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Aeroflot Superjet 100 fire and evacuation at UUEE

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  • Evan
    replied
    Originally posted by BBC
    Pilot Denis Yevdokimov told Russian media that the lightning had interrupted communication with air traffic controllers and forced him to switch to emergency manual mode.
    Originally posted by BBC
    Russia's transport ministry has decided against grounding Superjet-100s, saying there is no obvious sign of a design fault.
    Hmmmmmmmmmmmmmmmmm. Ok, a grounding might be a bit hasty, but obvious signs of design faults...?

    Well, a lightning strike (not such an uncommon event) apparently knocked out the radios and the flight-control computers (if not the entire primary electrical system). That's not supposed to happen. There are rare forms of lightning that will exceed protections, but the odds of this are remote.

    And a hard landing resulted in breached fuel tanks. That's not supposed to happen either. So I think there is reason to say there are obvious signs of design faults here.

    Start with lightning protection. Are the composite conductive layers adequate? Is there any vulnerable area? What about transient protection and surge suppression of vital avionics? Is it adequate?

    Then I would want to know how a hard gear-collapse landing could result in a fuel tank breach. Does something need to be structurally rethought there?

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  • Gabriel
    replied
    On May 6th 2019 Roaviatsia (Russia's CAA) reported a static atmospheric discharge at about 2100 meters (6900 feet MSL) resulted in the failure of the radios and other equipment including the autopilot. The crew returned to Sheremetyevo squawking loss of radio contact, subsequently emergency. While landing on runway 24L the aircraft experienced a rough landing, bounces and partial destruction of the aircraft. Following the 4th touch down fire broke out at the tail section of the aircraft and the aircraft veered left off the runway coming to a stop between taxiways A2 and A3. The aircraft burned partially out, there were fatalities and injuries.
    http://avherald.com/h?article=4c797dd7&opt=0

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  • Evan
    replied
    Originally posted by brianw999 View Post
    Every passenger in possession of hand baggage should be prosecuted for manslaughter.
    And you don't think they could claim 'temporary insanity'? Have you seen that interior video?! Let he who has waded through the fiery aisles of Russian aviation with a clear head cast the first stone.

    Leave a comment:


  • brianw999
    replied
    .....and yet again passengers get their hand baggage before evacuating. From what little I saw of the evacuation there seemed to be a distinct pause in front of each passenger seen with hand baggage. That equals a delay to other passengers evacuating and must surely have contributed to some of the deaths.
    Every passenger in possession of hand baggage should be prosecuted for manslaughter.

    Leave a comment:


  • Evan
    replied
    Originally posted by Gabriel View Post
    Well, it shouldn't. Fuse pins are there to prevent that hard landing loads transfer to the wing spar which then acts like a fuse itself. Like in the several DC-10 and MD-11 hard landing accidents where one of the wings pars failed, the airplane lost that wing, and the plane rolled inverted engulfed in flames. A fuse pin is NOT there to prevent the landing gear strut from going through the wing tanks, rather the opposite, sort of. The compression fuse pin is supposed to fail under high landing gear compression stress and let the strut go through the wing, except that there should be no fuel tank there because the landing gear assembly is located behind the rear spar which is the aft end of the fuel tank.

    I suppose that the British Airways 777 accident at Heathrow was a quite harder landing.
    25 ft/s (1500 ft/m)

    That accident, being at a high descent rate on soft surface, imposed very high loads both in compression and backwards. One landing gear failed under compression while the other failed under backwards force. One of the fuel tanks (don't remember which one) was protected as per design, the other one was breached because a secondary rod (that gives stability to the assembly) failed to fail as designed, and penetrated the fuel tank. Luckily the soft and wet ground helped avoid a fire.
    Actually, both MLG failed by design for upward compression (the outboard fuse pin failed on both of the main landing gear beams). I was wondering how a vertical compression fuse pin would work, expecting it at the trunnion, but it is actually at the gear beam (an airframe attachment structure) outboard attachment.

    The left wing tank was breached a bit between the upper wing skin and the rear spar. The center tank was breached when the right gear rotated inward and the drag brace tore off the rear spar web along with part of the center tank wall. The right gear then detached, striking and penetrating the aft fuselage, breaching the oxygen cylinder manifold (venting the oxygen, thank god there was no fire) and then went airborne, striking the horizontal stabilizer.

