Bell UH-1L N70410

Summary

On 18 September 1995 at about 18:00 local time, a Bell UH-1L registered N70410 was involved in an accident near Grace, Idaho, United States. One person was on board and one was seriously injured. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

18 September 1995 at 18:00

Classification

Accident

Location

Grace, Idaho, United States

Coordinates

42.5110, -111.7406

Aircraft

Bell UH-1L

Registration

N70410

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

SEA95LA221

1 person was seriously injured.

the fatigue failure of the centrifugal impeller and the lack of suitable terrain for a forced landing. Factors contributing to the accident were: the lack of required compliance with the FAA Airworthiness Directive by the operator, the insufficiently defined FAA procedure within the AD (failure to include the -07 impeller and establish a cycle count program), and inadequate rotor RPM.

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

Read the full NTSB narrative

During log slinging operations the restricted category UH-1L rotorcraft's T53-L-13B military engine experienced a total loss of power. The pilot dropped the log load and autorotated into a small, upsloping, cleared area within the surrounding wooded terrain landing hard. Postcrash examination of the engine revealed that the centrifugal impeller had separated due to fatigue cracking in one of the drain holes. An Airworthiness Directive (AD) had been issued relative to the -08 impeller but did not include the -07 impeller (installed in the accident engine). The -07 and -08 impellers are essentially identical with the exception that the -07 impeller is found on military variants of the engine whereas the -08 is found only on civilian variants. As the -07 impeller was not included in the AD, the operator was not required to conduct the appropriate inspections described in the mandated service bulletin. Additionally, the AD did not require a cycle count for the impeller as addressed in the service bulletin, thus rendering the service bulletin unusable even if it had been mandated for the -07 impeller.

Quoted verbatim from the NTSB record.