Yakutia Superjet at Yakutsk - runway overun and ldg. gear collapse
 

Accident: Yakutia SU95 at Yakutsk on Oct 10th 2018, overran runway on landing

I'm trying to understand, how could the main gear of a commercial aircraft collapse without affecting the nose gear? Surely the main gear should be capable of withstanding all sorts of landings. I wouldn't expect to see it collapse from going over a little ledge.

Any ideas?

Based on this YouTube video



I'm not surprised that the mains collapsed.

It shows the discontinuity in a section of the runway that was apparently being resurfaced. It's possible that the NLG encountered a section with a less abrupt transition than the part encountered by the mains.

I've just read the NOTAM and it seems the runway 23R was closed for landings. Should have been used for departures only.

However, this landed on 23L.

Thankfully nobody was seriously injured.

At approx 0:10 in the above you can see three distinct ramps the gear has made up the 'step' in the runway. That's a strong NLG then.

Doesn't the text say they landed on 23L, which seems to be allowed by the NOTAM?

The previous poster (timestamp 10th Oct, 22:58z) has an interesting explanation of the apparent survival of the nose gear: the nosewheels were still in the air (according to that explanation) and so did not hit the surface discontinuity at all.

That suggests a sudden deceleration thereafter like in a tailhook-arrested landing! (I admit some quite different Sukhoi twinjets are indeed capable of such techniques.)
Note that the aircraft came to rest 65 m beyond the edge of the higher runway surface.

What I have read in the Aviation Herald (link is in opening post):

The aircraft landed on 23L.
The southwesterly 1150 m of that runway has been taken out of use for reconstruction so that the remaining 23L LDA is only 2248 m instead of more than 3 km.

It appears to me then that the aircraft _may_ have landed long (floated) in the approx. 5 kt tailwind (landing on the last two-thirds of 05R not available), and/or it did not or could not brake sufficiently.
As a result, it overran the end of the available landing surface (maybe now braking heavily) and some 150 m further ‘down the road’ broke through construction barriers, and then 30 m beyond those barriers hit the edge of the higher newly reconstructed pavement.
The nosewheel may have been lucky to roll exactly over a temporary earthen ramp (upslope) that enables construction vehicles to climb the edge to the new surface.
The main gears were less lucky and also may well have been braking heavily.

Airfield elevation is 325 feet. The stated QFE will be in mm Hg. And the wind is in metres per second.

Plumb bob :D

The aircraft may also have completed its landing roll with the nose wheel firmly on the ground, crew see the trench at the last second and instinctively pull back on the control column raising the nose enough for it to pass over the depression, main wheels not so lucky.

I'm going with Plumb Bob's theory.

In fact I suggested pretty much the same thing in my earlier post, so he must be right. :O

My turn to be embarrassed ...
I admit that it was your theory in the first place!
The core of my explanation was indeed completely derived from the completely clear and unambiguous video you provided and (as far as necessary) commented upon in the first place.
I would never have taken up the pen, if not for at least trying to counter the later and quite deviating explanation that I reacted to.

The MEL reported the right hand reverser was unserviceable, which meant both were unusable. Also with M04 the runway was icy, but not yet reported by ATC.
.

As to the gear anomaly - is it not true that the weight distribution in most pax jets is about 92% main gear, 8% nose gear? Seems like that would make it easy for the nose gear to "hop" while the main gear "crunched."

As to the cause - as scifi alludes to, runway friction (with ice) was apparently about 60% of that reported to the crew, and possibly even to ATC itself. (.27 vs. .44)

That loading is about right. If you get out of sorts with it, then you get a fairly unpleasant rotate transition from ground to air, where the aircraft needs a large elevator input to rotate, and immediately the MLG come off the ground the elevator input has to be reduced to avoid an excessive pitch rate. There is at least one aircraft that this is a daily irritation on, takes away from an otherwise pleasant handling aircraft.

Of course, the nose gear has a lighter structure to reflect the lighter loads it sees. And braking (such as it was) would have tend to transfer load to the nose gear.

Maybe the pilot was a mountain bike rider and released the brakes and hauled back on the yoke at just the right time :O.

Probably at the end of the run the effect of hauling back on the yoke would be small because airspeed is slow? One might say that every little bit helps though.