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.
Physical Properties of H-70 Propellant
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.
H-70 Specifications
| Properties | Value |
|---|---|
| Hydrazine (% by weight) | 69-70 |
| Water (% by weight) | 30-31 |
| Particulate (mg/L) | 1.0 |
| Chloride (% by weight) | 0.0005 |
| Aniline (% by weight) | 0.40 |
| Iron (ppmw) | 20 |
| Non-volatile residue (mg/L) | 40 |
| Carbon dioxide (% by weight) (1) | 0.003 |
| Carbonaceous Material (Total as OVCM and OCM) (% by weight) | 0.02 |
| Note: 1 Determination of CO2 content must be performed before all other analyses to prevent further absorption of CO2. |
H-70 is a clear liquid with the appearance of water, but having a strong odor resembling ammonia. It is very caustic and is a strong reducing agent. The physical properties of H-70 Propellant are listed below.
H-70 Physical Properties
| Density | @ 25° (g/ml) | 1.003 |
|---|---|---|
| @ 25°F (lb/gal) | 8.337 | |
| Boiling Point | @ 760 mm Hg (°C) | 119 |
| @ 760 mm Hg (°F) | 246 | |
| Freezing Point | (°C) | -49 |
| (°F) | -56 | |
| Flash Point | TCC (°C) | 82 |
| TCC (°F) | 179 | |
| Flammable Limits in Air | (% N2H4 by vol) | 4.7-100 |
