Tow Hook Release installations on certificated aircraft must be FAA approved in accordance with the appropriate parts of the Federal Aviation Regulations. This approval can be accomplished by any of the following three methods:
- Approved Original Equipment Item: — the aircraft manufacturer designed, tested and received an FAA type approval for the tow hook installation as a part of the approved equipment items for a specific aircraft.
- Supplemental Type Certificate Approval: — one can design, engineer, test and obtain approval of an installation on a specific airplane model under provisions of an FAA supplemental type certificate. This installation can be accomplished on other aircraft of the same model with the approval of the STC holder.
- Major Alteration Approval on FAA Form 337: — FAA FSDO inspectors have the authority to accept individual installations done on a local FAA Form 337 basis. Installations in this case should be accomplished in accordance with the methods, practices and guidelines outlined in FAA advisory circular No. AC43.13-2B, Chapter 8, to afford a reasonable margin of safety. Additional engineering and testing may be required by the individual FAA inspector to substantiate the structural integrity of the installation. The FAA will often accept installations which were previously approved by FAA Form 337 on same model aircraft, provided such installations have been proven in service. Since the procedures and policies on this type of approval vary from one FAA district officer to another, one should discuss the proposed installation with the FAA before proceeding.