Flight 1492 Pilot Accuses Sukhoi – Critical Design Flaw Remains Unsolved

  • May 21, 2020

May 5th 2019, Moscow. Regional flight Aeroflot 1492 had taken off, bound to the city of Murmansk. It was operated by a regional aircraft of the controversial Russian-designed Sukhoi Superjet 100 type.

In just a few minutes after takeoff, the aircraft got struck by lightning – a common occurrence, which is typically a non-event in modern aviation, thanks to the 21st century engineering and safety regulations. However, the aftermath was anything but common.

The aircraft experienced an immediate radio failure and lost its autopilot system, switching the flight control mode to DIRECT – a degraded, more challenging mode of operation, with auxiliary systems unavailable, and the aircraft’s control panels responding directly to flight stick input.

The Captain made the decision to immediately conduct an emergency landing at the airport of origin. Upon making contact with the ground, the plane’s landing gear collapsed and punctured fuel tanks, which were at full capacity. As a result, fire broken out, and the aircraft spin out of control.

41 people out of 78 on board have perished from fire, which fully consumed the bottom half of the plane. Russian prosecutors have charged the flight Captain Denis Evdokimov as the sole culprit in the criminal investigation that ensued. However, he denies the accusation, and states that the aircraft was inoperable by the moment they’d touch down.

D. Evdokimov is currently under Restricted Residence (a preventive measure in Russian Criminal Code, which prevents a suspect from leaving their settlement of residence) and had not spoken with the press for over a year.

Denis Evdokimov

The Russian news platform Lenta.Ru posted his first interview after the tragedy in Russian. Vatnik Today is providing a translation below.

-Let’s talk about that day’s events. What were the weather conditions? Were they suitable for flight? Whose call was it to take off?

Evdokimov: The weather wasn’t anything out of ordinary. The forecast we received met all conditions for a take off. While stationary on runway, I’ve taken the forecast into account, and observed the airspace in the takeoff direction to confirm no dangerous weather conditions, which I’ve noted to my First Officer (co-pilot).

At any rate, the decision to take-off, keep on course, or land is always made by the Captain. Hence I, as the Captain on that flight, have decided to take off and head towards our destination.

-The plane was struck by lightning, and the control mode was switched to DIRECT. How ordinary is that?

Evdokimov: Lightning strikes are not uncommon, but usually they won’t result in malfunctions. On this flight, however, our most important system went offline – the aircraft control system. The Superjet’s flight control is fully Fly-By-Wire (fully electric), and there is no reserve mechanical system for control surfaces in place.

Neither the investigation authorities, nor the Interstate Aviation Committee were interested in the way the atmospheric electricity had affected the plane – there’s not a word on that in the criminal case materials, except for passenger and crew testimonies.

I believe that omission of this critical fact was made to avoid reputational risks for the Superjet’s manufacturer.

-Did you have any prior experience with operating SSJ-100 in DIRECT mode? Was it part of your training?

Evdokimov: The DIRECT mode was practiced as part of the aircraft type transition training, by using flight simulation. This is in compliance with the state regulator’s program. It does not mandate training on a live aircraft.

-Was the plane’s operation different in real life compared to the flight simulator?

Evdokimov: Usually, practice flights in this mode using flight simulators don’t cause any difficulties. On the actual May 5th flight, the DIRECT control was severely different to simulations.

-What made you turn around and return to the airport, instead of continuing your flight to Murmansk?

Evdokimov: Further flight towards Murmansk was impossible, as DIRECT mode allows flying only on low altitudes, which results in higher fuel consumption. We did not have enough fuel on board. Multiple malfunctions on cockpit displays have also made the decision to continue to the airport of destination impossible, because we could not accurately determine the plane’s condition in-flight.

-Why did you choose not to circle around the airport to burn fuel, and to land with full tanks instead? Was this not potentially dangerous?

Evdokimov: This decision was made out of fear of potential total loss of control over the aircraft. As I said before, atmospheric electricity does not affect flight control, but it happened in our case.

If this was a discharge with power higher than the certified values, continued flight may have resulted in a cascade of further malfunctions, which would’ve rendered the aircraft completely uncontrollable.

-During landing, you were recorded saying “What’s this? 200 feet, plus-minus”. What does this mean?

Evdokimov: I’ve noted difficulties maintaining level flight.

-An Investigative Committee of Russia official claims that the plane responded to pilot’s input adequately. Your attorney, however, said that the aircraft was getting tossed sideways. So what happened?

Evdokimov: Yes, but he didn’t mention the fact that on the day I was charged, there wasn’t any decoded flight parameters data in case materials, or any detailed analysis of [pilot’s] actions, and the plane’s responses to control input.

The fact that the investigation had appended only the cockpit voice recorder’s contents to case materials is particularly noteworthy, as it does not provide full flight data. Yet the Interstate Aviation Committee does use information from the flight data recorder, which contains full flight parameters, including system malfunctions.

During the emergency landing, the aircraft response to input became inverted, meaning that pulling the stick pulled the nose down, not up – and vice versa. According to flight recorder data, the input lag was roughly one second, which is critical on low altitudes.

-What was the exact moment you’ve noted the loss of control?

Evdokimov: Severe deviations and growing input lag have fully manifested at touchdown.

-At 1528 hours, a system alert went off – “Go around, windshear ahead!”, but the crew did not go around. Why?

Evdokimov: This alert does not mandate going around, it only informs the pilot of windshear probability. No signs of the windshear were observed at that moment.

-The Interstate Aviation Committee’s preliminary report mentions you making sweeping movements with the control stick, pulling and pushing it nearly to the limit. Why?

Evdokimov: When controling the aircraft, the pilot does not look at the stick. When moving it, they look either at the horizon, or at the runway. The range of movement it depends on the plane’s response. A pilot pulls the stick – the plane doesn’t move, so they continue to pull until the necessary response.

Next, the course is changed sharply, which is immediately compensated by the pilot to prevent critical flight parameters.

-Have you or your colleagues encountered any difficulties with controling the Sukhoi Superjet prior to the May 5th accident?

Evdokimov: I had no problems flying and landing the plane manually before, but on this particular flight, the control mode switched to DIRECT due to a reason not documented by the manufacturer, hence aircraft behavior might not have been in order.

My colleagues have noted certain instability of the SSJ-100 in this flight mode, which is actually mentioned in the Interstate Aviation Committee’s report with a note that these circumstances will be further investigated – which has still not happened by today.

It’s necessary to investigate what exactly had happened with flight controls after lightning strike. But nobody studied the wreckage, it’s not even present as evidence in the criminal case materials. The lack of a proper research leaves the cause of the accident unknown, so it might happen again.

-The plane bounced from the ground upon touchdown. Why did you not go around as per flight instructions require?

Evdokimov: Going around was impossible due to the aircraft’s improper response to flight input.

Setting engine throttle to Take Off position provides increments of the pitching moment, and with inverted response to control input, this could’ve resulted in a nose dive, or crash on the tail.

I am sure that both of these outcomes would result in death of everyone onboard…

-The plane’s landing gear has collapsed and damaged the plane’s fuel tanks, resulting in fuel leak and fire. Standards outlined in the Airworthiness Certificates provide that any destruction of landing gear shall not result in damage to fuel tanks.

However, an official of the Ministry of Industry and Trade of the Russian Federation has said that the gears are designed to collapse safely only upon one touchdown, and they are not designed to take three hits. How many hits do you believe they are supposed and could take?

Evdokimov: I find the Ministry’s safe collapse theory far-fetched. It’s all outlined in the Airworthiness Certificate, and no extra clarification is necessary.

Had the landing gear’s design been in compliance with Airworthiness provisions, they would’ve broken down safely from the first overload, and no further collapse would have happened.

I’ll also note that there were no test flights that would include landing with weight above the recommended maximum landing mass, although the manufacturer did allow landing with full take-off mass.

-Were there any prior incidents involving Sukhoi Superjet’s landing gear?

Evdokimov: There were similar cases, they’re all documented online:

  • During test flight at Paris-Le Bourget in 2008
  • During test flight in Zhukovsky in 2018
  • During landing in Yakutsk in 2018

In all of these incidents, landing gear damaged the fuel tanks and caused fuel leaks. And it’s only on a fluke that there were no fatalities. The issue keeps manifesting itself, and the Ministry refuses to see it.

-What do you think had resulted in people dying?

Evdokimov: [The plane’s] nonconformity with the standards of airworthiness. Had the manufacturer implemented the necessary engineering changes, these accidents would not repeat, the flight safety would have been ensured, and risks would come down to a minimum.

I’d like to express my deepest condolences to people who had lost their loved ones, and those who were injured in the accident. I am sincerely sorry and beg your apology for having become part of these events.

I knew that the lives of passengers and crew members depended on my actions, and I’ve done all I could.

There hasn’t been a single day, or a minute, that I wouldn’t have thought about those who did not disembark alive and unharmed.

I will not back down and keep pressing for a proper investigation to seek out the true reasons that have led to these tragic events, for lives and well-being of passengers who continue to fly on the Sukhoi Superjet depend on it.

[source – Lenta.Ru]

Translated by Vatnik.Today