7 ms·
When the plane takes off, why doesn’t the tail hit the runway?
- throwawayjava 9y agoThe tailskid (physical tailstrike protection [1]) was removed from the 777-300ER in favor of software-based mitigation [2,3]. [1] http://www.boeing.com/news/frontiers/archive/2004/december/i_tt.html http://www.boeing.com/news/frontiers/archive/2004/december/i... [2] http://www.airliners.net/forum/viewtopic.php?t=775483 http://www.airliners.net/forum/viewtopic.php?t=775483 [3] http://aviationweek.com/advanced-machines-aerospace-manufacturing/boeing-rolls-out-777-upgrade-plan http://aviationweek.com/advanced-machines-aerospace-manufact...
- neurotech1 9y agoIf there is a suspected tailstrike in an airliner, the tailskid might reduce the damage but it still requires an emergency return and engineering inspection for damage. Most severe tailstrikes occur on landing, and the tailskid isn't going to help reduce damage.
- deleted 9y ago[deleted]
- kuhn 9y agoInteresting write up. I was just watching a video yesterday which had a pretty good example of the testing aircraft manufacturers do for this scenario. It’s called a velocity minimum unstick test. Some impressive flying. https://youtu.be/BWwUTJM3jbA https://youtu.be/BWwUTJM3jbA
- chii 9y agoI'd say impressive commitment to QA'ing your product! I wish software in general, is tested to this degree.
- hueving 9y agoTesting costs money. If software in general was tested to this degree, we would still be stuck in the CLI-only world of 30 years ago.
- yebyen 9y agoOr, we would have long ago found better ways to adopt design and development strategies that more generally lend themselves to rigorous and easily repeatable testing.
- krupan 9y agoWe would have found Fred Brooks' missing silver bullet?
- yebyen 9y ago:D I don't know what that means, but I'm going to upvote you and go find out what interesting reading material I have missed! Edit: As a rails dev, I know that there is no silver bullet, but I also know that some strategies are objectively better than others, and some strategies produce software that is easier to verify than others. You can write heaping mounds of Javascript that you pile on top of each other, and pile more and more tests on top of each other and run them within a CI framework between each change (or don't), to build confidence that you don't break things that you previously guaranteed from one commit/release to the next... Or you can write tiny functions with an obvious and wholly singular purpose, and build them into micro-services that deliver one small fraction of the whole service, and test at each layer, and build composable units of the final service that you intended to guarantee. One strategy is easily verifiable if you keep it up without ceasing (and the other is not, but the two strategies are usually easy to tell apart.) Unfortunately it's probably true, for example, that neither strategy can ever be said to (obviate essential complexity! Fred Brooks) – to totally guarantee that the tail does not hit the ground on either takeoff or landing, which is a complex problem that probably can't actually be solved in units.
- 9y ago
- zodPod 9y ago"They put the plane into a stall to make sure it can recover" CAN YOU IMAGINE? lol Could you imagine being the guy who wakes up in the morning and is like "Today I get to put a plane into stall to make sure it can recover" shivers
- nunez 9y agoRecovering from a stall is something you learn very very early into flying
- sjburt 9y agoThis is a normal part of pilot training. I think it's less common in large aircraft but for small planes it's not uncommon.
- nsxwolf 9y agoIt really doesn’t feel like anything special is happening either, and recovery is quick and easy. It’s a non-event at altitude. Spin training though, no thanks!
- ubernostrum 9y agoWell, the nice thing about most planes is that they don't want to stall, and most of the time the correct action to recover is "stop doing things and let the plane recover". It's when you keep messing with it that you make things worse and get toward unrecoverability.
- mulmen 9y agoNormal pilot training does not involve testing aircraft limits. Stall training happens in a plane with a known stall speed and behavior. The quote is about finding that limit for the first time.
- Doxin 9y agoI'm fairly sure that the engineers have figured out a pretty good estimate of the stall speed before they send a pilot to go test it
- forgotmysn 9y agoi feel like it doesn't take a whole page to explain that planes are moving forward faster than they are gaining lift when taking off.
- larkeith 9y agoOr that the tail doesn't hit the runway because it's angled upwards.
- KGIII 9y agoI guess you can make it hit the runway, if you want. I watched a doc with them testing planes and they, quite literally, put some lumber on the tail to protect it from damaging the metal when they hit the runway with the tail. As in, they were intentionally trying to hit the runway with the tail.
- mikeash 9y agoYes, the actual answer to the question is "because the pilots are trained not to hit the tail, since it's expensive and makes the passengers nervous." It's a decent little article but it seems to not quite be on the same topic as the headline suggests.
- nopzor 9y agoYes, pilots are trained, and the design helps too. You first rotate the airframe at Vr speed (velocity rotate). Pilots are trained on their aircraft how much to rotate, and the design of the rear fuselage allows for initial rotation. Once you have rotated (ie. nose up) you wait for positive rate of climb, and you depart the earth, and possibly even increase your rate of climb. All without hitting the runway.
- KGIII 9y agoYeah, someone has added a video of this and it's currently at the top. I don't think I'd like to try that.
- GrumpyNl 9y agoThe tail wont hit the ground because the engineers designed the tail in a way so it wont hit the ground.
