Understanding the Bonanza G36 Electrical System

The following article was published in the November 2016 issue of the American Bonanza Society magazine - www.bonanza.org

As an aircraft owner, maintenance issues are bound to arise. When you factor in Murphy’s Law, you will eventually find yourself at an unfamiliar airport talking to a mechanic who may not necessarily be intimately familiar with your aircraft. Because of the popularity of the Bonanza, many mechanics have worked on one at one point, so chances are they can help with many issues that have you stranded away from home.  But what about problems that aren’t so cut and dried?  Understanding the systems on your specific aircraft will help guide the conversation with the mechanic, and possibly save you a lot of headaches.

One of my clients had just taken delivery of a G36 Bonanza and arranged to take it to an avionics shop to have the G1000 panels updated.  Everything seemed normal as we taxied out to the runup area.  Once we started the Before Takeoff checklist, however, we quickly found out that Alternator 1 was not functioning properly. We reluctantly taxied back to the ramp.  It appeared the shop’s technician was somewhat knowledgeable about late model Bonanzas, because he was aware that there were two alternators installed in the aircraft.  However, when discussing the symptoms he made a comment about swapping the alternators to help decide whether it was really the alternator at fault.

It was clear to me that he didn’t have an understanding of the G36 electrical system, which is completely different from any other Bonanza.  I had a brief conversation with him to help shed light on a unique system for a single-engine general aviation aircraft. The G36 does have two alternators. But they are quite different from each other and serve very different functions.   The G36 has two electrical busses, or distribution systems, normally powered by the alternators independently. It also has two batteries, one for each electrical buss.

Alternator 1 and the BUSSES TIED condition 

Alternator 1 is traditional in that it can deliver 100 amps of power to the airplane’s entire electrical system at about 700 or more engine RPM.  While on the ground it does exactly that. This is validated by the Before Taxi checklist as you look for ZERO LOAD on Alternator 2.   The two busses are tied together by a relay. When Alternator 2 is not working you will notice the BUSSES TIED annunciator illuminated on the G1000. This means Alternator 1 is providing power to everything. The checklist reminds you to check for the proper illumination of this annunciator. When the busses are tied together, there are current blocking diodes that isolate Battery 2 from providing power to Buss 1.  A typical current-blocking diode provides a pathway for electrical current to pass only in one direction. Because of the electrical properties of the diode, the electricity that traverses it experiences a drop of approximately two volts.  This is why you see a different voltage range when checking the voltage of Buss 2 in the Before Taxi Checklist than you do in flight.  You can see this isolation demonstrated by turning off Battery 1 and Alternator 1 and observing that Buss 2 still has voltage, but Buss 1 does not. Reversing this scenario with Battery 1 and Alternator 1 switched on, and Battery 2 and Alternator 2 switched off, you will see that Buss 2 still gets voltage because of the buss tie relay.

Alternator 2 

Alternator 2 is a much smaller alternator rated at 20 amps. This factory-installed unit is the same B&C Specialties unit that is sold as an aftermarket backup alternator in pre-2000 Bonanzas (the B&C became standard equipment in A36s that year). Alternator 2 will start to deliver power to Buss 2 when the output of Alternator 2 is above 2.8 amps, which occurs when the engine reaches about 2000 RPM.  Once this happens, the buss tie relay opens, the current blocking diodes are taken out of the circuit, the BUSSES TIED annunciator extinguishes, and the two busses become separate and independent operating electrical systems.  Alternator 1 along with Battery 1 powers Buss 1. Alternator 2 along with Battery 2 powers Buss 2. The voltage on Buss 2 shows a normal operating range since the buss is now getting its power from Alternator 2 without going through the current limiting diodes. This is the normal operating condition. It continues this way until either (1) the engine drops below 1800 RPM; or (2) Alternator 2 output drops below 2 amps.  

Why this unique system? 

Why engineer a system that functions this way?  A look at the equipment that is powered by each buss will help answer this question.  Reviewing the list of equipment on Buss 2, you will find that much of it is essential for safe flight while IFR. If there were ever a problem with Alternator 1 or an issue with any equipment attached to Buss 1, it is reassuring to know that Buss 2 can operate essential equipment completely independently.  This is not to say that a failure of Alternator 1 will be a non-event or that disabling Buss 1 will go without consequence.  If you don’t have power on Buss 1, a number of important things will no longer function, such as the landing gear motor.  It is important to review this list of equipment so that you know what to expect. You might want to tab it in your POH binder (Section III, pages 3-12) so you can find it for a quick review in the event of Alternator 1 failure in flight. It is prudent to also understand how aftermarket additions such as tip tank fuel transfer pumps and various anti-ice systems function in the event of Buss 1 shutdown.  For that you’ll need to check the POH Supplement for the modification or ask the STC holder. As advances in avionics continue, electrical systems evolve and increase in complexity.  It’s up to the pilot to be aware of as many scenarios as possible so that proper troubleshooting can be performed if an issue arises.  The alerts generated by the electrical system and possible equipment failures in the G36 Bonanza could leave an unknowledgeable pilot vulnerable. Having complete knowledge of the electrical system is important in knowing how to manage equipment in normal, abnormal, and emergency conditions, and to understand how these failures will affect the rest of your flight.  This knowledge will also pay dividends when you find yourself at an unfamiliar airport talking with a mechanic about the unique electrical system of the G36.

