Question - Decreasing TAS at Height, benefit?
A colleague of mine and I were discussing some aspects of principles of flight (pre-type rating course)and we both got stumped on something. We are both frozen atpls so please be gentle on our knowledge.
As you complete a long distance flight and the aircraft lightens due to fuel burn, you gradually increase flight levels. If you are cruising at a constant M0.79, assuming ever decreasing temperature with increased height, your TAS will be decreasing, at least up to the tropopause. If this is the case, as you get higher you are in fact flying slower due to the temperature decrease, while maintaining .79. Now the STUPID question. Is the advantage the increased efficiency of the engine?? Why doesn't the increased TAS slightly lower outweigh the gain of the higher FL? I completed my theory 4 years ago, and cannot remember. Sat here scratching my bald head.
Why fly higher and accept reduces TAS?????