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FAA issues Boeing 737 MAX proposed Airworthiness Directive
4 August 2020

FAA issues Boeing 737 MAX proposed Airworthiness Directive

The FAA has issued a notice of proposed rulemaking (NPRM) for a Boeing 737 MAX airworthiness directive (AD) (PDF) as another step to clear the grounded Boeing 737 MAX jets for flight again.

The NPRM proposes mandating a number of design changes. The NPRM is open for public comments with 45 days of publication. To assist with the review of the proposed AD, the FAA also published their Preliminary Summary of the FAA’s Review of the Boeing 737 MAX (PDF).

In short, the NPRM proposes the following steps to be taken before any 737 MAX will be allowed to operate revenue flights:

  • Installation/Verification of Flight Control Computer (FCC) Operational Program Software (OPS)
    Note: Boeing updated the FCC software to eliminate MCAS reliance on a single AOA sensor signal by using both AOA sensor inputs and changing flight control laws to safeguard against MCAS activation due to a failed or erroneous AOA sensor.
  • Airplane Flight Manual (AFM) Revisions
  • Minimum Equipment List (MEL) Provisions for Inoperative Flight Control System Functions
  • Installation/Verification of MAX Display System (MDS) Software
    Note: Boeing has revised the AOA DISAGREE alert message implementation to achieve the original design intent to be standard on all 737 MAX aircraft.
  • Horizontal Stabilizer Trim Wire Bundle Routing Change
  • AOA Sensor System Test
  • Operational Readiness Flight

FAA requires additional post-storage B737 engine inspections after several in-flight shutdown incidents

The U.S. FAA is requiring operators of Boeing 737 aircraft to inspect engine bleed air valves of aircraft that have been stored after several incidents of in-flight engine shutdowns.

Many airlines are restarting flights following groundings related to the COVID-19 pandemic. The FAA received four recent reports of single-engine shutdowns due to engine bleed air 5th stage check valves being stuck open. Corrosion of the engine bleed air 5th stage check valve internal parts during airplane storage may cause the valve to stick in the open position. If this valve opens normally at takeoff power, it may become stuck in the open position during flight and fail to close when power is reduced at top of descent, resulting in an unrecoverable compressor stall and the inability to restart the engine. Corrosion of these valves on both engines could result in a dual-engine power loss without the ability to restart.

This led the FAA to issue an Emergency Airworthiness Directive AD 2020-51, requiring inspections of the engine bleed air 5th stage check valve on each engine and replacement of the engine bleed air 5th stage check valve if any inspection is not passed. The EAD applies to all Boeing 737-300, -400, -500, -600, -700, -700C, -800, and -900 models in storage on or after the date of receipt of this AD, and any airplane that, as of the date of receipt of the AD, has been operated for 10 or fewer flight cycles since returning to service from the most recent period of storage.

 

FAA issues emergency AD following Vietnam Airlines A321 uncontained IAE V2533 engine failure

The U.S. FAA issued an emergency airworthiness directive following an uncontained engine failure of an IAE V2533-A5 engine of an Airbus A321.

On March 18, Vietnam Airlines flight VN920, an Airbus A321-231, powered by IAE V2533-A5 model turbofan engines, experienced an uncontained high-pressure turbine (HPT) 1st-stage disk failure on takeoff from Ho Chi Minh City-Tan Son Nhat Airport in Vietnam. The flight crew aborted the takeoff.

As a result of this occurrence, the FAA issued an emergency AD on March 21, 2020, requiring removal from service of affected HPT 1st-stage disks with specific part numbers, installed on IAE V2500 engine models. The FAA considers this an interim action as the root cause of this incident is still under investigation.

 

FAA issues emergency AD after ground fire accident involving Cirrus SF50 Vision Jet

The FAA issued an emergency airworthiness directive (AD) to remove headset amplifier and microphone interface circuit card assemblies from the Cirrus SF50 Vision Jet after a fire accident in December.

On December 27, 2019, a Cirrus SF50 Vision Jet caught fire prior to departure from Santa Monica Municipal Airport, California, USA. The private pilot was not injured, and the airplane sustained substantial damage.
Upon arrival at the airplane, the pilot began to perform preflight checks and completed a walkaround. After boarding and closing the cabin door, he continued with the checks and observed haze in the cabin accompanied by a faint smell of smoke. He continued to follow the checklists and after starting the engine, the smoke smell became stronger, and he decided to terminate flight preparations, and have a mechanic examine the airplane.
After completing the engine shutdown, he opened the main cabin door, and began to see smoke issue from the armrest area of the number 5 (right center) passenger seat. A mechanic arrived at the airplane with a fire extinguisher within a few minutes, however the smoke had become dense, and was now streaming out of the cabin door. A few minutes later, flames began to emerge from the cabin, and by 11:55 the cabin was completely engulfed. The fire department arrived at 12:02, and the fire was extinguished.
The airplane sustained extensive thermal damage, with fire consuming the cabin roof and destroying the cabin contents from the aft wall of the parachute (CAPs) enclosure through to the engine inlet nacelle, with fire damage more extensive on the right side of the airframe. Fire had consumed the lower right walls of the cabin down to the wing root, with only composite cloth remaining. The right wing was intact, but sustained thermal damage to the upper skin from the root outboard about 4 ft short of the tip. The left wing, and lower left exterior skins of the cabin were largely free of fire damage.

An investigation determined the probable root cause was a malfunction of the headset amplifier and the microphone interface circuit card assemblies for the 3.5 millimeter audio and microphone jacks. This malfunction likely resulted in an electrical short and subsequent uncontained cabin fire without activating circuit protection.
On February 14, 2020, the FAA issued an emergency AD to disconnect and remove the headset amplifier and microphone interface circuit card assemblies for the 3.5 mm audio and microphone jacks on all Cirrus SF50’s.

