CS 25.1549 Powerplant instruments

1 Powerplant instrument range markings are intended to indicate to flight crew members, at a glance, that the powerplant operation is being accomplished in a safe or desirable, undesirable but allowable, or unsafe region. The colour red indicates an unsafe condition which requires immediate and precise action by the flight crew. The use of multiple red lines should be avoided to minimise confusion. 2 A precautionary range is a range where limited operation is permissible, as indicated in the aeroplane Flight Manual. Experience has shown that to satisfy the requirement for clearly visible markings, the following minimum dimensions should be observed. a. Red, yellow and green lines. 1.3 mm (0·05 inch) wide and 7.6 mm (0·3 inch) long. b. Red, yellow and green arcs and areas. 2.5 mm (0·1 inch) wide, length as required.