Sct controller reports of a loss of separation he attributes to the pilot descending early next to a...

Attributes
ACN	1265923
Time
Date	201505
Local Time Of Day	1201-1800
Place
Locale Reference	SCT.TRACON
State Reference	CA
Environment
Light	Daylight
Aircraft 1
Make Model Name	Medium Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Medium Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Other Instrument Approach
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 26
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Deviation - Track / Heading All Types

Narrative:

I turned aircraft X onto the approach for 25L by saying 'maintain 3;300 until established on the localizer; cleared ILS ry 25L approach.' the readback sounded like 2;300 feet; so I went back and verified 3;300 feet as the altitude. It sounded like that was what he said. Subsequently; I saw aircraft X descending out of 3;100 feet turning onto final behind aircraft Y who was established on the 24R localizer; about 2 miles in front of aircraft X. At this point it looked to me like aircraft X was just turning onto the final; so he had broken the instruction. I switched aircraft X to lax tower because we were on simultaneous approaches. They got about 2 miles and 600 feet in altitude away before aircraft X was established on the localizer.the quality of radios in the la area is atrocious. We quit using 124.9 because it was unreadable out to the east; but all of our radios have very poor quality. 132.37; the replacement radio is just as bad; but we have no other backup. When you compound this with the poor quality of the radios on the crjs and some embraer types; you have a big problem. This is something that is getting worse and needs to be dealt with before something happens that we will regret because we could have prevented it. I have been in the area for almost 30 years and have noticed the quality of the radios eroding. When this is combined with the lower time pilots now flying jets; it is a recipe for disaster.

Original NASA ASRS Text

Title: SCT Controller reports of a loss of separation he attributes to the pilot descending early next to another aircraft and the radios associated to his position. The Controller has noticed a degradation of radio clearness and the experience of upgraded pilots in that area using the radios.

Narrative: I turned Aircraft X onto the approach for 25L by saying 'Maintain 3;300 until established on the localizer; cleared ILS Ry 25L approach.' The readback sounded like 2;300 feet; so I went back and verified 3;300 feet as the altitude. It sounded like that was what he said. Subsequently; I saw Aircraft X descending out of 3;100 feet turning onto final behind Aircraft Y who was established on the 24R localizer; about 2 miles in front of Aircraft X. At this point it looked to me like Aircraft X was just turning onto the final; so he had broken the instruction. I switched Aircraft X to LAX Tower because we were on simultaneous approaches. They got about 2 miles and 600 feet in altitude away before Aircraft X was established on the localizer.The quality of radios in the LA area is atrocious. We quit using 124.9 because it was unreadable out to the east; but all of our radios have very poor quality. 132.37; the replacement radio is just as bad; but we have no other backup. When you compound this with the poor quality of the radios on the CRJs and some Embraer types; you have a big problem. This is something that is getting worse and needs to be dealt with before something happens that we will regret because we could have prevented it. I have been in the area for almost 30 years and have noticed the quality of the radios eroding. When this is combined with the lower time pilots now flying jets; it is a recipe for disaster.

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.

Sct controller reports of a loss of separation he attributes to the pilot descending early next to another aircraft and the radios associated to his position. The controller has noticed a degradation of radio clearness and the experience of upgraded pilots in that area using the radios.