Question: Which Formula One car besides the Tyrrell P34 was one of the most radical entries ever to succeed in F1 competition, that used flat panel heat exchangers? 
Sentence (from "Brabham BT46"): The Brabham BT46 is a Formula One racing car designed by Gordon Murray for the Brabham team, owned by Bernie Ecclestone, for the 1978 Formula One season.
Relevant evidence: Yes