Tips on high speed ground handling during landing.

[DmitriKozlowsky]

I am having a bit of hard time, handling landing roll of Viper. Difficult to keep it on runway centerline. It wants pull to the right. Above 80 knots I use rudder. Below 80 knots I loose rudder authority and nose wants to drift to right. So below 8o I turn on NWS, and gently try to steer it. Except it ain't responding gently. Viper veers to left and tips onto its side. Nellis 21 runway is really kicking my butt on recoveries with Viper. No problem T/O. No problem taxiing up to moderate taxi speeds of 30 knots. But landing once nose gear touches, aircraft becomes a bucking bronco. 

Approach , no stores, 1200 lb of fuel .

App speed to threshold 220 knots 

APP speed at threshhold 180 knots

T/D speed with 10-12 AOA 150-170 knots. Hold noseup until it settles by itself around 100-80 knots. Strong left rudder deflection to keep nose down the runway.

Begin pumping wheel brakes with 2 second holds. Nose drifts to right, rudder looses authority. NWS is turned on with pedals neutral.

Counteracting right drift , with left pedal deflection. Aircraft looses directional stability at 70-60 knots and keels over onto its side.

 

[Deano87]

It can be tricky. Although I haven't seen any issues as bad as this as long as there are no excessive crosswinds involved. I use around 30 curve on the rudder pedals on the Viper in order to smooth things out on the ground, they are basically footrests in flight anyway  . I usually put nosewheel steering on as soon as the nose touches down. Make sure both your toe brakes are getting full travel, so you're not doing any asymetric braking. Also are you using Stable or Beta? 

[Xavven]

Full brakes is currently causing lockup and the viper steers right. If you're using pedals, try around 80% braking force. If you are using keyboard, try holding much less than 2 seconds. Another thread on this forum suggested anti-skid isn't implemented right now and possibly could be fixed later, helping us with maintaining control on rollout.

[danny875]

I have read in several places that NWS should not be used at speeds greater than taxi speed. 
So I only engage it just before runway turn off.

As mentioned the brakes are kinda broke at the moment, anti skid appears not to work and the wheels lock up too easily.

There is another post on here by a retired IP for the F16 where he takes you through the landing in great detail.

My main takeaway from that was to only brake from around 70 knots, until then it’s just aerobrake and aft stick/ full air brake.

Edited December 29, 2020 by danny875
Adding quote

[danny875]

On 12/22/2020 at 7:19 PM, FoghornF16 said:

Retired USAF F16 IP here, now turned civilian-employee test pilot on the same airframe.

This could be a 30-page document, but I will try to keep it brief.

Caveats & Assumptions:
- I assume DCS properly simulates aircraft aerodynamics, which I cannot attest to;

- USAF F-16CM, C-Model. NATO birds are lighter, ergo, numbers are different;
- NATO standard 9000' runway, w/ 1000' overruns;

 

Procedures & Techniques:
Approach at 144 +4 knots per 1000# of stores and fuel.  This will give you an 11^o AOA approach, which is slightly fast to the T.O. 1F-16CM-1 which states 13^o AOA, but is operational standard to keep the lieutenants from dragging the speedbrakes on the pavement (not a joke).  You do this by flying the FPM at the top of the AOA Staple in the HUD.  Top of the staple is 11^o AOA, bottom is 15^o AOA.

As you come down final, aim the FPM in the middle of the approach-end overrun at 2.5^o-3^o glide slope.  Counter to traditional flying, this is a power-on approach... here you will use POWER to control AOA, and PITCH to control Aimpoint.  As you approach the overrun (might just start getting ground rush here, or start a little before ground rush), shift your FPM to the threshold, pause a heartbeat, and then shift the FPM to the horizon and pull power to idle just before you cross the threshold.

Arrest your sink rate with stick, pause a heartbeat, and then set the airplane gently onto the runway surface.  Yes, you have to manually fly the jet onto the ground (more on that in a moment).  You should touchdown in the first 500' of the runway, unless you were landing from a precision approach like an ILS, which will guide you to a 1000' touchdown.  Never accept a long touchdown.  Power up, take it around and do it again, Lieutenant.

