Lufthansa A333 at Chicago on Mar 5th 2013, undetected tailstrike on takeoff
Last Update: December 16, 2016 / 14:40:41 GMT/Zulu time
The aircraft was removed from service after landing, the aircraft received substantial structural damage. Following initial repairs the aircraft was ferried from Munich to Hamburg Fuhlsbüttel (Germany) as flight LH-9926 on Mar 16th reaching a maximum cruise level of 080.
Germany's BFU confirmed they have been informed about the occurrence, an investigation has been opened, further details are not yet to be disclosed however.
On Mar 12th 2013 the French BEA reported the aircraft suffered a tail strike on takeoff, Germany's BFU is investigating the occurrence initially assessed as a serious incident.
In May 2013 the BFU reported in their monthly bulletin, that the investigation has been delegated to the BFU by the NTSB, the occurrence was rated an accident.
The BFU reported that the first officer (39, ATPL, 9,332 hours total, 5,431 hours on type) was pilot flying during the departure, the captain (57, ATPL, 17,693 hours total, 2,729 hours on type) was pilot monitoring, when the aircraft departed runway 32R and the tail contacted the runway surface. A flight attendant reported unusual noise from the tail shortly after departure, the third pilot in the cockpit (36, ATPL, 8,697 hours total, 4,186 hours on type) received the information. After consultation amongst the crew and with dispatch it was decided to continue the flight to Munich, the cockpit crew had not noticed anything unusual during departure.
The aircraft received substantial damage, besides visible abrasion damage to the skin there were deformations of four support beams carrying the floor of the aft cargo bay, a number of the joints between inner structure and skin were severed.
On Dec 15th 2016 the BFU released their final report concluding the probable cause of the tail strike was:
The BFU is of the opinion that the tailstrike was caused by a reduction of tail clearance due to the following factors:
- Flaps configuration
- Rotation rate dynamic
- Position of centre of gravity and pitch trim
- Reduced rebound of the main landing gear shock absorbers
It is to be pointed out that the concurrence of these factors resulted in the tailstrike. The complete system would have tolerated each individual factor by itself.
The BFU reported according to FDR the maximum rate of rotation was 4.2 degrees/s, while the usual rate would be 2-3 degrees/s, the rotation began at the computed Vr of 150 KIAS. The pitch angle increased to 11.5 degrees nose up, a peak of +1.18G was recorded, the pitch angle reduced a bit and the pitch rate slowed to 2.8 degrees/s. About one second later at 164 KIAS the main gear departed the runway surface at a pitch angle of 13.5 degrees nose up.
The BFU reported that the computer takeoff mass was 227 tons, with the CG at 22.87% MAC (permitted range 18 to 39%), the flight data recorder showed the gross takeoff mass was 225,435kg just prior to takeoff with the CG at 23.4% and trim position at 6.1 degrees nose up (permitted range 0-7 degrees).
The crew had chosen to select the flaps to 1+F considering that the snow slush and ice could raise their flaps, while the takeoff performance software recommended F2 position for the flaps for takeoff. The risk of a tailstrike decreases with a higher flap setting, the BFU annotated.
Following the flight, on Mar 6th 2013, the shock absorbers were checked and found to extend 237mm on the left hand gear strut and 240mm on the right hand gear strut, required however were 305mm plus/minus 15mm (290-320mm). The shock absorbers were refilled with Nitrogen and then extended 305mm on the left and 307mm on the right gear strut.
The BFU reported the aircraft manufacturer analysed the wind data recorded by the FDR and found, that at the time of rotation the aircraft was exposed to a downdraft gradient of 6 knots in 2.5 seconds and a tail wind gradient of 6 knots in 5 seconds. The manufacturer wrote: "The upshot of the wind estimation is a lift reduction during rotation.".
The BFU analysed:
The damages on the tail section of the airplane could be associated to the tailstrike. The area of the pressurised cabin was damaged but not degraded in its stability. There was no pressure loss during the flight. After the landing the airplane was visually inspected and the extent of the damages determined. The manufacturer confirmed the damages and only agreed to the ferry flight with unpressurised cabin and minimal crew after makeshift repairs of the fuselage. Due to the severity of the damages the occurrence was classified as accident.
This tailstrike accident occurred about one second prior to the main landing gear lifting off completely from the runway and the air-ground-switch being triggered. The ground impact was very brief and like a strike.
The energy of the strike was transported by struts and cross beams to the cabin floor of the aft galley where the flight attendants were seated.
Due to the airplane’s length the cockpit was far away from the place of ground contact. Therefore the cockpit crew could not determine the tailstrike. ...
The BFU does understand why the flight crew decided to use a lower configuration thus avoiding that the extended lift surfaces were hit by runway contamination. Due to weather and runway conditions it was highly likely that the lift surfaces and engines of the airplane would be hit by snow slush.
Both shock absorbers lacked gas and gas pressure so that the required rebound was not met. This resulted in decreased tail clearance.
KORD 060551Z COR 34013KT 10SM BKN012 OVC025 M01/M03 A2995 RMK AO2 SNE19 SLP150 4/010 P0000 60012 T10111033 10000 21011 400061017 51021 $
KORD 060451Z 35014KT 6SM -SN BR OVC012 M01/M03 A2994 RMK AO2 SNB02 SLP145 P0000 T10111028 $
KORD 060427Z 36012KT 2SM -SN BLSN BR OVC012 M01/M02 A2993 RMK AO2 SNB02 P0000 $
KORD 060351Z 35014KT 6SM BLSN BR BKN012 OVC018 00/M02 A2991 RMK AO2 SNE34 SLP136 P0001 T00001022 $
KORD 060323Z 01016G21KT 5SM -SN BLSN BR BKN012 OVC021 00/M02 A2990 RMK AO2 P0001 $
KORD 060251Z 01012KT 1 1/2SM -SN BLSN BR BKN011 OVC021 M01/M02 A2989 RMK AO2 SLP129 P0001 60011 T10061017 53016 $
KORD 060229Z 02013G20KT 1 3/4SM -SN BR BKN011 OVC021 M01/M02 A2989 RMK AO2 P0001 $
KORD 060203Z 02015G25KT 1SM R14R/P6000FT -SN BLSN BR SCT009 BKN013 OVC021 M01/M02 A2987 RMK AO2 P0000 $
KORD 060203Z COR 02015G25KT 1SM R14R/P6000FT -SN BLSN BR BKN011 OVC021 M01/M02 A2987 RMK AO2 P0000 $
KORD 060151Z 02011G18KT 1SM R14R/P6000FT -SN BLSN BR BKN009 OVC014 M01/M02 A2987 RMK AO2 SLP122 P0006 T10111017 $
KORD 060111Z 02013KT 1SM R14R/P6000FT -SN BR BKN009 OVC014 M01/M02 A2986 RMK AO2 P0002 $
KORD 060051Z 02011KT 3/4SM R14R/5000VP6000FT -SN BR BKN007 OVC011 M01/M02 A2986 RMK AO2 SLP118 SNINCR 1/10 P0004 T10111022 $
KORD 052351Z 03011KT 1/2SM R14R/5000VP6000FT SN FZFG OVC007 M02/M02 A2984 RMK AO2 SLP113 SNINCR 1/9 4/009 P0005 60036 T10171022 11006 21017 53018 $
KORD 052251Z 04011KT 1/2SM R14R/2600V3000FT SN FZFG OVC007 M02/M02 A2982 RMK AO2 SLP104 SNINCR 1/8 P0006 T10171022 $
This article is published under license from Avherald.com. © of text by Avherald.com.
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