A P180 captain and first officer ehsi's and eadi's became unusable in flight after having departed i...

Attributes
ACN	815533
Time
Date	200811
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl bound lower : 5000 msl bound upper : 8000
Environment
Flight Conditions	IMC
Weather Elements	Rain
Light	Night
Aircraft 1
Controlling Facilities	tracon : zzz.tracon
Operator	general aviation : corporate
Make Model Name	P180
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	descent : intermediate altitude ground : maintenance
Flight Plan	IFR
Person 1
Affiliation	company other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 50 flight time total : 9200 flight time type : 300
ASRS Report	815533
Events
Anomaly	aircraft equipment problem : critical inflight encounter : weather maintenance problem : improper maintenance
Independent Detector	aircraft equipment other aircraft equipment : flight instruments
Resolutory Action	flight crew : exited adverse environment
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Description of event: after flying through rain showers out of ZZZ and again on descent into ZZZ1; we noticed the copilot's ehsi display acting strange. Then the mfd navigation data became unreadable even though the radar display was still working. Then I lost both electronic displays on the pilot's side with both indicating dpu failure. This was during descent to 5000 ft. After all this; I had my copilot ask ATC for a heading to keep us VMC since we had just broke out of the clouds. This was approved and since we stayed in VMC I told ATC I did not need to declare an emergency; when they asked; as long as I stayed in VMC. I did tell them that I was having instrumentation problems. We were then cleared direct to the field. After reporting field in sight we were cleared for the visual approach into ZZZ1. When turning base for runway 18; we canceled IFR. While we were in VMC; I tried the drive xfer switch. What I got on the eadi was a picture that looked like 'double vision.' this included the composite mode for eadi and the pilot's side ehsi. Since we were in VMC; I switched everything back to normal switch positions and landed. When I called my chief pilot he told me this was a recurring problem in this airplane that was caused by moisture getting in the avionics bay in the nose of the airplane. A mechanic came out the next day; removed the nose radome; and found exactly that. After removing the dpu; then drying out the avionics rack; cleaning contacts; everything was put back together. An EFIS check was run and it checked out ok. After consulting with maintenance control; the airplane was signed off by the mechanic as ok to fly. Callback conversation with reporter revealed the following information: the reporter stated that his fractional carrier has a large P180 fleet and this particular aircraft is currently the only one that he is aware of with this radome moisture problem. This particular aircraft has a history of radome seal leakage allowing moisture onto the avionics and he believes a service bulletin has been issued addressing the radome seal.

Original NASA ASRS Text

Title: A P180 CAPTAIN AND FIRST OFFICER EHSI'S AND EADI'S BECAME UNUSABLE IN FLIGHT AFTER HAVING DEPARTED IN RAIN SHOWERS. MAINTENANCE DISCOVERED MOISTURE IN THE RADOME AVIONICS BAY.

Narrative: DESCRIPTION OF EVENT: AFTER FLYING THROUGH RAIN SHOWERS OUT OF ZZZ AND AGAIN ON DSCNT INTO ZZZ1; WE NOTICED THE COPLT'S EHSI DISPLAY ACTING STRANGE. THEN THE MFD NAV DATA BECAME UNREADABLE EVEN THOUGH THE RADAR DISPLAY WAS STILL WORKING. THEN I LOST BOTH ELECTRONIC DISPLAYS ON THE PLT'S SIDE WITH BOTH INDICATING DPU FAILURE. THIS WAS DURING DSCNT TO 5000 FT. AFTER ALL THIS; I HAD MY COPLT ASK ATC FOR A HDG TO KEEP US VMC SINCE WE HAD JUST BROKE OUT OF THE CLOUDS. THIS WAS APPROVED AND SINCE WE STAYED IN VMC I TOLD ATC I DID NOT NEED TO DECLARE AN EMER; WHEN THEY ASKED; AS LONG AS I STAYED IN VMC. I DID TELL THEM THAT I WAS HAVING INSTRUMENTATION PROBS. WE WERE THEN CLRED DIRECT TO THE FIELD. AFTER RPTING FIELD IN SIGHT WE WERE CLRED FOR THE VISUAL APCH INTO ZZZ1. WHEN TURNING BASE FOR RWY 18; WE CANCELED IFR. WHILE WE WERE IN VMC; I TRIED THE DRIVE XFER SWITCH. WHAT I GOT ON THE EADI WAS A PICTURE THAT LOOKED LIKE 'DOUBLE VISION.' THIS INCLUDED THE COMPOSITE MODE FOR EADI AND THE PLT'S SIDE EHSI. SINCE WE WERE IN VMC; I SWITCHED EVERYTHING BACK TO NORMAL SWITCH POSITIONS AND LANDED. WHEN I CALLED MY CHIEF PLT HE TOLD ME THIS WAS A RECURRING PROB IN THIS AIRPLANE THAT WAS CAUSED BY MOISTURE GETTING IN THE AVIONICS BAY IN THE NOSE OF THE AIRPLANE. A MECH CAME OUT THE NEXT DAY; REMOVED THE NOSE RADOME; AND FOUND EXACTLY THAT. AFTER REMOVING THE DPU; THEN DRYING OUT THE AVIONICS RACK; CLEANING CONTACTS; EVERYTHING WAS PUT BACK TOGETHER. AN EFIS CHK WAS RUN AND IT CHKED OUT OK. AFTER CONSULTING WITH MAINT CTL; THE AIRPLANE WAS SIGNED OFF BY THE MECH AS OK TO FLY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER STATED THAT HIS FRACTIONAL CARRIER HAS A LARGE P180 FLEET AND THIS PARTICULAR AIRCRAFT IS CURRENTLY THE ONLY ONE THAT HE IS AWARE OF WITH THIS RADOME MOISTURE PROBLEM. THIS PARTICULAR AIRCRAFT HAS A HISTORY OF RADOME SEAL LEAKAGE ALLOWING MOISTURE ONTO THE AVIONICS AND HE BELIEVES A SERVICE BULLETIN HAS BEEN ISSUED ADDRESSING THE RADOME SEAL.

Data retrieved from NASA's ASRS site as of May 2009 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.

A P180 captain and first officer ehsi's and eadi's became unusable in flight after having departed in rain showers. Maintenance discovered moisture in the radome avionics bay.