CONTAMINATED AND SLIPPERY RUNWAYS Contaminated and Slippery Runways Cont Rwy.2 CONTAMINATED AND SLIPPERY RUNWAYS Agenda: • Basic Regulations and Definitions • Physics of Contaminated Runways • Operational Practice • Operational Data/Applications • Other Considerations Cont Rwy.3 CONTAMINATED AND SLIPPERY RUNWAYS Contaminated runway – More than 25% of the runway is covered by slush, standing water, snow covered, Ice covered or compacted snow Cont Rwy.4 CONTAMINATED AND SLIPPERY RUNWAYS Regulatory Requirements • FAA Operators Historically No definitive regulatory requirements for contaminated or slippery runway performance adjustments in Part 25 or 121 Current (737-6/7/8/900) - Wet runway is part of AFM certification basis No definitive regulatory requirements for contaminated or slippery (non-wet) Cont Rwy.5 CONTAMINATED AND SLIPPERY RUNWAYS Regulatory Requirements • FAA Guidelines: – Current approved guidelines published in Advisory Circular 91-6A, May 24, 1978 – Provides guidelines for operation with standing water, slush, snow or ice on runway – Does not provide for wet runways – Proposed Advisory Circular 91-6B (draft) Cont Rwy.6 CONTAMINATED AND SLIPPERY RUNWAYS Regulatory Requirements • JAA Operators - New certifications – Specific requirements covered in the AFM – Includes performance based on various runway conditions (wet, compact snow, wet ice, slush, dry snow) • JAROPS 1 – Requires operational contaminated/slippery runway data based on possibility of an engine failure Cont Rwy.7 CONTAMINATED AND SLIPPERY RUNWAYS Proposed Advisory Circular 91-6B: • Guidelines for takeoff and landing with water, slush, snow or ice on runway – Defines contaminated runway – Defines braking coefficient used for accelerate-stop distance calculation – Includes wet runway – Reverse thrust credit for accelerate-stop • Did not specifically address, but were adopted in the advisory data of the time – 15-foot screen height for accelerate-go Cont Rwy.8 CONTAMINATED AND SLIPPERY RUNWAYS JAR-OPS 1 / AMJ15X1591: • Guidelines for takeoff and landing with water, slush, snow or ice on runway – Defines contaminated runway – Defines braking coefficient and contaminant drag to be used in calculations – Includes wet runway – 15-foot screen height for accelerate-go – Reverse thrust credit for accelerate-stop Cont Rwy.9 CONTAMINATED AND SLIPPERY RUNWAYS Dry, Damp, and Wet Runways are NOT Contaminated • Dry: Neither wet or contaminated (JAR-OPS 1.480) – FAA - No definitive definition • Damp: Surface is not dry, but moisture on the surface does not give a shiny appearance (JAR-OPS 1.480) • Wet: - FAA - neither dry nor contaminated (Draft AC 91-6B) - Shiny in appearance, depth less than 3 mm of water (JAR-OPS 1.480) Cont Rwy.10 CONTAMINATED AND SLIPPERY RUNWAYS Runways are CONTAMINATED When:* • More than 25% of the surface to be used is covered by standing water or slush more than 1/8 inch (3 mm) deep OROR • Has an accumulation of snow or ice *As defined by FAA Advisory Circular 91-6B Cont Rwy.11 CONTAMINATED AND SLIPPERY RUNWAYS Additional considerations: • If the contaminants are lying on that portion of the runway where the high speed part of the takeoff roll will occur, it