Leave your iPad at home

I do a lot of training for pilots that are looking to transition to a Bonanza or Baron.  Often times, the transition is from smaller aircraft that may not be in the high-performance or complex category, but sometimes it will be a lateral move.  For most pilots, the transition is not very complicated - a review of the systems, differences between their old aircraft, and the new one, and flight time can get the pilot up to speed.

It always concerns me when the first 10 minutes of the first flight with a pilot turns into working on mounting the iPad, and routing the wires.  I love the iPad, and I absolutely love ForeFlight and some of the other apps out there for the Android.  Its hard to believe the capability we get as pilots for such a cheap price, but it has its place.


The first flight in the Bonanza will be focused on pre-flight, ground operations, take-off, climb, air-work, cruise considerations, descent, pattern entry, and landings.  Notice, there will be nothing that involves the iPad, and it quite frankly just gets in the way and acts as a distraction.  I'd much rather not have it installed on the yoke for the first flight.  You will need to get acclimated with switch location, instrument indications and gear indicators that may become hidden with most iPad mounts.

The only time an iPad in the cockpit makes sense for initial check out is if there is a Stratus unit available.  Ill have my iPad with me, and will be connecting to your Stratus, or Stratusx/Flightbox, so you still don't need to worry about the iPad until we start doing instrument procedures, or cross countries.

I do understand the excitement - I really do. Owning your first Bonanza is an amazing experience, and I get that you want to get all of the goodies installed in the aircraft.  Ultimately, you will want to get the installation all squared away, but for the first flight, just know - it will be mostly useless.

Bonanza G36 Dual Bus System

About a month ago, I had an instance where a student of mine had an alternator failure in his G36 Bonanza at our destination.  We ultimately determined that the number one alternator needed to be repaired or overhauled, but not before a conversation with the mechanic ensued that caused me to raise an eyebrow. The mechanic, who was not totally familiar with the Bonanza, said to me that he wanted to take the number two alternator and swap it with the number one alternator just to see if it was an alternator issue. That was the red flag that caused me to realize that he didn't understand the electrical system and prompted me to think a about how I should explain the electrical system and some of the differences a pilot will need to consider when transitioning into the G36 Bonanza.  An article on this will appear in the November 2016 issue of the American Bonanza Society's magazine.

Garmin 430 and 530 basics

Some may find it hard to believe, but I still run across pilots that have no experience with the Garmin 430 and 530 equipment.  Not that everyone has experience with these systems, but with the proliferation of these units through the early 2000's, most pilots know what they are, and have likely been in an aircraft with one installed.

These pieces of equipment have been out for quite some time, but there are still pilots that are just starting to think about getting a GPS in their aircraft, and these units provide probably the lowest cost of entry these days that will allow a pilot to get a great moving map GPS that can be approved for IFR approaches.

I put together a quick cheat sheet for the first time pilot that wants to just fly their aircraft and get used to the functions of the GPS.

Communication Side----------------Navigation Side

Setup Navigation to an airport

• Press “Direct To” Button
• Use the knobs to enter the airport identifier
•  Each airport starts with a K
•  No “K” if the airport has a number in it. (ie. C09)
• The large knob moves the cursor
•  The small knob makes letters
• Press Enter TWICE

Find Nearest airports (In an emergency)

• Rotate the large knob on the right side - all the way to the right until you see NEAREST

Reset unit to default screen

• Press and hold the CLR button
• Rotate little knob on the right, one click to the right

Scheduler Function on Garmin 430/530

Ive been in enough aircraft to know that this function is starting to get a lot of attention, but there are still times where I fly with folks that have no idea what this is, or what it is about.

In the Garmin 430/530 navigators, there is a scheduler function that allows you to set up a recurring message (Alarm) that pops up at a certain interval. I love to use this function to help remind pilots to change tanks.  The Garmin 430 and 530 manual specifically uses this as an example when setting up scheduled tasks.  I know some pilots that use this to remind them of an oil change, transponder testing, and even BFR and medical!

Check out page 157 of the Garmin 430W manual. (Its PDF page 167 in the following download).
A copy of the manual can be found on the Garmin website, or here: http://www.takewinginc.com/documents/GNS430W_PilotGuideandReference.pdf

 

The castering nose-wheel

I do a lot of Beechcraft transition training - mostly in the Bonanza.  Over the past two years, I've had three pilots come to me for transition training where there previous aircraft had a castering nose wheel, such as the Cirrus or the Grumman American Tiger.

