Life on the Mountain Top

Contributed by Steve Weatherly

Life on our mountain top was often a challenge, but the maintenance of the radar and radio systems was always a challenge. Some examples follow and it was a trip down memory lane. My congratulations and thanks to so many who put in the long hours, under very bad weather conditions, at an isolated location to keep the site fully operational. Steve

FPS-24 search radar. The cooling system required water that circulated through copper pipes of 6 to 8 inches in diameter. Once when we were replacing a final triode amplifier tube that had been arcing internally, we discovered that it rattled. Inside its cooling jacket we found hundreds of pieces of solder that came from the sweated fittings in the copper tubes of the cooling system. We used a vacuum cleaner to suck them out and returned the tube to operation. Note: maintenance of the water cooling system was a civil engineer responsibility, not ground radar maintenance.

FST-2B. We were constantly greasing and replacing the bearings on the shaft between the AC motor and the 400 hertz generator. We could always tell when there was a problem by the "purple" grease on the T2 day shift crew. Then we discovered that the Canadians had a more rugged frame on which to mount the motor/generator. Once we installed the Canadian frame - problems went away. There were many system integration problems like this with the T2 as evidenced by the hundreds of TCTOs and conflicting circuit diagrams from one TCTO to another.

FPS-90 height finder. We had the inflatable radome with multiple air pressure units and heat banks. There was a Depot (SMALC) overhaul in 1966. The cone assembly on which the antenna was mounted was replaced. The overhaul was completed, signed off, and the team left late in the PM. The radar went operational and night came. Weather was bad, and given the above-ground tunnels that connected the various site buildings, no one walked outside during the swing shift change. At mid shift change, however, one of our intrepid FST-2B technicians did take the outside route and saw the radome doing the "hula". The replacement cone assembly had been for a Canadian site where rigid radomes were used and did not have the internal wiring that supported the air pressure systems that kept the radome inflated. We immediately shut down the radar, bypassed the cone assembly to get the air pressure system working, inflated the radome to spec, and resumed operation. Despite the radome `hula", there was no permanent damage to the radome. From the inside, however, the rubber fabric was permanently marked by the motion of the antenna when it settled on the antenna. For his initiative in learning about the radar systems, and his quick response to a potentially devastating situation, our T2 tech earned an AF Commendation medal for his actions.

FPS-24 search radar radome. The third and last of the rigid radomes was a space frame design comprised of individual panels. Each panel consisted of a metallic frame about 5.5 inches wide and 0.75 inches thick. There were 15 different shaped panels to make up the finished structure. Placement of the panels in the structure had been determined by using a computer program that minimized the effects of the metallic space frame on the antenna`s beam shape and side-lobes. This structure was 70% of a sphere 160 feet in diameter. This allowed for the 145 foot wide, 85 ton, FPS-24 antenna. The flaw in the space frame radome design was with the way in which the thin (0.20 inch) fiberglass membrane was attached to the space frame. The membrane was not stretched tight but was loose. Any wind would cause the membranes to flutter (and you could easily hear it from the ground) and over time crack along the junction with the space frame. We were now confronted with a radome that was "high maintenance". Cracks had to be repaired with fiberglass strips, and adhesive. We ended up with a Danish built "Cherry-picker" crane that had a personnel lift at one end. Spare parts for the crane had to make the journey from Denmark and were always in demand. We also had complete spare panels for emergency replacements (at least one for each of the 15 panels types). These spare panels were kept in large triangular shaped, plywood boxes at the base of the FPS-24 tower. Needless to say, Mt Hebo had extra annexes to the job descriptions for its 303x2 FPS-24 radar maintenance staff. Another "gift" from Hanscom.

Note that a radome was essential for operation of the FPS-24 at Mt Hebo. When the space frame radome was installed, the antenna was also repaired. The antenna was made up of steel tubes (up to 8 inches in diameter) for the central 65 foot wide section. The wing tips (each 40 feet wide) were comprised of aluminum tubing. Operation of the antenna, without a radome, in the winter of 64-65 had severely damaged it. The antenna structure was warped and some antenna tube members were bent or pulled apart. Measurements taken when the antenna was originally made were used as the basis for repositioning the antenna screen to achieve an approximation of the original contour. It worked, but an electromagnetic survey done afterwards led us to move the BX gas station to the other end of the site. P.S. We did get the FPS-24 operational within a month of completing the third radome and fixing the antenna. Lots of water leaks, but that`s another story.

FPS-24 radome tragedy. All the radomes at Mt Hebo had depot maintenance in accordance with TO 00-25-108. This work was done by SMALC using a civilian contractor team. In 1967, the initial depot maintenance for the space frame radome was done. The radome was caulked between the radome panels and painted. Given that the FPS-24 tower was 85 feet high, and the radome was another 100 feet taller, this was not a job for everyone and required special climbing gear such as rope ladders. The civilian team leader was killed when the rope ladder failed more than halfway up on the radome. It took our FPS-24 workcenter staff more than an hour to talk another of the civilians back to the top of the radome and inside. He was just above where the ladder broke, and was "glued" to it and could not move. It turned out that these rope ladders had not been used in some time and had "dry rot" where they could be connected together for "very" large radomes such as was at Mt Hebo.

