Narrative:

I left for ZZZ on an IFR flight plan. I almost didn't file for this flight; but a last minute look at the weather helped me decide that it might be easier to already be in the system if the weather should get any worse. When I was handed over to approach; the controller advised me to expect the visual into ZZZ. I acknowledged and continued inbound. I was showing 15 minutes out. Moments later I got the automated weather and it was advertising 700 feet and 5 miles visibility with winds 080 at 7 knots. I asked for the GPS 17 approach into ZZZ using zzzzz as my initial approach fix. All was going well; and I was still trying to decide if I would do a straight in approach or a circle to land. Just prior to zzzzz I listened to the weather again. Now it was 500 feet overcast; too low for a circling approach. I was going to have to do straight in. The winds on the ground were advertised as almost a direct crosswind from the east and less than 10 knots; but I noticed that my winds aloft were anywhere from 20-28 knots from the northeast. I was established on the approach now and inbound to ZZZZZ1. I listened to the weather once more. Now it was 400 feet. I knew that ZZZ1 as well as ZZZ2 were still great options; so I decided to continue on and see what it looked like when I got to minimums. I had noticed I was a dot low on my glide path; but the tailwind; rapidly changing weather on the ground; and the decision to either abort or continue the approach had taken much of my attention. Half a mile from ZZZZZ1 I crosschecked my altitude and the MDA at ZZZZZ1. Much to my dismay I saw that I had already descended well below the MDA for this approach; as I was at 2;400 MSL when I should have been at 3;000 crossing ZZZZZ1. I powered up and advised approach I was going missed. He asked me what I wanted to do and I requested to try the approach again. I was solo in the plane; and knew I could perform better than what I had just done. At this point I was already planning to go missed on my second try because I saw what the tailwind was doing to my approach profile and knew I didn't want to attempt a landing from that position. However; I didn't want to let my previous failure define my morning. My second approach went much better and I ignored my LNAV+V glide slope indication until I crossed ZZZZZ1 inbound. My biggest mistake was failing to thoroughly brief the approach and note that the MDA difference between ZZZZZ2 and ZZZZZ1 was only 100 feet. Upon reaching ZZZZZ2 the first time; I allowed myself to begin a descent without having a firm number in my mind that I was descending too. Even though I was hand flying; that altitude should have been put into my altitude pre-select box. I shouldn't have used my glideslope indication at all until crossing ZZZZZ1; and I should never have been okay with it showing I was low without turning more attention as to why. Even though my 530 was giving me an advisory glide path; this approach is a non-precision approach and should have been treated as such right from the beginning. My failure to recognize this initially; led me to see what I wanted to see; instead of what was actually happening. I did go missed the second time and diverted to ZZZ1 to wait for an improvement in the weather.

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Original NASA ASRS Text

Title: Beechcraft Baron pilot reported descending early during a GPS approach.

Narrative: I left for ZZZ on an IFR flight plan. I almost didn't file for this flight; but a last minute look at the weather helped me decide that it might be easier to already be in the system if the weather should get any worse. When I was handed over to approach; the controller advised me to expect the visual into ZZZ. I acknowledged and continued inbound. I was showing 15 minutes out. Moments later I got the automated weather and it was advertising 700 feet and 5 miles visibility with winds 080 at 7 knots. I asked for the GPS 17 approach into ZZZ using ZZZZZ as my initial approach fix. All was going well; and I was still trying to decide if I would do a straight in approach or a circle to land. Just prior to ZZZZZ I listened to the weather again. Now it was 500 feet overcast; too low for a circling approach. I was going to have to do straight in. The winds on the ground were advertised as almost a direct crosswind from the east and less than 10 knots; but I noticed that my winds aloft were anywhere from 20-28 knots from the northeast. I was established on the approach now and inbound to ZZZZZ1. I listened to the weather once more. Now it was 400 feet. I knew that ZZZ1 as well as ZZZ2 were still great options; so I decided to continue on and see what it looked like when I got to minimums. I had noticed I was a dot low on my glide path; but the tailwind; rapidly changing weather on the ground; and the decision to either abort or continue the approach had taken much of my attention. Half a mile from ZZZZZ1 I crosschecked my altitude and the MDA at ZZZZZ1. Much to my dismay I saw that I had already descended well below the MDA for this approach; as I was at 2;400 MSL when I should have been at 3;000 crossing ZZZZZ1. I powered up and advised Approach I was going missed. He asked me what I wanted to do and I requested to try the approach again. I was solo in the plane; and knew I could perform better than what I had just done. At this point I was already planning to go missed on my second try because I saw what the tailwind was doing to my approach profile and knew I didn't want to attempt a landing from that position. However; I didn't want to let my previous failure define my morning. My second approach went much better and I ignored my LNAV+V glide slope indication until I crossed ZZZZZ1 inbound. My biggest mistake was failing to thoroughly brief the approach and note that the MDA difference between ZZZZZ2 and ZZZZZ1 was only 100 feet. Upon reaching ZZZZZ2 the first time; I allowed myself to begin a descent without having a firm number in my mind that I was descending too. Even though I was hand flying; that altitude should have been put into my altitude pre-select box. I shouldn't have used my glideslope indication at all until crossing ZZZZZ1; and I should never have been okay with it showing I was low without turning more attention as to why. Even though my 530 was giving me an advisory glide path; this approach is a non-precision approach and should have been treated as such right from the beginning. My failure to recognize this initially; led me to see what I wanted to see; instead of what was actually happening. I did go missed the second time and diverted to ZZZ1 to wait for an improvement in the weather.

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.