Over the years, many modification options have become available for the Beechcraft King Air. If you own or operate a King Air, there is a good chance your airplane has some modification made to it. How does the modification from the original airplane design affect the way the pilot operates the airplane? Why should I care? After all, a modification made to my airplane improves it. Otherwise, why would I spend so much time and money purchasing and installing it?
A modification to an airplane must go through a process before the Federal Aviation Administration will approve it. A supplemental type certificate, or STC, is issued when the manufacturer has received FAA approval to modify an aeronautical product from its original design. The STC approves not only the modification but also how that modification affects the original design.
Once the manufacturer has STC approval for the product, the optional equipment can be offered to the public and installed in the airplane. After installation, we may forget that there has been a change to the airplane and continue to operate the airplane using the original aircraft flight manual (AFM). Is this a problem? Maybe, maybe not. It all depends on what the aircraft flight manual supplement (AFMS) states for that specific modification.
The AFMS is approved as an addendum to the aircraft’s basic FAA-approved AFM. The AFMS is an essential part of the aircraft’s inventory and is required by the FAA to be on board the aircraft. You will find it buried in the AFM’s supplements section. If you have not looked through the supplemental section of the AFM, you are probably not alone.
The AFMS augments or supersedes the limitations, procedures and/or performance information in the original FAA-approved AFM for that specific tail number. The AFMS contains crucial information. It is important to compare the supplements to the original AFM to see what changes were made.
Any section of the AFM not changed by the AFMS remains the governing body. Depending on the modification, there may be many changes, a few changes or no changes at all. As the pilot in command, you are required to know the AFM and the AFMS, and you must be able to combine the two.
Let’s look at an example: the emergency procedure sections in a factory King Air B200 AFM compared to the Garmin G1000 NXi B200 AFMS – specifically, the unscheduled electric elevator trim checklist. There is a subtle difference between the two. This difference could greatly affect the outcome.
Before King Airs were produced with Collins’ Pro Line 21 and Pro Line Fusion systems, they had an autopilot (AP) yaw damper (YD) electric trim disconnect red button on the yoke that was a two-position switch. Pushing down to the first detent results in the AP and YD disconnecting; continuing to fully push to the TRIM DISC position results in the electric trim disconnecting. The electric trim could only be reset using the electric pitch trim switch on the pedestal. The unscheduled elevator trim checklist in the original AFM called for the red button to be pushed. There is no call to hold the button fully depressed because the electric trim is disconnected even after the red button is released. If the pitch trim continues to run away, some King Air checklists include a last step to pull the pitch trim circuit breaker.
When the G1000 NXi is installed, the red button on the yoke is modified. It is now a one-position switch. When depressed, the AP and YD are disconnected and the electric trim is interrupted. Once released, the AP and YD remain disconnected though the electric trim will reengage. Therefore, the AFMS emergency procedure will have you push and hold the red button until the automatic flight control system (AFCS) circuit breaker is pulled. If you had used the original AFM procedure – pushing and releasing the red button – the pitch trim would just reengage resulting in a possible loss of aircraft control.
The voice in your head just said, “I would just pull the pitch trim circuit breaker if it continues to run away.” Unfortunately, with the Garmin modification the original pitch trim circuit breaker is no longer on the circuit breaker panel. The AFCS circuit breaker is the breaker that needs to be pulled now. This step is also included in the supplement. If you did not know this, you would have trouble finding the proper circuit breaker to pull after you released the red button and it continued to run away.
Reading and knowing the new procedures listed in the AFMS can be critical.
You may even have trouble in the heat of the moment finding the AFMS emergency checklist. Who can look through the extremely cumbersome AFM and find the one AFMS that is needed for this emergency? Once found, locating the emergency section of that supplement and the specific emergency checklist is not optimum to say the least. Back to our originally named unscheduled elevator trim checklist, it has now been superseded by the Garmin AFMS emergency checklist named autopilot or ESP (if installed) malfunction/pitch trim runaway.
It could make your life slightly easier if you make a copy of the emergency and abnormal sections of the supplement and keep them in an easily accessible spot in the cockpit, for example in your iPad Foreflight document section or in an old-school, three-ring binder with tabs for abnormals and emergencies.
Besides the emergency section of the AFM, other sections can be supplemented or superseded. The performance section is a good example. When a modification is made, such as upgrading engines, you would think a whole new performance section would be included in the AFMS. However, this doesn’t always happen.
The FAA requires that for any modification that may adversely affect the time/distance/fuel used to climb performance in the AFM, the manufacturer must either:
- Publish new cruise, range, endurance and/or fuel used performance data, or
- Include both a limitation (in the limitations section) prohibiting the use of the fuel consumption data in the basic AFM and a statement in the performance section stating that the data is not approved for use.
Examples of the types of modifications that this pertains to include but are not limited to modifications that significantly increase the total drag on the aircraft or engine changes that affect the fuel consumption.
This policy only applies to the cruise, range, endurance or fuel used data and should not be applied to the performance data required to be published by the FARs (e.g. takeoff/land distance, climb performance). This data must still be published or a statement made that it is equal to or better than that shown in the basic AFM.
It is not unusual to see this statement in an AFMS: “Performance will be as good or better than originally published.” That can leave you wondering, “What is my true performance data?” All you can do in this instance is use the original data in the AFM.
The AFM supplements section contains information necessary to operate the aircraft when equipped with optional systems and equipment (not provided with the standard aircraft). The appropriate information is inserted into the flight manual at the time the equipment is installed. These supplements are easy to miss, but as you can see, they can contain information critical to operating your King Air safely and efficiently.
Don’t forget to take your supplements!