A method (601; 801) comprising: receiving a first sensor signal from a first aircraft sensor of a rotorcraft, the first sensor signal including raw airspeed values of the rotorcraft; receiving a second sensor signal from a second aircraft sensor of the rotorcraft, the second aircraft sensor being different from the first aircraft sensor; measuring a first speed of the rotorcraft, the first speed being groundspeed of the rotorcraft or raw airspeed of the rotorcraft, the groundspeed of the rotorcraft measured by a GPS, a VHF Omnidirectional Range sensor, or the like; determining airspeed values of the rotorcraft, the determining comprising: using the raw airspeed values in the first sensor signal as the determined airspeed values in response to the first speed of the rotorcraft being less than or equal to a predetermined value; and estimating the determined airspeed values in response to the first speed of the rotorcraft being greater than the predetermined value, the estimating comprising: combining the first sensor signal and the second sensor signal with a complementary filter to determine estimated airspeed values; and using the estimated airspeed values as the determined airspeed values; and adjusting (609; 809) flight control devices of the rotorcraft according to the determined airspeed values. receiving a first sensor signal from a first aircraft sensor of a rotorcraft, the first sensor signal including raw airspeed values of the rotorcraft; receiving a second sensor signal from a second aircraft sensor of the rotorcraft, the second aircraft sensor being different from the first aircraft sensor; measuring a first speed of the rotorcraft, the first speed being groundspeed of the rotorcraft or raw airspeed of the rotorcraft, the groundspeed of the rotorcraft measured by a GPS, a VHF Omnidirectional Range sensor, or the like; determining airspeed values of the rotorcraft, the determining comprising: using the raw airspeed values in the first sensor signal as the determined airspeed values in response to the first speed of the rotorcraft being less than or equal to a predetermined value; and estimating the determined airspeed values in response to the first speed of the rotorcraft being greater than the predetermined value, the estimating comprising: combining the first sensor signal and the second sensor signal with a complementary filter to determine estimated airspeed values; and using the estimated airspeed values as the determined airspeed values; and using the raw airspeed values in the first sensor signal as the determined airspeed values in response to the first speed of the rotorcraft being less than or equal to a predetermined value; and estimating the determined airspeed values in response to the first speed of the rotorcraft being greater than the predetermined value, the estimating comprising: combining the first sensor signal and the second sensor signal with a complementary filter to determine estimated airspeed values; and using the estimated airspeed values as the determined airspeed values; and combining the first sensor signal and the second sensor signal with a complementary filter to determine estimated airspeed values; and using the estimated airspeed values as the determined airspeed values; and adjusting (609; 809) flight control devices of the rotorcraft according to the determined airspeed values. <EOS>