Figure 10.40. Takeoff thrust for a turboprop engine

(EPR) at the jet pipe temperature (JPT), which should remain lower than prescribed levels. An engine is identified at its sea-level STD day at takeoff in static conditions. For turbofans, it is denoted as TSLS. Typical power settings (i.e., ratings) of engines are given in the following subsections.

Takeoff Rating

This is the highest rating that produces the maximum power and is rated at 100% (i.e., at static run of turbofans, it is TSLS). At this rating, the engine runs the hottest and therefore has a time limit to ensure a longer life and less maintenance. For civilaircraft engines, the limit is about 10 minutes; for military aircraft engines, it could extend somewhat longer. A situation may arise in which one engine is inoperative and the operative engine must supply more power at the augmented power rating (APR). Not all engines have an APR, which exceeds 100% power by ≈5% for a short duration (e.g., ≈5 minutes).

Maximum Continuous Rating

This is the highest engine rating that can operate continuously at approximately 90 to 95% of the maximum power. It is more than what is required for climbing at a good fuel economy. Operational demand in this rating arises from specific situations – for example, a very fast climb to altitude (mainly in military use). Typically, a climb is accomplished at around 85% power to reduce stress on the engine and to achieve better fuel economy. For this reason, the maximum continuous rating is not included with some engines and rather is merged with the maximum climb rating.

Maximum Climb Rating

The climb schedule is accomplished at approximately 85 to 90% of the maximum power. A typical climbing time for a civil aircraft is less than 30 to 40 minutes, but it can run continuously.