The Cyclocrane The largest experimental aircraft ever made and the first new type of aircraft since the helicopter, the Cyclocrane, the invention of Arthur G. Crimmins, Jr., flew in Tillamook, Oregon in the 1980s. By Rob Crimmins
The Cyclocrane was a hybrid airship intended for ultra-heavy vertical lift. Hybrid airships use lighter than air gases and aerodynamic forces to generate useful lift. The Cyclocrane used a device known as a cycloidal-rotor for producing aerodynamic lift. Helium, and for awhile a helium and hydrogen mixture, were the lifting gases. The inventor of the Cyclocrane
was Arthur George Crimmins, Jr., my father. Dad came up with the idea after working on a similar device, the Aerocrane, which was conceived by a brilliant engineer, Donald B. Doolittle. Don was the President of All American Engineering, a Wilmington, Delaware manufacturer of aircraft arresting gear among other things. When Don invented the Aerocrane Dad was the company’s marketing director. I was in high school when Dad and Don began work on the Aerocrane in the early 70s and I even helped Dad a little on the first model in 1973, parts of which were built in our basement. I also saw them conduct early flight tests in All American’s shop on the riverfront in Wilmington. Dad immersed himself in his work and when he was on a project that excited him his devotion to it could become complete. As he learned more about the industries that the Aerocrane would benefit he became more dedicated to the advancement of the idea. He was an engineer too so he was able to contribute to the development of the concept in nearly every way. While considering how to overcome some of the complications with the Aerocrane the idea for the Cyclocrane came to him. The Aerocrane generated aerodynamic lift with a rotor disk that turned on a vertical axis just like a helicopter. Like a helicopter it had, what Dad called, a “second order effect” control system because the rotor disk had to be tilted in
order to maneuver which is not a problem in a helicopter. In order for that not to be a problem for the Aerocrane it would have to be able to generate a lot of force pretty quickly to resist the wind. The physics dictate
that the only way for that to work would be to make the rotor disk very large or to add another set of wings on the ends of the rotors. There were also Magnus-effect instabilities inherent in the Aerocrane that could have required complicated control systems not readily available in the 1970s. So an Aerocrane large enough to work without wings attached to the ends of the rotors and with the necessary control systems would be prohibitively expensive for a small company to build. Dad pictured the alternate configuration, the one with winglets on the ends of the rotor blades, turned ninety degrees so that the axis of rotation was in the direction of flight rather than perpendicular to it. That arrangement of rotating airfoils is a cycloidal rotor or cyclo rotor and the marriage of that to an elongated aerostat became the Cyclocrane, an aircraft that would work in a much smaller size. Cyclocranes capable of carrying sixteen tons would have significant commercial applications but an Aerocrane built to carry anything less than fifty tons wouldn’t work. Dad and Don struck out on their own to develop the Cyclocrane, for which Dad was granted the U.S. patent (#4482110), and decided to build a proof
of concept model that could lift just two tons. A vehicle that small wouldn’t have any commercial use but it would serve to attract investors so Don and another ex-AAE, Inc. employee, Bob Caufman, got to work on designing the two ton Cyclocrane while Dad looked for money, which he eventually found in a consortium of Canadian logging companies, the most important being McMillan Bloedel. Don moved to Bozman, Maryland with his wife Betty, after retiring from All American, so did Dad and his wife, my mother, Joan Crimmins and Bob, and the four of them got to work building the largest experimental aircraft ever made. The two ton version would be the smallest Cyclocrane ever made but that doesn’t mean it was small. When Don finished the engineering he had designed an airship that would be one-hun-
dred-and-eighty-four feet long with a one-hundredand-thirty-two-foot wing span that would weigh seventeen-thousand pounds and include a 330,000 cubic foot aerostat. I moved with my wife Judi and our eightmonth-old son, Daniel to Neavitt, Maryland to become the fifth member of the team in August of 1980. Dad taught me how to operate the lathe and milling machine in Don’s garage where I would work until we moved to a large block building next to Dad’s property
the next year. Shortly after I started (or maybe even a little before) a young French engineer joined us. Daniel Guimier worked for FERIC, The Forest Engineering Research Institute of Canada. Daniel kept track of our progress for the Canadian investors and helped Don. He was a very big help too with component design and analysis. He also figured out many of the details having to do with assembly which ultimately became my main task. After the move to the new shop others joined us beginning with Hunter Harris, a fixed wing, commercial pilot and A&P mechanic and Alberto Santa Maria, a retired Boeing Vertol helicopter pilot. Hunter
