14 CFR §142.57

1. (a)An applicant for, or holder of, a training center certificate must ensure that each aircraft used for flight instruction and solo flights meets the following requirements:
   1. (1)Except for flight instruction and solo flights in a curriculum for agricultural aircraft operations, external load operations, and similar aerial work operations, the aircraft must have an FAA standard airworthiness certificate or a foreign equivalent of an FAA standard airworthiness certificate, acceptable to the Administrator.
   2. (2)The aircraft must be maintained and inspected in accordance with—
      1. (i)The requirements of part 91, subpart E, of this chapter; and
      2. (ii)An approved program for maintenance and inspection.
   3. (3)The aircraft must be equipped as provided in the training specifications for the approved course for which it is used.
2. (b)Except as provided in paragraph (c) of this section, an applicant for, or holder of, a training center certificate must ensure that each aircraft used for flight instruction is at least a two-place aircraft with engine power controls and flight controls that are easily reached and that operate in a conventional manner from both pilot stations.
3. (c)Aircraft with controls such as nose-wheel steering, switches, fuel selectors, and engine air flow controls that are not easily reached and operated in a conventional manner by both pilots may be used for flight instruction if the certificate holder determines that the flight instruction can be conducted in a safe manner considering the location of controls and their nonconventional operation, or both.