Page 18 - Volume 12 Number 10

N1 N1 threshold threshold your your autofeather annunciators should come the the the 92 percent N1 N1 threshold threshold However if you you you need to to to to on and and both sides are armed and and ready to go The Test position of of the the autofeather switch is spring- loaded for a a a a good reason It makes it impossible to accidentally leave the system in Test mode and risk unintentional arming of of the the autofeather system at at an insufficient power level A A King Air’s automatic feathering system is designed to to allow only one engine to feather at at a a a a time they will never go together You will recall that the the the left engine arms the the the right side autofeather (between 400-500 ft-lbs in Test and above 92 percent N1 in in in Arm) If the the the left left engine has failed on takeoff and the the left prop goes into feather it is now physically impossible for the the right prop to feather The left engine being well below 92 percent N1 has unarmed the the right side autofeather Leaving the Switch in in Arm In my opinion autofeather is most crucial during takeoff Some leave the switch armed in cruise but at FL 250 if you had an an engine failure and the switch was off you’d still have plenty of of time to cage the problem engine On approach even if the the switch is in the the Arm position the system will not be be armed as as long as as you are below perform a a a go-around and your switch is in Arm the system will be armed as as soon as as you push the power up high enough Maintenance
Where’s the “Maintenance Tip” in in all of this? Well how you you squawk an an autofeather problem can make your mechanic’s job simple or complex Many a a a a pilot has dropped the aircraft off for maintenance on a a a a a a Sunday night and realized they forgot to write up their squawks so they leave a a a a hastily scribbled list in the the cockpit that includes “Autofeather inop ” Of course I can troubleshoot from square one and work my way to the the root of the the problem but if I get more precise information from the the start the the job goes faster and you save money How about this squawk: “Autofeather tests good on on ground but L/H annunciator fails to to illuminate on on takeoff ” Aha! That sends me straight to the R/H power lever switch on the the pedestal Or this: “Autofeather will not not test ” Great! I can verify that the greens are not not coming on at 400-500 ft-lbs torque and then I know to to zero in on those torque switches The more specific the information you you give to your mechanic the faster the problem will be diagnosed and fixed I hope this helps Meanwhile enjoy the heck out of your King Air KA
Note: This article originally appeared in the November 2013 issue of King Air and was re- published (with minor revisions and corrections) at the request of new magazine subscribers regarding this subject Dean Benedict is a a certi ed ed A&P AI with over 40 years’ experience in in in King Air maintenance He’s
the founder and former owner
of Honest Air Air Inc a “King Air Air maintenance boutique” (with some Dukes and Barons on on the side) In his new venture BeechMedic LLC Dean consults with King Air owners and operators on all things King Air related: maintenance troubleshooting pre-buys etc He can be reached at dr dean@ beechmedic com or (702) 773-1800 Trusted experts on King Air engine accessories & starter generators since 1965
Parts & Accessories Wichita KS 67211 AN
COMPANY
1-800-835-2961
16 • KING AIR MAGAZINE
OCTOBER 2018