Pilot Debrief

BOMBARDIER INC CL 600 2B19 near Baltimore, MD — 2017-01-23

Final reportENG17IA008
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Date
2017-01-23
Location
Baltimore, MD, USA
Airport
BWI
Aircraft
BOMBARDIER INC CL 600 2B19
Registration
N8986B
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Initial climb

Probable cause

A Bombardier CRJ200 No. 2 engine failure due to the separation of a fan blade airfoil at a low cycle fatigue crack that originated at the forward fan blade pin hole attachment. The separated fan blade had previously undergone a hot form repair and both metallurgical analysis and repair records indicated that the lance/shot peen step required to restore sufficient residual stress levels to the blade material was not completed.

NTSB narrative

The No. 2 engine fan blade airfoil separation was caused by a low cycle fatigue crack that originated at the forward blade pin hole attachment tang due to insufficient residual stress (hoop stress) levels in the Ti-8-1-1 blade material. The fan blade had undergone a hot form repair following a bird strike incident in December 2007 to restore the blade profile. During the hot form repair process the blade was placed in a ceramic die and heated to 1150-1200oF to restore the blade geometry. The hot form process relieved the compressive residual stress layer in the fan blade and the layer was not properly restored with a lance peen/shot peen step as called out in the GE Standard Repair Manual. There was visual evidence of 100% lance peen/shot peen coverage on the fan blade attachment pin holes surfaces that was identified during the materials lab examination, but the peen marks were most likely formed during the original fan blade manufacturing process. When the fan blade airfoil separated during the incident it was contained by the engine fan case containment system. The fan blade impact with the fan case containment system resulted in a bulge in the Kevlar wrap that damaged the attaching hardware at the fan cowl flanges, and the cowl subsequently separated when exposed to the jet stream. When the fan cowls separated from the engine they impacted the thrust reverser translating cowl and core cowl and resulted in gouging and surface buckling. The fan blade airfoil separation caused a fan imbalance that led to high No. 2 engine vibration levels. The high vibration levels caused the engine transition case to LPT flange separation, AGB housing fracture, and starter damage.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Perform thorough inspection of fan blades before flight to prevent failure.

NTSB coding

  • Powerplant sys/comp malf/fail · Enroute-climb to cruise

Evidence available

  • 3 docket documents
View NTSB final reportView NTSB docket

Docket documents3

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