Never Again Online: The most exciting day

March 1, 2003

The most exciting day of my life was nearly my last.

Total engine failure in the clouds over mountainous terrain in a piston single probably ranks right up near the top of the general aviation pilot's worst-nightmare list. We know about it, train for it, even like to read about it. But, probably like you, I never thought it would happen to me.

It was the middle of April and we were straight and level at 12,000 feet over the mountains of western Montana — my first time at the controls of an airplane in instrument conditions. Though I was concerned, I was also thrilled to be doing something that so challenged the boundaries of physics and human physiology.

I had only three more hours of instrument time left to log before taking my instrument practical test, scheduled for 10 days after this long cross-country from Bozeman, Montana, to Seattle's Boeing Field/King County International Airport.

I interrupted my scan to glance several times at the exhaust gas temperature (EGT) gauge while making adjustments to the mixture. We were in a borrowed Piper Comanche 250, and I wanted to treat that big Lycoming with care. This was only my second time in a retractable-gear aircraft with oxygen, area navigation (RNAV), and GPS, and I felt a little overwhelmed and underqualified.

My instructor, Ben, was busy cross-checking a world aeronautical chart, his handheld GPS, and me when I noticed the engine suddenly went to a much lower rpm. For some reason, I looked first at the EGT, perhaps because I had injected it into my scan just seconds before. It was all the way down to zero. Simultaneously, Ben pulled carburetor heat. Nothing.

Things started happening quickly then. The manifold pressure gauge slacked off, the altimeter unwound, and the vertical speed indicator neared 1,000 fpm down.

I must admit I was pretty slow on the take. For the first few seconds, I wondered why the engine had slowed down so much. Even after we went through the troubleshooting checklist (carb heat on, mixture full rich, fuel pump on, switch tanks, check magnetos), it failed to respond.

Then I grabbed the throttle and pulled it all the way back. There was absolutely no change in the mechanical vibration and prop speed. I realized then that we didn't just have a reduction in power; there was no power.

I know that a dead engine windmills. But this Comanche had an aftermarket, three-blade prop that made it seem more like we had just lost half our power rather than all of it. The almost imperceptible change in visual propeller rotation and the nearly identical engine/airframe vibration had fooled me into thinking that there was still some life left when there was none at all. The increased drag of the big prop made it drop like a rock compared to the glide performance of the Cessna 172 I was used to.

I immediately went to best-glide speed and thought to myself, "This is it! This is how I'm going to die." Ben reached for the mic switch.

"Mayday, Mayday, Mayday! We have a total engine failure, descending through 11,000 feet."

Not recognizing the true engine-out situation in this airplane was my first rookie goof. Having less than up-to-the-minute situational awareness was the second. I knew we were somewhere east of Missoula, Montana, but wasn't sure how far. And from previous VFR trips there, the size and abruptness of the mountains to the east of the town were fresh in my mind.

We had been flying the minimum en route altitude (MEA) of 12,000 ft. Now, at 10,500 ft with a nearly 600-fpm descent rate, we could expect to see pine trees in about 50 seconds. Imagining the end so near briefly hampered my mental clarity. ATC snapped me right out of it.

"Say fuel remaining in time, and souls on board," said the controller.

"Two people on board, six hours fuel."

Fortunately for us, Ben knew exactly where we were. The engine had quit nine miles east of the Missoula airport. Using his GPS, he had me turn in the direction of the nearby interstate that led to Missoula. At least that would give us more clearance from the mountains.

During the gaps in radio transmissions that followed, Spokane Approach was on the landline to Missoula Tower alerting them of the engine out, getting the latest weather, and dispatching the emergency equipment.

"Would you like the VOR Charlie approach, or try to descend straight in?" The calm in the controller's voice surprised us both.

The chart binder was within my reach, so Ben took over the controls while I started haphazardly flipping through the charts looking for the correct approach plate. Ben asked Spokane for current visibility and weather into Missoula.

At 12,000 ft, we had been above the large, dark stratus layers that were causing snowstorms below, and we had been cruising in a high, thin mist layer before the engine quit. There had been no structural ice evident and the outside air temperature at that level was minus 2 degrees Fahrenheit.

