Israel 1125 N511WA

Summary

On 3 April 2000 at about 00:30 local time, a Israel 1125 registered N511WA was involved in an incident near Pine Knot, Kentucky, United States. 4 people were on board and nobody was injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

3 April 2000 at 00:30

Classification

Incident

Location

Pine Knot, Kentucky, United States

Coordinates

36.6808, -84.3992

Aircraft

Israel 1125

Registration

N511WA

Category

Airplane

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Executive/Corporate

Phase of flight

Not recorded

Route

Naples → Cincinnati

Aircraft damage

Not recorded

Weather

VMC

Light

Night/Dark

NTSB number

NYC00IA116

Nobody was injured.

The partial failure of an inverter and the inadequate design of the electrical circuit breaker system.

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

Read the full NTSB narrative

While in cruise flight, the flightcrew selected "GPS" on the pilot's Electronic Horizontal Situation Indicator (EHSI). The number one inverter then began to malfunction and produce lower than normal voltage. As the voltage decreased, the vertical gyroscopes began to slow down and the displays on the Electronic Attitude Display Indicators (EADI) "blacked out," without any warning from the master caution panel. Shortly thereafter, heading warning flags appeared and the compass cards locked in position on both EHSI's. Due to the decreased voltage, the motors of the directional gyroscopes drew higher-than-normal amperage, and blew their respective internal 0.75-amp fuses. When the fuses blew, the load was decreased on the number one inverter, and the voltage output increased back to normal levels; however, because of their inaccessibility, the flightcrew could not reset the fuses. Additionally, a sensing relay, pre-set to de-energize at about 40-volts AC, did not activate to illuminate an "AC FAIL" light on the master caution annunciator panel. With the normal voltage levels restored, the vertical gyroscopes began to accelerate, and approximately 8 to 10 minutes later, the EADI displays returned. The flight landed uneventfully. After the incident, the airplane manufacturer issued an Alert Service Bulletin providing instructions to replace existing low voltage sensing relays with higher accuracy relays capable of providing a warning at higher voltages and to replace the 3-amp Directional Gyros circuit breakers on the overhead circuit breaker panel, with 0.5-amp circuit breakers, enabling disconnection of power to the EHSI's prior to their internal 0.75-amp blowing.

Quoted verbatim from the NTSB record.