Narrative:

We departed lan at approximately XA30 for mnn in learjet 45. We were to drop off passenger in marion and then continue on to cleveland, oh. Approximately 15 mins into the flight and climbing through FL180, the aircraft suffered a failure of the left windshield. Later inspection revealed the outer pane had cracked into hundreds of pieces. Both the first officer and I felt an immediate descent was necessary along with slowing the aircraft and reducing differential pressure thus relieving any additional stress on the windshield. There was also an electrical short in the windshield which was causing arcing and sparks in the lower portion. I switched off electric windshield heat to the left windshield which eliminated the arcing. Because we were not sure of the structural integrity of the windshield and the need for immediate descent, I felt it was prudent to declare an emergency. We also wanted the controller to be aware of our situation in case we needed further assistance. We were approximately 130 mi west of cleveland, and since we knew the cleveland WX was good with no significant NOTAMS, we decided to initially request clearance to the cleveland airport. The controller descended us and cleared us directly to cleveland. After descending, slowing, and reducing differential pressure, the first officer and I had an opportunity to discuss the situation. The windshield was holding well and no additional cracks were forming. We were at a reasonable altitude (10000 ft) and had reduced differential to about 4 psi. The first officer recalled that the inner pane of the windshield is a structural part of the aircraft and is designed fail safe. Running my fingers across the windshield revealed that the cracking was indeed in the outer pane and not part of the inner pane. Because of the precautions we had taken and the inspection of the windshield, we both felt that the emergency no longer existed and we advised detroit approach that we were no longer an emergency aircraft but did wish to continue on to cleveland. We also advised them that no special handling was required. We arrived in the cleveland terminal area and were vectored along with other aircraft for a visual approach to runway 23L. The landing was uneventful. The lear 45 is a new aircraft. I have heard stories of other lear 45's suffering windshield failures. Our failure is the 5TH I know of -- there may be more. It seems to me that there must be a flaw in the design, manufacturing, or installation process of this windshield. Callback conversation with reporter revealed the following information: this concerned reporter states that between he and the air carrier maintenance, they are aware of over a dozen window failures on these new lear 45 series aircraft. One of these failures was a double window failure that occurred in africa. Lear evidently changed window vendors on this new series and the maintenance department has complained about the poor quality and need to do much more work than in the past in trying to make the window fit. Lear is evidently also aware of this problem and claims to be looking for a new window vendor. The reporter states that there is no specific SOP for a failed window at this time. He also states that he will submit a request and recommendation that such a SOP be incorporated in the QRH to aid those flcs that will obviously need it in the near future.

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Original NASA ASRS Text

Title: LEAR 45 EXPERIENCES L WINDSHIELD FAILURE ON CLBOUT FROM LAN.

