Boeing 707 338C N624RH

Summary

On 10 April 2015 at about 22:00 local time, a Boeing 707 338C registered N624RH, operated by Omni Air International, was involved in an incident near Victorville, California, United States. 5 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

10 April 2015 at 22:00

Classification

Incident

Location

Victorville, California, United States

Coordinates

34.5975, -117.3831

Aircraft

Boeing 707 338C

Registration

N624RH

Category

Airplane

Year built

1968

Operator

Omni Air International

Operating rule

Part 91: General Aviation

Purpose of flight

Positioning

Phase of flight

Not recorded

Route

Port Hueneme → Brunswick

Aircraft damage

Minor

Weather

VMC

Light

Not Reported

NTSB number

ENG15IA017

Nobody was injured.

the fracture of one 1st stage turbine blade from a high cycle fatigue crack that originated from a break in the coating on the leading edge of the blade. The cause for the break in the coating could not be determined. Contributing to the uncontained release of turbine material was the yielding and rupture of the turbine exhaust case wall after turbine debris collected at probes in the case.

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

Read the full NTSB narrative

The airplane, a Boeing 707, was being repositioned from Pt. Mugu Naval Air Station, California to Brunswick, Georgia to remove and replace the No. 1 engine, a Pratt & Whitney JT3D-3B turbofan, because of excessive oil consumption.  During the takeoff roll after V1 and during the climb, the No. 1 engine's exhaust gas temperature (EGT) began to increase and continued to increase towards the red line limit requiring the flight engineer to retard the throttle several times to prevent an exceedance.  The flight crew leveled off the airplane and were retarding the No. 1 engine's throttle when a severe vibration developed.  Smoke and debris were observed trailing from the No. 1 engine.  The crew shutdown the No. 1 engine, declared an emergency, and diverted to Victorville, California where they landed without further incident.  The examination of the engine revealed damage to the low pressure turbine blades as well as a hole in the turbine case that was coincident with a hole in the nacelle.  The disassembly of the engine revealed one first stage turbine blade was fractured about an inch above the blade root platform.  The metallurgical examination of the fractured blade that was done at both the NTSB's and Pratt & Whitney's materials laboratories revealed a high cycle fatigue fracture the originated from multiple origins along the leading edge at the interface between the coating and the base metal.  The metallurgical examination also revealed just below the primary fracture a secondary crack that was of similar morphology to the primary fracture.  The metallurgical examination showed that the coating chemistry and thickness conformed to the requirements.  The maintenance records showed that the coating had been applied at the time of the last overhaul of the blades.  Although the coating conformed to requirements for chemistry and thickness, the presence of two adjacent cracks that originated at the coating interface suggests an issue with the application of the coating.  The cause of the breaks in the coating could not be determined.

Quoted verbatim from the NTSB record.