The
propellers used to power numerous aircraft require regular inspections to ensure their integrity. The interval for such inspections is typically specified by the propeller's manufacturer. Similarly, the fan blades of
jet engines are susceptible to cracking and thus require routine inspections to be conducted by operators. Such inspections are typically performed during maintenance intervals, typically using a combination of visual and
ultrasound scans performed upon each fan blade by technicians to detect any cracks. During October 2018, both the
Federal Aviation Administration (FAA) and the
European Aviation Safety Agency (EASA) issued updated
airworthiness directives that specified more frequent inspections of the blades of the
CFM International CFM56-7B turbofan powerplant used on many
airliners. The in-flight failure of a rotorcraft's main
rotor blade would likely lead to a serious life-jeopardising accident. Thus, manufacturers have developed detection techniques that guard against blade failure caused by fatigue cracking. A common method involves the
pressurisation of the interior cavity of the rotor blade spar with
nitrogen gas. Upon the formation of a crack, pressure is lost and a sensor built into the root of the rotor blade would detect this pressure change. Readouts from this sensor would be displayed via a cockpit display to the pilot. This system is intended to alert operators to cracking rotor blades in advance of a catastrophic failure, allowing for replacement blades to be installed in advance of such an outcome. American helicopter specialist
Sikorsky has incorporated this technology onto several of its rotorcraft, including the
S-61 series, ==Electricity generation==