|
GLOBAL HILTON N298AR BAIL OUT DECISION Submitted by: Richard G. "Dick" Rutan (USAF Lt. Col. ret) Commander, Global Hilton THE GLOBAL HILTON SYSTEM The Global Hilton system used last winter consisted of a single 170 foot tall Roziere balloon envelope with a 420,000 cubic foot helium cell. The two-member crew capsule was a highly insulated, 8 foot diameter pressurized carbon fiber sphere with a "closed loop cycle" life support system. Aboard the craft were life support consumables for 18 days. THE FLIGHT The launch site selection was the Balloon Fiesta Park in Albuquerque, New Mexico. This is the site of the largest annual balloon event in the world, and seemed a fitting launch site for the first ever balloon flight around the world. When the weather conditions proved suitable at 0300 on January 9, 1998, the helium was pumped into the envelope. About 45% of the 420,000 cubic feet of helium was required to lift the 12,000 pound balloon into the cold, dark New Mexico sky. During ascent, the helium would expand to fill the total volume at about 28,000 feet, which was our initial float altitude. THE PILOT NARRATIVE The balloon (Global Hilton N298AR) was launched at 0618 MST on January 9, 1998 from Albuquerque, New Mexico, approximately ten miles north of the Albuquerque International Airport (KABQ). The lift off and climb was as per the normal profile averaging 263 feet per minute. Dave Melton, who was flying the Global Hilton at the time, eased into a float altitude (with a fully inflated envelope) of 27,500 and flew level for twelve minutes. Then suddenly, with a loud "whoosh" and a mild bounce (cell rupture), the balloon climbed to 32,200 feet and leveled off. This climb after rupture is a result of the expanding helium being able to distend into the hot air cell below. A MAYDAY emergency call was made on the Air Traffic Control (ATC) frequency and as helium escaped through tears in the fabric, the balloon began to descend. The pilots looked up through the capsule's top hatch and saw a massive catastrophic rupture of the helium gas cell's lower membrane. It is important to note that the failure was not just with the lower portion of the helium gas cell membrane, but there were radial vertical tears that had begun to extend up into the top of the envelope itself. This tearing continued sporadically until crew bail out. Fortunately, the descent was slow and the rising sun heating the helium countered the leaking. At 12,000 feet, the capsule was de-pressurized, the hatch was removed, and photos of the failure were taken. The crew considered landing in the heavyweight condition, which would have been a challenge under ideal circumstances. At the time, however, with tons of propane and liquid oxygen on board, a heavyweight , emergency landing grew increasingly problematic because of the high surface winds that were being reported by the ground crew ahead of the balloon track. The surface winds were forecast to become stronger as the day and eastward track continued. A Roziere gas balloon system with a lower membrane rupture could conceivably be flown at low altitude for days. However, during the descent to a lower altitude, there were continuous pops, creaks and tearing sounds in the envelope structure. There was one specifically loud crack/ripping sound while passing 22,000 feet that immediately resulted in a rapid rotation of the balloon. This indicated a helium leak in the upper portion of the envelope that presented immediate concern. At that time, the structural integrity of the envelope was in serious question. Should the vertical tearing continue into the upper section, all of the helium would be lost and the balloon system (envelope and capsule) would "streamer in" with little or no chance to egress. The pilots evaluated this to mean the vertical tearing was progressing high enough into the envelope to allow helium to escape, that caused the rotation. Weight reduction was not a viable option, for it could have taken the rest of the day to jettison propane and valve off helium, the validity of that plan was not promising. That rejected plan, coupled with the ever-increasing surface winds, led to the decision to abandon the balloon. The abandonment decision was not made until there was an extensive evaluation by the ground team and crew of the sparsely populated area of eastern New Mexico, until the forecast for the ever increasing surface winds was studied, and until the integral structural degradation of the balloon envelope itself was determined. It was then that the decision was collectively made to bail out. Back inside the capsule, the pilots helped each other put their parachutes on, inspected each other's chute, and practiced pulling the ripcord. The pilots then assisted each other up through the hatch and out of the capsule. While standing outside on top of the propane tanks, Rutan pulled the envelope's manual helium valve rope, opening the helium valve and then securely tied it off to the capsule load ring to insure the balloon would impact in this same remote area of New Mexico, not far from where the pilots would land. After the bail out, the balloon did descend into a remote area downwind and east of where the pilots landed. The uncontrolled impact was severe, ripping half of the propane tanks (it is believed to be eleven) from the capsule. With such an immediate loss of ballast (weight), the balloon to shot back into the sky. After a few more hard landings that shed even more tanks, the balloon made its final landing twelve hours later in a remote area northwest of Gainesville, Texas. There was a power line