<< >> NASA ASRS Report 599741, November 2003

A canadair CL65 at FL270 declared an emergency and diverted due to essential bus failure. Air driven generator deployed to power essential bus.

Attributes
ACN	599741
Time
Date	200311
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : zzz.artcc
State Reference	US
Altitude	msl single value : 23000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air carrier
Make Model Name	Regional Jet CL65, Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 110 flight time total : 15000 flight time type : 135
ASRS Report	599741
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : eicas warning other flight crewa other flight crewb
Resolutory Action	flight crew : declared emergency flight crew : diverted to another airport
Consequence	other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Flight abcd departed ZZZ en route to ZZZZ. Reaching 27000 ft we had a master caution for the AC essential bus. Referenced the company flight manual. Air-driven generator automatic deployed. Made the decision to divert to ZZZ1. Declared an emergency. Contacted company via radio. PIC flew and talked to ATC. Sic ran checklist, and communicated with flight attendant, passenger, and company. Landed at ZZZ1 without any further problems. Maintenance found a bad relay in the system. Callback conversation with reporter revealed the following information: the reporter stated the EICAS warning, 'AC essential bus' came on and then the air-driven generator deployed and the AC essential bus was powered. The reporter said being powered by the air-driven generator, a great number of systems are not operating due to the limitations of the air-driven generator. The reporter stated maintenance found the essential power transfer relay at fault and it was replaced.

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Original NASA ASRS Text

Title: A CANADAIR CL65 AT FL270 DECLARED AN EMER AND DIVERTED DUE TO ESSENTIAL BUS FAILURE. AIR DRIVEN GENERATOR DEPLOYED TO PWR ESSENTIAL BUS.

Narrative: FLT ABCD DEPARTED ZZZ ENRTE TO ZZZZ. REACHING 27000 FT WE HAD A MASTER CAUTION FOR THE AC ESSENTIAL BUS. REFERENCED THE COMPANY FLT MANUAL. AIR-DRIVEN GENERATOR AUTO DEPLOYED. MADE THE DECISION TO DIVERT TO ZZZ1. DECLARED AN EMER. CONTACTED COMPANY VIA RADIO. PIC FLEW AND TALKED TO ATC. SIC RAN CHKLIST, AND COMMUNICATED WITH FLT ATTENDANT, PAX, AND COMPANY. LANDED AT ZZZ1 WITHOUT ANY FURTHER PROBS. MAINT FOUND A BAD RELAY IN THE SYSTEM. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE EICAS WARNING, 'AC ESSENTIAL BUS' CAME ON AND THEN THE AIR-DRIVEN GENERATOR DEPLOYED AND THE AC ESSENTIAL BUS WAS POWERED. THE RPTR SAID BEING POWERED BY THE AIR-DRIVEN GENERATOR, A GREAT NUMBER OF SYSTEMS ARE NOT OPERATING DUE TO THE LIMITATIONS OF THE AIR-DRIVEN GENERATOR. THE RPTR STATED MAINT FOUND THE ESSENTIAL PWR TRANSFER RELAY AT FAULT AND IT WAS REPLACED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.