14 CFR § 23.2305

The landing gear must be designed to—

Provide stable support and control to the airplane during surface operation; and

Account for likely system failures and likely operation environments (including anticipated limitation exceedances and emergency procedures).

All airplanes must have a reliable means of stopping the airplane with sufficient kinetic energy absorption to account for landing. Airplanes that are required to demonstrate aborted takeoff capability must account for this additional kinetic energy.

For airplanes that have a system that actuates the landing gear, there is—

A positive means to keep the landing gear in the landing position; and

An alternative means available to bring the landing gear in the landing position when a non-deployed system position would be a hazard.