is a tradeoff that SV is able to make (and finds amazingly beneficial) because we're working with soft tools and have backups of our data. I'm certain that were human life so cheap, Pratt and Whitney would have a much shorter dev cycle, too.
- kelvin0 11y agoCuriously, I read that comment as saying: Silicon Valley is too preoccupied with short term profits to be able to concentrate for a long time and come up with such 'tangible' and actual benefits in the domain of transportation. This is not the next 'snapchat/tumblr/facebook' ... That's how I interpreted his comment at least.
- onion2k 11y agoShorter project sprints came about to try to fix the problem of project failure. Failure to create a loop that feeds discoveries in to a project's knowledge, and to communicate knowledge between teams is exactly what makes projects come to catastrophic ends, and that's what the shorter cycle time attempts to correct. The fact the product benefits from faster innovation is a function of more efficiently sharing knowledge and data, not spending less time on individual components. Designing and testing an engine can be done in an agile style. There's nothing intrinsically "software only" about the methodology. NB: I ran a startup that made software to manage requirements in big projects. I've spent lots of time thinking about different ways to manage things. Including how not to, but that was after we failed.
- ams6110 11y agoYes it is intrinsically software-only. When a software test fails you fix the bug and run it again. When a jet engine test fails you just blew up a $10M prototype.
- onion2k 11y agoA software test is equivalent to a testing small part in an engine design. The cost of failure is low. The cost of a full production test in an engine design is clear, but it's the equivalent of a product handover and acceptance testing in software. The cost of failing that test could well run to millions of dollars. The only difference for a SaaS startup is that they're their own customer for product development (in the sense that they build and test in-house rather than someone else paying them to build a product). The cost of failure is still there, it's not measured.
- HeyLaughingBoy 11y agoIt's also a very different mindset. I moved from a long career designing software for Medical Devices to desktop S/W and the hardest part for me is getting used to a much more relaxed approach to development process, documentation and testing. It's weird when I realize I can just push something out the door and not have to wait for the reams of paperwork to be complete.
- pbowyer 11y ago> I'm certain that were human life so cheap, Pratt and Whitney would have a much shorter dev cycle, too. I read a book recently about the history of Supermarine, and what jumped out was the attrition rate of their test pilots. Ditto for the post-war British jet industry. There is a trade-off point between safety and fast development, but I'm glad we've moved to the side of safety.
- bediger4000 11y agoOr it could be that the FAA and other airline regulatory bodies around the world (especially in UK and Europe) keep innovations from happening, and so development times can be long.
- astrodust 11y agoIf we could distribute a new gear design which fixes flaws in some over-the-air patch it'd be a lot easier to iterate and improve. Selling thousands of engines too soon and realizing they all suffered from a critical engineering issue could bankrupt your company. There's a lot on the line!
- kenko 11y agoBankrupt your company, and probably do some serious damage to the airlines or plane manufacturers that bought them from you, and also kill a lot of people. But, you know, move fast!
- Scuds 11y agoYou can have an idea, but getting it into production, especially if the entire design hinges around it, is an entirely different story. From the article, the new engine is to wide to fit a number of existing planes.
- hinkley 11y agoYeah I don't think this is an argument the aerospace industry can win. To whatever degree SV lacks patience, the airplane industry has the opposite problem. Tolerance of needless complexity leads to expensive systems that aren't necessarily any better for it. There's a real sense that design has absolutely no place and every problem can be engineered around, even if it takes two more layers of parts to achieve it. Not only that, they have a bad habit of adopting disproven solutions simply because they 'are mature'. That is I believe Musk's premise with his rocketry division. It couldn't possibly be this complicated, can it? I hope he turns out to be right. But if he is, gonna be a lot of smug engineers having to take early retirement.
- hyperbovine 11y ago> That is I believe Musk's premise with his rocketry division. One hull loss per nineteen attempts is not an acceptable failure rate for "the airplane industry", is it? It's difficult for me to put into words the level of respect and admiration I have for the risk-averse, plodding, and methodical aerospace culture that has created modern aviation. (Seriously, have you ever considered the absolute miracle of engineering that is a modern jetliner?) To lump that profession under the same rubric of engineering as the one where a bunch of overcaffeinated "disruptors" write software to get people to click on ads seems... unjust, to put it mildly.
- hinkley 11y agoYou can't compare a giant pipe bomb with passengers on one end to an airplane either, but I'm the one who opened that door without a suitable qualifier, so that's on me. What I meant to convey is that I expect someone to do to commercial aviation what Musk is trying to do to rocketry, and what I expect that to look like is for more effort to be placed into reducing single points of failure by designing complementary systems instead of just putting three of everything on the vehicle and then adding two more layers of stuff to manage it. And also for them to act like progress in software development processes actually applies to them now instead of in thirty years. We got no end of grief for refusing to do pure waterfall, and they were conspicuously silent when we're were able to fix fundamental up front design flaws in 3-8 weeks, and without doing a reenactment of Macbeth starring William Shatner, set in a rehab clinic. Then again, I expect something to happen to improve the caliber of software developers out there as well, so we'll see how that goes. Often when I expound on the qualities of my profession I am intentionally and consciously imagining that the 30% of my peers that are responsible for 70% of our problems either don't exist, or are off doing something that's not important.
