Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Flight Crew Instrument; Flight Crew Private
Flight Crew Last 90 Days 28; Flight Crew Total 425; Flight Crew Type 50
Situational Awareness
Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control
Human Factors
We were on an IFR flight to ISP; being vectored for the RNAV 24 Approach. The approach was uneventful and we were in a smooth; overcast layer getting ready to turn onto the final approach segment at 2000 feet; near UKEGE about 5NM from ISP. Just as we were handed off to the Tower and cleared for the approach; we were swept up by a sudden windshear or turbulence event that rendered our [aircraft] almost uncontrollable; pushing us to a bank angle in excess of 70 degrees and an extreme nose up attitude. By the time I was able to recover; we had lost nearly 800 feet and had turned through about 150 degrees. As I recovered back to straight and level flight; I turned to get reestablished on the inbound final course. At this point; we experienced a second; but less severe; episode about a mile from the original event. The altitude drop put us in visual conditions; and since I'm very familiar with ISP (I did most of my flight training there) and had the runway in sight; I opted to complete the approach from that location. We were below the glideslope; but in visual conditions; and I was concerned about the risk of climbing back into the unknown conditions above us. Thankfully; we made an uneventful landing and the aircraft wasn't damaged.There was no advance notice of this turbulence. Before being vectored for our approach; we were flying at 3000 feet; roughly the top of the overcast layer. We saw a [solid] overcast layer with occasional breaks - no big cumulonimbus; no ominous dark clouds; no lightning; no precipitation; nothing on the NEXRAD image in the airplane (we have XM weather); and apparently nothing on ATC's radar. Even as we approached; conditions seemed fairly benign - the air in the vicinity was smooth as well...then without warning; we are nearly inverted.If this had happened a few miles closer to the airport; there might not have been adequate altitude to recover; and we'd be an NTSB statistic. There needs to be a technological way that these dangerous conditions can be detected.
GA pilot reported temporarily losing control of aircraft in turbulence while executing approach into airport.