F-16 Spin/Falling Leaf entry

Hello!

TLDR; Figured out how to depart flight in an F-16. Go to the departure for step by step instructions.

I had recently seen an F-16 training video where an F-16 departed normal flight. Video here:

So I began to wonder, how hard is it to depart flight in an F-16? I started looking it up and from what I found, it seemed to be pretty hard. In fact, starting with the block 25, they added a larger vertical stabilizer and I started wondering if it had to do with flight departures in an F-16. As many of you know, the F-16 is the first fighter to include negative stability into one of its features. It requires constant monitoring from 4 flight control computers to keep the plane flying.

Think of it as a piece of cardboard. Pulling it through the air is pretty easy and stable. The cardboard follows the path of your hand. Kind of like most civil aviation aircraft. This is positive stability where the plane naturally wants to return to an equilibrium. However, if you start pushing the cardboard through the air, it will either want to flip upside down or right side up.

Source: https://fas.org/man/dod-101/sys/ac/f-16.htm

Then I thought, I wonder if I can recreate a spin in DCS World! After all, almost all other negatively stable aircraft in DCS, I've practiced and played with spins, even ones that arent as unstable as the f-16, such as the f-15 and 14's. So I tried and tried and I couldn't get it!

THEN! I watched this video posted by mvsgas in this forum and I got some good pointers:

https://forums.eagle.ru/showpost.php?p=3775880&postcount=1143

FF to 6:00 to see a few spins in a row.

What I found out was that they would fly to about 30,000 ft and between 300-350 knots, which is right around mach .98 to 1.10. When they were ready, they'd pitch up so their velocity vector was about 8 degrees nose up, roll hard left or right to about 95 degrees in the respective direction and pull full aft stick. It would be about a 5.5g maneuver. Once the wings were loaded, they'd then start just rolling. When they started the maneuver, it also seems that they would return the jet to idle as when they'd start their pitch up, they were already bleeding off speed.

While practicing this in DCS, I've had to imply a couple things. First of all, I couldn't for the life of me get it to enter and then sustain a departure without using pitch override. Also, pitch override seems to be specifically to exit a departure. Second, I had limited success without using both roll input and yaw input in the same direction. Also, You can't get the speed necessary to perform this with bags. A clean configuration is best.

So, if you want to try this in DCS, here is the procedure that I've come up with and you'll enter a departure about 90% of the time. My video is here:

The Departure:

1. Climb to 35-40,000 ft @ 300-350 knots. You will need afterburner.

2. When you are almost to target altitude, press and hold the Pitch Override switch. It is just in front of the throttles to the left. You'll hold it until I mention you can stop.

3. When ready, pull throttle back to idle.

4. Immediately, pitch up so the velocity vector is at around 8-10 degrees above horizon.

5. Roll right so you are in a 95 degree bank and start yanking.

6. Since you have rolled past vertical, your nose should immediately start to drop. You may no longer be able to see the velocity vector. However, the moment your velocity vector passes through 5 degrees positive pitch, give full rudder input in the direction of your turn.

7. As soon as the velocity vector passes the horizon, give full roll input in the direction of your original turn. You should have just barely started to notice that the yaw input started the roll for you.

8. Just hold all inputs at max and wait. It'll start spinning like crazy.

9. You should notice that it sort of reaches a limit with AoA. Then, if you did everything right, at some point, it will just "snap out of it" and it will start to float like a leaf. At this point, you will still be travelling somewhat sideways. You should still be holding the Pitch Override. The plane will be rocking back and forth and side to side.

10. At this point, you can choose to recover or continue. If you chose to recover, it'll be much easier at this point to do so. Go to the recovery at the end.

Continuing:

11. Continue to deep the departure by continuing to hold it. At some point, you will be falling almost straight down. This should take an additional 10-15 seconds.

12. If you've gotten this far, you should be able to release the Pitch Override, and the plane is very nearly stuck. No matter how much throttle or stick input you give it (if not the correct procedure) you will still be floating down like a leaf.

Recovery:

This recovery technique was by Deano87 at this post:

https://forums.eagle.ru/showthread.php?t=252049&page=2

Enjoy!

