# Do mechanical attitude indicators have rotation limits?

Do mechanical attitude indicators have limits to the rotations they can display?

Wondering since gyros suffer from gimbal lock when two axes become aligned (e.g., at 90 deg pitch, if you were doing aerobatics?)

Digital gyros suffer from gimbal lock as well, though the cause is now the mathematics which loses one degree of freedom when two axes become aligned.

• I'll never forget the calm comment uttered by my friend from the front seat of a tiny 2-seater who was teaching me to fly as I rolled it a bit too aggressively: "You know, when you roll beyond x degrees, that's technically an aerobatic maneuver". Jan 26 '21 at 5:33

They do. When an attitude gyro is rolled or pitched beyond its limits, the gyro gimbals hit their stops and the instrument is said to "tumble".

Tumble resistance is more important in military craft, which traditionally use a gimbaling mechanism that can withstand any amount of roll without tumbling- which differs from those used in GA aircraft.

These two types of attitude indicators have names, and I invite the experts on this site to furnish them.

• Why is the term "tumble" used? If you roll beyond its limits does it just look stuck, or does it spin wildly? If the latter, what actually makes it do that? Jan 26 '21 at 5:28
• @RockPaperLz-MaskitorCasket, I do not know. I've played around with both types of gyros in my collection but never while in flight. Jan 26 '21 at 6:42

Typical limits for attitude indicators fitted to GA aircraft depend on how they are powered.

Pneumatic Attitude Indicator limits are typically +/- 60 degrees in Pitch and +/- 110 degrees in Roll

Electrically powered Attitude Inicator limits are typically +/- 85 degrees in Pitch and unlimited in Roll

These limits are determined by the internal construction, for example the apparatus required to drive the gyro rotor by air jet and the pendulous vane erection system will limit gimbal movement more than an electrically powered device.

More sophisticated AI’s powered by remote vertical gyros are available for fully aerobatic aircraft.