MGL Avionics User Forum

I have a pitot / static and transponder test scheduled with Mapoles Aviation at J-22 airport in Florida on Tuesday 28 June. Please provide or direct us to a simplified checklist for tests which will meet 91.227 (ADS-B Performance) 91.411 (Altitude Reporting Equipment Tests) and 91.413 Transponder Test. The equipment is as follows:

Discovery Lite S/N iDL190700302

TT22 S/N: 11432 with MGL interface to Discovery Lite

SP12 S/N: 10-20-02-F-0050

I understand that the Discovery Lite will not register an airspeed until at least 27MPH and that a 105mm water column pressure should provide an airspeed of 90MPH (Approx 78Kts). Do we need this airspeed pressure to test the Transponder / ADS-B for accurate readings?

The tests are prescribed in the references you quote.
We calibrate the ASI sensor at 105mm H2O as that is about the best pressure to calibrate the sensor at considering the pressure range. The sensors themselves are extremely linear (typically within 1% over the range or better). Note that the sensor should be zeroed once in a while to cancel out effects of aging. Also right after installation it should be done as the sensor itself is affected by mechanical pressure and even gravity to a small extent.

In practice - in most cases zero the sensor after first installation and then again a year later - that usually is the last time you do this but since it is quick and easy to do it's perhaps not a bad idea to do this whenever you perform maintenance on your aircraft.

Note: Transponder related checks do not assume that your airspeed sensor can correct for position errors so please remove any user calibration (the speed related ASI calibrations) before the test or else you will fail.

For altitude there is usually no issue - you can move the calibration by adding an offset (see your altimeter calibration in your sensor setup). There will be an offset number that was put in at the factory for sea level. As the sensor ages you may need to increase or decrease that number slightly to get the readings back in line.

A pitot/static test set will be used as reference for all tests. Ensure your AMO can produce a current calibration certificate for the equipment - nothing is worse than forcing your EFIS to an inaccurate calibration because the reference is not accurate.