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Are You Legal?

H. Dean Chamberlain
Reprinted with permission from FAA Aviation News

How about you? Are you legal? If your answer is, “Sure I am,” then what about your aircraft? You may be legal as a pilot, but does your aircraft meet that requirement as well? Most pilots are familiar with the need for flight reviews, number of takeoff and landings required for currency to be pilot in command (PIC) and carry passengers, and what is required to maintain instrument currency. But, how many pilots know what constitutes a “legal” aircraft, and understand exactly what that means?

Consider this case. The Howard 500 is a fully pressurized twin-engine aircraft with a stand-up cabin, since it was designed to be a long-range executive airplane. Powered by Pratt &Whitney R-2800 18-cylinder, two-row water-injected 2,500 horse-powered engines, the airplane burned 200 gallons per hour with a range of about 2,200 miles. The aircraft has a fuel capacity of 1,546 gallons.

The Type Certificate Data Sheet (TCDS) No. A1SW, awarded to the Dee Howard Company, lists four engine types approved for the airplane. The TCDS also lists the approved fuel for those engines. As noted on the TCDS, 115/145 minimum grade aviation gasoline is the appropriate fuel to feed those engines.

Now the question: Where in today’s world can you find 115/145 minimum grade of gasoline? Many airports sell 100 low lead (LL) and Jet A. So what do you do if you are flying into an airport with just these two choices? It’s probably a safe bet that most pilots would refuel with 100LL. They would have fuel, but are they legal?

There is no simple “yes” or “no” answer. First, look at the TCDS for any approved alternate fuel(s). Finding none, start looking elsewhere. The next logical step is to search for a supplemental type certificate, or STC. An STC is issued under Subpart E of Title 14 of the Code of Federal Regulations part 21. Section 21.113 states, in part, that: “Any person who alters a product by introducing a major change in type design, not great enough to require a new application for a type certificate under section 21.19, shall apply to the Administrator for a supplemental type certificate….”

Does anyone hold a STC for using 100LL in this aircraft and its engines? If you determine that someone holds such a STC, then the aircraft owner seeking to use 100LL in the aircraft must contact the STC holder for permission to use the STC. The owner of the STC would then have to provide written authorization to the requestor. Since 100LL is a different type of fuel, the STC holder would have had to show that using the fuel would not damage the engines or the fuel system. Also, the STC holder probably would have had to recalculate the performance data for the aircraft using the new fuel.

Fuel is just one example of possible conflicts between an aircraft’s TCDS and the actual aircraft. Other examples include engines, propellers, and other items not listed on the TCDS. This situation is especially true of older aircraft when parts availability, modifications, and repairs are not done in accordance with FAA procedures. Although the item or modification may not jeopardize flight safety, the aircraft is not airworthy, and not “legal,” if it has not been done with the proper approval process, such as using a field approval or STC.

What does this mean for you as pilot in command? It means that you need to make sure that your aircraft meets its TCDS. If it does not, was the change or modification done properly? A review of the aircraft’s records should provide a history of installed items or changes in the TCDS inventory that document what was changed or installed with the proper reference. To find TCDS information, go to, click on the “Mechanics” link, and follow the additional links to the TCDS part of the site. The site provides guidance on how to find the TCDS for your particular type of aircraft.

Check it out. You will undoubtedly learn something, and the life you save could be your own!

H. Dean Chamberlain is an Aviation Safety Analyst in Flight Standards Service’s General Aviation and Commercial Division. He is a Commercial Single and Multiengine Land and Sea rated pilot, a Commercial Glider pilot, a Certificated Flight Instructor Airplane Single and Multiengine and Instrument, and an aircraft owner.

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