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Sheremetyevo Superjet 100 in flames

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Sheremetyevo Superjet 100 in flames

Old 5th Jun 2019, 08:08
  #441 (permalink)  
fdr
 
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Originally Posted by tdracer View Post
Which time? The first bounce appears fairly benign, second is worse, third bounce all hell breaks loose.
The question remains - was the lightning (or other) induced systems damage so bad as to make the aircraft very difficult to fly, or did the crew botch what should have been a straight forward landing of a perfectly flyable aircraft?

thanks to longtimers post of some detail...


The aircraft is FBW, and has a similar control arm rest to Airbus designs. The aircraft has had an electrical systems failure and has reverted to direct law, and whatever gains that has in it for deflection of the SSC to control surface movement. Flying in windshear in such conditions is going to be a learning experience for the pilot. As I understand the SSJ's architecture, SCAC incorporated some changes to the airbus ideology, that may be a factor. The design had 3 modes, normal, degraded and minimum, with minimum still retaining damping in roll and pitch, which is a step up from AI direct law. That assumes that there is still some power in the system. The event suggests a significant loss of electrical power, and that raises a question as to what happens to the minimum law when unpowered? That this may have occurred, well, the video shows a full on PIO going on, which is more than would be expected from a system with damping.

SCAC increased the length of the SSC for the SSJ compared to the AI designs. That appears to have been retained through from the electric bird and initial sim, through design of the software by Liebherr, and on to the aircraft before and after RA-89098 MSN's. The design of the ATR was also changed from AI, SSJ elected to go part Boeing and incorporated servo control of the ATR to remove the no motion design towards more conventional designs as in the 777/787. The trim system also diverged from AI, AFAICS, SSJ has no trim pickle on the SSC, so follows AI design there rather than Boeing's, but does not have pitch trim wheels as the AI aircraft have had in their FBW design, it has a set of pickles on the rear of the pedestal. That is interesting in itself. It raises the question whether the FBW control stayed faithfully to the C* AI type design, (no speed trim input by the pilot in manual flight normal control law) or headed off towards, C*U, like the 777/787, where indexing of the speed is applied by the trim switches on the yoke. As the laws are enhanced from AI, while it looks a lot like C*, it may not be, it may have advanced towards a more advanced system, such as Dassault or Embraers later FPARC/FPAH type control law design. I digress; but only slightly. Cuz... the SSJ pilots are confronted with a major power loss, that appears to possibly have brought them into a new law, that is not part of the design, (I am way out in the breeze with this... but think it through before shooting...) The most degraded law still requires electronic input, which does not appear to have been available. Trim is by electrically actuated trim switches, not a wheel, and therefore is effectively FBW... the guys flying this probably have never before encountered a no trim available, out of trim, reduced capability below the minimum design trained degraded laws. Thats the worst case, and the guys would get a bit of slack for getting out of sorts. The slightly better case is that the aircraft is operating at minimum laws, but is in known windshear conditions, with manual flight for thrust and flight controls, necessitating input from both at the same time. The trim switches are.... way way way back out of the normal control handling, and that may result in the plane being out of trim purely by that cause. The guys are pitching and altering thrust, and those all result in moments that are being controlled by a system that is very dependent on minimising the random control input of the pilots arm, the reason the AI, SSJ, Dassault etc have configurable rests on the control side of the seat, to ensure that PIO's are avoided. Just add turbulence.

There is no question that the aircraft encountered a PIO (as defined by MIL-HDBK-1797A), it is not the first to do that, and won't be the last. Oddly, one major FBW system had a history of APIO... even electrons can get it wrong. The question is why did that happen, and in understanding that, perhaps until the TsAGI modelling of the actual architecture and conditions that the crew encountered is known, then I would back off throwing allegations of incompetence to the pilot. It potentially highlights an area of operation of electrojets for all driving those types, that if you have degraded laws, you may well consider having very simple conditions for your approach, to avoid finding out whether you end up on the wrong side of the Nyquist stability plot. O Caesar, thou art mortal, thou art mortal....

