Fuel Load critical for safe landing in DCS F-16

[ruddy122]

New Pilots,

 

Don't try to come back to base with more than 6000 lbs in the F-16 tanks unless you could land on a 10000 ft runway or more

 

More fuel gives you a higher landing speed and longer distance to stop

 

So short runways like Senaki, Khasab, and Ramat David can be tricky

 

Try to come back with as little fuel that's safe of course to land on short runways or use a runway that can accomodate you landing heavier

 

A good gouge by a Former Viper Instructor is quick math

 

Landing Speed = 140 + 4 for every thousand pounds of fuel

 

For example you are going to land with 6000 lbs of fuel what is my landing speed?

 

Well it is 164 which is 140 + 6*4=164

 

Happy Flying

[Lace]

Or just fly by AoA.  Correct AoA, correct landing speed for current aircraft weight.

[ruddy122]

I fly AOA, its the stopping part that is a challenge in the DCS: F-16

Aerobrake is fun but I'm slowly figuring out why I was hitting the ILS Antenna on rollout

[Lace]

If you are having stopping problems you are not aerobraking or are trying to drop it into farm strips.  It's really not that hard to land the Viper.  Aero to 100, wheel brakes from 70-taxy speed.

[ruddy122]

The KC-10A used airspeed not AOA

 

We told students pitch for 4.5 on the ILS and 10% of your weight + N1 and Vref+5 you will be super stable on the ILS

Maybe I'm not pitching enough on Aerobraking

 

The book (Dash One) says 13

 

I could land easily in Beirut

 

Ramat David next

[Lace]

Most aircraft use airspeed rather than AoA for the simple reason that they don't have AoA indication.  AoA is the only real defining factor in lift generation.  The reason the approach speed changes with weight is to arrive at the correct AoA.

 

You don't need to overdo the aerobraking pitch up either, or you risk a nozzle or airbrake strike, 10-13deg works ok, you just need to hold it for as long as the nose will remain controllable.

[Maxthrust]

6000 lbs seems a lot fuel to land with when compared to Mig-21's 1200 lbs (700 L) fuel reserve if not landing overweight. Actually you should be able to fly from Anapa to Batumi with 6000 lbs, why would you carry so much dead weight? 

Edited April 30, 2021 by Maxthrust

[Lace]

2 hours ago, Maxthrust said:

6000 lbs seems a lot fuel to land with when compared to Mig-21's 1200 lbs (700 L) fuel reserve if not landing overweight. Actually you should be able to fly from Anapa to Batumi with 6000 lbs, why would you carry so much dead weight? 

 

 

There is no max landing weight for the Viper.  If you can take off with it, you can land with it.

[ruddy122]

Curious does the real viper tip that easily or is it a DCS thing


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I know it has a high CG and the gear is nowhere near as beefy as the Hornet


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[Maxthrust]

 

24 minutes ago, Lace said:

 

There is no max landing weight for the Viper.  If you can take off with it, you can land with it.

 

That's impressive, though doesn't mean you can stop before the end!

 

I wish DCS simulated brake energy limitations, this would add a lot to realism and prevent people landing at the maximum takeoff weight.

[Lace]

9 hours ago, ruddy122 said:

Curious does the real viper tip that easily or is it a DCS thing
 

I know it has a high CG and the gear is nowhere near as beefy as the Hornet
 

 

You mean like this?

 

 

It does happen, but IRL there are procedures to follow and taxy speed limits so it is almost certainly far less common than an airquaker hurrying back to the runway after another hot pit rearm.  The info I have states taxy at 20ish, turns at 10 (from the DED INS G/S).

[TobiasA]

vor 16 Stunden schrieb ruddy122:

New Pilots,

 

Don't try to come back to base with more than 6000 lbs in the F-16 tanks unless you could land on a 10000 ft runway or more

 

More fuel gives you a higher landing speed and longer distance to stop

 

So short runways like Senaki, Khasab, and Ramat David can be tricky

 

Try to come back with as little fuel that's safe of course to land on short runways or use a runway that can accomodate you landing heavier

 

A good gouge by a Former Viper Instructor is quick math

 

Landing Speed = 140 + 4 for every thousand pounds of fuel

 

For example you are going to land with 6000 lbs of fuel what is my landing speed?

