Runway Excursion analysis on A320 ethiad
- 1. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 1 Safety Information Bulletin Reducing the Risk of Runway Excursion
- 2. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 2 The Safety Information Bulletin (SIB) is a tool used by Corporate Safety & Quality department to promulgate safety related information to Etihad personnel concerning hazard recognitions, evaluation and may include recommendations derived from accidents, incidents, investigations, safety analysis and international organizations. A special edition for flight crew was developed aiming to cater for the specific technical and safety related issues related to flight safety. Suggestions, feedback, queries and recommendations may be sent to the flightsafety@etihad.ae email address. Safety Information Bulletin
- 3. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 3 In this landing overrun incident in 1999 the aircraft aquaplaned after a long landing. Full reverse thrust was not selected and the ground spoilers did not initially deploy. The aircraft departed the runway at speed of about 95 kts (171 km/h) Excursion
- 4. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 4 Consequence The consequences of the B747 Bangkok overrun could have been far worse but for the fact the overrun area was relatively flat and free of obstacles. Most often this is not the case.
- 5. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 5 Introduction • A runway excursion occurs when an aircraft departs the end or side of the runway surface. A departure from the end of the runway is termed an overrun whereas a departure from the side of a runway is termed a veer off or offside (Boeing term). • The purpose of this SIB is: • To state the frequency of runway excursion events • To raise awareness in the pilot group of runway excursion risk factors • To present risk mitigation techniques • To provide an indication of the time it takes to veer off or overrun a runway. (based on a twin engine wide bodied aircraft). The figures provided serve as a useful general reference. For specific landing and takeoff performance information and aircraft geometry the pilot should as always refer to the applicable FCOM and FCTM.. • To highlight Etihad specific landing events and to make a case against complacency • To discuss in some depth the difficulty of the rejected landing decision- and to refer the reader to the appropriate guidance documentation.
- 6. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 6 Frequency • According to statistics compiled by IATA between 2004-2008 there were 502 commercial aircraft accidents worldwide of which 136 were runway excursions. • Of the 136 runway excursions 18% occurred on takeoff and 82 % on landing. • In 35% of landing runway excursions, the pilot did not conduct a go-around regardless of the existence of strong cues to do so. • The African (AFI) and Middle East and North African (MENA) region had the highest rate of runway excursions per million sectors flown.
- 7. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 7 Risk factors - Takeoff • Operational • Degraded directional control due to aft centre of gravity. • Rejected takeoff either not carried out or if carried out not done correctly. • Unsatisfactory aircraft handling. • Improper calculation of take-off performance speeds . • ‘Risky shift’-the tendency of a group of people to make a more risky decision than they would make individually. • Organizational • Policies which discourage the use of full take off thrust. • Flex or reduced thrust takeoffs increase the risk of a runway overrun (but decrease the risk of a runway veer off). • Meteorological • Crosswind or adverse windshear. • Runway contamination. • Reduced visibility. • Mechanical • Tyre failure. • Engine failure. • Thrust asymmetry (other than due to engine failure).
- 8. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 8 Risk mitigation-Takeoff • Check take off performance calculations for reasonableness. Carry out the calculations independently. • Review and understand the factors applicable to the RTO decision. • Review and understand the guidance material for aircraft handling on contaminated runways. • Review and understand the guidance material on aircraft handling in the event of thrust or drag asymmetry . Thrust/drag asymmetry can include engine failure, tyre failure, asymmetric reverser deployment. • Use a takeoff thrust setting and configuration appropriate to the conditions. • Don’t takeoff in conditions of windshear. • Review and understand the guidance material for takeoff in crosswind conditions. • When operating with four crew members on the flight deck be aware of the existence of ‘risky shift’
- 9. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 9 Risk factors - Landing • Operational • Continuation of an unstabilised approach. • ‘Risky shift’-the tendency of a group of people to make a more risky decision than they would make individually. • Poor landing technique or rejected landing decision making • Hard/bounced/long landing. • Degraded directional control due to aft centre of gravity. • Organizational • Policies which discourage the full use of all braking aids available to the flight crew such as the delayed application of brakes; less than full flap landing; non use of full reverse thrust. • Meteorological • Crosswind or adverse wind shear. • Runway contamination. • Reduced visibility. • Mechanical • Asymmetric thrust. • Damaged landing gear.
- 10. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 10 Risk mitigation- Landing • Select the best runway for the existing conditions. • Fly a stabilized approach. • Make full use of the braking / deceleration aids available (i.e., auto brakes, maximum flap settings, auto ground spoilers, etc). • Do not delay deceleration on contaminated runways. • Calculate your landing performance and review your landing continuation / rejected landing decision making criteria. A go-around should be conducted at any time significant deviations are recognized during the flare and touchdown. • The combination of a contaminated runway and a tailwind or crosswind is a major contributing factor in accidents. Review the guidance material on crosswind landing techniques. • Brief the threats in adverse weather or runway conditions, be ready and prepared to make a go-around. • Review and understand the guidance material on aircraft handling in case of thrust or drag asymmetry especially in contaminated runway conditions. • When operating with four crew members on the flight deck be aware of the existence of ‘risky shift’ .
