The aircraft came to a stop around 600 metres from the end of the runway
A Jet2 Boeing 737-800 experienced a significant loss of airspeed and directional control due to windshear during a take-off in gusty conditions at East Midlands Airport in February this year, a report by the Air Accidents Investigation Branch (AAIB) has found
The crew of the narrowbody elected to reject a take-off after reaching V1 leading the aircraft to come to a stop about 600m from the end of the runway.
The aircraft, G-DRTN (c/n 32735) is a nearly 19-year-old example that has been in the airline’s fleet since September 28, 2018.
Flight history
On the day of the incident, February 9, East Midlands was experiencing strong, gusty winds and squalls resulting from Storm Ciara. The forecast indicated wind was 32kts gusting 45kts.
The runway surface was wet and 25kt crosswind limit was in place for departure. The commander initially decided he would conduct the take-off but changed his mind after the co-pilot informed him that as a senior first officer, he was permitted by the airline to use the same weather limits as the commander.
This transfer of responsibility allowed the captain to focus on anticipated difficulties they would face in loading catering and persons of reduced mobility (PRM) caused by the airport stopping the use of high lift vehicles because of the wind.
As expected, the commander spent a considerable amount of time dealing with the airport ground staff and operator’s headquarters as he tried to resolve several issues relating to the strong winds.
The scheduled rotation was due to link East Midlands with Tenerife/South in Spain.
The take-off
During the cockpit brief, the crew refreshed the actions for the windshear escape manoeuvre and a rejected take-off. The calculated performance figures for the departure were V1 134kts, VR 149kts, V RMAX 158kts and V2 156kts.
The aircraft had fuel in excess of what was required so the crew decided to start and taxi to the runway and wait for a suitable opportunity to take-off. The pilots had calculated the maximum wind speed and direction for a runway 27 departure, that would give a crosswind component of 25kts, which was 210⁰ at 29kts. This was passed to ATC.
As they approached the runway, the flight was cleared for take-off and passed a wind of 220⁰ at 32kts. The pilots confirmed this was acceptable and lined up without stopping and selected take-off power.
At approximately 120 kt, the commander recalled a transitory reduction in airspeed of between 10 and 15kts. He called this to the co-pilot but, as the acceleration resumed, decided to continue. The commander stated that approaching V1 (134 kt) the aircraft deviated dramatically from the centreline to the right. He estimated the deviation was between 20° and 30° of heading. The commander saw a large downtrend on his airspeed indication and felt that the co-pilot’s attempts to control the heading were ineffective. He stated to the investigation, “as PM, my instant snapshot was that indicated airspeed was reducing and we were below V1, so I called Stop.” During this sequence of events, both pilots recalled hearing the automated V1 callout.
The commander took control in accordance with Standard Operating Procedures (SOP), the RTO actions were carried out and the aircraft stopped on the runway centreline between M and H taxiways, with approximately 600m remaining.
The report
During the aircraft’s take-off roll, there was a 13 kt reduction in airspeed prior to V1. The commander noted the reduction and informed the co-pilot. It was short-lived and as the acceleration in airspeed resumed the commander decided to continue.
At this stage, windshear is not one of the manufacturer’s RTO criteria and neither predictive nor reactive windshear warnings or cautions would be expected.
As the aircraft passed V1 the automated callout sounded, but immediately thereafter the airspeed decayed, the aircraft yawed rapidly right away from the centreline (approximately 8 degrees) and there was a noticeable change in the lateral g.
The commander was concerned the aircraft could exit the runway and considered the situation to be unsafe. He had seen the reduced airspeed with the associated downward trend indication, which occurred approximately five seconds before V1, and called “Stop” to reject the take-off. The AAIB say the RTO actions were promptly and correctly carried out along with rapid control inputs to return the aircraft to the centreline.
The AAIB’s accident analysis focused heavily on the crew’s decision to stop once beyond V1. The report quoted a section from the non-normal manoeuvres segment in the aircraft quick reference handbook (QRH) which concentrated on what to do if windshear is encountered before V1.
Responding to its QRH entry, Boeing said: “The … text … does not imply that stopping could be initiated after V1. On the contrary, a windshear during take-off roll can result in groundspeed greater than indicated airspeed due to the tailwind effect of the windshear. Because of the higher ground speed, performance data for stopping on a field length limited runway (a short runway) may not be accurate, resulting in a runway excursion even though the airspeed indicates V1 or less at the start of the RTO.
“The commander has the sole responsibility for the decision to reject or continue a take-off in a windshear emergency. The commander must determine the safest course of action based on airspeed, airspeed trend, runway remaining, braking capability, and other indications of airplane performance,” it added.
Conclusion
In conclusion, the AAIB report stated that the commander had a high workload managing the departure and to give himself time, decided that the take-off should be flown by the co-pilot.
In very gusty conditions, the aircraft encountered windshear near V1 which caused a 13kt reduction in airspeed. The strength of the crosswind also caused the aircraft to veer right.
Concerned that the jet might leave the runway, and considering the situation to be unsafe, the commander initiated an RTO five seconds after V1. Investigators noted that the airline’s standard operating procedure is to continue a take-off when V1 has been reached because as the manufacturer commented, successful outcomes are more likely than when a take-off is rejected.
As a result of the high-speed RTO, the number four wheel and brake unit suffered heat damage from the full braking action. The aircraft returned to its stand safely and passengers subsequently disembarked.
An engineering investigation led to the managed brake unit being replaced, as well as all wheels and tyres in accordance with the operator’s maintenance manual.
