Tail Strike

Typical tail clearance during takeoff is between 50 and 75 cm / 20 and 30 inches. This clearance increases with flap setting. Consider using Flaps 15 for takeoff with low gross weight.

Subtract about 2 degrees from the table values to get landing tail strike pitch (wings level - gear struts compressed).
Takeoff Tail Strike Pitch -800 : 11.0 degrees

Typical factors contributing to a tailstrike are :

On Takeoff

• Rotation at improper airspeed
  (error in takeoff perf computation, rotating before VR, etc)
• Mistrimmed Stabilizer
  (error in converting loadsheet c.g. to stab trim, trim not set, etc)
• Excessive rotation rate
  (initial operating experience, using trim too early, etc)
• Improper use of Flight Director
  (do not use the F/D for rotation !)

The loadsheet is handed-over to the crew at a moment of high workload on the flight deck. Always crosscheck all FMC weight and speed entries, takeoff performance computations and trim setting. Never expedite or skip proper weight and speed verifications in an attempt to make the flight schedule !

On Landing

• Unstabilized approach
  (not initiating a go-around when not stable at 500 feet, fatigue, etc)
• Holding-off in the flare
  (preoccupation with achieving a kiss landing, trimming in flare, etc)
• Mishandling crosswinds and/or tailwind
  (high descent rate, turbulence, windshear, etc)
• Over-rotation during low height go-around
  (maintain actual body attitude until engines have spooled up, especially when go-around is initiated below 50 feet !)
• Too low approach speed
  (if VREF shows within the amber minimum maneuvering speed bar, an incorrect ZFW or Gross Weight may have been entered in the FMC! Verify the loadsheet numbers and increase VREF to remain above the amber bar.)

There is nothing wrong with a go-around even if this go-around is due to an unstabilized approach. But there is definitely something wrong with a tailstrike or a runway overrun!

Post FLT
AMM 05-51 - Even if there is no apparent damage, each tail strike event requires maintenance inspection.

For more information, refer to
FCTM 3.x [Takeoff Tail Clearance]
FCTM 6.x [Body Clearance at Touchdown]
FCTM 8.x [Tail Strike]