- 11. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 11 The Numbers On an ice covered runway with crosswind how long will it take to veer off the runway? • For a 60 m wide runway: • Assuming: • Touchdown on centreline. • Close to zero friction ( as is possible on icy runways or in dynamic aquaplaning). • For a 20 kt crosswind • The aircraft’s main gear will depart the runway in about 2.5 seconds. • For a 40 kt crosswind • The aircraft’s main gear will depart the runway in about 1.25 seconds Ice covered runway
- 12. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 12 The Numbers …cont’d How long will it take to veer off a runway following a loss of directional control? • Assuming • 60 m wide runway • Touchdown on centreline • Dry runway • VApp 140kts (nil wind) • MLG-Main Landing gear • NLG- Nose Landing Gear Sustained heading deviation from runway centreline Time to runway excursion 5° 4.5 seconds MLG 10° 2.25 seconds MLG 15° 1.7 seconds NLG 20° 0.9 seconds NLG
- 13. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 13 Etihad incident data • Recently a number of Etihad pilots reported an unsatisfactory autoland performance in Abu Dhabi as a result of an abrupt aircraft heading change shortly after touchdown (possibly due to ground equipment error or LLZ signal distortion). In one such incident the pilot reported experiencing a heading change of about 30°. The pilot had less than one second in which to prevent the aircraft veering off the runway. It was fortunate that the RVR was significantly higher than the CATIIIB visibility minima ,which allowed the PF to regain directional control promptly. In genuine 75m visibility it is likely the outcome would not have been favourable.
- 14. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 14
- 15. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 15 The numbers - how long can you float without risking an overrun? Groundspeed (kts) Groundspeed (m/s) Distance Remaining (m) Time over Distance 140 70 1052 15seconds Dublin Example: An A330-200 at 180,000kg in nil wind, sea level, dry, ISA conditions will require an actual landing distance of 1020m. Dublin runway 16 is 2072m in length giving a margin of 1052m. At an approach groundspeed of 140 kts if touchdown occurs more than 15 seconds after crossing the landing threshold a runway overrun may result. New York Example: An A346 at 255,000 kg in nil wind, sea level, dry, ISA conditions will require an actual landing distance of 1250m. New York runway 22L is 2560m in length giving a margin of 1310m. At an approach groundspeed of 150kts, if touchdown occurs more than 17.5 seconds after crossing the landing threshold a runway overrun may result. Groundspeed (kts) Groundspeed (m/s) Distance Remaining (m) Time over Distance 150 75 1310 17.5 seconds
- 16. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 16 Etihad FOQA data • Etihad Airways’ FOQA data shows that the highest rate of long landing occurs in Abu Dhabi where the runways are around 4000m in length. The current record for touchdown from the landing threshold is 1642m. • The reasons cited for long landing in Abu Dhabi include: • Tailwind on approach due to ATC runway configuration • A slight discrepancy between the glide slope and PAPI indications • Runway slope • Significant number of training flights into Abu Dhabi • Most of these elements are also present in Kathmandu which at 2930m presents a more challenging runway environment, yet the greater majority of landings at KTM are in the touchdown zone. • It is of course quite easy to misread and misrepresent statistical data, however the long landing data comparison between KTM and AUH , shown in the next slide, would suggest that complacency due to benign weather, airport familiarity, and long runways may also be a factor. • If the factors that produced a touchdown at 1642m in Abu Dhabi were repeated when landing on runway 22L in New York it is highly likely that with only 918m of runway remaining there would be an overrun into water. • Guard against complacency.
- 17. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 17 Touchdown point comparison AUH/KTM Number of events Touchdown point in metres
- 18. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 18 Touchdown in the touchdown zone * Some runways will be unforgiving of a long landing! • Font : Arial 16 * The desired Etihad touchdown zone is 300-600m from the landing threshold
- 19. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 19 The rejected landing decision …is not easy • Prior to takeoff, the aircraft is at a known position with a known energy level with a known runway distance remaining. A V1 speed is calculated which defines the speed at which a takeoff is either rejected or continued. The rejected takeoff decision therefore is relatively simple. • A rejected landing decision however is significantly more complicated since the aircraft’s position on / over the runway and its potential and kinetic energy state are not positively known and are rapidly changing. Moreover, the remaining runway distance (in the absence of Runway Distance Remaining Signs (RDRS)) is also difficult to determine with accuracy. Refer to the ATSB report in Appendix 3. • Once a prolonged float occurs, how then does the pilot know whether there is enough runway in which to stop the aircraft or whether a go around can be safely executed with respect to obstacles? The short answer is –he/ she doesn’t- and it is for this reason that the OM-A is quite prescriptive on the matter.
