Why do business aircraft go off the runway more often than commercial aircraft? Gerard van Es • 58th annual Business Aviation Safety Seminar • Montreal, Canada • April, 2013
What is a runway excursion? A veeroffor overrun off the runway surface during takeoff or landing
Do business aircraft go off the runway more often? Source: NLR-ATSI
Runway excursion accident rate Difference is getting smaller last 5 yrs Source: NLR-ATSI
Is runway excursion risk importantfor business aviation? • 35% of all take-off & landing accidents with business ops involved a runway excursion; • Can result in fatalities and/or significant damage to a/c; • In top 6 of NTSB Priorities on Business Aviation safety.
Some accident/incident data analysis • Source: NLR-ATSI Air Safety Database • Inclusion criteria: • Runway excursions with known causes; • Period 1980-2010; • Worldwide; • Single engine aircraft excluded; • Turbine/turboprop aircraft. • >1600 excursions met these criteria.
Flight phase and excursion type Source: NLR-ATSI
Top factors in runway excursions Percentage of all excursions with known factors
Exposure to risk factors • Similar distribution of top causal factors between business and commercial operations; • Difference in exposure to risk factors? • Knowledge of day to day operations needed; • Based on FDM/FOQA data; • Focus on landing.
Wet/contaminated runway operations • Reduction runway friction; • No good data on number of business operations on wet/contaminated runways; • Business a/c can operate at smaller airports: • Runway surface condition monitoring less sophisticated; • Less equipment for snow removal.
Unstabilised approaches • Influence on fast & high approaches; • Comparison typical rates: • Commercial operations: 1-8% of all approaches; • Business operations: 1-14% of all approaches; • Go-around rates following unstabilised approaches are low: • Only 1-2 % of unstabilisedapproaches resulted in a go-around; • Higher values in commercial ops. Source: NLR-ATSI/FSF
Fast approaches • Speed difference at threshold (VTH – Vapp )>15 kts; • 3-5 times more likely on business a/c operations. Source: NLR-ATSI
Long flare (long landing, deep landing) • Rate of landings >2,400 ft touchdown from threshold 8 Times more likely on business ops Source: NLR-ATSI
Tailwind operations More tailwind landings in business ops Headwind Kt. Tailwind Kt. Source: NLR-ATSI/FSF
Runway length in overruns occurrences • A/c type depended • No data on day-to-day ops Source: NLR-ATSI
Landing distance assessment • Issues with landing distance assessments at time of arrival: • Not always required by operator (dispatch assessment only); • Confusion on whether reverse thrust has been included; • Sometimes based on (un)factored AFM instead of realistic landing performance data; • No (good) data for contaminated runways; • No guidance on how to use actual operational landing distance information; • No safety factors applied.
Runway width in veeroffs occurrences Matches with runways normally used Source: NLR-ATSI
Wheel track comparison Commercial a/c Business a/c 5-14 m 2.5-6 m • Maximum allowable deviation from centerline is 9.1 m; • VMCG and X-wind adjustments could be needed on narrow rwys (not common on business a/c).
Demonstrated crosswinds (dry rwy) Buss Jets average: 26 kts Passengera/c average: 30 kts. Source: NLR-ATSI
Crosswind and contaminated runways • Not part of certification – advisory only; • Advisory material normally available for commercial a/c: • But not perfect! • Often limited advisory material for business a/c, e.g.: • Only for an icy runway; • Statements like “extreme care should be taken...”, no hard numbers; • Crosswind limits based on non-validated correlation with runway friction coefficient.
How to manage the risk? • Check out the different initiatives and tools, e.g.: • European Action Plan for the Prevention of Runway Excursions (EAPPRE); • IATA/FSF Runway Excursion Risk Reduction (RERR) Toolkit; • FSF - Runway Excursion Risk Awareness Tool: • Can be used during dispatch. • FSF - ALAR toolkit; • Guidance material from NBAA.
Remember there is more than factorcausing runway excursions Example • Excess approach speed, • Late touchdown, • Delayed application wheel brakes.
Conclusions • Runway excursion causes are the same for business and commercial aircraft; • Exposure to certain risk factors is often higher during business operations: • Unstabilised approaches; • Long landings; • Fast landings; • High tailwind landings. • Less guidance for operations on contaminated runways for business a/c; • Lack of FDM/FOQA data for business operations (less awareness of rwy excursion risk factors).
It can happen more than once.... • SANTOS DUMONT AIRPORT, Brazil Landing overrun Take-off overrun