ILAFFT

WHEN PAY­ING AT­TEN­TION PAYS OFF

Flying - - DEPARTMENTS - By Tom Haak

Dead al­ter­na­tor on the good en­gine

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 dataen­try 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.

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 high­rpm 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 glare shield. In the mean­time, when fly­ing a Navajo in the fu­ture, I re­solved to keep an eye on those eye­brow panel lights.

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