Narrative: WE DEPARTED LAN AT APPROX XA30 FOR MNN IN LEARJET 45. WE WERE TO DROP OFF PAX IN MARION AND THEN CONTINUE ON TO CLEVELAND, OH. APPROX 15 MINS INTO THE FLT AND CLBING THROUGH FL180, THE ACFT SUFFERED A FAILURE OF THE L WINDSHIELD. LATER INSPECTION REVEALED THE OUTER PANE HAD CRACKED INTO HUNDREDS OF PIECES. BOTH THE FO AND I FELT AN IMMEDIATE DSCNT WAS NECESSARY ALONG WITH SLOWING THE ACFT AND REDUCING DIFFERENTIAL PRESSURE THUS RELIEVING ANY ADDITIONAL STRESS ON THE WINDSHIELD. THERE WAS ALSO AN ELECTRICAL SHORT IN THE WINDSHIELD WHICH WAS CAUSING ARCING AND SPARKS IN THE LOWER PORTION. I SWITCHED OFF ELECTRIC WINDSHIELD HEAT TO THE L WINDSHIELD WHICH ELIMINATED THE ARCING. BECAUSE WE WERE NOT SURE OF THE STRUCTURAL INTEGRITY OF THE WINDSHIELD AND THE NEED FOR IMMEDIATE DSCNT, I FELT IT WAS PRUDENT TO DECLARE AN EMER. WE ALSO WANTED THE CTLR TO BE AWARE OF OUR SIT IN CASE WE NEEDED FURTHER ASSISTANCE. WE WERE APPROX 130 MI W OF CLEVELAND, AND SINCE WE KNEW THE CLEVELAND WX WAS GOOD WITH NO SIGNIFICANT NOTAMS, WE DECIDED TO INITIALLY REQUEST CLRNC TO THE CLEVELAND ARPT. THE CTLR DSNDED US AND CLRED US DIRECTLY TO CLEVELAND. AFTER DSNDING, SLOWING, AND REDUCING DIFFERENTIAL PRESSURE, THE FO AND I HAD AN OPPORTUNITY TO DISCUSS THE SIT. THE WINDSHIELD WAS HOLDING WELL AND NO ADDITIONAL CRACKS WERE FORMING. WE WERE AT A REASONABLE ALT (10000 FT) AND HAD REDUCED DIFFERENTIAL TO ABOUT 4 PSI. THE FO RECALLED THAT THE INNER PANE OF THE WINDSHIELD IS A STRUCTURAL PART OF THE ACFT AND IS DESIGNED FAIL SAFE. RUNNING MY FINGERS ACROSS THE WINDSHIELD REVEALED THAT THE CRACKING WAS INDEED IN THE OUTER PANE AND NOT PART OF THE INNER PANE. BECAUSE OF THE PRECAUTIONS WE HAD TAKEN AND THE INSPECTION OF THE WINDSHIELD, WE BOTH FELT THAT THE EMER NO LONGER EXISTED AND WE ADVISED DETROIT APCH THAT WE WERE NO LONGER AN EMER ACFT BUT DID WISH TO CONTINUE ON TO CLEVELAND. WE ALSO ADVISED THEM THAT NO SPECIAL HANDLING WAS REQUIRED. WE ARRIVED IN THE CLEVELAND TERMINAL AREA AND WERE VECTORED ALONG WITH OTHER ACFT FOR A VISUAL APCH TO RWY 23L. THE LNDG WAS UNEVENTFUL. THE LEAR 45 IS A NEW ACFT. I HAVE HEARD STORIES OF OTHER LEAR 45'S SUFFERING WINDSHIELD FAILURES. OUR FAILURE IS THE 5TH I KNOW OF -- THERE MAY BE MORE. IT SEEMS TO ME THAT THERE MUST BE A FLAW IN THE DESIGN, MANUFACTURING, OR INSTALLATION PROCESS OF THIS WINDSHIELD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS CONCERNED RPTR STATES THAT BTWN HE AND THE ACR MAINT, THEY ARE AWARE OF OVER A DOZEN WINDOW FAILURES ON THESE NEW LEAR 45 SERIES ACFT. ONE OF THESE FAILURES WAS A DOUBLE WINDOW FAILURE THAT OCCURRED IN AFRICA. LEAR EVIDENTLY CHANGED WINDOW VENDORS ON THIS NEW SERIES AND THE MAINT DEPT HAS COMPLAINED ABOUT THE POOR QUALITY AND NEED TO DO MUCH MORE WORK THAN IN THE PAST IN TRYING TO MAKE THE WINDOW FIT. LEAR IS EVIDENTLY ALSO AWARE OF THIS PROB AND CLAIMS TO BE LOOKING FOR A NEW WINDOW VENDOR. THE RPTR STATES THAT THERE IS NO SPECIFIC SOP FOR A FAILED WINDOW AT THIS TIME. HE ALSO STATES THAT HE WILL SUBMIT A REQUEST AND RECOMMENDATION THAT SUCH A SOP BE INCORPORATED IN THE QRH TO AID THOSE FLCS THAT WILL OBVIOUSLY NEED IT IN THE NEAR FUTURE.

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.