BOEING 767 36NOMNI AIR INTERNATIONAL INC
Kabul, AF · 2014-06-20·N768NA
What happened
NTSB summary, verbatimThe flight experienced a tailstrike on landing resulting in substantial damage to the fuselage and aft pressure bulkhead. There were no injuries to the passengers; however, four of the 16 crewmembers received minor injuries. According to the flight crew statements and recorder data, the landing reference speed for the approach was 145 knots. Due to the weather conditions, the flight crew added 10 knots to this for their approach speed due to the gusty weather conditions and conducted a visual approach using the visual approach slope indicator as guidance. As a result of the weather and gusty winds, airspeed fluctuated during the approach between 162 knots and 138 knots and engine thrust varied accordingly between about 86% N1 and 40% N1 on approach. The captain stated that the flight was on speed and glide path at 500 feet above the ground but at about 200 feet above the ground, the flight started to move above the glide path and airspeed started to increase. To compensate, the captain reduced engine power and then heard a "sink rate" aural alert when passing through about 50 feet. Flight recorder data indicated the engine N1 decreased to 40%, with throttles at forward idle position, at about 110 feet above the ground, and remained there until after touchdown. The airplane touched down at 140 knots and a nose up pitch attitude of 8.9 °, increasing to 9.5° immediately after touchdown. Guidance included in the operator's training manuals indicated that normal touchdown attitude should be between 4 and 6 degrees nose up. Additionally, guidance indicated that thrust should be managed on approach to maintain reference speed, plus any wind additive, until the beginning of the flare. After reaching the flare, thrust levers should be retarded smoothly to idle with main gear touchdown ideally occurring simultaneously with thrust levers reaching idle. An analysis of calculated vertical and horizontal wind effect indicated an existing updraft transitioned to a downdraft and a headwind component transitioned to a tailwind component during the last 5 seconds prior to touchdown.
Probable cause
the Board's determinationthe early reduction of engine thrust that resulted in an excessive sink rate and nose high pitch attitude during the landing flare. Contributing to the accident was a significant change in the vertical and horizontal wind components just prior to touchdown.
Occurrence sequence
2 stepsNTSB coding · CICTT taxonomy- 1 · Landing-flare/touchdownTailstrikedefining event
- 2 · Landing-flare/touchdownAbnormal runway contact
Findings
2 causal · 0 contributing- CAUSEPersonnel issues › Task performance › Use of equip/info › Aircraft control — Pilot
- CAUSEEnvironmental issues › Conditions/weather/phenomena › Wind › Sudden wind shift — Response/compensation
Sequence of events
3 timed eventsfrom the FDR factual report · claude-fable-5-1 (in-session)- approachapproachp.3Accident approach to runway 29 at Kabul began at approximately 9,600 ft pressure altitude; Kabul airport elevation approximately 5,900 ft MSL
- about 3 seconds before touchdownlandingp.3TAWS generated a Mode 1 'Sink Rate' alert
- touchdown, about 1937 local (1507 UTC)landingp.3Tail strike during landing on runway 29; maximum pitch during landing approximately 9.5 degrees, maximum vertical acceleration approximately 2.5 g, touchdown at approximately 140 knots computed airspeed; aircraft substantially damaged, 4 of 16 crew with minor injuries
NTSB analysis
from the final reportThe flight experienced a tailstrike on landing resulting in substantial damage to the fuselage and aft pressure bulkhead. There were no injuries to the passengers; however, four of the 16 crewmembers received minor injuries. According to the flight crew statements and recorder data, the landing reference speed for the approach was 145 knots. Due to the weather conditions, the flight crew added 10 knots to this for their approach speed due to the gusty weather conditions and conducted a visual approach using the visual approach slope indicator as guidance. As a result of the weather and gusty winds, airspeed fluctuated during the approach between 162 knots and 138 knots and engine thrust varied accordingly between about 86% N1 and 40% N1 on approach. The captain stated that the flight was on speed and glide path at 500 feet above the ground but at about 200 feet above the ground, the flight started to move above the glide path and airspeed started to increase. To compensate, the captain reduced engine power and then heard a "sink rate" aural alert when passing through about 50 feet. Flight recorder data indicated the engine N1 decreased to 40%, with throttles at forward idle position, at about 110 feet above the ground, and remained there until after touchdown. The airplane touched down at 140 knots and a nose up pitch attitude of 8.9 °, increasing to 9.5° immediately after touchdown. Guidance included in the operator's training manuals indicated that normal touchdown attitude should be between 4 and 6 degrees nose up. Additionally, guidance indicated that thrust should be managed on approach to maintain reference speed, plus any wind additive, until the beginning of the flare. After reaching the flare, thrust levers should be retarded smoothly to idle with main gear touchdown ideally occurring simultaneously with thrust levers reaching idle. An analysis of calculated vertical and horizontal wind effect indicated an existing updraft transitioned to a downdraft and a headwind component transitioned to a tailwind component during the last 5 seconds prior to touchdown.