Narrative:

This flight was to be my second solo cross country for my asel ppl. My instructor had signed off on everything in my logbook and had the current briefing from both airfields. I was about 50 nm into my flight; switching on the 2nd communication to listen to the ASOS at ZZZ; when I heard a pop in the engine and had a significant RPM drop. I scanned all my instruments and didn't notice anything critical other than a loss of RPM. I decided not to add power as the engine was running very rough and I didn't want to exacerbate any problems. I scanned my efb for the nearest airport and saw that I was about 23 nm from ZZZ. I trimmed for best glide speed and started trying to troubleshoot the problem. I thought maybe I had fouled the plugs; or had a mag fail. I cycled the mags and went back to both with no improvement. I then pulled in the carb heat to check for carb ice; but had no improvement. The engine was still running but I was losing RPM quickly. I immediately started for a field to set the plane down in and squawked 7700. I looked at my emergency checklist one more time; and decided to add power. I enriched the mixture and pushed in the throttle to try and re-gain some of my lost altitude. The engine did restore to the point of being able to maintain 3;000 feet. I then re-squawked 1200. I quickly looked at my efb and saw that ZZZ1 was closer by about 5 nm and I diverted there. I called the CTAF at ZZZ1 and had a short approach landing. Once on the ground; I removed the cowling and discovered that an exhaust stack had split into the muffler. I contacted my local a&P and the parts are now ordered and will be installed shortly.

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Original NASA ASRS Text

Title: Cessna 172 student pilot reported the failure of the engine exhaust stack resulting in reduced engine performance; and a subsequent diversion to the nearest suitable airport.

Narrative: This flight was to be my second solo cross country for my ASEL PPL. My instructor had signed off on everything in my logbook and had the current briefing from both airfields. I was about 50 nm into my flight; switching on the 2nd COM to listen to the ASOS at ZZZ; when I heard a pop in the engine and had a significant RPM drop. I scanned all my instruments and didn't notice anything critical other than a loss of RPM. I decided not to add power as the engine was running very rough and I didn't want to exacerbate any problems. I scanned my EFB for the nearest airport and saw that I was about 23 nm from ZZZ. I trimmed for best glide speed and started trying to troubleshoot the problem. I thought maybe I had fouled the plugs; or had a mag fail. I cycled the mags and went back to both with no improvement. I then pulled in the carb heat to check for carb ice; but had no improvement. The engine was still running but I was losing RPM quickly. I immediately started for a field to set the plane down in and squawked 7700. I looked at my emergency checklist one more time; and decided to add power. I enriched the mixture and pushed in the throttle to try and re-gain some of my lost altitude. The engine did restore to the point of being able to maintain 3;000 feet. I then re-squawked 1200. I quickly looked at my EFB and saw that ZZZ1 was closer by about 5 nm and I diverted there. I called the CTAF at ZZZ1 and had a short approach landing. Once on the ground; I removed the cowling and discovered that an exhaust stack had split into the muffler. I contacted my local A&P and the parts are now ordered and will be installed shortly.

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.