Narrative:

Shortly after takeoff [on the second leg of a three leg IFR cross country training flight]; I looked up at the multi-functional display (mfd) and noticed a caution text for the oil pressure. I pressed the 'acknowledge' button and the oil pressure went back to normal operating range. Note: the gauge remained in the caution range for approximately 2-3 seconds total and then immediately returned to green. The indication was sporadic and I immediately started scanning the oil temperature gauge; cylinder head temperature gauge; exhaust gas temperature gauge; and listened for any change in the sounds from the engine. I also evaluated the smoothness of the engine. All gauges were normal and in the green and there were no abnormal sounds from the engine; no decrease in performance and nothing else abnormal noted. Since the oil pressure gauge sporadically deviated from normal only momentarily then remained in the green; there was no deviation from normal in any other gauges and I saw that there were no other indications that backed up the momentary drop in oil pressure; I determined the aircraft to be in an airworthy state and made a mental note to write up the aircraft for a possible gauge or sensor malfunction upon return to my home airport. I then continued my flight. We continued to the next airport; then requested and executed an ILS to a touch-and-go. We received our clearance back to base (on climb-out). After telling my student what the departure procedure said to do I looked up and noticed the caution light for oil pressure was back on and it immediately went back to normal. Again the gauge remained in the caution range for approximately 2-3 seconds total and then immediately returned to green. The indication was sporadic; just as before; and I immediately started scanning the oil temperature gauge; cylinder head temperature gauge; exhaust gas temperature gauge; and listened for any change in the sounds from the engine. I also evaluated the smoothness of the engine. Again all gauges were normal and in the green and there was no abnormal sounds from the engine; again no decrease in performance and nothing else abnormal noted. Since the oil pressure gauge sporadically deviated from normal only momentarily then remained in the green; there was no deviation from normal in any other gauges and I saw that there were no other indications that backed up the momentary drop in oil pressure; I determined the aircraft to be in an airworthy state. At this point I really made an effort to find anything that would indicate we had a systems problem rather than a gauge malfunction and I could not find anything that indicated we had a systems problem. The aircraft had great performance; and we had no abnormal sounds or vibrations from the engine. Other than the sporadic dip in oil pressure; all gauges were in the green and the oil pressure was also back in the green and remaining there. This further confirmed that the oil pressure gauge was malfunctioning and I deemed the aircraft airworthy and continued to base. At no time from here after was there any change in the engine gauges nor did we have anymore oil caution lights. We were handed off to approach and I requested a hold at an intersection off of the VOR. We entered the hold and due to a strong crosswind from the east my student was having a hard time becoming established and we ended up holding for about twenty minutes so he could learn from the winds and get better established. We then told approach we were ready to leave the hold and continue to base and did proceed on course. I requested a 12 DME arc from the southwest to the northeast (counter-clockwise) into the VOR DME approach to a full stop. At approximately 20 miles southwest of the airport; we started a descent from 5;000 to 3;000 ft to intercept a 12 DME arc to the northeast into a VOR approach. Soon after we got cleared down to 2;000 from 3;000 and were about 12.3 DME from the airport. Descending out of 3;000 (at 700FT per min) was when the engine coughed/ran rough (for a split second) the first time. I scanned the gauges and they were all in the green and performance level was normal. At this time my student had the flight controls and we continued in our descent. About 30 seconds later the engine coughed again but this time my student and I both knew the sound was abnormal. Immediately when I heard the cough of the engine; I looked up and we were descending through 2;500 ft. Within seconds (just barely long enough for me to look at the altimeter) we heard a bang and the engine started vibrating and making a slipping and grinding noise. I took the flight controls while continuing my scan and noted we only had about 1;800 rpms. I gave full throttle; turned the fuel pump to boost; and mixture full rich and told approach we had a partial power loss and told my student to back me up on the emergency checklist. I knew from the vibration and noise that something must have broken inside the engine and I immediately started looking for a place to land. I remember looking at the gauges but I honestly do not remember at that point what they read. Everything happened very; very fast and my focus was on the fact that our altitude was only about 2;500 ft and with full power we only had 1;800 rpms. My focus became landing the aircraft safely and immediately. The controller was very professional and she kept a calm voice the whole time while giving us distances to the two nearest airports. I told her we could not make either field. We were then passing through 2;500 ft when the engine completely gave out and it got quiet. I had already pitched for best glide speed which was 95 KTS. I told approach that we lost the engine and we would be landing on the highway. She said she would send out help immediately. I momentarily thought about pulling the caps handle on the aircraft but quickly dismissed the idea (while not letting fear over take me) because I still had full control of the aircraft and decided to fly it down. The primary flight display was indicating we had a 31 KT crosswind so I then turned to a west heading to use the 31 KT tailwind to push us pass the bridges. Once cleared of the last overpass; I told my student we were clear of the bridges but we still had to clear the signs. I then turned into the wind; lined up with the highway; passed over a road sign stretching across the highway; flew under the next sign and I determined there were a group of cars on the highway with enough spacing in-between them for a safe landing with no harm to the cars and their passengers. I then touched down just prior to a bridge so we could safely roll out under it. I let the plane roll as far as it would; trying to make the off ramp so that I would not block the road and become a danger to traffic. Unfortunately; the airplane stopped short of the exit. I would like to note that my actions for determining the airworthiness of the aircraft after a momentary; sporadic dip in oil pressure with all other gauges in the green; were based on the information in the cirrus poh which states; 'if low oil pressure is accompanied by normal oil temperature; it is possible that the oil pressure sensor; gauge; or relief valve is malfunctioning.' based on my assessment of the aircraft's performance at the two times we had the momentary drop; it appeared we were dealing with a malfunctioning gauge; which made it practical to write up and investigate upon return to our home airport.

