Date: 201707
Local time of day: 1201-1800
Location: OWD.Airport, MA
Flight conditions: Marginal
Weather elements / visibility: Rain; 3
Light: Daylight
Aircraft: Small Aircraft
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Final Approach
Airspace: Class D OWD
ATC / advisory: Tower OWD
Reporter organization: Personal
Reporter function: Single Pilot
Reporter qualification: Flight Crew Instrument; Flight Crew Private
Human factors: Workload
Anomaly: Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Contributing factors: Human Factors; Weather
Primary problem: Human Factors

Narrative: During approach in to OWD; I was in IMC being vectored to final at 2000 feet. Once cleared for the GPS 35 approach; I began my descent along the glideslope to the FAF which was CUPUG at 1700 feet. The rain was sufficiently heavy that it was impacting my static ports. I was seeing sudden swings in vertical speed and substantial variations in indicated altitude that slowly returned to normal; but I remained on/near glideslope as indicated by the LPV guidance. Due to the turbulence and rain; it was a high workload situation. Not far beyond the FAF; OWD reported a low altitude alert. I reported that my altimeter setting was correct and that I was on the GPS glide path. I was one dot low on the LPV glide slope. At about this time I also had visual ground contact. This was consistent with PIREP from a previously arriving aircraft observing ceilings at 1700 feet. I struggled to maintain a stable descent rate as I continued the approach and remained low on the glideslope but on-scale. The Tower issued two more low altitude alerts; presumably because my varying descent rate was causing a predicted insufficient altitude combined with being a little low on the glideslope. With each low altitude alert; I added some power and back pressure on the yoke; which I needed to do anyway to bring the glideslope needle back down. I didn't note the exact altitude I had the runway in sight but it took me a few moments due to lack of familiarity with the area. I would estimate 600-800 feet AGL. The PAPI was indicating 3 red so I leveled out to get 2 white and two red and continued to a normal landing. The aircraft's GPS provides forward looking terrain alerts and none were received during the approach.A lesson learned from this is that I should consider alternate airports if the rain is heavy enough to affect instruments or considered use of the alternate static source. I should have more seriously considered going missed upon receiving follow up low altitude alerts. My logic was that as long as I had the LPV glideslope I was protected; but if I desensitize myself to that useful tool then I may not help me in a situation in which I made a mistake in setting up or interpreting the approach.




Synopsis: GA pilot reported receiving several low altitude alerts on the GPS 35 approach to OWD during heavy rain.