Slippery Runways

159TH International Air Safety Seminar25 October 2006 Paris, France

Airplane Deceleration on Slippery Runways

What You Should Know

Mark H. SmithMark H. SmithBoeing Air Safety Investigation

2The Boeing Company


Airplane Deceleration On Slippery RunwaysAgenda

Certified vs. Advisory Landing Distance DataCertified vs. Advisory Landing Distance Data

Airplane Braking vs. Runway FrictionAirplane Braking vs. Runway Friction

Autobrake vs. Manual BrakesAutobrake vs. Manual Brakes

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Also Called: DispatchFactored

En routeUnfactoredOperational

Certified DataCertified Data Advisory DataAdvisory Data

Reqmts: Parts 25 & 121 Part 121

Location: Airplane Flight Manual (AFM)

Quick Reference Handbook (QRH)

Landing Distance DataData Provided by Boeing

Two sets of landing data are provided.

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Certified DataCertified Data Advisory DataAdvisory Data

Use:

Purpose: Provide factored landing distance as required by regulators

Determine landing distance requirements prior to dispatch

Provide actual landing distance capability of the airplane

Determine landing distance for operational decisions while en route

Landing Distance DataData Provided by Boeing

The two data sets are for different purposes and uses.

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Landing Distance DataBaseline Demonstrated Distance

RunwayThreshold

Air Distance

TouchDown

TransitionDistance

Auto-Speedbrakes DeployedBrakes Applied

Stopping Distance

Stop

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RunwayThreshold

Air Distance

TouchDown

TransitionDistance


Stopping Distance

Stop

Dry

50 ft

Distance from 50 ft 1sec Max. Manual BrakingBasis Distance

Basis for Certified Data Set

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RunwayThreshold

Air Distance

TouchDown

TransitionDistance


Stopping Distance

Stop

Reverse

1000 feet 1sec Max. Manual BrakingBasis Distance

Dry

Basis for Advisory Data Set

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RunwayThreshold

Reverse

1000 feet 1sec Max. Manual BrakingBasis Distance

Dry

Basis for Advisory Data Set

Dry

50 ft

Distance from 50 ft 1sec Max. Manual BrakingBasis Distance

Basis for Certified Data Set

Air Distance

TouchDown

TransitionDistance


Stopping Distance

Stop

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Dry runway Automatic Speedbrakes Max manual braking No reverse thrust

Stop

Basis Distance

FAR Dry

Basis Distance x 1. 67

CERTIFIED Data

Basis Distance

Basis Distance x 1. 67 x 1. 15

Basis Distance x 1. 67

Basis Distance

FAR Wet / SlipperyCERTIFIED Data

Landing Distance Data CERTIFIED Data Set

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Snow

Ice

Wet

Dry

Dry runway Automatic Speedbrakes Max manual braking With reverse thrust

ADVISORY DataDry Braking

Stop

1000 ft Reverse

Medium Braking

Poor Braking

Good BrakingBasis Distance

Landing Distance Data ADVISORY Data Set

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Dry runway Automatic Speedbrakes Max manual braking With reverse thrust

Good Braking

Medium Braking

Poor Braking

ADVISORY DataDry Braking

Stop

1000 ft Reverse

Snow

Ice

Wet

Dry

ReferenceDistance Dry runway

Automatic Speedbrakes Max manual braking No reverse thrust

Basis Distance x 1. 67 x 1. 15

FAR Wet / SlipperyFAR DryBasis Distance x 1. 67CERTIFIED Data

Stop

Basis Distance

Basis Distance

Landing Distance Data SummaryCERTIFIED Data vs. ADVISORY Data

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Landing Distance Advisory Data

Quick Reference Handbook (QRH) contains airplane landing distance data for various runway conditions and brake configurations.

Good

Med

Poor

Dry

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Landing Distance Advisory Data

QRH landing distance data is based on the notes at the bottom of the page.

