InFO directs attention to Angle-of-attack sensor
Boeing 737 Max, Cirrus SF-50 Vision, A320 and A321 aircraft
Leonard M. Greene ,inventor of AOA, Founder of Safe Flight Instrument and co-founder of Corporate Angel Network
By Sean Broderick | Aug 20, 2019
The FAA, citing non-specific “continued airworthiness activity,” reminded operators that angle-of-attack (AOA) sensors can be easily damaged during “normal operations” and must be carefully maintained to ensure safe flight operations.
‘Based on continued airworthiness activity on multiple foreign and domestic products, including large transport aircraft and small general aviation aircraft, FAA has determined it is necessary to advise operators of the importance of performing proper operations and maintenance on AOA sensors,’ the agency said in an ‘information for operators’ bulletin (InFO).
The U.S. agency cautioned that the sensors are exposed to many conditions that could result in damage.
‘It is imperative that all operators are aware of the criticality of AOA sensors and the potential for damage during normal operations, maintenance procedures, servicing procedures, and any other procedures around an aircraft where damage to an AOA sensor could occur,’ the FAA said. It urged operators to remind everyone ‘involved with the operation and maintenance of aircraft, such as aircraft operators, certificate holders, maintenance providers, ramp service providers and miscellaneous service providers,’ to follow AOA airworthiness requirements diligently.
FAA’s advisory messages are often triggered by specific incidents or collections of similar reports. If they are linked to ongoing accident investigations, however, international protocol limits what the agency can reveal.
AOA sensor failures are at the center of two ongoing probes into Boeing 737 MAX accidents that have the worldwide fleet grounded. But the agency said the message is not indicative of any new findings coming from those investigations.
‘The [alert] was sent out as a reminder and was not indicative of any specific findings related to the ongoing investigations,’ an FAA spokesman said.”
In addition to the Boeing 737 Max mentioned by Mr. Broderick, the AOA sensor has had problems with the Cirrus SF-50 Vision, A320 and A321[i] aircraft; so, there is more validity to the not-just-the-Max comment.
Here is the interesting origins of the AOA:
Such a simple, yet critical instrument, one might presume, has long been part of the aviation safety inventory. Not so, Leonard M. Greene invented the AOA and his patent was granted on August 8, 1995.
SUMMARY OF THE INVENTION
In essence, an angle of attack sensor in accordance with the present invention includes a rotatable vane which is positioned in response to a fluid stream
or airstream across the vane and means for generating a signals which indicates the position of the vane with respect to the fuselage horizontal reference plane.
The AOA was not the only innovation of this American inventor and aerodynamics engineer who held more than 200 patents, many of which are aviation-related. To build the device, Greene established the Mr. Greene founded Safe Flight Instrument Corporation in 1946 to manufacture his aviation instruments.
Mr. Greene co-founded the Corporate Angel Network, a philanthropic organization that matches patients with business aircraft for free travel to treatment. This service not only improves the patients’ chances of survival but at the same time, it reduces their emotional stress, physical discomfort and financial burden. CAN is one of NBAA’s Charities and the association’s BACE raises significant funds for the charities operations.
Greene died on November 30, 2006 at the age of 88 in Mamaroneck, New York.
[i] In 2014, Lufthansa flight 1829 took off from Bilbao, Spain, and was ascending normally when the plane’s nose unexpectedly dropped. The plane — an Airbus A321 with 109 passengers on board — began to fall. The co-pilot tried to raise the nose with his controls. The plane pointed down even further. He tried again. Nothing, according to a report by German investigators.
As the Lufthansa plane fell from 31,000 feet, the captain pulled back on his stick as hard as he could. The nose finally responded. But he struggled to hold the plane level.
A call to a ground crew determined that the plane’s angle-of-attack sensors — which detect whether the wings have enough lift to keep flying — must have been malfunctioning, causing the Airbus’s anti-stall software to force the plane’s nose down
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