Aerodynamic Braking During Heavy Landing

[Terzi]

Hello,

When the jet is loaded with 2 external tanks and the fuel is almost full both internal and external, aerodynamic braking after touchdown is impossible and the nose will drop down almost right after you land without touching the wheel brakes. Having some AG ordnance would make it even worse.

I checked from external view that the stabs are fully trying to raise the nose up which should be the case. But the nose cannot keep ~10 degrees until slowing down to  ~100 knots.

Any ideas how to do it properly? Am I missing something? Can someone try and confirm the same issue?

Normally that kind of payload and wheel braking for that distance would likely cause hot braking which can destroy the brakes and is not yet simulated in DCS.

[Moonshine]

tried it with different amounts of fuel.
while i cant seem to replicate it, i do feel like the nose drops 10-15kts earlier than previously.

Landing_2xBag_8000lbs.trk Landing_2xBag_6000lbs.trk Landing_2xBag_3000lbs.trk

[Grodin]

7 hours ago, Terzi said:

Hello,

When the jet is loaded with 2 external tanks and the fuel is almost full both internal and external, aerodynamic braking after touchdown is impossible and the nose will drop down almost right after you land without touching the wheel brakes. Having some AG ordnance would make it even worse.

I checked from external view that the stabs are fully trying to raise the nose up which should be the case. But the nose cannot keep ~10 degrees until slowing down to  ~100 knots.

Any ideas how to do it properly? Am I missing something? Can someone try and confirm the same issue?

Normally that kind of payload and wheel braking for that distance would likely cause hot braking which can destroy the brakes and is not yet simulated in DCS.

Only thing i could think of is that maybe you are already slow enough when touching down that the nose wont stay up? Sure it does fall down a bit sooner with heavy weight, but i can always keep the nose up atleast for a while even if landing with max load, but i land at 11 AoA instead of the 13 so i might be coming in a bit faster than you.

[Machalot]

Are you within valid landing parameters with that much weight on board?  I.e. maybe the jet is not designed to land that heavy.

[SickSidewinder9]

You're flaring before you land, right?

[Nealius]

I don't think the jet is designed to land heavy. IIRC typical landing fuel is 2,000lbs, maybe +extra for alternate.

Edited October 24, 2023 by Nealius

[Grodin]

On 10/21/2023 at 6:55 AM, Machalot said:

Are you within valid landing parameters with that much weight on board?  I.e. maybe the jet is not designed to land that heavy.

 

6 hours ago, Nealius said:

I don't think the jet is designed to land heavy. IIRC typical landing fuel is 2,000lbs, maybe +extra for alternate.

 

Unlikely because any weight you can take off with you can also land with, there is no seperate landing weight limitation.

[Lace]

^^^  Correct, there is no MLW for the Viper.  If you can take off with it, you can land with it.

OP - chances are you are too steep in your approach.  It is possible to be on-speed/on-AoA, but above glideslope which will result in an excessive rate of descent.  Don't slam it into the runway, and use a small amount of flare just before touchdown to arrest the landing.  I usually get the slightest side-to-side rock as one wheel touches first (depending on crosswind component), but the nose won't drop if you are gentle enough. 

[Nealius]

7 hours ago, Grodin said:

Unlikely because any weight you can take off with you can also land with, there is no seperate landing weight limitation.

6 hours ago, Lace said:

^^^  Correct, there is no MLW for the Viper.  If you can take off with it, you can land with it.

This is correct only if you have enough runway to work with.

Reaching way back in my hippocampus when I flew with a dedicated group of Viper guys who had a couple SMEs in there, real-world planning was--as relayed to us--2,000lbs landing fuel + fuel for alternate. Flight/mission fuel was always calculated from there.

