Page 22 - Volume 11 Number 10

connected to the sleeve and the other available to hook to the exhaust stub lip. Easy peasy, right?
The early model 200 landed and was parked for the day at an airport in Kentucky that had a King Air maintenance facility associated with the FBO. It was a windy, cold and rainy day, so the pilot installed the homemade restraints. The temperature kept falling as hours passed until the rain had turned to sleet. When the passengers arrived later in the day, the pilot found a major starting problem – no N1 rotation when he activated the start switch. The large drop in voltage led him to believe that the starter was receiving power, but the compressor shaft never showed any speed. Into the maintenance facility he goes, reports the problem, and is advised that they will pull the plane into the shop. “We had this same thing happen about a month ago on another 200. The number two bearing – the forward support of the compressor shaft – had seized and we had to replace that bearing. I bet yours is the same. Probably a bad batch of bearings.”
The passengers were put on another plane and into the shop our 200 goes. The shop personnel start by removing the starter-generator and inserting a socket wrench into the accessory case splines, trying to rotate the compressor by hand. “Yep, she’s frozen
solid.” The pilot authorized the shop to proceed to replace the suspected seized bearing.
This shop, being well-versed on King Airs, had the cowling off and the power section separated from the compressor section at the C Flange in a jiffy, to gain access to the bearing. Wait! What is this we see?!
We see the bottom quarter or so of the Compressor Turbine (CT) solidly encased in a hunk of ice. What the ...?!
Seems like the rain and wind angle had conspired to blow lots of water into the engine via the uncovered exhaust stacks. As the temperature dropped, the water inside of the engine had now frozen, locking the CT in its icy grip. This was the reason for the lack of rotation; the bearing was fine.
I had – and still have – a question that has never been satisfactorily answered. PT6 engines have two drains, forward and aft, at the bottom of the compressor case. These are designed to spring open when the pressure equalizes on both sides of the drain but they close when the compressor’s rotation creates higher internal pressure, to avoid an undesirable P3 leak. Their primary purpose is to provide an exit path for fuel following a no-light-off starting attempt. Why didn’t they permit the water to drain from the case in this situation?
Were they installed incorrectly? Were they defective? Or did the ice freeze over them rapidly enough that they became plugged before much water could exit? I don’t think we will ever know the exact reason but we do know that this incident did indeed happen and led to unnecessary delay and expense.
Bottom line? Do not use a simple bungee cord setup under these conditions. Cover up those exhaust stubs with the propeller restraint when it’s rainy and cold.
My last comment has to do with storing the restraints when not in use. There may be room in a wing locker – if you have them – simply toss them into the locker along with the pitot tube covers, engine intake plugs and heat exchanger inlet plugs. But if no locker is available or if it is full of baggage, golf clubs or skis, now is the time to fit all the items into the small canvas bag that Beech provides with the new airplane. That can be a tight fit.
20 • KING AIR MAGAZINE
OCTOBER 2017