recommended two men, Chris Wegener and Ted Wiltbank, and next to join us were two electronics technicians who were friends of mine, Bill Giordano and Art Regan. We could make all the parts in the new shop but final assembly had to be done in a hangar, a very big hangar, very few of which exist. Most are left over from the 1920s and 30’s when the German and US Navy dirigibles were flying or from World War II. The hangar that we were able to secure for assembly and inflation was in Tillamook, Oregon so in June of 1981 we packed up all the parts that we’d made, all the tools, furniture and fixtures and all our households and moved to the West Coast. The hangar was one of two that the US Navy constructed in Tillamook at the beginning of World War II for their K Type airships that were used along the East and West Coasts for anti-submarine warfare. One of the hangars was a sawmill and full of equipment used to turn trees into lumber and plywood. Louisiana Pacific operated the mill and had more
equipment in the other hangar but there was room at one end of the second one where we could assemble the structure and inflate the balloon. The balloons and blimps that I worked on later in my career are inflated in a day. All the hardware on a blimp or a kite balloon is attached to the skin and internal pressure keeps everything on the envelope in place. It doesn’t take long to bolt and lace all the components to the skin of a blimp and put in the gas. The comparable operation with the Cyclocrane took six months. One reason why it took so long was because most of the assembly was done by just three of us, Chris Wegener and a young man we hired in Tillamook, Steve Shelfer, and me. There were times when a lot of hands were needed, like when the envelope or gas bag had to be spread out or turned or when heavy and large components had to be carried inside but on most days during the assembly process the guys tying line and turning nuts inside the aerostat were Chris, Steve and me.
(We used three different terms for the balloon itself. The fabric envelope could be referred to as “the envelope”, “the gas bag”, which was not meant to be funny, or “the aerostat”. (Anything that can hold a lifting gas and remain at a fixed altitude is an aerostat.)) Hunter put the engines together and some very talented technicians and engineers joined Bill, Art and Dad to design and build the electronics and avionics. Fabrication and assembly work on the mooring mast, the tail, the wings and blades, ground handling equipment and the forward cab and the lower cab, which was the pilot’s, co-pilot’s and flight engineer’s station took place in the shop, which was separate from the
hangar. The whole crew, about thirty of us, was needed to move the thing from the hangar to the mooring mast and we finally did that on October 9, 1982. There was still work to do, mostly with the electronics and controls but there was pressure to demonstrate progress so Dad decided to do the remaining work outside on the mast and make the first flight sometime in October. The weather in September on the Oregon Coast is beautiful and it can be very good in October too so being outside in the weeks leading up to the first flight was very pleasant. Unfortunately we took too long to button up the last few details. On October 21 a storm was off the coast and headed toward us. The forecast was not for high winds and by the time we knew a storm was coming it was already too breezy to move the ship so we kept it on the mast, which was a very massive and strong, one-hundred foot logging tower, so we thought that even if the wind did rise it would be alright. And we were, for awhile, but at 09:45 on the 22nd a violent squall went through and the Cyclocrane was torn from the mast and crashed in a pasture five hundred yards to the north. That short period of severe weather was the worst of the day and by the afternoon the storm had passed. For my family and some of the men and women on the crew that date is still “Black Friday”. It took about a week to get every thing out of the aerostat and it rained most of the time. There was so much water in the balloon we wore wet suits. It was a very hard task but we all did what we had to. Chris and Steve once again proved themselves to be iron men. On the Friday after the crash we ran an announcement on the AM radio station in Tillamook asking for help to fold the aerostat and pack it in a crate for shipment back to ILC Dover, in Frederica, Delaware where it would be repaired. The next day fifty
people were there to help. Which brings up another part of the story that should be told. The people of Tillamook are the best. From the day we arrived they were with us. Every time there was an opportunity for the community to get behind the project they did. The local hardware store, Kenny Bell’s print shop, Tillamook Trucking, Morris Supply, Louisiana Pacific, The Headlight Herald, the local newspaper, the radio station, KTIL, The Port Of Tillamook Bay, the airport operator, everyone was supportive. There was one company and individual to whom we owed and owe the most, that’s Churchill Logging and George Churchill. George was there, with his crew, every time we took the Cyclocrane out of the hangar. He loaned equipment to us, in fact one of his trucks stayed in the hangar for us to use whenever we wanted. He gave us the logging tower that became the mooring mast and he provided all the trucks and equipment and his crew to erect it. He let us use his airplane, which he piloted, when we needed aerial video and photography. Dorothy, George’s wife, took the 8mm film of the crash. I’ll never forget all that George, Dorothy and his son Dave, did for us. They were the most generous people I’ve ever known. From the afternoon of the crash Dad was determined to rebuild. When we regrouped in the office while the Cyclocrane and thousands of hours of work lay in a heap I asked Dad what we do now and he replied, in a completely matter-of-fact tone, “We’ll rebuild it”. We were insured, through Lloyds of London, and the agreement with the Logging companies said that they would back us until the end of the first flight so Dad’s intention, from the afternoon of October 22nd, was to recover all the parts, fix the broken ones and try again. So that’s what we did.
