A Human Factors Approach to Preventing Tail Strikes Captain Vern Jeremica Senior Safety Pilot Boeing Commercial Airplanes May 2004 1
Presentation Overview Tail strike statistics as of 2003 Engineering/procedural improvements & general information Human factors review of a 2003 tail strike Review causes and prevention Future strategy for tail strike prevention Training recommendations Summary W100.2
Million Landings per Year 1.2 1.0 0.8 0.6 0.4 737-300 737-400 737-800 757-200 767-200 767-300ER 777-200 747-Classic 747-400 MD11 Operations Per Year for Models with Tail-Strikes 12 Month Moving Average 737-300 (2.14 (1.92 on 12/01/01) 12/01/03) 737-800 757-200 737-400 767-300ER 747-400 777-200 0.2 747-Classic 767-200 MD11 0.0 84 86 88 90 92 94 96 98 00 02 04 06 Year Boeing Proprietary W100.3
40 Tail-Strike Rate History 1991-2003 12 Month Moving Average (except MD11 = 24MMA) Tail-Strikes per Million Landings * 30 20 10 737-300 737-400 737-800 757-200 767-200 767-300ER 777-200 747-Classic 747-400 MD11 0 91 92 93 94 95 96 97 98 99 00 01 02 03 04 Year * Tail skid contacts without damage are not included. MD11 contacts with only VHF antenna or drainmast damage are not included. Boeing Proprietary W100.4
160 Tail-Strike History Tail-Strikes vs. Number of Flights 140 747-Classic 737-300 737-400 757-200 Cumulative Number of Tail-Strikes * 120 100 80 60 40 737-400 757-200 747-Classic 737-300 20 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Number of Flights (million) * Tail skid contacts without damage are not included. Boeing Proprietary W100.5
30 747-Classic 757-200 Tail-Strike History Tail-Strikes vs. Number of Flights 737-300 25 737-400 Cumulative Number of Tail-Strikes * 20 15 10 5 MD11 737-800 747-400 737-300 737-400 737-800 757-200 767-200 767-300ER 747-Classic 747-400 777-200 MD11 767-200 767-300ER 777-200 0 0 1 2 3 4 5 6 Number of Flights (million) * Tail skid contacts without damage are not included. MD11 contacts with only VHF antenna or drainmast damage are not included. Boeing Proprietary W100.6
16.00 Takeoff and Landing Tail-Strike Rates From Entry Into Service Through 12/1/03 Tail-Strikes per Million Landings 14.00 12.00 10.00 8.00 6.00 4.00 2.00 Landing/Unknown Takeoff Airplanes with Tail Skids * 0.00 0.0 0.0 0.0 0.0 0.0 0.0 737-300 737-500 737-600 737-700 747-Classic 747-400 757-200 767-200 777-200 MD11 737-400 ** 737-800 ** 737-900 ** 757-300 767-300/300ER 767-400ER 777-300 * Tail skid contacts without damage are not included. ** 737-400/-800/-900 tail skids not designed for landing protection. Boeing Proprietary W100.7
10.0 (2) 9.8 Current and Historical Tail-Strike Rates Historical: From 12/98 to 12/03 8.0 (3) 8.1 Current: From 12/02 to 12/03 (--) indicates number of tail-strikes in 2003 Tail-Strikes per Million Landings 6.0 4.0 2.0 4.5 2.8 1.3 (1) 1.0 2.0 1.6 4.6 Airplanes with Tail Skids * 0.9 (3) 3.6 3.2 (3) 2.9 0.7 0.0 0.2 0.0 0.0 0.0 0.0 0.0 737-300 747-Classic 747-400 757-200 767-200 777-200 MD11 737-400 ** 737-800 ** 767-300/300ER * Tail skid contacts without damage are not included. ** 737-400 and 737-800 tail skids not designed for landing protection. Boeing Proprietary W100.8
Engineering/Procedural Improvements & General Information Newer designs incorporate improved elevator feel systems Aircraft such as the 737-400, 737-800/900, 767-300, 777-300, 757-300, 767-400 have tail skids which prevent damage from takeoff tail strikes but not landing tail strikes Longer bodied Boeing airplanes use relative higher rotation speeds (speed additives to V1,VR, and V2, to maintain equivalent tail clearance) More tail strikes occur on landing than on takeoff Tail strikes are cyclic W100.9
Worldwide Hull Loss Accident Rate 1959-2001 Hull loss accident rate, per million departures 50 45 40 35 30 25 20 15 10 5 0 1960 1965 1970 1975 1980 1985 1990 1995 Year 2001 W100.10
1950-2000 Focused on accidents, specifically hull loses Lessons learned from the accidents were used to improve aviation safety W100.11
