View Full Version : Korean 773 Blows MLG on ldg with clip ...
JanetFlight
30th Jun 2018, 03:45
Hummmm....not a good week at all for Korean Aviation ... https://www.pprune.org/images/smilies/sowee.gif
https://www.youtube.com/watch?v=gtR4Dnct2iAhttps://cimg7.ibsrv.net/gimg/www.gmforum.com-vbulletin/640x425/kal_3f443fae918114daf38f28db2274d502acf5e311.jpg
Capn Bloggs
30th Jun 2018, 05:48
If it's a Boeing, I'm not going! :}
India Four Two
30th Jun 2018, 06:08
Well, that Boeing is certainly not going anywhere for a while!
A bit of PIO low down but the actual touchdown didn’t look too hard?
FullWings
30th Jun 2018, 07:54
Yeah. A little bit wobbly but I’ve done far worse than that. Looks like some kind of failure in the right gear assembly, not necessarily related to the touchdown. Main gear steering problem, perhaps?
wiggy
30th Jun 2018, 07:58
A bit of PIO low down but the actual touchdown didn’t look too hard?
Must admit having looked at it a couple of times I’ve been thinking similar...
Sure there’s what looks like period of what looks like roll PIO and also what appears to be a fairly dramatic but brief reduction in pitch attitude at one point but it doesn’t look like the ROD was massive at touchdown and it doesn’t appear that the truck was thumled into the ground due to a high roll rate...but appearances can be deceptive so it will be interesting to see what “g” was recorded...wonder if we ever will?
Fullwings: just seen your comment about maingear steering - looking at the image of the gear I see what you mean...
Capn Bloggs
30th Jun 2018, 08:04
Interesting to see how the forward wheels aren't taking much weight: the poor centre wheels is almost squashed to the ground!
msbbarratt
30th Jun 2018, 08:20
That appears to be a little bit more than a blown tyre.
Nicely understated! Wheels all wonky, etc. One wonders how much harder it'd have to have been for the gear to have collapsed. Sturdy things.
You can see a certain wobbliness in the approach, quite a lot of yaw to the right just before touchdown (I can't see right rudder being applied), lots of up-elevator just as its touching down, and a boot full of left rudder as the right hand gear gets mushed into the runway. I don't know if it's just the video compression hiding things or not, but the left rudder seems to be applied very suddenly. It looks like it was quite blustery - the grass is getting blown around a lot. Just a bad day at the office? ACMS pointed out that the touchdown itself didn't look very hard. I wonder if it was quite hard, and a lot sideways?
Big Enos Burdette
30th Jun 2018, 08:54
https://cimg9.ibsrv.net/gimg/www.gmforum.com-vbulletin/750x453/korean_b773_hl7573_tokyo_180629_1_c1bc869473218d5f0e963c55ce 0963938064f0df.jpg
Assume there is a cycle life limit on the landing gear. Any more info about that? The landing itself looks not that bad and no tire did burst. The banana ist still straight so I doubt that this was a hig G landing.
BAengineer
30th Jun 2018, 12:28
Steering axle failed - possibly corrosion?
cappt
30th Jun 2018, 14:10
The gear probably gave up after numerous wonky landings.
A0283
30th Jun 2018, 15:13
Blocked wheels righthand...?
But visible part of tyres dont look that bad..
so would require flat spots on the opposite side...
Would not be enough for an axle overload like that...
Wobbly approach...
what if it had blocked wheels and touched down rh first?
Would have to look at that on a bigger screen than this mini ipad...
NWA SLF
30th Jun 2018, 19:45
Since its a 300, can the actuator for the levered gear lock so all the weight remains on the rear as it settles down? It appears from the rear view picture that the rears are pointing toward the engine like the rears were taking a heavy side load as it touched down, but it also needed a heavy vertical load to camber them apart like that. Looks kind of like a friend's car when the shop dropped it off their lift.
FullWings
30th Jun 2018, 19:47
I like the guy in the photo: “Hmmm, I’m pretty sure it’s not meant to do that...?"
An interesting failure mode. The (titanium?) shaft that forms part of the bogie appears to have split underneath and allowed the rear wheels to rotate upwards. I would be surprised if this isn’t some kind of defect as you’d expect the tyres to go before the undercarriage starts coming apart...
DaveReidUK
30th Jun 2018, 20:04
Since its a 300, can the actuator for the levered gear lock so all the weight remains on the rear as it settles down?
If you're referring to the semi-levered gear, that's only on the 777-300ER. This was a 777-300, not an ER.
BAengineer
1st Jul 2018, 01:18
I like the guy in the photo: “Hmmm, I’m pretty sure it’s not meant to do that...?"
An interesting failure mode. The (titanium?) shaft that forms part of the bogie appears to have split underneath and allowed the rear wheels to rotate upwards. I would be surprised if this isn’t some kind of defect as you’d expect the tyres to go before the undercarriage starts coming apart...
