An light transport, along with 2 other non-reporting air carrier aircraft, found themselves on the GS but low over the ground at a DME fix to runway 17L at dfw.

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Attributes
ACN	229949
Time
Date	199212
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dfw
State Reference	TX
Altitude	msl bound lower : 1500 msl bound upper : 2300
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tower : dfw
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Navigation In Use	ils localizer & glide slope : dfw Other Other
Flight Phase	descent : approach
Route In Use	approach : straight in
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent : approach
Route In Use	approach : straight in
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 285 flight time total : 10500 flight time type : 5800
ASRS Report	229949
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : overshoot other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other

Narrative:

We were told to cross penny intersection at 4000 ft. Slowed to 170 KTS and cleared for the ILS 17L approach to dfw. We were then handed over to the tower. Inside penny intersection, we intercepted the GS. All indications normal, no flags, identify ok, first officer flying command bars on EFIS system. We were about 4 mi behind an air carrier B, an large transport, on the approach, experiencing some light turbulence. Just prior to jiffy OM, we were still on GS when I glanced at the DME and saw we were lower than we should be for that distance from the airport. We stopped our descent at 1500 MSL. Tower then came on and advised us we were 1500 MSL and asked if there was a problem. We stated that we had a bad indication on the GS and would go to localizer mins. The air carrier B flight ahead of us on the approach then stated that they also had a problem with the GS. Air carrier a flight Y behind us stated the same thing. The ceiling was 900 ft ragged and we saw the airport from 7 mi out. We landed with no further problem. Fatigue was the major factor in not noticing the altitude discrepancy sooner. We suspect the GS interference may have been from construction activity near the runway or an aircraft crossing the runway.

Original NASA ASRS Text

Title: AN LTT, ALONG WITH 2 OTHER NON-RPTING ACR ACFT, FOUND THEMSELVES ON THE GS BUT LOW OVER THE GND AT A DME FIX TO RWY 17L AT DFW.

Narrative: WE WERE TOLD TO CROSS PENNY INTXN AT 4000 FT. SLOWED TO 170 KTS AND CLRED FOR THE ILS 17L APCH TO DFW. WE WERE THEN HANDED OVER TO THE TWR. INSIDE PENNY INTXN, WE INTERCEPTED THE GS. ALL INDICATIONS NORMAL, NO FLAGS, IDENT OK, FO FLYING COMMAND BARS ON EFIS SYS. WE WERE ABOUT 4 MI BEHIND AN ACR B, AN LGT, ON THE APCH, EXPERIENCING SOME LIGHT TURB. JUST PRIOR TO JIFFY OM, WE WERE STILL ON GS WHEN I GLANCED AT THE DME AND SAW WE WERE LOWER THAN WE SHOULD BE FOR THAT DISTANCE FROM THE ARPT. WE STOPPED OUR DSCNT AT 1500 MSL. TWR THEN CAME ON AND ADVISED US WE WERE 1500 MSL AND ASKED IF THERE WAS A PROB. WE STATED THAT WE HAD A BAD INDICATION ON THE GS AND WOULD GO TO LOC MINS. THE ACR B FLT AHEAD OF US ON THE APCH THEN STATED THAT THEY ALSO HAD A PROB WITH THE GS. ACR A FLT Y BEHIND US STATED THE SAME THING. THE CEILING WAS 900 FT RAGGED AND WE SAW THE ARPT FROM 7 MI OUT. WE LANDED WITH NO FURTHER PROB. FATIGUE WAS THE MAJOR FACTOR IN NOT NOTICING THE ALT DISCREPANCY SOONER. WE SUSPECT THE GS INTERFERENCE MAY HAVE BEEN FROM CONSTRUCTION ACTIVITY NEAR THE RWY OR AN ACFT XING THE RWY.

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.