FAA AC 20-112:1981
FAA AC 20-112:1981 Airworthiness And Operational Approval Of Airborne Systems To Be Used In Lieu Of A Ground Proximity Warning System(s) (gpws) Gives information and guidance regarding the airworthiness and operational approval equipment/system(s) in accordance with Federal Aviation Regulations (FAR) Section 135.153, paragraphs (b) and (c).