NTSB Issues Inspection Recommendations for GEnx-1B and -2B engines
Posted: 2012-9-17
The National Transportation Safety Board today issued two urgent safety
recommendation to the FAA regarding two recent occurrences in which the fan
midshaft on General Electric GEnx-1B engines fractured or exhibited crack
indications; and a GEnx -2B incident that appears similar in nature. The
recommendations include: (1) Issue an airworthiness directive to require, before
further flight, the immediate ultrasonic inspection of the fan midshaft in all
GEnx-1B and -2B engines that have not undergone inspection, and (2) Require
repetitive inspections of the fan mid-shaft at a sufficiently short interval that
would permit multiple inspections and the detection of a crack before it could
reach critical length and the fan mid-shaft fractures.
On July 28, 2012, the NTSB initiated an investigation of an engine failure that
occurred on a Boeing 787 during a pre-delivery taxi test in Charleston, South
Carolina. This investigation is ongoing.
"The parties to our investigation -- the FAA, GE and Boeing -- have taken many
important steps and additional efforts are in progress to ensure that the fleet is
inspected properly," said NTSB Chairman Deborah A.P. Hersman. "We are
issuing this recommendation today because of the potential for multiple engine
failures on a single aircraft and the urgent need for the FAA to act immediately."
In addition, on August 31, 2012, a GEnx-1B engine installed on a Boeing 787
that had not yet flown was found to have an indication of a similar crack on the
fan midshaft. The fan midshaft was removed from the engine for further
inspection and examination. As a result of the investigative work to date, the
NTSB has determined that the fan midshafts on the GEnx engines fractured or
cracked at the forward end of the shaft where the retaining nut is installed.
GE developed a field ultrasonic inspection method to inspect the fan midshaft in
the area where the fracture and crack occurred that can be accomplished with
the engine still installed on the airplane. To date, all in-service and spare GEnx-
1B engines have been inspected. In addition, all GEnx-2B engines on passenger
airplanes have been inspected. However, the NTSB is aware of approximately 43
GEnx-2B engines on 747-8F cargo airplanes that have not yet been inspected
and is concerned that they are potentially susceptible to a fan midshaft failure.
More recently, a Boeing 747-8F cargo flight, operated by Air Bridge Cargo,
equipped with General Electric GEnx-2B turbofan engines, experienced a loss of
power in one of the engines during the takeoff roll in Shanghai, China. The
airplane had accelerated through 50 knots when the engine's low pressure rotor
speed dropped. The pilot rejected the takeoff and returned to the ramp.
Photographs of the low pressure turbine show damage similar to the GEnx-1B
engine from the Charleston incident. The NTSB will continue to coordinate with
our investigative counterparts in China.
To view NTSB's urgent recommendation letter, visit:
www.ntsb.gov/doclib/recletters/2012/A-12-052-053.pdf
recommendation to the FAA regarding two recent occurrences in which the fan
midshaft on General Electric GEnx-1B engines fractured or exhibited crack
indications; and a GEnx -2B incident that appears similar in nature. The
recommendations include: (1) Issue an airworthiness directive to require, before
further flight, the immediate ultrasonic inspection of the fan midshaft in all
GEnx-1B and -2B engines that have not undergone inspection, and (2) Require
repetitive inspections of the fan mid-shaft at a sufficiently short interval that
would permit multiple inspections and the detection of a crack before it could
reach critical length and the fan mid-shaft fractures.
On July 28, 2012, the NTSB initiated an investigation of an engine failure that
occurred on a Boeing 787 during a pre-delivery taxi test in Charleston, South
Carolina. This investigation is ongoing.
"The parties to our investigation -- the FAA, GE and Boeing -- have taken many
important steps and additional efforts are in progress to ensure that the fleet is
inspected properly," said NTSB Chairman Deborah A.P. Hersman. "We are
issuing this recommendation today because of the potential for multiple engine
failures on a single aircraft and the urgent need for the FAA to act immediately."
In addition, on August 31, 2012, a GEnx-1B engine installed on a Boeing 787
that had not yet flown was found to have an indication of a similar crack on the
fan midshaft. The fan midshaft was removed from the engine for further
inspection and examination. As a result of the investigative work to date, the
NTSB has determined that the fan midshafts on the GEnx engines fractured or
cracked at the forward end of the shaft where the retaining nut is installed.
GE developed a field ultrasonic inspection method to inspect the fan midshaft in
the area where the fracture and crack occurred that can be accomplished with
the engine still installed on the airplane. To date, all in-service and spare GEnx-
1B engines have been inspected. In addition, all GEnx-2B engines on passenger
airplanes have been inspected. However, the NTSB is aware of approximately 43
GEnx-2B engines on 747-8F cargo airplanes that have not yet been inspected
and is concerned that they are potentially susceptible to a fan midshaft failure.
More recently, a Boeing 747-8F cargo flight, operated by Air Bridge Cargo,
equipped with General Electric GEnx-2B turbofan engines, experienced a loss of
power in one of the engines during the takeoff roll in Shanghai, China. The
airplane had accelerated through 50 knots when the engine's low pressure rotor
speed dropped. The pilot rejected the takeoff and returned to the ramp.
Photographs of the low pressure turbine show damage similar to the GEnx-1B
engine from the Charleston incident. The NTSB will continue to coordinate with
our investigative counterparts in China.
To view NTSB's urgent recommendation letter, visit:
www.ntsb.gov/doclib/recletters/2012/A-12-052-053.pdf
