I'm working on a spaceflight simulator (FSX SpacePort), and currently developing instrumentation for NASA's Orion capsule. I'm using whatever little info is available on line and trying to identify various readouts and symbols on the Orion's Multi-Functional Display (MFD) instrumentation. In particular, Orion's Primary Flight Display MFD mode has 3 readouts that I can't quite identify:

enter image description here

The readouts, numbered and framed in faint green, are as follows:

  1. V1, orbital speed, as a fraction of current speed.
  2. Capsule Roll readout
  3. Vertical distance (Altitude), in km
  4. Vertical speed (H dot) in meters per second
  5. Vertical acceleration (H dot dot), in meters per second squared
  6. ?
  7. ?
  8. Current G load factor
  9. Heading
  10. ? ("Xtrk" - cross track distance?)
  11. Altitude vs. V1 plot, with markers for seconds-to-staging

Does that seem correct? Also, any guesses on readouts for 6, 7 and 10?


1 Answer 1


Ok - after a bit more research, I figured out what the readouts in question are: the attitude "ball", along with readouts 2, 6 and 7, are part of a spacecraft-specific instrument called Flight Director Attitude Indicator (or FDAI):

Apollo FDAI

The readouts 2, 6 and 7 are, respectively, Roll value and rate, Pitch value and rate and Yaw value and rate, with red bands indicating the rate amount. These readouts are usually not found in aircraft instruments, but in spacecraft, they are vital pieces of instrumentation. In space, there are no external factors (atmosphere) that would dampen the "spin" of the spacecraft in all 3 axis, so these readouts are vital in determining the attitude state of the spacecraft. The aircraft version of this instrument is gimbaled on 2 axis (pitch and roll), since aircraft usually always points in the direction it is travelling. However, this instrument is gimbaled on 3 axis, that includes yaw axis, since spacecraft does not necessarily need to point in the direction it is travelling.

  • $\begingroup$ What would be the difference between Heading (9) and Yaw value (7)? $\endgroup$
    – SF.
    Commented Mar 26, 2019 at 9:13
  • $\begingroup$ Heading is the value of the direction you're going. Yaw is the deflection from the direction you're going. So, if your heading is 60 degrees NE, and your yaw is -10 degrees, you are pointing to 50 degrees NE but traveling 60 degrees NE. As I mentioned, with aircraft, yaw is not prominent in instrumentation, since the air (fluid) forces the airplane to align with the direction of travel. An example of aircraft yaw is landing in high winds (a bit sideways). With spacecraft, it is a major factor, because spacecraft have to, for example, have a yaw of 180 (travel in reverse) to do a deorbit burn. $\endgroup$
    – Mitch99
    Commented Mar 26, 2019 at 17:43
  • $\begingroup$ Aviation.SE seems to say otherwise - track is the direction you're traveling, heading is the direction your nose is pointing; with side wind they will differ considerably. $\endgroup$
    – SF.
    Commented Mar 26, 2019 at 18:07
  • $\begingroup$ Ok, I screwed up in nomenclature, but the principle is the same. I could say, spacecraft is tracking 60 deg NE, heading 50 deg NE, giving it a yaw of -10 deg... $\endgroup$
    – Mitch99
    Commented Mar 26, 2019 at 18:22

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