Originally Posted by
FGD135
flyingfalcon16,
Here are your answers:
Not necessarily. The nose down trim will create the tendency for the nose to pitch down. This "tendency" is better known as a "moment". There are many pitching moments acting at any given time. Which way the aircraft pitches, if at all, depends on what the sum of those moments is. If the sum was zero, for example, and nose down trim was applied, then yes, you would expect a pitch down result, but the application of nose-down trim does not guarantee a nose-down, or negative, pitch attitude.
Note that a pitch-down does not necessarily result in a "negative pitch attitude". In aerodynamics, the latter is considered to be a pitch attitude whose angle is below the horizon. An aircraft with a pitch attitude of positive 45 degrees, for example, could experience a pitch-down such that it's pitch attitude was now positive 30 degrees. Both these attitudes are considered positive pitch attitudes.
To clarify, I didn't mean to suggest MCAS will
result in negative pitch attitude, but that it
adds negative pitch attitude. Your wording is better. MCAS creates a pitch down moment. Thx for the example too.
Originally Posted by
FGD135
Trim changes create changes to the pitching moment. This is true for everything on the aircraft. Extending undercarriage and flaps, increasing or decreasing thrust, etc - all create pitching moments. At any time in flight, there are many pitching moments. Whether the aircraft pitches up or down, and at what rate, depends on the sum of all those moments. If the sum is zero, for example, then there will be no pitching.
So isn't it accurate to say, since MCAS creates a pitching down moment by adjusting trim, it is effecting the final attitude of the aircraft, which is determined by all pitch moments acting on the plane? Or put very shortly: MCAS effects the pitch attitude of the plane. Since by changing the aerodynamics of the plane, trim effects pitch.