Impact Of Increased Hydraulic Pressure In New Aircraft

In the ever-evolving world of aviation, technological advancements are constantly being made to improve the efficiency, safety, and performance of aircraft. One such advancement is the increase in hydraulic pressure in new aircraft from 3000 psi to 5000 psi. This seemingly small change has a significant impact on various aspects of aircraft design and operation.

Reduced Actuator Size

The increased hydraulic pressure leads to smaller actuators. In fact, new actuators are approx. only 60% of the volume of the old ones. This reduction in size leads to a decrease in weight, which is always a critical factor in aircraft design. For instance, in the photo below the release actuators of the Main Landing Gear (MLG) and MLG doors in the Boeing 787 show a noticeable difference in actuator volume.

Each image illustrates two actuators designed for the same function in the aircraft’s landing gear system: the Main Landing Gear Uplock Normal Release Actuator and the Main Landing Gear Uplock Alternate Release Actuator. Despite their shared purpose, there is a noticeable difference in size between the two, which is attributed to the different operating pressures. The actuator designed for the normal extension system, which operates at 5000 psi, is significantly smaller than the one for the alternate extension system, which operates at 3000 psi. This size difference exemplifies how higher-pressure systems allow for more compact component design, contributing to the overall reduction in aircraft weight and improvement in efficiency.

Lower Hydraulic Flow Rate

With smaller actuators, we need 40% less hydraulic flow rate to move the actuator the same stroke with the same speed. This results in smaller pipes, further reducing the weight. Additionally, the smaller pipes improve response time, enhancing the overall performance of the aircraft.

Smaller Hydraulic Reservoirs

All the above improvements also mean we need smaller hydraulic reservoirs. For example, the Boeing 737-800 need 66 liters in hydraulic systems A, B and the standby reservoirs combined. In contrast, the Boeing 787 need only 51 liters in the left, right, and center reservoirs combined. This reduction in reservoir size contributes to the overall weight reduction and costly hydraulic oil consumption.

Reduced Size of Other Components

The trend towards smaller components doesn’t stop at actuators and reservoirs. Pumps, filters, heat exchangers and valves also become smaller with the increased hydraulic pressure. This not only reduces weight but also makes these components easier to maintain and replace, reducing the time and cost of maintenance operations.

Significant Weight Reduction

The use of 5000 psi systems can lead to significant reductions in weight. For instance, it’s estimated that the Airbus A380’s move to 5000 psi may cut on-board mass by as much as a metric ton3. Similarly, other studies suggest that these high-pressure systems can reduce weight by up to 30% and volume by up to 40% over the used 3000 psi systems.

Cooling Capabilities

Hydraulic fluid in these high-pressure systems not only serves as a medium for power transmission but also plays a crucial role in cooling. It readily absorbs and releases heat, helping to maintain the optimal operating temperature of the aircraft’s hydraulic components. This dual function enhances the performance and longevity of these components, contributing to the overall efficiency and reliability of the aircraft.

Conclusion

In conclusion, the shift to 5000 psi hydraulic systems in modern aircraft like the Airbus A350, Boeing 787, and Airbus A380 represents a significant advancement in aviation technology. The benefits - from weight reduction and improved efficiency to enhanced safety and easier maintenance - underscore the immense potential of these systems. As we look to the future, it’s clear that high-pressure hydraulic systems will continue to play a pivotal role in shaping the next generation of aircraft.

Suggested reading point: The 2H/2E Design in Aircraft Hydraulic Systems

The 2H/2E design is a notable trend in modern aircraft hydraulic systems. This design features two hydraulic systems (referred to as “2H”) and two electric systems (referred to as “2E”)1. In this configuration, the hydraulic actuators are normally active, while the electrically powered actuators stand by and become operative in the event of a failure of the normal, hydraulically supplied, control lane

This design approach provides redundancy and ensures system reliability. It also allows for a more flexible and efficient use of power resources within the aircraft, contributing to overall performance and safety. Notably, this 2H/2E design has been incorporated into the hydraulic systems of advanced aircraft models such as the Airbus A380.

Remember, while this Article provides a broad overview, the specifics can vary based on the aircraft model and the particular hydraulic system used. Always consult with aircraft hydraulic system experts or technical manuals for the most accurate information.