The indignation over this event appears to be railroading a quite competent design, that is a potentially valuable asset for the Russian civil economy. It would be a shame to bury the design through lack of understanding, where some comprehension may well easily remove the potential for such untidy outcomes. The loss of electrical systems may well be the bigger issue here to resolve to make the plane successful.

The SSJ in service appears to be disadvantaged by poor documentation, a poor MCD that is out of step with modern designs that the aircraft is, and lack of spares. These are symptoms of lack of funding. On the other hand, it is probable that it can be produced at a competitive price, be reliable as most Russian designs are. It needs additional support and understanding from customers in order to succeed, and possibly some fine tuning of the control law algorithm, additional training, and maybe a bit of extra beef in the gear-wing attachment area.

The SSJ is not the first aircraft to have some PIO potential, the MD11F at RJAA 34L is just one of many examples, as is the JAS Gripen, and the F22 in early days of test.




(Anyone with more information on the laws of the SSJ, please PM me)
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Old 5th Jun 2019, 09:37
  #442 (permalink)  
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Originally Posted by DaveReidUK View Post
Well they would, if they had any in their fleet or on order. They don't.
They do have 20 on order .(which according the same Moscow times quoted before, they consider cancelling).
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Old 5th Jun 2019, 11:03
  #443 (permalink)  
 
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Originally Posted by ATC Watcher View Post
They do have 20 on order .(which according the same Moscow times quoted before, they consider cancelling).
Those won't be flying Aeroflot passengers, nor in Aeroflot colours, which was my point:

Originally Posted by SamYeager View Post
Never mind, Aeroflot will be able to fly their passengers in the super safe B737 MAX instead...…..
Pobeda deal for 20 737 Max includes high-density option

But yes, Pobeda is owned by Aeroflot ...
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Old 5th Jun 2019, 11:39
  #444 (permalink)  
 
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Question

Just out of interest, is anybody else missing Kulverstukas input on this thread. Not like them to miss a major thread on their doorstep.
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Old 6th Jun 2019, 05:16
  #445 (permalink)  
 
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[color=left=#000000]State officials and airline executives say the airliner spends about half its time on the ground undergoing maintenance, and can fly only about a third as much as foreign-made rivals in a 24-hour period when in use.[/color]

[color=left=#000000]They blame a lack of readily available spare parts and the complexity of servicing its engines.[/color]
(from up_down_and_out's link)
Even if the two crashes are unrelated to the aircraft, if it takes that much maintenance and can't average at least 8 hours/day utilization, no one's going to want it regardless of how cheap they can sell it.
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Old 6th Jun 2019, 08:09
  #446 (permalink)  
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Originally Posted by tdracer View Post
(from up_down_and_out's link)
Even if the two crashes are unrelated to the aircraft, if it takes that much maintenance and can't average at least 8 hours/day utilization, no one's going to want it regardless of how cheap they can sell it.

That is true at present but doesn't need to always be so. Changing from an IRAN style maintenance program to something like MSG-3 or phase programs takes some time but is not impossible. The aircraft is relatively conventional, and should not need more maintenance overhead than any other aircraft made of the same materials doing the same task. I've only flown some former CIS military jets and helicopters, but they are build solidly. For the same vintage western aircraft, they are comparatively rugged in design, and usually well thought out. The engines can be a pain, but these ones seem to have been well designed. Redoing the maintenance program to make it rational is a matter of will to do so, rather than cost or even time.

It seems to be a shame to trash a fundamentally competent design for the sake of lack of will to make it work. The losses of the SSJ to date have primarily been crew related, that means there is an opportunity for a 142 program to provide appropriate training. The production system appears to be well put together, and the spares availability is again a lack of will and funding rather than inability to provide an effective supply chain. The most recent accident may have brought up a possible PIO issue in some situations, but that is able to be cured, even for the total electrical failure case that may be novel in the latest event. Overall, I would consider that it remains a viable candidate for support from the Govt to get it going as an export product and for domestic operation.

