Small Aircraft; Low Wing; 1 Eng; Fixed Gear
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument
Flight Crew Last 90 Days 30; Flight Crew Total 30270; Flight Crew Type 100
Other / Unknown
Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action; Flight Crew Regained Aircraft Control
Weather
I was flying just slightly below a benign looking undercast and forward visibility was about 3 miles in haze. I suddenly encountered a severe downdraft. Normal cruise IAS in this aircraft is about 115 to 118 knots (at that altitude). I increased engine power to max and raised the pitch attitude to the point that my IAS decreased to 65 knots and was unable to arrest the decent. I lost about 600 feet during this event. The ARTCC frequency was busy and in the few seconds that transpired during the loss of altitude; I was unable to tell the controller what was happening. Plus; aircraft control demanded my full attention.Due to an ADS-B traffic display that I have installed in my aircraft; I know that there was IFR traffic at my 12 to 11 o'clock position at 7;000 MSL that I did not have in sight. At some point; very early in this event; knowing that IFR separation had been lost and separation was decreasing rapidly; I started a right turn (without Controller direction) to 300 degrees to at least increase the lateral separation from that traffic. (The ADS-B traffic display did not show any traffic behind me). At this point (probably; about 30 seconds after this event started); the Center Controller asked what was going on. After my brief explanation; the Controller then assigned my flight; 6;000 MSL and soon after I was given a left turn; back on course.I offered to make a phone call to the ARTCC after landing to explain the event further; but the Controller indicated that a phone call was unnecessary.
Glasair pilot reported encountering a severe downdraft enroute. This pushed him down 600 feet creating an airborne conflict which he deviated his track 30 degrees to avoid.