21 st Century, A Different Approach For Every Accident There Are 100 Close Calls! Focus not only on accidents but just as important the close calls, incidents, and lessons learned from each flight LOSA, ASAP, FOQA, and AQP have much to offer! Study accidents, flight deviations, and incidents from a human factors perspective Specifically from a Threat & Error Management Perspective W100.13
747 Classic Tail Strike W100.14
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Human Factors Man is error prone Crews can and will occasionally string a chain of errors resulting in an accident! The error chain for a tail strike accident can be very short! Stop the accident by breaking the error chain. How? Threat & Error Management-Crew Resource Management Concept- Newest Generation of CRM W100.17
Threat and Error Management Threats Threat Mngmt Errors Error Mngmt Outcome W100.18
Threat and Error Management Significant in: Accident Investigation LOSA, FOQA, ASAP Training Evaluation Design The way an airline operates W100.19
Definition of Terms Threats: are situations external to the flight deck, that must be managed by the cockpit crew during normal, everyday flights. Such events increase the operational complexity of flight and pose a safety risk to the flight at some level. Errors: are actions or inactions by the crew that lead to deviations from organisational or flight crew intentions or expectations. Errors in the operational context tend to reduce the margin of safety and increase the probability of accidents or incidents. W100.20
Threats Crew was in delay and was rushed The airplane was dispatched with an inoperative APU, with hot weather and minimal air on the flight deck and cabin. The center fuel pump gauge was on a MEL Non-standard cross bleed start procedure The scavenge fuel pump was on a MEL Flight Engineer busy working technical issues and mechanical portion of his seat failed Second flight engineer working in the cabin with passenger issues W100.21
How Did The Crew Manage The Threat? 20 minutes sterile cockpit rule was broken The way duties were delegated while the crew was rushing to catch up with the delay--- broke down the safety net Flight Engineer was overloaded The crew was rushing W100.22
Errors Engineer entered Takeoff Data using zero fuel weight as gross weight into the computer. Data was entered incorrectly and data insertion not checked. Data computer for takeoff calculations was not used per correct procedure: Error was over 220,000 lbs V1:123, VR:123, V2:142 (Incident Speeds) V1:154, VR:164, V2:171 (Tech. Order Speeds) Captain checked numbers instead of First Officer who was trained/required Data was double checked but no indication it was compared to the Load Sheet No one on the flight deck did a Reasonable Check! Was the crew under stress? W100.23
How Did The Crew Manage Errors & Aircraft Undesired States? Data Insertion? Error-undetected 1 st Rotation-Undesired Aircraft State-Managed 2 nd Rotation-Undesired Aircraft State-Managed Tail Strike Discovery? Managed past errors W100.24
Takeoff Risk Factors Mis-trimmed stabilizer Improper Rotation Techniques Improper use of the flight director Rotation prior to VR-either: Early rotation: Too aggressive, misinterpretation Early rotation: Incorrect takeoff speeds (Human Factors) Excessive initial pitch attitude Crosswinds W100.25
Review Proper Takeoff Techniques Use normal takeoff rotation technique Do not rotate early Do not rotate at an excessive rate or to an excessive attitude *Ensure takeoff V speeds are correct and adjusted for actual thrust used Consider use of greater flap setting to provide additional tail clearance Manage gusty winds and use proper amount of flight controls during crosswinds *Note: From a human factor perspective, a common error with a high level of consequence W100.26
