Is it possible there was an altimeter error on the chopper? And should ATC advise a chopper pilot who is too high?
Possible helo altimeter error? Good point - but these were reportedly experienced pilots who presumably would know they were well over their allowed ceiling.
“Is it possible there was an altimeter error on the chopper?”
I don’t know know if a radar altimeter — which wouldn’t be subject to much error — is in use on a military aircraft when operated in civilian airspace like that.
But regardless, helicopter pilots develop quite a keen sense for altitude above ground even at night (out of a sense of survival). And there were plenty of lights along the river. If the 200’ AGL ceiling I read is valid, it’s hard to understand how he/she could have been off by a big fraction of that. But he evidently was.
The chopper would have mode C on its transponder. ATC knew how high he was.