Most of us know what needs to be done before we legally file an instrument flight plan and embark on an instrument flight. The FAA qualifies aircraft by category class and type. For example, Airplane is a category, Single-Engine Land is a class, and Cessna 182 is a type. If you had flown in the IFR environment in an airplane of the same category class and type 30 years ago, you would be safe and well qualified for the flight in that aircraft. At that time, we all flew VORs, and they all worked the same, whether they were manufactured by King, Narco, or Collins. Not so today, as now currency should be in the exact N-number aircraft to be safe realistically, but not by FAA definition. Our modern avionics are so sophisticated, and avionics equipment differs greatly from one N-number to another. Every time an aircraft goes into the avionics shop, it comes out with new features or updates. We even see database updates making the avionics behave differently, and accidental programing errors for approaches can cause deadly consequences. This is why we pay ridiculous prices for these updates… attorneys and insurance companies may contribute to this problem.
I have been very saddened by the recent number of aircraft accidents. Several accidents were fatal, including the loss of a colleague and his wife several weeks back — two dear friends of mine.
With so many different manufacturers of avionics and each having numerous models to choose from, installed by different avionics shops, all interfaced with other manufacturers’ equipment and running different firmware, how can we know how to operate this equipment? As an instructor, it has become an increasingly difficult job to teach pilots how to run this equipment. The actual flying of the aircraft going from one Cessna 182 to another Cessna 182 is not difficult, flight characteristic-wise; however, using the avionics in an instrument environment is. Having seen some pretty bazaar installs with different interfaces, I often have an idea where to look for answers.
On one install of a Garmin 950 with a GFC-500 autopilot, it took me many hours to diagnose. Sometimes, it would capture the glide path on a GPS approach, and sometimes, it would not. What was different? If the pilot used altitude preselect for the flight from takeoff to approach, there was no glidepath couple. If the pilot manually controlled altitude by pushing the altitude button on the autopilot, the glide path was captured correctly once intercepted.
Last week, I had a chance to fly with a dear friend and customer for the first time after an avionics upgrade. This upgrade consisted of adding two Garmin GI-275s to his Bonanza. Most of us are familiar with GPS steering referred to as GPSS. Seeing that most of the legacy autopilots were not designed to support this function, several avionics companies designed conversion modules to work with these autopilots. The module took the digital signal from a GPS navigator, converted it to analogue, and then put the information into the heading input on the autopilot. The pilot then used the GPSS switch to toggle between the heading bug input and digital GPSS, which was converted to analogue to direct the autopilot. During our training, we selected a GPS approach that had a course reversal. While looking for that GPSS button, I found it was no longer there. I had flown in this aircraft many times before and was sure it previously had one. After a bungled approach, we landed to go through the supplement on the new equipment to find out how the equipment was configured.
When new equipment is installed and the installer follows proper protocol, the flight supplement should show the many limitations and options that were configured in the new avionics. Some of those limitations cover the operating parameters of the new equipment.
For example, a GFC-500 autopilot has a limitation on some aircraft that it is not to be engaged below 800 feet on a departure or limitations showing the max bank or pitch limitations. On the Garmin GI275s, the limitations show what options are installed like dual AHRS (Attitude and Heading Reference System) or dual magnetometers. After consulting the supplement, we found the GPS steering option was provided by an output from the GI275, and input went to the heading function on the Century IV autopilot. It is important to note that most autopilots will not capture a glidepath while using a GPSS input going to the heading function on the autopilot, so once established inbound prior to the Final Approach Fix (FAF), it is necessary to select the approach function on the autopilot.
The main point that needs to be gained from reading this article is that it is important to know your avionics in the exact N-numbered aircraft you are flying. A G1000 system in a Cessna will not necessarily function the same as a G1000 system in a Beechcraft, even though both are factory-installed systems.
I often hear words from aircraft owners before I fly with them: “The aircraft should be in great shape; it just came out of annual.” This is when I am worried the most, for I have found more problems when aircraft just get out of the shop.
I am not trying to discredit aircraft mechanics, but the fact is that humans do make mistakes. I will not launch into IMC weather whenever any recent maintenance has been done on an aircraft, or recent updates have been done on the avionics.
Let’s understand the equipment in the exact N-numbered aircraft we fly. It is quite exciting when you ask the question, “What is it doing now?” while on a low instrument approach.
Fly safe and continue to train!!!
