Air carrier widebody transport aircraft near midair collision with a WX balloon-radiosonde.

Attributes
ACN	215626
Time
Date	199207
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ekr
State Reference	CO
Altitude	msl bound lower : 37000 msl bound upper : 37000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv tower : oak
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute airway : zdv
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 17000 flight time type : 600
ASRS Report	215626
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : atp pilot : commercial
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted none taken : insufficient time
Consequence	Other
Miss Distance	horizontal : 0 vertical : 50
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

Zsl said he had our radar position approximately 58 mi from ekr at time of incident. Experienced near miss with a radio-sonde WX balloon at FL370 approximately 60D. Ekr. Cluster of 4 white balloons with radio-sonde package below passed not more than 50 ft. Directly above cockpit. Close enough we thought there was a change it could have struck vertical stabilizer. No time for evasive maneuver. First officer an ex- meteorologist and positive idented the package stating he used to launch them 3 a day. This balloon and it's package was so dead center head on that had we been a couple mins sooner I think we could have lost an airplane with 299 sob, because it would've come straight through the windscreen. Why are there no transponders on such packages so ATC can track them at altitude?

Original NASA ASRS Text

Title: ACR WDB ACFT NMAC WITH A WX BALLOON-RADIOSONDE.

Narrative: ZSL SAID HE HAD OUR RADAR POS APPROX 58 MI FROM EKR AT TIME OF INCIDENT. EXPERIENCED NEAR MISS WITH A RADIO-SONDE WX BALLOON AT FL370 APPROX 60D. EKR. CLUSTER OF 4 WHITE BALLOONS WITH RADIO-SONDE PACKAGE BELOW PASSED NOT MORE THAN 50 FT. DIRECTLY ABOVE COCKPIT. CLOSE ENOUGH WE THOUGHT THERE WAS A CHANGE IT COULD HAVE STRUCK VERT STABILIZER. NO TIME FOR EVASIVE MANEUVER. FO AN EX- METEOROLOGIST AND POSITIVE IDENTED THE PACKAGE STATING HE USED TO LAUNCH THEM 3 A DAY. THIS BALLOON AND IT'S PACKAGE WAS SO DEAD CTR HEAD ON THAT HAD WE BEEN A COUPLE MINS SOONER I THINK WE COULD HAVE LOST AN AIRPLANE WITH 299 SOB, BECAUSE IT WOULD'VE COME STRAIGHT THROUGH THE WINDSCREEN. WHY ARE THERE NO TRANSPONDERS ON SUCH PACKAGES SO ATC CAN TRACK THEM AT ALT?

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.