135.153—Ground proximity warning system.
(a)
No person may operate a turbine-powered airplane having a passenger seat configuration of 10 seats or more, excluding any pilot seat, unless it is equipped with an approved ground proximity warning system.
(d)
No person may deactivate a system required by this section except under procedures in the Airplane Flight Manual.
(e)
Whenever a system required by this section is deactivated, an entry shall be made in the airplane maintenance record that includes the date and time of deactivation.