Abstract: An aircraft comprises an aircraft body, and apparatus, carried by the body, for discharging a persistent vapor of bird repellant into an elevated airspace.

Abstract: A gatebox for an aircraft comprises an opening operable to allow material to flow out of the gatebox, a hopper operable to direct material in the gatebox to the opening, a door coupled to the hopper and operable to move between an open position and a closed position by sliding along a surface of the gatebox, wherein the door comprises a front edge, a rear edge wider than the front edge, and at least two side edges that taper between the front edge and the rear edge, and a seal coupled to the hopper and operable to, when the door is in the closed position, engage the edges of the door and compress to prevent material in the gatebox from being released through the opening along the engaged edge of the door.

Abstract: A system for simulating wet runway conditions by using a liquid container that is placed inside an aircraft. The liquid container is connected to a nozzle that sprays water in front of the wheels of the aircraft. A valve is used to control the flow of water from the nozzle. Systems, such as the braking system of the aircraft, can then be tested in wet runway conditions simulated by the system. The amount of water sprayed from the nozzle can also be electronically controlled in relation to the speed of the aircraft, such that the nozzle sprays a nearly uniform layer of liquid in front of the wheels. The system can also be modified to include two tanks to manipulate the center of gravity of the aircraft.

Abstract: A system for airborne transport of flammable liquids with an aircraft. A fuel tank and a reservoir, each for storing flammable liquids, are joined to the aircraft. A fuel jettison subsystem is coupled between an interior portion and an exterior of the reservoir to selectably expel fuel from the reservoir to an exterior portion of the aircraft. The fuel jettison subsystem includes a jettison valve opening formed in the reservoir. A lid selectably closes off the opening. A biasing member urges the lid away from the jettison valve opening. A solenoid retains the lid in the jettison valve opening when unactuated and releases the lid when actuated. A jettison linkage is coupled to the solenoid, the jettison linkage being operable to actuate the solenoid. The lid is urged away from the jettison valve opening by the biasing member when the solenoid is actuated by the jettison linkage.

Abstract: A system for affixing a gatebox to an aircraft includes a first type of gatebox operable to release material from an aircraft, a second type of gatebox operable to release material from the aircraft, a frame coupled to the aircraft operable to receive a selected one of the first type of gatebox and the second type of gatebox; and a plurality of fastenings operable to secure the selected one of the first type of gatebox and the second type of gatebox to the frame.

Abstract: An aerial retardant delivery system comprising a retardant tank mountable in the fuselage of an aircraft. The tank includes a pressure opening in fluid communication with the fuselage such that pressure in the fuselage may act on retardant contained in the tank. The tank includes an outlet extending through a sidewall of the aircraft's fuselage, through which retardant may be delivered to a target. The system also includes a discharge gate operative to open and close the outlet. An actuation mechanism is disposed on the exterior of the tank and operatively coupled to the at least one discharge gate. A variable flow controller controls the discharge gate open position in order to provide retardant over a desired area of terrain. A one-way flapper is disposed in the pressure opening and is operative to allow pressure in the fuselage to enter the tank while inhibiting retardant from spilling from the tank.

Abstract: A system for affixing a gatebox to an aircraft includes a first type of gatebox operable to release material from an aircraft, a second type of gatebox operable to release material from the aircraft, a frame coupled to the aircraft operable to receive a selected one of the first type of gatebox and the second type of gatebox; and a plurality of fastenings operable to secure the selected one of the first type of gatebox and the second type of gatebox to the frame.

Abstract: A control system is disclosed for use with a machine having a work tool and operating at a work site. The control system may have a sensor associated with the work tool and configured to generate a signal indicative of a position of the work tool, an offboard worksite controller, and an onboard controller in communication with the sensor and the offboard worksite controller. The onboard controller may be configured to receive from an operator an input indicative of a current task being performed by the machine, and track movement of a portion of the work tool corresponding with the operator input. The onboard controller may also be configured to communicate the tracked movement to the offboard worksite controller.

Abstract: A method of reducing the amount of water in a region of air including: forming seed ice crystals; dispensing the seed ice crystals towards the region of air; allowing water in the region of air to freeze or deposit onto the seed ice crystals; and allowing the resulting ice crystals to move from the region of air so as to reduce the amount of water in the region of air. An ice crystal seeding assembly arranged to reduce the amount of water in a region of air, the seeding assembly includes an ice crystal seeder and dispensing means, the dispensing means being arranged to dispense seeded ice crystals towards the region of air so that water in the region of air freezes or deposits onto the seed ice crystals and that the resulting ice crystals move from the region of air.

