Fellow Grumman Operators,
I own a 79 Tiger and use it to commute between NC and FL a couple of times a month and wanted to share a recent event that happened to me during a flight in Nov 2020.
My Tiger had completed its annual two months prior with no major issues and solid compressions. I have owned my Grumman for 5 years and have had the same mechanic doing my annuals and routine maintenance.
On the second leg of subject flight, I noticed my mixture lever required a leaner setting than normal to get the power and fuel burn I was accustomed to at that particular altitude. As the flight progressed, my RPM began to roll back so I turned to the nearest airfield which was 12nm away and traded airspeed for altitude. My engine then began running very rough so I went through my emergency procedures (switching mags, fuel pump on, carb heat, switching tanks, all had no effects). I then went full rich on my mixture and the engine quit. I leaned it to an extreme setting and it started back up. I limped it to Headland Airport under partial power and landed safely. Once on the deck, I ran it up and it would quit every time I went full rich.
I spent the night at the FBO and called my mechanic who instructed me to check airflow from the air intake to the carburetor. Fortunately there was a mechanic at the airfield the next morning and we began our investigation. When I looked at the air filter I read a placard that I had not given much attention too in the past that reads “WARNING Air Filter deterioration can cause engine power loss”. We cracked open the air filter canister and the filter looked to be in pretty bad shape. So we dropped the cowling, removed to entire air filter canister and discovered the air filter had indeed deteriorated and blocked airflow into the carburetor causing the engine to run rich and loose power. ****see pictures****** Of note: further examination of my air filter revealed that it was missing the “pie plates” which I understand is not that uncommon in older Grummans as they are sometimes discarded.
That morning I ordered the Challenger Air Filter Kit (P/N: CP-0711) from FletchAir which is a STC option for our aircraft. Instead of the original foam element, it is more like a filter that you would see in a car (framed filter). It cost $216 and can be cleaned and re-used 25 times (similar to a K&N filter).
Recommendations: 1) Roscoe has some very good videos on the air filters in our Grumman that I encourage everyone to view; 2) do a one time check of your existing filter to know the condition, type you have, and if it has all the required parts.
During this event, the symptoms were counterintuitive to me. Extreme lean settings started the engine again and allowed me to continue to an airport partial power. I was pretty sure when it quit that I would be doing a forced landing. I hope this helps. Please feel free to contact me if you want more details.
R/Wayne
bueno7557@gmail.com