    The fuel pipes also fractured, spilling fuel until the spar valves closed.

    But that is all to be expected from a 777 falling out of the sky. Fuel tanks should be protected against the kind of rough landing we saw yesterday.

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  • Evan
    replied
    Originally posted by Gabriel View Post
    1- Depending on how you define "the roughest landing", this can actually be a bad thing. In the same way than super solid cars that would remain almost intact after a crash but with the occupants smashed inside.
    2- And it has just been proven wrong, unless this landing was rougher than the roughest one.
    And it's not the first time the MLG has collapsed on landing.

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  • Gabriel
    replied
    We have a durable landing gear, excellent double-strut gear legs, a real work of art. They are able to endure the roughest landing without any damage.
    1- Depending on how you define "the roughest landing", this can actually be a bad thing. In the same way than super solid cars that would remain almost intact after a crash but with the occupants smashed inside.
    2- And it has just been proven wrong, unless this landing was rougher than the roughest one.

    Leave a comment:


  • Evan
    replied
    The MLG-to-wing setup:
    Click image for larger version

Name:	ssj-mlg.jpg
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  • Gabriel
    replied
    Originally posted by Alex - Spot-This ! View Post
    Videos from inside the cabin show how main gear went through the wing and remained there for the entire landing
    Link please?

    Leave a comment:


  • Evan
    replied
    Whatever the cause, a bounced landing like this shouldn't result in a breached fuel tank (or a broken wing spar). The DC-10/MD-11 had a problem with this (see Gabriel's previous post) and lessons were learned. Hopefully the investigation will focus on this.

    The wings:

    The SSJ wing has the second highest aspect ratio after the B787. Pains were taken to achieve this. The wing was optimized for cruise level flight.

    The gear:

    Originally posted by Alexey Dolotovski, Deputy Chief Designer (Aerodynamics) at SCAC
    We have a durable landing gear, excellent double-strut gear legs, a real work of art. They are able to endure the roughest landing without any damage. Of course double-strut landing gear is heavier than a single-strut one. But when a single-strut landing gear is mounted on the aircraft it turns out that the hinge fittings need to be reinforced. As it turned out the single-strut landing gear together with reinforced hinge fittings are heavier than double-strut landing gear. Our landing gear has lower weight as compared to the single-strut one installed on Embraer 190.

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  • Evan
    replied
    Originally posted by Evan View Post
    No, the breach occurs after the last impact, but before the last impact, it **appears** that the MLG is either detached or collapsed (or never extended), when there is still no fuel tank breach.
    You know what... forget it. That video is too lowres to determine anything.

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  • Alex - Spot-This !
    replied
    Videos from inside the cabin show how main gear went through the wing and remained there for the entire landing

    Leave a comment:


  • Evan
    replied
    Originally posted by Evan View Post
    No, the breach occurs after the last impact, but before the last impact, it appears that the MLG is either detached or collapsed (or never extended), when there is still no fuel tank breach.
    Maybe it's a trick of the low-res video, but have a closer look.

    https://www.youtube.com/watch?v=HG3_clcQIFI

    Leave a comment:


  • Evan
    replied
    Originally posted by Alex - Spot-This ! View Post
    Yes, main gear went through the wings and tanks after first hard contact, setting everything on fire.
    No, the breach occurs after the last impact, but before the last impact, it **appears** that the MLG is either detached or collapsed (or never extended), when there is still no fuel tank breach.

    Leave a comment:


  • 3WE
    replied
    Originally posted by Gabriel View Post
    The fire should not have gone into the cabin so easily. Unless the landing was harder than I think and the fuselage itself broke.
    I think the landing was harder than you think.

    Evidence: A very large fire that went into the cabin.

    If you hit hard enough, there's things besides the landing gear that rupture fuel tanks. (Evan's nacelles included)

    Originally posted by Gabriel View Post
    Perhaps it was the smoke, not the fire, what initially disabled the passengers who could then not escape.
    ...or impact injures...The 90-second evacuation is usually done with healthy, mobile folks who are mentally prepared, in a not_smoke-infested cabin, AND not really in danger, since it's usually a simulation.

    Leave a comment:

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