Aircraft Mechanical Movement Indication Instruments

Aircraft instruments are devices that provide a great amount of flight pertinent information for the pilot to safely fly. While many instruments may convey information such as spent fuel and current altitude, there are also many instruments that are used for measuring and indicating the mechanical movement of components, instruments, or the aircraft as a whole. These instruments may vary in what components that they measure, and this information can be very useful for a pilot during flight operations. In this blog, we will discuss some of the main aircraft mechanical movement indication instruments, such as tachometers, the synchroscope, accelerometers, and stall warning and angle of attack (AOA) indicators.


Tachometers are an instrument that is used to measure the speed of the reciprocating engine’s crankshaft or a gas turbine engine’s compressor. In regards to reciprocating engines, tachometers allow the pilot to be aware of engine power and operational limits. Typically, tachometers are either mechanical or electric. The choice between mechanical and electric depends on the distance between the engine and instrument panels, as well as the size of the aircraft. Smaller aircraft with small distances between the engine and instrument panel will most often use a mechanical tachometer, featuring an indicator attached to the engine via a flexible drive shaft. The drive shaft rotates in unison with the engine, causing a pointer to move and indicate the rotations per minute (RPM). When the engine is not located in the fuselage or near the instrument panel, electric tachometers are used. Electric tachometers can feature increased accuracy, and their functionality may be provided by a generator that turns with the engine, providing a frequency output that may be measured to indicate the speed of the engine.


The synchroscope of an aircraft can be used to check if two or more rotating components are in sync with each other by using the measurements made by the tachometer to compare the RPM of components. Synchroscopes operate with the use of a motor and gear wheel that receives electric current from the components that they are comparing. If one current overpowers the other due to a higher RPM, the gear wheel will rotate in a direction to indicate such discrepancy. If both components are in sync, the synchroscope will not turn the gear. With these measurements, the pilot may adjust systems and operations as needed.


Accelerometers are an instrument that is used to measure the acceleration of the measured system or component. Within the realm of aviation, accelerometers may measure forces that are exerted upon the airframe. Aircraft accelerometers measure the G forces enacted upon the aircraft, which are typically greater when an aircraft makes rapid climbs, descents, or is travelling at great speeds. Within the accelerometer, a weight remains in place as the instrument shifts around due to acceleration forces. As the position changes, the acceleration can be measured to indicate such information for the pilot. Accelerometers are typically mechanical, but they may also be electric or digital, measuring acceleration through resistance, current flow, or capacitance.

Stall Warning and Angle of Attack Indicators

Aircraft instruments such as stall warning and angle of attack (AOA) indicators are also critical for maintaining safety, allowing the pilot to avoid stalls caused by a loss of lift on wing surfaces. There are various types of stall warning indicators, such as those that implement a reed that makes an audible noise in the cockpit when air is sucked into a passage containing the reed at certain angles of attack. Electric switches may also provide a similar effect, making audible sounds at stalling angles of attack.

When it comes time to begin sourcing the tachometers, accelerometers, and synchroscope components that you need for your next operation or project, look no further than Cogent Sourcing. Cogent Sourcing is owned and operated by ASAP Semiconductor, and we can help you find the aircraft instruments and other aerospace components that you need, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we're always available and ready to help you find all the parts and equipment you need, 24/7x365. ASAP Semiconductor is an FAA AC 00-56B accredited and ISO 9001:2015 certified enterprise. For a quick and competitive quote, email us at or call us at +1-714-705-4780.


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