 

Well it is 164 which is 140 + 6*4=164

 

Happy Flying

 

We don't fly airspeed in the F-16. We fly AOA.

There are charts for landing distance in RL manuals (from HAF) but they do not apply to DCS since the FM is not according to the real thing. So you will always have longer landing distances in DCS until the flight model gets fixed. That is the main part of your problem with stopping. The current F-16 has landing speeds of up to 175kts due to that issue, leading to extremely long stopping distances.

During aerobraking, try to keep the AOA near 12-13°. Lower the nose at 100kts. When the nose comes down, extend speedbrakes fully and pull the stick full aft to use the elevators as an additional speed brake.

[SpaceMonkey037]

17 hours ago, ruddy122 said:

New Pilots,

 

Don't try to come back to base with more than 6000 lbs in the F-16 tanks unless you could land on a 10000 ft runway or more

 

More fuel gives you a higher landing speed and longer distance to stop

 

So short runways like Senaki, Khasab, and Ramat David can be tricky

 

Try to come back with as little fuel that's safe of course to land on short runways or use a runway that can accomodate you landing heavier

 

A good gouge by a Former Viper Instructor is quick math

 

Landing Speed = 140 + 4 for every thousand pounds of fuel

 

For example you are going to land with 6000 lbs of fuel what is my landing speed?

 

Well it is 164 which is 140 + 6*4=164

 

Happy Flying

Your calculations are slightly simplified, the true base number is 138, not 140. A very minor thing but noteworthy nonetheless, it is important to mention that this is for all weight, not just fuel. If you have bombs etc. those will have an effect on landing speed as well. Landing speed is only used as a reference to what speed you're supposed to aim for, and a backup in case the AOA probes malfunction. When flying a normal approach you use AOA, not airspeed. 8000 feet of runway is more than sufficient for most loadouts, and you will only ever reach issues when flying with loadouts over 34000 pounds ground weight. 

As for the actual landing procedure:
At 12-15nm away from the runway lower the landing gear under 300 knots and extend the speedbrakes. Once lined up with the runway intercept a 3 degree glide slope. This can be achieved by using the dotted attitude line that appears in the HUD with gear down shows you 2.5 degrees nose down attitude. Line up the dotted line slightly above the runway threshold and place the flight path marker on the threshold. Doing this will result in a 3 degrees. Then simply fly for 11 degrees AOA. 11 degrees AOA is preferred of 13, as 13 degrees proved to give too little room for error when flaring (11 degrees is achieved by placing the flight path marker on the top of the AOA bracket) Fly the 11 degree glide slope until you’re at approximately 2 seconds from impact when following the 3 degree glide slope. Here you will pull back on the stick, idle the throttle now, or a few bits later if you are heavy. When touching down you’re not trying to smash the plane down, but also not try to just kiss the runway. Smashy smashy style is self-explanatory as that will destroy stuff, however landing too softly increases the chances of aquaplaning with wet runways. For this reason, ALWAYS try to firmly place the aircraft down, not too soft not too hard. Even if the runway is dry it is a good habit to land it firmly. 

