StacksVerified U.S. regulatory reference

14 CFR §25.1549

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
For each required powerplant and auxiliary power unit instrument, as appropriate to the type of instrument—
  1. (a)Each maximum and, if applicable, minimum safe operating limit must be marked with a red radial or a red line;
  2. (b)Each normal operating range must be marked with a green arc or green line, not extending beyond the maximum and minimum safe limits;
  3. (c)Each takeoff and precautionary range must be marked with a yellow arc or a yellow line; and
  4. (d)Each engine, auxiliary power unit, or propeller speed range that is restricted because of excessive vibration stresses must be marked with red arcs or red lines.