Air carrier on coupled ILS approach to bdl experienced glide slope interference and pitch up at 1800...

Attributes
ACN	830234
Time
Date	200904
Local Time Of Day	1801-2400
Place
Locale Reference	BDL.Airport
State Reference	CT
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 237 Flight Crew Type 8800
Events
Anomaly	Other Glideslope Interference

Narrative:

After joining GS to runway 24 bdl during an autopilot coupled approach; tower cleared another jet for departure. As that jet entered the ILS safety zone; the GS indication suddenly deflected to showing 1 dot low. Aircraft pitched up to follow erroneous indication and slowed to 3 KTS below reference during recovery. GS then quickly showed us high by 1/4 dot and then stabilized. ATC should not clear anyone into ILS zone while another jet is on GS.

Original NASA ASRS Text

Title: Air Carrier on coupled ILS approach to BDL experienced glide slope interference and pitch up at 1800 when ATC cleared another aircraft for takeoff; reporter suggesting ATC refrain from same type operations.

Narrative: After joining GS to Runway 24 BDL during an autopilot coupled approach; Tower cleared another jet for departure. As that jet entered the ILS safety zone; the GS indication suddenly deflected to showing 1 dot low. Aircraft pitched up to follow erroneous indication and slowed to 3 KTS below reference during recovery. GS then quickly showed us high by 1/4 dot and then stabilized. ATC should not clear anyone into ILS zone while another jet is on GS.

Data retrieved from NASA's ASRS site as of April 2012 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.

Air carrier on coupled ILS approach to bdl experienced glide slope interference and pitch up at 1800 when ATC cleared another aircraft for takeoff; reporter suggesting ATC refrain from same type operations.