Effects of Temperature and Altitude.
Cold and/or Low
On cold days the air density will increase. If the engine has a ‘part throttle rating' and the throttle is advanced to its maximum position, the thrust produced will be significantly higher, resulting in the engine exceeding its mechanical and/or thermal limits as set by the manufacturer.
Hot and/or High.
On hot days, when the air density is less, a significant reduction in thrust will result. Advancing the throttle to its maximum condition could again cause the engine to exceed its thermal and /or mechanical limitations.Density of air will also be affected by altitude, although the temperature of air drop (1.97°C per 1000ft Temperature lapse rate) which should cause an increase in thrust, the density of the air drops at a higher rate due to the drop in pressure so thrust decreases with altitude at a relatively slow rate. When the tropopause is reached at 36,000ft the temperature remains constant and the thrust drops off at a greater rate when climbing. The engine manufacturers graphs and tables will enable the operator to control the engine within safe thermodynamic and mechanical limits. By observing these limits the engine will be protected against unnecessary wear and tear as well as maintaining the recommended time between overhaul periodicity's.