<< >> NASA ASRS Report 1162098, April 2014

Reporter states difficulty with pilot in understanding the difference between cleared and descend via phraseology which led to an operational error.

Attributes
ACN	1162098
Time
Date	201404
Local Time Of Day	1801-2400
Place
Locale Reference	BOS.Airport
State Reference	MA
Environment
Light	Night
Aircraft 1
Make Model Name	Light Transport Low Wing 2 Turboprop Eng
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Aircraft 2
Make Model Name	Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR KRANN3
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 14
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance

Narrative:

I issued a 'cleared KRANN3 arrival runway 27 transition' to aircraft Y and the pilot read it back correctly. I exchanged traffic information with both aircraft. Aircraft Y began his descent. I caught the descent when aircraft Y was leaving 10;800; and instructed the pilot to maintain 11;000. I instructed aircraft X and aircraft Y to maintain visual separation from each other. Both pilots read it back timely and correctly. I issued a 'brasher' warning to aircraft Y and asked what happened? His response was that he received a 'descend via' clearance.in reference to all of the RNAV changes in recent months/years; I feel that all of this change is confusing to flight crews and controllers. I specifically told the crew that there was crossing traffic and issued traffic; and the crew still descended!my recommendation is to not use the word 'cleared' in a clearance associated with RNAV procedures. If we are going to use this phraseology; I recommend re-iterating to the pilot the altitude to maintain. 'Cleared KRANN3 runway 27 transition; maintain 11;000'. We shouldn't have to; but this is an added measure of safety until we find a better way of doing this.

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Original NASA ASRS Text

Title: Reporter states difficulty with pilot in understanding the difference between cleared and descend via phraseology which led to an operational error.

Narrative: I issued a 'Cleared KRANN3 arrival Runway 27 Transition' to Aircraft Y and the pilot read it back correctly. I exchanged traffic information with both aircraft. Aircraft Y began his descent. I caught the descent when Aircraft Y was leaving 10;800; and instructed the pilot to maintain 11;000. I instructed Aircraft X and Aircraft Y to maintain visual separation from each other. Both pilots read it back timely and correctly. I issued a 'Brasher' warning to Aircraft Y and asked what happened? His response was that he received a 'descend Via' clearance.In reference to all of the RNAV changes in recent months/years; I feel that all of this change is confusing to flight crews and controllers. I specifically told the crew that there was crossing traffic and issued traffic; and the crew still descended!My recommendation is to not use the word 'cleared' in a clearance associated with RNAV procedures. If we are going to use this phraseology; I recommend re-iterating to the pilot the altitude to maintain. 'Cleared KRANN3 Runway 27 Transition; maintain 11;000'. We shouldn't have to; but this is an added measure of safety until we find a better way of doing this.

Data retrieved from NASA's ASRS site 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.