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Original NASA ASRS Text

Title: SR20 Instructor with student reports oil pressure anomalies while on a three leg instrument training flight. Some time after the second momentary dip in oil pressure the engine begins to run very rough and eventually stops. Unable to reach an airport the decision is made to land on a highway; which is accomplished successfully without damage.

Narrative: Shortly after takeoff [on the second leg of a three leg IFR cross country training flight]; I looked up at the Multi-Functional Display (MFD) and noticed a caution text for the oil pressure. I pressed the 'acknowledge' button and the oil pressure went back to normal operating range. Note: the gauge remained in the caution range for approximately 2-3 seconds total and then immediately returned to green. The indication was sporadic and I immediately started scanning the oil temperature gauge; cylinder head temperature gauge; exhaust gas temperature gauge; and listened for any change in the sounds from the engine. I also evaluated the smoothness of the engine. All gauges were normal and in the green and there were no abnormal sounds from the engine; no decrease in performance and nothing else abnormal noted. Since the oil pressure gauge sporadically deviated from normal only momentarily then remained in the green; there was no deviation from normal in any other gauges and I saw that there were no other indications that backed up the momentary drop in oil pressure; I determined the aircraft to be in an airworthy state and made a mental note to write up the aircraft for a possible gauge or sensor malfunction upon return to my home airport. I then continued my flight. We continued to the next airport; then requested and executed an ILS to a touch-and-go. We received our clearance back to base (on climb-out). After telling my student what the departure procedure said to do I looked up and noticed the caution light for oil pressure was back on and it immediately went back to normal. Again the gauge remained in the caution range for approximately 2-3 seconds total and then immediately returned to green. The indication was sporadic; just as before; and I immediately started scanning the oil temperature gauge; cylinder head temperature gauge; exhaust gas temperature gauge; and listened for any change in the sounds from the engine. I also evaluated the smoothness of the engine. Again all gauges were normal and in the green and there was no abnormal sounds from the engine; again no decrease in performance and nothing else abnormal noted. Since the oil pressure gauge sporadically deviated from normal only momentarily then remained in the green; there was no deviation from normal in any other gauges and I saw that there were no other indications that backed up the momentary drop in oil pressure; I determined the aircraft to be in an airworthy state. At this point I really made an effort to find anything that would indicate we had a systems problem rather than a gauge malfunction and I COULD NOT find anything that indicated we had a systems problem. The aircraft had great performance; and we had no abnormal sounds or vibrations from the engine. Other than the sporadic dip in oil pressure; all gauges were in the green and the oil pressure was also back in the green and remaining there. This further confirmed that the oil pressure gauge was malfunctioning and I deemed the aircraft airworthy and continued to Base. At no time from here after was there any change in the engine gauges nor did we have anymore oil caution lights. We were handed off to Approach and I requested a hold at an intersection off of the VOR. We entered the hold and due to a strong crosswind from the east my student was having a hard time becoming established and we ended up holding for about twenty minutes so he could learn from the winds and get better established. We then told Approach we were ready to leave the hold and continue to Base and did proceed on