- mulmen 9y agoIt is very easy to cause a tail strike. The article provides multiple examples of how this can and does happen.
- devnonymous 9y agoWhy aren't people reading the article? Yes, as engineers we tends to rationally think and come up with seemingly plausible explanations but like 3 comments out of the current 8 seemingly didn't even bother validating their theory or verifying whether the article offered an explanation! News for hackers indeed!
- brian-armstrong 9y agoYes, this is a frustrating trend. It would be nice to see ~2-week long posting bans handed out for this sort of behavior
- hk__2 9y agoNote that insinuating people haven’t read the article is itself against HN’s guidelines [1]. [1]: https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- twic 9y agoThis always reminds me of the rule that in parliament, MPs cannot accuse each other of lying [1]. People do it, we all know they do it, and it's a genuine problem that they do it - but we're not allowed to talk about it! [1] https://www.theguardian.com/notesandqueries/query/0,5753,-2245,00.html https://www.theguardian.com/notesandqueries/query/0,5753,-22...
- kbenson 9y agoThe solution there is the same as here. Point out how people are wrong, and if egregiously so, make it obvious that is the case. Replying "The article mentions this exact case and explains it" Is sufficient.
- marak830 9y agoIs it accuse people of lying or present proof that they are either wrong, or knowing lying? Otherwise I could just had me and a few friends constantly telling everyone that anything I don't like, is lying.
- jokoon 9y agoI remember seeing somewhere that some planes were fitted with some wooden ball on the tail so it can touch the ground.
- chrisseaton 9y agoI think Concorde had a wheel on the tail.
- dingaling 9y agoAnd the Soviet Il-62. It was actually smarter than the more elegant British VC-10 as it permitted the centres of pressure ( wing position ) and gravity to be optimised for cruising rather than remaining in its main gear whilst in the ground.
- liorn 9y agoThe cockpit recording from Japan Airlines Flight 123 (which crashed due to improper repairs of tail strike damage 7 years earlier) is chilling. https://www.youtube.com/watch?v=Xfh9-ogUgSQ https://www.youtube.com/watch?v=Xfh9-ogUgSQ
- wyldfire 9y agoWow, that was a scary recording. From the wikipedia article [1]: > Casualties of the crash included all 15 crew members and 505 of the 509 passengers > ... > deadliest single-aircraft accident in history, the deadliest aviation accident in Japan, the second-deadliest Boeing 747 accident and the second-deadliest aviation accident after the 1977 Tenerife airport disaster. > ... > During the investigation, Boeing calculated that this incorrect installation would fail after approximately 10,000 pressurization cycles; the aircraft accomplished 12,318 successful flights from the time that the faulty repair was made to when the crash happened. > ... > In the aftermath of the incident, Hiroo Tominaga, a JAL maintenance manager, killed himself to atone for the incident, while Susumu Tajima, an engineer who had inspected and cleared the aircraft as flight-worthy, committed suicide due to difficulties at work. [1] https://en.wikipedia.org/wiki/Japan_Airlines_Flight_123 https://en.wikipedia.org/wiki/Japan_Airlines_Flight_123
- kbenson 9y ago> > In the aftermath of the incident, Hiroo Tominaga, a JAL maintenance manager, killed himself to atone for the incident, while Susumu Tajima, an engineer who had inspected and cleared the aircraft as flight-worthy, committed suicide due to difficulties at work. That sucks. If ever there were two people that knew first-hand how important it was to get right and would have worked to make sure that accident, and likely others as well could never happen on their shift, those were them. Suicide as atonement is a stupid, counter-productive cultural norm (and hopefully it's much less of a norm in any modern society where it exists).
- wallace_f 9y agoInterestingly, at the end of WWII, when Tojo was captured by the Americans, he shot himself in the abdomen--creating referencss fo seppuku--and apologized that "I am taking so long to die." Not long after, he was tried for war cimes and executed by hanging. I'm sure he would have rather have died from the gunshot. Whether right in some cases and wrong in others, I think it's difficult to say cultural norms are simply and plainly wrong.
- jotjotzzz 9y agoOmg, scary stuff. How can we check the planes we are boarding have never had this airstrike repair? Sounds crazy.
- mulmen 9y agoYou can't and without specialized experience you probably wouldn't know what to look for anyway. This is why we have regulatory structures in place to ensure airworthiness.
- Animats 9y agoTail-draggers died out for larger aircraft partly because the slanted cabin when on the ground was inconvenient. The DC-3 was the last successful tail-dragger airliner. Wolfgang Langewiesche, in his 1944 classic, "Stick and Rudder", writes that the tail-dragger arrangement is a poor landing gear, but a good takeoff gear for underpowered aircraft. It gives the effect of flaps on takeoff for planes that don't have flaps. Tail-draggers are prone to nose-plant accidents and ground loops.[1] Worst landing gear ever - the U-2. Two inline wheel sets.[2] That's the result of extreme weight reduction. [1] https://www.youtube.com/watch?v=q5trygRQaV0 https://www.youtube.com/watch?v=q5trygRQaV0 [2] https://www.youtube.com/watch?v=-ELjCkG4Gl0 https://www.youtube.com/watch?v=-ELjCkG4Gl0