Date: 201406
Local time of day: 0001-0600
Location: LAX.Airport, CA
Light: Dawn
Aircraft: Medium Transport; High Wing; 2 Turboprop Eng
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Tower LAX
Second aircraft: Medium Large Transport
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Human factors: Confusion; Communication Breakdown; Situational Awareness
Second reporter function: Pilot Not Flying; Captain
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Provided Assistance
Contributing factors: Procedure; Environment - Non Weather Related
Primary problem: Procedure

Narrative: After landing on Runway 24R; Los Angeles Tower instructed us to hold short of 24L on Taxiway ZULU behind Aircraft Y and keep it tight. I advised Tower that I didn't think there was enough room for both of us and that our tail might not be completely clear of the 24R hold bar. Tower explained that it was designed to accommodate two aircraft of our size and we would be clear. We got as close as we safely could behind Aircraft Y; but our tail was still hanging well over the hold bar. The Captain told Tower that we were as close as we could get and Tower acknowledged. As we were holding; an Air Carrier landed on 24R. From my perspective in the flight deck; it appeared that the last quarter of our aircraft (about 26 feet) was not clear of the 24R hold bar.The distance available on Taxiway ZULU between 24L and 24R may be sufficient for Aircraft X and Aircraft Y on paper; but it did not appear to be enough room during this event. I could not verify that the Aircraft Y was all the way up to the hold line ahead of us from our perspective; but that could have been a contributing factor.


Second narrative: After landing on the right parallel runway; ATC instructed us to exit the runway and hold short of the L parallel runway. Aircraft Y was already holding short. I commented to my First Officer (FO) how it looked like we might not be fully clear of the right runway. Before I could ask my FO to query ATC; we were instructed to 'Exit the runway without delay.' We complied and joined the high speed turnoff. I taxied up to what I felt is a safe distance behind Aircraft Y; as I was concerned with close proximity to the tail mount engines of the jet in front of us. This gave us approximately 15-20 feet from our nose to Aircraft Y's tail. After I set the park brake; my FO and I evaluated how much of our aircraft had cleared the hold short line behind us. We observed our main wings directly over the hold line. This meant the aft 1/2 of our aircraft (approximately 55 feet) was on the active runway side of the R runway. We immediately advised ATC who responded with 'I show you are clear of the runway.' We repeated that our aft half of our aircraft was not clear of the runway behind us. ATC responded 'that taxiway provides adequate room for your aircraft and Aircraft Y in front of you; you are clear.' A 737 landed on the right runway and exited on the reverse exit. I have two problems here. First is that we were not clear of the runway. Had it been a larger aircraft that rolled longer; there was a great possibility of a collision. Second is that the Tower said we were clear of the runway when in fact we were not. When we parked at the gate I phoned the Tower Manager and expressed my concerns and was told that we were clear and there was no conflict potential. I was told the Local Controller used binoculars to verify we were clear of the runway. I believe the cause of this event was ATC believing that our aircraft was clear based on what their training informs them of how many aircraft can occupy the non-runway area between the parallel runways rather than actual observation of where our aircraft was positioned. Being told by the ATC Tower Manager that the Local Controller used binoculars to verify we were clear when from the flight deck my FO and I verified half of our aircraft was indeed not clear makes me question the controller's assessment that our aircraft was clear. Perhaps it's a miscommunication in how ATC considers an aircraft clear. I do know that if the front half of my aircraft crosses a hold line of an active runway; I am considered on that runway. This is where I need clarification.


Synopsis: Pilot and co-pilot report of holding behind an aircraft in which they did not feel was enough rough for aircraft to land behind them on parallel runway they were holding short of.