Cessna 421A N1477D

Summary

On 25 July 2000 at about 19:50 local time, a Cessna 421A registered N1477D was involved in an accident near Homewood, Mississippi, United States. 6 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

25 July 2000 at 19:50

Classification

Accident

Location

Homewood, Mississippi, United States

Coordinates

32.3501, -89.4692

Aircraft

Cessna 421A

Registration

N1477D

Category

Airplane

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Destin → Tulsa

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

MIA00LA225

Nobody was injured.

The inadequate installation of the right propeller by the mechanic for his failure to properly torque the eight nuts resulting in fatigue failure of the studs and separation of the right propeller during cruise flight. Findings in the investigation were 1) the mechanic who installed the right propeller used un-calibrated torque wrenches, and 2) the mechanic who installed the right propeller used an outdated Service Manual.

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

Read the full NTSB narrative

During cruise flight, a slight vibration was felt and the right propeller completely separated contacting the right horizontal stabilizer. The flight diverted and landed uneventfully. The right engine No. 3 cylinder connecting rod failed; evidence of exposure to elevated temperatures and higher stress fatigue crack propagation was noted. Extensive fretting noted on the faying surfaces of the right propeller gear and hub, and on both sides of the propeller bulkhead and fillet assembly. The holes in the propeller bulkhead assembly and propeller gear were elongated/eggshaped. Fatigue noted on all eight studs; wear noted on the shanks of seven studs; the eighth stud was not examined. Four of the recovered seven spacers were damaged shortening their length. Only two of the eight fractured studs were extended the specified minimum distance beyond the nut. No discrepancies with the threads in the hub holes of the left propeller, or to the threads in the hub holes of the right propeller that were checked. Overstress failure noted on the fractured propeller blade from the right propeller. The mechanic who installed the right propeller used un-calibrated torque wrenches and an outdated Service Manual. The airplane had accumulated approximately 50 hours since installation of the right propeller.

Quoted verbatim from the NTSB record.