Not sure if this is relevant to your particular case, but.....
don't confuse alty output (which is rotational-speed dependent anyway) and breaker current capacity.....most breakers incorporate a bimetal strip, and /or an electromagnetic latch.....the latter will be instantly resettable...the bimetalwill get cooked up by too high a current and open /release the contacts it will take time tocool down to it,s normal shape in order to reset.......
As you've eliminated all other loads on that breaker,and it doesn't trip with any of those, I conclude the fault lies with the pitot -heater and/or associated wiring/switching....a high-resistance earth-fault could pass sufficient current, together with the heater, to trip a breaker.(say the pitot -feed passes through an earthed aluminium bulkhead and the insulation chafes through.)
we are making the assumption that the breaker is correctly rated for the load......If, for example, panel-lightsare wired through a 5-amp trip and then someone later adds another item to take the total load on that breaker,over it's rating, you'll have problems.
Sounds like your repeat tripping is normal where a fault exists....a pitot heater which is partially-shorted (assuming it's wound from resistance-wire) would draw a higher -than-rated current.
disconnect feed at pitot(isolate/insulate) switch on.....NO current should flow/-if it does, look for a shorted-to earth wire but remember an indicator-bulb could be in parallel with the feed to the pitotand show the appropriate current!
reconnect pitot-heat with an ammeter in series(if you're on 12V, they can be found in car scrappers or about a fiver new from a decent car accessory emporium.)...turn on and compare current with rating-plate and with the breaker rating.
As BP has said, it's extremely dodgy to keep resetting a trip.....in theory, the feed to the trip is unprotected , but substantial enough to take the max current the trip could pass ....but, there is a possibility the trip could malfunction and cause a high current to flow, cooking the wiring and anything (other, bundled wires, fuel lines etc.)in close proximity.
Your battery can probably poke in excess of 200 amps down a shorted wire- enough to make it glow white hot before it melts through.
(or you turn off the battery master switch.)