Monday, May 5, 2014

Air data computer open project starts

Every Basic Air Data instrument needs some electronic part to be fully functional. Implementations for stand alone instruments have been shown on the BAD main web site. When all the electronics needed for the operation of different sensors is collected into a single unit we name it Air Data Computer

This time we're facing the design of an Air Data Computer or ADC. The development process will take place on the brand new BasicAirData forum, this post introduces the preliminary requirements for ADC. Some work has been already done, have a look to the following figure. 

Figure P44. Some preliminary virtual prototype and an example commercial air data computer

Within this project we will develop an Air Data Computer that can manage one Pitot-static probe, one barometer and one temperature sensor; the following measurements will be available. 

-Static pressure, Pa
-Differential pressure, Pa
-Outside air temperature, Degree Kelvin
After sensor data fusion the unit will provide the followings data through a serial link.
-Indicated airspeed IAS, m/s
-True airspeed TAS, m/s
-Outside air temperature, °K/°C 

The separate implementation of every function is more expensive than monolithic approach. Main advantage is that since all the necessary electronics is located in the same place it is easier to remove or install the equipment. As standard pneumatic and data link connection are provided then also placement on different airframes is fast and somewhat standardized.

ADC features list.

-Reduced dimensions and weight, so the unit can be fitted into middle/smalls UAS. Let's say about 50x20x20mm and 20g.
-Able to withstand high G-loads, more than 8
-3.3V Hardware with on board voltage regulator
-Standard pneumatic connection
-Standard serial connection
-On board sensor data processing
-Static pressure accuracy better than "0,5 meter". Maximum IAS airspeed below 300 km/h; accuracy at full scale 1% or better.
-Temperature accuracy about 0.5°C.
-Broadly available components
-Low part count and few soldering work
-Easy to make and assemble 

Stated accuracy is intended without the use of any sensor calibration procedure.
Open design is starting right now, for further reference go to BasicAirData Forum.
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