Yesterday's Unplanned Landing in Omaha (long)
Enroute from North Platte, Nebraska (KLBF) to Chicago Midway
(KMDW) yesterday afternoon (March 1), I made an unplanned landing in Omaha's
Eppley Airfield (KOMA). Everything happened so quickly that I didn't have a
chance to absorb it all until I woke up this morning. The following narrative
of yesterday's events is interspersed with paragraphs beginning with the word
Note containing my retrospective thoughts of today.
Around 4 pm (local time), I was cruising with one passenger in severe clear VFR at 11,000 feet eastbound across the midwest: almost 1.25 hours into the flight from KLBF with just under 2.0 hours to go until KMDW. Power was set at LOTWOTSOP: 2650 rpm and 13.2 gph, yielding TAS of 168 knots and given the tailwind, GS of roughly 180 knots. Fuel remaining at the destination was a comfortable 36 gallons.
Out of the corner of my eye I saw an annunciator light flickering orange: Oil, Oil, Oil. I looked at the Emax indicators in the upper corner of the map page on the MFD: all the readings were green except for Oil Pressure: 15 PSI! The analog gauge confirmed this depressing reading. But the engine was still humming along smoothly, and the Oil Temperature reading was normal for this flight at around 150 degrees F.
My immediate reaction was that the engine was about to fail. I waited a few seconds to see if the oil temperature would rise, or if fuel flow would drop, or if PSI would go back to 50, or if there would be an audible reaction from the engine. Nothing happened, but the oil pressure was still stuck at 15 PSI. Not good.
Note, I didn't go to the Emergency page of the MFD. Don't ask why, I just didn't. Instead, I thought of the emergency scenarios taught at the APS course, studying the Emax data for clues from the other indications (temperature, fuel flow, EGTs and CHTs). I instinctively felt that either I had an impeding engine failure which no amount of knob turning on the Emergency page of the MFD was going to solve, or it was a sensor problem that should be checked out on the ground as soon as possible.
Instead, I flipped the big knob on Garmin 2 to the Nearest section and looked at my closest choice: about 4 miles from Offutt Air Force Base (11,700 foot runway): I can deal with that. I hit Direct and called ATC to advise that I had an oil pressure problem and needed to land immediately. Because of my high cruising altitude I was with Minneapolis Center, not Approach Control.
Note, I did not yet switch the HSI to Garmin 2 and continued to let the autopilot fly the plane on GPSS off of Garmin 1, since the engine was still producing full power. I thought I'd wait a moment and first talk with ATC before turning and descending to Offutt.
ATC told me to descend to 5,000 feet and asked if I could accept Omaha Eppley, which he said was about 11 miles away. I flipped to the Nearest page on the MFD, and saw that it was choice number three; a quick look at the airport diagram page on the MFD confirmed that it was the large field with three big runways ahead and off to my left. I agreed to divert instead to Eppley, and ATC handed me off to Omaha Approach, which gave me a vector, read the ATIS and cleared me for a visual approach to runway 32R.
Note, I didn't bother setting up an instrument approach procedure, because the weather was so good, and decided to keep things simple and just fly the plane without dealing with the avionics any more than I had to.
I disconnected the autopilot, pulled the power lever back to below the detent (1,900 rpm), and began the descent at 850 fpm. Lo and behold, with that action the annunciator light went blank and the Oil Pressure gauge went back into the green at 52 PSI. Just then ATC asked if I was declaring an emergency, but since I was within easy gliding distance of several major airports I said no, and that perhaps I'd cruise a little first to see if I had a real, impeding engine failure or whether it was just a faulty sensor. Apparently not satisfied with that answer, ATC repeated the question: are you declaring an emergency? I said no emergency, but I'd like priority handling into KOMA. Omaha Approach canceled another plane's clearance to land, and handed me off to the tower.
Note, I was now fairly certain that the problem was sensor-related and not a real engine issue. But there was no question that a precautionary landing was in order, especially given the fact that it was already late afternoon and this was not a problem I wanted to see recur later in the flight at night.
The tower controller cleared me to land and authorized any necessary turns to reach the runway. I was now only five miles from the airport, at an altitude of roughly 5,000 feet AGL, descending at 150 KIAS with the engine running smoothly at 1,900 rpm. I cut back to idle power, increased the descent rate to 1,500 fpm, and did a few S-turns. One mile from the runway I pitched the nose up to reduce the airspeed to below 120 KIAS, put in one notch of flaps, and landed smoothly at 80 KIAS.
Note, when I began the descent I did not reduce to Best Glide Speed. Perhaps I should have, but the engine was still running smoothly and if fact I was able to cruise without losing altitude. Plus I was over a major city with four big to very large airports with the 20 mile gliding distance. Reasoning that as long as I still had power I could trade speed for distance, I decided to descend with some power and burn off the remaining excess speed only when I was very close to the airport.
After landing, I taxied to TacAir where the mechanics at the Garrett maintenance hanger towed the plane inside and uncowled it. Predictably, there was no unusual oil on the belly and no oil inside the cowl, and the dipstick showed 6 quarts. However, the oil pressure sensor at the bottom of the oil cooler showed a few drops of oil leaking out. They set up a hand pump (with its own gauge) to check the sensor, but it produced confirming, normal readings on both the Emax and analog gauges. They removed and cut open the oil filter, but no metal was found: apparently if the oil pressure drop was caused by a pump failure, the gears would have ground up and there would have been metal in the filter.
Quite fortunately I was able to reach my SC at Lincoln Park, and they were able to tell the mechanics in Omaha what to look for. Five stars to Bert Betzler, who was reached on his cell phone and kept calling back in for consultation and suggestions. For some bizarre FAA paperwork reason, the head mechanic at Garrett would not install a replacement sensor (since he didn't have any Cirrus manuals on hand), so they cleaned and reinstalled the original sensor; I did a run up and everything checked out fine. They added two quarts of oil (at least one quart was lost when the oil filter was replaced), topped off the fuel tanks, and we proceeded uneventfully to Chicago Midway three hours late.