Sunday, June 1, 2008
Tight Is Right
Inadequate preflights can have dire consequences
|It has been said that oil is the blood of an engine. If the oil is old and tired, contains foreign materials or flows at the wrong pressure, the engine’s optimum life span can be threatened. All pilots should know enough to check oil quality, as well as quantity, during preflight inspection. A quick peek at oil quantity marks on the dipstick isn’t enough. During preflight, you need to determine whether the oil seems suspiciously gritty, displays an unusual color or sheen, seems too thin or too thick for the ambient temperature, or has a “burnt” aroma. Inspect inside the cowling and on the ground under the engine for signs of oil leaks.|
• A Cessna 182C was substantially damaged when it collided with terrain while maneuvering for a precautionary landing at the Carson Field Airstrip in Marion, Mont. The certificated commercial pilot and all four passengers were killed. Day/VFR conditions prevailed for the skydiving flight. The flight took off about five minutes before the accident.
A witness saw the pilot perform a preflight inspection prior to departing on the first flight of the day. This included checking the oil and fuel levels. The pilot pulled out and then checked the dipstick, but the witness didn’t see him remove the oil filler cap or add any oil to the airplane. The airplane’s engine had separate openings for adding oil and checking oil level.
Another witness saw the airplane take off heading north, and a minute or so later, she heard the sound of an airplane descending. The witness reported, “I looked up to see him approaching [runway 32] on his base leg, too low to make a safe turn to final. I continued to watch him as the aircraft rocked slightly, then appeared to take a sharp left turn, causing the nose to dive downward.” The witness said the left wing slightly dipped, and the airplane crashed. The commercial pilot had accumulated a total of 508.5 flight hours with 46 hours in make and model.
An examination of the engine revealed that the oil filler cap was detached from the oil filler tube. It was hanging by its chain between cylinders four and six. The cap wasn’t damaged.
A weight and balance calculation indicated that the airplane was approximately 165 pounds over its max gross weight, and the center of gravity was at or near the aft limit at the time of the accident.
The NTSB reported that because the oil filler cap wasn’t secured to the filler tube, it’s reasonable to expect that oil would have escaped the engine and blown back over the pilot’s windscreen, thereby obstructing his vision. The obstructed windscreen, coupled with the airplane’s excess gross takeoff weight, would probably explain the pilot’s loss of control.
The NTSB determined that the probable cause was the pilot’s failure to maintain aircraft control while maneuvering to reverse direction. Factors included the airplane exceeding its max gross takeoff weight, the improper preflight in which the pilot failed to secure the oil cap, the low altitude and an obstructed windshield.
• A Piper PA28R-201T, which originated from Watkins, Colo., was destroyed when it struck a fence during a forced landing near Hartsel, Colo. The pilot and passenger escaped injury. Dusk/VFR conditions prevailed.
The pilot told investigators that shortly after sunset, he was in cruise flight when oil began to appear on the windshield. He pulled back the throttle to idle, then slowly added some power. He didn’t notice “any substantial response” from the engine, but did observe more oil on the windshield. He slowed the airplane to 100 knots, then determined that the nearest airport, Buena Vista, was about 21 miles away. He didn’t think he could make it, and elected to land on a dirt road. He said approach speed was 10 knots higher than normal “to avoid obstructions.” He realized he was going too fast and would overshoot the road, so he turned to an adjoining field. He maneuvered the airplane over a herd of buffalo and touched down. During the landing roll, the airplane struck a fence, rupturing the right-wing fuel tank. Fire department personnel later discovered the oil filler cap was missing.
The airplane was moved to a facility in Greeley, Colo. The oil access panel on the cowling was opened and the dipstick was removed. It registered three quarts of oil. The pilot said he “thoroughly preflighted the airplane” and checked the oil. The oil level was “about one-third down from the top” (about six quarts; capacity is eight quarts). The pilot said the oil filler cap, which was next to and behind the dipstick, “was easily visible and in place,” but he didn’t physically check it for security. The oil filler cap was eventually located in a recess atop the right bank of cylinders where it had fallen.
The probable cause was determined to be the misjudgment of the proper touchdown point on the dirt road due to excessive airspeed and failure to deploy flaps. Other factors included the partial loss of engine lubricating oil, which resulted from the oil filler cap departing after an unknown person failed to properly secure it, and an inadequate preflight inspection.
Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other NTSB news. To subscribe, write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.