Our piston airplane engines are extremely reliable — but fly enough and you may have an engine problem. Here are some lessons I’ve learned; I hope my experience will help you.
“ALMOST” TOTAL ENGINE FAILURE
Back in the early ‘90s I was instructing a Beech Bonanza pilot near Wichita, KS. During our preflight inspection we noted a small, rubber bushing was cracked on one of the fuel injector nozzles, on the right side of the engine. I remember advising the pilot to have it replaced as soon as possible to prevent rubbing of the injector line against its metal mounting bracket.
During the lesson the student and I noticed a “fuel smell” during takeoff and landing practice at a remote airfield. We even shut down and looked at the engine. Doing so managed to convince us that we were “smelling things,” so we launched into instrument meteorological conditions (IMC) back to Jabara Airport, northeast of Wichita. While at 4000 feet on vectors for the VOR approach the power suddenly dropped — dramatically. Strangely, the engine still ran smoothly, but the airplane began to descend. I took the controls and immediately began a standard-rate turn toward the nearby non-directional beacon (NDB) at Newton, KS. I held altitude in the turn, slowing toward best glide speed, and keyed the mike: “Wichita approach, Bonanza 12345 has an engine failure, I need a vector to Newton.” In the pre-GPS airplane I asked for the distance to Newton, and the distance to Jabara. Both were about seven miles, but toward Jabara I’d have a slight tailwind. Jabara it was. I got the vector and found we could barely hold altitude at full throttle, full prop, and best glide speed.
I handed control back to my student and assessed the situation. We had an “almost” total engine failure, but we had altitude, were under control, and were headed toward the nearest airport. Time to troubleshoot. I talked my student through the checklist we’d reviewed all week in class and in the simulator:
- Fuel tank: select other main tank. (This did no good.)
- Fuel pump: check LOW (no effect), HIGH (made the engine stumble even more), then OFF since it didn’t fix the problem,
- Fuel mixture: FULL RICH. (The fuel flow was indicating well above redline.) Okay, then LEAN for smoothness. (No luck there either before power began to drop further.) We put it back to FULL RICH.
- Ignition: check each magneto independently… (with no success). We put it back on BOTH.
- Air: The alternate air system in the Bonanza should have worked automatically but has a manual backup. (Pulling the manual alternate air control had no effect.)
OUT OF OPTIONS
There was nothing left but to land the airplane. Wichita Approach directed a descent to about 1000 above ground level, hoping to get us into visual conditions. “We’ll just stay at 4000 until we’re closer to the field,” I replied after a quick mental check of gliding distance. The engine held, barely, and we got within about three miles of the airport (according to ATC) before accepting the descent, breaking out of the cloud deck, and making an uneventful landing (with very little throttle reduction required after extending the landing gear and flaps).
Taxiing in, the fuel smell returned to the cabin. We quickly shut down and got out; blue fuel stains (a very handy indicator) extended from the rear of the engine compartment to the very tail on the right side of the fuselage.
LESSONS LEARNED
- Fix discrepancies found during preflight inspection before the next flight. This is especially true for anything found “wrong” in the engine compartment. That little rubber bushing not only prevents rubbing of the fuel line, as we learned, but it also damps out vibration of the injector line. In flight, as the last of the bushing blew away, the fuel line shook right out of the injector nozzle — it was spraying fuel all over the engine.
- Pay attention to unusual smells in the cockpit. The fuel odor we noticed resulted from fuel spray entering a cabin air vent. A strong fuel smell warns of potential failure.
- Know where you are at all times. It’s easier with GPS, but use every means available to tell where you are, and where you will go if you have a problem. Be ready to turn to the nearest airport and ask ATC for help at the first sign of trouble. Be ready to turn down an ATC request (like the descent) if you feel it will compromise factors still in your favor.
- Know your emergency procedures. We could easily have become disoriented and lost control in the clouds if we’d not been familiar enough with our procedures to run them while flying the airplane.
- Know your systems. Complete familiarity with the design of the airplane’s fuel and engine systems made it very easy to troubleshoot the problem. The biggest anomaly, the above-redline fuel flow, came from loss of back-pressure in the fuel lines and the resulting free-wheeling of the fuel flow transducer. Knowing this could have pointed more directly to a fuel leak as the problem — with that knowledge I probably would have put the airplane down in a field instead of trying to make it to a runway. (Recall that we were spraying fuel all over our engine.)
- Use your resources. The student, Air Traffic Control, and I made a pretty good team during this event. It would have been significantly harder, and potentially much less successful, if any one of the three had not been in the loop.
- Don’t underestimate luck. I guess the engine didn’t burn because there was too much air in the compartment to support a fire. I’m really surprised it didn’t light up as we taxied in.
BOTTOM LINE: Engine emergencies usually aren’t the all-or-nothing, glide to a landing affair we learn during primary training. It takes system knowledge, practiced procedure, command authority, and a little bit of luck to make it when things go wrong.