Northrop F-5E Technical Description

[nairb121]

@Curly I wanted to ask in a new topic to leave your aileron bug report relatively clean - in the Technical Description documents you have, is there any discussion of the relationship between true AOA in degrees and the displayed AOA units? I suspect there is a mismatch in our DCS F-5E, but have been unable to find much useful. See post here for previous discussion:

 

[BIGNEWY]

Ive sent Curly a PM, we would like to see this document if possible, as long as it is a public one of course. If anyone has this please DM me. 

thank you 

[Bucic]

Are you talking about

units vs AoA mismatch or 

units-AoA relation real vs units-AoA in-game

?

[nairb121]

2 hours ago, Bucic said:

Are you talking about

units vs AoA mismatch or 

units-AoA relation real vs units-AoA in-game

?

Both, really - I've been unable to find much to correlate the true AOA and indicated units, only scattered references to stall AOA - stated in one report to be 23°, and in the -1 to be 27-28 units - Notably, this does not seem to match DCS, which places 27.5 units AOA at about 20°. This doc seems promising though, I hope we can see it in full before too long.

[Bucic]

On 10/28/2025 at 2:52 PM, nairb121 said:

Both, really - I've been unable to find much to correlate the true AOA and indicated units, only scattered references to stall AOA - stated in one report to be 23°, and in the -1 to be 27-28 units - Notably, this does not seem to match DCS, which places 27.5 units AOA at about 20°. This doc seems promising though, I hope we can see it in full before too long.

Ok. So let me tell you this - neither correlation matters. You fly by the units. Not only F-5E real flight manual doesn't bother with a conversion table or tape. There used to be a thread on this citing FMs of even newer machines with the same caveat. I am aware of the subject, I'm allergic to arbitrary, vague units and I've never seen a single reference pointing to a conversion data set. Because it does not matter in real flying.

 

Hell, you can do a quick conversion yourself. Note down 5 pairs of units vs aoa (from the in-game info bar) and just dump it into excel. Insert a trend line with the option to reveal the equation. Done.

I'm guessing it's always linear, so you can draf t a quick conversion tape like this

Edited Wednesday at 07:56 PM by Bucic

[nairb121]

1 hour ago, Bucic said:

Because it does not matter in real flying.

You're correct, knowing the "true AOA" is not relevant to typical piloting situations - all operational numbers are based on the gauge units. But the true AOA is relevant from a flight modeling standpoint, and as you know, there is fairly substantial evidence that the DCS F-5 has something amiss with its AOA modeling. I suspect that the root of this issue is an error in the correlation between indicated and true AOA - but I have no data apart from a single point, the stall AOA as mentioned above.

[Bucic]

On 10/29/2025 at 10:59 PM, nairb121 said:

You're correct, knowing the "true AOA" is not relevant to typical piloting situations - all operational numbers are based on the gauge units. But the true AOA is relevant from a flight modeling standpoint, and as you know, there is fairly substantial evidence that the DCS F-5 has something amiss with its AOA modeling. I suspect that the root of this issue is an error in the correlation between indicated and true AOA - but I have no data apart from a single point, the stall AOA as mentioned above.

For that there would have to have been ¿ a scenario where FM programmers had no data point for a specific flight condition available in plain AoA so they had to resort to AoA units gauge. Highly unlikely. 

It's also problematic from a bug reporting standpoint. It's just compounding variables.

There's a dedicated documented and acknowledged bug report on AoA capability inaccuracy. The error is significant, to the point any other discussion on AoA in higher numbers seems a waste of time until that modeling error is fixed.

[nairb121]

On 11/2/2025 at 2:31 AM, Bucic said:

For that there would have to have been ¿ a scenario where FM programmers had no data point for a specific flight condition available in plain AoA so they had to resort to AoA units gauge. Highly unlikely. 

I'm far from an expert, and I don't know what all their sources were, but It doesn't seem that unlikely to me. The flight model adheres closely to the -1 performance data, but there's nothing in there tying it to true AOA. It seems very possible that some assumptions had to be made in development.

On 11/2/2025 at 2:31 AM, Bucic said:

It's also problematic from a bug reporting standpoint. It's just compounding variables.

There's a dedicated documented and acknowledged bug report on AoA capability inaccuracy. The error is significant, to the point any other discussion on AoA in higher numbers seems a waste of time until that modeling error is fixed.

Indeed, that's my report. But it's important that it be fixed correctly. I'm fairly certain already that there is an AOA indication error, due to the mismatch in reported stall values from what we have in DCS. I think the AOA limit is just a symptom.

My theory/conjecture:

1. An incorrect assumption was made on the relation of the True AOA in degrees to the Indicated AOA in units. The flight model was based primarily on available performance data and descriptions in the -1 manual, which describe the aircraft handling purely using Indicated AOA.
2. Of particular note is the Stall AOA.
   1. The -1 manual states that stall occurs at 27-28 units (indicated) for our F-5E-3 - or 24 units in "older F-5E".
   2. The Taylor/Skow report linked in the AOA bug report, meanwhile, states that stall occurs at "approximately 23 deg angle of attack". The report does not precisely indicate which subvariant it concerns; however, based on the departure descriptions and the age of the data presented, an older variant seems much more likely.
   3. Testing in DCS shows that the AOA gauge indicates 27.5 units at a True AOA of only 20 degrees - this is wrong if Taylor/Skow is for F-5E-3 (unlikely), and very wrong if Taylor/Skow is for F-5E (which stalls earlier).
3. Two more data points: takeoff (with nose hike) and landing roll. The video quality leaves much to be desired, but these appear to indicate about 11 units and 6 units respectively. Landing roll should be at 0° AOA; takeoff nose hike adds 3°. I have not yet confirmed these in DCS. https://youtu.be/WPtpS2wf-0Y
4. Plotting these points gives a very rough idea of how "Indicated" and "True" AOA relate:
   
5. How this connects to max AOA: visually extrapolating (and correcting a little for the noticeable, but unsurprising, nonlinearity) places 30 units indicated close to 30° true AOA. This aligns closely in my view with language in the -1 which indicates various departure onsets in this AOA region, and a small ability to pitch beyond stall. Simply increasing pitch authority to fit the expected 30° AOA would result in the ability to pull 50% beyond stall - this is not consistent with the language in the manual or the expected behavior of this type of aircraft. It's my belief that the entire pitch axis behavior is scaled improperly, and not just the peak AOA, but also the lift and drag polars need to be reevaluated.
6. Another possibly related problem: the wing-snap issue. If the pitch rate is right, but the stall AOA is wrong - then you will reach max lift more quickly, the g-onset is too fast, and the wings are rapidly overloaded.
7. One more ongoing concern for me is the departure resistance - while our IHQ F-5E-3 should be much improved over the older F-5E, few if any of the departures detailed in the -1 for the E-3 are present in DCS. I'm not sure if this connects to the AOA issue at all, but I thought I'd mention it while we're on the subject.

Please let me know your thoughts - maybe I'm overthinking this, or have missed something critical, but that summarizes my thinking on this matter.