Ok like I said I have not idea if all be-76 have them, but the flapper switch is on the outside (yes there is in an internal one for the over heat but is separate) and its function is a safety for the heater, but the gear needs to be up and you not moving (Crashed or gear up landing) and the heater will not operate…
After I break out my bifocals, I'll check out our Duchess tomorrow.
-mini