Method for defining a touch-down power for head having a flying height actuator

A method for defining a touch-down power for a head that has a head-based flying height actuator, the head including a transducer to read data from a disk, the method comprising:

• determining a first spacing between the transducer and the disk when a first electrical power is applied to the flying height actuator;
• determining a second spacing between the transducer and the disk when a second electrical power is applied to the flying height actuator, the second electrical power larger than the first electrical power;
• deriving a linear relationship between power and spacing, the linear relationship fit to the first electrical power, the first spacing, the second electrical power, and the second spacing;
• determining a third spacing between the transducer and the disk when a third electrical power is applied to the flying height actuator, the third electrical power larger than the second electrical power;
• calculating an estimated third spacing between the transducer and the disk corresponding to application of the third electrical power to the flying height actuator, the estimated third spacing calculated using the derived linear relationship and the third electrical power;
• and
• defining the touch-down power to be substantially equal to the second electrical power if a first condition is satisfied, the first condition being satisfied if an error between the third spacing and the estimated third spacing is larger than a first threshold.