Date: 202101
Local time of day: 1201-1800
Location: GSO.Airport, NC
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground GSO
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Situational Awareness; Distraction
Second reporter function: Captain
Anomaly: Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Detector: Person Air Traffic Control
When detected: Taxi
Result: Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: I was acting as PIC (Pilot in Command) and PF (Pilot Flying). On taxi out from maintenance facility; ATC Instructions were 'cleared to taxi Mike; Alpha cleared to cross runway 14.'Just prior to reaching the intersection of Mike taxiway and runway 14 ATC Instructions heard was 'clear to cross runway 14' The PM (Pilot Monitoring) read back; 'cleared to cross runway 14.'At the point just past the hold short lines and the runway ATC asked if we were holding short. A short exchange was made between us and ATC as ATC stated we were to hold short. An aircraft was held in position on runway 14 and ATC instructed us to proceed and cross runway 14.This flight was an test flight as the day before we had a number 2 engine failure. During taxi out a series of checklist items are accomplished in addition to the normal SOP line flight checklist items. Due to the preceding day's events and root cause of the engine failure information obtained; I ran additional thrust settings changes while on taxi to induce multiple pneumatic pressure bumps and fuel flow oscillations to further test the engine performance. Both the PF and the PM have an abundance of items to accomplish during taxi out on a test flight; I heard two separate clearances to cross runway 14; repeated the clearance verbally to the PM while physically scanning the approach end to my left stating 'cleared to cross 14; clear on final.'While conducting test flights the 'normal everyday expected clearances' and communications exchanges with ATC are handled quickly while simultaneously running additional checks pertinent to specific tasks.


Second narrative: I was acting as the pilot monitoring on flight.  The day prior we had a block turn back due to an engine shut down during taxi out for the test flight.On an FCF flight taxi time is quite busy. We have many checks to perform; sometimes with very little taxi time to do it. Also; on this day we were very concerned that the engine was properly repaired and we were performing extra checks to make sure that we did not have an engine failure on the takeoff.We were told to taxi to runway 05R on Mike and cross runway 14.  I read back instructions to Taxi to runway 05 R on Taxiway Mike and Cross runway 14. As we were doing our taxi checks for the test flight I once again heard instructions to cross runway 14; and I again read back clear to cross runway 14. After we crossed the hold short line for runway 14 Ground Control instructed us to stop and asked if we had cross the hold short line for 14. I advised that we had and he had then told me that he gave us instructions to hold short Of runway 14. I advised him that I read back clearance to once again cross runway 14. There was an aircraft waiting to takeoff on runway 14. He advised us that we were now clear to cross 14 and contact Tower for takeoff on runway 05R.  We had no further communications with the Ground Controller and we contacted Tower for a normal takeoff. I was acting as the pilot monitoring on [a] test flight. The day prior we had a block turn back due to an engine shut down during taxi out for the test flight.On [a test] flight taxi time is quite busy. We have many checks to perform; sometimes with very little taxi time to do it. Also; on this day we were very concerned that the engine was properly repaired and we were performing extra checks to make sure that we did not have an engine failure on the takeoff.We were told to taxi to runway 05R on Mike and cross runway 14. I read back instructions to Taxi to runway 05 R on Taxiway Mike and Cross runway 14. As we were doing our taxi checks for the test flight I once again heard instructions to cross runway 14; and I again read back clear to cross runway 14. After we crossed the hold short line for runway 14 Ground Control instructed us to stop and asked if we had cross the hold short line for 14. I advised that we had and he had then told me that he gave us instructions to hold short Of runway 14. I advised him that I read back clearance to once again cross runway 14. There was an aircraft waiting to takeoff on runway 14. He advised us that we were now clear to cross 14 and contact Tower for takeoff on runway 05R. We had no further communications with the Ground Controller and we contacted Tower for a normal takeoff.As usual; I will do my utmost best to maintain situational awareness while taxing to or from a runway. In this case; during the busy environment of a test flight I specifically heard that we were told twice that we were cleared to cross the active runway; and I read back twice that we were cleared to cross the active runway. It would be my hope that the Controller would hear the miscommunication and correct the situation before we actually crossed the hold short line. In the future I will be much more diligent in listening to the Ground Controller instructions.As usual; I will do my utmost best to maintain situational awareness while taxing to or from a runway. In this case; during the busy environment of a test flight I specifically heard that we were told twice that we were cleared to cross the active runway; And I read back twice that we were cleared to cross the active runway. It would be my hope that the Controller would hear the miscommunication and correct the situation before we actually crossed the hold short line. In the future I will be much more diligent in listening to the Ground Controller instructions.


Synopsis: Air carrier flight crew reported misunderstanding GSO ATC taxi instructions resulting in a runway incursion.