ONR Hydrofoil Boat XCH-6 217 
Magnetic drain plugs are employed in the strut and in the pod to provide indication of 
gear or bearing wear. 
ENGINE 
Power is supplied by a General Electric YT-58-2 free turbine engine. Maximum turbine 
output speed is 19,500 rpm. An engine gear box with a 3.25-to-1.0 ratio reduces the output 
shaft speed to a maximum of 6000 rpm. At this speed, the engine has a guaranteed normal 
continuous rating of 900 hp on a 59°F day and 765 hp at 80°. Although available power is 
greatly in excess of vehicle requirements, its light weight and desirable output speed make 
the T-58 particularly well suited for this application. Engine fuel and lubrication systems 
are in accord with normal practice for this engine, with 5-micron and 25-micron filters 
installed in the engine fuel and gear box oil supply lines, respectively. 
A goal of this program has been to determine the location and degree of corrosion 
effects on engine components and to test thereafter various coatings and changes in material 
so as to systematically accomplish a final marinization of the YT-58-2 engine. Accordingly, 
initial installation utilized a standard engine, No. SN-200-103, without any special compo- 
nent protection, extemal cowling, or maintenance procedure. 
External corrosion was first observed on small, unpainted areas of the engine’s magne- 
sium front frame and of the magnesium reduction gear box. Further corrosion was then pre- 
vented in these locations by a grease coating. Thereafter, stiffness became apparent-in the 
linkage motion of the variable stator system. This stiffness was then corrected by periodic 
application of oil. Subsequent corrosion occurred on other exterior components. Again, 
after observation for a suitable period of time, further corrosion was halted in each locale by 
regular application of grease or oil. 
Engine operation was continued, with inlet exposure to direct salt-water spray, until the 
turbine inlet temperature reading at idle had increased to approximately 100°C higher than 
normal. Removal of the compressor casing revealed a significant amount of corrosion through- 
out the entire compressor, with the effects of corrosion increasing toward the later stages. 
Although the aerodynamic configuration of the higher stage blading had been materially 
affected, engine starting difficulty had not been encountered. The compressor rotor was 
cleaned by hand using large, gun barrel brushes; blades were removed and cleaned with an 
aluminum oxide blast. The engine was reassembled and a cowling was installed to protect 
the inlet from direct salt-water spray. In addition, engine washdowns were begun whereby 
2.5 gallons of fresh water were sprayed into the inlet just prior to engine shutdown after each 
test period. A second period of operation, equivalent to the first, was completed and internal 
engine components were again inspected. It was found that the simple procedures then 
adapted had essentially halted the spread of further corrosion. Engine temperatures and oper- 
ation remained normal over the observation period. 
A second engine, No. SN-200-102, has recently been installed and is currently being used 
during test operations. It is a modified engine intended to test the effectiveness of certain 
coatings in preventing corrosion of engine components. Table 2 gives a list of these compo- 
nents and their coatings. Prior to installation, test-stand operation was completed by the Gen- 
eral Electric Company to determine the effects of these modifications on aerodynamic charac- 
teristics. They have been found small, and guaranteed performance ratings remain unchanged. 
Vehicle operation will continue to use engine washdowns, exterior oil application and inlet 
cowling. While no effects of corrosion have yet been observed with this engine, insufficient 
operating time has been accumulated to allow proper conclusions. 
