Tail Tales

What works on one airplane might not work on another.

- PETER GARRISON

Back in the day, when FAA employees outnumbered amateur airplane builders, a government inspector would do a “pre-closure” inspection on every part of your homebuilt, then return for a pre-first-flight inspection and again every year thereafter. The quality of these inspectors varied. Some were skilled A&Ps who almost always found a discrepancy that you had overlooked or had some useful comment or suggestion to offer. Those you welcomed. A few, however, barely knew one end of an airplane from the other.

It was one of the latter who showed up for the pre-first-flight inspection of my first homebuilt, Melmoth. With thinly-veiled bewilderment, he walked around the airplane—which was fairly large and complex for its time and, furthermore, of all-metal construction, an idiom just gaining prevalence among homebuilts in 1973. He finally paused for a long time to contemplate the horizontal tail before delivering himself of the opinion that the elevator looked awfully small.

Indeed, it would have been awfully small—had it been an elevator. But it was not; it was an anti-servo tab.

Melmoth had what is variously termed a “stabilator,” a one-piece or an all-flying tail. Like T-tails, these were quite fashionable in the 1970s; they are less so now. Claims of their advantages always included the assertion that the single-piece surface was more aerodynamically efficient than a hinged elevator. The conventional two-part arrangement has the perplexing property that, as you raise the elevator to lift the nose of the airplane, the leading edge of the stabilizer rises as well, producing a force opposite to what is needed. Because it was not working against itself, the stabilator could in principle be made smaller and lighter without sacrificing effectiveness.