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36 An airship is an engine-driven LTA aircraft that can be steered. Airships can be rigid or non-rigid, with blimps the common example of a non-rigid airship. A rigid airship has an internal structural framework that forms its shape and that contains compartments or bags of LTA gas, whereas a non- rigid blimpâs form is maintained by the LTA gas envelope. If a rigid airship deflates, its shape remains the same. If a blimp deflates, it loses its shape. Blimps are the main form of airships seen in the United States. They are used primarily for commercial promotion and advertising, and as platforms for televising sporting and specialty events. One main airship operator is currently converting its blimp fleet to rigid airships. AIRSPACE ACCOMMODATION Owing to limited maneuverability, airships do not normally fly a standard traffic pattern. A blimp has the right-of-way over an airplane or rotorcraft. It does not have the right-of way over an aircraft in distress, a balloon, or a glider. An airshipâs size makes it easy to see and avoid. Airships are susceptible to weather conditions, especially wind, ice, and snow. As the airship slows to approach a mooring, wind can create an unsafe condition resulting from an airshipâs inherent lack of low-speed controllability. An airship requires a clear approach into any wind direction, for safety purposes. A flat surface, unobstructed approaches, and the ability to dock and move 360 degrees with prevailing winds are other needs for successful mooring. Ice and snow are concerns because they add weight to the blimp that can significantly reduce its lifting capabilities. AIRPORT ACCOMMODATION Airships tend to be infrequent visitors to airports, because their commercial use, appearance schedules, route of flight, and operational needs require preplanning by airship operators. The specific routes and the airports used for stopovers are normally vetted beforehand. Because of their mooring needs, an airship operator will visit an airport manager a week or more in advance of movement to survey the airport as a potential landing site. Some airports have received an unexpected visit when weather conditions make the stop a prudent choice. When conducting a site assessment, a blimp operator pri- marily considers the local topography, soil conditions, weather conditions, and the mooring method to be used. Figure 9 illustrates a typical mooring position away from the taxiway and runway with a large open area for approach, departure and mooring, and staging area for blimp crewmembers. There are four mooring methods: bow mooring, belly mooring, complete vehicle (total) restraint, and hangars. Bow mooring is the typical method of restraint when the airship is away from its home base. Figure 10 illustrates a bow mooring and the various cable stakes secured into the ground. At its home base, a hangar is the norm for housing an airship, although initial capture uses a bow or belly mooring process. Bow mooring allows the aircraft to swivel with the wind, but it requires a 360-degree movement area on the ground. An airship typically has a ground/support crew of 13 to 17 people. They travel with vehicles that contain support equipment and supplies, such as ground power units. If the airport is selected as a chapter seven AIRSHIPS
37 landing facility, the crew requires access to the airport. It can take several hours to complete a set-up or tear down. A newly designed truck vehicle for a rigid airship has an integral mast that can support and move the airship as needed. It can operate on pavement, if the ground will not support the truck. Most accidents and incidents related to airships are associated with ground crew mishaps. NOTICES TO AIRMEN Typical NOTAMs issued for a blimp or airship moored at an airport contain information on where it is located on the airport; its distance from a runway, taxiway, or approach/departure path; its height; whether it is lighted or illuminated for night or instrument meteorological conditions; the presence of persons and or vehicles in the vicinity; line of sight issues; and operational status of any affected navigational aids. FIGURE 9 Blimp positioned and moored away from aircraft movement areas (Credit: S. Quilty, SMQ Airport Services, Lutz, Florida. Used with permission.). FIGURE 10 Blimp moored at the bow (Credit: S. Walsh, Lakeland Linder Regional Airport, Florida. Used with permission.).
38 RELATED INFORMATION Weather, aircraft size, maneuvering area, crew access, and public attraction are concerns of airport operators accommodating airships. Persistent bad weather can result in an airship staying moored at an airport for a long period of time. The size and height of an airship can penetrate safety surfaces surround an airport and its runways. If a surface is penetrated, a NOTAM is issued. Consideration needs to be given to a moored airship interfering with navigational or weather aids. If moored overnight, FAA requires that the airship be lighted in some way. Portable generators usually accompany the crew, and power flood lamps. The airport managers surveyed indicated the blimp operator normally stations at least one crew- member with the blimp at all times, including an overnight watch. One airport manager described how he accommodated a blimp by placing it on a crosswind run- way, requiring closure of the runway. Bad weather arrived, preventing the airship from departing. The bad weather also brought winds requiring the use of the crosswind runway for aircraft, however, the blimp prevented the runwayâs use. A lesson learned. Another airport manager related how an airship crew was quite nervous about a local community test of its tornado sirens. The crew rushed to the airport thinking they would need to deflate the blimpâan expensive proposition. Blimps use helium for their LTA capabilities. Helium does not present a significant safety hazard, as it is an inert gas. The problem with helium is its availability. Once deflated at a remote site, the scarcity of helium to re-inflate the blimp can cause a lengthy delay. As certificated aircraft, the current blimp fleet use certificated piston engines and avgas fuel. Emergency response personnel need to be familiar with emergency egress hatches and the operation of the fuel system and gas bag releases. With the exception of one airport, which charged a nominal five-dollar overnight fee for all aircraft, airport managers interviewed for this report did not charge a blimp for other services. A concern expressed by one airport operator was the amount of foot and drive-through traffic a blimp generates from people sightseeing. Normal parking lot and perimeter roads can become clogged with traffic and present security concerns.