- knodi123 11y ago> what may be most remarkable about the engines is that they took almost 30 years to develop. That’s about 15 times as long as the gestation period of an elephant Who the hell is running their analogy department?!? "Thirty years! That's a big number! We need some kind of comparison that will instantly give the reader perspective. Of course, in this, as in so many other things, the answer lies in pachydermian pregnancy patterns."
- avar 11y agoI thought the next example was even more inane. It goes on to say: "and unimaginably longer than it takes to pop out a smartphone app".
- wmeredith 11y agoWell, as we all know, every smartphone app takes exactly 1 year to create, and it's hard to imagine a time period 30 times longer.
- craftkiller 11y agoSmart phones haven't even existed long enough for anyone to spend 30 years making an app for them... And the laws of physics have much better backwards compatibility than each new fly-by-night smartphone OS
- gavazzy 11y agoThirty years is: ~ 0.36 x orbital period of Uranus ~ 1.02 x orbital period of Saturn ~ 5.7 x half-life of colbalt-60 source: http://www.wolframalpha.com/input/?i=30+years http://www.wolframalpha.com/input/?i=30+years
- hinkley 11y agoPsssht, it's not even half a Jovian year. What's the big deal.
- jws 11y agoAs long as we are ripping on their numbers… "75% less noise" almost certainly means 75% less power in the noise which means about 6 decibels quieter. That's noticeable, but not huge.
- callesgg 11y ago30 years. I do wonder if that is true. Did they actually developed it under a time period of 30 years. or do they mean it more in a way that it is a continuation of previous models.
- kenko 11y agoDid you read the article. I do wonder if that is true.
- mschip 11y agoIt's more of a 'The concept is 30 years old' thing. Some of the reasons driving the commercial development only became factors in the market more recently; things like fuel efficiency and airport noise restrictions. Also, one of the less discussed advantages (as a customer) for the geared turbo fan is the decrease in expected maintenance/repair costs on the life of the engine. That's big business for engine manufacturers and there will be less of it with this design.
- dognotdog 11y agoIt'd be interesting to know what exactly they are doing in the gearbox, apart from the flexible mount to absorb excess torque. New materials? Surface treatments? Special lubrication?
- rm445 11y agoThis article has much more detail: http://theflyingengineer.com/flightdeck/pw1100g-gtf/ http://theflyingengineer.com/flightdeck/pw1100g-gtf/ The gearbox is described as the epicyclic type with the compressor driving the sun gear and the carrier of the five planet gears driving the fan. The article doesn't seem to identify any extra special sauce. It points out that geared turbofans have been used on an airliner in the past, and identifies some design trade-offs. "there may be a performance penalty, marked by slower cruise speeds for the same thrust setting, possibly slower max cruise speeds, slower green dot (best L/D speed), slightly shallower climbs, and possibly degraded single-engine performance. The single engine performance difference is expected to be the most prominent, with a possibly larger yaw, and a definitely reduced climb gradient, consequently lowering obstacle clearances." My impression based on just reading that article is that, rather than a technological breakthrough enabling the geared approach, Pratt and Whitney have explored a rather neglected area of the design space, to arrive at a more efficient, lower noise engine with slightly worse performance in some other respects. And had to conquer numerous 'ordinary' engineering challenges to make it work.
- dognotdog 11y agoThanks, that article was indeed much better to understand what's going on. Still, as mentioned, high-speed gearing of the kind does offer some design challenges, but apparently its all secret sauce.
- mhandley 11y agoI wonder if instead of gearing a single large fan, you could just remove the fan from the turbine altogether, add a much larger alternator, and power several large electric external fans from each turbine? That would give you more fan area than you can get with a geared turbofan, optimal fan speed for efficiency, redundancy in case one of the fans suffered damage, allow cross-routing of power between turbines if one turbine failed, and not require quite such large fans so they'd fit under the wings more easily.
- blobert 11y agoThis idea would unfortunately negate one of the top benefits of a high-bypass turbofan. Noise reduction.
- mschip 11y agoAnd noise reduction is actually a really important benefit of this engine as some airports have restrictions on noise.
- mhandley 11y agoYes, but why is a high bypass turbofan quieter? If I understood correctly, it's because most of the thrust comes from the large slow moving fan, so you don't need to blast nearly so much air through the turbine as a turbojet to get the same thrust. The whole purpose of decoupling the fans is to give you an even higher bypass ratio - two or three large electric fans driven from one turbine can have a larger swept area than a single large geared turbofan, so can run slower for the same thrust, and hence be quieter.
- WalterBright 11y ago> Yes, but why is a high bypass turbofan quieter? The noise comes from high speed air alongside slow moving air. A high bypass fan moves more air at slower speed to get the same push. The slower speed means less noise.
