Never Again

Turbo-torch

July 1, 2010

As we climbed up through 5,000 feet, the airplane began to whisper. Ever so faintly, its breath in my ear, it was trying to tell me something. I’d been flying this airplane for just one year, but with almost 700 hours in other turbocharged Cessnas, I was confident that I knew it well. As the airplane continued the climb, the throttle position seemed out of place. For some reason it needed to be shoved forward a good deal more than normal.

Something wasn’t right and my senses were elevated. I listened intently, looked at everything, sniffed for acrid odors. Nothing. The temps looked good and the climb was smooth in near-perfect VFR weather. So I pushed on. It was February and we were about to cross the Southwest on a multiday adventure from Southern California to Central Florida.

“Land me,” the airplane seemed to whisper, but I ignored it. The gauges were in the green, the engine ran powerfully, and there were no outward signs of trouble. Heck, I said to myself, this airplane has just come out of maintenance with new oil, a fresh exhaust, and all fluids checked by mechanics I’d trusted for a decade. But why the unusual throttle position?

I leveled off at 11,500 feet with the autopilot comfortably in command as we cleared the mountainous terrain that divides this coastal area from the broad desert. I had planned to climb to 17,500 to take advantage of winter’s westerly winds, but the throttle was already firewalled, and I was getting increasingly concerned. My passenger, Mike, and I talked as the miles slid beneath us. We were in the Cessna TR182 I had purchased the previous spring. My last airplane was a Cessna T210, and the four-seat TR182’s performance was similar. During my initial training on the TR182, however, I learned that it’s not a T210. It is carbureted instead of fuel-injected and it’s turbonormalized. The turbo is controlled with manual linkage that is not altitude compensating like the T-210, and a fancy set of cams limit the turbo to sea-level manifold pressure— and no more.

I considered all this as we clipped along at 180 knots over the ground, diagramming in my head the business end of the throttle cable. I knew it managed multiple features on the carburetor and the turbo’s wastegate. But something was happening under the cowl that wasn’t right. Where was the problem? Nothing made sense.

“Land me now!” the airplane seemed to say more insistently. I stayed the course, and proceeded east. Suddenly the carbon monoxide alarm sounded with a series of piercing chirps. The Home Depot unit I’d tucked under the front passenger seat snapped us to attention. The airplane was talking louder now, and I felt a shot of adrenaline. I had to take action.

So I opened a window. If there was a CO problem, we should get clean air in the cockpit right away and see if would silence the alarm. If not, perhaps there was a problem with the sensor, or its batteries. With a window partially open, the alarm quit. But as soon as the window was closed again, the device chirped non-stop. The problem was carbon monoxide and the alarm was for real.

Mike’s a CFII, but I was pilot in command, and I had some decisions to make.

It was time, perhaps past time, to land the airplane and determine the reason for the unusual throttle position and carbon monoxide leak.

I reduced the power and began a steady descent. We were just west of the Colorado River and Yuma, Arizona, lay ahead, easily within gliding distance. I knew it was a joint-use airport with general aviation, airlines, and military aircraft. Busy place, but I needed to land now, find a mechanic, and answer the aircraft’s pleas for attention.

Los Angeles Center had been providing VFR flight following. When we switched to Yuma Approach and then Yuma Tower, we advised the controllers that we were making a precautionary landing. The controllers were calm and professional as you’d expect them to be, and we never declared an emergency. We made an uneventful approach and landing and taxied to a maintenance facility. All seemed perfectly normal, and as I shut down, and I began to question why the heck I’d landed with five hours of fuel remaining, and thousands of miles to go before reaching Florida. Had I overreacted? Was this stop really necessary, or was I just wasting time and a tailwind?

As I stepped out of the airplane, however, those thoughts disappeared immediately, and I suddenly appreciated the communiqué the airplane had been trying to deliver. On the left side of the cowling, the paint was gone from an area about the size of my hand. Beneath it, the aluminum skin was badly blistered and nearly melted from excessive heat.

We removed the cowl and the source of the problem quickly became obvious. An exhaust coupling had failed. Also known as a V-band, the linkage secures the exhaust system to the output side of the turbocharger. When it failed, a small gap between the turbocharger and exhaust pipe opened up and allowed superheated exhaust gasses—upwards of 1,600 degrees Fahrenheit—to escape and torch the aluminum cowl just an inch or so away.

Our near-disaster had nothing to do with the throttle cable or its misbehavior. The culprit V-band had been deemed fit to reinstall after exhaust work, and when it failed, the wastegate needed to be opened far wider than normal to make up for boost lost to the broken connection. The V-band, which resembles a hose clamp, is a critical part that must withstand extreme thermal cycles. Without it, hot exhaust was well on its way to burning through the aluminum cowling, and the superheated gas created a serious risk of an in-flight engine fire.

In flying, all pilots must have a certain degree of confidence in their aircraft. But how much you trust the airplane, how well you know it mechanically, and how sensitive you become to its behavior varies widely. For me, I learned that ignoring an airplane’s subtle messages that something isn’t right could prove disastrous. When the airplane speaks, I listen.

Lou Frank, AOPA 860808, is an instrument-rated commercial pilot with about 3,000 flight hours. He has been flying 25 years, lives in San Diego, and has flown throughout the United States and Mexico.