Anything that could find or sink a submarine was worth supporting in World War II. Since lighter-than-air ships could do both, the U. S. Navy put more than 170 of them in the air between 1941 and 1945. During this period, airships flew convoy escort for 89,000 ships without losing a single vessel. ASW airship patrols operated on both the Atlantic and Pacific Coasts of the United States, in the Gulf of Mexico, and off South America, Morocco, Gibraltar, and France.
With the end of the war, the fortunes of lighter-than-air began to decline. Technological advances in heavier-than-air fixed wing aircraft, helicopters, and in the hunted submarines themselves obscured the airship from the view of men whose eyes were looking only for speed and killing power. The Navy’s L.T.A. fleet dwindled to less than a hundred ships. Memories of wartime success faded, and pre-war failures of rigid airships were recalled.
Of America’s rigid airships, only the Los Angeles was free from tragedy, and she was built in Germany. Delivered to the U. S. in 1924 as a prize of war, she flew without an accident until decommissioned and broken up for scrap in 1932. Each U. S.-built rigid, on the other hand, had an average life of about two years: Shenandoah, 1923-1925; Akron, 1931-1933; and Macon, 1933-1935. Each was lost in a storm.
German dirigibles, even though forced to use highly inflammable hydrogen gas for buoyancy, were singularly immune from mishap, or so it seemed. They piled up record after record in the late twenties and early thirties. But the flight achievements of the Graf Zeppelin and Hindenburg paled into insignificance beside the adverse impact on public opinion of the explosion and burning of the latter rigid airship in 1937. Small wonder that at this point, outside of a small, staunch circle of lighter-than-air advocates, there was little confidence in the future of the airship.
This lack of confidence was evident in the talk and actions of both the taxpayers and their elected representatives. Citizens and legislators were unimpressed by arguments that rigid airships and non-rigid airships are vastly different, that hydrogen is not like non- inflammable helium, that aircraft metals and structural engineering would improve. What the country needed, said the fund donors and the fund planners, was new weapons, not old experiments. Still, airships could find submarines, they could carry heavy loads of detection equipment, they might come in handy for coastal defense. It did not seem logical to cancel out the large investments made in airfield and hangar facilities for lighter-than-air. The result: non-rigid airships were retained by the U. S. Navy and continued to operate on a reduced scale. Not completely accepted, but tolerated, frequently the subject of controversy, lighter-than-air hung on through successive governmental administrations, always laboring in the shade of the new weapons.
But the new weapons had flaws, too. One of these weapons was defensive radar. One of its flaws was that gaps could occur in its early- warning coverage. The faster enemy bombers could fly, the farther the radar defense perimeter had to be extended. Success of the air defensive network around the United States depends on its advance warning capability. The fast-moving and often bewildering events since World War IT have taken the United States through one small war fought with old weapons and on into a new era of defensive and offensive maneuver on a global scale. New and unprecedented tactics and tactical tools have appeared. Means are constantly sought to increase the effectiveness of these tools. Dewline, Conad, Sage, and GOC have all been developed to extend the early-warning perimeter, but not even the most optimistic defense planner would claim that there were no holes in the radar fence. Ways and means of plugging these holes must be found. In the game of national defense, Early Warning is on the first team.
The small, staunch circle of lighter-than-air advocates had not been idle through the years. If airships could carry heavy anti-sub- marine warfare gear, why not heavy loads of radar? An Airship Airborne Early Warning Squadron was formed early in 1956. The results were interesting and significant. Using lessons learned by long and bitter experience, the airship men loaded their craft with care and with precision. Proceeding cautiously but methodically, they made many experiments, drew many conclusions, made many improvements. They were able to prove what they already knew, that the lighter-than-air craft is mobile, that it can lift a tremendous load of early-warning equipment, that it can carry the personnel, the fuel, the provisions for a very long patrol. They demonstrated that airships were a suitable warning platform that could check vital but remote areas at low and medium altitudes, higher than the shore stations and the Texas Towers, lower than the WV-type Constellation airplanes.