Abstract: A drainage mast (13) for draining liquids from an APU compartment (11) of an aircraft with a first end (15) connected to the APU compartment (11) and a second end (17) for discharging said liquids to the atmosphere. The drainage mast (13) is configured with at least a sector having decreasing cross section areas towards the second end (17). The area of the initial cross section of said sector is lesser than the area of any cross section of the drainage mast (13) closer to the first end (15). The invention also refers to an aircraft comprising the drainage mast (13).

Abstract: A method for launching counter-measures from a launch opening of a dispenser mounted on an aeroplane. The counter-measures are launched in a direction obliquely forwards and downwards relative to the aeroplane. In order to facilitate launching of counter-measures, a low dynamic pressure is created permanently across the launch opening of the dispenser by a fixed element acting on the air stream. An arrangement for storing and launching counter-measures including an elongate body provided with at least one launch opening used for storing the counter-measures in compartments. The arrangement is designed to be mounted on an aeroplane with the longitudinal direction of the elongate body essentially coinciding with the flight direction of the aeroplane. The counter-measures are connected to a firing control unit for feeding firing signals to the counter-measures. The arrangement is designed to be mounted under the aeroplane.

Abstract: An aircraft chaff dispenser includes an elongated hollow housing intended to be fixed to the structure of the aircraft so as to be oriented in the longitudinal direction of the aircraft. The housing has a pair of side walls and the front of each side wall is provided with a pair of lateral air intakes each having a circular through-hole with a diameter d and a fence located behind the hole in the longitudinal direction, or in the direction of travel, of the aircraft at a distance 1 from the center of the hole and having a shape in the form of a horizontally lying V with its vertex directed away from the hole. The diameter d of the hole is between 8 and 12 mm. The ratio h/1 between the height h of the fence at the vertex of the V and the distance 1 is between 0.8 and 1, while the ratio h/d between the height h and the diameter d is between 1.5 and 2.

Abstract: According to certain embodiments, an aerial delivery system configured to be deployed from an aircraft comprises a base, a sleeve generally configured to be positioned on the base, a bag configured to receive at least one liquid and a lid assembly attached to the bag using at least one strap. In some embodiments, the strap is attached to the bag in a manner that causes the bag to be selectively compromised once the aerial delivery system is deployed from an aircraft. In one embodiment, the system comprises a cellulose-based material. In other arrangements, the bag comprises polypropylene.

Abstract: According to certain embodiments, an aerial delivery system configured to be deployed from an aircraft comprises a base, a sleeve generally configured to be positioned on the base, a bag configured to receive at least one liquid and a lid assembly attached to the bag using at least one strap. In some embodiments, the strap is attached to the bag in a manner that causes the bag to be selectively compromised once the aerial delivery system is deployed from an aircraft. In one embodiment, the system comprises a cellulose-based material. In other arrangements, the bag comprises polypropylene.

Abstract: Firefighting bucket (11) suspended from an aircraft by lines (15), has open top (12A) and a valve at base (13). The valve is attachable to the aircraft by remotely actuatable line (16) and independent movement of lines (15-16) may utilize the weight of the water to facilitate opening and closing of the valve. Dynamic sensing of a bucket attribute, e.g. weight, enables bucket (11) to be filled or discharged by a pre-determined volume by the pilot. Chemical fire retardant may be added by entraining it with water discharging from the valve.

Abstract: A system for airborne transport of flammable liquids with an aircraft. A fuel tank and a reservoir, each for storing flammable liquids, are joined to the aircraft. A fuel jettison subsystem is coupled between an interior portion and an exterior of the reservoir to selectably expel fuel from the reservoir to an exterior portion of the aircraft. The fuel jettison subsystem includes a jettison valve opening formed in the reservoir. A lid selectably closes off the opening. A biasing member urges the lid away from the jettison valve opening. A solenoid retains the lid in the jettison valve opening when unactuated and releases the lid when actuated. A jettison linkage is coupled to the solenoid, the jettison linkage being operable to actuate the solenoid. The lid is urged away from the jettison valve opening by the biasing member when the solenoid is actuated by the jettison linkage.

