AIS JS32 at Muenster on Oct 8th 2019, takeoff with gust locks engaged, rejected takeoff, runway excursion
Last Update: February 8, 2021 / 17:38:24 GMT/Zulu time
On Dec 27th 2019 Germany'S BFU reported in their October 2019 bulletin that another aircraft was waiting at the hold short line when the JS32 crossed the taxiway between runway edge and hold short line at 119 KIAS.
The first officer had not flown on type for more than 3 months and felt being behind the aircraft already during taxiing the aircraft via D and A to runway 25. While approaching the hold short line the crew contacted tower and received takeoff clearance. The crew subsequently worked the Line Up checklist with the first officer reading the points of the checklist. The first officer however overlooked the point "Flight Controls" in that checklist, the flight controls thus were not checked for free movement by either pilot. On a further point "Stall Protection" the first officer did not find the relevant switches, the captain found them "not so important", hence the stall protections were't activated. 92 seconds after being cleared for takeoff the crew commenced takeoff, the captain noticed, while steering the aircraft via nose wheel steering, that stall protections and landing lights were not switched on. Upon reaching 70 knots the captain handed controls to the first officer. The captain later reported that the aircraft continued straight for a couple of seconds before veering right.
Following the rejected takeoff a runway inspection found damage to runway edge light, a sign (for the glider area). The aircraft received damage to a right propeller blade, the left main tyre and the right luggage hold, fuel leaked at the joints of left and right main gear struts to the wings.
The captain reported the gust lock lever was in the upper position, which locks the flight controls.
The BFU reported with the gust lock lever in the locked position, it should have been impossible to advance the thrust levers to above flight idle. However, the thrust levers could be freely moved even with the gust lock lever in the locked position. The fork end of a driving rod, that should have locked the thrust levers, was found bent by 45 degrees, so that it could no longer block the thrust levers. That mechanism had been last checked on Mar 19th 2019 with no anomaly detected.
There had been 4 similiar occurrences where the rod had bent and was no longer able to prevent the thrust levers to be moved above flight idle with the gust lock lever in the locked position. An enforced version of the control rod was designed in 1992 and highly recommended to be used. The recommendation however had not been implemented on the occurrence aircraft.
On Feb 8th 2021 the BFU released their final report concluding the probable causes of the serious incident were:
Veering off the runway during take-off run occurred due to the engaged Gust Lock system which locked the control surfaces and resulted in the pilots loosing temporary control of the aircraft.
- Insufficient supervision, support and monitoring of the Line Training Instructor
- Inexperience of the young co-pilot and long time gap between type rating and the first commercial scheduled flight
- Insufficient Crew Resource Management of the flight crew
- Pressure of time created by the crew between engine start-up and take-off
- Non-stringent application and erroneous completion of the checklists
- Checklist items, procedures and choice of wording in the checklists of the operator which did not completely correspond with the ones of the aircraft manufacturer
A mechanically deficiency in the Gust Lock system, which allowed the engine power of both engines to be increased simultaneously, was also a contributing factor.
The BFU analysed:
The serious incident, take-off run with engaged Gust Lock system during commercial scheduled services, and veering off the runway, occurred involving a flight crew who was very different in regard to age, years of professional experience, flying and type experience.
The 63-year-old PIC has to be viewed as very experienced in regard to his total flying experience and the number of years working in aviation. The major part of his flying experience he acquired as flight instructor during training flights in flight schools. He had been flying the type concerned since 2018. The operator deployed him as Line Training Instructor, i.e. as someone, who is training, instructing, and monitoring new pilots to adhere to the company’s procedures. The BFU is of the opinion that especially during Line Training it should be self-evident that checklists are completed item by item and that the required time for all actions is taken. The exemplary function during training and especially preparation of scheduled services should be clear to everyone at all times. The BFU is of the opinion that for a young or new pilot of a company good practices of an experienced PIC or Line Training Instructor are formative and important for the safety culture and flight safety.
Compared with the PIC the 26-year-old co-pilot was very inexperienced. His realtime-flying experience on type was less than one hour. The day of the occurrence was his first day of work for the operator, in commercial air operations and after acquiring his type rating. The BFU is of the opinion that due to the time gap between finishing his type rating and the first flight, intensive attention of the Line Training Instructor would have been required to prevent asking too much of the co-pilot and compromising Crew Resource Management. The BFU is of the opinion that the inexperience and the large age and experience gradient within the flight crew made an equal flight-safety-improving CRM difficult.