One tremendous if loomed large before further progress. It was generally conceded that LTA would be a welcome addition to the early-warning net, if it could be counted on to do the job on an all-weather, around the clock basis. It was not hard to find scoffers who frankly contended that this was impossible. The big bags, said the scoffers, were unmanageable in high winds. In icing conditions aloft, freezing buildups on the bag would force the airship to earth. Ice would fly off the props and tear the envelope. Lightning would strike and destroy the whole ship. Thunderstorm turbulence would tear it to pieces. Remember the Shenandoah—the Akron—the Macon!
LTA men were quick to point out the characteristics of the craft they claimed would meet this weather challenge. The ZPG-2 type airship is a blimp. Unlike the rigid airships of old, its tough, rubberized envelope has no metal supporting members except for some short, curved, forming strips at the tip of the nose. Having a flexible envelope, the blimp is not subject to the stresses and shocks that destroyed rigid airships. Soft and pliant, the blimp rolls with the punch, relaxed rather than resistant.
At its longest, highest, and widest dimensions, a ZPG-2 measures 342 feet, 96 feet, and 77 feet, respectively. The bag holds 1,000,000 cubic feet of helium and air, with the helium riding on top. Below the helium, adjustable fabric chambers called “ballonets” contain air under slight pressure. Blower air, controlled by the pilot, distorts the ballonet to squeeze the helium above it forward or aft as desired. When the helium moves aft, the center of buoyancy moves aft. When the helium moves forward, the center of buoyancy advances to trim the nose of the ship up.
Beneath the envelope hangs the gondola or car, suspended from a “catenary curtain” reaching to the top of the inside of the bag, and supported at the sides by the bag itself. In the ZPG-2 type, this car has two decks. Engines are inboard, where they can be serviced in flight. Shafts from the engines extend from either side of the car through a streamlined housing to turn the propellers. From the control area in the forward end of the car, modern yoke-type dual controls, hydraulically boosted, move elevators and rudders. An autopilot, result of many years of research and development, takes the strain on long flights. A wardroom, crew’s quarters, galley, and head take up car volume not occupied by control compartment, engines, CIC, storage, and fuel spaces.
“Lighter-than-air” turns out to be a misnomer for most blimp operations. Rigged heavier-than-air for cruising, the airship takes off by rolling down the runway on its retractable tricycle landing gear, lift supplied by the airfoil shape of the envelope carrying it aloft. In the air, the helium volume can be regulated to make the ship truly lighter-than-air, and free ballooning can be enjoyed if the engines are cut.
An interesting problem for those used to heavier-than-air concepts is that of “stalling out up.” This can happen when an airship, rigged lighter-than-air, rises. The pilot increases the down angle, and uses power to return to his lower altitude. Too great an increase in the bag’s angle of attack, and the airfoil shape hits the burble point and stalls out—but in an upward direction! There is no remedy but to valve out helium, restoring the balance of gravity vs. lift. Airship crews take such peculiarities of their craft in stride.
The crew of a ZPG-2W, the early warning version of the ZPG-2, is a respectable equipage for any twin-screw craft capable of fifty knots standard speed, seventy knots flank. The “Old Man” is the command pilot. His officer complement contains a pilot, co-pilot, and C.I.C. Officer. His black gang is one mechanic to service the engines, his deck crew a rigger for envelope and car. Six electronics- men, radar and radio experts, comprise his juice and radio gangs, and the galley is ruled by that most indispensable of all experts, the cook. Cook and captain are on continuous duty. For long patrols, reliefs for all other stations are carried, making a total complement of twenty-four. There’s room, too, for observers, and for casual crew members such as an aerographer for special missions.
The Chief of Naval Operations and the Office of Naval Research programmed an exercise to take the if out of LTA’s radar role. It was tough, but no one knew just how tough it could, and did, get, until it was under way.
The commanding officer of the Naval Air Development Unit at NAS, South Weymouth, Mass., and the commanding officer of Airship Airborne Early-Warning ONE at NAS, Lake- hurst, N. J., were directed to provide five airships for a special test. The test period was January 15-25, 1957—midwinter. The test area: an expanse of the North Atlantic, 200- odd miles off the New England coast. The problem: maintain continuous single ship airborne early-warning patrol, twenty-four hours a day, for ten days.
