<< >> NASA ASRS Report 536654, January 2002

A B737-500 flight crew has to ask for a second approach when the ILS localizer and GS for runway 31L is scalloping at mdw, il.

Attributes
ACN	536654
Time
Date	200201
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	msl single value : 3000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 31l other
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 10500 flight time type : 5500
ASRS Report	536654
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : undershoot altitude deviation : crossing restriction not met cabin event : passenger electronic device cabin event : passenger misconduct non adherence : far non adherence : company policies non adherence : clearance other anomaly other spatial deviation
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued advisory controller : issued new clearance flight crew : executed go around
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance Cabin Crew Human Performance Passenger Human Performance Aircraft
Primary Problem	Passenger Human Performance

Narrative:

Navigation interference. Over cht, cleared '10 degrees right intercept localizer runway 31L plan circle runway 22L.' upon tuning localizer frequency and setting course, it appeared we were on the localizer, although visually we appeared south of course. ATC asked if we had intercepted and said we were south of course. The CDI then swung full scale to the other side indicating we were north of course. I turned to center the CDI and we switched to tower. My CDI swung right indicating we were south of course. I noticed the first officer's CDI was swinging the same direction as mine, but moving about half as far. When we saw the runway, we were north of course with CDI's indicating we were south of course. We were high and well north of course when tower asked if we could get down from there. We asked to be turned out to re-enter the pattern. Upon turning outbound we made a PA asking people to please make sure their cell phones and other equipment were turned off. The CDI's immediately became steady and we completed a normal ILS runway 31C circle runway 22L with normal indications and the flight attendants reported that a woman in the forward lounge was talking on her cell phone. As soon as she turned her phone off, our CDI indicated normally.

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Original NASA ASRS Text

Title: A B737-500 FLC HAS TO ASK FOR A SECOND APCH WHEN THE ILS LOC AND GS FOR RWY 31L IS SCALLOPING AT MDW, IL.

Narrative: NAV INTERFERENCE. OVER CHT, CLRED '10 DEGS R INTERCEPT LOC RWY 31L PLAN CIRCLE RWY 22L.' UPON TUNING LOC FREQ AND SETTING COURSE, IT APPEARED WE WERE ON THE LOC, ALTHOUGH VISUALLY WE APPEARED S OF COURSE. ATC ASKED IF WE HAD INTERCEPTED AND SAID WE WERE S OF COURSE. THE CDI THEN SWUNG FULL SCALE TO THE OTHER SIDE INDICATING WE WERE N OF COURSE. I TURNED TO CTR THE CDI AND WE SWITCHED TO TWR. MY CDI SWUNG R INDICATING WE WERE S OF COURSE. I NOTICED THE FO'S CDI WAS SWINGING THE SAME DIRECTION AS MINE, BUT MOVING ABOUT HALF AS FAR. WHEN WE SAW THE RWY, WE WERE N OF COURSE WITH CDI'S INDICATING WE WERE S OF COURSE. WE WERE HIGH AND WELL N OF COURSE WHEN TWR ASKED IF WE COULD GET DOWN FROM THERE. WE ASKED TO BE TURNED OUT TO RE-ENTER THE PATTERN. UPON TURNING OUTBOUND WE MADE A PA ASKING PEOPLE TO PLEASE MAKE SURE THEIR CELL PHONES AND OTHER EQUIP WERE TURNED OFF. THE CDI'S IMMEDIATELY BECAME STEADY AND WE COMPLETED A NORMAL ILS RWY 31C CIRCLE RWY 22L WITH NORMAL INDICATIONS AND THE FLT ATTENDANTS RPTED THAT A WOMAN IN THE FORWARD LOUNGE WAS TALKING ON HER CELL PHONE. AS SOON AS SHE TURNED HER PHONE OFF, OUR CDI INDICATED NORMALLY.

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.