course. I requested a 12 DME arc from the southwest to the northeast (counter-clockwise) into the VOR DME approach to a full stop. At approximately 20 miles southwest of the airport; we started a descent from 5;000 to 3;000 FT to intercept a 12 DME arc to the northeast into a VOR approach. Soon after we got cleared down to 2;000 from 3;000 and were about 12.3 DME from the airport. Descending out of 3;000 (at 700FT per min) was when the engine coughed/ran rough (for a split second) the first time. I scanned the gauges and they were all in the green and performance level was normal. At this time my student had the flight controls and we continued in our descent. About 30 seconds later the engine coughed again but this time my student and I both knew the sound was abnormal. Immediately when I heard the cough of the engine; I looked up and we were descending through 2;500 FT. Within seconds (just barely long enough for me to look at the altimeter) we heard a bang and the engine started vibrating and making a slipping and grinding noise. I took the flight controls while continuing my scan and noted we only had about 1;800 RPMs. I gave full throttle; turned the fuel pump to boost; and mixture full rich and told Approach we had a partial power loss and told my student to back me up on the emergency checklist. I knew from the vibration and noise that something must have broken inside the engine and I immediately started looking for a place to land. I remember looking at the gauges but I honestly do not remember at that point what they read. Everything happened very; very fast and my focus was on the fact that our altitude was only about 2;500 FT and with full power we only had 1;800 RPMs. My focus became landing the aircraft safely and immediately. The Controller was very professional and she kept a calm voice the whole time while giving us distances to the two nearest airports. I told her we could not make either field. We were then passing through 2;500 FT when the engine completely gave out and it got quiet. I had already pitched for best glide speed which was 95 KTS. I told Approach that we lost the engine and we would be landing on the highway. She said she would send out help immediately. I momentarily thought about pulling the CAPS handle on the aircraft but quickly dismissed the idea (while not letting fear over take me) because I still had full control of the aircraft and decided to fly it down. The primary flight display was indicating we had a 31 KT crosswind so I then turned to a west heading to use the 31 KT tailwind to push us pass the bridges. Once cleared of the last overpass; I told my student we were clear of the bridges but we still had to clear the signs. I then turned into the wind; lined up with the highway; passed over a road sign stretching across the highway; flew under the next sign and I determined there were a group of cars on the highway with enough spacing in-between them for a safe landing with no harm to the cars and their passengers. I then touched down just prior to a bridge so we could safely roll out under it. I let the plane roll as far as it would; trying to make the off ramp so that I would not block the road and become a danger to traffic. Unfortunately; the airplane stopped short of the exit. I would like to note that my actions for determining the airworthiness of the aircraft after a momentary; sporadic dip in oil pressure with all other gauges in the green; were based on the information in the Cirrus POH which states; 'If low oil pressure is accompanied by normal oil temperature; it is possible that the oil pressure sensor; gauge; or relief valve is malfunctioning.' Based on my assessment of the aircraft's performance at the two times we had the momentary drop; it appeared we were dealing with a malfunctioning gauge; which made it practical to write up and investigate upon return to our home airport.

Data retrieved from NASA's ASRS site as of April 2012 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.