Dear SFE,
Measuring the angle of attack (alpha) and sideslip angle (beta) is extremely important in radio controlled airplane.
It must not be confused with measuring the pitch or yaw angle as they are quite different (pitch angle = alpha only when the air is calm and stationary, i.e. no winds in any direction at all)
I have searched on Google several times in vain to find such a sensor that is suitable for rc airplane application.
I have found an excellent NACA article online (http://www.spaceagecontrol.com/naca-tn-4351.pdf) which can serve as a starting point for designing such a sensor. It just involves a pitot tube with some extra holes for sensing the angle (see the above naca article), a differential pressure probe and a calibration chart.
As I mentioned in the beginning the measurement of alpha and beta are very important especially when designing a flight control system/ autopilot. Therefore it could be an excellent idea for a new product.
Cheers,
baravi
AoA is important, but arent’ you more interested in rate of climb? For example, given a cargo weight of 200 grams, you might require -0.1 degree angle of attack for level flight, and given 300 grams you might require -0.09 degree angle of attack. Yes, the amounts can be negative for high lift wings to maintain level flight.
Using an altimeter that you sample every second, you know your rate of climb/descent and from that you can know your current angle of attack for a particular airplane. Adn then if you use a gyro to zero out sudden up or down pitches, you are set.
Yes, the rate of climb may be important too…and I guess you can measure with a very sensitive gps unit or some kind of an altimeter.
But I was just saying that there are devices like infrared sensors and gyros/ accelerometers to measure pitch angle so why not the angle of attack sensor since usually, they are not the same and an angle of attack/ side slip sensor are very important parameters in the flight mechanics of an airplane.
One nice feature that you can incorporate with an aoa sensor and a microcontroller is that you can make an airplane stall free. When I was learning to fly rc airplane I used to stall the airplane quite often which can be a dangerous situation. You can prevent this from happening by ignoring the nose up motion caused by any further up elevator when the airplane is near the stalling angle. This can be done if you know what the angle of attack of the airplane is.
This is a feature that is incorporated in some real life aircraft like Airbus that prohibit the pilot from stalling the aircraft in any situation by ignoring the pitch up command from him when the aircraft is close to the stalling angle of attack.
There are many other things that you can do if you know the aoa of the airplane as it bears direct influence on the amount of lift that is generated by the airplane at that instant.
It is indeed an excellent suggestion to obtain the aoa from the rate of climb. The aoa can be calculated indirectly if we know the rate of climb, forward speed and the pitch angle.
I have not thought of this but I think there are other situations like when the aircraft is flying level or there is a sudden gust of wind, etc. when it may not be very simple to obtain the aoa indirectly with the minimum computation and math !
So I think in the end measuring the angle of attack using a vane/ rotary encoder or pitot tube arrangement is a much simpler solution - it will work in any situation.