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.|
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. And, for security, check whatever parts of the oil system may be visible, including hoses, the oil cooler and the filler pipe. To avoid having your lengthy preflight become a waste of time that creates, rather than prevents, a hazardous condition, you also need to make sure that you’ve secured whatever you opened for inspection. Take, for example, the following accidents.
• A Cessna 150M with a student pilot on board was substantially damaged during a forced landing attempt. The flight originated at Grand Ledge, Mich., and was en route to Mount Pleasant, Mich., in day/VFR conditions.
In a written statement to investigators, the (uninjured) student reported being approximately four miles from Mount Pleasant Municipal Airport when the airplane “started to shake violently and the engine rpm dropped to 1,500.” The pilot moved the mixture control to rich, turned on the carburetor heat and performed his checks, but “couldn’t find anything wrong.” He contacted Saginaw Approach and informed them that the airplane “was having engine trouble and was losing altitude.” The pilot also told the controller that he thought he “could make the field” and that he “had the airport in sight.” The pilot changed radio frequencies to Mount Pleasant Unicom and informed the airport traffic that he’d be making an emergency landing on runway 09. As the pilot turned toward the airport, the engine rpm dropped to 1,000, and the airplane began to lose altitude rapidly. The pilot performed a forced landing on the airport grounds, 400 feet short of the runway 09 threshold. When the nosewheel touched down in the snow-covered ground, the airplane “stopped suddenly and pitched forward on its nose.”
An FAA inspector reported that oil was covering the engine cowling. Further examination of the engine revealed that the connecting rod to the number-one cylinder had failed due to oil starvation. The oil cap to the crankcase was found to be loose. Oil was observed covering the left-side engine components in the area of the oil filler neck.
The NTSB determined that the probable cause was the student’s inadequate preflight and a loose oil filler cap, which resulted in oil starvation and failure of the number-one cylinder connecting rod. The pilot had 34 hours with 32 in type.
• A Cessna T210L was destroyed when it impacted the ground near Richard Lloyd Jones Jr. Airport in Tulsa, Okla. Two passengers and the instrument-rated private pilot were fatally injured. Day/visual meteorological conditions prevailed for the cross-country personal flight. The flight’s destination was Joplin, Mo.
After taking off from runway 19R, the pilot was instructed to turn to a 100-degree heading. About a minute and 40 seconds later, the pilot reported that he had oil on the windshield and wanted to return to the airport. A pilot who was taking off behind the aircraft said that it leveled off at 300 feet, slowed down and made a right turn back toward the airport. He said that the T210L started the right turn to the north and “appeared to be moving very slowly.” As the airplane turned through a heading of about 300 degrees, the right wing dropped, the airplane rotated three-quarters of a turn to the right and it struck the ground. A fire broke out.
The pilot had approximately 1,474 hours of flight experience with 794 hours in the accident airplane.
The engine’s oil filler neck was found without its cap, which was attached to the neck by a chain and was found undamaged between two of the engine’s cylinders. Windshield pieces found beyond the fire zone were coated with oil. According to the engine manufacturer, the engine could probably run for 15 to 25 minutes without a cap on the filler neck.
The probable cause was determined to be the pilot’s inadequate preflight inspection and his failure to secure the oil cap. This resulted in oil leakage on the windscreen, which obstructed his vision and led to his failure to maintain adequate airspeed.