H-70 Propellant

H-70 (hydrazine, 70% aqueous solution) is used as the propellant in emergency power units (EPU) on the F16 and other single engine aircraft. When there is a loss of engine power, the EPU activates and provides power to maintain the aircraft’s vital functions such as hydraulic and electrical systems.

H-70 does not work like conventional propellants in that it does not burn to provide energy. Instead it is passed over a catalyst bed which causes the hydrazine to decompose into gaseous nitrogen, hydrogen and ammonia. The presence of the water acts to modify the decomposition temperature in order to prevent thermal damage to the catalyst bed and to the turbine parts. As the water removes heat, it is turned into steam which aids in powering the EPU.