 

Once down, ease the nose up to 15^o AOA / FPM at bottom of the staple (no more or you'll drag the speedbrakes) and hold it there (this is an aerobrake), until less than 100 KCAS.  The nose should naturally slowly fall until the nose gear touches down as well.  Full override on the speedbrakes and hold (if DCS sims that) with full aft stick, and gently test your wheelbrakes to ensure they are working (now... when you have enough time and runway left to throw the hook down and take a cable if they don't).  If wheelbrakes check good, then come off them and continue rollout with just full speedbrake & full aft stick until airspeed is less than 70 KCAS, then full wheelbrakes to a stop.

 

Comments:

The reason you have to fly the Viper onto the ground is because the F16 wing does not stall as you are landing; the DFLCS keeps rolling more and more LEF and flaperon as the airspeed bleeds off in the flare to keep the wing flying.  It is a common (and much mocked) sight at the Luke and Holloman, with the first landing attempts of new F16 B-Course students, to see the D-model floating down the runway for 3000' or more with the tires 2" above the pavement, because the student is waiting for the classic stall of the wing like in the T38... which never comes as runway ticks away.

I have landed 10 minutes after takeoff with full air-to-ground ordinance aboard, 2 full bags of gas and an ECM pod on the center, in the rain, on a NATO standard runway... 2000' more than needed.  You have PLENTY of runway available, I can attest to that (again, assuming DCS is simming accurately).

Fly-By-Wire Flight Control Systems are amazing.  But very, very different from what a 'traditional' pilot is used to.  Thank you for your time; I hope this helps.


P.S.  Finally, something I can discuss on here without violating clearances!  -- Foghorn

 

[taco3rd]

I like rudder more than NWS. I'll wait until the rudder becomes completely ineffective before switching over. That NWS is way too twitchy at default. I like to put a 25 curve on it but I still don't like the response of it. I think it just takes time with the jet and knowing how to be proactive with the rudder before those characteristics, like pulling to the right, becomes an issue. 

Edited December 29, 2020 by taco3rd

[DmitriKozlowsky]

Thank you. 

Did an approach to Batumi on default standard day. No cross. Stores AIM-9X x2, 2200 lbs of fuel.

Approach 180 knots , slowing to 165 kias at threshold. Brake out, trying to hold 10-11 AOA. Throttle in power range, about middle. Throttle to idle 1 sec after gear touch. Held nose high , but nose would not settle and I was running out of runway. Slightly forced nose gear to runway, then applied brakes at 80% (anti-skid ON). Used almost all of runway. Stopped about 2 Viper lengths from grass. Viper did drift right, and I countered with rudder, then work the NWS. Not elegant, but aircraft stayed upright. IP post was gold. OK, I admit, perhaps I was a bit late on full stick aft, after three point contact because I did not want to risk nose raising. My air brakes were out full.

What I am having difficulty understanding , is how others, keep the aircraft straight down runway below 80 down to 40 using rudder without NWS, when in my case, I quickly loose rudder authority on ground below 80. Its not instantaneous loss. But its quick gradual. At 70 with three points of gear contact, rudder has no effect. If aircraft drifts to the side, I have to use NWS, or I slide into sideline grass. My pedal curve is 25. Works fine everything else.

Edited December 29, 2020 by DmitriKozlowsky

[taco3rd]

Unless something changed on the last update perhaps, anti-skid isn't implemented yet, so mashing the brakes will eventually produce skidding. From your description, you may be using your brakes too early. I personally use aft stick and air brakes to get myself well bellow 100 knots before using 2 second stabs at the brakes to avoid skidding. I'm no expert, but I'm pretty close to 100% landing success unless its some crazy windy rainy day in the Caucusus.

[danny875]

Throttle to idle before touchdown, I think it should be about when you cross the threshold. Re-read the IP post.

as for how do I maintain directional control, I use medium pressure not threshold braking and make use of differential braking.

Prior to that I maintain 13-15 AOA in the aerobrake and rudder to maintain centreline, once the nose drops on its own I maintain full aft on the stick and deploy full speed brake, then as suggested I test out the brakes. Once speed is about 70 I brake carefully.

[DmitriKozlowsky]

Anti-skid ain't working. Now it makes sense. I am skidding and I did not even know it. Viper needs to be Norwegianized. Our Norse NATO allies operate A and CCIP A Viper of snowpack runways, and use brake chutes. 

[taco3rd]

I think just find a way to get down safely and reliably, then strive for perfect technical landings. I like to come in a little hot, maybe around 160-170 knots. It allows me to flare a little more aggressively and you can touch down smooth as can be. When you do a multiplayer mission the others in the squadron usually appreciate the guys that can get down fast.