I've noticed that pilots transitioning from an aircraft with a castering nose wheel have a hard time breaking the habit of using differential braking for turning.  This can be caught by the instructor by keeping their toes on the pedals to determine whether they are being used for steering, or whether the brakes are being applied.  An experienced instructor will be able to tell this right away.  The thought is to save on brakes while taxiing.

Another item of interest is the use of brakes on take-off in a Cirrus or Grumman.  I see this happen all the time and I personally think this is bad technique.  Once you get rolling, you should have enough rudder authority to counteract the wind (to an extent) once you get rolling.  The Bonanza has very effective brakes - attempting to correct directional control while heading down the runway is a recipe for disaster.

Independent Instructors and the TSA

One day I received a letter from the TSA (Transportation and Security Administration). It seemed innocent enough - they wanted to have me call their offices to schedule an in person review of my flight instructor records. At first, I didn't really think anything of it since I keep pretty good records and had been instructing for quite a few years at the time, but for some reason something just didn't feel right, so I telephoned the AOPA legal services division to see if they had ever come across anyone receiving letters like this. They said that they have not, but they didnt think it would be anything to be concerned about since there have been rumors of Independent flight instructors being reviewed by the TSA.

Shortly after the attack on the World Trade Center in 2001, the TSA was formed and so were requirements for flight instructors.  Many of these requirements and procedures concern themselves with foreign citizens looking to get their pilot certificate or advanced ratings, however there are record-keeping requirements and a procedural nuance requiring all flight instructors to capture information from new students even as citizens of the United States.

I set up a date and time to meet with the TSA inspector at my local airport. There was a little bit of confusion, since I live in Indiana, but instruct out of Illinois based airports. The TSA agent said he was not able to come to an Illinois airport because it was out of his jurisdiction and we had to meet him in Indiana based airport, which I thought was strange, so I arranged to meet him at an airport in Indiana about 20 minutes from my home.

The meeting started off good.  He asked me if he could see my logbook to which I declined stating that I keep all of my records of students in a separate file. I showed him the file and the appropriate TSA sign-offs for all of my students.  He wanted to see the copies of my student's passports and I told him that I did not retain them since I didn’t want the liability if these records were lost or stolen.  He told me that it was required, but I challenged him to show me the requirement in the regulation.  He said he would get back to me, which he never did. He then asked to see my proof of my annual TSA training, so I did show him those, but I only had three past years of evidence. During the question and answer, one of the questions that he asked was on record-keeping requirements for the TSA, which I thought was 3 years, but that is actually for the FAA requirement for CFI record keeping, not TSA.... Which is 5 years.  He marked this in his ledger.  I told him that I had lost the other 2 years of evidence, but I certainly did take them and could probably provide evidence that I had paid for them through the American flyers program, which he had never heard of.  He also asked to see my initial training certificate which, luckily I had taped in the back page of my logbook many years ago when the TSA requirements started. I didn't think we needed to keep records of that, since the record keeping requirement was only 5 years for them.

The agent became a little agitated and proceeded to tell me that not complying with the TSA requirements could result in a $19k fine, but he was willing to let me off with a warning and that I needed to be reevaluated after 6 months. 

Six months came along with a phone call from the same TSA agent. I told him over the phone beforehand that I hadn't had any new students in the six months prior, but he wanted to meet anyway.  The second meeting was a waste of time. He asked for my logbook again and I declined again stating that I showed him all of my records already and they are still current.  I basically watched him fill out paperwork and we said our good bye, but not before he mentioned that he will be checking in with me in another 6 months. 

I then did some research and called the TSA offices downstate and was able to get a TSA Supervisor.  I politely mentioned to the TSA Supervisor that considering I do instruction for very few students that meet the requirements of 49 CFR 1552.3, I think the inspection requirements are a little unfounded.  The result of the conversation was that I submitted an affidavit to the TSA stating that I no longer provide any training as described in 49 CFR 1552.3 which includes training toward an initial pilot certificate, an instrument rating, or a multi-engine add on.

Admittedly, this was all done out of frustration, but in reality, I was at a point in my instructor career where I only had a few students that were going for ratings, and this gave me the opportunity to focus on specialized instruction and leave the instruction for ratings to the folks that do it all of the time and are likely a lot better than me at making sure all of the nuances of sending someone for a rating are met.  A fringe benefit was that I dropped student pilot training from my liability insurance and saw a drop in premiums.

The moral of this story is that the TSA is ramping up efforts to identify independent instructors and review their paperwork.  More often than not, I am sure the experience will be a good one, but for me it was a challenge.  The silver lining was that I was able to focus my efforts on a different side of instruction.