Once you’ve touched down slightly (very slightly) lower the nose to avoid floating back up into the air. Then a split second later pull back on the stick and aim for 13 degrees AOA. Do not exceed 15 degrees as you will tail strike above this. Keep the aerobraking for as long as possible. If your runway is long enough keep your nose up until it falls down by itself, once the nose wheel has touch the ground fully extend the speedbrakes by holding the speedbrake switch aft and give full back stick pressure to increase the drag of the horizontal tail. Keep in mind that there is no reason to lower the nose “manually” if you’re not going to brake immediately after the nose wheel as touched the runway. For shorter runways a shorter stop might be needed. Here you might need to lower the nose at 100 knots and apply brakes. For absolute maximum stopping “power” you will want to aerobrake and apply full brakes while aerobraking. You will then lower the nose at 100 knots, keeping full brakes, full back stick pressure and full speedbrake once the nose wheel as touched the runway. Hot brakes is another consideration when landing. If heavy use of wheel brakes is necessary you risk getting hot brakes. Hot brakes can destroy the hydraulics in the wheel brakes and might lead to fires, so avoid this if possible. Unless you have a really light loadout (4k pounds and belove) you won’t get hot brakes no matter what you do. If you brake at anything under 80 knots you pretty much won't get hot brakes unless you have a heavy loadout. Anything under 7k pounds will be just fine. You can calculate your current weight by estimating each missile to 250 pounds and bombs to.. whatever bombs you have, and then of course adding on the amount of fuel left as it is calculated in pounds. Generally you want to avoid using brakes if you don't need to, as you will have to change out the brake pads more often, however changing brake pads is a lot cheaper than changing the plane. It's better to use them rather then not if you're unsure about the braking distance.

As for the actual braking technique, think like this: No matter the braking power you will always have the same amount of heat build up, meaning that it is better to brake hard over a short amount of time rather than braking softly over a long time. Same goes for taxing. With hot brakes i mean red glowing hot brakes. The only way to actually confirm that you have them is if a flight member can spot the brakes.

Try to stop with 2000 feet of runway remaining, under normal conditions this will be sufficient takeoff distance for sub-32 000 pound loadouts in MAX AB, so if you need to go around you have the possibility to do so. For an 8000 feet runway you would stop 3/4 of the way down the runway.

[mobua]

2 hours ago, SpaceMonkey037 said:

Your calculations are slightly simplified, the true base number is 138, not 140. A very minor thing but noteworthy nonetheless, it is important to mention that this is for all weight, not just fuel. If you have bombs etc. those will have an effect on landing speed as well. Landing speed is only used as a reference to what speed you're supposed to aim for, and a backup in case the AOA probes malfunction. When flying a normal approach you use AOA, not airspeed. 8000 feet of runway is more than sufficient for most loadouts, and you will only ever reach issues when flying with loadouts over 34000 pounds ground weight. 

As for the actual landing procedure:
At 12-15nm away from the runway lower the landing gear under 300 knots and extend the speedbrakes. Once lined up with the runway intercept a 3 degree glide slope. This can be achieved by using the dotted attitude line that appears in the HUD with gear down shows you 2.5 degrees nose down attitude. Line up the dotted line slightly above the runway threshold and place the flight path marker on the threshold. Doing this will result in a 3 degrees. Then simply fly for 11 degrees AOA. 11 degrees AOA is preferred of 13, as 13 degrees proved to give too little room for error when flaring (11 degrees is achieved by placing the flight path marker on the top of the AOA bracket) Fly the 11 degree glide slope until you’re at approximately 2 seconds from impact when following the 3 degree glide slope. Here you will pull back on the stick, idle the throttle now, or a few bits later if you are heavy. When touching down you’re not trying to smash the plane down, but also not try to just kiss the runway. Smashy smashy style is self-explanatory as that will destroy stuff, however landing too softly increases the chances of aquaplaning with wet runways. For this reason, ALWAYS try to firmly place the aircraft down, not too soft not too hard. Even if the runway is dry it is a good habit to land it firmly. 

