Investigating FOD Damage Part 2

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Investigating FOD DamagePart 2
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Example 1 DC-10 2

• Vibrations in 2 engine during take-off
• Take-off aborted
• Engine then pulled for fan blade damage

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Example 1 DC-10 2
Good place to sample
Circular symmetry
Apparent thread marks
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Example 1 DC-10 2
LE fan blade damage
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Example 1 DC-10 2 Analysis

• Most of the impacts occurred to the LE concave
  surface, indicating that the impacting object
  entered through the intake
• There is circular damage symmetry
• There is rectangular damage symmetry
• There are apparent thread marks
• Blades are made of titanium

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Example 1 DC-10 2
FAST samples reveal nickel - chrome plated steel
tool material
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Example 1 DC-10 2 Analysis
Source of thread marks
A nickel - chrome plated crescent wrench accounts
for the damage
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Example 2 Blade fracture in HPC

• 6 HPC blades were submitted for analysis
• The 3 blades on the right are HPC-7 blades
• The 3 blades on the left are HPC-9 blades
• An HPC-9 blade is broken

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Example 2 Blade fracture in HPC
Two HPC-7 blades with TE cracks
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Example 2 Blade fracture in HPC

• HPC-9 blade shows LE impact
• Fatigue crack growth emanates from LE impact
• Knife edge fast fracture shear lip at TE

TE shear lip
LE impact
Fatigue
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Example 2 Blade fracture in HPC
1000X Scanning electron microscope (SEM) photo
showing fatigue striations in fatigue crack
growth zone of HPC-9 blade
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Example 2 Blade fracture in HPC
500X SEM photo showing ductile dimples in TE fast
fracture zone of HPC-9 blade
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Example 2 Blade fracture in HPC
Aluminum fastener material found as foreign debris
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Example 3 B-727 2 Engine

• B-727 had been airborne approximately 1 hour.
• The plane was cleared for a climb from FL 300 to
  Fl 340.
• During the level off, the 2 engine
  disintegrated.
• What happened?

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Example 3 B-727 2 Engine
Blade remnants
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Example 3 B-727 2 Engine
These circular shaped impacts are not the result
of liberated airfoil and are good places to take
FAST samples
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Example 3 B-727 2 Engine
Nickel-chrome plated socket material found as
foreign debris
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Example 4 Fan Blade Damage Found on Arrival
Two fan blades found with LE tip curls. Blade
tips are curled in the direction opposite to
engine rotation.
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Example 4 Fan Blade Damage Found on Arrival

• Only two fan blades damaged
• The blade tip curls are smooth with no obvious
  impact deformation
• The energy of the impact did not result in blade
  tearing
• FAST samples revealed no foreign debris
• This is consistent with ice damage
• The ice ingestion occurred during a low power
  setting, probably during the approach phase
• The scratch on one of the fan blades below the
  tip curl was due to the two blades being shipped
  together for analysis and not protected from
  contact with one another

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Example 5 Fan Blade Damage FOA

• Damage found on arrival (FOA)
• Only three blades were damaged
• Impacts resulted in blade tearing and loss of
  material
• The impacts are smooth without obvious secondary
  impact deformation

Concave surfaces shown, LE at top
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Example 5 Fan Blade Damage FOA
Large smooth blade curl
This blade is torn
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Example 5 Fan Blade Damage FOA

• There was sufficient impact energy to result in
  blade tearing, which indicates the impacts
  occurred at a high power setting, probably during
  the takeoff roll
• Black light test was negative for a bird strike
• FAST samples revealed no foreign debris, which is
  consistent with ice damage
• This example differs from example 4 in power
  settings at time of impact