Edited December 29, 2020 by taco3rd

[ruddy122]

What works for me is make the wheel brakes an axis command on the joystick to stop the swerving

Like this thread says the Anti-Skid isn’t perfected yet but there’s some good work arounds

NWS is twitchy at best so use small inputs or you run the risk of flipping over or off roading both of which is bad

The Viper is easier than the DCS Hornet in my opinion and a lot of fun

You just have to treat her right


Sent from my iPhone using Tapatalk

[DoctorVixen]

i leave the nosewheel steering off at 8o knots, rudders still work a bit and u can be as rough with them as you want, u can also use the brakes to steer a bit, when rudder does nothing anymore i engage nosewheel steering but u need to be gentle with it. Do u have the rudder set to an axis or do you use your keyboard?

 

Try trim the plane a bit for landing, in the beginning don't go to slow. 

I find 170 knots with speedbrakes out nice for a final approach, 190 - 200 knots before the final approach (brakes out). I use about 8 degrees angle of attack and cut the throttle when i am about to touchdown. on touchdown increase from 8 to 11-13 degrees aoa, keep pulling the stick back (harder and harder) to maintain 13 degrees aoa until it is impossible. then start braking. i have set this to an axis but i can imagine on a keyboard you need to do some tapping.

Edited December 29, 2020 by DoctorVixen

[danny875]

Hey Dmitri,

At 1200 lbs fuel and no stores you are gonna float some way... try adding two fuel tanks at least (144 Approach speed + 4 for every 1000lbs of fuel and stores).

180 at threshold is far too fast, at 1200lbs fuel app speed should be about 150 max (plus 5 if applicable)

 

[DmitriKozlowsky]

Yep. But I think I got it. I know what the issue was, or at least I think I know. I was skidding. All good.  

So has anyone tried to replicate this in DCS. Some time back one  of the ED developers posted visualization of their real-time wingtip  vortex of a large aircraft. I am curious if thrust is calculated in their real-time sim. Setup B-1B to T/O, then get close behind, see of his thrust flips your Viper.

 

[Dee-Jay]

Hi!

Wake turbulence is different than Jet blast. I don't know is jet blast is implemented yet, and wake turbulence is extremely exaggerated (on F-16 at least, I don't know for other modules).

Regards.

[DmitriKozlowsky]

Oh yeah. Brake chute would be nice. If on landing roll Viper starts on wobble and begin to think its a drift-mobile from F&F films, pop the chute to straighten it. I watched an old USAF film brief on B-47 landings, and how brake chutes can save aircraft in that situation. Although the film was straight on to say that brake chutes should not be used to correct a bad landing or pilot error. But when I get into landing roll wobble I don't have enough speed or time or runway to goaround, which IMHO is result of both pilot error and fast landing. 

[ruddy122]

Wake turbulence is scary

I was number 2 of a KC10 three ship and I hit the wake of lead

The plane wanted to flip I had to fight to keep it right side up

This was the time that A300 biffed it in NY

Naturally I didn’t touch the rudders used the stick to bail me out

Still scary all these years

Moral don’t hit wake turbulence not fun


Sent from my iPhone using Tapatalk

[FoghornF16]

Oh boy.   I can gas-bag some more.  Again, I can't attest to the fidelity of DCS's simulations, cuz while I own DCS Viper... I have only flown it once and said, "I'll put that away until it gets more developed".  So modify these Real World techniques for use in DCS.

Rudder use on the ground
IRL, the rudder is effective down until the airspeed indicator stops indicating @ 50 KCAS.  Once the nose falls from the loss of stab authority during the aerobrake (approx. 100 KCAS), rudder-only for directional control until at a safe taxi speed.  If a full boot of rudder isn't doing the job, LIGHTLY drag in the outside wheelbrake to maintain runway alignment.

Light brake application under 100 KCAS (and all the way up to MAX brake application under 70 KCAS) will not generate enough energy to heat up the brakes to a Hot Brake situation.  Again, if DCS sims that properly.

 

Only engage NWS once at a safe taxi speed exiting the runway.

 

-- Foghorn

Edited January 4, 2021 by FoghornF16

[Mustang25]

2 hours ago, FoghornF16 said:

Oh boy.   I can gas-bag some more.

 

Please do. I think most of us here would love and appreciate as much IRL Viper knowledge as you're willing to share!