will relieve oxygen pressure if the oxygen cylinder pressure reaches 2700 to 3000 psi. A green overboard indicator on the outside surface of the dorsal fin will be ruptured or missing to indicate that the rupture disc is not intact. Fire detection The engine fire system is of the continuous-element type and will provide a FIRE warning indication to the crew in the event that the rear nacelle area temperature exceeds 510 degrees Fahrenheit or if the forward nacelle area temperature exceeds 480 degrees Fahrenheit. Two spherical fire extinguisher containers can discharge their contents to either engine. A check valve prevents reverse flow between the containers. Monobromotrifluoromethane (CF3BR) is used as extinguishing agent. Two disc-type indicators are flush mounted under the left engine. If the yellow disc is ruptured, either or both containers have been discharged into the engine nacelle. If the red disc is ruptured, either or both the containers have been discharged overboard as a result of an overheat condition causing excessive pressure within the containers. Drag chute A drag chute is fitted as optional equipment on some Learjet 25 aircraft. The chute offers an addition safety margin, since it can significantly reduce the stopping distance. The drag chute is attached to the aircraft with a lanyard system that releases it from the aircraft should an inadvertent deployment be made while airborne. The lanyard is attached to the aircraft at the forward end of the tailcone access door opening. This point is near the aircraft centre of gravity and minimizes weathervaning when the chute is deployed under crosswind conditions. The drag chute has been deployed in a crosswind of up to 20 knots under actual test conditions. Flight characteristics Taxi operations are accomplished using the electronic nose wheel steering. The steering system on aircraft without variable authority nose wheel steering requires the pilot to select master or primary steering mode. In master mode, 10 degrees of steering is possible. This mode is suitable for straight taxi, takeoff and gentle turns. Primary steering mode allows up to 45 degrees angle of turn and is suitable for slow speed aggressive steering maneuvers. On aircraft equipped with variable authority steering, the steering authority varies with ground speed. The CJ610-6 engines fitted to the Learjet 25 have very low inertia and accelerate rapidly. The time required to accelerate from idle to 100% RPM is approximately four seconds. This excellent throttle response enables