may be appropriate to consider the runway contaminated. (Draft AC 91-6B) • Do NOT takeoff when the depth of standing water or slush is more than: 1/2 inch (13 mm) deep Cont Rwy.12 CONTAMINATED AND SLIPPERY RUNWAYS Boeing Contaminated Runway Takeoff Performance • Slush / Standing Water Data – Acceleration/deceleration capability • Slippery runway –Deceleration capability Ice covered, compacted snow, or wet Cont Rwy.13 CONTAMINATED AND SLIPPERY RUNWAYS Agenda: • Basic Regulations and Definitions • Physics of Contaminated Runways • Operational Practice • Operational Data/Applications • Other Considerations Cont Rwy.14 CONTAMINATED AND SLIPPERY RUNWAYS 1 Takeoff Distance Is Proportional to a • Large Acceleration (a) Short Takeoff Distance • Small Acceleration (a) Long Takeoff Distance Cont Rwy.15 CONTAMINATED AND SLIPPERY RUNWAYS Dry Runway Acceleration Friction Drag Thrust g a = W []Thrust - Drag - Friction Cont Rwy.16 CONTAMINATED AND SLIPPERY RUNWAYS Acceleration with Slush/Standing Water Friction Drag Thrust SlushSlush DragDrag g a = W []Thrust - Drag - Friction - Slush Drag Cont Rwy.17 CONTAMINATED AND SLIPPERY RUNWAYS 2 Slush ρ F = 1/2 Vg CD Slush ATire ρ = Slush Density, 1.65 slugs/ft3 Equal to Specific Gravity of 0.85 Vg = Ground Speed - Feet per Second CD = Slush Drag Coefficient for airplane's Slush specific gear arrangement ATire = Reference Area for Slush Force Calculation Data Sources: FAA/NACA Convair 880 Tests 1962 NASA Langley Load Track Tests - 1960,1962 Cont Rwy.18 CONTAMINATED AND SLIPPERY RUNWAYS CD Slush Accounts for Displacement and Impingement FWD Displacement Drag Impingement FWD Drag Cont Rwy.19 CONTAMINATED AND SLIPPERY RUNWAYS Tire Reference Area for Slush Calculation ATire = (Σ bmain + Σ bnose) x Slush Depth Slush depth b Average tire width Cont Rwy.20 CONTAMINATED AND SLIPPERY RUNWAYS Slush Force Hydroplaning Slush force Ground speed VHP Cont Rwy.21 CONTAMINATED AND SLIPPERY RUNWAYS Hydroplaning Tire Pressure in psi evaluated for Main Gear Tire Pressure V = 8.63 80’s, 90’s method HP Specific Gravity = 8.63 Tire Pressure Current method Cont Rwy.22 CONTAMINATED AND SLIPPERY RUNWAYS Slush Force Including Hydroplaning F = (1/2 ρ C V 2 A ) x f s DSlush g Tire HP Slush force Ground speed VHP 2.5V g -1.5) 1.6V -V ( V f = HP g HP This factor is applied at speeds HP above the hydroplaning speed. [ .6VHP ] Cont Rwy.23 CONTAMINATED AND SLIPPERY RUNWAYS Slush Force From Rotation to Liftoff F = (1/2 ρ C V 2 A ) x f x f x f s DSlush g Tire HP R LOF Slush force VHP VR VLOF Ground speed Cont Rwy.24 CONTAMINATED AND SLIPPERY RUNWAYS Force Variation With Speed All engine thrust Engine out thrust Airplane acceleration forces Slush Drag Aero Drag Rolling Friction VHP VR VLOF Ground speed Total Acceleration Force = Thrust - (Slush force + Aero drag + Friction) Cont Rwy.25 CONTAMINATED AND SLIPPERY RUNWAYS All Engine Acceleration Capability 130 Knots 6 mm of slush - 10-20 % reduction in all engine acceleration 13 mm of slush - 20-40 % reduction in all engine acceleration Dry 4.0 Dry Dry Dry 6 mm 6 mm 6 mm 6 mm 3.0 13 mm 13 mm 13 mm All engine 13 mm acceleration 2.0 Kt/sec 1.0 0.0 747 767 757 737 Cont Rwy.26 CONTAMINATED AND SLIPPERY RUNWAYS