Cessna 150
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 20; Flight Crew Total 6000
Communication Breakdown; Situational Awareness
Conflict Airborne Conflict
Flight Crew Took Evasive Action
Airspace Structure; Human Factors
Climb out of ZZZ; passing 2000 MSL for 4500 MSL VFR contacted Approach (for Class C passage. Heading out ZZZ was a heading of 187 for 10-15 miles; then a planned crossing [a large body of water] after gaining at least 3500 MSL for safe crossing (needed glide distance w/o floatation).At 2100 MSL climbing ATC directed an 'at/below 2500 MSL'. Student pilot replied 'unable 2500 after 60 seconds'. ATC did not acknowledge; but then gave two vectors to what I (the CFI) believed to be the other conflicting aircraft). 2 minutes later (approaching 3000 MSL) ATC queried our altitude and repeated the 2500 MSL restriction. I replied (as CFI) to ATC that we were unable to maintain that altitude because we needed to cross the water at a higher altitude. I heard in background a 'traffic alert' and the controller then called traffic '1-2 o'clock'. I sighted the traffic which was slightly moving in the windscreen; but not much. Possibly on collision course. I took the aircraft from the student and rolled a 45 degree right bank turn in VMC; reduced power and descended about 200 feet. I then called to ATC that traffic was in sight; no longer a factor; and I would keep in sight.I resumed the climb toward 4500 and crossed the water climbing through about 3300 MSL. After the crossing; ATC directed a call for debrief and I pledged to call after mission complete. Mission completed and I called ATC. Controller had gone home; so I followed the call in the morning as directed and debriefed ATC supervisor.
Cessna 150 Flight Instructor report being unable to comply with ATC altitude direction followed by an evasive maneuver for traffic.