Hydraulic systems are a vital component of modern aircraft, controlling critical functions such as: brakes, flaps, flight controls, and landing gear. Despite their pivotal role in ensuring flight operations’ safety, reliability, and efficiency, the basic design of these systems has remained largely unchanged since the 1960s. While the design of hydraulic systems has remained stagnant, most other aspects of aerospace engineering have advanced. With the push towards More Electric aircraft, we explore how hydraulic systems can also advance to keep pace with modern demands in terms of efficiency and sustainability.
Role of Hydraulics in Aircraft
Hydraulic systems in aircraft are essential for managing various critical functions that require precise control. These systems use hydraulic pumps and valves to transmit force to mechanical components throughout the aircraft. For example, the landing gear is operated via the hydraulics system, which allows it to deploy and retract reliably, accurately, and efficiently. Similarly, flight control surfaces such as ailerons, rudders, and elevators rely on hydraulics to ensure the pilot can manoeuvre the aircraft effectively.
The use of hydraulic systems offers a number of benefits to aircraft, the chief of which is reliability. Hydraulic systems have proven to be incredibly robust, even under the extreme conditions experienced during flight. They have a minimal risk of failure when maintained correctly, and have contributed greatly towards modern aviation safety. They are also extremely efficient, enabling quick and precise control over critical flight systems.
History of Hydraulic Systems in Aircraft
The widespread use of hydraulics in aircraft started during World War II when significant advances in aircraft hydraulic technology were made. By the 1960s, hydraulic systems had become standardised in commercial and military aircraft, providing reliable performance and safety. Aircraft like the Boeing 747, introduced in 1968, featured a centralised hydraulic system – a design that has remained fundamentally unchanged over the decades. The Boeing 787, introduced in 2011, features a centralised hydraulics system largely similar to that found in the 747, with a few minor optimisations. This is surprising when compared to other technologies on the same plane. From the communications interfaces and the materials used in the fuselage, all the way to air conditioning, aviation technology has progressed significantly, with the design of the hydraulics system stagnating.
These centralised systems consist of multiple hydraulic pumps that distribute hydraulic fluid through a network of pipes to various flight systems on the aircraft. Over the decades since its introduction, this system has proven its reliability, contributing to the safety record of modern aviation. However, this centralised design also has significant drawbacks that must be addressed.
Problem With Legacy Systems
One of the most significant drawbacks of traditional centralised hydraulic systems is their weight. They require an extensive network of pipes to distribute hydraulic pressure to flight systems, which adds considerable weight to an aircraft, often amounting to tonnes. This additional weight directly impacts fuel efficiency and range – critical concerns in the modern aerospace industry, which is increasingly focused on sustainability and reducing emissions.
The Future of Hydraulics in Aircraft
At Domin, we believe that the solution to addressing these drawbacks lies in the replacement of centralised hydraulic systems with decentralised hydraulics. This design involves using localised hydraulic subsystems instead of a single centralised system. These systems lead to significant weight reduction through smaller pumps, smaller piping, and a reduction in the amount of piping needed.
To realistically achieve this, Domin has developed micro-electrohydrostatic actuators (EHAs) by combining our high-speed, lightweight servo valves with our compact, power-dense radial piston pumps. These micro-EHAs are less than half the weight of equivalent electromechanical actuators while offering power, control, and reliability. By using our micro-EHAs and implementing these distributed hydraulics systems, we can achieve weight savings of up to 550 kg, depending on the aircraft.
While hydraulic systems have historically been reliable and integral to aircraft control and safety, their outdated design poses significant challenges to the modern aerospace industry. With our revolutionary servo valves and hydraulic pumps, we can rethink what hydraulics systems in aircraft can be, leading to more efficient aircraft, lower emissions, and a more sustainable aerospace industry.
