Date: 201902
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Rain; 1.5
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Navigational Equipment and Processing
Component problem: Failed
Reporter organization: Personal
Reporter function: Single Pilot; Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument
Human factors: Training / Qualification
Anomaly: Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; Flight Crew Diverted
Contributing factors: Human Factors; Aircraft
Primary problem: Aircraft

Narrative: On an IFR flight from to ZZZ; I encountered a glideslope indicator failure when established on the ILS 21L into ZZZ. Worse-than-forecasted and deteriorating weather conditions plus climbs for traffic avoidance with ZZZ Center had consumed more fuel than planned and had burned all of fuel carried in excess of fuel to alternate [plus] 45 minutes. Once glide slope failure was determined; I was vectored for one more attempt of the ILS after troubleshooting the VLOC/GPS [VOR/Localizer/Global Positioning System] selector for user error. After determining that pilot error wasn't the cause of the failure; I told ZZZ Approach at that point; I was going to my filed alternate of ZZZ1. Once on track to ZZZ1; I determined that winds aloft created roughly 25 kts stronger headwind than forecasted and with our fuel situation would prevent us from getting to ZZZ1. At that point with roughly 8 gallons of fuel indicated total; I [advised ATC] for low fuel. ZZZ Approach assisted me with determining whether at surrounding airports and found that ZZZ2 had ceilings about 100 feet above minimums for the RNAV 29. ZZZ1 also has ASR [Airport Surveillance Radar] for the RNAV 29. I elected for the ASR on the RNAV 29. ZZZ1 Approach controllers executed the ASR approach from the FAF of ZZZZZ. I gained visual of the field environment at the minimums of 1;540 feet and quickly gained visual of the runway at about 1/4 nm from the approach end of Runway 29 and about 1/8 nm right of centerline. A landing from minimums was conducted using normal maneuvers to Runway 29.This event was a great example of the Swiss Cheese model of risk management; enough small issues accumulated that a larger issue occurred. During preflight planning; I had selected a cruising altitude of 4;000 feet due to the favorable winds and had noted that higher altitudes had much worse headwinds. When ZZZ Center issued us a climb to 8;000 feet; I had just checked fuel and we were burning less fuel than planned and was indicating more fuel on board than planned at the last waypoint. I believe this set a confirmation bias that led me to believe the fuel savings up to that point would cancel out with the climb and added headwind; and for the most part it did. Once we started our descent down to 6;000 feet; we were still on track with indicated vs. planned fuel on board; but headwinds didn't lighten up at lower altitudes as forecasted. This is when our indicated fuel on board dropped below planned fuel on board. At this point; I didn't see this as an issue because I had planned on having over an hour of fuel more. However; the failure of the glideslope indicator and increased headwind on track to the alternate were the last links in the chain of issues that arose the closer we get to ZZZ. Knowing that fuel had already dropped below what was planned; I should have made the decision as soon as the glideslope indicator failed to go to the filed alternate; but I got too fixated resolving the problem and was convinced that I improperly set up the instruments that I accepted a vector for another attempt instead of taking control of the situation and immediately diverting to the alternate. Having done that; I could have avoided another 20-30 minutes of vectoring and would have had the fuel to get to ZZZ1.




Synopsis: Cessna 172 pilot encountered a glideslope indicator failure while on approach. Pilot attempted to troubleshoot and ran low on fuel; advsied ATC; and diverted.