Relevant notes include:- two engine detent reverse thrust

- 1,000 ft of air distance

- actual (unfactored) distances (JAR Ops include 15% margin)

Based on these notes

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Airplane Braking vs. Runway Friction Runway Condition Reporting

Three methods can be used to report runway conditionc Airplane Braking Action Reportd Runway Description e Runway Friction Measurement

Each method uses a different descriptor (scale)

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Airplane Braking vs. Runway Friction Summary of Reporting Methods

Better Braking

Worse Braking

Dry

WetDry Snow

Compact Snow

Wet SnowSlush

IceWet Ice

eRunway Friction

Measurement

dRunway

Description

cAirplane Braking

Action Report

Good

Med

Poor

Dry

Good

Med

Poor

ICAO

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Airplane Braking vs. Runway Friction Summary of Reporting Methods

eRunway Friction

Measurement

dRunway

Description

cCalculated

Airplane Braking

Good

Med

Poor

Dry

Good

Med

Poor

ICAOBetter Braking

Worse Braking

Dry

WetDry Snow

Compact Snow

Wet SnowSlush

IceWet Ice

QRHData

0. 4

0. 3

0. 2

0. 1

0. 0

Calculated AirplaneBraking

Coefficient

PAirplane

1. 0

0. 8

0. 6

0. 4

0. 2

0. 0

MeasuredRunwayFriction

Coefficient

PRunway

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Deceleration Available MoreLess

Airplane Braking vs. Runway Friction Deceleration Available from Brakes

Slippery RunwayP Runway (Tire Skid Point)

initially, brakes will attempt full pressure but this would lock the wheels

P -Airplane (Braking Capability)

Max Brakes

e.g., stand on the brake pedals

Worse

Better

Braking Conditions

P -Runway (Tire Skid Point)Dry Runway

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Deceleration Available MoreLess


Max Brakes

Slippery RunwayP Runway (Tire Skid Point)

P -Airplane (Braking Capability)P -Runway (Tire Skid Point)

Dry Runway


Worse

Better

Braking Conditions

AntiskidP Airplane (Braking Capability)Method c

Method e

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Deceleration Availablefrom Brakes

MoreLess


Max Brakes


Dry

Antiskid

Good

Med

Poor

Braking Conditions

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MoreLess


DryGood

MedPoor

Decel. Available from Brakes

Deceleration Availablefrom Brakes

For reference in next section

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Autobrakes vs. Manual BrakesAirplane Deceleration

Total airplane deceleration is affected by three factors:

- Aerodynamic drag - Wheel brakes - Reverse thrust

If used, the autobrake system- Targets a deceleration level- Brakes applied as required to reach target level

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Total Airplane Deceleration MoreLess


Braking AppliedMax Manual

Autobrake Max

Autobrake 2

BrakesDrag Reverse Thrust

BrakesDrag

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Autobrake Max

Autobrake 2


BrakesDrag


BrakesDrag


BrakesDrag

Deceleration levelvalid with or without

reverser thrust

DecelTarget

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Autobrakes vs. Manual BrakesTotal Airplane Deceleration

Braking Applied

DryGood

MedPoor


Max Manual

Autobrake Max

Autobrake 2


Decel. Target

BrakesDrag


BrakesDrag


BrakesDrag

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DryGood

MedPoor



Autobrakes vs. Manual BrakesDry Braking


Autobrake Max

Autobrake 2


Decel. Target

BrakesDrag


BrakesDrag


BrakesDrag

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DryGood

MedPoor



Autobrakes vs. Manual BrakesGood Braking


Autobrake Max

Autobrake 2


Decel. Target

BrakesDrag


BrakesDrag


BrakesDrag

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DryGood

MedPoor



Autobrakes vs. Manual BrakesMedium Braking


Autobrake Max

Autobrake 2


Decel. Target

BrakesDrag


BrakesDrag


BrakesDrag

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DryGood

MedPoor



Autobrakes vs. Manual BrakesPoor Braking


Autobrake Max

Autobrake 2


Decel. Target

BrakesDrag


BrakesDrag


BrakesDrag

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Autobrakes vs. Manual BrakesSummary

Manual BrakesDry runway: Reversers are additive

Slippery runway: Reversers are additive

AutobrakesDry runway: Reversers not additive

Slippery runway: Reversers may be additive

Landing Distance Advisory Data in the QRH includes reversers for Manual and Autobrakes

Documents

Slippery Runways