AT45, Amami Japan, 2020
AT45, Amami Japan, 2020
On 8 January 2020, an ATR 42-500 veered off the side of the runway at Amami after touchdown whilst attempting to complete a crosswind landing following a crosswind approach in potentially limiting conditions. It was concluded that directional control had been lost during touchdown because of sub optimal use of the combination of flight control inputs and power at and immediately after touchdown following an essentially stabilised visual approach. The aircraft manufacturer was prompted to make some changes of emphasis in normal operations guidance during the landing roll.
Description
On 8 January 2020, an ATR 42-500 (JA07JC) being operated by Japan Air Commuter on a scheduled domestic passenger VFR flight from Kikai to Amami as JC3830 touched down normally on the centreline of runway 03 at destination in day VMC in the presence of a significant gusting crosswind from the left. However, directional control was then lost and the aircraft veered off the left edge of the paved surface onto the adjacent grass before coming to a stop after travelling a further 110 metres. None of the 21 occupants were injured.
The accident aircraft in its final stopping position. [Reproduced from the Official Report]
Investigation
After prompt notification, the Japan Transport Safety Board (JTSB) began a Serious Incident Investigation later the same day. Recorded data from the FDR and CVR were downloaded and included useful information. Relevant meteorological data and recorded R/T communications between the flight and the Remote Tower location were also available.
It was noted that the 49 year-old Captain, who was acting as PF for the accident flight, had a total of 12,373 hours flying experience including 1,450 hours on type. The 44 year-old First Officer had a total of 7,125 hours flying experience including 738 hours on type.
What happened
The flight crew departed Kagoshima for the one hour flight to Amami just before 0730 local time. They then operated 10 minute VFR flights from Amami to Kikai and back to Amami with the runway excursion occurring after landing at Amami from Kikai. On takeoff from Kikai the aircraft climbed to 2000 feet and called Amami Radio for the latest weather report and was informed that the wind velocity was currently 320° at a mean speed of 28 knots and that the maximum recently observed instantaneous wind gust was 38 knots. On right base leg for Amami runway 03 a few minutes later, the wind was unchanged except that the maximum recently observed instantaneous wind gust had increased to 40 knots.
The Captain was aware that the applicable 30 knot crosswind landing limit was based on the reported mean wind velocity and of the AOM stipulation that provided an approach to land met the stabilised approach criteria at 1,000 feet agl and when passing 500 feet agl, the crosswind limit was only required to be strictly applied until 500 feet. Below that height, the pilots had discretion to judge that a safe landing could be achieved “with normal manoeuvring irrespective of the notified (AOM wind velocity maximum) value” subject to the requirements for a stabilised approach being “continuously satisfied”.
The AP was disconnected at approximately 1,400 feet, the flaps were set to 35°and a stabilised approach was set up with a VAPP of 105 KIAS. Speed variations were thereafter called out by the First Officer and corrective action taken.The Captain stated that he had considered a go-around but decided that he was and would continue to be able to maintain a stabilised approach. At 850 feet agl, Amami Radio transmitted the mean wind velocity as 310°/27 knots with the maximum recently observed instantaneous gust being still to 38 knots. A minor deviation to the left of the extended centreline occurred at about 300 feet agl but had been corrected by 250 feet agl and the runway threshold was crossed at approximately 50 feet agl with an approximate 4° bank to the left and a magnetic heading of approximately 023°.
The right rudder pedal was applied at approximately 30 feet agl and the elevators were moved in the nose-up direction at around 20 feet agl and when the left main landing gear touched down almost on the runway centreline 400 metres beyond the runway, the power levers were at flight idle, the rudder pedals were almost matched, the bank angle was approximately 2.6° to the left and the magnetic heading was approximately 029°. The other two gear legs touched down one second later. The normal hand over of the control column to the PM followed and although the First Officer stated that they had initially believed directional control was keeping the aircraft on the 45 metre-wide, 2000 metre-long runway, tyre marks showed that the aircraft left the paved surface to the left at approximately 680 metres past the runway threshold before stopping just over 100 metres further on.
A reconstruction of the flight path. [Reproduced from the Official Report]
It was noted that wind velocity at Amami was automatically measured every 6 seconds during the period around the time of the excursion using an anemoscope and an anemometer installed in the vicinity of Runway 03 touchdown area (approximately 330 metres past the threshold and approximately 105 metres west-northwest of the runway centreline). These readings all allowed an instantaneous crosswind component to be derived and all were comfortably within the 30 knot crosswind landing limit with that at the point of touchdown being only 18 knots with the maximum just before and just after touchdown being 25 knots.
Why it happened
It was considered that it was unsurprising that the approach was commenced in the prevailing wind velocity conditions since the crosswind components derived from all mean wind velocity figures passed to the flight by Amami until passing 850 feet agl were 30 knots or less - the AOM in flight limit based on the mean wind velocity being reported. It was noted that the brief deviation to the left of the extended centreline between 300 feet and 250 feet had presented some control issues but a rapid recovery to the centreline had been followed by touchdown of the left main gear just ahead of the right main gear and nose gear with the rudder almost neutral.
It was considered that this gear contact sequence at a time when the bank angle was also very slightly left wing down had probably initiated a deviation to the left in the absence of sufficient right wing down aileron input after the Captain’s de-crab rudder movement as he prioritised forward movement of the control column followed by selection of reverse pitch. A delay in right rudder input pending the transition from directional control by rudder to the use of nosewheel steering was also considered to have had significant consequences.
The Probable Cause of the Accident was recorded as “the delay in correcting the deviation to the left immediately after touchdown when landing in a crosswind from the left, which resulted in the aircraft running off the side of the runway and coming to a stop and being unable to move again under its own power”.
Safety Action taken as a result of the findings of the Investigation was noted as having included but not been limited to the following:
Japan Air Commuter:
- Made revisions to their AOM and Flight Technical Guide (FTG) in respect of landings performed when a gusting wind is present. The OM Supplement now stipulates that whether or not an approach in such condition shall be continued depends on the crosswind component during gusts not exceeding 1.5 times the maximum crosswind and satisfies the 30 knot limit in the AOM.
- Incorporated revisions to the ATR FCOM in respect of normal procedures in the landing roll into the AOM in particular by fully incorporating the FCOM guidance on ‘Operations in wind conditions’ and revised FTG content on takeoff and landing in crosswinds to ensure consistency.
- Conducted ground school and simulator training for all pilots to enhance knowledge and application of the ATR-recommended crosswind landing manoeuvre and provided additional ground school training to support stabilised approach operations.
ATR
- Reviewed the procedures for normal operation during the landing roll in order to revise FCOM by clarifying that braking is the primary means of deceleration after touchdown, that the power levers should be set to ground idle at the time the nose landing gear touches down and that reverse pitch should be used as required.
The Final Report was adopted by the JTSB on 25 February 2022 and then published simultaneously in both the definitive Japanese language version and in an English language translation on 24 March 2022. No Safety Recommendations were made.