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FAA demands replacement of AOA sensors on Cirrus SF50 jets following incidents
22 April 2019

FAA demands replacement of AOA sensors on Cirrus SF50 jets following incidents

On April 18 the FAA published an emergency airworthiness directive (2019-08-51), requiring replacement of the angle of attack (AOA) sensor with an improved model.

This AD was prompted by Cirrus reporting three incidents of the stall warning and protection system (SWPS) or Electronic Stability & Protection (ESP) System engaging when not appropriate.
The SWPS and ESP may engage even when sufficient airspeed and proper angle of attack (AOA) exists for normal flight. SWPS includes the stall warning alarm, stick shaker and stick pusher. ESP includes under speed protection (USP). The SWPS and ESP engaging could potentially result in a STALL WARNING crew alert (CAS) message activation, accompanied by an audio alarm and stick shaker activation, followed possibly by either low speed ESP/USP engaging and/or the stick pusher engaging. The pilot will also observe the dynamic and color-coded (Red) airspeed awareness ranges displaying the stall band, regardless of actual indicated airspeed. These conditions, if not addressed, could result in the flight crew having difficulty controlling the airplane, lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.

Cirrus and Aerosonic (manufacturer of the technical standard order AOA sensor) have identified the probable root cause as an AOA sensor malfunction due to a quality escape in the assembly of the AOA sensor at Aerosonic. Two set screws that secure the potentiometer shaft to the AOA vane shaft may have improper torqueing and no application of thread locker (Loctite) to secure the two set screws.

Before further flight, AOA sensor must be replaced before further flight.  Operators may fly the airplane to a location where the modification/corrective action can be incorporated using a special flight permit.

FAA issues emergency AD regarding potential erroneous AOA input on Boeing 737 MAX

On November 7, the U.S. FAA issued an emergency Airworthiness Directive (AD 2018-23-51) regarding the potential for erroneous angle of attack input.

The AD, and an earlier Boeing FCOM Bulletin on the matter, was prompted by initial findings in the investigation into the cause of the crash of Lion Air flight JT610 on October 29, 2018. The Indonesian NTSC revealed that the aircraft experienced erroneous input from one of its AOA (Angle of Attack) sensors.

The FAA AD now requires “revising certificate limitations and operating procedures of the airplane flight manual (AFM) to provide the flight crew with runaway horizontal stabilizer trim procedures to follow under certain conditions.”

On November 6, 2018, Boeing issued an Operations Manual Bulletin (OMB) directing operators to existing flight crew procedures to address circumstances where there is erroneous input from an AOA sensor. (Boeing statement)


FAA issues AD for ultrasonic inspection for cracks in HPT stage 1 and stage 2 disks on CF6-80 engines

The U.S. Federal Aviation Administration (FAA) issued an Airworthiness Directive, requiring airlines to perform an ultrasonic inspection for cracks in High-Pressure Turbine (HPT) stage 1 and stage 2 disks on certain CF6-80 engines.

The AD, was published in the wake of the uncontained engine failure accident involving American Airlines flight 383 at Chicago-O’Hare International Airport on 28 October 2016. The aircraft, a Boeing 767-300ER suffered an experiencing an uncontained General Electric CF6-80C2 engine failure during takeoff. A fire erupted and consumed a large part of the wing. All 170 occupants survived.

Stage 2 high pressure turbine disk of AA383

FAA issues AD for certain Engine Alliance GP7000 engines after A380 uncontained engine failure

The U.S. Federal Aviation Administration (FAA) issued a new airworthiness directive (AD) for certain Engine Alliance  GP7270, GP7272, and GP7277 turbofan engines in the wake of the uncontained engine failure on an Air France Airbus A380.

This AD (2018-11-16) requires a one-time eddy current inspection (ECI) of the engine fan hub blade slot bottom and blade slot front edge for cracks, a visual inspection of the engine fan hub for damage, and removal of parts if damage or defects are found that are outside serviceable limits.

This AD was prompted by the uncontained failure of the engine fan hub on an Air France A380 on September 30, 2017.

The required actions must be accomplished within 120 days after the effective date of the AD, which is July 2, 2018.



FAA issues new airworthiness directive for all CFM56-7B engines in wake of Southwest 1380 accident

The U.S. FAA issued a new airworthiness directive (AD) for all CFM International S.A. (CFM) Model CFM56-7B engines in the wake of the April 17 uncontained engine failure accident involving a Southwest Airlines Boeing 737-700.

The AD 2018-09-10 requires initial and repetitive inspections of the concave and convex sides of the fan blade dovetail to detect cracking and replacement of any blades found cracked.

The AD is effective May 14, 2018.

In response to the Southwest Airlines accident, the FAA issued Emergency AD 2018-09-51, to address certain high-time CFM56-7B engines, specifically including those with 30,000 or more total accumulated flight cycles since new. AD 2018-09-51 requires a one-time ultrasonic inspection (USI) of the concave and convex sides of the fan blade dovetail.
Since the issuance of that AD, the FAA states it has been working with CFM to develop an additional compliance plan to address the risk of fan blade failure for the entire CFM56-7B fleet. This AD addresses the unsafe condition affecting CFM56-7B engines by requiring initial and repetitive inspections of fan blades based on accumulated fan blade cycles.

FAA and EASA issue Emergency Airworthiness Directive for CFM56-7B engine inspections

The U.S. Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA) issued Emergency Airworthiness Directives, requiring inspection of CFM56-7B engines, in the wake of the accident involving Southwest flight 1380.

