Continued CAT ii approach by air carrier with below legal limits.

Attributes
ACN	123256
Time
Date	198909
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dtw
State Reference	MI
Altitude	msl bound lower : 2900 msl bound upper : 2900
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dtw
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent : approach landing : missed approach
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time total : 13000
ASRS Report	123256
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	inflight encounter : weather non adherence : published procedure non adherence : far non adherence other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Dtw CAT ii ILS 3R: RVR 1200' and we were on final for CAT ii approach on runway 3R dtw, mi. We captured the glide slope at 3000' when approach control changed us to tower. In landing confign and passing 2900' on the glide slope, I called the tower. They gave us an RVR of 1000'. Thinking we were in the final approach segment because we were on the glide path, I continued the approach. We missed the approach because we did not see the runway. Later I checked on the rules for final approach segment for an ILS and discovered that it actually starts at 2700' and on the glide path for this approach not on the glide path as I thought.

Original NASA ASRS Text

Title: CONTINUED CAT II APCH BY ACR WITH BELOW LEGAL LIMITS.

Narrative: DTW CAT II ILS 3R: RVR 1200' AND WE WERE ON FINAL FOR CAT II APCH ON RWY 3R DTW, MI. WE CAPTURED THE GLIDE SLOPE AT 3000' WHEN APCH CTL CHANGED US TO TWR. IN LNDG CONFIGN AND PASSING 2900' ON THE GLIDE SLOPE, I CALLED THE TWR. THEY GAVE US AN RVR OF 1000'. THINKING WE WERE IN THE FINAL APCH SEGMENT BECAUSE WE WERE ON THE GLIDE PATH, I CONTINUED THE APCH. WE MISSED THE APCH BECAUSE WE DID NOT SEE THE RWY. LATER I CHECKED ON THE RULES FOR FINAL APCH SEGMENT FOR AN ILS AND DISCOVERED THAT IT ACTUALLY STARTS AT 2700' AND ON THE GLIDE PATH FOR THIS APCH NOT ON THE GLIDE PATH AS I THOUGHT.

Data retrieved from NASA's ASRS site as of August 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.