Air carrier has windshield cracking. Requests lower, center says unable. Declares emergency.

Attributes
ACN	226222
Time
Date	199211
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : bam
State Reference	NV
Altitude	msl bound lower : 24000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zlc tower : lga
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 250 flight time total : 10000 flight time type : 2000
ASRS Report	226222
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency none taken : unable none taken : anomaly accepted other
Consequence	other
Supplementary
Primary Problem	Aircraft

Narrative:

While flying in the vicinity of bam on radar vectors to swr at FL350 we heard a very loud cracking sound and 5 or 6 cracks appeared in the captain's left #1 windshield. We turned off the left side window head. We asked ZLC for FL240 and we were told that FL350 was the lowest available due to MOA's. After more loud noises and cracks we used emergency authority to descend to lower altitude (FL240). At the lower altitude the windshield quit cracking. The cracks appeared to be only in the outer pane and our QRH gave no restrictions for this condition. We made a slower than normal descent at a constant speed. We made an uneventful landing at smf. All ATC personnel were most helpful.

Original NASA ASRS Text

Title: ACR HAS WINDSHIELD CRACKING. REQUESTS LOWER, CTR SAYS UNABLE. DECLARES EMER.

Narrative: WHILE FLYING IN THE VICINITY OF BAM ON RADAR VECTORS TO SWR AT FL350 WE HEARD A VERY LOUD CRACKING SOUND AND 5 OR 6 CRACKS APPEARED IN THE CAPT'S L #1 WINDSHIELD. WE TURNED OFF THE L SIDE WINDOW HEAD. WE ASKED ZLC FOR FL240 AND WE WERE TOLD THAT FL350 WAS THE LOWEST AVAILABLE DUE TO MOA'S. AFTER MORE LOUD NOISES AND CRACKS WE USED EMER AUTHORITY TO DSND TO LOWER ALT (FL240). AT THE LOWER ALT THE WINDSHIELD QUIT CRACKING. THE CRACKS APPEARED TO BE ONLY IN THE OUTER PANE AND OUR QRH GAVE NO RESTRICTIONS FOR THIS CONDITION. WE MADE A SLOWER THAN NORMAL DSCNT AT A CONSTANT SPD. WE MADE AN UNEVENTFUL LNDG AT SMF. ALL ATC PERSONNEL WERE MOST HELPFUL.

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.