Once you’ve touched down slightly (very slightly) lower the nose to avoid floating back up into the air. Then a split second later pull back on the stick and aim for 13 degrees AOA. Do not exceed 15 degrees as you will tail strike above this. Keep the aerobraking for as long as possible. If your runway is long enough keep your nose up until it falls down by itself, once the nose wheel has touch the ground fully extend the speedbrakes by holding the speedbrake switch aft and give full back stick pressure to increase the drag of the horizontal tail. Keep in mind that there is no reason to lower the nose “manually” if you’re not going to brake immediately after the nose wheel as touched the runway. For shorter runways a shorter stop might be needed. Here you might need to lower the nose at 100 knots and apply brakes. For absolute maximum stopping “power” you will want to aerobrake and apply full brakes while aerobraking. You will then lower the nose at 100 knots, keeping full brakes, full back stick pressure and full speedbrake once the nose wheel as touched the runway. Hot brakes is another consideration when landing. If heavy use of wheel brakes is necessary you risk getting hot brakes. Hot brakes can destroy the hydraulics in the wheel brakes and might lead to fires, so avoid this if possible. Unless you have a really light loadout (4k pounds and belove) you won’t get hot brakes no matter what you do. If you brake at anything under 80 knots you pretty much won't get hot brakes unless you have a heavy loadout. Anything under 7k pounds will be just fine. You can calculate your current weight by estimating each missile to 250 pounds and bombs to.. whatever bombs you have, and then of course adding on the amount of fuel left as it is calculated in pounds. Generally you want to avoid using brakes if you don't need to, as you will have to change out the brake pads more often, however changing brake pads is a lot cheaper than changing the plane. It's better to use them rather then not if you're unsure about the braking distance.

As for the actual braking technique, think like this: No matter the braking power you will always have the same amount of heat build up, meaning that it is better to brake hard over a short amount of time rather than braking softly over a long time. Same goes for taxing. With hot brakes i mean red glowing hot brakes. The only way to actually confirm that you have them is if a flight member can spot the brakes.

Try to stop with 2000 feet of runway remaining, under normal conditions this will be sufficient takeoff distance for sub-32 000 pound loadouts in MAX AB, so if you need to go around you have the possibility to do so. For an 8000 feet runway you would stop 3/4 of the way down the runway.

Gold dust, thanks for laying it out clearly. I consider myself capable in the DCS F-16 but there are some things to take away from this.

 

Again, thanks!

[ruddy122]

Many thanks

11 AOA on approach nice

Greater than 175 landing expect longer landing distance

Aerobrake key 13 AOA optimum 15 run risk of damaging something important like your nozzle or speedbrake

I love the viper wish ED fixed the viper vs the Hornet but I’m an AF guy

Lot simpler avionics wise than the Hornet


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[ruddy122]

Don’t taxi too fast or you’ll flip your viper and your Squadron Commander won’t be happy to see you


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[Jester2138]

On 4/30/2021 at 9:42 AM, Lace said:

Most aircraft use airspeed rather than AoA for the simple reason that they don't have AoA indication.

Correction: most NON-MILITARY aircraft use airspeed. Military pilots are trained to fly by AoA by-and-large.

[Lace]

44 minutes ago, Jester2138 said:

Correction: most NON-MILITARY aircraft use airspeed. Military pilots are trained to fly by AoA by-and-large.

 

Which is a much better way.  There is no such thing as a stalling speed, only a stalling AoA. Fortunately AoA probes and their integration into GA glass cockpits is becoming cheaper and more common these days.

[ruddy122]

AOA is more intuitive than asking an FMS or checklist of Vref


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[Dee-Jay]

https://youtu.be/2wlvpJLcf-A

[Nealius]

On 5/1/2021 at 6:35 PM, SpaceMonkey037 said:

you will only ever reach issues when flying with loadouts over 34000 pounds ground weight. 

 

At 32,000lbs GW I'm finding it impossible to aerobrake. The nose comes down at 150kts with full aft stick. With lighter, but still heavy GW (28,000lbs) the nose will come down at 110kts with full aft stick. I understand the "proper" procedure to aerobrake until 100kts, but I have so far been unable to do so. Is this expected behavior when landing heavy, assuming everything else in the landing is more or less correct (on-speed AoA, boards out, TD point, etc.)?

Edited June 29, 2021 by Nealius

[Spurts]

By default the Center of Gravity CG is in front of the MLG by enough that you can be so nose high on the ground that your tail scrapes and the nose will still come down.  If the CG was further aft than this once you aerobrake to a certain point the jet would rest like this until the back is jacked up.

 

The horizontal tail at full deflection will make a "fixed" about of downforce on the tail at any given speed.  So at any speed there is only so much "force" holding the nose up, and this force increases as a square of the speed. *Edit* or I should say decreases as the square of the speed since we are slowing down.

