C550 on ILS runway 2L approach to dpa is unable to maintain altitude during ILS attempt due to WX.

Attributes
ACN	600743
Time
Date	200311
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : dpa.airport
State Reference	IL
Altitude	msl bound lower : 3000 msl bound upper : 4000
Environment
Flight Conditions	IMC
Weather Elements	Turbulence Windshear Thunderstorm
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	general aviation : corporate
Make Model Name	Citation II S2/Bravo
Operating Under FAR Part	Part 91
Navigation In Use	ils localizer & glide slope : 2l
Flight Phase	descent : approach
Route In Use	approach : instrument precision arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 12800 flight time type : 120
ASRS Report	600743
Person 2
Affiliation	company : corporate
Function	flight crew : captain
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather other anomaly
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment flight crew : overrode automation flight crew : regained aircraft control flight crew : took precautionary avoidance action
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Weather
Primary Problem	Weather

Narrative:

Our citation jet was being vectored for the ILS runway 2L at dpa airport by chicago approach. After receiving a clearance to shoot the approach, we encountered severe convective activity outside the FAF and were unable to maintain altitude. We entered heavy rain and experienced moderate to occasionally severe turbulence. A sudden increase in airspeed was noted and the plane began to climb uncontrollably even though the appropriate pitch and power changes were being made to correct the climb. ATC asked us why we climbed to 4000 ft, and I responded that we were in a cell. ATC directed us to maintain 3000 ft, and I informed the controller that we were unable to control the aircraft and requested an immediate turn. We were given a turn off course and requested another 90 degree turn to exit the WX. We were eventually vectored to the west side of the line of WX and were able to successfully shoot another approach to runway 2L. ATC did not inform us of any traffic conflict and none was noted on the TCASII. Contributing factors: although we had onboard radar we were unaware of the severity of the line of WX encroaching on the final approach course. It appeared to be a very narrow band, but the scale of the radar display probably should have been on a lower setting to better depict the cell and its position relative to the ILS final approach course (the display may have been set on 25 mi instead of 12.5). Also, ATC gave no indication of any convective activity along the final approach course.

Original NASA ASRS Text

Title: C550 ON ILS RWY 2L APCH TO DPA IS UNABLE TO MAINTAIN ALT DURING ILS ATTEMPT DUE TO WX.

Narrative: OUR CITATION JET WAS BEING VECTORED FOR THE ILS RWY 2L AT DPA ARPT BY CHICAGO APCH. AFTER RECEIVING A CLRNC TO SHOOT THE APCH, WE ENCOUNTERED SEVERE CONVECTIVE ACTIVITY OUTSIDE THE FAF AND WERE UNABLE TO MAINTAIN ALT. WE ENTERED HVY RAIN AND EXPERIENCED MODERATE TO OCCASIONALLY SEVERE TURB. A SUDDEN INCREASE IN AIRSPD WAS NOTED AND THE PLANE BEGAN TO CLB UNCONTROLLABLY EVEN THOUGH THE APPROPRIATE PITCH AND PWR CHANGES WERE BEING MADE TO CORRECT THE CLB. ATC ASKED US WHY WE CLBED TO 4000 FT, AND I RESPONDED THAT WE WERE IN A CELL. ATC DIRECTED US TO MAINTAIN 3000 FT, AND I INFORMED THE CTLR THAT WE WERE UNABLE TO CTL THE ACFT AND REQUESTED AN IMMEDIATE TURN. WE WERE GIVEN A TURN OFF COURSE AND REQUESTED ANOTHER 90 DEG TURN TO EXIT THE WX. WE WERE EVENTUALLY VECTORED TO THE W SIDE OF THE LINE OF WX AND WERE ABLE TO SUCCESSFULLY SHOOT ANOTHER APCH TO RWY 2L. ATC DID NOT INFORM US OF ANY TFC CONFLICT AND NONE WAS NOTED ON THE TCASII. CONTRIBUTING FACTORS: ALTHOUGH WE HAD ONBOARD RADAR WE WERE UNAWARE OF THE SEVERITY OF THE LINE OF WX ENCROACHING ON THE FINAL APCH COURSE. IT APPEARED TO BE A VERY NARROW BAND, BUT THE SCALE OF THE RADAR DISPLAY PROBABLY SHOULD HAVE BEEN ON A LOWER SETTING TO BETTER DEPICT THE CELL AND ITS POS RELATIVE TO THE ILS FINAL APCH COURSE (THE DISPLAY MAY HAVE BEEN SET ON 25 MI INSTEAD OF 12.5). ALSO, ATC GAVE NO INDICATION OF ANY CONVECTIVE ACTIVITY ALONG THE FINAL APCH COURSE.

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.