Abstract: An aircraft hull attachment device may be configured for attachment to a fuselage of an aircraft. The aircraft hull attachment device can include one or more floats to enable the aircraft to operate on water. The aircraft hull attachment device can also include a structure such as, for example, a saddle-shaped structure, for mounting the device against a bottom region of a fuselage of the aircraft. Upon being operatively coupled to the aircraft, the aircraft hull attachment device can convert an aircraft previously configured to operate only on ground landing strips into an aircraft configured to operate on water landing strips. Additionally or alternatively, the device can include a water tank and a water-tank door to enable the aircraft to which the device is mounted to perform in-flight water drops (e.g., during fire fighting aerial operations).

Abstract: A control system for transferring fluid between a fluid supply and a process. The control system includes a transfer controller, which outputs a transfer signal that corresponds to a time varying fluid transfer rate, and plural valves that are plumbed in parallel for connection between the fluid supply and the process. Each valve has a corresponding input to receive an actuation signal that enables a closed state or an open state. The system also includes plural means for limiting the rate of fluid flow corresponding to the plural valves, and a valve drive that is coupled to the corresponding inputs of the plural valves, which operates to generate a sequences of valve actuation signals that result in a combined fluid flow rate through the plural valves selected to track the time varying fluid transfer rate defined by a modulated transfer signal within a margin of error.

Abstract: A system for airborne transport of flammable liquids with an aircraft. A fuel tank and a reservoir, each for storing flammable liquids, are joined to the aircraft. A fuel jettison subsystem is coupled between an interior portion and an exterior of the reservoir to selectably expel fuel from the reservoir to an exterior portion of the aircraft. The fuel jettison subsystem includes a jettison valve opening formed in the reservoir. A lid selectably closes off the opening. A biasing member urges the lid away from the jettison valve opening. A solenoid retains the lid in the jettison valve opening when unactuated and releases the lid when actuated. A jettison linkage is coupled to the solenoid, the jettison linkage being operable to actuate the solenoid. The t lid is urged away from the jettison valve opening by the biasing member when the t solenoid is actuated by the jettison linkage.

Abstract: A gas turbine engine has a nacelle, a plurality of pipes and a drains assembly, the drains assembly including a drains mast that extends through the nacelle and provides an outlet for the pipes. The engine is characterised in that drains assembly has a connection block defining internal passages and is arranged to connect between the pipes and the drains mast. The connection block also has lateral connections to the pipes enabling the nacelle to have a lower profile; thereby reducing aerodynamic drag.

Abstract: The invention relates to a deflector for an aircraft, comprising a discharge pipe for leading a fluid to be drained from the aircraft by way of an outlet end to the environment of the aircraft; an actuator, coupled to the discharge pipe, for swinging out, when required, the discharge pipe to at least one activation position, wherein in the activation position the outlet end is arranged so as to be spaced apart from the exterior skin of the aircraft, and the deflector guides the fluid to be drained so that it exits outside a flow boundary layer that is present on the exterior skin. The deflector according to the invention is activated when required and is able to discharge structure-damaging fluids to the environment in such a way that the exterior structure of the aircraft does not become wet, and at the same time the deflector according to the invention, normally accommodated within the contour of the aircraft, does not result in any additional aerodynamic resistance.

Abstract: According to certain embodiments, an aerial delivery system configured to be deployed from an aircraft comprises a base, a sleeve generally configured to be positioned on the base, a bag configured to receive at least one liquid and a lid assembly attached to the bag using at least one strap. In some embodiments, the strap is attached to the bag in a manner that causes the bag to be selectively compromised once the aerial delivery system is deployed from an aircraft. In one embodiment, the system comprises a cellulose-based material. In other arrangements, the bag comprises polypropylene.

Abstract: A drainmast (200) comprises an exit-defining foot (300), entrance-defining draintubes (400,500), a heater (600), and a fairing (700). The heater (600) heats the draintubes (400,500) to prevent water from freezing therein and heats the foot (300) to prevent ice from accumulating thereon. The foot (300) incorporates fluid-steering features to efficiently and effectively discharge drain water into the airstream (A).

Abstract: A system for delivering cooling water to building roofs by means of drone aircraft is disclosed. Control systems for navigation and precisely targeting a water spray are disclosed.

