FK10 crew had false radio altimeter readings on approach at cyzd.

Attributes
ACN	457620
Time
Date	199912
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : cyzd.airport
State Reference	ON
Altitude	msl single value : 2100
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Fokker 100
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 24l other
Flight Phase	descent : approach
Route In Use	approach : instrument precision approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	457620
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment : gpws aircraft equipment other aircraft equipment : radio altimeter other flight crewa other flight crewb
Resolutory Action	none taken : anomaly accepted
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Erroneous radio altimeter indications. Established on the ILS runway 24L approach into yyz approximately 7 DME directly abeam toronto downsview airport, the #1 radio altimeter became erratic. Several aural GPWS warnings sounded -- too low gear, too low flaps, and the 50, 40, 30, 20 callouts sounded as well. The erratic #1 radio altimeter occurred on flight X as well as flight Y. The aural warnings occurred on flight X. There appears to be an NDB on the final approach segment as well. I am wondering if the NDB could have given us the erroneous indications we experienced.

Original NASA ASRS Text

Title: FK10 CREW HAD FALSE RADIO ALTIMETER READINGS ON APCH AT CYZD.

Narrative: ERRONEOUS RADIO ALTIMETER INDICATIONS. ESTABLISHED ON THE ILS RWY 24L APCH INTO YYZ APPROX 7 DME DIRECTLY ABEAM TORONTO DOWNSVIEW ARPT, THE #1 RADIO ALTIMETER BECAME ERRATIC. SEVERAL AURAL GPWS WARNINGS SOUNDED -- TOO LOW GEAR, TOO LOW FLAPS, AND THE 50, 40, 30, 20 CALLOUTS SOUNDED AS WELL. THE ERRATIC #1 RADIO ALTIMETER OCCURRED ON FLT X AS WELL AS FLT Y. THE AURAL WARNINGS OCCURRED ON FLT X. THERE APPEARS TO BE AN NDB ON THE FINAL APCH SEGMENT AS WELL. I AM WONDERING IF THE NDB COULD HAVE GIVEN US THE ERRONEOUS INDICATIONS WE EXPERIENCED.

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.