Consider first the pitch display. Motion of the pitch display short term is gyroscopic as it must be to fly in IMC. Long term it is VSI. This display has two distinct advantages, the first being that it provides an instantaneous vertical speed presentation. The second is that when the reference airplane is on the horizon the aircraft is neither climbing nor descending. This eliminates the need for adjusting the position of the pitch reference airplane to compensate for the angle the fuselage is flying. The resulting benefit of the concept is that it makes holding altitude easier.  More......

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