Above are the lecture notes for my aircraft performance course. If you are serious about developing an airframe then I would recommend you read through these, its all very useful and interesting. They're notes written to prepare a future aeronautical engineer!
they basically cover calculating and predicting (for different altitudes, payloads and drag coefficients):
- rate of climb
- service cieling
- finding optimum and economic flight regimes
- takeoff, ascent, cruise, descent, and landing performance
- turning performance
And just some interesting stuff really. You may think that varying altitudes are irrelevant to DIY UAV's, however hotter or colder conditions affect density as much as altitude does (changes in density are quite influential on an aircraft).
A very interesting and easy to miss part is the solution to question 3 of section 5.
It basically describes how to experimentally determine your drag coefficients
That is, as long as you have a way of measuring:
- shaft power ( Power [W] = torque being produced by motor [Nm] x RPM [rad/s] )
- your propeller efficiency
- airspeed ( using a pitot static tube, GPS speed is NNNOOOOTTT good enough)
- the aircrafts weight (the only easy one :])
- density ( density [kg/m^3] = pressure [Pa]/ ( 237 x temperature [K] ) )
If you do look through these notes, please note that at least half of the solutions to the examples have numerical errors somewhere, but their
methods all hold true! Also there is some stuff about Mach numbers which you can definitley ignore, I don't think any DIY UAV will ever be even near Mach 0.7+