Tail Strikes During Gusty Crosswind Conditions Boeing Flight Crew Training all model change Use max takeoff thrust Momentarily delay rotation during the gust Use normal rate of rotation Limit control wheel input to maintain wings level Avoid excessive control wheel displacement Smoothly transition from slip after liftoff W100.27
Landing Risk Factors Un-stabilized approach Holding airplane off the runway in the flare Mis-handling of crosswinds Over-rotation during go-around *Note: Tail strikes on landing generally cause more damage. The tail may strike the runway before the main gear damaging the aft pressure bulkhead. W100.28
Landing Risk Danger Landing tail strike damage can cause pressure bulk head failure Short term, if damage is not corrected or flight is continued-risk of structural failure Long term, if repair was not properly corrected-risk of structural failure W100.29
Maintenance Issue Post tail strike flight-ensure maintenance inspection prior to next flight Maintenance inspection must be accomplished by qualified maintenance Aircrew is not qualified to conduct the inspection W100.30
Proper Landing Techniques Maintain an airspeed of Vref + 5 knot minimum to start of flare and fly the approach at Specified Target Airspeed Airplane should be in trim at start of flare; do not trim in the flare or after touchdown Do not hold the airplane off in an attempt to make an excessively smooth landing Use only appropriate amount of rudder/aileron during cross wind approaches and landing Immediately after main landing gear touchdown, release back pressure on control wheel and fly the nose wheel onto the runway Do not allow pitch attitude to increase after touchdown Do not attempt to use aero braking - it does not work! W100.31
Future Strategy For Accident Prevention TEM is a major strategy to prevent cyclic occurrences of tail strikes TEM Training-Aircrews, Instructors, Check Airman, and Safety Personnel Threat and Error Management becomes part of the way aircrews operate: Used in Flight Operations Major emphasis during all crew training and evaluations W100.32
Training Recommendations As the crew member: Assess yourself in training or during your next operational takeoff and landing Assess each other s rotation rates and techniques When training in the simulator, check your tail clearance if this function is installed As the trainer: Evaluate tail clearance during takeoffs and landings Use scenarios that create Threats that can test and measure the crew s capability to prevent tail strikes Evaluate how the crew deals with errors W100.33
Continental Airlines Tail Strike Prevention Program Reduced operational tail strikes to almost nil Use of a crew self monitoring tail strike clearance tool Pitch report for every takeoff and landing available for crew review If within 1 degree of maximum it auto prints Air Canada is adopting W100.34
To Prevent Tail Strikes Crew members: Adhere to proper takeoff and landing techniques Apply the lessons learned. Know the pitfalls. Don t assume! Double check the takeoff data, especially if something doesn t look right. Coordinate insertion of the ZFW with another crew member. Double check data with the load sheet. Must know their airplane! Have an idea about the T/O and Approach speeds. When setting airspeed bugs always do a Reasonable Check! Must be aware of the differences between models and types, especially when transitioning from other equipment If a tail strike occurs, follow the CHECKLIST! Assess your takeoffs and landings. W100.35
To Prevent Tail Strikes The Airline should: Stress proper landing and takeoff techniques during all training and evaluations Make Tail Strike Prevention part of the safety program: Posters, Briefings, Videos, CBT, CD s, etc. Use a tail clearance measuring tool for all takeoffs and landings during simulator training and evaluations, (provide feedback to crews) Use a self measuring tail strike crew reporting tool! Ensure that FOQA is not used as a punitive device W100.36
Final Thought Use Threat & Error Management to: Manage the threats Mitigate and reduce errors W100.37