Relationships across the border may be fragile at this time, but international trade works to break down borders through self interest, and that is the problem with the direction that is being followed in the land o the great PX at present, building barriers increases risk of conflict, same to the former CIS products, countries that are trading with each other tend to avoid hot conflicts.

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Old 6th Jun 2019, 11:59
  #447 (permalink)  
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To me it's very simple: flying in direct law at higher speed in crosswinds IS DIFFICULT.
Simple as that.
Captain screwed the flaiir.
Period.
He overcontrolled.
He smashed his aircraft on the runway.
End of story.

I've hated airbus from the first day I transitioned from Boeing, for various reasons.
The change in feeling and reaction to the same side stick input, if in direct law, is another insult to the pilot's basic instincts....
If superjet is the same, and if it is true, as I've got no difficulties to believe, that the worst pilots in Aeroflot get to fly it instead of A and B, then everything is clear to me.
Public must realise that, contrary to what they'd like to think, their lives are still in pilots hands, literally, and an apparently insignificant difference in hands, makes the difference between life and death, let it be in Indonesia, Ethiopia, or Russia....
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Old 7th Jun 2019, 14:16
  #448 (permalink)  
 
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https://www.flyingmag.com/sukhoi-superjet-encountered-windshear

​​​​​​

Sukhoi Superjet Encountered Windshear

Aircraft experienced massive g forces when it touched down.

By Rob Mark

06/06/19

The Russian Ministry of Transport’s initial findings into the May 5 Sukhoi Superjet accident at Moscow’s Sheremetyevo Airport said the crew received a windshear alert in the final minutes of the flight. Moments later, Aeroflot Flight 1492 landed hard on Runway 24 Left and bounced several times before bursting into flames. Forty-one people on board died in the accident while 37 survived the crash.

About five minutes after departure, as the aircraft was flying in an area of thunderstorms about 20 miles northwest and climbing through about 9,000 feet, the crew experienced an electrical failure of unknown origin. The captain began flying the aircraft by hand. The crew managed to establish radio contact with an unknown party using its UHF radio. The Russian report becomes a bit confusing here, only explaining the crew was unable to make contact with ATC. The pilots switched their transponder to code 7600 confirming the loss of communications.

The Russian report said the Sukhoi jet executed a series of turns and once overshot the runway centerline, but 15 minutes after takeoff, eventually ended up making an approach back to Runway 24 Left for an overweight landing. The Sukhoi POH called for 25 degrees of landing flaps for this approach. Twenty-three minutes after takeoff, the crew set 7700 in their transponder although the report does not indicate precisely why.

As the aircraft descended on final through approximately 1,000 feet, the windshear warning sounded five times with, “Go around. Windshear ahead.” The crew continued the approach. At approximately 260 feet as the aircraft descended below the glide path the terrain alert sounded, “Glide Slope.” The aircraft’s airspeed increased to 170 knots.

The aircraft touched down approximately 3,000 feet beyond the runway threshold at 158 knots with a force of 2.55g before bouncing about six feet back into the air. On the third touchdown at 140 knots, the aircraft hit with a 5g vertical overload that ruptured the wing and fuel lines. Flames quickly engulfed the rear of the aircraft before it slid to a stop on the grass between Runway 24L and two taxiways. An emergency evacuation was carried out.
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Old 14th Jun 2019, 21:36
  #449 (permalink)  
 
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An interim report was published today: https://mak-iac.org/upload/iblock/c0...9098_pr_en.pdf
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Old 14th Jun 2019, 23:14
  #450 (permalink)  
 
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and it pretty much hints to pilot error (even if, as many have mentioned, direct law landing in these conditions might not be the easiest of feats).
I am still wondering if they have not added thrust after the 1st and/or 2nd bounce. The report does not address this so I guess not...
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Old 15th Jun 2019, 04:40
  #451 (permalink)  
 
