Oil is the lifeblood of your aircraft engine or engines. Despite what a few vendors will try to show you about additives, without engine oil, most aircraft engines will self-destruct quite quickly. This is one of the reasons why we are all trained to check the oil during our preflight and oil temperature and pressure soon after engine start. The safety of our flight can depend on how well we do our job when we make sure there is enough oil in the engine.
CASE IN POINT. The owner of a Bonanza had checked the oil in his airplane, and had found the level to be correct and acceptable. By “correct and acceptable,” we mean that the sump held 10 quarts, and the engine showed 10 quarts on the dipstick. The owner then performed his normal preflight, jumped into the airplane, and set course for his destination, some three and a half hours away.
YOU KNOW THE FEELING WHEN YOU ARE UP IN THE AIR. It feels really great to be flying, and to be headed toward your destination. You scan the instruments, and everything looks good. You get comfortable in the flight, since everything in the previous umpteen hundred or thousands of hours has gone well. You’ve had some minor problems, but nothing your skills and training as a pilot didn’t allow you to handle.
The engine is running well, the cylinder head temperatures are good, the RPMs are good, and then you look down at the oil temperature and pressure. In this case, the oil temperature seemed to be running higher than what he expected it to, but the pressure was okay. A few minutes later, our pilot looked down at his instruments again, and was very surprised at what he saw. Oil temperature had dropped, and the oil pressure had gone to 0 psi — pegging the bottom of the gauge!
THE PILOT DID THE RIGHT THING IN THIS CASE. He was flying in daylight, and identified an acceptable landing area. He reduced power on the engine to idle, and started circling down to his selected off-airport landing area. Due to his skills, the daylight hours, and a little luck, the pilot made a safe and uneventful landing.
ON REMOVING THE DIPSTICK, THE PILOT DID A DOUBLE-TAKE. He thought he might have an instrument problem, but both oil instruments at the same time were too much, so he made a precautionary landing. It’s a good thing he did — the dipstick didn’t have a drop of oil showing on it! MANY A PILOT MAY THINK, “Well, the dipstick only goes to around 4 quarts … maybe there was some oil under it.” Maybe there was. Then again, maybe not.
After calling local law enforcement and Flight Service to advise them of his difficulty, the pilot looked further. In this examination, he found a significant streamer of oil down the belly of the fuselage. Tracking the oil back, he located the problem — the oil line to the Hobbs meter had broken. Over the course of his long flight, this leak had managed to bleed all the oil out of his airplane.
PREFLIGHT MEANS PREFLIGHT! When you preflight the plane, do you look in every available opening, or do you look in what is convenient? The Hobbs line had been leaking before, but the pilot had missed the oil stain on the belly because it hadn’t been cleaned in a while, and was pretty dirty! More important, the pilot only lifted the small cover over the dipstick to check the oil. He didn’t open up the tops of the cowling to look for problems.
THE MOONS AND STARS LINED UP PROPERLY IN THIS CASE, AND OUR PILOT WAS ABLE TO MAKE A SAFE LANDING. The airplane wasn’t damaged, so some might question why this is a big deal. All you need to do is change the situation a little, and this becomes a HUGE PROBLEM…
- The flight took place at night? How successful would you be finding a safe off airport landing site at night?
- The flight was in IFR conditions? Same thing holds true — when you circle down after the engine fails, will you break out in the proper orientation, or become a new statistic on CFIT — Controlled Flight Into Terrain?
- A bigger leak had been present? If the oil pressure drops to zero and you don’t notice it in time, your first indications might be a runaway prop as the governor goes dry. Once the engine is out of oil, the chances are good that it will seize and seize quickly, which leaves you with a stuck prop, which translates to less glide performance than one that is windmilling.
TAKE THE TIME TO DO A PROPER PREFLIGHT. The preflight is your insurance that your flights will continue in a safe and uneventful manner. Take this opportunity to check your preflight actions. If you find yourself taking some shortcuts, remember this example and then ask yourself who will protect you if your preflight isn’t adequate. We both know the answer.