The first thing to do was to get the value of the Cyclocrane from the insurance company which was an interesting exercise. It cost about four million dollars to build it originally. They sent experts to determine the cost to replace it and the first man who came realized right away that he couldn’t figure it out without help. We were able to give him a good estimate but it was more then they wanted to pay so they hired Airmetal Northwest, a Seattle company with mostly ex-Boeing employees and expertise in airplane restoration to go through everything. They were amazed that we built the Cyclocrane for as little money as we had and recommended that we get everything the policy covered, which was enough to put it back together, which took another two years. It wasn’t as hard the second time and we had a much better aircraft when it was done, but it wasn’t without hardship. There were numerous, minor examples and some major, the most notable being the time the ballonet split and we nearly lost all the gas from the balloon, and Chris. The ballonet is an air chamber, or bladder, inside the hull. There are different kinds of ballonets but, with only one exception I know of, all non-rigid airships have them. It’s the way constant hull volume and shape is maintained even though helium constantly expands or contracts and they’re nearly as fundamental to airships as wings are to airplanes. During ascent or when the temperature rises helium expands. To relieve the pressure, valves open and let air out of the ballonet. During descent or if the helium cools it contracts and then the blowers run to pump in more air and make up for the lost volume. Blowers keep the air in the ballonet at a slightly higher pressure than the helium (or hydrogen) so the ballonet curtain bears on the helium which bears on the hull.
That force causes the envelope to keep its shape and resist flight pressures. Until the Cyclocrane, in every aerostat whose shape is maintained with hull pressure, the ballonet had been at least one chamber attached to the inside of the hull at or near the lowest point. The Cyclocrane couldn’t use that tried and true approach because it rotated. The analogy is water in a bottle. Imagine a few ounces of water in a bottle turned on its side. If you rotate the bottle along its long axis the water will tend to stay on the down side. If the water was in a bag glued to the bottom of the bottle when the bottle is turned the water will fall and stress the bag. Air would do the same thing in the Cylcocrane so our ballonet had to be a cylinder that ran the length of the balloon, on the long central axis, from nose to tail. And it couldn’t go slack. The cross sectional shape as well as the volume had to change to accommodate changes in lifting gas volume. Don and the geniuses at ILC Dover, George Durney and Dale Williams, came up with the design for the Cyclocrane ballonet. It had a four-leaf-clover cross section and was pinned to the longitudinal structure with sixty-eight, 1/16” diameter, 7x19 aircraft cables that ran through a series of pulleys to a winch in the forward cab. When the lifting gas expanded and the ballonet volume needed to decrease the winch was activated, the inboard points of the “clover” were drawn in, and air was forced out of the ballonet, then a brake would set, holding the retraction cables, and therefore the ballonet, in position. When the lifting gas contracted, as it would when the ship flew under a cloud where the temperature is lower, or when it was ascending the brake would release and fans would run to add volume to the ballonet until the lifting gas pressure rose to the right value, which was around two inches of water
pressure. Because of changes in ground level atmospheric temperature and pressure the ballonet had to expand and contract when the Cyclocrane was on the mast or in the hangar too. One day, in the summer of 1984 while the balloon was in the hangar one of us was working on the ballonet winch at the end of the day and neglected to release the brake. During the night the temperature in the hangar dropped and the gas in the hull contracted. The system did what it was supposed to and turned on the fans but with the brake engaged the ballonet volume couldn’t increase and the fans stayed on until the ballonet fabric couldn’t take it and it tore. The next morning the guy who had left the brake on returned to continue what he had been doing the previous day. When he opened the door to the cab helium poured out. It took him just seconds to realize what had happened. I was on the hangar floor so he called down to me in the Mickey Mouse voice that a lung full of helium produces. Chris and I put Scott Air Packs on and went inside to see how bad the damage was and found that there was a twenty-four foot tear in the ballonet about fifty feet from the front of the balloon. The forward cab housed the telemetry gear that transitioned all the control and data paths from the non-rotating systems to the rotating ones. In the first Cyclocrane it was done with slip rings which was less reliable and much heavier than radio gear. (The opportunity to re-do that aspect of the ship actually made the crash a fortunate accident.) It also carried batteries, the components that transfered the fuel between the rotating and fixed systems and the ballonet winch and blowers. All this gear, the structural components and the bulkhead at the back of the cab made this space hard to traverse and it was real hard to move through
