Aircraft System Safety

Aircraft System Safety

1. The Assignment involves the analysis of the Hydraulic System shown in Figure 1. This diagram does not reflect all of the functions fulfilled by the hydraulic system, simply those that need to be considered in meeting the objectives of the assignment. Neither does it show detailed parts of the system such as Non-Return Valves, Accumulators, etc. The aircraft design is at the concept stage and the design team need to verify certain aspects of the hydraulic system architecture before proceeding to the detailed design stage. The aircraft has two wing mounted engines and has an average flight time of one hour.

BRIEF DESCRIPTION OF THE AIRCRAFT HYDRAULIC SYSTEM

The aircraft has 2 wing mounted engines, A and B. Each Engine drives an Engine Driven Pump (EDP) for both of the hydraulic sub-systems Green (G) and Yellow (H). Each sub-system has its own dedicated Hydraulic Reservoir (D & E) containing a Phosphate Ester hydraulic fluid. For the purposes of the analysis, carried out in the Assignment, complete loss of hydraulic fluid from any of the systems is represented by failure of the associated Hydraulic Reservoir.

The aircraft elevator is operated by two hydraulic actuators (P & V), powered by each of the hydraulic sub-systems, as shown in Figure 1. The elevator has manual reversion a purely mechanical system that enables continued pilot control of the elevator in the event that all hydraulic power is lost. The aircraft has two ailerons each powered by two hydraulic actuators (L &R), one from each of the hydraulic sub-systems. As with the elevator, the aileron has manual reversion such that, in the event of loss of all hydraulic power, pilot control, of the aileron, is maintained.

The rudder is operated by two actuators (M & S) each powered by one of the hydraulic sub-systems.

The Undercarriage Retraction Actuator is powered from the Green hydraulic

Subsystem. The Undercarriage may be extended by the Green hydraulic Subsystem or, in the event of loss of hydraulic power, manually by free-fall.

In the event of loss of power from engine A, the Green system continues to be pressurised by the Power Transfer Unit, J, (PTU), provided it has been selected on by the flight crew. The PTU is an hydraulic motor, powered by the Yellow hydraulic sub-system, which drives an hydraulic pump in the Green hydraulic sub-system. There is no fluid connection, within the PTU, between the hydraulic motor and the hydraulic pump.

The aircraft flap system is driven by two hydraulic motors powered by the Green and Yellow hydraulic sub-systems as shown in Figure 1. Although not addressed in this assignment, for reference, these sub-systems also power the flap asymmetry protection systems.

TASKS

For the Hydraulic System shown in Figure 1, derive the minimum cut set for loss of hydraulic power to the elevator. Assume that the Power Transfer Unit is NOT available throughout the flight.

How would this minimum cut set change if the Power Transfer Unit were selected on for the entire flight thus making it available to pressurise the Green hydraulic sub-system when the Yellow hydraulic sub-system is generating hydraulic power and there is hydraulic fluid in the Green hydraulic sub-system.

Based on the failure rates contained in Table 1 derive the failure probability per hour of loss of power to the elevator. Assume that the Power Transfer Unit operates throughout the flight.

Include diagrams or images as appropriate to support the discussion.

Avoid extensive introductions or descriptions. work should concentrate on critical evaluation.

Support your opinions / views with evidence. Sources of evidence could include, but should not be limited to, academic literature, accident reports, research and technical reports, etc.

Use a sans serif font such as Arial, Futura or Calibri.

Use a font size no lower than 11 pt and use 1.5 line-spacing for text.

Style APA 7