Abstract: Embodiments of methods, apparatuses, and systems associated with producing and distributing one or more radiative forcing agents to Earth's atmosphere are disclosed.

Abstract: An aerial distribution system includes a fluid distribution head having at least one head fluid inlet in fluid communication with a fluid source, and at least one head fluid outlet. The fluid distribution head is reconfigurable between a deployed position and a collapsed position. The aerial distribution system further includes a suspension assembly for suspending the fluid distribution head from an aerial lift system, and a deployment assembly coupled to the fluid distribution head and actuatable to reconfigure the fluid distribution head between the deployed position and the collapsed position.

Abstract: A countermeasure arrangement including a countermeasure dispenser. An envelope at least partly encloses the countermeasure dispenser. A first control module is configured to control the countermeasure dispenser. A suspension module is arranged on the envelope for suspending the envelope on an aircraft. The suspension module has a form and a design that substantially correspond to the form and design of a suspension rail of a missile, so that the suspension module mates to a hard point on the aircraft, which is adapted to the missile.

Abstract: A system for launching, controlling and delivering in a preselected target pattern a plurality of low-cost, guided fire-retardant-containing vehicles, i.e., “smart water bombs” equipped with control surfaces sufficient to provide limited lift and maneuverability to respond to guidance command to place it at a selected GPS coordinate within a large footprint in time and space and to discharge its payload of fire retardant at a preselectable altitude in a very precise manner and dispersion pattern. A controller determines bombing patterns and timing for all bombs and trajectories for each guided bomb. Dynamic differential equations are used to determine location and time of release of the guided bombs to achieve the target while avoiding collisions among guided bombs and aircraft.

Abstract: An air guide for a dispenser. At least one air scoop is configured to guide an air stream to a feeding out opening for chaffs on the dispenser in order to facilitate packages of chaffs to be released from the dispenser. A control unit is configured to control the air stream through the at least one air scoop.

Abstract: A method and system for allowing unsafe action signals in a dispensing system of a vehicle. A discharging signalling system of at least one dispenser of a vehicle includes an activation circuit arranged to discharge the dispenser. An indicator is arranged to indicate that dispensing is allowed. The activation circuit includes a first safety arrangement arranged to be activated when an indication from the indicator indicates that dispensing is allowed. The activation circuit also includes a second safety arrangement arranged to be activated when a discharge of the dispenser is indicated.

Abstract: In accordance with the present invention, there is provided a deployment device that is operative to deploy Special Material (SM) to protect the vehicle when an enemy infrared (IR) threat is present. The deployment device constructed in accordance with the present invention comprises at least one, and preferably a pair of canisters which are each filled or loaded with SM, then factory sealed to prevent oxidation or contamination. Each of the canisters included in the deployment device includes an input shaft which, when rotated, is operative to transmit the rotary motion to each of four threaded rods. The rods have two primary functions, which are to advance a piston thereby preloading the SM within the canister toward the open end thereof, and to turn rotary metering devices which are located at the open end of the canister. The advancing piston maintains consistent compression in the SM stack within the canister.

Abstract: The invention relates to a device (1) for receiving liquids in an aircraft and/or releasing liquids therefrom, especially during the flight, said device being arranged especially in an airplane. The aim of the invention is to provide a device which can receive large quantities of liquids in a rapid, reliable and flexible manner.

Abstract: The lighter-than-air vehicle for shading is an airborne, movable system that provides shade from the sun for an open area. The vehicle is a substantially flat flying device having upper and lower surfaces, and which is filled with a lighter-than-air gas or gases, such as helium or hydrogen. The vehicle may be tethered to the ground through control wires, or may be fully autonomous and controlled by propeller fans. The required power may be provided by wire from ground, or through a portable power source, such as solar cells, mounted atop of vehicle. The vehicle has sun sensors that allow it to track the sun, and provides around the clock shaded area underneath its surface. The vehicle can also have pressure sensors and altitude sensors that may trigger an alarm in case of an emergency descent to the ground.

Abstract: An enhanced aerial delivery system addresses issues raised when large quantities of fluids, powders, and other agent materials are to be transported in and aerially dispersed by aircraft. Some aspects include positioning and securing of tanks aboard the aircraft to facilitate management and safety of the tanks and aircraft. Other aspects address coupling of the tanks and associated piping to lessen structural effects upon the aircraft. Further aspects deal with channeling, containing, and dumping stray agent materials that have escaped from the agent tanks on board the aircraft.

