<< >> NASA ASRS Report 526434, October 2001

A B737-700 flight crew is involved in some maneuvering which was required from ATC to provide separation from military aircraft at FL330 and FL350 near rbl, ca.

Attributes
ACN	526434
Time
Date	200110
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : rbl.airport
State Reference	CA
Altitude	msl bound lower : 31000 msl bound upper : 33400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa.artcc artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zoa.artcc
Operator	other
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 130 flight time total : 17000 flight time type : 3000
ASRS Report	526434
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	atc equipment other atc equipment : 4
Resolutory Action	controller : separated traffic controller : issued new clearance controller : issued advisory
Supplementary
Problem Areas	Airspace Structure Flight Crew Human Performance ATC Human Performance
Primary Problem	ATC Human Performance

Narrative:

Clearance issued by ZOA to climb to FL270. Prior to reaching FL270, a climb to FL350 was issued and read back, and acknowledged by both pilots. Passing through approximately FL334, ZOA advised us that clearance had been amended to FL310, which I did not hear, nor was it acknowledged. A right turn to a 030 degree heading was issued by ZOA and to expedite climb to FL350. Shortly thereafter, and prior to reaching FL350, controller issued a climb and expedite to FL390, followed by a clearance to proceed direct to btg VOR on course. No abrupt maneuvers were required or immediate clrncs issued. I believe frequency congestion was a factor, as the controller was working more than 1 frequency or a hfr frequency, as mostly only 1/2 of the conversation was being heard.

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Original NASA ASRS Text

Title: A B737-700 FLC IS INVOLVED IN SOME MANEUVERING WHICH WAS REQUIRED FROM ATC TO PROVIDE SEPARATION FROM MIL ACFT AT FL330 AND FL350 NEAR RBL, CA.

Narrative: CLRNC ISSUED BY ZOA TO CLB TO FL270. PRIOR TO REACHING FL270, A CLB TO FL350 WAS ISSUED AND READ BACK, AND ACKNOWLEDGED BY BOTH PLTS. PASSING THROUGH APPROX FL334, ZOA ADVISED US THAT CLRNC HAD BEEN AMENDED TO FL310, WHICH I DID NOT HEAR, NOR WAS IT ACKNOWLEDGED. A R TURN TO A 030 DEG HDG WAS ISSUED BY ZOA AND TO EXPEDITE CLB TO FL350. SHORTLY THEREAFTER, AND PRIOR TO REACHING FL350, CTLR ISSUED A CLB AND EXPEDITE TO FL390, FOLLOWED BY A CLRNC TO PROCEED DIRECT TO BTG VOR ON COURSE. NO ABRUPT MANEUVERS WERE REQUIRED OR IMMEDIATE CLRNCS ISSUED. I BELIEVE FREQ CONGESTION WAS A FACTOR, AS THE CTLR WAS WORKING MORE THAN 1 FREQ OR A HFR FREQ, AS MOSTLY ONLY 1/2 OF THE CONVERSATION WAS BEING HEARD.

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.