Transport Canada Civil Aviation Safety Alert – Inaccurate airborne status transmitted by transponders

Effectivity: Challenger and Global aircraft  

ATA 34-54 

By: Camelia Constantin and Louis Martel – Technical Services

Following the release of the Transport Canada (TC) Civil Aviation Safety Alert (CASA) No. 2021-03 in December 2021, Bombardier Technical Services was contacted on a few occasions regarding the CASA applicability to Bombardier products. The European Union Aviation Safety Agency (EASA) also posted on their website this TC CASA No. 2021-03 as a Safety Information Bulletin (SIB) in January 2022. As stated in the TC CASA document, the incident involved, during a rejected take-off, an aircraft where the transponder transmitted an airborne status, even though it remained on the runway. The Bombardier Challenger and Global aircraft are not equipped with the same avionics system involved in this event and therefore this TC CASA No. 2021-03 is not applicable.

Despite the fact the TC CASA No. 2021-03 did not list Bombardier manufactured aircraft as affected, operators were asking clarification on the logic that will trigger the airborne status transmitted by the transponder. The CASA recommends that operators should become aware of the airborne status override threshold applicable to their aircraft and provide the information found in this CASA to staff and/or flight crew as a means of awareness. See below table with details per aircraft platform:

 Note that the minimum performance standards for transponders are identified in the Radio Technical Committee for Aeronautics (RTCA) document Minimum Operational Performance Standards (MOPS) for Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne Equipment (DO-181E MOPS). The standards require an override threshold that switches the transponder to airborne mode after 100 knots is reached, regardless of any other sensor input. 

 For more details:  

Transport Canada (TC) Civil Aviation Safety Alert (CASA) No. 2021-03 is available here. 

European Union Aviation Safety Agency (EASA) Safety Information Bulletin (SIB) is available here.