Other systems in the Q400 that are affected that rely on the radio altimeter are the configuration systems (warnings for incorrect gear or flap settings), our TCAS system (traffic collision avoidance system) could give us a command to “descend” at low altitude where previously this would be inhibited, and of greater concern is that the stall protection equipment, which includes the stick pusher, could activate at low altitude when it is normally inhibited by the radio altimeter. I have spoken with other pilots and on the Embraer E175 the autoland system will not be available in addition to similar TCAS warnings, configuration warnings and autothrottle issues. Although I cannot comment for sure, I have heard that Airbus aircraft rely on the radio altimeter for many functions and will be more affected than Boeing.
What is the general feeling of the crews about all this? It seems like the last minute and a lot of uncertainty for something that’s been happening for a very, very long time.
Uncertainty is the word that best describes it. Those of us who haven’t planned to fly the 18 are happy because we honestly don’t know what’s going to happen from a cockpit perspective. We understand the operational aspects (i.e. canceled flights and diversions) but as far as the reaction of the aircraft is concerned, we have only received superficial indications.
It’s not the fault of the operator or even the aircraft builder, he was thrown into our lap with very little warning and we’re doing the best we can with him. Lots of communication from management which is good they are aware of the issue and are working on the best way to fix it but at the end of the day we are not sure exactly how each guy is doing of plane. to respond to incorrect radio altimeter readings. Safety is definitely at the forefront of everyone’s mind.
What about attenuation? What do you mean in terms of how these issues will actually be resolved? It looks like it could get expensive in the long run.
The only mitigation we have is after something happens. It is not known if these interferences will be constant and will always occur in the same way, at the same airport, at the same place on approach or if they will be random. It is this unpredictability that is worrying.
We have been informed of the authorized approaches and, as I said earlier, it is very restrictive. For any airport with an active 5G NOTAM, we are not allowed to fly SA CAT 1, SA CAT 2, CAT 2 or CAT 3 and if it is also mentioned that it affects RNP (Required Navigation Performance) approaches those- these are also unavailable.