Now, the clouds were getting darker and thicker on our descent. As reality sank in, we both realized that if we made it to the Missoula valley, and if we broke out of the clouds within gliding distance of the runway, there was no way we'd have time to fly an approach. We got back on the radio:

"We're not going to have time for that — can you just help us out with vectors?"

Thankfully, we were still high enough to be in range of radar. "Turn to heading 270 and you might pick up the airport here in another three miles."

The controller then proceeded to give us current weather in Missoula:

"Missoula weather is wind 160 at 10 kt, gusts 17. Visibility is three miles, light snow." We looked at each other silently. He continued, "Ceiling is 2,300 broken, 3,600 overcast. Temperature one, dew point minus two."

At this point a bit of a calm replaced the chaos. By now, I'd reached a pucker factor of about 10, so it was a relief to simply fly the airplane. Since Ben spoke GPS and I didn't, and he was also handling the radio, we agreed that I'd take the controls back. Hold a constant airspeed; that I can do.

Just to be sure, we went through the engine-out procedure again. Still nothing. And the carb heat had been on constantly now since Ben first pulled it.

The controller came back on: "Now turn heading 290. That'll take you right over the runway."

Only four and a half minutes and nearly 7,000 vertical feet after the engine had quit, we broke out of the clouds about 2,200 ft above the surface. The runway was visible forward and to the right, with snow showers just to our left reaching the ground. The sense of relief I felt at seeing the airport was like that of a kid getting rescued from the principal's office after a close case of mistaken identity.

Ben popped the door latches once we were on a high base leg and then took over the controls as I lowered the gear. We both had been comfortable with our altitude with distance remaining on base until that gear came down. Suddenly, the additional drag from the lowered gear made it obvious that we weren't going to make the runway after all.

At that moment, I remembered an earlier lesson where an instructor demonstrated the effect of feathering the prop on a windmilling engine. I pulled the prop control all the way back, and it felt like a 1,000-pound weight was just released from the bomb bay. The airplane floated up and lurched forward just enough to put us back on glidepath.

The controller cleared us to land on Runway 11 "with emergency vehicles standing by." We went through the prelanding checklist aloud, tried the throttle one more time, and then shut off the fuel and master switch. The landing was textbook.

After a short wait on the taxiway, we were towed to the FBO. The mechanic who checked out the airplane found a piece of ice that fell out of the intake plenum, and the entire engine area was dripping wet with condensation. After drying out the carburetor and air filter, he started the engine right up and put it through a vigorous test sequence. All was fine.

In the subsequent investigation, the FAA agreed with the local mechanic who had determined that we'd picked up carburetor ice. I find it curious, though, that 90 seconds before the engine quit, I had just switched tanks. I now know that it's very possible to pick up carb ice with no indication of structural ice, and I don't doubt that could have been the cause. But there was no telltale drop in manifold pressure, and the air temperature at that altitude was minus two degrees, much colder than the published cautionary range of 20 to 70 degrees F. Plus, fuel was switched to a new, full tank just shortly before the failure.

I can't help but wonder about the phenomenon of suspended moisture in the fuel or water in the line farther up from where I'd sumped on preflight. As for the carb ice, if you're going to take a windmilling engine on a rapid descent 7,000 feet through visible moisture, I bet you'd get carb ice, too. I guess we'll never really know which one it was.

In fact, after a few hours on the ground in Missoula and a thorough checkout of the aircraft, we climbed right back on those 250 horses and headed again to Seattle. Of course, we spent the first 15 minutes circling up to 14,000 feet directly over the airport checking everything checkable before continuing on.

Thankfully, the remainder of the trip was routine and I had lots of time to reflect on how many things worked out "just right" for us. To not only survive a total engine failure in the clouds over the mountains, but also to land on an airfield with no injuries or damage must have been a miracle.

I learned a lot that day. In particular, I learned to be a lot more aware of the dangers of carb ice and suspended moisture in fuel. Also, I was reminded of the need to stay situationally aware at all times. And finally, if ever in a similar circumstance, I think I'll wait to switch tanks until I'm over or near a runway, thank you very much.


Mark Borden, AOPA 3502776, is an instrument and multiengine flight instructor at FlightSafety International in Vero Beach, Florida. He has logged more than 1,000 hours in four and a half years of flying.


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Posted Tuesday, March 04, 2003 2:13:15 PM