Tail strike, Boeing B737-838, VH-VXH

On 1 February 2005, a Boeing Company 737-838 (737) was being operated on a scheduled passenger service from Sydney, NSW, to Darwin, NT with two pilots, five cabin crew and 151 passengers. The pilot in command (PIC) was the pilot flying for the take-off. At 1931 Eastern Daylight-saving Time, during lift-off from runway 34 Left (34L), in gusty crosswind conditions, the PIC and copilot felt the aircraft’s tail strike the runway. They queried the rear cabin crew, who confirmed that there was an unusual noise during the aircraft’s rotation. The pilots performed the 737 Quick Reference Handbook (QRH) Non-Normal Checklist for tail strike on take-off. Following completion of the checklist, the PIC elected to return to Sydney for an overweight landing. An engineering inspection confirmed that the aircraft had sustained a tail strike during the take-off. A crushable cartridge, fitted to minimise damage to the aircraft during a tail strike, was damaged and required replacement.

The investigation found that while the PIC needed to react quickly and precisely to manage roll in the gusty crosswind conditions, a more measured input of pitch control was required during the aircraft’s rotation to maintain the allowable tail clearance margin. This occurrence highlights that during a take-off manoeuvre, tail clearance margins can reduce to the point where a tail strike will probably occur if the recommended rotation rate is exceeded.

On the 25 January 2006, the operator advised the Australian Transport Safety Bureau they had developed a New Technologies training segment effective 18 January 2006. That training includes the use of the Heading Guidance System (HGS) on the Boeing 737 which will enhance situational awareness during takeoff and landing.

On 1 February 2005, a Boeing Company 737-838 (737) was being operated on a scheduled passenger service from Sydney, NSW, to Darwin, NT with two pilots, five cabin crew and 151 passengers. The pilot in command (PIC) was the pilot flying for the take-off. At 1931 Eastern Daylight-saving Time, during lift-off from runway 34 Left (34L), in gusty crosswind conditions, the PIC and co-pilot felt the aircraft's tail strike the runway. They queried the rear cabin crew, who confirmed that there was an unusual noise during the aircraft's rotation. The pilots performed the 737 Quick Reference Handbook (QRH) Non-Normal Checklist for tail strike on take-off. Following completion of the checklist, the PIC elected to return to Sydney for an overweight landing.

An engineering inspection confirmed that the aircraft had sustained a tail strike during the takeoff. A crushable cartridge, fitted to minimise damage to the aircraft during a tail strike, was damaged and required replacement. There was also minor wear to the tailskid shoe. A structural inspection of the tail section and an overweight landing check were completed and the aircraft was found to be serviceable.

The Sydney Airport automatic terminal information service (ATIS) provided meteorological and operational information for pilots of arriving and departing aircraft by means of a continuous and repetitive radio broadcast. The information broadcast at the time advised that runway 07 was in use, the wind direction was 030 degrees M at a speed of 20 kts and gusting to 30 kts. The maximum crosswind was 18 kts [for aircraft operating on runway 07]. Those conditions would have resulted in a crosswind of 16 kts to 23 kts for runway 34L.

The Bureau of Meteorology provided a report of the weather conditions at 1930 as recorded by the automatic weather station at Sydney Airport. The report indicated that there was a north-easterly wind (from 050 degrees T), with a speed of 25 kts and gusting to 35 kts. That resulted in a right crosswind of 22 kts (mean) and up to 31 kts during a gust, for aircraft operating on runway 34L.

The aircraft's weight and balance sheet provided to the pilots by the operator showed that the planned take-off weight was 75,689 kg¹. That resulted in a calculated take-off decision speed (V1) of 150 kts indicated airspeed² (IAS), a rotation speed (Vr) of 151 kts IAS and a take-off safety speed (V2) of 156 kts IAS. The PIC reported that after assessing the performance requirements for take-off, he elected to use runway 34L. The operator's crosswind limit for runway 34L was 33 kts.

The aircraft was fitted with an L3 Communications digital flight data recorder (DFDR). The ATSB analysed the recorded DFDR data to assist in establishing the sequence of events during the occurrence. During the take-off roll, control wheel (right) and rudder (left) inputs were made consistent with a right crosswind. The analysis showed that during the take-off roll the PIC used quick and precise roll control inputs in the gusty crosswind conditions. Fluctuations in the aircraft's calibrated airspeed (CAS) showed that variable wind conditions were experienced during the take-off roll, consistent with the ATIS values. The aircraft was rotated at the calculated Vr of 151 kts IAS. At lift-off, the aircraft's pitch attitude was +10.9 degrees³. By comparison, the average pitch attitude for the 23 previous takeoffs was +5.5 degrees. The average pitch rate of rotation was 3.7 degrees per second, compared with an average pitch rate of rotation of 2.2 degrees per second for the 23 previous flights. The data revealed that immediately prior to rotation, the aircraft was tracking on the runway centreline and the wings were level.

The operator's 737 Flight Crew Training Manual section 3.9 stated that, 'a 2 to 3 degree per second rotation rate is required to achieve a tail clearance of 51 cm'. Section 3.14 states that under gusty wind and strong crosswind conditions, 'do not rotate early or use a higher than normal rotation rate in an attempt to clear the ground and reduce the gust effect because this reduces the tail clearance margins'.

Actual brakes release weight at the start of the take-off run.
Indicated airspeed is the reading of the airspeed indicator instrument.
The pitch attitude mentioned is consistent, allowing for resolution limits, with the Boeing Flight Crew Training Manual (FCTM) tail strike pitch attitude (11.0 degrees).

The operator’s 737 manual provided information on the handling techniques to maintain tail clearance margins during take-off, including take-off in gusty and crosswind conditions.

While the pilot in command (PIC) needed to react quickly and precisely to manage roll in the gusty crosswind conditions, a more measured input of pitch control was required during the aircraft’s rotation to maintain the allowable tail clearance margin. The almost doubling of the average pitch rate of rotation during the take-off indicates that the PIC exceeded the recommended rate. It is possible that the PIC used a similar style of control input for pitch that he was using to manage roll.

This occurrence highlights the fact that during a take-off manoeuvre, tail clearance margins can reduce to the point where a tail strike will probably occur if the recommended rotation rate is exceeded.

Operator

On 25 January 2006, the operator advised the Australian Transport Safety Bureau that:

The training department has developed a New Technologies training segment effective 18 January 2006. That training includes the use of the Head-up Guidance System (HGS) on the Boeing 737 which will enhance situational awareness during take-off and landing.