PA-31 pilot reported descending below the published altitude during a GPS approach due to misreading...

Attributes
ACN	1452717
Time
Date	201705
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	PA-31 Navajo/Chieftan/Mojave/T1040
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Engineer Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 45 Flight Crew Total 17300 Flight Crew Type 1350
Events
Anomaly	Deviation - Altitude Overshoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

Narrative:

Flying GPS/lpv runway 13. Misread approach chart and saw alt from if to FAF as 2000 ft. Rather than charted 2400 ft. Approaching FAF tower informed me I was indicating 2000 ft. Rather than 2400 ft. Shortly before this at about 2250 ft.; avidyne ifd 440 had given me a yellow low altitude warning; but I assumed it was in error. Did not get a terrain warning since I remained at least 1200 ft. Above terrain/obstacles below or ahead of me. I was tired and too comfortable flying into my home field though it was an approach I had not flown before. I should not have assumed the low altitude warning was an error; and instead rechecked the approach chart immediately. I held 2000 ft. Till intercepting the gp (glide path).

Original NASA ASRS Text

Title: PA-31 pilot reported descending below the published altitude during a GPS approach due to misreading the chart.

Narrative: Flying GPS/LPV RWY 13. Misread approach chart and saw alt from IF to FAF as 2000 ft. rather than charted 2400 ft. Approaching FAF tower informed me I was indicating 2000 ft. rather than 2400 ft. Shortly before this at about 2250 ft.; Avidyne IFD 440 had given me a yellow low altitude warning; but I assumed it was in error. Did not get a terrain warning since I remained at least 1200 ft. above terrain/obstacles below or ahead of me. I was tired and too comfortable flying into my home field though it was an approach I had not flown before. I should not have assumed the low altitude warning was an error; and instead rechecked the approach chart immediately. I held 2000 ft. till intercepting the GP (Glide Path).

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.