Runway excursion and nose gear failure on a Robin DR400-140B at Granville Mont-Saint-Michel (F-GCIM)

Flight and accident sequence On 10 October 2013 at about 13:00 local time, a Robin DR400-140B registered F-GCIM, operated by a club, departed the uncontrolled aerodrome of Granville Mont-Saint-Michel for Avranches Le Val-Saint-Père, 15 nautical miles to the south. The pilot, accompanied by one passenger, performed a touch-and-go on runway 04 at Avranches and returned to Granville. On approach to runway 07, a paved runway 960 m by 30 m, the pilot observed wind from 350 degrees at 15 kt, the same as at departure. During landing, when the nose wheel touched the runway, the aircraft turned rapidly to the left and left the runway. At low speed, the nose gear became stuck in a rabbit burrow and the aircraft stopped. The nose gear leg was broken and one of the two propeller blades was bent. ## Wreck and aircraft information Ground traces indicated that the main wheels touched down 70 m from the threshold of runway 07. The aircraft came to rest after a total ground roll of about 325 m, of which 228 m were on the runway. About 150 m after main-wheel touchdown, the aircraft’s path had gradually deviated from the runway centreline until it formed an angle of about 30 degrees with it. The flaps were in the landing position. For Robin tricycle-gear aircraft, the nose wheel locks automatically in the aircraft’s longitudinal axis once its shock absorber is no longer compressed after takeoff. This system prevents movement of the wheel and its fairing and limits aerodynamic effects from rudder inputs. On landing, the wheel is unlocked by compression of its shock absorber. Below a certain speed, the rudder is no longer effective and the nose gear provides directional control. The braking system of F-GCIM is operated by a control on the central console, between the fuel selector and the instrument panel. It brakes the two main wheels symmetrically. Asymmetric braking is also possible when one rudder pedal is at its stop. For crosswind landings, the flight manual does not specify a particular flap setting. However, a flight manual update valid for all DR400 aircraft, published in February 1988 for the DR400-140B, recommends using only one notch of flaps for crosswind landings. The demonstrated crosswind limit is 22 kt. At maximum landing mass (1,000 kg), at sea level and 15 °C, the landing roll on a paved runway with moderate braking is 220 m. ## Pilot experience and testimony The pilot held a PPL(A) licence since July 2013 and had 113 flight hours, including 22 hours as pilot-in-command and 7 hours in the three months before the accident. He had about 8 hours on the DR400-140B, including 6 hours 20 minutes as pilot-in-command, all in the three months before the accident. He had completed most of his training and flights on Robin DR400-120 aircraft, on which braking is obtained by pressing the rudder pedals. The pilot stated that during flight preparation he noted that the northerly wind would cause crosswind takeoffs and landings. He estimated the wind between 10 and 15 kt. He reported no turbulence during the flight and said the wind, in both intensity and direction, was identical at Avranches and Granville. He described a sudden but steady veer to the left when the nose gear touched down. Accustomed to the DR400-120, he first tried to brake by pressing both rudder pedals and only used the manual brake control late, shortly before the aircraft stopped. He said there were no vibrations or shocks during the landing roll and that the nose gear remained in a fixed position. Regarding his training, the pilot said he knew the braking system of F-GCIM but was more accustomed to systems operated by pressing the upper part of the rudder pedals. ## Findings and conclusion At the Granville landing, the nose wheel probably remained locked in the aircraft’s axis. The nose gear shock absorber was not compressed enough, probably because of excessive aft stick input. This input may be explained by the pilot’s attention to maintaining the runway centreline in crosswind. From a certain speed, the rudder was no longer sufficiently effective and the crosswind acting on the empennage turned the aircraft to the left, into the wind (weathervane effect). With the nose gear lightened and locked in the aircraft’s axis, the pilot could not prevent the path deviation and the runway excursion. The reflex action on the rudder pedals had no effect because, on this aircraft, braking is obtained by operating a manual control on the instrument panel. This confusion is explained by the pilot’s relatively limited experience on F-GCIM. The stress generated by the unexpected situation also led him to act according to the skills acquired during his initial training. Although the crosswind limit had been demonstrated by the manufacturer in a “full flaps” configuration, the flight manuals of many aircraft recommend an intermediate configuration, which, because of a higher landing speed, allows better control of the aircraft. However, landing with flaps in an intermediate position changes the final approach parameters and attitude and increases the landing distance and therefore the risk of a longitudinal runway excursion. The number of runway excursions in general aviation is nearly constant each year. In 2006, the BEA published a study titled “Technical mastery during landing and self-knowledge,” which, in particular, describes the implications of the nose gear locking system on Robin aircraft and of crosswind on landing. This study is available on the BEA website, in the “Safety studies” section.