All hands concerned with the exercise knew that much advance planning would be needed. Each blimp would be on station twenty-four hours. Crews would be on watch- and-watch, heel-and-toe. Relief airships would have to be standing by outside the hangars long before the Estimated Departure Time of each patrol. To-and-from en route time had to be considered in programming fuel and food provisioning. Radar and engine maintenance had to be perfect.
Perfection, obviously, could not be achieved without painstaking preparation. A four- phase operation evolved. Phase 1 evaluated ground handling characteristics of airships in adverse weather and high winds. Phase 2 checked blimp reaction in flight to icing conditions. When phase 3, the ten-day patrol, came up, invaluable experience and knowhow had been accumulated. Upon the success or failure of phase 3 depended the completion or cancellation of phase 4, placed at the outset of the program in a highly classified category. Phase 4 was to be a long distance flight, one to attempt feats never before achieved by airships.
Phases 1 and 2 went smoothly enough, and it was discovered that the big bags would handle acceptably in high surface winds if due care were exercised. To the not inconsiderable surprise of many, it appeared in phase two that ice would build up on the blimp envelope at a high initial rate, then taper off to insignificance, making it possible to continue flight undue difficulty once initial weight increase and adverse handling characteristics had been compensated for. Phase 3 began to seem more encouraging.
It had been expected that Phase 3 would be brought off in winter weather, but no one anticipated the kind of weather that would actually prevail during the ten days beginning January 15, 1957. When airship operations began, predictions were for exceedingly unstable weather over the entire East Coast region. What actually ensued was to be called by experienced aerologists the worst ten days of winter weather seen in this part of the United States in thirty-five years. Freezing rain, fog, sleet, snow, hail, turbulence, thunderstorms, high surface winds—if it was weather, and had a name, it was there.
In spite of the “impossible” weather, the test went on as scheduled. Those conducting the operation were under no delusions. One experienced LTA officer put it this way: “a ship is good, or it isn’t,” he said. “If it isn’t good, then we should deflate them and put them in a box. Why waste the taxpayer’s money?” Another called the ten-day test, “A pioneering step as important to us as Lindbergh flying the Atlantic.”
Tension mounted at South Weymouth and at Lakehurst as the operation went forward. The weather, bad at the beginning, got worse. Winds at the takeoff and landing sites steadily increased. A takeoff was made with the anemometer showing thirty-five knot steady winds. Ten minutes after this takeoff, gusts of up to sixty knots were recorded. Another airship was forced to stand by outside its hangar for eight hours while snow fell steadily. Three inches on the runways, no one knew how much was on the bag when the takeoff time arrived. When the nose of the ship was released from its mooring mast, the weight of snow on top of the bag forced the tail toward the ground. The Command Pilot, using full down elevator and full power on both engines, cushioned the impact somewhat, but the tail still struck earth. Rebounding like a limp football, the big gas bag staggered skyward and lumbered off on patrol. Considering the fact that it was made at night, this takeoff could qualify as at least one of the most precarious moments of the test period.
One ZPG-2 took everything the test area could throw at it in the way of icing conditions for thirty-two of the forty hours it spent in the air. Moderate to severe ice was encountered at all altitudes from 200 to 3,000 feet. This ship began and ended its on-station period on schedule.
A new ZPG-2W endurance record of 56.3 hours without refueling was set when worsening weather forced a Lakehurst airship to divert for South Weymouth when halfway home after a twenty-four hour patrol. Battling through headwinds, clouds, turbulence, and ice, the tired crew ironically found conditions at South Weymouth at least as bad as at Lakehurst. The final landing was made without incident.
There were anxious moments, but advance training and preparation paid off. One airship, moored to its mast immediately after returning from a long patrol, was apparently secure. The crew disembarked and headed for the welcome sanctuary of barracks and bunk. But something was amiss. The nose of an airship is held to the mast by a mooring cone, which dangles free from the tip of her nose while she flies. The ground crew inserts this cone into a cup atop the mooring mast. Two retractable lugs in the cup slip into an annular groove in the cone. The blimp can then pivot about the mast, swiveling into the changing wind, remaining snug and stable, as long as the lugs are in place. But in this instance, the lugs were not in place. They had frozen in a retracted position. The cone slipped out of the cup and the blimp was loose.
