-1
$\begingroup$

An F-16 Fighting Falcon is nose up at 25 degrees angle of attack (AoA) and unable to keep the level flight path but it is in a $600$ feet per minute dive slope. Does the attitude direction indicator (ADI) show more of the sky or more of the ground?

$\endgroup$
6
  • 2
    $\begingroup$ Angle of attack is not a variable in the pitch attitude of the airplane. You can be at any AoA at any pitch attitude. What is the power setting? $\endgroup$
    – wbeard52
    Jul 20, 2023 at 16:45
  • $\begingroup$ The power setting is on the left side of the curve ,but I'm interested only the attitude showed on ADi ,regardless of the /climb /dive (here)velocity. $\endgroup$
    – George Geo
    Jul 21, 2023 at 5:16
  • $\begingroup$ 600 FPM is 3 degrees or so flightpath below the horizon at normal approach speeds; it would be perhaps 1 degree below the horizon at 250 knots. So if your flightpath is -1 to -3 and your AoA is +25, your pitch can be estimated, as long as one assumes thing like wings level and some sort of reasonable airspeed. (If assumptions can include unreasonably slow forward speeds, ie a VTOL hanging in the air with barely any forward or vertical speed, then everything is "possible", if pretty wildly hypothetical.) $\endgroup$
    – Ralph J
    Jul 21, 2023 at 6:14
  • 1
    $\begingroup$ "An F-16... is nose up at 25 degrees angle of attack (AoA)" -- this sentence is confusing. The implication is that "25 degrees" is meant to specify exactly how "nose up" the plane is. It sounds like you meant to say the pitch attitude is 25 degrees. Did you? Or did you mean to say something like "The nose is above the horizon at some unspecified angle, and the angle of attack is 25 degrees" --? Pitch attitude and angle of attack are two completely different things. Or by "is nose up" did you not actually mean that a/c was in a positive (nose-up) pitch attitude? Please clarify. $\endgroup$ Jul 22, 2023 at 11:15
  • $\begingroup$ (As long the a/c really "is nose up" relative to the horizon, the answer seems obvious.) On the other hand if the question is only meant to specify that the a/c is nose-up relative to the flight path, then you really need to say that explicitly, because that's not what we normally mean by "nose up". As it stands now the question is confusing. $\endgroup$ Jul 22, 2023 at 11:42

1 Answer 1

9
$\begingroup$

If the nose of the airplane is above the horizon the ADI will show more sky than ground.

Rate of descent, AoA, and power setting are all irrelevant. The ADI displays only attitude with respect to the earth's horizon.

$\endgroup$
11
  • 1
    $\begingroup$ Adding to this excellent answer, (totally correct without any irrelevant additional details), in the HUD, which also displays aircraft attitude as the HSI does, among the other info displayed is a flight path marker, which is positioned over the spot representing the aircrafts current wind- corrected flight path or velocity vector. The difference or displacement between the two represents the aircrafts AOA, sideslip angle, and any wind correction. $\endgroup$ Jul 21, 2023 at 12:59
  • 1
    $\begingroup$ true , but I want to isolate the ADi . $\endgroup$
    – George Geo
    Jul 21, 2023 at 19:16
  • 1
    $\begingroup$ @Timbo, I think George was referring to Charles' comment. (i.e. he isn't interested in extra information about the HUD, sideslip, velocity vector, etc...) $\endgroup$ Jul 22, 2023 at 0:56
  • 1
    $\begingroup$ The only reason (albeit a minor one) to add these extraneous details, would be to educate the op about what these other variables (like AOA, sideslip angle, etc. etc. ), are, how they relate to aircraft pitch attitude, which is displayed on the ADI, so that the answer to his question might make more sense to him. As his question, as worded, might betray a fundamental confusion about the relationship of these concepts. $\endgroup$ Jul 22, 2023 at 2:41
  • 1
    $\begingroup$ @Michael, I deliberately added these extra details as a comment, rather than as a separate answer, because, indeed, your answer was totally correct, and directly answered the op's question. It does not need any additional details. What I added in a comment would on no way be a complete answer to his question. It would be incomplete and confusing as a separate answer. However, in future, when I comment on one of your posts, I will word my comments to make it more explicit that I am not implying any fault or criticism of your answer. $\endgroup$ Jul 22, 2023 at 14:39

Not the answer you're looking for? Browse other questions tagged .