Fairchild FC-2, modified for icing flight tests.
A steam boiler heated by the engine exhaust heats a small test airfoil mounted beneath the wing.
A water spray is mounted in front of the test airfoil to provide simulated cloud conditions in flight.
from NACA-TR-403, "Ice Prevention by means of Engine Exhaust Heat and Technical Study of Heat Transmission from a Clark Y Airfoil", 1931