Before the wind could sweep the unmanageable envelope across the field and into a hangar side, volunteers leaped into the car and started the engines. One nimble and hardy bluejacket clambered up the 60 foot mast. Working unprotected in an icy gale, he used a sledge hammer to “unfreeze” the offending lugs. The landing party worked the nose cone back into the cup while the crew in the ship held her steady on. The lugs were driven home, and the airship was properly secure.
The final test of the airship’s “all-weather” capability came during a situation made to order for such a purpose. A Ground Controlled Approach is a precision maneuver for any aircraft. Precise corrections, radioed by GCA personnel to the aircraft, must be answered instantly and exactly to guide the craft along a pre-determined ground track and glide path leading to a touch-down point on the runway. Airships do not respond swiftly to minute corrections. Close to the ground, their very slowness can make them dangerous. Control forces are less, course and altitude changes difficult to effect on short notice.
A ZPG-2W returning to Lakehurst found the station wrapped in ground fog and drizzle. Requesting present weather, the Command Pilot heard the matter-of-fact voice of the tower operator reply that it was ceiling 200 feet, visibility 3/16 of a mile. The landing was completed on the first pass. Without even a pause for congratulatory messages, as soon as the landing airship had cleared the runway, another took off. The weather was not the same, however. The ceiling had dropped from 200 to 100 feet.
When the last blimp landed on January 25, 1957, at 9:20 a.m. at South Weymouth, the patrol area had been continuously covered for 240 hours. As reports of the weather conditions on the eastern seaboard continued to come in, LTA fliers began to realize the significance of what they had done. Even the most optimistic prophets found it hard to grasp.
During the time the blimps had operated continuously without an accident, and particularly from January 14-16, commercial airliners from Maine to Florida were grounded. On January 16, military all-weather aircraft were grounded. And the silver behemoths had continued to lumber in and out of their hangars, relieving on station, on time. On January 26, 1957, the Assistant Secretary of the Navy for Air, at a luncheon of the Aviation Writers’ Association in Washington, made the following statement:
“These airships flew through extremes of snow, freezing rain, winds of sixty miles an hour and severe turbulence— conditions which at times kept all airplanes grounded.
At 9:20 this morning the last flight landed at the Naval Air Station at South Weymouth, Mass., successfully completing an all-weather evaluation which provided a continuous airborne alert of over ten days.
We feel that airships offer many advantages as a warning radar platform.” (Italics supplied.)
Without question, lighter-than-air was ready for Phase 4. One of the U. S. Navy’s most experienced LTA pilots, was assigned a ZPG-2 and given secret orders. Every item taken on board the airship was weighed and stowed according to plan. Fuel consumption curves were meticulously plotted. Support and flight-following tactics, weather reporting, and communications schedules were laid out. The objective of all the secrecy, the careful planning, the exact calculation, was a goal dear to the heart of U. S. Navy lighter-than- air men for 28 years. The ZPG-2 was out to break the distance and endurance record of the German Graf Zeppelin. The venerable Graf, in 1929, flew nonstop, without refueling, from Friedrichshafen to Tokyo, covering 6,980 miles. For a non-rigid airship, a standard U. S. Navy blimp, to challenge this record was audacity itself.
Nevertheless, when the ZPG-2 floated down on Boca Chica Field at Key West, Florida, on March 15, 1957, the U. S. Navy took possession of the lighter-than-air long range and endurance record. The sturdy, stubby Navy blimp had covered 8,216 miles in eleven days and fourteen minutes. From her base at South Weymouth she had cruised over three continents, crossing the Atlantic on a continuous round trip eclipsing all former achievements by any airship anywhere.
The big IF has been erased. There is a new light in the eyes of lighter-than-air men. All- weather, around-the-clock radar early warning patrols are feasible for blimps, and they are proud of it. There’s something doing in LTA.