ZAB controller described loss of separation event reportedly caused by a missed incorrect altitude a...

Narrative:

Aircraft X departed elp on course; northwest bound and checked on frequency climbing from FL192 to FL360. This resulted in a loss of separation with aircraft Y westbound at FL200. Aircraft X should have been climbing to 17;000 per the LOA. Aircraft were on diverging courses and never seemed to be aware of each other. Upon questioning aircraft X about his clearance from elp approach; he stated that he had been issued and 'unrestricted climb to FL360 by clearance delivery'. It was later confirmed that aircraft X was issued climb to 17;000 with 'expect FL360 10 minutes after departure'; but read back something like; 'roger; climbing to FL360'. The read back was not caught by anyone at elp. The departure clearance phraseology from the 7110.65 that states to use 'expect (altitude) 10 minutes after departure' can be misleading and misheard. In my opinion; the expectation of further climb is implied if a higher altitude is requested in the flight plan and the phraseology could be omitted.

Original NASA ASRS Text

Title: ZAB Controller described loss of separation event reportedly caused by a missed incorrect altitude assignment read back; reporter claiming required 'expect altitude etc. etc.' can be confused and easily misunderstood.

Narrative: Aircraft X departed ELP on course; northwest bound and checked on frequency climbing from FL192 to FL360. This resulted in a loss of separation with Aircraft Y westbound at FL200. Aircraft X should have been climbing to 17;000 per the LOA. Aircraft were on diverging courses and never seemed to be aware of each other. Upon questioning Aircraft X about his clearance from ELP Approach; he stated that he had been issued and 'unrestricted climb to FL360 by clearance delivery'. It was later confirmed that Aircraft X was issued climb to 17;000 with 'expect FL360 10 minutes after departure'; but read back something like; 'roger; climbing to FL360'. The read back was not caught by anyone at ELP. The departure clearance phraseology from the 7110.65 that states to use 'expect (altitude) 10 minutes after departure' can be misleading and misheard. In my opinion; the expectation of further climb is implied if a higher altitude is requested in the flight plan and the phraseology could be omitted.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	876272
Time
Date	201003
Local Time Of Day	1801-2400
Place
Locale Reference	ZAB.ARTCC
State Reference	NM
Aircraft 1
Make Model Name	Learjet 40
Flight Phase	Climb
Flight Plan	IFR
Aircraft 2
Make Model Name	PA-31T Cheyenne I
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Altitude Overshoot Deviation - Procedural Clearance

ZAB controller described loss of separation event reportedly caused by a missed incorrect altitude assignment read back; reporter claiming required 'expect altitude etc. Etc.' can be confused and easily misunderstood.