Reporter states that when DC10, B747 type freighters roll to the end of runway 4R and turn sideways exiting the runway, the localizer is deflected to the left for a short period of time. Reporter had previously been on an autoplt coupled approach and got a hard left turn to chase the localizer.

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Attributes
ACN	377764
Time
Date	199708
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	agl bound lower : 600 agl bound upper : 600
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tower : ord
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Route In Use	arrival other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	ground other : taxi
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	377764
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
ATC Facility	other physical facility

Narrative:

I was expecting this to happen last night since I've experienced this very thing before on this runway. Following a DC10 on runway 4R at ord, with instructions to roll to the end. When the preceding widebody transport aircraft rolls to the end of runway 4R and turns sideways exiting the runway, it deflects the localizer to the left about 1/2 DOT for a short period of time. Last night it was a DC10, I've experienced the same thing following a B747. Maybe it has to do with the fact that these aircraft were freighters and their fuselages were full of freight which might block the localizer beam more than a passenger aircraft would. We should get this ILS flight tested with a widebody transport aircraft blocking the localizer as if it was turning off at the end. I'm sure the result will be that the localizer is deflected significantly to the left. Last night I was hand- flying with the runway in sight so I just watched the localizer swing to the left and then come back. In the previous incident the autoplt was coupled in VMC and I got a hard left turn to chase the localizer -- not fun.

Original NASA ASRS Text

Title: RPTR STATES THAT WHEN DC10, B747 TYPE FREIGHTERS ROLL TO THE END OF RWY 4R AND TURN SIDEWAYS EXITING THE RWY, THE LOC IS DEFLECTED TO THE L FOR A SHORT PERIOD OF TIME. RPTR HAD PREVIOUSLY BEEN ON AN AUTOPLT COUPLED APCH AND GOT A HARD L TURN TO CHASE THE LOC.

Narrative: I WAS EXPECTING THIS TO HAPPEN LAST NIGHT SINCE I'VE EXPERIENCED THIS VERY THING BEFORE ON THIS RWY. FOLLOWING A DC10 ON RWY 4R AT ORD, WITH INSTRUCTIONS TO ROLL TO THE END. WHEN THE PRECEDING WDB ACFT ROLLS TO THE END OF RWY 4R AND TURNS SIDEWAYS EXITING THE RWY, IT DEFLECTS THE LOC TO THE L ABOUT 1/2 DOT FOR A SHORT PERIOD OF TIME. LAST NIGHT IT WAS A DC10, I'VE EXPERIENCED THE SAME THING FOLLOWING A B747. MAYBE IT HAS TO DO WITH THE FACT THAT THESE ACFT WERE FREIGHTERS AND THEIR FUSELAGES WERE FULL OF FREIGHT WHICH MIGHT BLOCK THE LOC BEAM MORE THAN A PAX ACFT WOULD. WE SHOULD GET THIS ILS FLT TESTED WITH A WDB ACFT BLOCKING THE LOC AS IF IT WAS TURNING OFF AT THE END. I'M SURE THE RESULT WILL BE THAT THE LOC IS DEFLECTED SIGNIFICANTLY TO THE L. LAST NIGHT I WAS HAND- FLYING WITH THE RWY IN SIGHT SO I JUST WATCHED THE LOC SWING TO THE L AND THEN COME BACK. IN THE PREVIOUS INCIDENT THE AUTOPLT WAS COUPLED IN VMC AND I GOT A HARD L TURN TO CHASE THE LOC -- NOT FUN.

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.