I hope you enjoyed my recent introduction into maximizing climb specific range, which I consider one of the most important topics when discussing flight efficiency. In recognition of all the “numbers” folks out there, this article will continue to discuss a few performance topics very rarely considered: how to maximize your climb specific range based on winds, temps, and takeoff weight. Please take a look at this short video to hear more about Climb Specific Range from me as well.
I have written my own loads and performance code for over 20 years, gaining valuable comprehension of all numbers in all tables in the AFM, OM, POH, etc. (We were required to reproduce all that for our active winglet modification, so I even adapted my own code for the 525s.) This type of deep understanding is very different than plugging in a city pair into fltplan.com. The truth is, I prefer to talk airplanes with the true “numbers” folks out there - and as a pilot and aerospace engineer specializing in flight loads, aerodynamics, and performance, I am the definition of a “numbers” guy.
The thoughtful pilot does not always rely on the “set it and forget it” mode, but rather commits to calculating and flying the ideal profile for maximum efficiency. The “cruise climb” 220/.57-type climb requires a higher level of focus, while some 525s entail an even stricter OEM recommended “Best ROC” airspeed schedule. However, none of these methods consider the wind and temps during climb, so flying the ideal profile means an extremely focused, active, and responsive cockpit - but I personally love that activity during a climb.
Finding our ideal climb profile takes some serious math and equation crunching. We know from basic performance equations that the sine of the climb gradient is (T-D)/W.
Here is the partial breakdown of some of the variables that make this fun, but definitely complicated:
- T = Thrust is a function of Altitude, Mach and RAT and Throttle Setting.
- D = Drag is the addition of form drag and induced drag, which depends on lift, airspeed, etc.
- RAT is a function of altitude and KIAS.
- Mach is a function of TAS and temperature.
- Altitude is a function of TAS and climb gradient.
- W = Weight is dependent on fuel flow.
- Ground speed is dependent on TAS and winds.
If we know the predicted winds and temps along the climb route and our takeoff weight, we can solve for the ideal profile. This profile will produce an indicated airspeed schedule at every altitude that, if followed, will produce the most efficient climb and level off. In addition, we can maximize our range by going as far as possible using the least amount of fuel we can. Even if we are held down by ATC, we can always optimize what is left of our climb.
If you really want to stretch your legs, or be a real “numbers” person, you may want to consider this concept in your next flight planning profile. Stay tuned for my upcoming eBook, discussing how to reach your CJ’s potential, coming out next month.