How Does the Boeing 777 Main Gear Oleo Strut Work and How Is EPR Calculated?

  • Context: Boeing 
  • Thread starter Thread starter stan19
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SUMMARY

The Boeing 777 main gear oleo strut operates by utilizing nitrogen gas for charging, which affects the oleo extension dimensions based on the aircraft's weight. The strut maintains a constant pressure that reflects the weight acting on it, while the damping action is provided by the oleo fluid and compressed gas within the strut. Additionally, the Engine Pressure Ratio (EPR) is calculated independently of the Engine Electronic Control (EEC) system, as evidenced by its display on the Engine Indication and Crew Alerting System (EICAS) during power-up events.

PREREQUISITES
  • Understanding of oleo strut mechanics and nitrogen charging
  • Familiarity with aircraft weight distribution and its impact on strut pressure
  • Knowledge of Engine Pressure Ratio (EPR) calculations
  • Basic comprehension of the Engine Indication and Crew Alerting System (EICAS)
NEXT STEPS
  • Research the construction and operation of Boeing 777 oleo struts
  • Learn about nitrogen charging techniques for aircraft struts
  • Study the principles of EPR calculation and its significance in aircraft performance
  • Examine the functionality of the EICAS in relation to engine management systems
USEFUL FOR

Aerospace engineers, aircraft maintenance technicians, and aviation students interested in the mechanics of landing gear systems and engine performance metrics.

stan19
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For main gear oleo strut servicing, when we charging it with nitrogen, The dimension of oleo extension would increase or decrease.As wat i understand, the pressure of strut may remain constant as it reflect the weight of aircraft acting on it.
Any idea about the construction and theory of b777 strut. the damping action is by its oleo fluid or compress gas in the strut?




Question 2:
How the aircraft calculate the EPR of the day(max epr) ; when aircraft is power up eventho engine EEC is not powered, the value is still showing on the EICAS. Does it mean it do nothing with the EEC?
 
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To respond to this thread, this image compares landing gear on the Boeing 777 to comparable transport air frames. From Wikipedia
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A Google search displays these pictures of 777 landing gear configurations. Notice the large size of the 777 relative to other dual jet engine transports.