Cessna 525 N123JN

Summary

On 29 August 1996 at about 18:30 local time, a Cessna 525 registered N123JN was involved in an incident near Milwaukee, Wisconsin, United States. 3 people were on board and nobody was injured. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

29 August 1996 at 18:30

Classification

Incident

Location

Milwaukee, Wisconsin, United States

Coordinates

42.9805, -87.9002

Aircraft

Cessna 525

Registration

N123JN

Category

Airplane

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Business

Phase of flight

Not recorded

Aircraft damage

Minor

Weather

VMC

Light

Day

NTSB number

CHI96IA320

Nobody was injured.

an uncontained failure of a high pressure turbine disk blade retention post due to fatigue. A factor relating to the incident was: inadequate design of the high pressure turbine disk. Fretting on the leading side of the lobe near the fracture origin may have contributed to premature initiation of the fatigue.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

After being cleared to climb from 6,000', the pilot began advancing the throttles to climb power, when he heard a loud bang & noted indications of a #2 engine failure. He secured the #2 engine & made an uneventful landing. Examination of the failed Williams-Rolls FJ44-1A engine revealed it had sustained an uncontained high pressure turbine (HPT) disk blade retention post failure. Examination of the HTP disk (PN 48629) showed that a blade retention post had fractured adjacent to the bottom of the blade slots & that 3 adjacent HPT blades had broken loose. Subsequently, the upper portion of the fuel-oil heat exchanger mount pad was fractured, which resulted in an oil leak. Metallurgical examination revealed the primary failure was the release of a blade retaining lobe just below a fret zone. Creep fatigue was found at the failed blade retaining holes. No evidence of gross overheating was noted. The failed disk was of an 'older' design. As a result of the incident, Williams-Rolls Alert Service Bulletins No. FJ44-A72-30 and -31 were issued to describe a procedure for eddy current inspection (ECI) of the high pressure turbine (HPT) disk blade retention posts to locate possible cracks and to describe a procedure for replacing the existing HPT disks with an advanced-design HPT disk. Also, Airworthiness Directive (AD) 97-01-05 was issued to require initial and recurring ECIs of the HPT disks and for replacement of FJ44-1A HPT disks with improved disks. A more durable fuel-oil mounting pad was being developed for the FJ44-2 engine.

Quoted verbatim from the NTSB record.