with breathing equipment. After Chris and I looked things over and briefed Dad on what was wrong and what we had to do we gathered everything we needed and started to bring it inside the ballonet. At the rate that gas was pouring out of the balloon, and air was contaminating what was left, we didn’t have long to get it done before it would be too late. First we had to let the balloon rise and rotate it to get the tear on the bottom. Then Chris went in to secure bosun’s chairs so he and I and Steve could first tape the tear to stop the flow and then patch the rip. As Chris was moving toward the front of the balloon, carefully picking his steps on the eight inch diameter tube that was the ship’s spine, the alarm sounded on his Air Pack. It’s a bell that rings at a low frequency, just a few dings per second, and it sounds like the bell they put at the counter at the post office or bakery. We didn’t use the Air Packs much. There is little need to get inside the helium chamber and although we had some experience with them none of us had used them to the point that the alarm sounded. Chris knew that the alarm indicated that the air in the tank was getting low and he needed to get out but there shouldn’t have been a need to hurry and risk falling, so he didn’t. He just kept on moving forward as he had been. I was on the platform outside and when I heard the bell I called to Chris and he confirmed that he was coming out. I couldn’t hear him very well because of the face piece but I understood that he was near the front of the balloon and making his way to the exit. About a minute later I heard him call for help, and it was in the squeaky, Mickey Mouse voice that’s so funny at birthday parties. It wasn’t funny then and hasn’t been funny to me since. My Air Pack was on my back and ready to go
so I quickly put on the face piece and went into the cab to find Chris lying on the floor and halfway out of the hatch in the aft bulkhead. He had run out or air before he got to the hatch and by the time he managed to make his way through all the struts and rigging he didn’t have enough to make it through the hatch. By calling for help, with helium instead of air flowing from his lungs, he may have saved himself. He was unconscious so I pulled his face piece off, opened the valve on my Air Pack, took a deep breath and held it then put my mask over his face. His eyes were open and glassy which scared me. My fear for him overcame me and I exhaled so about the time that Chris came to and his eyes looked normal I passed out. Luckily I fell toward the outside door so my head was where there was some air. It had a lot of helium in it but there was enough oxygen that I woke up pretty quickly. I went back for Chris and did the same thing again! He woke up, his eyes cleared, I passed out and we were right back where we were. By then Steve and others had climbed the mast and were there to pull us out. I woke up the third time on the platform with
inside safely for even half-an-hour. Chris and Steve and I didn’t want to give up and Dad didn’t really want to either so we decided to rent SCUBA gear and go back in. Once again someone in Tillamook came to the rescue and supplied a Hookah system. It’s an air compressor with hoses and respirators for scuba diving. It was set up and operating in time for us to get back inside and tape the tear before we lost too much gas. We lost a lot and it was a very expensive screw-up but we were able to stop the leak and replace what was lost before it was too late. For five long days, twelve to fourteen hours each, with respirators in our mouths, hanging in harnesses and sitting in bosun’s chairs we brushed and wiped thin fabric suspended in space with Methtyl Ethyl Ketone and adhesive. Finally the repair was done and we were pretty proud of ourselves. By October of 1984 we were ready to go again and on the 15th we flew it for the first time. I was aboard as co-pilot. J.J. Morris a retired US Army helicopter was the pilot. Bill Giordano and Dad were flight engineers. I think Dad let me come along as a reward or as something for he and I to share which I’m grateful for but I didn’t fly in the Cyclocrane again. There were several more flights in the next couple of months. Dad, Bill and J.J. were the crew on all of them and when that first phase was finally through we had logged about five hours of flight time. I shot most of the video which was a pretty important outcome since what we were primarily trying to do then was raise more money. The video was proof that we had something that worked. I thought we were really on our way to founding an industry. In the winter of 1985 Dad worked very hard looking for more money and I went to a few cities around the country with video and called on the local television stations. I managed to be interviewed at