Abstract: An aircraft (10) having a cabin (14) with a plurality of potable-water-using stations (22) that drain graywater to a transfer tank (24). The graywater ejection system pressurizes the transfer tank (24) at appropriate times and/or places, so that graywater can be ejected through a drainmast (26) without the help of gravity. This graywater ejection system eliminates the need for a discharge line from the transfer tank (24) and frees the aircraft's fuselage (12) from having an inconvenient port associated with such a discharge line.

Abstract: An enhanced aerial delivery system addresses issues raised when large quantities of fluids, powders, and other agent materials are to be transported in and aerially dispersed by aircraft. Some aspects include positioning and securing of tanks aboard the aircraft to facilitate management and safety of the tanks and aircraft. Other aspects address coupling of the tanks and associated piping to lessen structural effects upon the aircraft. Further aspects deal with channeling, containing, and dumping stray agent materials that have escaped from the agent tanks on board the aircraft.

Abstract: A method performed by an aircraft, the aircraft including a wing, aircraft fuel, and a whole-aircraft parachute that is coupled to the aircraft. The method comprises: deploying the whole-aircraft parachute while the aircraft is in flight; and after deploying the parachute, but before the aircraft contacts the earth or any object coupled to the earth, discharging at least a portion of the aircraft fuel from the wing of the aircraft.

Abstract: Currently, the wastewater collection tank and the freshwater tanks comprise separate containers which are each mounted individually in the pressurized area of the cabin on the structure. In the present application a water-wastewater module is described which has two tanks for disposing of feces and wastewater and a water generation unit in the form of the fuel-cell module as integral components. The module and the fuselage may advantageously be manufactured separately from one another and first have to be combined during the final mounting of the aircraft.

Abstract: A method for launching counter-measures from a launch opening of a dispenser mounted on an aeroplane. The counter-measures are launched in a direction obliquely forwards and downwards relative to the aeroplane. In order to facilitate launching of counter-measures, a low dynamic pressure is created permanently across the launch opening of the dispenser by a fixed element acting on the air stream. An arrangement for storing and launching counter-measures including an elongate body provided with at least one launch opening used for storing the counter-measures in compartments. The arrangement is designed to be mounted on an aeroplane with the longitudinal direction of the elongate body essentially coinciding with the flight direction of the aeroplane. The counter-measures are connected to a firing control unit for feeding firing signals to the counter-measures. The arrangement is designed to be mounted under the aeroplane.

Abstract: A method and apparatus for directing waste away from an aircraft contemplate a fairing having a first end and a second end; a connection flange mounted on the first end of the fairing; a drain pipe extending through the fairing from the first end to the second end; a heating element in the fairing; a vortex redirector attached to the second end of the fairing; and an air splitter and a vortex generator extending outward from the fairing. The vortex redirector and the vortex generator, along with the air splitter, manage airflow to direct waste away from the aircraft. The method may include separating airflow passing over a drain mast assembly by an air splitter; holding airflow near a surface of a fairing by a pair of vortex generators; and redirecting airflow upwards by a vortex redirector. The redirecting forces airflow into the underside of the air splitter, while increasing velocity of the airflow above the air splitter.

Abstract: A protective device and protective measure for a radar system is provided that includes an active countermeasure by using passive emitter and/or decoys. Decoys are thereby utilized that function according to the reflection principle. These decoys are thereby radiated by the vehicle's radar. The radiation reflected by the decoys in the direction of the ARM has the same characteristic as the direct radiation from the radar itself. Thus, the ARM is unable to discriminate between decoys and the actual radar.

Abstract: A rotary wing vehicle includes a body structure having an elongated tubular backbone or core, and a counter-rotating coaxial rotor system having rotors with each rotor having a separate motor to drive the rotors about a common rotor axis of rotation. The rotor system is used to move the rotary wing vehicle in directional flight.

