Severe weather conditions blamed for Jet2 Boeing 737 runway incursion
A Boeing 737 aircraft belonging to Jet2, a British low-cost carrier, experienced a serious runway incursion due to very gusty weather conditions.
On February 9, 2020, a Jet2 Boeing 737-800, registered as G-DRTN, was scheduled to complete a regular flight from East Midlands, the UK to Tenerife, Spain when the Commander decided to abort the takeoff after the aircraft had already reached the recommended speed limit. As the initial report showed, the incident occurred when the aircraft was accelerating for takeoff from East Midlands Airport (EMA) in gusty weather conditions while carrying 193 passengers and 6 crew members onboard.
Thorny weather was the key factor
On December 10, 2020, the Air Accidents Investigation Branch (AAIB) of the United Kingdom released a bulletin regarding the investigation of the incident. The AAIB concluded that on the day of the incident, as a result of Storm Ciara, the weather conditions at EMA airport presented strong gusts of wind. As the weather forecast indicated, the speed of the wind reached 32 knots (59 km/h) with gusts of 45 knots (83 km/h). During the crew briefing, the Commander of the aircraft initially decided that he would take off despite the thorny weather conditions.
As the surface of the runway at EMA airport was wet, the plane was limited to a 25 knot (46 km/h) crosswind component for a takeoff. Following further discussion, the First Officer informed the Commander that the guidance of the airline allowed him to use the same climate limits as the Commander. Taking into account the weather conditions, the airport decided to stop using high-lift vehicles, which are used to help People with Reduced Mobility (PRM) to board the aircraft. In response, the Commander anticipated that there would be many difficulties that would consume his attention in preparation for departure and decided to delegate the preparation process for takeoff to the First Officer in order to be able to focus on other matters.
During the cabin briefing, the flight crew also discussed the possible actions for the Shear Wind Escape Maneuver (Windshear) and a Rejected Takeoff (RTO) performance in case of various wind stages. While the aircraft was refueled more than planned, the flight crew decided to taxi to the end of the runway and wait for clearance for takeoff. Regarding the relatively stable wind direction, the flight crew counted that the maximum wind speed and the direction, which was 210⁰ to 29 knots, would give a 25 knots side wind component.
As the aircraft approached the waiting point for Runway 27, the flight crew received clearance for takeoff. Meanwhile, the plane experienced a wind of 220⁰ to 32 knots that was at the counted limit and the flight crew applied the takeoff thrust. Then, at 120 knots (222 km/h), after the Commander noticed a transient decrease in airspeed between 10 and 15 knots, he warned the First Officer. When the aircraft accelerated again, the Commander decided to continue the approach.
Flight crew forced to complete the rejected takeoff
The investigation found out that during the approach V1 with a speed reaching 134 knots (248 km/h) the aircraft drifted dramatically from the central line to the right. The commander estimated that the deviation reached between 20 ° and 30 ° heading. After noticing a major downward trend in the airspeed indicator, the Commander decided that the First Officer’s attempts to control the course were ineffective. Following Jet2's Standard Operating Procedures (SOP), the Commander took control of the aircraft and performed the takeoff rejection (RTO).
After the RTO, the plane stopped in the center of the runway between taxi lanes M and H, with approximately 600 meters to go. Meanwhile, the Commander made a public announcement to alert the cabin crew. Then the flight crew informed the Air Traffic Control (ATC) about the decision to clear the runway while suggesting ATC to inspect the runway as the Commander was concerned that the plane could have hit sidelights of the runway.
As soon as ATC granted permission, the flight crew decided to return to the yard where the aircraft was shut down normally. An engineering investigation showed that during the incident the aircraft suffered fourth wheel and brake unit damage. As noticed in the AAIB bulletin, the damaged brake unit was replaced as well as all wheels and tires.
The Quick Access Recorder (QAR) registered that almost immediately after the moment when the airspeed dropped from 142 to 129 knots, the aircraft changed its course to the right. The AAIB clarified that between the V1 and the beginning of RTO, the plane turned to the right at 8 °. Once the RTO was started, the aircraft quickly turned left about 14 ° before returning to the centerline of the runway. Around the beginning of the RTO, there were substantial changes in lateral g-force, proportional to the rapid changes in direction.
The human factor
The Boeing 737 G-DRTN involved in the incident was equipped with a preventive wind detection system, which should warn the flight crew by an audible alert in the cockpit in case the aircraft is below 2,300 feet in altitude. However, the flight crew did not receive any predictive wind warning or warning during takeoff.
The AAIB analyzed that the weather conditions during the incident were severe and the aircraft was being operated to the limits of Jet2’s documentation. Regarding the guidance of Jet2, before deciding who should operate the aircraft, the Commander must take wind, pilot experience, track width, and surface conditions into account. The AAIB noticed that the First Officer had three times as many hours of work as the Commander and was more familiar with the airport. This means that the First Officer was also allowed to operate within the same limits as the Commander.
In addition, the AAIB noticed that after the airspeed decreased while the aircraft was passing V1, there was a noticeable change in lateral g-force and the Commander was concerned that the plane might leave the runway. The authority explained that the reduction in the wind during the incident changed the ratio of the airspeed and traveled distance along the runway in an unpredictable way. In this case, in addition to the wind, the Commander noticed the aircraft moving away from the centerline immediately after V1.
The AAIB concluded that the Commander of the G-DRTN, “had a great deal of work managing the takeoff and, to give himself time, decided that the copilot should take off”, read in the authority’s bulletin. In addition, the very strong wind was the main reason for the reduction of 13 knots in the airspeed while the crosswind during the takeoff made the plane deviate to the right.
The possibility that the aircraft might leave the runway forced the Commander to start RTO immediately after the V1 despite that the standard procedures (SOP) oblige the flight crew to continue the takeoff when V1 is reached. In this case, the aircraft stopped on the runway with 600 meters of the runway remaining.
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