Date: 201511
Local time of day: 1201-1800
Location: VRB.Airport, FL
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Operator: FBO
Operating under: Part 91
Flight plan: IFR
Mission: Training
Flight phase: Initial Approach
Airspace: Class E ZMA
ATC / advisory: Center ZMA
Reporter organization: FBO
Reporter function: Instructor
Reporter qualification: Flight Crew Multiengine; Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument
Human factors: Fatigue; Communication Breakdown; Situational Awareness
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: On active IFR flight plan on frequency with Miami Center on VOR 12R approach into Vero Beach airport; I requested holding instructions at BUEYE intersection (IAF); prior to approach for training purposes. Controller advised hold would be two or three turns for traffic sequencing. On inbound turn from first hold; Controller asked 'are you ready?' I responded by saying 'affirmative.' Controller advised of traffic '1000 ft below and to reference traffic prior to descent from 4000 ft to 3000 ft.' I advised Controller of traffic was in sight and began descent. The misunderstanding began with the assumption of what the Controller's question 'are you ready?' really meant. I concluded with the expectation that further descent instructions were to be given immediately; and consequently descended below the assigned altitude of 3000ft. Controller responded by asking what our current altitude was. When asked this question; I immediately recognized the mistake; and responded by saying 'correcting altitude from 2800 back to 3000 ft.' Controller responded by warning that we were not cleared for approach and to 'be aware of possible pilot deviation.' Some consideration given to the fact that I had approximately 5-6 hours of sleep the night before; while completing last flight on a 6 hour+ flight day; fatigue could've contributed to this event. I had to use the restroom facility on the ground urgently; which could've rushed the decision-making process to getting too far ahead of ATC instructions. I also could've asked Controller to clarify what he meant when asked 'are you ready?' which ended up being a vague and confusing instructions; meant to descend from 4000 ft to 3000 ft; not given approach clearance; and to ask Controller to 'confirm cleared for approach' if any question about whether or not to be cleared for approach was actually given. Moving forward; my students and I will make sure that we have written down on paper all assigned headings; altitudes; and clearances; cross out old headings; altitudes; and clearances; whenever new ones are given. Students and I will emphasize three-way aircraft control; as both of us were flying this approach together; since this was only the student's second time flying approaches on an IFR flight plan.




Synopsis: PA28 flight instructor reported departing from cleared altitude in response to a confusing clearance. Reporter cited fatigue as contributing.