Pilots on a training flight reported a malfunction of the radio altimeters and autothrottles while on approach to MDW. The crew suspected the anomaly was 5G related.
Synopsis
Pilots on a training flight reported a malfunction of the radio altimeters and autothrottles while on approach to MDW. The crew suspected the anomaly was 5G related.
Narrative
We were on right downwind for RWY22R at 1900 MSL on the first of two almost identical flights. As we approached the base turn; I noted an amber R ALT flag in the PFD and the EICAS indicated a cyan 'FGC - A/T Rad Alt Invalid' CAS message. Our GPS track indicates the event occurred approximately above Laramie & 31st St. None of the three of us knew exactly the corrective action from memory; but it was apparent that the autothrottles were affected by a radar altimeter issue. The tower frequency was busy; working us between numerous arrivals and departures. We were coordinating inside the cockpit since I could not see the airport from my position on the left side of the aircraft. Between the long traffic pattern checklist; increased coordination in the cockpit; lots of radio traffic; configuring the airplane; discussing the implications of the CAS message; and tracking numerous targets outside; we were quite busy so we didn't have the opportunity to compare radar altimeter indications. We had briefed the possibility of radar altitude issues stemming from the rollout of 5G services; and we elected to disconnect the autothrottles and continue the approach to a normal landing.While we were aware of the possibility of radar altimetry issues due to the NOTAM at MDW and all of the industry publications as of late; we didn't really expect to have any issues with our operation. With a combined years of [aircraft type] operation between the three of us; we have found the radar altimeters to be supremely reliable; and none of us had seen that CAS message ever displayed prior to this occurrence. We discussed the 5G NOTAM during our preflight brief; but we had assumed (incorrectly) that it would only affect the listed operations. It was certainly a very unwelcome distraction during an especially high workload critical phase of flight.
Second reporter narrative
[Report narrative contained no additional information.]
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.