BAE3201 in light to moderate icing with marginal deice capability diverts to iad.

Attributes
ACN	453240
Time
Date	199910
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : iad.airport
State Reference	VA
Altitude	msl single value : 13000
Environment
Flight Conditions	IMC
Weather Elements	Ice
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc.artcc
Operator	common carrier : air carrier
Make Model Name	Jetstream 32
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Route In Use	enroute airway : v44.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Experience	flight time last 90 days : 200 flight time total : 1900 flight time type : 600
ASRS Report	453240
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter other other anomaly other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist controller : issued new clearance flight crew : declared emergency flight crew : diverted to another airport flight crew : exited adverse environment flight crew : landed as precaution
Consequence	other
Supplementary
Problem Areas	Weather Environmental Factor Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

Flight departed gate at iad at XA21 local, was delayed on taxiway for 1 hour in light rain before takeoff. Deice boots tested properly on ground before departure. Normal takeoff and climb out, ceiling 9500 ft overcast, anti-ice equipment on. We flew in IMC for 15 mins with no icing, then light rime. Upon reaching 13000 ft, approximately 20 mi east of balance and with 1/2 inch, the captain tried to blow the deice boots to no avail. We could see the moon through a little mist so we opted to try to climb out of the IMC to 15000 ft. The same conditions existed there, still misty, still light icing. Meanwhile, the captain was on the radio with dispatch and maintenance, and continually tried to get the boots to operate. We could still see the moon so after 1 min at 15000 ft, we asked for 17000 ft. The icing then got heavier (moderate mixed) and we had probably accumulated 1 1/2 or 2 inches by then. After 1 min at 17000 ft, having lost 24 KTS airspeed and with PIREPS of light to moderate ice ahead, we asked for a rapid descent. The controller gave us 11000 ft. Passing 12000 ft, I asked for 9000 ft (captain off #1 communication) because I knew that 9000 ft would likely get us out of visible moisture and my workload was too heavy to spend much time looking out the window. The controller wanted me to stop at 11000 ft 'for traffic.' by now, due to the descent, we likely had 3 1/2 - 4 inches of rime on the leading edge with clear glazed over it and all the way to the back of the boots on the top of the airfoil. The controls were heavy and mushy and I figured that the controller didn't understand the urgency of the situation, so I asked for an 'emergency descent' to 9000 ft. The aircraft began to vibrate (propeller imbal). We diverted back to dulles. At 8000 ft with balance approach in VMC, the ice began to chunk off the plane. Before turning us over to approach, the center controller verified that we had not 'declared' an emergency, but that we had just needed a priority descent. The deice boots operated intermittently on the approach (VMC) and again intermittently on the ground. In IMC, we did not get a single positive operating indication in the cockpit. I feel that we performed well as a crew in handling the situation. We had flown together in the past. I think that as a captain, I may test the boots in the air just before entering IMC as well as on the ground. Ultimately, some of our decisions may have been based on the fact that we knew we could get below the freezing level.

Original NASA ASRS Text

Title: BAE3201 IN LIGHT TO MODERATE ICING WITH MARGINAL DEICE CAPABILITY DIVERTS TO IAD.

Narrative: FLT DEPARTED GATE AT IAD AT XA21 LCL, WAS DELAYED ON TXWY FOR 1 HR IN LIGHT RAIN BEFORE TKOF. DEICE BOOTS TESTED PROPERLY ON GND BEFORE DEP. NORMAL TKOF AND CLBOUT, CEILING 9500 FT OVCST, ANTI-ICE EQUIP ON. WE FLEW IN IMC FOR 15 MINS WITH NO ICING, THEN LIGHT RIME. UPON REACHING 13000 FT, APPROX 20 MI E OF BAL AND WITH 1/2 INCH, THE CAPT TRIED TO BLOW THE DEICE BOOTS TO NO AVAIL. WE COULD SEE THE MOON THROUGH A LITTLE MIST SO WE OPTED TO TRY TO CLB OUT OF THE IMC TO 15000 FT. THE SAME CONDITIONS EXISTED THERE, STILL MISTY, STILL LIGHT ICING. MEANWHILE, THE CAPT WAS ON THE RADIO WITH DISPATCH AND MAINT, AND CONTINUALLY TRIED TO GET THE BOOTS TO OPERATE. WE COULD STILL SEE THE MOON SO AFTER 1 MIN AT 15000 FT, WE ASKED FOR 17000 FT. THE ICING THEN GOT HEAVIER (MODERATE MIXED) AND WE HAD PROBABLY ACCUMULATED 1 1/2 OR 2 INCHES BY THEN. AFTER 1 MIN AT 17000 FT, HAVING LOST 24 KTS AIRSPD AND WITH PIREPS OF LIGHT TO MODERATE ICE AHEAD, WE ASKED FOR A RAPID DSCNT. THE CTLR GAVE US 11000 FT. PASSING 12000 FT, I ASKED FOR 9000 FT (CAPT OFF #1 COM) BECAUSE I KNEW THAT 9000 FT WOULD LIKELY GET US OUT OF VISIBLE MOISTURE AND MY WORKLOAD WAS TOO HVY TO SPEND MUCH TIME LOOKING OUT THE WINDOW. THE CTLR WANTED ME TO STOP AT 11000 FT 'FOR TFC.' BY NOW, DUE TO THE DSCNT, WE LIKELY HAD 3 1/2 - 4 INCHES OF RIME ON THE LEADING EDGE WITH CLR GLAZED OVER IT AND ALL THE WAY TO THE BACK OF THE BOOTS ON THE TOP OF THE AIRFOIL. THE CTLS WERE HVY AND MUSHY AND I FIGURED THAT THE CTLR DIDN'T UNDERSTAND THE URGENCY OF THE SIT, SO I ASKED FOR AN 'EMER DSCNT' TO 9000 FT. THE ACFT BEGAN TO VIBRATE (PROP IMBAL). WE DIVERTED BACK TO DULLES. AT 8000 FT WITH BAL APCH IN VMC, THE ICE BEGAN TO CHUNK OFF THE PLANE. BEFORE TURNING US OVER TO APCH, THE CTR CTLR VERIFIED THAT WE HAD NOT 'DECLARED' AN EMER, BUT THAT WE HAD JUST NEEDED A PRIORITY DSCNT. THE DEICE BOOTS OPERATED INTERMITTENTLY ON THE APCH (VMC) AND AGAIN INTERMITTENTLY ON THE GND. IN IMC, WE DID NOT GET A SINGLE POSITIVE OPERATING INDICATION IN THE COCKPIT. I FEEL THAT WE PERFORMED WELL AS A CREW IN HANDLING THE SIT. WE HAD FLOWN TOGETHER IN THE PAST. I THINK THAT AS A CAPT, I MAY TEST THE BOOTS IN THE AIR JUST BEFORE ENTERING IMC AS WELL AS ON THE GND. ULTIMATELY, SOME OF OUR DECISIONS MAY HAVE BEEN BASED ON THE FACT THAT WE KNEW WE COULD GET BELOW THE FREEZING LEVEL.

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.