Horizontal stabiliser without a trim tab?

The Piper TriPacer has a jackscrew that moves the horizontal tail surface rather than an elevator trim tab.

I think most of the old planes had this arrangement, meaning biplanes etc, I guess because it was ‘obvious’ and seen as the technically best way to do the job. The Pre-Cherokee Pipers were some of the last to do so. Its surely elegant but maybe a bit heavy relative to an adjustable tab.

Early Luscomes had no tab, just a bungee or spring setup. Pretty soon they installed a cable adjustable tab but as accessories were added forward of the firewall, the CG moved forward and the tab ran out of effectiveness at low speed. The solution was to bias the trim tab movement for more nose up and less nose down, which then pushes the limit of trim tab effective angle – beyond a certain deflection angle a trim tab stops generating more force. You see them now with extra area riveted on, generally without approval but it works well.

One of my planes has an all flying tail with the usual tie rod and associated geometry to move the tab and provide stability. It does make the elevator very powerful (a good thing) but its hard to make a mechanical linkage combine with aerodynamics to generate a really nice, linear stick force gradient. So you have to learn the elevator feel a bit as you get used to the plane.

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The DH82 Tiger Moth had a spring. Without a trim tab you lose the ability to control if elevator cable failed.
The Jodel DR1050 has a trim tab. We flew for months without one. It needed muscle only with a passenger in the rear seat.

Good point, but still not a universal law….The Mooney pitch trim system moves the whole tail-plane/elevator/rudder assembly as a complete unit. There is no trim tab but the system is still independent from the elevator control system. The whole assembly is hinged off the fuselage….if the elevator control rod breaks/jams you can control pitch with the trim system….

The Mooney pitch trim system moves the whole tail-plane/elevator/rudder assembly as a complete unit. There is no trim tab but the system is still independent from the elevator control system. The whole assembly is hinged off the fuselage….if the elevator control rod breaks/jams you can control pitch with the trim system….

The Mooney system is a variation on the old-style (and robust) jack screw system, as implemented by the ever imaginative Al Mooney… His career stretched back far enough to have designed the 1925 Alexander Eaglerock biplane, so he’d seen it all.

This photo is of a Monocoupe, an early go-fast monoplane, but it shows the basic layout of a no-tab trim system. In addition to independent control of pitch, flutter resistance must also be good (no tab to flutter), although that’s maybe not so important for a slow speed plane.

This happened in an Ovation. The whole tail became slightly unhinged when the attachment point became loose. They still landed it ok. A massive AD followed and a further 3 planes (from model C to Acclaim) were found which had one part wrong. Just one ever failed.

The hinge:

The early Cessna 182 (A through C), and the 180/185 had a variable incidence tail plane trim system, until the accountants switched the 182 to a single trim tab on the starboard elevator.

The 182 then developed a well earned reputation for wrinkled firewalls, as pilots in a forward CG condition seemed to run out of elevator and landed on the nose wheel. AOPA provides a good safety review of the type, with some advice to consider limiting flaps to 20 degrees if in a forward CG condition.

The early 182 is a poor man’s 180 these days. The 182 C is the last version with variable incidence trim, and apparently is the fastest of the normally aspirated 182 type, by a few knots.

If the elevator link breaks, you will presumably die.

I see the point, but it’s a bit like saying a bi plane is more safe because if you break one wing, you still have one wing left. Doesn’t the DC-3 use indirect control on all moving surfaces? (like trim tabs).