There was a special check some years ago for corrosion in the axles of 777's - thought all the aircraft worldwide would have been inspected by now though.
underfire
1st Jul 2018, 12:37
HD version shows it much better, a float, then a sudden pitch down on right landing gear. (note that on youtube, when in HD, under settings, you can have the video play at 0.25 speed)
https://cimg3.ibsrv.net/gimg/www.gmforum.com-vbulletin/913x357/hdfull_f1b66abd5a1e00b78302a8065ce0a89c10ae6255.jpg
Nailed it! (the landing that is) Right gear hits so hard that left gear comes off runway)
https://cimg4.ibsrv.net/gimg/www.gmforum.com-vbulletin/911x320/fullhd2_b0583ffdaccf0c3fadcf2c858353aa8c4f0ef9e0.jpg
Now the rebound from the right hitting so hard
https://cimg7.ibsrv.net/gimg/www.gmforum.com-vbulletin/883x319/hdfull3_1173aa98836bcd2c9688d52540602166b2d0ee9d.jpg
Capn Bloggs
1st Jul 2018, 13:18
4 Reds! Unstable! Go Around! :cool:
Nailed it! (the landing that is) Right gear hits so hard that left gear comes off runway)
You will note that the left bogie is almost flat, meaning it is on the ground...
Cloudtopper
1st Jul 2018, 14:20
I note , no one here has mentioned the sparks from the right MLG after touch down , followed by occasional smoke trailing behind .
nonsense
1st Jul 2018, 14:23
You will note that the left bogie is almost flat, meaning it is on the ground...
It has *been* on the ground, but as the aircraft has bounced back upwards, it has been lifted off the ground and has not had time to tip back to the usual "dangling" orientation on approach.
underfire
1st Jul 2018, 14:42
You will note that the left bogie is almost flat, meaning it is on the ground...
It has *been* on the ground, but as the aircraft has bounced back upwards, it has been lifted off the ground and has not had time to tip back to the usual "dangling" orientation on approach
That is correct nonsense. If you watch the video in slo-motion, you see it has been lifted up off the runway. You can see the puff smoke is behind the gear from the momentary touch, and when watching you can see the left gear land again. Too many frames to post here...
Capn Bloggs
2nd Jul 2018, 00:03
Having gone backwards and forwards through the video a few times, it looks to me the left wheels do not leave the ground after the first touch. Look at the left engine's height above the ground.
It looks to me that, through no action on the crew's part, the right wing dropped at the last second and the right bogie touched firmly. In my view, the PF had the aeroplane nicely set up for a decent touchdown until the @#$% dropped out of the right wing.
Also of interest is the sparks start well after touchdown, indicating the axle may not have given way on touchdown, but later on.
Unlucky...
Having gone backwards and forwards through the video a few times, it looks to me the left wheels do not leave the ground after the first touch. Look at the left engine's height above the ground.
It looks to me that, through no action on the crew's part, the right wing dropped at the last second and the right bogie touched firmly. In my view, the PF had the aeroplane nicely set up for a decent touchdown until the @#$% dropped out of the right wing.
Also of interest is the sparks start well after touchdown, indicating the axle may not have given way on touchdown, but later on.
Unlucky...
The two applications of near full nose up deflection (aft stick) of the stab just prior to touchdown drove the mains into the runway.. Yes it was setup pretty good after all the sillyness, should have just let it settle in.
Sunamer
2nd Jul 2018, 08:42
This is not the first time KA did that type of landing.
This one is from 2012...Looks like it is pretty much identical, in terms of the PIO...
watch?v=OoK_dbLDfA0
underfire
2nd Jul 2018, 12:37
Note puff of smoke from momentary touch, then the bounce, front wheels of assembly up, (no smoke) then contact again with full smoke...
https://cimg7.ibsrv.net/gimg/www.gmforum.com-vbulletin/409x298/wheelsup_ce4d9011d3afb9d2d92fbe73be0608769689e0c5.jpg
front wheels up on bounce
BAengineer
2nd Jul 2018, 12:49
The two applications of near full nose up deflection (aft stick) of the stab just prior to touchdown drove the mains into the runway.. Yes it was setup pretty good after all the sillyness, should have just let it settle in.
I dont think the pilot did anything wrong. The gear (and specifically the axles) are designed to take harder landings than that and the fact that the rear axle failed points to mechanical failure not pilot error.
If you look at the BA 777 crash at LHR where both landing gear assemblies were ripped off and the right MLG bogie was snapped in half, all the individual axles survived intact.
Capn Bloggs
3rd Jul 2018, 00:58
Note puff of smoke from momentary touch, then the bounce, front wheels of assembly up, (no smoke) then contact again with full smoke...
No. That smoke is from the rear wheels. The front wheels haven't even reached the ground yet. The next few frames clearly show another large cloud of smoke when the front wheels touch down. There is no bounce.