- 20. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 20 The rejected landing decision …is made easy • The guidance in the OM-A 8.3.19.24 states… If touchdown cannot be accomplished within the desired touchdown zone (which is 300-600m from the landing threshold for Etihad ) a missed approach should normally be initiated with due regard to the remaining runway length. (Refer Appendix 1) • To comply with the OM-A, especially on shorter runways, the pilot should predetermine physical features-such as taxiway intersections- which correspond to the 600m mark. • Alternatively the pilot can determine the time it will take to reach the 600m mark: • For the appropriate rejected landing techniques the reader should refer to guidance documentation in the FCOM and FCTM. The relevant parts of the Airbus FCTM are shown in Appendix 2. Boeing pilots should refer to the appropriate Boeing publications. Groundspeed (kts) Groundspeed (m/s) Time to 600m (seconds) 120 60 10 140 70 8.6 160 80 7.5 180 90 6.6
- 21. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 21 Safety and Quality are in your hands! Summary • Review your takeoff and landing risk factors. • Minimize your risk. • Maintain the centreline. • Touchdown in the touchdown zone • Predetermine a physical reference point (touchdown marker/taxiway intersection) or calculate a time since crossing the landing threshold, from which a go around must be made in order to comply with the recommendations of the OM-A 8.3.19.24. • Be aware of runway distance remaining on landing. Awareness is the key. • Guard against complacency.
- 22. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 22 Acknowledgements • ATSB-Australian Transport Safety Bureau • IATA-International Air Transport Association /Runway Excursion Risk Reduction • FAA-Federal Aviation Administration • FSF-Flight Safety Foundation
- 23. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 23 Appendix 1 OM-A • 8.3.19.24. Landing Within TDZ • The desired touchdown point lies at a distance between 300 m to 600 m from the landing threshold. Within this zone the landing shall be made. Corresponding runway markings, position of VASIS/PAPI bars and/or lighted touchdown wing bars are of great assistance in determining the correct aiming point. If touchdown cannot be accomplished within the desired touchdown zone, a missed approach should normally be initiated with due regard to the remaining runway length. Spool up of engines, aeroplane speed and pitch attitude must be considered carefully. It is of utmost importance to aim for the aeroplane to be tracking the runway heading prior to touchdown, consequently every effort must be made to land on and along the runway centerline. This will provide the best margin to recover from lateral control difficulties occurring after touchdown. *Note the FAA defines the Touchdown Zone to be 150-900m from the landing threshold. Etihad however defines it’s desired touchdown zone to be 300-600m from the landing threshold.
- 24. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 24 Appendix 2 FCTM extract • Factors Affecting landing Distance • For a 50 ft Threshold Crossing Height, a shallower glide path angle increases the landing distance, as the projected touchdown point will be further down the runway. • Floating above the runway before touchdown must be avoided because it uses a large portion of the available runway. The aircraft should be landed as near the normal touchdown point as possible. • Deceleration rate on the runway is approximately three times greater than in the air. • Reverse thrust and speedbrake drag are most effective during the high-speed portion of the landing. Therefore, reverse thrust should be selected without delay. Speed brakes fully deployed, in conjunction with maximum reverse thrust and maximum manual antiskid braking provides the minimum stopping distance.
- 25. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 25 Appendix 2… cont’d FCTM extract • Bouncing At Touch Down • In case of light bounce, maintain the pitch attitude and complete the landing, while keeping the thrust at idle. Do not allow the pitch attitude to increase, particularly following a firm touch down with a high pitch rate. • In case of high bounce, maintain the pitch attitude and initiate a go-around. Do not try to avoid a second touch down during the go-around. Should it happen, it would be soft enough to prevent damage to the aircraft, if pitch attitude is maintained. • Only when safely established in the go-around, retract flaps one step and the landing gear. A landing should not be attempted immediately after high bounce, as thrust may be required to soften the second touch down and the remaining runway length may be insufficient to stop the aircraft.
- 26. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 26 Appendix 2… cont’d FCTM extract • Rejecting the Landing • If a decision is made to reject the landing, the flight crew must be committed to proceed with the go around maneuver and not be tempted to retard the thrust levers in a late decision to complete the landing. • TOGA thrust must be applied but a delayed flap retraction should be considered. If the aircraft is on the runway when thrust is applied, a CONFIG warning will be generated if the flaps are in conf full. • The landing gear should be retracted when a positive climb is established with no risk of further touch down. Climb out as for a standard go-around. • In any case, if reverse thrust has been applied, a full stop landing must be completed.
- 27. Safety Information Bulletin – Flight Crew – Edition 03/2009 – Rev. 0 27 Appendix 3 ATSB recommendation regarding RDRS • Runway distance remaining signs (RDRS) are a simple and low cost measure to increase flight crew spatial awareness during the landing rollout. These are large, illuminated signboards on either side of the runway that indicate the distance remaining in thousands of feet . • On takeoff, pilots can use RDRS to check expected versus actual aircraft acceleration prior to rotation. • These signs have several safety benefits for landing: • if the aircraft lands long, they provide greater pilot awareness of remaining runway distance, allowing the pilots to make an informed decision about whether a go-around is warranted based on the risk of an overrun. • they are visible in all conditions, and are not obscured by ice or snow (unlike standard runway distance markings painted on the runway surface) and • the pilot is able to quickly realize if the aircraft is decelerating fast enough in the landing roll. • The FAA currently recommends that RDRS are installed on all runways used by jet aircraft (FAA, 2004a). Neither ICAO nor CASA require or recommend airport operators to install RDRS at the side of runways.