Part II : 1950-1957 / 8. Suntan
Engine Tests
[158] The testing of the 304 engines was carried out at Pratt &
Whitney's new center west of West Palm Beach, Florida. The test center, still
under construction in the fall of 1957, was the result of several years of
planning by United Aircraft officials to overcome the limited space for testing
at their Connecticut plant. Problems of safety and noise made a more remote site
desirable, and there were considerations of dispersal of facilities for defense
reasons. These had led to the choice of West Palm Beach County as a desirable
test site. United Aircraft acquired a large tract of land, swapped part of it
for adjacent land owned by the state, and ended up with 27 square kilometers of
sand, scrub pine, swamp, and alligators-well suited for remote testing of new
engines. In the negotiations for the hydrogen engine contract, United Aircraft
officials indicated a willingness to invest $20 million in permanent facilities
at the new center if the Air Force would pay for all movable equipment, also
estimated to be about $20 million.29 The cost sharing was agreed upon in principal, if not in the exact
amounts, and construction proceeded. During initial operations, the test crew
often had to call for a bulldozer to clear the unpaved roads of deep ruts to
allow passage; alligators were a common sight.30
The first 304 engine tests began on 11 September 1957 using
three fluids: nitrogen, gaseous hydrogen, and liquid hydrogen. The inert
nitrogen was used to check the fuel system and rotating machinery, especially
bearings and seals. The first series of runs lasted through October; 4 1/2 hours
were logged, including 38 minutes with liquid hydrogen. The engine was removed
for inspection and overhaul when turbine oil consumption became excessive. When
reinstalled for a second series of runs on 20 December 1957, no significant
failures occurred, but the engine was periodically removed, inspected,
overhauled and reinstalled.31
Six series of runs were made through the first part of July
1958 and 5 1/2 hours of operation with hydrogen were accumulated. Only minor
problems were encountered until the last run, when there was a major failure of
bearings, turbine, and heat exchanger. Meanwhile, a second engine of the same
type had been installed on a twin test stand; its first run was made on 16
January 1958. Tests continued on the second engine into the first part of April,
with a little over 10 hours of operation with hydrogen. The engine was removed
when the low pressure section of the turbine failed.
During the testing period, Coar and Mulready designed and
built a second model of the 304 engine, which had an additional (fifth)
compressor stage and lower specific fuel consumption. The first 304-2 was
assembled at East Hartford on 20 June 1958 and four days later was operated at
the Florida test center. Tests continued for a month, with 3 1/3 hours of
accumulated running time with hydrogen before the engine experienced a complete
turbine failure. It was removed for repair and strengthening of the turbine
disks. While this engine was in the shop, another 304 engine (presumably of the
first design) was installed and operations began in mid-August. This engine
operated satisfactorily through September and accumulated over 6 hours time
using hydrogen. Table
5 shows a comparison of the specifications and
performance of the two versions of the 304.
By the end of September 1958, the repaired 304-2 engine was
back on the stand and made a short run, and another 304 engine was nearing
assembly at East Hartford.
