---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 05/19/19: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:00 AM - Re: 2 alternators and 3 questions (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 07:00:40 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 2 alternators and 3 questions > > Recommend you consider a Z-12 style installation. Leave > the 17A alternator OFF unless needed during anticipated > icing conditions . . . another condition that should > be vanishingly rare -OR- failure of the SD-20. > You're not going to experience dual alternator failure > on ANY mission . . . energy rationing with > an E-bus adds no value. Have you conducted an electrical load analysis by flight condition? There are forms that assist in organizing the data available at https://tinyurl.com/9rt6ymn Included are some exemplar spread sheets uploaded by various List members over the years. I did notice that one of the .xls spread sheets shows exterior lighting as a running load coincident with pitot heat. My instructors taught that exterior lights be turned off while in clouds. The combination of variable reflection off passing clouds combined with flashing of the strobe is distracting and can induce vertigo . . . I've experienced it first hand. Your RUNNING loads do not include landing lights (unless you have a wig-wag system or other recognition assist), trims, landing gear or flap motors, transmitter draws, etc. Just the steady state running loads are used to evaluate alternator adequacy and in some cases, battery supported E-bus operations. It may be that a well sorted load analysis will mitigate concerns for alternator adequacy. It also helps you define what switches should be ON and which ones OFF in the various flight conditions. I suspect that your suite of alternators will be shown to be entirely adequate to all anticipated missions . . . especially if your exterior lights are all LED. 20 years ago the most energy hungry system on the airplane was position lights . . . 2A per bulb x 3 bulbs x duration of flight. Xenon flash strobes are way up there too. No longer the case. In your case, it seems likely that a Z12 architecture with the PM alternator as "standby" is possible . . . crunching the numbers will confirm/deny that assumption. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.