Abstract: An aircraft chaff dispenser includes an elongated hollow housing intended to be fixed to the structure of the aircraft so as to be oriented in the longitudinal direction of the aircraft. The housing has a pair of side walls and the front of each side wall is provided with a pair of lateral air intakes each having a circular through-hole with a diameter d and a fence located behind the hole in the longitudinal direction, or in the direction of travel, of the aircraft at a distance 1 from the center of the hole and having a shape in the form of a horizontally lying V with its vertex directed away from the hole. The diameter d of the hole is between 8 and 12 mm. The ratio h/1 between the height h of the fence at the vertex of the V and the distance 1 is between 0.8 and 1, while the ratio h/d between the height h and the diameter d is between 1.5 and 2.

Abstract: A fuel jettison system which provides pilot-initiated automatic operation to jettison fuel down to a 60 minute useable fuel remaining level while the manual operation, requiring the pilot to hold down the jettison panel switch, jettisons fuel down to a 20-minute useable fuel remaining level. The pilot can interrupt jettisoning at any time. This termination sequence operates in either automatic or manual mode. The port and starboard main fuel tanks jettison fuel independently through independent shutoff valves and associated circuit logic to thereby maintain aircraft balance.

Abstract: An enhanced aerial delivery system addresses issues raised when large quantities of fluids, powders, and other agent materials are to be transported in and aerially dispersed by aircraft. Some aspects include positioning and securing of tanks aboard the aircraft to facilitate management and safety of the tanks and aircraft. Other aspects address coupling of the tanks and associated piping to lessen structural effects upon the aircraft. Further aspects deal with channeling, containing, and dumping stray agent materials that have escaped from the agent tanks on board the aircraft.

Abstract: The present invention is directed to an aerial delivery system that provides for the controlled delivery of items from an aircraft into a selected drop zone. In accordance with the present invention, the aerial delivery system includes a base and a sidewall arrangement adjacent the base. The sidewall arrangement generally acts as a sleeve defining an inner volume. Within the inner volume is a tray or cassette configured to be moveable within the inner volume. Adjacent the sidewall arrangement opposite the base is a top cover. The top cover is generally oversized relative to the shape defined by the sidewall arrangement. A plurality of straps connects the top cover, sidewall arrangement and, optionally, the material within the inner volume. The aerial delivery system is activated by an air stream that catches the oversized top cover, forcing the separation between the top cover and the other portions of the aerial delivery system.

Abstract: An enhanced aerial delivery system addresses issues raised when large quantities of fluids, powders, and other agent materials are to be transported in and aerially dispersed by aircraft. Some aspects include positioning and securing of tanks aboard the aircraft to facilitate management and safety of the tanks and aircraft. Other aspects address coupling of the tanks and associated piping to lessen structural effects upon the aircraft. Further aspects deal with channeling, containing, and dumping stray agent materials that have escaped from the agent tanks on board the aircraft.

Abstract: An enhanced aerial delivery system addresses issues raised when large quantities of fluids, powders, and other agent materials are to be transported in and aerially dispersed by aircraft. Some aspects include positioning and securing of tanks aboard the aircraft to facilitate management and safety of the tanks and aircraft. Other aspects address coupling of the tanks and associated piping to lessen structural effects upon the aircraft. Further aspects deal with channeling, containing, and dumping stray agent materials that have escaped from the agent tanks on board the aircraft.

Abstract: A deflector for an aircraft engine comprises a screen attached to a base, a connector connecting the base and the engine, a mechanism to limit the movement of the connector and base, a spring that has two ends, one end being attached to the base inside surface, the spring extending past the base, and the spring's other end is positioned proximate the screen; and a shock absorbing means attached to the base, and connects the base with the engine, whereby when a foreign object contacts the deflector with a force sufficient force to move the spring and the shock absorbing means, the screen, the spring and the shock absorbing means are urged towards the engine, the movement of the screen and the spring being controlled by the shock absorbing means and the limiting mechanism, preventing the foreign object, such as a bird, from entering the engine.

Abstract: Aerial dispersion systems that may be employed to allow rapid and temporary conversion of aircraft for aerial dispersion purposes, such as aerial fire-fighting. The aerial dispersion systems may be implemented using modular components that may be configured for compatibility with conventional cargo loading and unloading systems of modern aircraft, including side-loading cargo systems of wide body passenger and cargo aircraft having high lift capacities. The aerial dispersion systems may be rapidly installed in a large fleet of high capacity aircraft in response to a wildfire or other rapidly-developing emergency such as an oil spill, chemical or biological contamination incident, building or refinery fire, etc. After use, the aircraft of the fleet may be rapidly de-modified and returned to original condition.