February 1, 2001
Steven W. Ells
Abbott needed Costello; Laurel needed Hardy; and Babe Ruth needed Lou Gehrig. James Brown needed the Famous Flames and Zanfir needed a set of panpipes. Without the airworthiness certificate, registration certificate, operator's manual, and weight and balance data an airplane is not airworthy. So it can be accepted that airplanes need paperwork. And in the paperwork of weight and balance, the airplane weight and balance data needs an up-to-date equipment list to be complete and legal.
During airplane weighing the airplane is leveled, the scale readings are recorded, and calculations are made to determine the airplane's empty weight and empty-weight center of gravity (CG).
This information is dated and signed by an appropriately rated mechanic and inserted in the aircraft records on a weight and balance form, or in the weight and balance section of the pilot operating handbook (POH).
But there's still more work to be done, for a complete weight and balance record contains not only the empty weight, arm (CG), and the empty-weight moment of the airplane, but must also contain a current equipment list. This is the area where the paperwork of many airplanes, which are thought by their owners to be well maintained, figuratively leaks a little oil.
An equipment list is exactly what it says-a list of all the equipment installed in the airplane, along with the arm, or CG, of each piece of equipment and the resultant moment. FAR 23.29(b) and Civil Air Regulation (CAR) 3.73 require this list, and the weight and balance information. When a piece of equipment or avionics is removed or added, the change must be entered into the equipment list in order for the airplane to remain legal.
For one reason or another, the equipment list is not always updated when gear is removed or replaced. Yet, a new weight and balance revision sheet is almost always created and added to the weight and balance folder in the airplane. So why doesn't the equipment list get any respect? One reason may be that the existing equipment list has become so far out of date that updating it would take a lot of time, money, and effort.
Mechanics are often hesitant to charge an owner the four to eight hours necessary to re-create a current equipment list, and even if they weren't, many owners balk at paying shop labor rates for what they consider to be nonessential paperwork. Fortunately, creating an up-to-date equipment list is relatively easy and is a perfect task for an owner to undertake over a couple of winter weekends.
Not only is the task of creating an equipment list within the capability of most owners-an equipment list can be customized to fill more than one need. For instance, expanding the format to add extra spaces for the part number and serial number of each piece of gear is easy. This option creates a good way to track the calendar times and hours-in-service of components such as gyros, vacuum pumps, and turbochargers. It also is a convenient place to note serial numbers of avionics and other semi-portable items in case these numbers are needed for an insurance claim.
Admittedly, it would take a lot of work to remove and replace every component to initially record the part numbers and serial numbers, but the process could be initiated by starting with the engine, prop, magnetos, prop governor, and carburetor or fuel injection unit part and serial numbers, which are easy to note during an annual. Then anytime a component is sent out for overhaul or replaced, the numbers could be plugged into the equipment list.
A spreadsheet program is usually the easiest way to create an up-to-date equipment list. The first task is to determine what items are currently installed in the airplane. Do this by taking a copy of the existing list to the airplane and comparing it to the equipment that's actually installed.
The most common discrepancies between the list and the airplane result from avionics and STCed equipment changes that haven't been entered on the equipment list. This look-and-check list-amending task will be easier after studying the manufacturer's original list to get an idea of equipment list nomenclature and notations. For instance, if a list maker isn't aware that an option for a Cessna pilot's seat could be an "articulating, reclining, vertically adjustable" seat he might not include that in his new list.
The pre-study of the existing weight and balance data will help the list maker realize that the goal is to list every piece of installed equipment-the audio panel as well as each radio; the sun visors; the shoulder harnesses; the horizontal stabilizer abrasion boots; and such small items as the rear window curtain. After listing everything installed, the next step is to determine the weight and arm of every piece of equipment. Going back to the existing list is often the best place to start.
If the original weight and balance record is missing or has been defaced, in many cases owners can buy a certified copy of this important document from the customer service department of the airplane manufacturer. While the original report isn't necessary for airworthiness, obtaining a copy eases the task of creating a new equipment list and rounds out an aircraft's records.
Airplanes certified under the Civil Air Regulations before January 1, 1958, were issued aircraft specifications. These aircraft specifications are a treasure trove of weight and balance information for these early airplanes. When the Civil Aeronautics Administration became the Federal Aviation Agency (January 1, 1958) these specifications were replaced by type certificate data sheets (TCDS), which no longer listed items, arms, and weights. For an example of aircraft specifications see the Web listing for a 1939 Beech D17S Staggerwing ( www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/ f2f667488a8495328525676200542f0b/79c959480ea3ab018525673f006d944f/ $FILE/ATTCQDGG/A-649.pdf). Compare the wealth of weight and balance data in the Staggerwing aircraft specifications to the complete lack of weight and arm information on the type certificate data sheet for the 1997 Cessna 182S on the Web ( www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/ f2f667488a8495328525676200542f0b/49fc3f99233cd42e862569580056d27f/ $FILE/3A13.pdf).