GordonR_Cape
29th Sep 2019, 15:50
Corrosion cracking caused Korean Air Boeing 777 main gear axle failure on landing: http://newsinflight.com/2019/09/29/corrosion-cracking-caused-korean-air-boeing-777-main-gear-axle-failure-on-landing/
Meester proach
30th Sep 2019, 12:30
A bit wobbly, but you’d need to be closer to see what the actual touchdown was like. I’d be surprised if it was that bad though.
Anyone know what peak G the BA777 hit in the LHR glider incident ?
Speed of Sound
30th Sep 2019, 12:53
Anyone know what peak G the BA777 hit in the LHR glider incident ?
2.9g oooooooooooooooooooo
PerPurumTonantes
30th Sep 2019, 14:29
2.9g oooooooooooooooooooo
= 638 tonnes :eek: No wonder it got a bit bent.
It is initially a stable approach, with a bit of low level corrections going on, but none of the magnitude needed to overstress the MLG. The touchdown shock is extended over the wheel un-tilting, and the compression of the MLG shock. That looks to have been within the normal limits in the video. The landing loads assume symmetrical loading across the MLG, however the single gear impact has to be considered.
I would be suspecting corrosion fatigue of the attach section around the steering bearing. It doesn't appear to be the axles, it appears to be a failure of the structure around the vertical bearing.
Speed of Sound
30th Sep 2019, 16:59
I would be suspecting corrosion fatigue of the attach section around the steering bearing. It doesn't appear to be the axles, .
“Japanese investigators of Korean Air Boeing 777-300 that suffered serious damage to its rear wheel axle of the main landing gear conclude that corrosion contributed to failure.”
Meester proach
30th Sep 2019, 21:45
2.9g oooooooooooooooooooo
Is that all ? Enough to shove the main gear through the wings. Seeing as Boeing hard landings start at 1.8 G , I’m quite surprised how low
“Japanese investigators of Korean Air Boeing 777-300 that suffered serious damage to its rear wheel axle of the main landing gear conclude that corrosion contributed to failure.”
thanks.
I went back later and read the report after my post.... the report was well done. The aft bogie has the hardest time of loads on takeoff and on landing. It is subject to higher torsional and bending loads than the other axles.
[The B777 has great control authority and handles crosswinds well. Looking back in some data I see one particular TO in that tail number that got a 46kt crosswind gust on the takeoff, and required much less than full rudder to maintain centerline. It does exhibit spoiler walkdown but only when there is a lot of wok n' roll going on. This incident should indicate that SIWL is a factor to consider if wing down is being contemplated as a XW technique. I have to dust off notes on a investigation I did years ago on a series of gear trunnion failures that were occurring to a carrier, the gear was quite often coming up through the upper spar cap which makes for a long day. Through the cobwebs however, the inputs immediately before touchdown and the touchdown attitude can alter the magnitude and type of loads that the gear is subjected to
One oddity of the 777 was a weirdness of directional stability in a strong crosswind, at low speed... rather surprisingly with strong crosswinds, the plane initially has a tendency to turn away from the wind. Once some speed has been achieved on the roll, this reverses slightly to a more normal weathervaning tendency. Another slight oddity is that in stable strong crosswinds, the aircraft responds to a rudder alignment prior to touchdown by effectively jacking the tail upwind, and the cockpit offset from the centerline doesn't come back towards the centerline quite as it does with say, the B747, or 757/767/737. Nice plane though, pity it has so much fuel on board]
procede
2nd Oct 2019, 10:53
Is that all ? Enough to shove the main gear through the wings. Seeing as Boeing hard landings start at 1.8 G , I’m quite surprised how low
The main issue was that touchdown was on the grass before the runway. That probably limited the vertical loads, but also meant the gear dug in and was sheared off.
UltraFan
3rd Oct 2019, 06:48
If it's a Boeing, I'm not going! :}
More like "If it's a Boeing, IT's not going". :)
UltraFan
3rd Oct 2019, 06:57
Yeah. A little bit wobbly but I’ve done far worse than that.
I've aborted at far less. Definitely a try-again landing. You don't play games with a 73-meter airliner full of innocent bysitters. My guess would be a "veteran", "ex-air-force" captain, "the right stuff", and very young inexperienced FO. And my bet would be, the FO called for abort... in a whisper. Korean Air 8509 comes to mind. Followed by the general Korean Air's reputation. Could've been much, much worse.
hans brinker
3rd Oct 2019, 18:20
I've aborted at far less. Definitely a try-again landing. You don't play games with a 73-meter airliner full of innocent bysitters. My guess would be a "veteran", "ex-air-force" captain, "the right stuff", and very young inexperienced FO. And my bet would be, the FO called for abort... in a whisper. Korean Air 8509 comes to mind. Followed by the general Korean Air's reputation. Could've been much, much worse.
Those are some bold assumptions based on a cellphone video, maybe keep it down a little till the report comes out.