October 15, 1984 everyone else but I thought that Chris was still inside so I got up and tried to stumble back in. Steve stopped me. When Dad found out what happened he was ready to call it off. Fixing the leak was going to take days and with the equipment we had we couldn’t stay
stations in Seattle, Philadelphia and New York but by March the additional backers were still missing. In the time between the crash and the rebuild the company that Dad formed to develop the Cyclocrane, Aerolift, Incorporated had gone public so there was a board of directors and stockholders. When the money from the insurance, the public offering and a US Forest Service contract ran out Dad and the board disagreed on where to direct the marketing and fundraising efforts. By then Dad and others had pursued potential sources all over the world and Dad felt strongly that the only hope was the United States Government, either the Department of Defense or the Forest Service. The Canadian members of the board insisted on soliciting Canadian sources. That proved to be a fundamental and irreconcilable difference so Dad got out and so did I. The new managers did manage to get another grant or contract and it was with the U.S. government, as Dad knew it would be. They flew the Cylcocrane a few more times after the initial series of tests and did a little more research and development but there was no more work on the Cyclocrane after 1989.
THE CYCLOCRANE CONCEPT A “hybrid airship” uses two forms of lift; aerostatic and aerodynamic, or buoyancy from gas that is lighter than air and lift from aerodynamic surfaces like wings and rotors. In the Cyclocrane the lighter than air gas, which was either helium or a helium and hydrogen mixture, carried the weight of the aircraft, including fluids and crew, and half the payload. The wings on the ends of the blades generated the lift needed to either carry the rest of the payload or to hold the airship down if it was unloaded. In a two ton slingload Cyclocrane, for example, the lifting gas would lift the weight of the vehicle, fluids and crew and one ton of payload. The airfoils would produce one ton of force to either lift one ton of payload or to hold the ship down against one ton of buoyancy when the payload was released. Flights begin with the airship either attached to the slingload, or tethered, and allowed to rise until the net buoyancy is transfered to the tether or the load. The “stalk”, which is the assembly the engine is mounted on, that is hanging beneath the aerostat (the gas bag) is pointed forward and the engine started. Once the engine is warmed up and running at full power that stalk is rotated ninety degrees. The thrust generated by that engine starts the airship center body into rotation. After a revolution or two centrifugal force is adequate to keep the oil in the engines out of the oil pans and at that point the other engine, or engines, are started. When the rate of rotation (in the two ton slingload Cyclocrane) reaches thirteen revolutions per minute the relative wind over the “wings”, which are the airfoils on the ends of the “blades”, is sixty-milesper-hour. That airspeed is sufficient to create the lift needed to lift one ton, if the airship is loaded, or to hold the ship down against one ton of buoyancy if it isn’t. To fly to his destination the pilot executes a cyclic command to the wings that causes them to change their orientation through each revolution to either lift the load or counteract the aerostatic lift. Once hovering at the desired altitude a collective command on the blades points them into the direction of flight, causing them to function as propeller blades and pulling the airship forward (or backward). This forward velocity component allows for a reduction in the rate of rotation to maintain the necessary sixty-mile-perhour relative wind over the wings.
The result of this mixing of velocity components means that the path that the wings trace through the air as the ship reaches full forward flight is a helix, the rotation rate decreases as the horizontal speed increases and at full forward flight the ship is no longer rotating. To release the load or to moor the airship the process is reversed. The stalks are gradually rotated in the opposite direction causing them to act as a propeller again to take the ship back into rotation and hover. The load is then released and the ship can return for another load or if the ship is to be moored it can be secured to a tether or mast.