getting to grips with aircraft performance 如何掌握飞机性能 1(47)

These specific rules, developed later, assume the simultaneous failure of two engines, which has to be considered for dispatch, as soon as one route sector is at more than 90 minutes’ flying time, with all engines, from a possible en route diversion airfield.
“JAR-OPS 1.505
(c) The two engines are assumed to fail at the most critical point of that portion of the route where the aeroplane is more than 90 minutes [flying time] away from [a possible diversion] aerodrome.” (Figure D10).

2.4.2. Obstacle Clearance – Two Engines Inoperative
2.4.2.1. Lateral Clearance
The regulations define the corridor width within which obstacles must be taken into account, as follows:

“JAR-OPS 1.505
(b) The two engines inoperative en-route net flight path data must permit the aeroplane to continue the flight, in the expected meteorological conditions, from the point where two engines are assumed to fail simultaneously, to an aerodrome at which it is possible to land, […] clearing all terrain and obstructions along the route within 9.3 km (5 nm)1 on either side of the intended track. […] If the navigational accuracy does not meet the 95% containment level, an operator must increase the width margin […] to 18.5 km (10 nm)2.”
1 FAA: 5 statute miles 2 JAA rule not valid for FAA

2.4.2.2. Vertical Clearance
Vertical clearance shall always be understood as a margin between the two engines’ inoperative net flight path and the obstructions. The two engines inoperative en route net flight path shall be determined from the Aircraft Flight Manual, and must take into account the meteorological conditions (wind and temperature) prevailing in the area of operations, as well as the use of ice protection systems, if required.

“JAR-OPS 1.505 The net flight path must clear vertically, by at least 2,000 ft all terrain and obstructions along the route within [the prescribed corridor].”

2.4.3. Diversion Airfield – Two Engines Inoperative

“JAR-OPS 1.505
(d) The net flight path must have a positive gradient at 1,500 ft above the aerodrome where the landing is assumed to be made after the failure of two engines.“ (Figure D12).
The route study must indicate the different possible en route diversion airfields, associated with the various diversion scenarios. The two-engine inoperative net flight path gradient should be positive at least at 1,500 feet above the airport where the landing is assumed to be made. For that purpose, fuel jettisoning can be considered, when the system is available.

3. IN-FLIGHT CABIN PRESSURIZATION FAILURE

3.1.1. Oxygen Systems
“JAR-OPS 1.770 (a)(1) An operator shall not operate a pressurized aeroplane at pressure altitudes above 10,000 ft unless supplemental oxygen equipment […] is provided.”
After a cabin pressurization failure, oxygen is automatically supplied to passengers through individual dispensing units, immediately available to each occupant. These units are automatically deployed in case of a cabin pressurization loss, but they only supply oxygen for a limited period of time.
　
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