In reply to:
I think the reason [the electric trim] is so sensitive is that in order to be effective at low speeds it has to be very sensitive at high speeds.
I was told by an old FAA salt that trim rate is predicated on performance at maneuvering speed. I nosed around FAR 23 and didn’t see anything to that effect (see below). I would be very interested to hear from anyone familiar with FAR 23 certification procedures or with the Cirrus certification about why the pitch trim rate on the Cirrus seems way too touchy, especially when levelling at cruise.
My Bonanza 36 has the opposite problem - trim rate too slow. Not too big a deal except for trimming after configuring the airplane for landing. I always have to resort to a couple twirls of the manual trim wheel on final.
Maybe this is a hint as to the speed choice in the Cirrus. Those of you who actually have the airplanes (as opposed to us mere position holders) - if the trim rate was slower would the transition to full flaps and final approach speed be awkward?
SFAR 23.11 Electric trim tabs.
The airplane must meet the requirements of FAR 23.677 and in addition it must be shown that the airplane is safely controllable and that a pilot can perform all the maneuvers and operations necessary to effect a safe landing following any probable electric trim tab runaway which might be reasonably expected in service allowing for appropriate time delay after pilot recognition of the runaway. This demonstration must be conducted at the critical airplane weights and center of gravity positions.
23.677 Trim systems.
(a) Proper precautions must be taken to prevent inadvertent, improper, or abrupt trim tab operation. There must be means near the trim control to indicate to the pilot the direction of trim control movement relative to airplane motion. In addition, there must be means to indicate to the pilot the position of the trim device with respect to both the range of adjustment and, in the case of lateral and directional trim, the neutral position. This means must be visible to the pilot and must be located and designed to prevent confusion. The pitch trim indicator must be clearly marked with a position or range within which it has been demonstrated that take-off is safe for all center of gravity positions and each flap position approved for takeoff.
(b) Trimming devices must be designed so that, when any one connecting or transmitting element in the primary flight control system fails, adequate control for safe flight and landing is available with -
(1) For single engine airplanes, the longitudinal trimming devices; or
(2) For multiengine airplanes, the longitudinal and directional trimming devices.
© Tab controls must be irreversible unless the tab is properly balanced and has no unsafe flutter characteristics. Irreversible tab systems must have adequate rigidity and reliability in the portion of the system from the tab to the attachment of the irreversible unit to the airplane structure.
(d) It must be demonstrated that the airplane is safely controllable and that the pilot can perform all maneuvers and operations necessary to effect a safe landing following any probable powered trim system runaway that reasonably might be expected in service, allowing for appropriate time delay after pilot recognition of the trim system runaway. The demonstration must be conducted at critical airplane weights and center of gravity positions.