On April 17, a Boeing 737-700 of Southwest Airlines, powered by CFM56-7B model engines, experienced an engine failure due to a fractured fan blade, resulting in the engine inlet cowl disintegrating. Debris penetrated the fuselage causing a loss of pressurization and prompting an emergency descent. Although the airplane landed safely, there was one passenger fatality.

The FAA AD (2018-09-51) details specific series of CFM56-7B model engines with 30,000 or more total accumulated flight cycles since new. The FAA requires that airlines within 20 days after receipt of this AD, perform a one-time ultrasonic inspection (USI) of all 24 fan blade dovetail concave and convex sides of these engines to detect cracking.

On the same day, EASA issued Emergency AD 2018-0093. This AD describes similar required actions for engines with 30,000 or more engine cycles. However, EASA also requires an inspection on engines with less than 30,000 engine cycles. These need to be checked before exceeding 20.000 fan blade cycles, or within 133 days after the effective date of this AD, whichever occurs later.
Also, the EASA AD requires inspections to be repeated at intervals not exceeding 3,000 engine cycles.

The EASA AD supersedes a previous AD (2018-0071), dated March 26, 2018. This AD was issued following a previous engine failure event and required inspections within 9 months.

CFM56-7B engines are known to be installed on, but not limited to, Boeing 737-600, 737-700, 737-800 and 737-900 aircraft.


FAA to publish AD to require CFM56-7B engine inspections after uncontained failure on Southwest 1380

The FAA issued a statement, saying it is planning an AD to be published in the wake of the Southwest Boeing 737 uncontained engine failure accident on April 17.

The Boeing 737-700, powered by CFM56-7B engines, diverted to Philadelphia when the no.1 engine suffered an uncontained failure while climbing through FL325. One passenger sustained fatal injuries after debris broke a window.

The NTSB stated that fan blade no.13 was missing and that it had separated at the hub. Preliminary investigation results show there was evidence of metal fatigue in the area where the blade broke.

This prompted the FAA to issue the following statement:

“The FAA will issue an Airworthiness Directive (AD) within the next two weeks that will require inspections of certain CFM56-7B engines. The directive will require an ultrasonic inspection of fan blades when they reach a certain number of takeoffs and landings. Any blades that fail the inspection will have to be replaced.”


EASA issues emergency AD on certain PW1000G powered Airbus A320neo and A321 neo aircraft

The European Aviation Safety Agency (EASA)  issued an Emergency Airworthiness Directive with an operational limitation on certain Airbus A320neo and A321 neo aircraft fitted with PW1000G engines.

EASA states that several occurrences of engine in-flight shut-down (IFSD) and Rejected Take-Off (RTO) have been reported on certain Airbus A320neo family aeroplanes. While investigation is ongoing to determine the root cause, preliminary findings indicate that the affected engines, which have high pressure compressor aft hub modification embodied from ESN P770450, are more susceptible to IFSD.

In line with an Airbus alert to operators, AD 2018-0041-E requires the following operational restrictions:

  1. Within 3 flight cycles (FC) from the effective date of this AD, do not operate an aeroplane having two affected engines installed.
  2. Within 1 FC from the effective date of this AD, for an aeroplane having at least one affected engine(s) installed, ETOPS operations are not allowed.
  3. Inserting a copy of this AD in the ETOPS Configuration, Maintenance and Procedures (CMP) of concerned aeroplane models and, thereafter, operating that aeroplane on ETOPS accordingly, is acceptable to comply with paragraph (2) of this AD.

The AD is considered to be an interim action and further AD action may follow.


EASA issues Emergency Airworthiness Directive for Trent 1000 engines

The European Aviation Safety Agency (EASA) issued an emergency AD for specific Rolls-Royce Trent 1000 engines, as a result of an incident in November 2016.

A Scoot Boeing 787-9 Dreamliner returned to land at Singapore Airport after the crew performed an engine in-flight shut-down (IFSD) following N2 vibration and multiple messages.
The post-flight borescope inspection of the engine revealed an intermediate pressure turbine blade (IPTB) missing at the shank. Analysis shows that this kind of failure was due to sulphidation corrosion cracking.
Initial actions included and AD (2017-0056) that required removal from service of certain engines. Since that AD was issued, prompted by further occurrences and analyses, it has been decided that, to reduce the risk of dual IFSD, a new cyclic life limit must be applied to certain engines, which determines when an engine can no longer be installed on an aeroplane in combination with certain other engines.
For this reason, the EAD requires de-pairing of the affected engines. This AD is considered an interim action and further AD action may follow.

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Propeller control system malfunction eyed in fatal Let L-410 accident in Russia

The Let L-410 impacted terrain (photo: MAK)

A propeller control system malfunction is focus of the investigation into the cause of a fatal Let L-410 accident in Russia in November 2017.

The Let L-410 aircraft operated by Khabarovsk Avia impacted a forest with little or no forward speed, 1200 m short of runway 04 at Nelkan Airport, Russia. Two crew members and four passengers suffered fatal injuries. A young girl was the only survivor.

On 15 December 2017 EASA issued a Safety Information Bulletin, stating that preliminary investigation identified an un-commanded activation of the beta mode signalization of a propeller during the final approach. As a preliminary preventive measure, Let issued Revision 1 of Service Bulleting L410UVP-E/492b, providing instructions to check the components of engine and propeller control system, including the beta switch.

More information: