When the plane takes off, why doesn’t the tail hit the runway?

http://www.thegigamax.com/2017/10/10/plane-takes-off-doesnt-tail-hit-runway/

by skellertor • 9 years ago

59 64 9 years ago

kuhn• 9 years ago

Interesting 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

chii• 9 years ago

I'd say impressive commitment to QA'ing your product! I wish software in general, is tested to this degree.

hueving• 9 years ago

Testing 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.

zodPod2• 9 years 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

sjburt• 9 years ago

This is a normal part of pilot training. I think it's less common in large aircraft but for small planes it's not uncommon.

nunez2• 9 years ago

Recovering from a stall is something you learn very very early into flying

Doxin• 9 years ago

I'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

zodPod2• 9 years ago

I'm going to reply here because multiple people said it:

I'm aware that stall training is a common occurrence but the difference here is that you're testing with a plane that is massive and may have no nearly been tested as much before. What struck me was the "Make sure it can recover" it's not a test for the pilot's training to see if he can recover it. It's testing the plane's capability to recover. Sure the pilot could still end up recovering it if it doesn't but the sheer size of this plane is what mostly made me surprised!

forgotmysn• 9 years ago

i 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• 9 years ago

Or that the tail doesn't hit the runway because it's angled upwards.

KGIII2• 9 years ago

I 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.

mulmen5• 9 years ago

That doesn't prevent tail strikes. The article provides many examples of how the (angled) tail of an aircraft can strike the runway during takeoff and landing.

goialoq• 9 years ago

horizontal velocity has nothing to do with it. It's because they gain a bit of lift before increasing angle

mulmen5• 9 years ago

Horizontal velocity and lift are at least correlated. The reason the tail of the plane does not strike the ground in a proper takeoff rotation is because the pilot make sure the aircraft has sufficient speed (and indirectly, lift) to perform the rotation maneuver. The airspeed at which the rotation can happen is calculated based on weight and loading.

skj• 9 years ago

Perhaps an entire page is needed to explain that what you suggest is not at all the reason :)

GrumpyNl• 9 years ago

The tail wont hit the ground because the engineers designed the tail in a way so it wont hit the ground.

mulmen5• 9 years ago

It is very easy to cause a tail strike. The article provides multiple examples of how this can and does happen.

devnonymous• 9 years ago

Why 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• 9 years ago

Yes, 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• 9 years ago

Note that insinuating people haven’t read the article is itself against HN’s guidelines [1].

[1] https://news.ycombinator.com/newsguidelines.html

marak8304• 9 years ago

Well I have read the article, I have nothing to add directly, yet I have commented twice in reply to other comments.

Should I get a 2 week ban for bot commenting directly? Perhaps people want to discuss some issues raised or some side issue/interest about the article?

We are here to discuss afterall, and I am more than a little disappointed to see someone being upset for comments that may be to the side of the article.

If they were all political posts, okay I could understand, but they arnt.

Edit: I am reading the top third comments, most popular threads bottom thirds are, well ignored for a reason(and hence downvoted)

autokad• 9 years ago

i read it, and now i am looking for articles on the 4 survivors of Japan Airlines Flight 123

jokoon• 9 years ago

I remember seeing somewhere that some planes were fitted with some wooden ball on the tail so it can touch the ground.

chrisseaton• 9 years ago

I think Concorde had a wheel on the tail.

dingaling• 9 years ago

And 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• 9 years ago

The 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

komali2• 9 years ago

Oh man, that captain screaming for more power [9:30] while the "pull up" alarm is going on, that is bonechilling. Thanks for the link.

Why did he want flaps AND power? Wouldn't flaps slow the plane making it more likely to stall?

diabeetusman• 9 years ago

Flaps do increase drag (especially at higher speeds) but they also decrease the stall speed which is why they're deployed during takeoff and landing-- they allow a slower takeoff speed. In effect, at lower speeds, the lift increase has a bigger effect than the drag.

dragonwriter• 9 years ago

Flaps reduce stall speed as well as inducing drag; in the very short term, they prevent stalls.

wyldfire2• 9 years ago

Wow, 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

kbenson3• 9 years 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_f4• 9 years ago

I've just been reading a bit on the aftermath and what is amazing to me is that Boeing apparently paid nothing in compensation or liability, but JAL did, despite the accident being nearly entirely the fault of Boeing!? Does anyone know why?

swendoog3• 9 years ago

I already had SEVERE fear / anxiety of flying before this video. I'm not sure I'll ever fly again. FML.

marak8304• 9 years ago

Well cars don't have drive recorders, they seem to cause a lot more deaths and probably should.

I think a lot of people have anexiety for flying, I useto for a while. The best recommendation I could give to get over that (or at least to mitigate it a little), is to do some flight lessons. I actually conpletly switched deom being nervous to wanting to fly fairly quickly :-)

nunez2• 9 years ago

Note that this is a historical accident that hasn’t happened since and that accidents in aviation are extremely uncommon. You’re significantly more likely to get T-boned by a driver on their phone browsing Facebook than you are to encounter a minor incident in the air.

You should read Cockpit Confidential; it’s a great book written specifically to address your concerns

jotjotzzz• 9 years ago

Omg, scary stuff. How can we check the planes we are boarding have never had this airstrike repair? Sounds crazy.

mulmen5• 9 years ago

You 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.

throwawayjava• 9 years ago

The 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...

[2] http://www.airliners.net/forum/viewtopic.php?t=775483

[3] http://aviationweek.com/advanced-machines-aerospace-manufact...

neurotech1• 9 years ago

If 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.

Animats• 9 years ago

Tail-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 [2] https://www.youtube.com/watch?v=-ELjCkG4Gl0

When the plane takes off, why doesn’t the tail hit the runway?

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