 

The heavier the plane, the more force is pulling the nose down.  This force does not change with speed.  Once the nose down force exceeds the nose up force the nose will begin to drop.  So a heavier plane will pull the nose down at a higher speed than a lighter plane.  If you have stores that move the CG forward (most do) then even at the same notional weight the nose will pull down harder and the nose will come down at a higher speed.  

 

At 32,000lb you are both heavy and have nose heavy stores on board.  Both things will pull the nose down.

 

*Edit2*  This is literally the same physics that doesn't let you rotate on takeoff at the same speed for all configurations and weights.

Edited June 29, 2021 by Spurts

[Theodore42]

@Spurts you seem familiar with this kind of thing and I've always wondered,

 

How does using your wheel brakes during aerobraking affect the aircraft?

 

My intuition suggests that the rotational inertia from applying the wheel brakes would be the end of any aerobraking, and I can't really imagine having the CG up a little closer to the nose would have MORE of an impact...

But I've read multiple sources stating this is part of the short field landing procedure. Do you know anything about this? In DCS (the last time a tried this), applying wheel brakes during aerobraking didn't affect aircraft pitch. Is there something going on physics-wise that would make this the case?

 

Would it be more accurately modeled if you had to increase elevator deflection when using wheel brakes during aerobraking? Or maybe the FLCS does that for you? Although I haven't read anything that suggests that, and original sources usually drop some acronyms when the FLCS is doing something behind the pilots back.

[Spurts]

7 minutes ago, Theodore42 said:

@Spurts you seem familiar with this kind of thing and I've always wondered,

 

How does using your wheel brakes during aerobraking affect the aircraft?

 

My intuition suggests that the rotational inertia from applying the wheel brakes would be the end of any aerobraking, and I can't really imagine having the CG up a little closer to the nose would have MORE of an impact...

But I've read multiple sources stating this is part of the short field landing procedure. Do you know anything about this? In DCS (the last time a tried this), applying wheel brakes during aerobraking didn't affect aircraft pitch. Is there something going on physics-wise that would make this the case?

 

Would it be more accurately modeled if you had to increase elevator deflection when using wheel brakes during aerobraking? Or maybe the FLCS does that for you? Although I haven't read anything that suggests that, and original sources usually drop some acronyms when the FLCS is doing something behind the pilots back.

I never use the brakes during aerobraking so I can't say what the sim is doing, but I can go over the physics of what SHOULD happen.

 

You are spot on that the braking drag below the CG will pull the nose down.  The further forward the CG is in a nose up attitude the longer the moment arm for the braking force to act on, so it would increase the nose down moment (weather this is enough to be noticeable I cannot say right now).  An increase in stab deflection would counter the nose down, assuming you still have stick travel available.  One thing to keep in mind is that early in the aerobrake, when speed is still high, is that the wheels have very little weight on them and thus they can only provide a small amount of brake force drag.  The wings are still holding up the plane. 

 

Landing a taildragger like the P-51, you hold max aft stick and then as much brake as you can without flipping over the gear and smashing the prop.  The same balance of brake moment and tail moment, but when you do that you are unloading the wing and putting weight on the wheels.

 

Landing the F-15 is much the same as the F-16.

 

Landing the F/A-18 you can't get the nose up when at landing speeds due to the gear design so to minimize landing roll you need to actually pull the flaps up to get all the weight on the wheels for braking.

 

The F-14 has the shortest stopping distance of any 4th gen US fast jet.  This is due to lower approach speed, fantastic brakes, and that the moment weight-on-wheels is detected the spoilers deploy and dump all the lift off the wings.  Max weight on wheels for max braking drag in addition to aerodrag from deployed spoilers, flaps, airbrake, and in my case fully deflected stabilator.

 

In the Harrier you just cut power and laugh.

 

 

[TobiasA]

It is not possible with the current flight model due to the lack of lift at the given AOA, that is also why the landing speeds are higher.