december 2011 volume 11 • number 12 - American Bonanza Society

Tech TipsTech Tips is a sampling ofresponses from ABS TechnicalAdvisors and Technical Staffto members’ questions.Neil Pobanz, ABS leadtechnical advisor, is a retiredU.S. Army civilian pilot andmaintenance manager. He isan A&P and IA with more than50 years experience.Glen “Arky” Foulk, formerowner of Delta Strut, has beenan ABS technical advisorsince 1986.Arthur Miller has wonnumerous FAA awards asa mechanic, and runs aBeech specialty shop incentral Florida.Using external power for avionics trainingDennis Dabney, Columbia, South CarolinaI want to run the avionics with an external power source (not starting theQ. engine). I have reviewed the POH and found the procedure for starting theengine using external power. The manual also refers to supplements if the aircrafthas a standby generator, which my airplane does. The supplement is silent on theissue. So, is the procedure ALT and BATTERY switches off and turn on avionicsswitch, and it should work with no damage? Thanks so much for your service tothe ABS.The service manual calls for turning the master switch ON, then pluggingA. in the external power. (The system is actually wired so that the externalpower is locked out until the master switch is turned on and the master relay isactuated to the ON position – with a totally dead battery you can’t use the APUplug.) What you need to remember is to unplug the external power, then turn offthe master switch.You want the battery to always be in the system any time the external poweris used. The battery acts as a very large capacitor and smoothes out any spikesthat could damage transistorized equipment. I would leave the alternator switchOFF at all times while running the avionics on the APU as it would be drawingunnecessary current. —AMBob Ripley retired from DeltaAirlines as a manager of linemaintenance (Atlanta) and hasrun an FBO focusing on Beechmaintenance for 20+ years.Bob Andrews is a retiredEastern Air Line pilot, CFI,mechanic and a Wright BrothersAward winner. He owns aBeech-only maintenance FBOin Atlanta, Georgia.Tom Turner, ABS-ASFExecutive Director, holdsa Master’s degree in AviationSafety. He has specializedin Beech pilot instructionfor over 20 years.E-series expert Lew Gage and avionicsexpert John Collins also occasionallycontribute answers.Cowling louvers for E-Series Bonanzas?Donald Kuskie, Centennial, ColoradoI wish to add the venting gills to the large engine cowl panels on my E35Q. Bonanza. Is there a STC that would describe how to perform the task on theoriginal panels?A.I know of no approval to use louvered lower cowl panels on E-Bonanzas.Also, although the PS-5C carburetor will not develop the classic carb ice,there may be impact ice that accumulates on the carb parts that protrude into theair intake stream and in the intake manifold. The alternate air door, if the damperis closed in the carb air inlet elbow, will open as it will also open if the air cleanerwere to plug with impact ice and admit intake air to the engine that has beenheated during passage over the cylinders. Since the event was started by the formationof ice in the induction system, and the remedy is to apply any availableheat to the intake air to eliminate the accumulated induction system ice, thespring loaded aux air door opens and the engine then draws air from under theengine. I have measured the temperature of the air after it passes over the engine,and the temperature rise is about 30 degrees.I have been told by those wiser than I that if louvered cowl panels are installedin PS-5C equipped airplanes that the air temperature available for this “carb heat”may/will be diluted to the point that engine stoppage may occur if the ice accumulationis not halted. I have also been told by some really old time Bonanzaowners that by installing louvered lower cowl panels, the cooling of the engineand oil may not be as good as with the original solid panels. —LGVolume 11 • Number 12 AMERICAN BONANZA SOCIETY 43