strike, causing sparks to ignite the remaining propane, which was totally destroyed the capsule. The envelope was pulled away free of the capsule by the same power lines and was recovered about three miles from the capsule resting site. The envelope was returned to Albuquerque, where the National Transportation Safety Board (NTSB) and the Federal Aviation Administration (FAA) are conducting a thorough investigation concerning the structure failure of the balloon envelope. A formal report of their findings is expected from both of these agencies. POST SCRIPT Global Hilton Pilot, Dave Melton, suffered a serious hip injury during the high surface wind parachute landing (he has since recovered). Global Hilton Commander, Dick Rutan, survived the high wind landing with minor injuries from a Choya cactus patch. LESSONS LEARNED During the post flight team debriefing, the main questions were, "Did we make the correct decision to bail out?" "Was our decision making process prudent?" "Did we have the right people to access the information (technical, weather, communication)?" "Did we explore all possible scenarios and select the proper one?" The foremost concern was the structural integrity of the envelope and every indication was that the envelope was continuing to deteriorate and was the basis on which the team confidently made the bail out decision. Area for Improvement 1. Fatigue. The emergency action team members were also directly involved with the launch. All team members had been awake most of the day and all of the night before. Only the two air crew members were able to get about two hours of sleep just before the pre-dawn take off. Most everyone optimistically anticipated that any challenge would not occur until perhaps weeks later when the craft was half way or more around the world; never immediately following take off. 2. Communications. This was a critical item in the team concept of emergency action. The ground team recognized that direct VHF communication with the balloon would soon be lost, so a discrete frequency was requested through Albuquerque Air Traffic Control. Consequently, the air crew was never out of direct voice link with the ground control. 3. Derelict Balloon. Our failure to insure a positive, safe termination of the balloon after bail out was a major deficiency requiring corrective action. Although the air crew opened the helium control valve prior to capsule departure, the now unmanned balloon descended and impacted in a remote area of eastern New Mexico, but it did not stay on the ground. On impact, half of the propane tanks broke away and the balloon rebounded back into the air. A positive termination device is required. One method would be a position activating rip out panel to dump helium once the crew bails out. 4. Emergency Procedures. An emergency procedure was never developed to handle a heavy weight, high surface wind landing right after launch. The situation was considered, but determined to be so remote that specific procedures were never formulated. The team was well aware long before the flight that this was the "dooms day" scenario and there was no practical method of dealing with it. As fate would have it, the team was faced with the worst of all imagined situations and had to deal with it tired and fatigued. REFLECTIONS One frequently asked question (mostly from fighter pilots) has been, "Why not jettison all of the tanks and land?" Each one of the 20 propane tanks weighs 350 pounds. When a tank is released, it sends a jolt, or a shock wave, up through the balloon. After the rupture, the air crew continued to hear pops, ripping and tearing noises and was very reluctant to jolt the envelope and precipitate a full envelope failure by attempting to jettison tanks and face the possibility of streamering in. The pilot controlled helium valve is adequate for normal maneuvering, but not large enough to vent/dump helium fast enough to counter the release of full tanks. If this cause of action was chosen, it would have taken most of the remaining daylight hours. The balloon would have had to wait until the next day to land and by then, it could have been over the Atlantic Ocean. The procedure would have been to open and leave open the helium valve, wait until the balloon developed a healthy rate of descent, and then jettison one tank. Relieved of the weight, the balloon would start to climb, even with the helium valve opened, it would take some time to stop the climb and begin a descent. Then the next tank would have been jettisoned, the ultimate long period phugoid. This would take the rest of the day to jettison the tanks, Lox Dewars, crew food, water, etc. to reduce weight for landing. Had we jettisoned all of the tanks, etc. at once, the balloon could have shot up to well above 50,000 feet. CONCLUSION The only course of action was to abandon the balloon. The fact that the helium envelope structurally survived the initial impact, popped back to 30,000 feet, descended back to the earth and skipped across north Texas before coming to rest on some power lines may have suggested the envelope was not on the ragged edge of failure, and a faulty bail out decision was made. However, to recover/land the balloon in it's heavy weight state, even in calm winds, with all of the propane tanks was a hazardous proposition at best. Most all of the propane tanks did fail, releasing volatile clouds of propane, that ultimately fueled the fire. In high winds, it was less than acceptable risk. Will we try again? It's been said that "the tougher the climb, the better the view." Remember, you only fail if you quit. |