Engine Out Acceleration Capability 130 Knots 6 mm of slush - 15-50 % reduction in engine out acceleration 13 mm of slush - 30-110 % reduction in engine out acceleration Dry all Dry all Dry all Dry all engine engine engine 4.0 engine 3.0 Engine out Engine out Engine out Engine out Dry Acceleration 6 mm 2.0 Kt/sec 13 mm Dry Dry Dry 1/4" 6 mm 1/4" 6 mm 1.0 1/2" 13 mm 6 mm 1/2" 13 mm 13 mm 0.0 -0.5 747 767 757 737 Cont Rwy.27 CONTAMINATED AND SLIPPERY RUNWAYS Effect of Slush On Airplane Stopping • Tire to ground friction reduced due to slush • Retarding slush drag acts to slow the airplane Dry runway Average brake force Retarding force Total Slush stopping force = Slush Drag + Wheel braking Slush drag Slush wheel braking 0.9Vhp Vhp Ground speed, knots Cont Rwy.28 CONTAMINATED AND SLIPPERY RUNWAYS One Engine Inoperative Deceleration Capability 130 Knots • Dry - AFM performance - includes maximum braking, spoilers, idle thrust • Slush - includes wheel braking, spoilers, reverse thrust, and slush drag Dry Dry Dry Dry 8.0 Deceleration 6.0 13 mm 13 mm Kt/sec 13 mm 13 mm 6 mm 6 mm 4.0 6 mm 6 mm 2.0 1/2" 0.0 747 767 757 737 Cont Rwy.29 CONTAMINATED AND SLIPPERY RUNWAYS Effect of Slush - All Engine 767-300 - 182,800 kg, V1 = 163 IAS Baseline - AFM balance field length - 9520 Feet V =163 IAS 35 Feet 1 Go Accelerate V=0 Stop Runway available Effect of using dry runway performance on slush covered runway All engine performance- 6 mm slush Margin 15% All engine performance- 13 mm slush Margin 5% Cont Rwy.30 CONTAMINATED AND SLIPPERY RUNWAYS Effect of Slush - Engine Out 767-300 - 182,800 kg, V1 = 163 IAS • Effect of using dry runway performance on slush covered runway • Engine out performance - 6 mm slush 14 Feet Go V1= 163 IAS Accelerate V= 138 knots V=0 Stop Runway available - 9520 feet • Engine out performance - 13 mm slush Liftoff V1= 163 IAS Go Accelerate V= 142 knots V=0 Stop Cont Rwy.31 CONTAMINATED AND SLIPPERY RUNWAYS Agenda: • Basic Regulations and Definitions • Physics of Contaminated Runways • Operational Practice • Operational Data/Applications • Other Considerations Cont Rwy.32 CONTAMINATED AND SLIPPERY RUNWAYS Boeing Contaminated Runway Data Adjustments - Choices • All engines operating – Weight reduction – No V1 adjustment provided – Preserves 15% margin •Engine failure is considered - JAROPS 1 –Weight reduction and V1 adjustment provided –Credit for reverse thrust –15 foot screen height Data presented in airplane Operations Manual, FPPM, and PEM Cont Rwy.33 CONTAMINATED AND SLIPPERY RUNWAYS FAR Dry Field Length Typical Twin Engine Airplane Weight Altitude Temperature Flap Accelerate - Go Distance Accelerate - Stop Minimum Runway Required - FAR Dry 1.15 All Eng Distance V V 1 1 balanced Cont Rwy.34 CONTAMINATED AND SLIPPERY RUNWAYS Contaminated Runway Case All Engine Data Weight Altitude Temperature Accelerate - Go Flap Distance 1.15 All Eng Distance All Engine Slush Runway Required Increase (Slush) Distance Accelerate - Stop { Minimum Runway Required - FAR Dry 1.15 All Eng Distance V V 1 1 balanced Cont Rwy.35 CONTAMINATED AND SLIPPERY RUNWAYS Constant Field Length Weight Reduction All Engine Data Altitude Temperature Slush All Engine Flap