At the day of the occurrence, the crew met sufficiently early to have enough time for the first Line Training flight and to ensure a safe conduct of flight. The BFU is of the opinion that the slot arrangement and the relatively late engine start-up in spite of early clearance at their own discretion 20 minutes prior to the intended slot resulted in unnecessary haste. Within 10 minutes engine start-up occurred, taxi instructions and clearances were received, taxiing to the runway and line-up were conducted. During the same time Before Start, Start Up, After Start, Taxi and Line up checklists should have been completed. Especially during the first flight of the Line Training sufficient time would have been required. The CVR recording showed that during Line up the checklist items Flight Controls … CHECKED and Stall Protection … TESTED & ON were not completed. Therefore, the engaged Gust Lock system was not detected during Line-up.
The meteorological conditions did not limit the intended flight. Neither visibilities, clouds nor the prevailing wind should have resulted in distraction during the preparation, taxiing or take off run.
There was little traffic at the airport. The general procedures and the taxi procedures at the airport were clear and not demanding or distracting, as it could be at, for example, large airports with confusing procedures and designations, several run- and taxiways and high traffic volume.
The serious incident occurred during the take-off run for the third flight of the aircraft of the day. The BFU does not have any information of technical limitations which would have resulted in distraction or impairment of the flight crew to complete all checklist items and adhere to procedures.
The aircraft type has been operated in commercial air transport for decades, especially for short-distance flights in feeder operations. As a result, compared with the operating time, this type of flight creates a high number of flight cycles. The aircraft involved also had a higher number of flight cycles than operating time. In comparison to some other aircraft the design of the Gust Lock system to lock the flight controls during parking of this aircraft type was complex. The Gust Lock lever was installed in a slightly unfavourable position in the cockpit, i.e. a location easily overlooked by pilots. According to the manufacturer’s check items of checklists for engine start-up, taxiing and last checks prior to take-off (POWER levers … Full and free, GUST LOCK lever … Confirm in OUT position, STALL PROTECTION system … Tested ON, Stall Protection … Tested & ON, Flying controls … Full and free) it should have been ensured that a flight crew realises in time prior to take-off run that the Gust Lock system was not disengaged. In addition, as a last technical barrier it should not have been possible to increase engine power with both power levers simultaneously. The BFU is of the opinion that it is probable that other flight crew did not check the proper function of the Gust Lock system during pre-flight preparation or cockpit checks and that the technical deficiency had existed for some time.
Procedures and checklists of the operator of the aircraft involved deviated in some items and choice of wording from the published procedures and checklists of the aircraft manufacturer. The checklist item GUST LOCK … RELEASE / FULLY DOWN was missing in the Taxi and Line-up check. The checklist item FLYING CONTROLS … FULL and FREE was shortened to Flight Controls … CHECKED. Checking the full and free movement of the flight controls was moved from the Taxi check to the Lineup check.
The BFU is of the opinion that the missing checklist items regarding the Gust Lock system and the choice of wording for checking the flight controls is not acceptable. Checking the flight controls should occur prior to Line-up as it was intended by the manufacturer, and as it is commonly practised. In general, at airports there is usually no time for time-consuming Line-up checks on the runway. In spite of the deviations, the correct completion of all checklist items of the operator should have ensured that the Gust Lock system was disengaged and the full movement of flight controls checked.
The current and similar occurrences in the past involving this aircraft type show that several flight crews forgot to disengage the Gust Lock system and/or did not detect an incomplete unlocking due to insufficient check of flying controls prior to the takeoff run, and that several control rods for blocking the power levels were bent. The BFU is of the opinion that EASA should change the Highly Recommended Service Bulletin (SB) 27JM-535 of the manufacturer to a mandatory Airworthiness Directive to ensure that the power levers of all aircraft of this type are locked if the Gust Lock system is engaged.
Incidents during take-off run due to engaged Gust Lock systems occur around the world time and again. This is surprising since the problem has been known for decades. The BFU can only support the findings of the multiple investigations of forgotten Gust Lock systems and refer to the importance of extensive flying training, compliance with and adherence to procedures and checklists and mutual monitoring as part of flight-safety-improving CRM. The maintenance personnel should understand the importance of a fully functional Gust Lock system, which does not allow take-off in the engaged position, and check the proper function regularly.
Ultimately, only a complete check of flight controls prior to a take-off run can ensure that all flight controls are full and free.
Aircraft Registration Data
This article is published under license from Avherald.com. © of text by Avherald.com.
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