When the aircraft specifications were replaced by the TCDS, the task of supplying the weight and balance data that had been contained in the aircraft specifications was taken over by the airplane manufacturers.
For years Cessna provided component weight and balance information by supplying each airplane with a comprehensive list of all the equipment that was available from the factory for that model airplane. The comprehensive list was made aircraft-specific by letters or x's on the lists identifying all the equipment that is installed in each specific airplane.
This format was changed when the General Aviation Manufacturers Association (GAMA) expanded-format pilot operating handbooks (POH) replaced airplane owner's manuals in the late 1970s. The weight and balance chapter in the new POHs had been expanded to include all the data that was previously included in the comprehensive list mentioned in the previous paragraph.
This chapter contains a detailed list of all of the optional equipment with corresponding weights and arms and is a valuable source when gathering data for equipment lists. Savvy list makers will often refer to a POH-or its generic and less expensive equivalent, the information manual-for equipment list details that are fuzzy in earlier owner's manuals.
When POHs replaced the owners manuals, Cessna started supplying a document titled Weight & Balance and Installed Equipment Data with each of its single-engine models. The N number, the serial number, and the model of the aircraft are listed at the top of the page. This was followed by an item-by-item equipment list and the empty weight, arm, and moment of the items and the airplane. This document, used in conjunction with the POH, almost reduces the creation of a new equipment list to a fill-in-the-blanks exercise.
After listing each piece of equipment, all that remains is to determine the weight and arm. The moment can be derived by multiplying the weight by the arm and is always expressed in inch-pounds. The arm is the center of gravity of the installed equipment and is always listed in inches forward or aft of the datum. Let's discuss how to determine the arm of a piece of equipment.
The weights and arms of common equipment can be taken off the factory lists, out of the POHs or information manuals, or the aircraft specification lists. If equipment has been installed that isn't listed in any of these sources, it's often possible to determine the arm of an item of equipment by referring to the service manual. All service manuals, except the very earliest, have three-view drawings of the airframe and notations about the airframe and wing reference stations.
By referring to the drawings in the general specifications section of the service manual for a Cessna 180, the aft face of the fuselage bulkhead that the baggage door hinges off of can be identified as fuselage station 90.0. This means that the aft edge of this bulkhead is 90 inches aft of the datum, which in this airplane is the forward face of the firewall. By knowing the arm of that bulkhead surface, determining the arm of any piece of equipment that's installed nearby becomes no more than a simple measure-and-cipher exercise.
Weights and arms of equipment that has been installed by STC, such as STOL kits, can often be obtained from the STC holder.
Spreadsheet programs, such as Microsoft Excel, can be easily configured for use as an equipment list. The simplest form would have nothing more than four columns. From left to right, the columns would be titled "item," "weight," "arm," and "moment." We've posted a downloadable Excel example on AOPA Online ( www.aopa.org/members/files/pilot/2001/anp_intro0102.html).
Expanding the form to include component part numbers and serial numbers and/or the date and tach time a component was installed will facilitate component recordkeeping. This combined form fulfills a need and a want-the need to have a current equipment list and the desire to maintain equipment records.
If the factory weight and balance report is still in good shape, and very few equipment or avionics changes have occurred over the life of the aircraft, it's probably simplest to make any changes right on the original weight and balance report. Draw a single line through removed items and add the information pertaining to the replacement items at the bottom of the page, and the work is done.
If the records are in sad shape, or changes that have occurred over a couple of decades haven't been entered in the equipment list, it's time to create a new document. Once the sources of information are known, the actual task of creating the list and noting all the information shouldn't take too long.
If the equipment list isn't up to date the pilot is subject to the same kind of information dark hole as the citizen who loves his new car because it can go 400 miles between fill-ups but doesn't know how big the gas tank is. For weight and balance data to be trustworthy, the pilot must know what equipment was installed when the airplane was weighed.
Links to additional information about airplane equipment lists and the Web sites referenced in this article may be found on AOPA Online ( www.aopa.org/pilot/links/2001/links0102.shtml). E-mail the author at [email protected].
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