Narrative:

I was flying a twin comanche with my student seeking a multi-engine rating. We planned to make an ILS approach to full stop with 1 engine inoperative (simulated). We requested a practice approach since the conditions were VFR at the time. After we contacted departure, we were told that ILS was not available and were offered an NDB which we accepted. We leveled off at 2000 ft. When we were cleared for the final approach I simulated an engine failure. The student aligned himself fine but had difficulty maintaining altitude. When he descended below MDA (1700 ft), I decided to give him back the engine and let him just fly the approach (on both engines). The student started climbing back to 2000 ft. The controller advised us about cessna traffic and I started looking. After a while I reported that traffic was in sight. The cessna was to our left and ahead of us at about 3000 ft passing to our right. The cessna and our aircraft were in VFR conditions. The student, however, climbed to approximately 2200 ft. Before descending through a thin cloud layer that had just formed, I asked the tower to verify that we could descend since both of us were under the impression that we were making a practice (VFR) approach. After our flight we were told to call the tower supervisor and were advised that according to their computer, the vertical separation from the other cessna was 700 ft at one moment, since we climbed to 2300 ft. I said that we reported the cessna in sight which the controller later confirmed. We were never aware that the cessna was IFR. In any case, I should have verified that we were making a practice approach and not assume that in VFR conditions, I do not have to pay close attention to our altitude.

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Original NASA ASRS Text

Title: AN SMA ON A PRACTICE APCH CONFLICTED WITH AN SMA THAT WAS IFR. ALTDEV ALT EXCURSION DURING PRACTICE INST APCH.

Narrative: I WAS FLYING A TWIN COMANCHE WITH MY STUDENT SEEKING A MULTI-ENG RATING. WE PLANNED TO MAKE AN ILS APCH TO FULL STOP WITH 1 ENG INOP (SIMULATED). WE REQUESTED A PRACTICE APCH SINCE THE CONDITIONS WERE VFR AT THE TIME. AFTER WE CONTACTED DEP, WE WERE TOLD THAT ILS WAS NOT AVAILABLE AND WERE OFFERED AN NDB WHICH WE ACCEPTED. WE LEVELED OFF AT 2000 FT. WHEN WE WERE CLRED FOR THE FINAL APCH I SIMULATED AN ENG FAILURE. THE STUDENT ALIGNED HIMSELF FINE BUT HAD DIFFICULTY MAINTAINING ALT. WHEN HE DSNDED BELOW MDA (1700 FT), I DECIDED TO GIVE HIM BACK THE ENG AND LET HIM JUST FLY THE APCH (ON BOTH ENGS). THE STUDENT STARTED CLBING BACK TO 2000 FT. THE CTLR ADVISED US ABOUT CESSNA TFC AND I STARTED LOOKING. AFTER A WHILE I RPTED THAT TFC WAS IN SIGHT. THE CESSNA WAS TO OUR L AND AHEAD OF US AT ABOUT 3000 FT PASSING TO OUR R. THE CESSNA AND OUR ACFT WERE IN VFR CONDITIONS. THE STUDENT, HOWEVER, CLBED TO APPROX 2200 FT. BEFORE DSNDING THROUGH A THIN CLOUD LAYER THAT HAD JUST FORMED, I ASKED THE TWR TO VERIFY THAT WE COULD DSND SINCE BOTH OF US WERE UNDER THE IMPRESSION THAT WE WERE MAKING A PRACTICE (VFR) APCH. AFTER OUR FLT WE WERE TOLD TO CALL THE TWR SUPVR AND WERE ADVISED THAT ACCORDING TO THEIR COMPUTER, THE VERT SEPARATION FROM THE OTHER CESSNA WAS 700 FT AT ONE MOMENT, SINCE WE CLBED TO 2300 FT. I SAID THAT WE RPTED THE CESSNA IN SIGHT WHICH THE CTLR LATER CONFIRMED. WE WERE NEVER AWARE THAT THE CESSNA WAS IFR. IN ANY CASE, I SHOULD HAVE VERIFIED THAT WE WERE MAKING A PRACTICE APCH AND NOT ASSUME THAT IN VFR CONDITIONS, I DO NOT HAVE TO PAY CLOSE ATTN TO OUR ALT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.