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Originally Posted by atakacs View Post
and it pretty much hints to pilot error (even if, as many have mentioned, direct law landing in these conditions might not be the easiest of feats).
I am still wondering if they have not added thrust after the 1st and/or 2nd bounce. The report does not address this so I guess not...
Page 26 ff. of the report:
...During the first bouncing up, when the aircraft was in the air, the PIC switched the thrust levers to the "Maximum Reverse" mode but the thrust reverser doors did not deployed, as there were no weight-on-wheel (WOW) signals. Upon receipt of the left and right main landing gears WOW signals, the reverser doors started to deploy, which was completed after the second aircraft bouncing up movement off the RWY. There was no engine power increase as at this moment, there was no WOW signals again.
During the second bouncing up, the aircraft reached the height of ≈ 15 - 18 ft (5-6 m). In 2-3 seconds after this repeated bouncing up, the thrust levers were set to "Takeoff" mode and the sidestick was pulled to the maximum retard position. This actions may be interpreted as an attempt to perform the go-around, as before that the thrust reverser system was engaged (the reverser doors were in the open position, though starting to close), the engine thrust did not increase.
...
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Old 15th Jun 2019, 10:14
  #452 (permalink)  
 
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Good catch, somehow missed that part. Well I guess they tried but it did not actually deploy any effect.
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Old 15th Jun 2019, 16:10
  #453 (permalink)  
 
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Sounds like a cockup in intentions and actions - poor guys
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Old 15th Jun 2019, 19:58
  #454 (permalink)  
 
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Originally Posted by bill fly View Post
Sounds like a cockup in intentions and actions - poor guys

Don't select reverse until you are on the ground, don't go around after you have selected reverse....
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Old 15th Jun 2019, 21:36
  #455 (permalink)  
 
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Don't fly into a cell when everyone else is taking vectors around it. Don't perform an emergency landing and tell the aerodrome and cabin crew that it's nothing to worry about. Don't jerk the stick to the stops and back in direct law. Don't continue an approach when predictive windshear calls for go around 2.5 times. Don't continue an unstabilized approach. Don't ignore the "Glideslope" warning approaching decision height. Don't bunt into the runway. Don't respond to a bounce with full ND deflection. Don't talk to the press after doing any of that and people die.

Any other lessons here?
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Old 15th Jun 2019, 21:54
  #456 (permalink)  
 
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According to the interim report, every blame points to the "PIC". What I'm wondering is to which degree one can trust such a report being unbiased, considering that this comes from Russia and Putin has interests/prestige invested in Sukhoi. I don't know if anyone here can answer this, but how likely is this report to be unbiased and factual?
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Old 16th Jun 2019, 10:09
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Originally Posted by Nadar View Post
how likely is this report to be unbiased and factual?
It correlates well with the videos we've seen. Also it comes from the interstate committee which is quasi-independent and working in the whole CIS area. Its head (Anodina) bears a grudge against Russian authorities after their family business (Transaero) was killed in 2015.
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Old 16th Jun 2019, 16:21
  #458 (permalink)  
 
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Kulverstukas..where are you?
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Old 16th Jul 2019, 09:47
  #459 (permalink)  
 
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Originally Posted by FlightDetent View Post
I hear they do not really have bases across the country, is that so?
They have subsidiary company on Far East only and a couple of companies in Moscow related to AFL merely nominally. But they are on the way to create some hubs
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Old 16th Jul 2019, 10:31
  #460 (permalink)  
 
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Originally Posted by FlightDetent View Post
How does AFL compare to the other RF airlines, btw? I hear they do not really have bases across the country, is that so?
I don't think any Russian airlines have bases outside of their main hubs. The ones that do are the airlines formed outside of Moscow who kept their former bases after moving to Moscow airports (such as UTair at SGC or S7 at OVB). The only example of a newly formed base that I know of is S7's hub in IKT. Aeroflot prefers a simpler (?) model - if they need a base somewhere they either buy out an existing airline (a practice they learned through Donavia and Nordavia to be painfully detrimental) or establish a subsidiary.
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