Flight crew of mdt departed cleared altitude prior to glideslope intercept while flying ILS approach...

Attributes
ACN	571839
Time
Date	200301
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dfw.airport
State Reference	TX
Altitude	msl bound lower : 2300 msl bound upper : 3000
Environment
Flight Conditions	Marginal
Light	Dusk
Aircraft 1
Controlling Facilities	tower : dfw.tower tower : pwk.tower
Operator	common carrier : air carrier
Make Model Name	Medium Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 36l ils y other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 3300 flight time type : 1700
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : company policies non adherence : far non adherence : published procedure non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : altimeter other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Chart Or Publication Company Flight Crew Human Performance FAA ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation
Situations
Chart	approach : dfw ils y 36l
Publication	Commercial Chart Supplier

Narrative:

I completed a commercial chart revision dated 1/fri/03 . The previous evening taking note of the effective date of 1/thu/03. On approach to dfw on 1/fri/03, we were given the 'Y 36L ILS.' I recalled during the revision that a note on the chart for this particular approach said 'procedure not in database.' thus, I discarded the chart, mistakenly thinking this note applied to us. Neither the pilot flying nor I had the 'Y 36L ILS' approach chart. Rather than accept on frequency embarrassment, we pressed on, plugging in the localizer frequency for 'ILS 36L.' (111.9). Level at 3000 ft, thin overcast of 2100 ft, 7 miles visibility. We became confused with an airport south of dfw (it also had a north/south alignment). Believing he was high, the PF started to descend, losing 700 ft before realizing error. He then climbed to original altitude of 3000 ft. At some point, I asked to confirm the frequency for the approach. Tower replied '110.55. It lines you up with runway 36R.' no comment was heard from tower about our altitude. We landed without incident. What caused this was 1) discarding the approach chart and 2) continuing the approach (visibility was good with a very thin overcast). Lesson about prematurely discarding charts has most certainly been learned. Would like to see more information regarding the purpose of 'Y ILS 36L' or 'Z ILS 18L' apches. Why the 'Y' or 'Z' designation? Callback conversation with reporter revealed the following information: callback to reporter was completed 13 days after initial review by analyst. At this date reporter stated that he was still unaware of the meaning and intent of the phrase 'procedure not in database' on the approach plates, nor with the implications of the modifiers 'Y' and 'Z' in the procedure name. He reiterated that the lack of information regarding these matters led both he and his captain to simply discard the plates as unusable for their operation.

Original NASA ASRS Text

Title: FLC OF MDT DEPARTED CLRED ALT PRIOR TO GLIDESLOPE INTERCEPT WHILE FLYING ILS APCH FOR WHICH THEY HAD EARLIER DISCARDED APCH PLATES. UNUSUAL APCH IDENTIFICATION AND TERMINOLOGY ON THE CHART, NOT ADDRESSED BY THE PUBLISHER, CONTRIBUTED TO THE CONFUSION.

Narrative: I COMPLETED A COMMERCIAL CHART REVISION DATED 1/FRI/03 . THE PREVIOUS EVENING TAKING NOTE OF THE EFFECTIVE DATE OF 1/THU/03. ON APCH TO DFW ON 1/FRI/03, WE WERE GIVEN THE 'Y 36L ILS.' I RECALLED DURING THE REVISION THAT A NOTE ON THE CHART FOR THIS PARTICULAR APCH SAID 'PROC NOT IN DATABASE.' THUS, I DISCARDED THE CHART, MISTAKENLY THINKING THIS NOTE APPLIED TO US. NEITHER THE PLT FLYING NOR I HAD THE 'Y 36L ILS' APCH CHART. RATHER THAN ACCEPT ON FREQ EMBARRASSMENT, WE PRESSED ON, PLUGGING IN THE LOCALIZER FREQ FOR 'ILS 36L.' (111.9). LEVEL AT 3000 FT, THIN OVCST OF 2100 FT, 7 MILES VIS. WE BECAME CONFUSED WITH AN ARPT S OF DFW (IT ALSO HAD A N/S ALIGNMENT). BELIEVING HE WAS HIGH, THE PF STARTED TO DSND, LOSING 700 FT BEFORE REALIZING ERROR. HE THEN CLBED TO ORIGINAL ALT OF 3000 FT. AT SOME POINT, I ASKED TO CONFIRM THE FREQ FOR THE APCH. TWR REPLIED '110.55. IT LINES YOU UP WITH RWY 36R.' NO COMMENT WAS HEARD FROM TWR ABOUT OUR ALT. WE LANDED WITHOUT INCIDENT. WHAT CAUSED THIS WAS 1) DISCARDING THE APCH CHART AND 2) CONTINUING THE APCH (VIS WAS GOOD WITH A VERY THIN OVCST). LESSON ABOUT PREMATURELY DISCARDING CHARTS HAS MOST CERTAINLY BEEN LEARNED. WOULD LIKE TO SEE MORE INFO REGARDING THE PURPOSE OF 'Y ILS 36L' OR 'Z ILS 18L' APCHES. WHY THE 'Y' OR 'Z' DESIGNATION? CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CALLBACK TO RPTR WAS COMPLETED 13 DAYS AFTER INITIAL REVIEW BY ANALYST. AT THIS DATE RPTR STATED THAT HE WAS STILL UNAWARE OF THE MEANING AND INTENT OF THE PHRASE 'PROC NOT IN DATABASE' ON THE APCH PLATES, NOR WITH THE IMPLICATIONS OF THE MODIFIERS 'Y' AND 'Z' IN THE PROC NAME. HE REITERATED THAT THE LACK OF INFO REGARDING THESE MATTERS LED BOTH HE AND HIS CAPT TO SIMPLY DISCARD THE PLATES AS UNUSABLE FOR THEIR OP.

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.

Flight crew of mdt departed cleared altitude prior to glideslope intercept while flying ILS approach for which they had earlier discarded approach plates. Unusual approach identification and terminology on the chart, not addressed by the publisher, contributed to the confusion.