Cool post! I've had the pleasure to do some of this testing IRL on the Viper. Here's a couple things I can tell you (if you're interested in learning more):

1) Watch this video: https://youtu.be/Rv9YC-gaNYo. The maneuver shown here (and in the video from mvsgas's post) is a "break turn" or "slowdown turn". To check new flight control software, the jet is intentionally loaded asymmetrically (usually 2 AIM-9's on the left (STA 1/2), 1 AIM-9 on the right (STA 9), a centerline 300 Gal Tank, and a targeting pod). This loading makes the jet very "squirrelly" at higher AoA and causes it to be directionally unstable (yaw). To mirror what is done in the HUD footage, set your flight path marker (or velocity vector as those Hornet folks call it) ~5-10 deg, roll ~90 deg left or right, and let the nose slice to the horizon (while neutralizing your stick input). Once the FPM hits the horizon, apply abrupt full aft stick and have fun! Depending on what side you loaded the missiles on and what direction you rolled before the pull, your nose will either slice up or down because of the asymmetry and you'll depart. This is due to the rudder being "washed out" at high AoA and being unable to combat the inherent asymmetries present with a configuration like that. Sweet spot for stuff like this is >35K ft and between 250-300 KCAS (transonic, as mentioned in the video above). The jet won't always settle into a deep stall (i.e. falling leaf motion) and may sometimes recover by itself. But if it does, you have the recovery procedure more or less down. Throttle to idle, engage MPO, and cycle the stick in phase with the motion of the pitch oscillation.

2) The maneuver you described (while being effective at departing the jet) is not what was being shown in the videos (pilot does not make any roll input after the aft stick input). The nose movement is completely of the jet's own accord due to the asymmetry I mentioned above. However, there is another maneuver done in testing that is similar to what you're describing. It's called a "roll-coupled departure" and there's a really old video of one from the Blue Angels somewhere on the internet but I can't find it. Basically, a combination of full roll and pitch is input at the same time, held for ~270 deg of roll, and then the pitch stick is reversed. This causes inertial coupling and the jet can no longer keep up to maintain control. There are some other maneuvers done to test this stuff as well but all the cool videos come from the SDT's and Roll-Coupled stuff.

3) I've done a couple departures so far in DCS and the FM is close to real life, but not quite there yet. From what I can tell, it more resembles the Hornet's characteristics, with some tweaks for the Viper. Real Viper will totally get "stuck" in a deep stall/flat spin. In DCS, it seems like there's more of a natural tendency for the Viper to get stuck at limiter AoA rather than the full "falling leaf". Impressive FM'ing on the part of ED nonetheless.

High AoA stuff is really cool and you get into some really weird flight regimes. Weird mechanics start to come into play so you start to experience some really "exotic" phenomena while testing this stuff like control reversals (i.e. left becomes right, right becomes left. Hopefully this was good info for you!

Awesome! I love to learn and appreciate your feedback! When I have a moment today, I'll get back on and play around with asymmetric loadings. No matter how hard I tried to have a flight departure, I couldnt get it without using the MPO but I hadnt even considered what he said in thr video about pilots being at risk after having fired a missle causing asymmetric wing loadings. I had to come up with the procedure to force the plane in DCS to do it while I was testing. I'll post my results and video later :D

Update on this. I ended up trying the maneuver described in that video. At this time, it seems the flight model is too resistant to departure relative to what they did in the video. It may work with someone else but the method I came up with seems to be the best, surefire way to depart normal flight at this time.

Be aware that in some cases fuel is used to put the CG aft so the jet is more prone to depart or go into a deepstall..

I pitch up to +35 degrees, and pull idle thrust, and just let it stall. It's quite effective.

As the nose comes through the horizon I hold aft stick, and the nose rate is too low for the aircraft to recover "naturally", AoA increases, and she's deep-stalled.

This, at about 35000 ft.

"Attacking" the flight controls is also another fun move.

Get the aircraft slow in level flight, start a pull-up as the speed bleeds off, then add full left or right aileron, and hold it there while adding full aft stick. She'll start to barrel-roll followed by spin development as the rudder can no longer control the yaw rate, and there is insufficient pitch authority to get the nose up.