Date: 201502
Local time of day: 0601-1200
Location: SCT.TRACON, CA
Flight conditions: VMC
Weather elements / visibility: Haze / Smoke; 6
Light: Daylight
Aircraft: DA50 Super Star
Operator: Corporate
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B SCT
Reporter organization: Corporate
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Commercial; Flight Crew Instrument
Human factors: Communication Breakdown; Confusion; Situational Awareness
Second reporter function: Captain; Pilot Flying
Anomaly: ATC Issue All Types; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural FAR
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: During the approach we were above 10;000 feet and given an ATC clearance to maintain 300 KIAS or greater. A few minutes later; while still above 10;000 feet we were given another clearance to maintain 250 KIAS or greater. As we transitioned through 10;000 feet the captain interpreted the clearance from ATC as to maintain best forward speed. Once below 10;000 feet; we were descending through 9;000 feet and still flying 325 KIAS when the controller asked what our IAS was. Upon read back of 325 KIAS; the controller asked if there was any reason we were maintaining that speed. At that time the captain keyed the mic to explain the clearance and how he interpreted it. The controller responded with a speed restriction to maintain of 200 KIAS. Before handing us off to the next controller; he explained only the FAA administrator has the authority to assign an airspeed greater than 250 KIAS below 10;000 feet.After talking about what happened the captain and I both agreed that the last airspeed clearance verbiage could be cleaned up to eliminate the potential confusion for crews in the future. Another example of a poor choice of verbiage in a clearance given by LAX ATC on our departure from LAX was to maintain 280 or greater in the climb. We were climbing through 8;000 feet when ATC gave us this clearance. Overall I believe the captain should have known better; I as the co-pilot needed to speak up more and ATC's clearances need to be more specific when giving a clearance that breaks an FAR if pilots comply with it.


Second narrative: ATC instructed me to maintain 250 knots indicated airspeed or greater in the descent and to comply with the vertical guidance as specified on the RIIVR2 STAR and also at the same time cleared me for the runway 25L ILS approach into Los Angeles International Airport.Once on the ground I looked up the FAR 91 regulation that pertains to aircraft speeds and found that the administrator and ATC are two different entities; it was my understanding that ATC was the FAA and that I should comply with the ATC clearance as given.I am aware of this now and will remain mindful of such clearances in the future.I hope that the submission of this report will be helpful for other pilots and air traffic controllers regarding communication and understanding of certain vernacular and regarding Federal Aviation Regulations.


Synopsis: A DA-50 Captain descending into LAX on the RIIVR STAR misinterpreted ATC clearances for higher than charted airspeeds and maintained an IAS well above 250K below 10;000 feet. The First Officer; expressing timidity; failed to share his concerns and it fell to ATC to intervene. The Captain cited his misunderstanding of permitted ATC discretion with respect to maximum airspeeds below 10;000 feet.