In an embodiment, a rotorcraft includes: a flight control computer configured to: receive a first sensor signal from a first aircraft sensor of the rotorcraft; receive a second sensor signal from a second aircraft sensor of the rotorcraft, the second aircraft sensor being different from the first aircraft sensor; combine the first sensor signal and the second sensor signal with a complementary filter to determine an estimated vertical speed of the rotorcraft; adjust flight control devices of the rotorcraft according to the estimated vertical speed of the rotorcraft, thereby changing flight characteristics of the rotorcraft; and reset the complementary filter in response to detecting the rotorcraft is grounded.