The Pressure Measuring Instruments and Sensing Mechanisms of Aircraft

During flight, pilots need to be aware of many system characteristics and conditions in order to safely and efficiently operate the aircraft. Across the various flight conditions that are tracked during a typical flight, pressure is an important characteristic that can have major effects on many systems. Ranging from hydraulic fluid pressure that ensures force for actuation to oil pressure that is paramount for proper engine lubrication and cooling, the pressure of various systems can have a great effect on the performance of the aircraft during flight.

In order to track the pressure of various aircraft systems, pilots rely on a number of pressure sensing instruments that are located within the flight deck. Pressure sensing instruments may be able to carry out measurements directly or remotely depending upon the system that they are monitoring as well as the sensing mechanisms that such instruments employ. For the safety of flight, it is crucial that pressure sensing instruments are always accurate in their readings. Depending upon the system that the instrument is monitoring and its design, pressure measuring may be conducted mechanically or electronically. Across all pressure measuring instruments, however, the most common mechanisms used are the bourdon tube, diaphragm or bellow, and solid-state sensing devices.

The bourdon tube is a tube-shaped component that is coiled, and the open end is fixed to a surface while the sealed end is free to move. In order to measure pressure, the bourdon tube allows for fluids to enter the open end, and this causes the sealed, free end to begin straightening out. The higher the pressure of the fluid, the more the tube will be straightened out. As such, a pointer is provided at the end of the tube and will move across a dial as pressure increases with the help of small shafts and gears. The bourdon tube is common to many pressure gauges, regularly serving engine oil pressure gauges, hydraulic pressure gauges, oxygen tank pressure gauges, and deice boot pressure gauges. 

Diaphragms and bellows are also basic sensing mechanisms for instruments, and the two components have similar functionalities and designs. The diaphragm is a metal disk that has thin walls and may be corrugated, and its construction allows for expansion when pressure enters one side of the disk. With the attachment of a linkage and pointer, the expanding and contracting movements of the diaphragm may be tracked and displayed on a dial for the pilot. Bellows are components consisting of multiple diaphragm chambers, and they can measure differential pressure with ease. Diaphragms and bellows are common to a number of instruments such as the altimeter, vertical speed indicator, manifold pressure gauge, and cabin differential pressure gauge.

Solid-state sensing devices are becoming a staple of modern aircraft, allowing for critical pressures to be determined for flight safety. They can also work with electronic flight instrument computers, utilizing microelectric signals that are converted into a digital format for the use of computers. In order to determine pressure changes, solid-state sensors take advantage of electrical output or resistance changes that are tied to adjustments in pressure. For many sensors, wires are embedded into a crystal or pressure-sensitive semiconductor chip. As pressure is induced to the crystals, a small amount of electricity is generated or the resistance will change, both of which can be detected by the sensor for a pressure reading. Solid-state pressure sensor components can be used for almost all systems where pressure is monitored, though they are most common for remote sensing applications.

With the various pressure sensing mechanisms and the instruments that they support, pilots can oversee the operational characteristics of various systems to ensure safety throughout a flight. At RFQ experts, we operate as an online distributor of aircraft parts, and we are your sourcing solutions for top quality aircraft instruments, pressure sensors, pressure gauges, and much more. If you find items from our website that you wish to procure, we invite you to request a quote today through the submission of an Instant RFQ form. With the information that you provide us, our team of industry experts can tailor a personalized solution for your particular needs and requirements. Begin the purchasing process today and see how RFQ Experts can serve as your strategic sourcing partner.


July 21, 2020

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