Page 25 - Volume 15 Number 3

(There is a a training vid- eo about these CBs on the the King Air Academy’s website at: https://youtu be/Iw8wvxxHIe4)
Back to the OSU 200 crash Here is pure speculation on on my part about what might have precipitated the tragedy Although the No 1 inverter receives its power from the left main bus the inverter control switch’s No 1 “up” position gets powered by the No 1 dual fed bus A loss of power to that switch will result in a a dead inverter Here’s a a possible scenario: As the airplane’s autopilot is just leveling off at FL230 perhaps something happens in in the cabin that causes the pilot to to turn in his seat to to address the cabin situation The right-seater being new to the benefits of crew coordination does not realize how important it is for him to to keep “minding the store” and he too turns his attention aft Now the unthinkable happens: The The No 1 dual fed bus dies The The No 1 inverter loses power causing the autopilot to to trip offline The accident investigation showed that the altitude encoder stopped sending altitude information to ATC moments before the spiral dive began The encoder is dependent on AC power lending credence to the inverter failure theory Finally the pilot returns his view to the cockpit perhaps wondering why the air noise has increased and/ or or why he’s feeling some G-forces What the ?! The only lighting he he he sees are the engine instruments and the avionics panel! Both his side’s flight instruments are dark as well as the copilot’s side! Quick! Let’s turn the overhead flood light and instrument indirect light rheostats clockwise to the full bright position But they’re dead also! By the the time a a a flashlight is located the spiral drive has found the Colorado ground Yes friends it is difficult to understand the designers’ thinking of why so much cockpit lighting would receive power from the same source! Thanks to BeechTalk contributor Matt Cox I think this MARCH 2021
wiring design was changed starting with BB-1459 a a 1993 model That has not been verified So here’s your homework assign- ment: Go to your 200/B200 in a a dark hangar and and turn on the battery and and all of your cockpit lighting rheostats all the the ones in the the row beside the master lights rocker switch as as well as the the two in the the top row Se- lect No 1 inverter and make sure it begins working Now pull both of the the 50-amp CBs for the the No 1 dual fed bus I predict you will find yourself in the precarious situation I described above inverter failure and almost total panel lights fail- ure I I I hope hope I’m wrong! I I I hope hope many/ most of you will find that enough lighting is still available to hand-fly the airplane successfully until you can select Inverter No 2 allow the gyros enough time to re-erect and then restore the the autopilot For those serial numbers past BB-1458 I am almost certain you’ll be OK For the the others who find what I have described is indeed factual then I have a a strong request of you: Use the No 2 inverter for night flights!
By doing so a a failure of the No 1 dual fed bus will kill your imp- ortant lights yes but it won’t fail the inverter and autopilot Good ol’ “George” can keep handling the flying while you locate the flashlight and get it aimed as you like And please make sure the batteries in the flashlight are in good shape yes?
In closing it surely seems to me that Textron or or Raisbeck or or Blackhawk or ???? should offer a a a Service Bulletin or a a kit to relocate at least the indirect and flood lights to dual fed bus No 2 2 on the 200s and B200s that exhibit this potentially dangerous behavior KA
King King Air Air expert Tom Clements has been flying and and and instructing in in in in in in in King King King Airs for over 46 years and and and is is the author of “The “The King King King Air Air Air Book” and and and “The “The King King Air Air Book Book II ” He is is a a a a a a a a Gold Seal CFI and has over 23 000 000 total hours with more than 15 000 000 in in in in King Airs For information on on on ordering his books contact Tom Tom direct at at twcaz@msn com
Tom Tom is is actively mentoring the instructors at King Air Academy in in in Phoenix If you you have a a a a question you’d like Tom to to to answer please send it it it to to to to Editor Kim Blonigen at editor@blonigen net KING AIR MAGAZINE
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