My point being, even if it doesn't have a MLW you shouldn't be landing heavy because you won't stop in time from aforementioned inability to aerobrake at heavy weights (even just TPOD and HTS have an affect on this when lightly loaded). It's the same with the Mudhen too. Both have crappy brakes. Mover attested to this in one of his videos somewhat recently when talking with Wombat and Gonky about fuel dump and how the Viper doesn't have dump, so in cases where they need to lighten up before landing they would open the speed brakes and plug in afterburner to get lighter (IIRC in situations where they had to abort mission shortly after takeoff). So yeah, even if there is no MLW, there is an operational limit they go by, probably determined by runway length/conditions if I had to guess. 

We're in "Doctor it hurts when I do this. Well, stop doing that." territory. 

Edited October 24, 2023 by Nealius

[Lace]

17 minutes ago, Nealius said:

This is correct only if you have enough runway to work with.

Reaching way back in my hippocampus when I flew with a dedicated group of Viper guys who had a couple SMEs in there, real-world planning was--as relayed to us--2,000lbs landing fuel + fuel for alternate. Flight/mission fuel was always calculated from there.

My point being, even if it doesn't have a MLW you shouldn't be landing heavy because you won't stop in time from aforementioned inability to aerobrake at heavy weights (even just TPOD and HTS have an affect on this when lightly loaded). It's the same with the Mudhen too. Both have crappy brakes. Mover attested to this in one of his videos somewhat recently when talking with Wombat and Gonky about fuel dump and how the Viper doesn't have dump, so in cases where they need to lighten up before landing they would open the speed brakes and plug in afterburner to get lighter. So yeah, even if there is no MLW, there is an operational limit they go by, probably determined by runway length/conditions if I had to guess.  

 

LDA is always a factor with any flight planning (which begs the question - why are you trying to land on a runway which is too short?), but the fact is most people just aren't doing it right.  I can put the viper down and have it stopped before the intersection at most ADs, and have never felt like I was going to run out of room.  Fly the right landing technique and you will not have a problem, none of them have 'crappy brakes' if you land correctly (but if you are trying to compensate for a bad approach and landing with brakes, well you might have an issue).  If you can't, well there is no shame in dumping the ordnance before landing and boards and burners is always an option - not as if you have to justify it to anyone and the virtual ammunition depots are always full.

[Hiob]

My tip would be a steep approach, too. IIRC the Landing cue line in the Viper is at a 2,5 degree glide slope, so even flatter than the usual 3 degrees. That would suggest to me that the Viper is meant for a rather shallow approach. Looking at the flimsy undercarriage, and the unlimited LW (didn't know that), that makes kind of sense.

[Nealius]

11 hours ago, Lace said:

LDA is always a factor with any flight planning (which begs the question - why are you trying to land on a runway which is too short?), but the fact is most people just aren't doing it right.  I can put the viper down and have it stopped before the intersection at most ADs, and have never felt like I was going to run out of room.  Fly the right landing technique and you will not have a problem, none of them have 'crappy brakes' if you land correctly (but if you are trying to compensate for a bad approach and landing with brakes, well you might have an issue).  If you can't, well there is no shame in dumping the ordnance before landing and boards and burners is always an option - not as if you have to justify it to anyone and the virtual ammunition depots are always full.

You're completely missing the point, moving the goalpost, and getting carried away with assumptions about poor landing technique, or trying to land on runways that are too short with zero evidence to lead to such judgements. Given the evidence supplied by OP, the only logical and reasonable conclusion is that he's simply too heavy when landing. It's that bloody simple. No point in complicating it or disparaging others' "technique" when you have no evidence to support that critique until OP supplies a video or track file of one of his landings.

Edited October 25, 2023 by Nealius

[Lace]

4 hours ago, Nealius said:

You're completely missing the point, moving the goalpost, and getting carried away with assumptions about poor landing technique, or trying to land on runways that are too short with zero evidence to lead to such judgements. Given the evidence supplied by OP, the only logical and reasonable conclusion is that he's simply too heavy when landing. It's that bloody simple. No point in complicating it or disparaging others' "technique" when you have no evidence to support that critique until OP supplies a video or track file of one of his landings.

