FC3 F15 Approach AOA Bug Units or Degrees ?

[IvanK]

I think there is an error in the F15 AOA indicating system. The F15 AOA IRL is displayed in units NOT Degrees. Typical on speed approach AOA in the F15 according to the Flight manual is 20-22 UNITS AOA.

 

I think the AOA scale on the hUD is actually displaying AOA in degrees NOT UNITS.

 

In the HUD below we can determine actual AOA by comparing Nose position to the flight Path as depicted by the velocity Vector. Assuming he waterline symbol (W) represents the fore Aft axis or nose postion we can deduce that the angle between the Nose position and the velocity Vector is 10 degrees, so actual AOA is 10 degrees.

The AOA scale also indicates 10 degrees. Conclusion AOA scale is displaying Degrees when it should be displaying units.

 

 

I didnt check the AOA instrument .. silly I should have, but I think its the same deal as the HUD AOA scale.

 

EDIT: Checked the AOA gauge .. its the same and displays the same value as the HUD AOA scale.

Edited November 18, 2012 by IvanK

[JEFX]

I concur!

I was just now seaching this forum to see if anyone else had reported a problem with the F-15C AOA display... I have the same thing : I am used to do a nice approach with a 3 degrees glise lope, nice centered bars on the ADI and an average airspeed of around 150 knots and the AOA indicator on the HUD AND the AOA gauge both display around 10 (not the prescribed 22).

 

At first, I thought I was rusty on fighters (after those years of A-10C..) and I tried to land with a 22 degrees AOA and I crashed short of the runway everytime... NOT POSSIBLE...

 

Can someone from the team confirm this funny behavior as a bug?

 

thanks a lot!

[Smokin Hole]

Pardon my ignorance but what is a "unit" of AoA?

[IvanK]

A "Unit" of AOA is just another way of describing AOA rather than using degrees. The US in particular got the ball rolling displaying AOA as units rather than degrees....listned to the engineers rather than pilots I guess :)

 

The exact degree value of a unit is problematical as it can vary from type to type. The only one I have seen as documented value is for the A7D where a weapons manual states 1.5units AOA = 1 degree.

 

Most later US and international types have gone with actual degrees.

[Cali]

Units just seem like another pita way of making the pilot convert more crap then he needs to, stick with degrees.

[lunaticfringe]

Adding a third factor of "degrees" (the first two being pitch and cardinal direction) in an already task-saturated environment isn't exactly conducive to mental clarity. Further, the pilot needs to perform no conversion to match up the gouge performance value- it's already calculated as such.

 

In an environment where the amount of relative degrees that can be changed based on maneuver in three dimensions against the two indicators already noting things rated based on 360 units around a circumference, is it really less clear to the pilot to have his most important performance "degree notation device" listing up the tape in something more specific?

 

AoA is good *because* its different. The difference in terminology gives it focus, and importance. The pilot can look directly at one gauge and know immediately that his numbers are ahead, behind, or dead on to the "right" amount of pull, versus looking at a number and, for perhaps a split second, wonder if he read the wrong "degree" tape.

 

"Was that degrees of pitch, or degrees of decoupling of wing from relative velocity/wind?"

 

You're dead faster than you can answer that question.

[HiJack]

Angle-of-Attack (AoA) Indicator

 

As inspecting the gear landing problem on the F-15 I read the landing procedures from ED’s FC3 documentation and discovered that there is something wrong with the AOA indicator. As I read in documentation it is clear that the AOA indicator should be showing "units" and not degrees as it currently does in the FC3 F-15C. Using “units” is correct according to ED's FC2 documentation, FC3 documentation, USAF F-15 Flight Manual (USAF F-15 Series A B C D Block-7 and Up Change 5 01-Mar-1986) and all sources I can find online. I collected a few clips:

 

USAF F-15 Flight Manual:

 

USAF F-15 Flight Manual:

 

FC3 documentation:

 

I know the AOA indicator is a complicated instrument as it involves the direction of the relative wind and may take some work to do right but in my mind it is absolutely essential to have in the F-15C. If not modeled right you in fact break all flight documentation around, including ED’s own documentation! So I guess it’s all up to ED, do you want to be correct to the detail or do you just want to be detailed? If it’s impossible to get the indicator to work in DCS World then please make it so it shows 22 when I’m on final.

 

 

I bet this pilots AOA indicator shows 22 precisely!

 

 

Also for Inflight cruise and endurance the AOA has recommended setting:

 

 

And a pilot is of course required to learn the AOA indicator as any other cockpit instrument.

 

 

Please read this section about Pitch Attitude versus Angle of Attack.

http://www.av8n.com/how/htm/aoa.html#sec-leadville

 

Please read the complete guide to get the complete picture:

Angle of Attack Awareness and Angle of Attack Management

http://www.av8n.com/how/htm/aoa.html#sec-def-aoa

 

Angle of attack - Wikipedia

http://en.wikipedia.org/wiki/Angle_of_attack

 

Previous thread on the issue from 2009:

http://forums.eagle.ru/showthread.php?t=42635

[GGTharos]

Holy necro batman.

 

ED is aware of all this, and probably was aware from the very beginning. There's no notion of AOA units in SFM, so it isn't implemented that way in FC.

[HiJack]

Strange there is no confirmation on this in any of the posts then. But thanks for clearing this out then GG.

[HiJack]

Can someone with Microsoft FSX and Milviz F-15 check if the same issue is there?

 

And I find it strange that ED did not mark the section in the documentation explaining that this is not modeled. They do on other sections.