Understanding Optimal AoA for F-5E-3

I've now flown dozens of hours in the F-5E-3. It's a great module, but I continue to lack the "feel" for optimally performing the aircraft that I'd gained previously with the P-51D and F-86F. I'm continuing to struggle in dogfighting, or turning with a heavily laden aircraft in strike missions.

Part of my confusion is over understanding how to optimize AoA in the F-5E. This is the first aircraft I've flown with an AoA gauge, but I'm not understanding the principles of how to maximize the aircraft's performance.

Here's what I know:

* F-5E is controllable to 27-28 AoA. This is thanks to E model's "shark nose", which increased high AoA controllability versus the older F-5A at max ~24 degrees.

* Buffeting starts around 15 AoA, and that point is marked prominently on the gauge.

Here's what I DON'T know:

* For best sustained turn rate (STR), what AoA do I set? Do I pull to 15 AoA and hold there to achieve the best balance of turn vs energy loss? Or is AoA irrelevant to STR? I'm trying to understand how to turn most efficiently in dogfights and don't understand how AoA is used to fly efficiently.

* Is greater lift & greater drag linear as AoA increases? Or is the buffeting at 15 telling me that I really shouldn't go above unless absolutely necessary since drag becomes much greater?

Thanks for any advice!

Best STR is the condition Ps = 0 (sustained) which has the best turn rate. You'd look on the TR v. Mach chart for the Ps = 0 line and follow it to the Mach for peak TR then look up probably what LF that corresponds to.

It's unconventional to reference turn performance by alpha although it can be done. You think thrust is almost constant with dynamic pressure and drag equaling thrust would be at a near constant alpha as well. It's just not how the thought is traditionally formulated.

I watched a video about STR and it said that G-loading is what affected STR. I know with the SU25 if I’m trying to turn faster I quickly check the G gauge (which is one side of the AOA and G gauge) and adjust back pressure on the stick aaccordingly. Too much or too little G slows down the rate of turn...get that sweet spot in-between though, and you’ll turn on a dime!

Or maybe a half-dollar, depending on how much weight you’re carrying, throttle setting, etc.

Here it is, from FlankerTraining’s YouTube channel:

I don't know if setting your turn by AoA is unconventional. The US Navy has it plastered all over their FTIs. I've been looking for this answer for quite a while. Not sure the methodology to figure it out for the F5.

Load factor divided by speed is turn rate. Speed generally increases load factor available (until corner) while increasing the path length which decreases turn rate. The best ratio of load factor (at Ps = 0) to speed is where you find maximum sustained turn rate by definition.

In P-1289 Basic Fighter Maneuvering Section Engaged Maneuvering T-45 Strike, Figure 4-3 10K E-M Diagram (page 31) you see the Ps 0 line on axes KCAS and turn rate. The turn rate is rather flat in a band 240-330 KI©AS. So the performance reference is the airspeed gauge. Get in that airspeed range and pull so as not to go faster or slower.

Same idea but for F-5E-1 (I can't find charts for F-5E-3) in T.O. 1F-5E-1 Appendix I, Part 8, Turn Performance: Turn Rate, Turn Radius and Load Factor. Page A8-31.

Ps = 0 line is shown peaking at ~0.74M for a value 13°/s. Throwing that into an ISA calculator gives ~450 KCAS at 5000'.

Dynamic pressure, airspeed or Mach, is most closely related to the performance you want and is the obvious reference. I really don't know about an alpha reference, if that's wise or not, but I've always seen STR reference airspeed. It's there in USAF and USN handbooks alike.

P-1289 also explains how to pull:

Pitch: Airspeed above corner airspeed: load limit pull, 7.33Gs (above 5,000 ft).

Airspeed below corner airspeed: lift limit pull, 19-21 units (rumble of buffet) pull.

For the pilot the most important thing is to know his options while looking at his bandit. His options are defined by his energy - speed + altitude. He will check those if he wants to know what maneuver he can fly (offensive or defensive). The AOA/G gauge doesn't tell you how much energy is left but how the pilot performs the aircraft.

E.g.

Too slow -> better no nose-high maneuver

too low -> no vertical nose-down maneuver

Why should he check another instrument if the speed gives him an already ok feedback in combination with his butt for G and AOA. In DCS we can happily ignore the G-Limits of the F5 and pull until we would black out.

Coming back to OPs interests:

I'm continuing to struggle in dogfighting, or turning with a heavily laden aircraft in strike missions.

Heavily laden: Try to turn level and with not too much AOB - eg. 20-30. Climb with wings level. If you do a good roll-in you don't need to maneuver much in the target area. If you need to be defensive by surprise use the emergency jettison button.

dogfighting

For the correct alpha and pull into the turn you also need to know if it is a turn rate fight (2C) or a turn radius fight (1C). I usually experience 2C because of loosing sight in a 1C.

As already mentioned a good corner speed for 2C is 450kn. But if you are generally above 350kn you are fine, too. Most common error is to not ease the pull after the initial turn. So if you end up slow, you pulled to much.

I continue to lack the "feel" for optimally performing the aircraft

Since the F5 is faster than the F-86 or P-51 but the turn rate is not that much better you will have the feeling that the A/C doesn't turn that much.

Little tip: Jettison the pylons if you go Air to Air.

Apologies for being away for a few days, RL situation came up.

Appreciate the replies, very interesting information! I had no idea this P-1289 document even existed. I'm looking at it right now, and it's a terrific source for how to put these ideas into action. Going to be doing some further reading there.

Based on the comments in this thread, the key seems to be knowing the relevant speed (or speed ranges) at a given altitude and weight combination. That information can be found in the relevant "Dash-1" manual for the aircraft (at least modern American models), correct? Also, AoA is less critical as a target, and should be used more for mananging energy loss efficiently (as in don't use any more AoA than absolutely necessary for the STR desired).

The tips on flying heavy also help. I've learned to use the AoA indicator in the F-5 as a measure of how much "reserve" turning ability I have in the jet. When I'm low and slow with a heavy bombload and I'm calculating if I can make that 180 turn in a tight mountain valley for another pass, I now glance down at my AoA indicator to see if I have the "reserve" to pull the nose around or if I'm just going to mush.

I think you are right, AOA IS EVERYTHING, but is very misunderstood, you know if you are depleting energy or if you are keeping it or if you can increase energy by putting certain amount of AOA units and if you are stalled or not.

I think sim do a bad job simulating this.

What we all need is good performance tables for each module that explains relationship between AOA/SPEED/Rate of turn etc. Or experiment a lot with tacview