ACCIDENT CAUSES

An accident can have any number of factors, but the NTSB tries to find a singular event that led to the outcome. This is the defining event, and every accident has one. A look at the defining events for seaplanes reveals that abnormal runway contact (ARC) leads seaplane causes with 86 accidents followed by loss of control in flight (LOC-I) with 79 accidents. Third, system component failure-power plant (SCF-PP) has 55 accidents. Fourth and rounding out two-thirds of the accidents is loss of control on ground (LOC-G) with 46 accidents.

Defining Events

ARC is not limited to traditional paved runways as the NTSB loosely defines a runway as any landing surface. Thus, water lanes, rivers, lakes, gravel strips, turf, etc. are all considered runways for the purpose of ARC causes.

SCF-PP is best thought of as engine and propeller failure. Causes listed may include additional factors outside of the pilot’s control—for example, mistakes made by maintenance providers.

LOC-G differs from LOC-I as all the events take place when the aircraft is on the ground. In cases where the aircraft is transitioning during takeoff or landing, the NTSB tries to determine where the event originated. If the aircraft was already swerving off the runway and made it into the air, albeit briefly, the NTSB would probably view this as LOC-G instead of LOC-I as the flight was not under control during the portion before the aircraft left the surface.

Abnormal Runway Contact

ARC Analysis

It’s no surprise that ARC leads the landing phase with 90 percent of accidents. ARC during takeoff may sound confusing, but these are cases where the aircraft became airborne briefly and returned to the surface. For example, if the aircraft became airborne due to a wind gust and abruptly dropped back to the surface with force, it could constitute an ARC accident. The location for these is primarily during the takeoff roll.

Gear-down water landings dominate ARC accidents, accounting for 35 of the primary causes of ARC accidents. Hard landings (18) are second, followed by windy conditions (7), and glassy water conditions (6) rounding off most issues related to ARC accidents.

Loss of Control In Flight

LOC-I Analysis

LOC-I accidents appear more spread out across flight phases with initial climb leading (24), followed by maneuvering (18), and takeoff (15). Initial climb accounts for 30 percent of all accident causes. Maneuvering accounts for only 23 percent but it represents most fatal accidents compared to the other phases. Lethality—a measure of total accidents to fatal accidents—is 72 percent in maneuvering alone, making LOC-I maneuvering accidents close to a three-to-one possibility of suffering a fatality if you encounter such an event.

Stall/spin (41) is the leading issue in LOC-I accidents. General loss of control not associated with a stall/spin (15) is second. Non stall/spin loss of control is best thought of as directional control issues and accidents where it was too difficult to determine if a stall/spin occurred. Nine LOC-I accidents had winds affect them—either tail or crosswind—that subjected the aircraft to forces leading to loss of control.

System Component Failure-Power Plant

SCF-PP Analysis

SCF-PP accidents largely occur during the en route phase (19) followed by initial climb (15). These two flight phases make up roughly two-thirds of all SCF-PP accidents. One may suspect takeoff as the most likely location for an engine failure—as this is the place where the engine is accelerating the aircraft and running at its highest power setting—but it is shortly after getting airborne and climbing out of ground effect where initial climb begins. This location is where the engine loses all the benefits of being near the ground. While initial climb is second, en route makes the most sense due to failure over time. If the engine were already broken it would fail to start and run nominally. In the case of en route, the engine has adequate time for an issue to arise and lead to failure. Fatigue cracks usually take time to propagate, and damage needs continuous force to exacerbate the issue. On a positive note, SCF-PP rarely suffers from high fatalities and powerplant issues are largely survivable across all phases of flight, provided pilots take appropriate action.

Loss of Control on the Ground

LOC-G Analysis

LOC-G occurs more than 65 percent of the time during the landing phase accounting for 30 accidents. Again, this cause suffers few fatalities, in large part because the aircraft is on the ground and the airspeed is low; these two factors reduce impact forces. Least suspicious are the limited phases landing, takeoff, and taxi for this cause as LOC-G occurs on the ground. Loss of directional control is a major contributor to LOC-G accidents—rudder use is critical to avoid LOC-G and maintain directional control.

Two ARC Case Studies Emphasize Common ARC accidents.

In the case of a Cub Crafters PA-18 (NTSB Accident Report CEN11LA632), the pilot’s choice to make an impromptu decision and his failure to retract the gear resulted in a nose-over on touchdown. The accident pilot departed a land-based airport and decided to perform a touch and go at a lake en route to the final destination. After departure, the pilot failed to retract the landing gear, and the gear warning system activated too late—at about the time of touchdown—resulting in a nose-over.

In the case of a hard landing (NTSB Accident Report CEN12LA187), an ATP-rated pilot failed to properly flare. The aircraft struck the water and cart-wheeled coming to rest inverted. Sadly, the pilot was unable to exit the aircraft and drowned. While a number of water conditions can make the distance from the surface difficult to judge (e.g., glassy water landings), pilots need to find additional landmarks and monitor the aircraft’s descent rate to help judge their aircraft’s height above the water surface.

LOC-I Case Study

Stall/spin during maneuvering flight remains the leading fatal LOC-I cause and phase. In the case (NTSB Accident Report CEN10FA182) of a pilot flying along a river at 500 feet agl, the turn toward a residence resulted in an aerodynamic stall. The pilot had departed from a runway near the river and began a brief flight down the river before executing a turn low to the ground. In these cases, distraction or reduced speed can increase the stall risk; executing a steep turn also positions the aircraft into an accelerated stall. Using a cross-check, ensuring coordinated maneuvering, and checking airspeed and coordination every three to five seconds provides better situational awareness and helps mitigate speed related stalls and spins.