ARTCC radar controller climbing a B737 on same route to an altitude below the preceding B747 did not ensure vertical separation between the 2 aircraft. Radar controller was betting that the B747 would outclb the B737 and he didn't. Supervisor controller was working the data position and observed the less than standard separation occur.

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Attributes
ACN	356729
Time
Date	199701
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : rbl
State Reference	CA
Altitude	msl bound lower : 28000 msl bound upper : 28700
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	B747 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 4
ASRS Report	356729
Person 2
Affiliation	government : faa
Function	controller : flight data oversight : supervisor
Qualification	controller : radar
Experience	controller radar : 5 controller supervisory : 1
ASRS Report	356730
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Miss Distance	horizontal : 21000 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

2 aircraft climbing northbound. Aircraft #1 climbing to FL350. Aircraft #2 climbing to FL280. Aircraft #2 out-climbed aircraft #1 and vertical separation was lost. Aircraft #2 should have been laddered up underneath aircraft #1 instead of climbing both to altitude and thinking #1 will out climb #2. Supplemental information from acn 356730: air carrier B747 and air carrier B737 both departed sfo and were in en route climb phase. Right side recognized that horizontal and lateral separation was diminishing, but had vertical. He saw that vertical was 1100 ft and increasing and elected to let it alone. When rate of climb on top aircraft began to decrease, and vertical separation was decreasing, he was unable to take other action to ensure any other type of separation. He bet on rate of climb and did not ensure anything else.

Original NASA ASRS Text

Title: ARTCC RADAR CTLR CLBING A B737 ON SAME RTE TO AN ALT BELOW THE PRECEDING B747 DID NOT ENSURE VERT SEPARATION BTWN THE 2 ACFT. RADAR CTLR WAS BETTING THAT THE B747 WOULD OUTCLB THE B737 AND HE DIDN'T. SUPVR CTLR WAS WORKING THE DATA POS AND OBSERVED THE LTSS OCCUR.

Narrative: 2 ACFT CLBING NBOUND. ACFT #1 CLBING TO FL350. ACFT #2 CLBING TO FL280. ACFT #2 OUT-CLBED ACFT #1 AND VERT SEPARATION WAS LOST. ACFT #2 SHOULD HAVE BEEN LADDERED UP UNDERNEATH ACFT #1 INSTEAD OF CLBING BOTH TO ALT AND THINKING #1 WILL OUT CLB #2. SUPPLEMENTAL INFO FROM ACN 356730: ACR B747 AND ACR B737 BOTH DEPARTED SFO AND WERE IN ENRTE CLB PHASE. R SIDE RECOGNIZED THAT HORIZ AND LATERAL SEPARATION WAS DIMINISHING, BUT HAD VERT. HE SAW THAT VERT WAS 1100 FT AND INCREASING AND ELECTED TO LET IT ALONE. WHEN RATE OF CLB ON TOP ACFT BEGAN TO DECREASE, AND VERT SEPARATION WAS DECREASING, HE WAS UNABLE TO TAKE OTHER ACTION TO ENSURE ANY OTHER TYPE OF SEPARATION. HE BET ON RATE OF CLB AND DID NOT ENSURE ANYTHING ELSE.

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.