Geez, I should know this...

[CAFedm]

This is a general aircraft question, but being that I am testing an FS-designed aircraft in a similar manner, thought to post here for a response. If wrong, please feel free to move it.

I was taking in an article on the F-15A Streak Eagle (that makes for some interesting reading BTW!). Time-to-climb was discussed among other things, including the fact that the aircraft had no paint or radar to reduce weight, ran on fumes, and had to fly on a very cold day while adhering to a precise flight profile, in order to obtain the results that it did. Still impressive, nonetheless. Anyway, my question is regarding the definition of climb rate. Time-to-climb was discussed both in this article and another relating to the EE Lightining, with the latter claiming the highest climb rate until the advent of the Su-27 & MiG-29. The Lightning's time-to-climb was reported to be 2.5 minutes from brakes off to 36,000 feet, at full afterburner, and was described as being nearly similar to the Eagle in this aspect of performance. It's initial rate of climb was described as being 50,000 ft/min, which of course is not anywhere the same as the previous figure. I cannot find any proper definition of how an aircraft's initial rate of climb is calculated. If anyone can clue me in to how these figures are determined, I would appreciate the info.

...For the flightsim part of this, the design I tested made it to 36,000 ft in 70 seconds from brakes off, in standard (59 degree F) temps. Don't think it did too badly!

[Brett_Henderson]

Interesting stuff. In simplest terms, the rate-of-climb is a self-calculation; feet climbed divided by minutes  :P

I'm not sure what you mean by calculating the initial rate-of-climb. I'm guessing, that if you plotted altitude vs time; it would be the first (most likely steepest) part of that graph.

I do remember enough about that nasty calculus stuff, and its elusive, exact rates of change... that any change can have a theoretically, infinite rate  ::)

As far as testing and then trying to match real-world performance in the sim; it's all a matter of how much tuning you're up to trying.

Static thrust, thrust scalar, parasitic drag and induced drag are things to tinker with..  but to get a TRUELY accurate profile, you'll probably have to employ a set of invisible flaps controlled by an XML, speed and altitude referencing gauge. These flaps, with their pitch, drag and lift scalars (which can be negative numbers), being deployed to different degrees, under different speed/altitude parameters can "force" a plane to perform realistically.

[CAFedm]

Thanks for the info. It would seem to be a that things are not necessarily as straightforward (or uncomplicated!) as they might at first appear. As far as Streak Eagle flights go, it might make for an interesting addon mission in FSX.

[pepper_airborne]

I think so too, you could put it in a graph i think with a formula similair to this:

It would be close to something like max climb(initial climb)*0.99(any number below 0) to a power of T.

Climb=IC*Decrease^Time