30 CFR § 36.22
This system shall be so constructed that the quantity of fuel injected can be
controlled at a desired maximum value and shall be so arranged that this
adjustment can be changed only after breaking a seal or unlocking a
compartment. Provision shall be made for convenient adjustment of the maximum
fuel-injection rate to that required for safe operation at different
altitudes (elevations above sea level). The governor, controlling engine
speed and fuel injection, shall not directly affect airflow to the engine
and provision shall be made to seal or lock its adjustment compartment.
Filters shall be provided to insure that only clean fuel will reach the
injection pump or injectors.