Skyhawk 172/Cutlass 172
Flight Crew Multiengine; Flight Crew Commercial; Flight Crew Instrument
Flight Crew Last 90 Days 35; Flight Crew Total 2600; Flight Crew Type 110
Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Environment - Non Weather Related
Flying back from ZZZ to ZZZ1 I decided to file and fly on an IFR flight plan due to possible unintended low visibility due to the bushfires. In cruise at 10000 ft. approaching ZZZZZ waypoint; the aircraft started to sink. My initial response was to increase power; reduce speed to initiate a climb. The sink rate continued and after then looking at my engine oil temp/pressure gauges; I was able to verify the sink was a big downdraft from the lee side of the mountains I was crossing and the aircraft was unable to out-climb it. As I was about to notify ATC; the controller contacted me first and asked if everything was all right. I let him know I had a downdraft and was unable to stop the descent. He very quickly gave me a block altitude to work with. During the next few minutes I configured the plane to best rate of climb and went through different ways to increase aircraft performance. Unfortunately none of these actions helped and I was quickly at the bottom of my block altitude. I then radioed and requested vectors to a lower MVA (Minimum Vectoring Altitude) and was promptly given a heading of a westerly direction. The controller then asked if I was VMC and in sight of the mountains and I responded yes. He then said if I was happy to cancel IFR he could give me a lower MVA VFR. I proceeded to cancel IFR and carried on the flight VFR under flight following. At this point I had been vectored away from the downdraft and was able to begin a climb again and carry on to my destination.I could not have been happier with the response from the controller and with great communication we were able to make a plan to avoid any dangerous situation. I have learned multiple things from this situation and will make sure I pass them on to as many others as I can. The main thing will be to take a non-mountainous route when there are strong winds forecasted and even though I was 3000 ft. above the highest point; downdrafts can still effect small piston aircraft.The other important lesson is to communicate as early as possible with ATC if any abnormality arises and if not on an IFR flight plan; always opt for VFR flight following so you are always in immediate contact with the correct controllers in any situation. I hope others can learn from this situation.
C-172 Pilot reported a rapid loss of altitude due to a mountain-related downdraft; which resulted in multiple clearance adjustments.