Narrative:

I was departing on an IFR flight in visual conditions to ZZZ with an instrument student. We just got to our cruising altitude 9;000 ft that center had assigned us. About 10 miles north of the ZZZ VOR we started to experience moderate turbulence and a severe downdraft; at this point the student could no longer maintain altitude; so I took the controls and immediately went full power and pitched for our aircrafts best rate of climb speed to try to maintain the altitude that we were at; however the aircraft did not have the performance to do that and we were still descending. We were quickly losing altitude and we were quickly approaching our MEA for the route of flight on V85; at this point I tried to lean the mixture to get a little more performance from out engine; because we had not yet leaned it for cruising flight. I was able to look at the vertical speed indicator; and it looked to be past its limits of 2;000 ft/min; so the downdraft must have been even worse than that. Center quickly got ahold of us and gave us a low altitude warning; and that we were below the minimum IFR altitude for that route of flight. They informed us that we were at 8;300 ft. We responded and told them we were unable to maintain altitude because of moderate turbulence and a bad downdraft. We also told them we were trying to climb and would let them know as soon as we were able to climb or even maintain an altitude. Within minutes of the start of the downdraft we finally were able to start a shallow climb; about 300 ft/min back to 9;000 ft. I gave the student back the controls and the rest of the flight went smooth. After we landed we inspected the aircraft and the engine and found nothing wrong. After we landed and were able to think about what happen we figured it must have been a severe mountain wave coming from the west our route of flight.

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Original NASA ASRS Text

Title: C172 flight instructor reported severe mountain wave resulting in uncontrolled descent below the MVA.

Narrative: I was departing on an IFR flight in visual conditions to ZZZ with an instrument student. We just got to our cruising altitude 9;000 ft that Center had assigned us. About 10 miles north of the ZZZ VOR we started to experience moderate turbulence and a severe downdraft; at this point the student could no longer maintain altitude; so I took the controls and immediately went full power and pitched for our aircrafts best rate of climb speed to try to maintain the altitude that we were at; however the aircraft did not have the performance to do that and we were still descending. We were quickly losing altitude and we were quickly approaching our MEA for the route of flight on V85; at this point I tried to lean the mixture to get a little more performance from out engine; because we had not yet leaned it for cruising flight. I was able to look at the Vertical Speed Indicator; and it looked to be past its limits of 2;000 ft/min; so the downdraft must have been even worse than that. Center quickly got ahold of us and gave us a low altitude warning; and that we were below the minimum IFR altitude for that route of flight. They informed us that we were at 8;300 ft. We responded and told them we were unable to maintain altitude because of moderate turbulence and a bad downdraft. We also told them we were trying to climb and would let them know as soon as we were able to climb or even maintain an altitude. Within minutes of the start of the downdraft we finally were able to start a shallow climb; about 300 ft/min back to 9;000 ft. I gave the student back the controls and the rest of the flight went smooth. After we landed we inspected the aircraft and the engine and found nothing wrong. After we landed and were able to think about what happen we figured it must have been a severe mountain wave coming from the west our route of flight.

Data retrieved from NASA's ASRS site 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.