FAA issues Emergency AD on GE90 engines after Boeing 777-300ER uncontained engine failure

The U.S. FAA issued an Emergency Airworthiness Directive (AD)  in the wake of a Boeing 777-300ER uncontained engine failure occurrence on October 20, 2019.

A Thai Airways Boeing 777-300ER airplane powered by GE GE90-115B model turbofan engines experienced an uncontained high-pressure turbine (HPT) failure that resulted in an aborted takeoff at Bangkok-Suvarnabhumi International Airport. Debris impacted the aircraft fuselage and the other engine.

To prevent a recurrence, the FAA requires the removal from service of the GE GE90-110B1 or GE90-115B model turbofan engine interstage seal, part number 2505M72P01 or 2448M33P01, from the affected engines.

The AD lists 16 engine serial numbers that are affected.

More information:

Canada issues Emergency AD to limit Airbus A220 engine power settings after recent incidents

Regulator Transport Canada issued an Emergency Airworthiness Directive (AD) to limit certain engine power settings on Airbus A220 aircraft following three recent failures.

Three inflight shutdowns occurred within three months time: July 25, 2019, September 16, 2019, and October 15, 2019. In all cases, the aircraft involved was a Swiss International Air Lines Airbus A220-300 (formerly named Bombardier CSeries 300) with Pratt & Whitney PW1524G-3 engines. These inflight shutdowns were due to failure of the low-pressure compressor (LPC) stage 1 rotor, which resulted in the rotor disk releasing from the LPC case and damaging the engine.

Investigations are ongoing to determine the root cause., but preliminary investigation results indicate high altitude climbs at higher thrust settings for engines with certain thrust ratings may be a contributor. This condition, if not corrected, could lead to an uncontained failure of the engine and damage to the aeroplane.
Transport Canada issued the AD on October 26, introducing a new Aircraft Flight Manual (AFM) limitation and normal procedure to limit the engine N1 setting to 94% while above 29000 feet. This AD is considered an interim action and further AD action may follow.

 

FAA issues emergency AD on GE90-115B turbofan engines following uncontained failure incident

The FAA issued an emergency Airworthiness Directive (AD), ordering the removal of a seal from certain General Electric GE90-115B turbofan engines.

The emergency AD was prompted by an incident that occurred on October 20, 2019, in which a Thai Airways Boeing 777-300ER airplane powered by GE GE90-115B turbofan engines experienced an uncontained high-pressure turbine (HPT) failure that resulted in an aborted takeoff. Debris impacted the aircraft fuselage and the other engine.

The AD calls for the removal from service of the Interstage Seal of certain GE GE90-115B turbofan engines, within 25 flight cycles.

 

Airbus A220 PW1500G engine failures prompt inspection AD

The FAA issued an airworthiness directive (AD), requiring initial and repetitive inspections on certain Pratt & Whitney geared turbofan engines following two recent incidents.

The first inflight shutdown occurred on July 25, 2019 and the second occurred on September 16, 2019. In both cases, the aircraft involved was a Swiss International Air Lines Airbus A220-300 with Pratt & Whitney PW1524G-3 engines.
These inflight shutdowns were due to failure of the low-pressure compressor (LPC) stage 1 rotor, which resulted in the rotor disk releasing from the LPC case and damaging the engine.

To prevent recurrences, the FAA requires initial and repetitive borescope inspections of the LPC inlet guide vane (IGV) and the LPC stage 1 rotor and, depending on the results of the inspections, replacement of the LPC.

Although these incidents occurred on PW1524G-3 model turbofan engines, the FAA is including PW1900 engines because similarities in type design make these engines susceptible to the same unsafe condition. The required inspections have to be performed within 50 flight cycles from September 26, and thereafter at intervals not to exceed 50 flight cycles until the engine accumulates 300 flight cycles.

The investigation into both incidents has been delegated to the NTSB.

Parts from the low-pressure compressor stage 1 rotor in the July 25 incident

CASA Australia and EASA lift grounding of GA-8 Airvan

Australian and European regulators decided to lift the grounding of the GA8 Airvan.

The grounding came into effect on July 20, following a fatal accident on 14 July 2019, when a GA8 Airvan skydiving plane crashed in Sweden. At 4000 meters altitude, the aircraft suffered a separation of a wing.

Since the emergency AD was issued, CASA Australia informed EASA that the results of the physical inspection of the accident aircraft indicate that it appears to have been exposed to aerodynamic loads beyond those for which the type design is certificated.

No evidence was found to indicate that an unsafe condition exists or could develop that would warrant further grounding.

CASA Australia and EASA ground GA-8 Airvan following a recent accident in Sweden

Australian and European regulators decided to ground the GA8 Airvan following a recent accident.

On 14 July 2019, a fatal accident occurred with a GA8 Airvan skydiving plane in Sweden. Indications are that the aircraft, at 4000 meters altitude, suffered structural failure. Early reports are that a wing may have detached prior to the accident, but, at this time, the root cause of the accident cannot be confirmed.
CASA Australia, the authority of the State of Design of the affected type design, has informed EASA that a Direction will be issued, which provides for the temporary prohibition of operations of the GA8 Airvan in Australia. The Direction will take effect on 20 July 2019 and will be valid for 15 days. Based on all available information, and taking into account the Australian Direction, EASA has
decided to ground the affected aeroplanes registered in EASA Member States, until further notice.
The emergency AD 2019-0177-E is considered an interim action and further AD action may follow.

File photo of a GA8 Airvan (c) H. Ranter