E190, manoeuvring, northeast of Lisbon Portugal 2018
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|On 11 November 2018, an Embraer 190-100LR which had just taken off on a non-revenue positioning flight after a ‘C’ Check became extremely difficult to control in day IMC despite the complete absence of any flight control warnings. Eventually, after reverting to Direct Law, the crew were able to obtain some control and after exiting IMC were guided to Beja where, on the third attempt after almost two hours airborne, a landing was successful. The Investigation is not yet complete but has concluded the cause was gross maintenance error involving release from check with the aileron system incorrectly configured.|
|Actual or Potential
|Airworthiness, Human Factors, Loss of Control|
|Aircraft||EMBRAER ERJ 190-100|
|Type of Flight||Public Transport (Non Revenue)|
|Intended Destination||Minsk International Airport|
|Take off Commenced||Yes|
|Tag(s)||Approach not stabilised,|
Military Fast Jet Formation,
|Tag(s)||Procedural non compliance|
|Tag(s)||Significant Systems or Systems Control Failure,|
Temporary Control Loss
|Contributor(s)||Maintenance Error (valid guidance available),|
Inadequate Maintenance Inspection,
Dispatch of Unserviceable Aircraft
|Damage or injury||Yes|
|Causal Factor Group(s)|
On 11 November 2018, an Embraer 190-100LR (P4-KCJ) being operated by Air Astana on a non-revenue international positioning flight from Alverca to Almaty, Kazakhstan via a technical stop at Minsk, Belarus as KZR 1388 became extremely difficult to control almost immediately after takeoff in day IMC. After declaring an emergency, the crew were eventually able to recover partially normal control and after being guided to Beja, a third attempt to land was successful after almost two hours airborne. One of the three company engineers on board as passengers sustained minor injuries and there was substantial damage to the aircraft.
The event was notified to the Portuguese Air and Rail Accident Investigation Agency (GPIAAF) whilst it was still in progress and investigators then travelled to Beja and commenced a detailed examination of the aircraft. The FDR and CVR were both removed from the aircraft but useful data could only be downloaded from the FDR as relevant CVR data had been overwritten.
The accident flight was the first since the completion of a ‘C’ Check on the aircraft at Oficinas Gerais de Material Aeronáutico (OGMA), an MRO specialising in Embraer maintenance located near Lisbon. It was established that “immediately after takeoff into adverse meteorological conditions”, the flight crew had concluded that the aircraft was not responding normally to pilot inputs intended to control the aircraft flight path. Abnormal aircraft attitudes began to be experienced whilst still in contact with the TWR at Alverca and an emergency was declared.
Despite continuous Alerts for abnormal flight attitudes, no flight control system warnings or alerts were presented and it was found that it was not possible to engage the AP. Whilst the crew continued with flight control inputs in an attempt to counter unwanted movements, “without any understanding of the cause of the aircraft instability” it was difficult to remain in effective control and it was only with considerable effort that they were “able to minimise the oscillatory movements, with high structural loads involved during some recovery manoeuvres and using crossed (flight control) commands”.
The critical situation did not improve and FDR data showed that the erratic trajectory of the aircraft had created “intense G-forces” as well as multiple instances of complete losses of control for brief intervals - see the example illustrated below which was one of many upset instances during the flight. In view of the difficulty in controlling the aircraft, ATC were requested several times to provide radar headings which would take the aircraft towards the sea to carry out a ditching.
However, before this occurred, the crew decided that, despite the absence of any warnings for system failures, they would activate the flight control system Direct Mode (elevators, rudder and roll spoilers) which removes the Flight Control Module (FCM) from flight surface command so that they are then controlled directly in proportion with the control column and rudder pedal inputs. After this, although “the situation improved considerably”, it did not restore normal operation and achieving roll control remained difficult, so having realised that aileron control was now the main problem, roll commands were thereafter minimised.
Having gained some control of their situation, the crew were assisted by ATC to fly inland to the east to seek a suitable airport with better weather conditions for an emergency landing. Once in VMC, the aircraft was joined by two Portuguese Air Force F-16s which helped guide the aircraft to the joint military/civil use airport at Beja which had, in the meantime, been selected as the best emergency landing option.
On arrival at Beja, two visual approaches which were discontinued when they became unstable were followed by a third attempt to land on the 3450 metre-long main runway, 19R, which turned into a successful landing on the slightly shorter (2951 metre long) parallel runway 19L when it proved impossible to prevent the aircraft drifting off the 19R extended centreline on short final. It was noted that upon arriving at the allocated parking position, “all those on board were physically and emotionally shaken”. The aircraft was found to have sustained substantial structural damage to both wings, the fuselage and all flight control surfaces.
It was noted that roll control on the aircraft type involved is achieved either by input to the control columns in manual flight or, when the AP is engaged by commands it generates with in both cases aileron movement being assisted by roll spoilers. The Power Control Units (PCU) which move the aileron surfaces are mechanically controlled and hydraulically powered.
A detailed examination of the aircraft flight controls found that the aileron control cable system had been incorrectly installed inverted in both wings.
It was found that action taken during implementation of a modification detailed in SB 190-57-0038 during the ‘C’ Check had replaced a pulley system with a new cable support which had obviated the need for cable routing and separation around rib 21. This was considered to have “made it harder to understand the maintenance instructions” which was taken as an indication that there may be “opportunities for improvement in the interpretation of the maintenance procedures involved”.
It was also found that a message ‘FLT CTRL NO DISPATCH’ had been generated during the maintenance work and had led to troubleshooting activities supported by the aircraft manufacturer which lasted 11 days but had not identified the ailerons' cables reversal and had not been correlated to the "FLT CTRL NO DISPATCH" message.
It was noted that deviations from internal procedures at the MRO had been discovered which had led to the cable routing error not being detected in the various safety barriers implemented by safety regulators, the aeronautical maintenance industry in general and within OGMA in particular.
Possible Safety Action
The Investigation findings communicated so far have provided Embraer with sufficient relevant factual data to allow the manufacturer, should it consider it necessary, to:
- Formally raise aircraft operators’ and MROs’ awareness of possible maintenance error following significant disturbance to flight control systems, including but not limited to revising the Embraer release of Field Report: ERFR GFS 018-18.
- Provide guidance material in line with these findings to aircraft operators and MROs which will help them positively identify errors after maintenance has been carried out on aircraft primary flight aircraft control systems.
Reporting the Investigation
After issuing an initial Information Notice about the accident on 13 November 2018, a further Aircraft Accident Investigation Notice was issued on 31 May 2019. This detailed the factual and causal findings as established at that point but noted that the Investigation will continue to further examine the design and functioning of the aircraft, the crew procedures and the human factors aspects raised and will focus particularly on maintenance procedures and related aircraft technical documentation and the human and organisational factors involved at the Part 145 MRO which carried out the ‘C’ Check.