AS-1090 UHF antennas. These arctic antennas had a fiberglass radome around them. We used them for GRT-3/GRR-7 communications at the GATR site. A high VSWR usually meant we had to schedule the antennas for replacement. The radomes would deteriorate in our severe weather and water would leak in. 4AF had a climbing team out of Hamilton AFB, CA that would come and do the replacements.

Anemometers. Normally the FPS-24 did not have a radome. The FPS-24 came with a wind positioning system that would allow the antenna to move so that in high winds it could be positioned to the point of least wind resistance. This system had its own 90 foot high tower, separate from the FPS-24 building A close look at some of the pictures of the FPS-24 radome at Mt Hebo shows this wind positioning system tower. The system had 2 anemometers and the selsuns were set 90 degrees apart. With the radome, we used these anemometers for a different purpose. In winter, we used the indicated wind speed for a safety program. As the wind speed increased we would restrict outside walking to our above ground tunnels. If there was ice and snow on the FPS-24 radome, we would send non-essential personnel out of the operations areas. Once we had a chunk of ice come off the FPS-24 radome and punch a hole through the roof of the ops building and into the radar operator break room (no one hurt).

Winters at Mt Hebo were often accompanied by heavy fog off the Pacific Ocean. At 3100 feet, this fog would condense and freeze on antenna towers and the anemometers. The ice would build up (6 to 8 inches thick), the winds would come up, and the anemometers would break apart and blow over the mountain side. We never gave it a second thought as spares were readily available. The truth, however, was revealed when the item manager at SMALC called and asked where we were. Seems we used more of these anemometers (6 or more a year) than anyone else including US facilities in the Antarctic (twice as many).

FPS-24 Bearing Replacement. We did our SOAP tests on schedule, but still had a bearing replaced in 1967. The radar eval squadron was on-site and at the request of the FAA changed the feedhorn angle to see if lower altitude coverage would be improved. SOAP test results immediately afterwards showed ball bearing failure. A suspected cause was changes in the dynamic balance of the antenna and associated changes in the track followed by the ball bearings within the race. The SMALC depot team replaced the bearing without any problem over a 3 week period, but it was quite an operation to see. The bearing was 12 feet in diameter and weighed about 8000 pounds. The original bearing used 5 inch diameter ball bearings. The new bearings were tapered rollers. To replace the bearing, the entire 85 ton antenna was jacked up 18 inches. The hard stands for the jack assemblies were built into the roof of the FPS-24 building and were permanent. People new to the FPS-24 always asked what the pads were for on the building roof, and if you saw a bearing replacement you would know. The FPS-24 bearing was so large that with interlocks on, and from inside the building, you could go up into the bearing area and open a port and see the ball bearings. We later learned that in operation, their was a high frequency noise hazard from the bearing - why am I not surprised?

Weather tidbits. Most buildings at Mt Hebo had functional shutters on the windows (the 2 story barracks was an exception). During high winds in the fall, stones as big as your fist would be blown around. When I arrived in June 65, I remember asking why there were stones on the roof of most buildings. I was told wait and learn. Indeed, inside our metal Guam huts (such as the BOQ, Admin, Dining Hall, and NCO club, the rocks hitting the buildings made quite a noise and quite an impression; I got my answer.

We had a 250 gallon water trailer in support of the GATR site. In the winter the road would be blocked by snow and the GATR troops were snowed in. Water and K-rations were what they had. We also had a snow cat with wide rubber tracks(and cleated) to negotiate the snow. We ran it at top speed to keep from sliding off the mountain as many parts of the path to the GATR site went very close to the edge. Our 250 gallon water trailer got drafted for Vietnam, 6 month later our 100 gallon replacement arrived.

Our 7 foot tall security fence around the radar area was often buried and on 2 occasions I walked over it wearing snow shoes.

Each winter at Mt Hebo, the BOQ was buried in the snow. Civil engineering would add extensions to the heater vents to keep them above the snow.

The snow at Mt Hebo was usually of very high moisture content and caused icing on the access road. You could easily slide down the access road from the site to the Housing Area (about 2 miles) and never walk a step.

The access road was repaired every year. Our 2 engine snow blower worked fine, but by the spring you could see white snow and black chucks of pavement coming out of the blower.

Until the radar site at Cottonwood Idaho closed in 65, we had no winter sports equipment. We thanked them for the snow shoes, skies, ice skates, hockey equipment, and sleds that were transferred to us. They made for lots more winter excitement.

Mt Hebo would get feet of snow in a day and than it would rain. We often had water pouring down the main street until the snow melted in the storm drains. This pooling of water could then freeze, and I saw cars whose wheels were encased in ice and going no where.