Date: 201902
Local time of day: 0601-1200
Location: RAC.Airport, WI
Flight conditions: VMC
Light: Daylight
Aircraft: Small Aircraft
Operator: FBO
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Takeoff / Launch
Airspace: Class G RAC
ATC / advisory: CTAF RAC
Reporter organization: FBO
Reporter function: Instructor
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Commercial; Flight Crew Flight Instructor
Human factors: Situational Awareness; Training / Qualification; Confusion
Second reporter function: Trainee; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Detector: Person Flight Crew
When detected: In-flight
Contributing factors: Airport; Chart Or Publication; Human Factors
Primary problem: Human Factors

Narrative: I was acting as the Certified Flight Instructor providing Flight Instruction to a Commercial pilot applicant and PIC (Pilot in Command) for the flight.We departed our base airport for a routine training flight and headed towards RAC to practice takeoffs and landings. Winds were light and favoring runway 32; this was my second time to RAC and first time using runway 32. My student and I noted that there were displaced thresholds at all four runways and we would not land early on them. After 3-4 uneventful touch and goes we opted for a full stop landing; made the first left turn off and taxied back to Runway 32.After holding short for landing traffic and noting one aircraft behind us we proceeded to cross the hold short line and followed the taxiway to runway 32 where my student planned on demonstrating a Short Field takeoff procedure for practice. After lining up and stopped; we were approximately 220 feet prior to the runway threshold. My student noted unusual paint markings in front of us (Taxi way lines leading up to four yellow arrows) and asked if we were ok to takeoff here. I checked out the markings and failed to notice two things. - That the arrows were yellow and not white as with displaced thresholds.- That the area prior to the yellow arrows did not display any long dashed lines with white arrows that also accompany displaced thresholds.In the heat of the moment I did not want to be lingering on an active runway trouble shooting the markings and assumed these markings were displaced threshold markings that accompanied the other 3 runways at RAC. I instructed my student to continue the takeoff which was uneventful. During the climb out we received a radio transmission from the aircraft that was holding behind us and watched us. They informed us that 'the displaced threshold was recently changed to a takeoff displaced threshold.' We acknowledged them and made sure to look into it. We departed the area to finish our lesson.Upon further investigation we found runway 32 to be labeled as what looks like a Relocated Runway Threshold. Neither of us had encountered one of these before and were unfamiliar. We noted the difference in color of the arrows leading up to the threshold; the taxiway lines leading up to it and the lack of lead in white arrows seen on displaced thresholds. Notes:- The most important source we found clarifying what the taxiway leading up to the runway may be used for is located in FAA-H-8083-25B Pilots Handbook of Aeronautical Knowledge page 14-5 -7. This paragraph says the closed portion of the runway is not available for use by aircraft for takeoff or landing; but is available for taxi.- No NOTAMS were issued indicating the runway was shortened.- The Chart Supplement does note notate any displaced threshold for runway 32; but does show a taxiway preceding the runway.- Google Maps shows the relocation arrows were once white. Not sure what this means but a change did happen at some point. Possibly supporting the pilot who told us about the recent change in displaced threshold. Time of picture is unknown. - AIM 2-3-3 and 2-3-4 explain Relocated threshold and taxi way preceding a displaced threshold. Neither mention if the area preceding the runway can be used to power up and takeoff on. Contributing factors:- Fairly new airport for myself and PIC (Pilot in Command).- First time using this runway- Failure to note the difference in threshold and the lack of displaced threshold symbol on the chart supplement. - First time seeing this kind relocated threshold.- Failure to confirm my students concerns; delay takeoff and taxi up to the threshold for takeoff.Corrective actions:Now that we have realized our error. Emphasis will be placed on remediation for both of us. I have already completed the following FAA WINGS courses and advised my student to do the same.- ALC-48 Hold Short for Runway Safety- ALC-94 Runway Safety CompletedWe will also be reviewing the following FAA sources to ensure we understand the difference between a displaced threshold and a taxiway leading up to relocated threshold.- FAA-H-8083-25B Pilots Handbook of Aeronautical Knowledge page 14-5 through 14-7- AIM 2-3-3 and 2-3-4- AC150-5370-2G (2.7.1.1) Page 2-8- AC 150/5300-13A Page 52Unsolved issues:- What we are still unsure about is why this one runway does not have a displaced threshold and instead has this relocated threshold.- Relocated thresholds sound like they are a temporary event per the AIM; this runway does not look like a temporary thing so why is it painted as such?Suggestions:The airport should implement signage at the hold short line for runway 32 reminding pilots no takeoff prior to runway threshold is allowed; add a note in the airport remarks of the Chart Supplement or add a NOTAM for it.


Second narrative: I was practicing takeoffs and landings towards a commercial certificate. An instructor was in the right seat. We had completed a full-stop landing on runway 32 and taxied back for a short field takeoff. Taxiing to into position for departure I thought the runway had a displaced threshold but the markings weren't what I was used to. I asked my instructor and we decided that it was a displaced threshold. On takeoff another aircraft informed us that we had started out takeoff roll on the taxiway.After getting airborne and reviewing the situation; we determined that runway 32 did not have a displaced threshold but rather a taxiway aligned with the runway.Contributing to the incident was our desire to not hold up the aircraft waiting behind us. All of the other runway approach ends at KRAC have displaced thresholds; which probably helped us convince ourselves that 32 also had a displaced threshold.In an effort to prevent this happening again; I reviewed the FAA's materials related to runway and taxiway markings. This also emphasized the need to thoroughly read the Chart Supplement for every destination airport; even ones that one flies to regularly. Finally; we should not have allowed ourselves to feel rushed just because there was somebody in line behind us.


Synopsis: GA instructor and student reported departing from taxiway which was recently changed from a displaced threshold.