Cessna 152
Flight Crew Private
Flight Crew Last 90 Days 13.6; Flight Crew Total 1010; Flight Crew Type 550
Human-Machine Interface; Troubleshooting; Confusion
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft; Human Factors
Upon takeoff from Runway 23 I had a gradual loss of engine power beginning at about 300 FT. My first thought was that I was experiencing fuel starvation; so I confirmed that the fuel cutoff valve was still in the open position and that the throttle and mixture were still full forward. I then executed a steep 180 degree turn to the left and landed on the flat ground in front of the new; still unopened ATC Tower; about 250 FT from Runway 23. The landing was uneventful; with no injuries to myself and no damage to the aircraft. The engine; which was still turning over slowly; died after the plane came to a stop. After about a minute; I attempted a restart; and the engine started immediately. I taxied across the flat ground until I could get onto Runway 23 to cross it to the taxiway; and then returned to the tie down area to determine what to do next.Prior to this incident I had flown in from my home base and parked the plane near the avionics shop for reinstallation of a radio that they had cleaned and retuned. I returned to the plane about an hour later. I did not sump the fuel tanks and lines at that time because I had done that prior to the inbound flight. I taxied to Runway 23 and did a run-up; which was normal. My engine analyzer showed normal temperatures during the run-up.After the incident; I did several run-ups to 2400 RPM; but there was no sign of what caused the engine loss. I checked under the cowling but everything was in place. I sumped the fuel tanks and lines; but found no contaminants. I then asked the Service Manager at the FBO to have a mechanic check the plane.After a few hours; the Service Manager told me that two mechanics with long experience in general aviation had given the plane a close inspection; including a compression check of the engine and a complete review of the fuel system. The only discrepancy they had found was a mud dauber nest well inside the fuel vent tube under the left wing. They cleared the obstruction and checked to see that the engine was running correctly.Once the plane was returned to me; I did a normal run-up and departed. The return flight was uneventful.A blockage of the vent tube would explain the gradual decrease in engine power; especially since the engine was drawing maximum fuel for takeoff at full throttle; mixture rich and the nose was at a steep angle upward. I thought that the vents in the fuel tank caps were supposed to ensure fuel flow if the vent tube became blocked; but this does not appear to be the case. They may have been designed only to keep the fuel tanks from crumbling if a vacuum built up inside. If so; a fuel vent tube blockage represents a single point of failure.I later looked for more information about mud daubers to see if they can build a nest in less than an hour and in what season they are active. I plan to get a pipe cleaner or wire to poke into the vent tube during preflight to check for blockage. I may also use some lightweight screening material to make a vent tube cover for while the plane is on the ground.I cannot say for certain why it came into my mind to return to the airfield for landing. I knew that I had a large expanse of flat open ground to my left as I was taking off; and I rolled out of the steep left turn after 180 degrees; not the 270 degrees I would have needed to make it to the runway. Although I did not consciously choose the open ground as a landing spot; I accepted it as a suitable place as I rolled out of the turn.I may have stalled the plane during the turn; because I found after I came out of the turn that I was in a dive; had pulled the yoke back to its rear stop; and had no elevator effectiveness. The ailerons; however; had remained effective enough for me to end the turn. While I was thinking about what to do to recover from the dive - keep the yoke back or push it forward - the elevator began to take effect and the plane leveled off. My decision to turn back was influenced in part by my reading a recommendation to perform a steep turn if turning back and by my having practiced steep turns because of this recommendation. I imagine that if I had practiced lowering the nose and looking ahead for a landing place; I might have done that.
When his engine started to lose power shortly after takeoff the pilot of a C-152 elected to attempt to turn back to the runway but was unable to do so and landed on flat ground still on the airport proper.