By the fall of 1978 I’d worked for Piper Aircraft in Lakeland, Florida, for three years. I was the assistant chief engineer-technical, which meant I had the people in the structures, aerodynamics, power plants, systems, electrical/avionics and flight-test groups all working for me. At the time, we were working extremely hard to certify the new Piper Cheyenne III. I was, however, also responsible for support of the twin-engine Navajo Chieftain assembled at Lakeland.
Piper’s new manufacturing facility was located on the Lakeland airport, a place with three paved runways, the longest of which was Runway 9/27 at about 5,000 feet. The uncontrolled airport was home to more than 100 private airplanes and, of course, depended on pilots to report their intentions using the unicom frequency.
As an engineering test pilot, I flew a number of single-engine cooling climbs in the Navajo Chieftain to solve some operational problems. The FAA demanded that twin-engine airplanes be able to climb to 5,000 feet on one engine without exceeding engine temperature limits on the operating engine. The Chieftain we flew was equipped with thermocouples on each cylinder head on the right engine that allowed us to individually scan important data and send it to a box in the flight-test observer’s lap. During our tests, we would shut down and feather the left engine, close its cowl flap and commence the climb on the right engine while it ran at full throttle. The observer’s job was to check the thermocoupled cylinder heads every two minutes and record the temps on his data sheet. The data would be correlated with OAT at various altitudes and used on future designs to fix problems long before the aircraft were ever delivered to customers. These test flights had always been pretty much problem free.
One sunny Saturday morning, my counterpart Frank, the assistant chief engineer-programs, and I were scheduled to fly one of these tests in the Chieftain. Despite the hard work, we both still loved flying and were intent on keeping up our proficiency, so we didn’t feel too bad helping the flight-test group out on a weekend for these more mundane tests.
I flew left seat, with Frank sitting in the right seat, preparing to handle the data scans and entry. Despite the drudgery of his right-seat data-entry job that day, Frank was also a highly experienced former Air Force pilot and well qualified in the Chieftain himself.
The temperature on the ground at Lakeland was a balmy 80 degrees, with a light wind from the east. We took off normally and climbed to 1,000 feet, where I shut down the left engine before we began the test. We climbed due south from Lakeland at the usual 125 feet per minute, with the airplane’s CG ballasted to bring us to forward at max gross weight. We droned on for some time, with Frank dutifully recording performance data while I kept an eye out for traffic.
Shortly after we topped 4,000 feet, I noticed the VOR needle starting to act strangely. It was lazily swinging back and forth, somewhat like it does when you get too far from the VOR station. Except today, we were not very far from the station. I tried to think of what might be going on and decided to call back to home base on unicom. My calls brought no response. Only then did my expanded scan of the cockpit note the yellow “alternator inop” light illuminated for the right alternator. The battery was also nearly dead. Doggone it. On the Chieftain, those alternator lights were located on the eyebrow panel over the windshield and not a normal part of my scan.
I usually checked them after engine start and then again before takeoff, but honestly, not very often during flight. What was worse, the bright sunshine outside made the lights even more difficult to see.
So here we were, the left engine shut down, with the propeller feathered and the good engine running but producing no electricity. We, of course, discontinued the test climb, leveled off and then began a gentle turn back north toward Lakeland.
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With a dead battery, we both knew there would be no way to restart the left engine. And the airplane was not equipped with unfeathering accumulators. That pretty much meant a single-engine approach and landing was in store for us. At least we were still at 4,300 feet. Call me silly, but despite my experience I really did not like single-engine landings if they could be avoided. Sure, a lot of them have been made successfully, including by me, and the funny thing was they were among my smoothest landings ever. I still didn’t like them because you were just so committed once on final approach, left to the mercy of someone beyond your control possibly cluttering up the runway at the last minute. We had no radios to tell anyone what was happening or our plans for landing. We also both knew that even if we needed it, a single-engine go-around in a Chieftain near forward gross weight was not a good option.
With my mind racing through our alternatives, I remembered something my chief power-plants engineer had said in a status meeting. He had talked about how we’d determine the optimum prop feather angle for the Cheyenne II in upcoming flight tests. He explained that the angle needed to be optimized for the speed range at which the airplane would normally be operating during any single-engine operations. He said the feathered props wouldn’t remain in the feathered position if the speed range was drastically exceeded.
We formulated a plan. We’d sacrifice 2,300 feet of altitude to see if the speed and the airflow as we dived might make the engine turn over fast enough to allow it to start. If it worked, we’d make a normal approach and landing. If it didn’t, we’d abandon the dive at 2,000 feet and commit to a single-engine approach and landing.
With the prop lever pushed one-third of the way toward the high-rpm position, we commenced our dive. At 185 mph, the prop twitched just a bit. At 190 mph, it turned completely through a couple of times. At 195 mph, the prop started turning. A rotating propeller meant the engine had oil pressure. As soon as that oil pressure hit the propeller, it came out of feather. I switched on the mags as I gradually brought the mixture control forward. The EGT gauge confirmed we now had a running engine and electricity.
Shortly thereafter, I flew a normal approach and landing, happy we’d avoided a no-radio, single-engine landing. The flight also reinforced in me the need to pay attention when experts are speaking about related flying topics, as I did during the discussion on the Cheyenne II prop-feathering issue, because it really paid off. I also learned there was a better place in the cockpit for those alternator inop lights. On the Cheyenne III, we put them in plain view on the annunciator panel just below the glareshield. In the meantime, when flying a Navajo in the future, I resolved to keep an eye on those eyebrow panel lights.