Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor
Flight Crew Last 90 Days 120; Flight Crew Total 5000; Flight Crew Type 300
Troubleshooting; Workload; Human-Machine Interface
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Loss Of Aircraft Control
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed As Precaution; Flight Crew Regained Aircraft Control
Weather; Human Factors
Flight was a morning repositioning flight from ZZZ to SBP. [I] used self brief and a call to Flight Service to determine if clouds in SoCal were a solid deck or layers as icing was a factor. In discussions with the briefer the briefer commented that the Graphical Forecasts for Aviation tool showed both solid clouds and layers and that it was purely computer generated. I lamented the loss of the area forecast and asked for pireps; but none were available. I attempted to get on top by climbing to 12000 ft. and that worked until just E of PMD VOR. Initial entry into IMC produced no ice due to very little moisture and was able to receive vectors around radar returns of moisture. At some point north of RZS VOR; I picked up trace rime ice and noted an indicated airspeed decay and based on aircraft performance; suspected pitot ice. I cross-referenced indicated altitude with GPS altitude and ensured it was reliable. Not too long after that I experienced a downdraft and countered with pitch; unfortunately it was enough that I got down below Vs and was mushing downhill in a power on stall with no airspeed indicator. I told LA Center I was unable to maintain altitude and requested 10k; and set about -700VSI in order to get airspeed back and level at 10. This worked until another downdraft repeated the problem; I was able to get it leveled back at approx 9600 ft. and ATC issued an altitude alert for MVA; I had already selected the terrain display on the GPS. LA handed me off to Santa Barbara Approach who had lower MVAs and I was able to stabilize at about 9000 ft. Uneventful recovery via RNAV 29 at SBP and the airspeed came back to life at about 200 ft. AGL.Bring back the area forecast. The meteorologists narrative on flight conditions beats a computer model. Decision to take off into suspect icing with an unclear forecast and no PIREPS was foolhardy for an aircraft not FIKI equipped. Loss of reliable airspeed is worthy of advising ATC; not just recognizing and dealing with it. Not wanting to divert to an airport I hadn't prepared for; in IMC was the rationale; but again; poor. LA Center did a fantastic job of getting me to Santa Barbara approach as early as possible to get [a] lower MVA and he had briefed the Approach Controller who was ready with a vector and an altitude.In both my airline and military careers we train to unreliable airspeed but we usually do so where the aircraft has plenty of performance margin. I owned this plane for 3+ years and knew what the indicators of decreasing airspeed were without an indicator but at 12k; (which is as high as I've ever flown it and near the service ceiling) there wasn't any more power to add to arrest the descent from a downdraft. Fortunately I have flown that plane deep into stalls and knew that's what was happening. I let the new owner know the pitot heater is INOP and recommended he install a separate ammeter or indicator light to show the pitot heater is energized. Because of the static sources aft on the fuselage; there were no static pressure problems.The decision not to fly was clearly missed. Pitot heaters should have some indicator of operational status. Training to know pitch and power settings for flight is a glorious thing but it's never done at the edge of the performance envelope. AoA gauge here would have made this a non-event IF it was installed in an icing resistant position. (Heated vane or pressure ports on top and bottom of wing well aft of leading edge. Stall training needs to be to [a] fully developed stall (not FAAs current posture of 'first indication'. Many old and experimental aircraft have no indication but small buffet and nose drop. In this case in the Navion; I was making about 50% rated hp and was in a full power-on stall; if I hadn't recognized it by feel; I'd have likely kept pulling aft because I knew my airspeed was bad. A bad decision to fly put me in a bad situation of my own making; in a single engine aircraft; in IMC; with no airspeed indicator; at high altitude and no performance reserve; STALLED.
Navion Single Pilot reported entering icing conditions causing altitude and airspeed loss resulting in a stall. Pilot landed with ATC assistance.