Date: 202104
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Citationjet (C525/C526) - CJ I / II / III / IV
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Second aircraft: Commercial Fixed Wing
Aircraft component: Air/Ground Communication
Component problem: Malfunctioning
Reporter organization: Corporate
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Captain; Pilot Flying
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem
Contributing factors: Procedure; Human Factors; Aircraft
Primary problem: Aircraft

Narrative: We were departing out of ZZZ on runway XXR at [Taxiway] 1. Tower had cleared us to line up and wait. The co-pilot started to move into position as I responded back to the tower. A moment later the tower came back and said for us remain holding short of runway XXR on 1. The co-pilot stopped immediately but we had already crossed the hold short line. I immediately replied back to the tower and stated that we were already across the hold short line and asking for further instruction. The hold short line was still in front of the main landing gear to give an idea of how quickly we stopped and responded to the towers call. The tower then cleared Aircraft Y to land on the same runway. I immediately radioed back again that we were beyond the hold short line and requested instruction. A second [same airline] pilot; on the other side of the runway waiting to take off; then also radioed to the tower that we were across the hold short line and needed further instruction. The tower said they had not heard any response from us and that we were to remain holding short of runway XXR at 1 and then cleared Aircraft Y to land again. The Aircraft Y pilot radioed that they were going around until the situation was figured out; I switched to the other radio and requested instructions again. The tower then gave us instructions to taxi onto runway XXR; turn right onto [taxiway] 2; turn right again to return to 1 and hold short. I responded with the clearance while the co-pilot taxied us on to the runway and back around to hold short at 1. The tower commented that we weren't responding to her transmissions to which both the Aircraft Y pilot; who was around a 10 mile final at the time of our first transmission; and the [same airline] pilot holding on the other side of the runway confirmed that they had heard all of our responses to the towers clearances. It is my belief that there is a radio dead spot in the area of Runway XXR and taxiway 1 as ground control; clearance; and both [other airline] pilots heard us clearly from varying distances and at different points at the airport; but the tower did not while we were at that intersection.Look into why the radio dead zone from that point to the tower while all other aircraft; ground; and clearance could hear us on that radio at different times and/or inform others of the issue so they can be sure to use a radio with a topside antenna for better ground ops/reception of the dead zone can't be addressed.


Second narrative: After taxi to runway XXR at ZZZ for departure the tower cleared us to line up and wait. Controller informed us there was a plane on a 5 mile final. The PNF acknowledged the instruction and began the Before Takeoff Checklist. I began moving to the runway.  As we taxied just beyond HOLD line with our tail above the line the controller issued an instruction for us hold short.  I immediately stopped; knowing that there was an aircraft on final I instructed the PNF to let her know we were past the HOLD line but not on the runway.  Controller never acknowledged our transmission and shortly thereafter repeated her instruction to hold short.  I then attempted to transmit to her we had moved past the hold short line but were not on the runway.  Another aircraft waiting on the other side of the runway let her know we were acknowledging her transmissions to which Controller responded that they had not heard our transmissions.  At that point I realized our transmissions on the #1 radio were not being heard in the tower possibly due to our antenna location and orientation but the other aircraft were hearing us fine.  I instructed the PNF to switch to the #2 radio and to try using the antenna on the top of the fuselage. Meanwhile the Controller instructed the aircraft on final to go-around.  We established contact with her on the #2 radio and were instructed to expedite onto the runway and clear at the first taxiway then taxi back and hold short for departure sequence.  The remainder of the flight continued without incident using the #1 radio.  Not sure why there was a dead spot with our radio at that position on the airport.  We had clear line of sight to the tower cab and antenna array off our nose and had no issues communicating with the ground controller during taxi out except we were oriented 90 degrees broadside to the tower before turning to face the tower upon reaching the end of the taxiway.I am not sure if this would be considered an incursion event since we were in compliance with the Tower clearance when we crossed the hold short line.  It wasn't until after crossing the line and the subsequent counter instruction to hold short that we were inside the clear area.


Synopsis: CE-525 flight crew reported communications failure caused a runway incursion and another aircraft to execute a go around.