 

No, the OP is probably too steep, or too slow, which is why they cant arrest the rate the nose sinks.  By definition you can't be 'too heavy' to land a Viper.

Like any technique, it just takes a bit of practice, that's all.  There is no need to get all defensive.

[Grodin]

18 hours ago, Nealius said:

You're completely missing the point, moving the goalpost, and getting carried away with assumptions about poor landing technique, or trying to land on runways that are too short with zero evidence to lead to such judgements. Given the evidence supplied by OP, the only logical and reasonable conclusion is that he's simply too heavy when landing. It's that bloody simple. No point in complicating it or disparaging others' "technique" when you have no evidence to support that critique until OP supplies a video or track file of one of his landings.

 

Considering that the landings work perfectly fine for the rest of us the only logical conclusion is that either a) Something wrong with the technique or b) something wrong with the game. I'm unable to reproduce a situation where the nose wont stay up no matter how heavy i load the plane if i have the correct AoA and glide path.

[Theodore42]

The F-16 has a tail-hook for just such emergencies, right?

Probably just the center of gravity with full fuel plus external tanks makes aerobraking unreasonable, even if the landing gear can take landing at 100% of take off weight.

When testing I noticed taking off the TGP gets more aerobraking distance when landing heavy.

[Terzi]

I am not slamming the jet onto the runway or doing very high AoA landing.

I can keep the nose up for a very short time, but not down to 100 knots or anywhere close to it. I will try to make a video/track replay with the control axis displayed. I don't think the problem is my way of landing. Its just the jet will tend to put the nose down even if I am not touching the brakes yet after touchdown.

[NaOH1]

Is aerodynamic breaking modeled yet? I've read some people say it has little effect at this point.

[Theodore42]

7 hours ago, NaOH1 said:

Is aerodynamic breaking modeled yet? I've read some people say it has little effect at this point.

Ya for sure. Keeping the pitch above 12 degrees during landing slows you down a lot.

It's so effective that people in this thread are wondering why you can't aerobrake under 140 knots when the Viper is really heavy.

1. The manual (irl) says it's ok to land at the max take off weight. BUT you NEED to aerobrake a LOT to get the Viper stopped while it's really heavy because the brakes aren't that great

AND

2. In the DCS Viper, you can't aerobrake long enough to slow down enough to stop before the end of the runway that the irl manual says is long enough to safely operate from

THEREFORE

Either the Viper flight model is wrong and should allow for the ability to aerobrake down to a slower speed OR there are procedures concerning landing near max weight that we don't know. [EDIT: or we all suck at landing]

I've seen a video of an F-16 (Spanish maybe?) Taking off with wing tanks and then immediately landing due to a problem. I couldn't find it when I went looking for it though 

Edited November 2, 2023 by Theodore42

[smire666]

I've landed with a fully-loaded Viper at "famous" Kobuleti and have used the entire Runway-length. I was able to aerobrake until approx. 120kts.

[bbrz]

On 10/27/2023 at 12:34 PM, Terzi said:

I can keep the nose up for a very short time, but not down to 100 knots or anywhere close to it. 

Since touchdown should occur at the same AoA, regardless of weight, you should check if the external loads you are carrying are shifting the CG forward.

Even a slight fwd shift would noticeable increase the pitch down tendency.

Another factor might be thrust reduction. If you reduce thrust to idle before touchdown, the speed will decrease faster at higher weight, hence touchdown might occur at a higher AoA.

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Edited December 3, 2023 by bbrz

[Braunn]

Nose will drop after aerobraking when its ready to. Theres no set speed where it should go down. 

If you cant hold the nose up w full elevator deflection.... guess what, youre not fast enough. And shes ready to wheel brake a little before rwy exit.

[TobiasA]

The problem is that you will get a tailscrape at about 13-14 degrees in DCS which is wrong, it should be 15 with the brakes in landing position.