- Gibbon1 11y ago
- Animats 11y agoThere's a long negative history of high-speed gearing. Jet engines have one big rotating unit, and that basic simplicity is good for reliability. Turboprops have a gearbox, and fragile, high-maintenance gearboxes are a long-standing problem with turboprops. Adding a gearbox without reducing reliability is a major achievement.
- iammaxus 11y agoHigh-speed gearing is indeed very difficult, but jet engines already typically have two separate, concentric rotating units (spools: https://en.wikipedia.org/wiki/Turbofan#Basic_two_spool https://en.wikipedia.org/wiki/Turbofan#Basic_two_spool). Also, as the article mentions, turboprops (essentially jet engines connected to a propeller) already commonly use gearing. I guess you can think of it as a turboprop with a duct. The reality is probably just that this is a solvable problem that just wasn't worth the work while there were easier efficiency gains to be had.
- fancyketchup 11y ago> High-speed gearing is indeed very difficult, but jet engines already typically have two separate, concentric rotating units [...] Yes, everyone knows that, but the spools are not connected by a set of gears as they are in the P&W's new engine. > Also, as the article mentions, turboprops (essentially jet engines connected to a propeller) already commonly use gearing. I guess you can think of it as a turboprop with a duct. The new engine is ALSO unlike most installations of turboprop engines in that the fan is driven by the power spool, not a free turbine. The free turbine (in turboprops that have them), which powers the reduction gears for the propeller, runs at a much lower speed than the power turbine.
- readams 11y agoSo basically this seems to be a extra-high-bypass turbofan achieved by gearing down the fan. But delayed hugely because giant megacorps move very very slowly.
- ckozlowski 11y agoBecause of safety. For a brand new concept engine, you don't want to have any doubts at all. That means lots of long term testing. Since it will be powering jetliners, it has to be as close to flawless as possible. And even then, they have to convince the airline companies to use it.
- wernercd 11y agoTake too long? ZOMG KKKORPORATION$!!! Move to short and fatal flaw kills people? ZOMG KKKORPORTATION$!!! Can't win for losing...
- pjc50 11y ago"Move fast" certainly applies to jet engines, but "break things" results in lots of expensive high-velocity shrapnel.
- brwnll 11y agoCould some knowledgable aircraft people answer these questions for me? 1. Can/are jet engines ever swapped out after a plane as been put into service? Or will these only ever be sold attached to new aircraft orders. 2. Any idea on what the engine costs? And what percentage of the overall airline cost is engine? I didn't see any references to costs of this engine vs existing models.
- vermontdevil 11y agoAlso I believe airlines often lease backup engines while they service the original purchased ones. It's been a while since I was in the business but that's what my old company did. They leased spare engines and aircraft on demand if needed.
- WalterBright 11y agoRe-engining an airframe is a big deal. A lot of engineering has to go into it.
- dexterdog 11y agoWhy can't they just have a standard mount like an LCD panel?
- ChuckMcM 11y agoIt isn't the mount that is at issue, it is stresses on the airframe. Different engines stress the airframe in different ways leading to different failures.
- WalterBright 11y agoConsider that the engines for the Me-262 turned out to be heavier than anticipated, throwing the center of gravity off. The easiest fix was to sweep the wings back, inadvertently discovering the advantages of swept wings for high speed flight.
- Gibbon1 11y agoI upvoted cause not dumb question. Yes they do to an extent. One of the major reasons the engines are mounted on pylons is exactly to make maintenance and replacement easy.
- PeterWhittaker 11y agoLove this: “It’s the antithesis of a Silicon Valley innovation,” says Alan Epstein, a retired MIT professor who is the company’s vice president for technology and the environment. “The Silicon Valley guys seem to have the attention span of 3-year-olds.”
- TeMPOraL 11y agoI suppose the world is big enough for both. Sadly, media follows the kids more often than the adults.
- gilgoomesh 11y agoYeah, there are definitely people in Silicon Valley who are working on the same problems they were working on 20 years ago – it's just not very interesting to outsiders so you don't hear about it (until they have a breakthrough).
- nether 11y agoWell, that's what you get with age discrimination. There are probably all manner of worthwhile problems that older people understand better due to experience in long-haul, delayed gratification efforts (raising kids to adulthood, financing a house, chronic illnesses) rather than scrambling for the latest gastropub or gallery opening.
- jimbrusstar 11y agoIt's easy to dismiss Silicon Valley companies as trivial, but if nothing else, SV stands for a culture of experimentation. This, by contrast, sounds like an engineer's nightmare: > “In other years we hid him [McCune] behind the curtain and slipped him some sandwiches so management wouldn’t know what the investment was,” he jokes. Maybe a decades-long attention span wouldn't have been required in the first place if the company in question gave their engineers better support.
- joncp 11y ago> "At times, the extent of the operation had to be protected from bean-counting Pratt executives" Yep, that's how UTC operates. It's amazing they make any money at all.