This Aircraft is Unforgiving on Landing!

[KlarSnow]

190 is still quite fast. Based on the rule of thumb I posted above, that indicates you are landing with roughly 18,000 lbs of fuel and ordnance. You may be on speed, but you are going far too fast to slow down effectively. 

Rule of thumb for airspeed that estimates on speed is 155 plus 2 knots for every thousand pounds of fuel and ordnance. So if you are at 190, thats 35 knots/2 = 17-18,000 lbs which would require roughly a 17-18,000 foot runway.

You can be on speed and exceed the nose wheel gear limit (210 knots) if you try and land with 30,000 lbs of fuel on board.

recommend shooting for something in the 160-170 knot region for on speed and it will be much more comfortable.

[skypickle]

On 7/3/2023 at 7:32 AM, KlarSnow said:

Rule of thumb is 1000 lbs of fuel and ordnance for every 1000 feet of runway you are landing on.

So if its a 9000 foot runway, combined fuel plus ordnance should be no more than 9000 lbs. Take that as your MAXIMUM landing weight, recommended is probly less than 5000 lbs combined fuel and ordnance.

You have a fuel dump switch that will dump ~1000 lbs a minute, so use that to help get down to a good landing weight if you find yourself with too much.

Fly a 20-22 unit AOA final approach with the flaps down.

Flare at 50 feet AGL using the radar altimeter and the tape on the side of the hud.

If you are floating in the flare crack the speedbrake to get the jet to settle on to the runway. Normal technique used all the time in the real thing.

 

A clean f15e (31000 lbs) needs 7500 feet. So if the formula above is used, this distance should also be enough if you are carrying up to 7500 lbs of fuel and ord. Or is that not correct?

[KlarSnow]

All of these rules of thumb are for fuel and ordnance, the aircraft base weight is taken into account in them.

Just keep in mind the USAF default minimum runway length is 8000 feet for a fighter airfield.

If you are landing on something much shorter than that even if you are super light you may run into problems stopping.

 

Edited July 4, 2023 by KlarSnow

[skypickle]

2 hours ago, KlarSnow said:

All of these rules of thumb are for fuel and ordnance, the aircraft base weight is taken into account in them.

Just keep in mind the USAF default minimum runway length is 8000 feet for a fighter airfield.

If you are landing on something much shorter than that even if you are super light you may run into problems stopping.

 

 

Understood. Just wondering what i can land with on an 8000 ft runway. A couple of sidewinders, empty bags and the two pods (tgp and nav)?

[Lord_Pyro]

I tested the other extreme. Loaded the jet up to overweight (pic 1), then took off, flew away for a bit to get some speed and height, to simulate a long approach (pic 2). During the descend its true, i had to keep the speed at around 190 to 200null (so the fpm did not flash but still remained on the landingstripnull) (Pics 3 and 4). However during short final i aimed a bit short in order to prolong my flare null (pic 5) whichnullnull allowed me to be slower than 160 on touchdown. (pic 6). 

So my point here is that its correct that you glide on 190+ as not to stall, but the touchdown can be way slower.

 

I admit i overshot the runway a bit (Pic 7) but i remind you, i was still heavier than max allowed takeoffspeed + i tried to get a pic of the aerobreaking too (in vr), which messed up my breakingprocess a bit, so maybe it would have been possible to come to a hold still on the runway.

Oh and btw my fuelreadout after landing was still aboce 31k.

null

So on final conclusion i would suggest not to only rely on numbers and books alone. We are flying a simulator and there is no better tool to experiment with things and just figure out if stuff works and or not.nullnull

[Poptart]

2 hours ago, skypickle said:

Understood. Just wondering what i can land with on an 8000 ft runway. A couple of sidewinders, empty bags and the two pods (tgp and nav)?

I've landed on a 5,000 ft runway with 11,000 lbs of fuel and a couple amraams. You just need to forget about flaring and get on the brakes very early. 

 

Edited July 4, 2023 by Poptart

[Rainmaker]

Or the fuel dump can be used as intended and all this weird stuff can be avoided. 

[Lord_Pyro]

But that takes time. If you don't want to wait for the fuel to dump, or don't can for some reason it doesn't hurt to have a skillset from outside of the normal procedures.

[KlarSnow]

Which is all fine until they model the tires exploding from your stepping on the brakes at 150 knots and that weight. You don’t want to be on the brakes at those weights and speeds, you very much want to be aero braking.

[Raven (Elysian Angel)]

3 hours ago, skypickle said:

Just wondering what i can land with on an 8000 ft runway

Earlier today I landed at Creech in NTTR (6000ft runway) with A/A weapons still on the jet (2x AIM9 2x AIM120), A/G expended and 6.5k pounds of fuel remaining. I touched down at 145KIAS, waited for the nose to drop by itself (after aerobraking) and gradually started applying wheel brakes from 100KIAS onwards, and I didn't need full brakes. I was able to stop well ahead of the end of the runway.

[Lord_Pyro]

47 minutes ago, KlarSnow said:

Which is all fine until they model the tires exploding from your stepping on the brakes at 150 knots and that weight. You don’t want to be on the brakes at those weights and speeds, you very much want to be aero braking.

Thats why you aerobrake, yes.

[Nealius]

10 hours ago, skypickle said:

Understood. Just wondering what i can land with on an 8000 ft runway. A couple of sidewinders, empty bags and the two pods (tgp and nav)?

I've been regularly landing on ~7,000ft runways with up to 3xAIM120, 1xAIM9, Nav/TGP, empty bags, and 3000-4000lbs gas. 

[Ignition]

10 hours ago, Lord_Pyro said:

I tested the other extreme. Loaded the jet up to overweight (pic 1), then took off, flew away for a bit to get some speed and height, to simulate a long approach (pic 2). During the descend its true, i had to keep the speed at around 190 to 200null (so the fpm did not flash but still remained on the landingstripnull) (Pics 3 and 4). However during short final i aimed a bit short in order to prolong my flare null (pic 5) whichnullnull allowed me to be slower than 160 on touchdown. (pic 6). 

So my point here is that its correct that you glide on 190+ as not to stall, but the touchdown can be way slower.

 

I admit i overshot the runway a bit (Pic 7) but i remind you, i was still heavier than max allowed takeoffspeed + i tried to get a pic of the aerobreaking too (in vr), which messed up my breakingprocess a bit, so maybe it would have been possible to come to a hold still on the runway.

Oh and btw my fuelreadout after landing was still aboce 31k.

null

So on final conclusion i would suggest not to only rely on numbers and books alone. We are flying a simulator and there is no better tool to experiment with things and just figure out if stuff works and or not.nullnull

(from what I can see on screenshots) You were off glide slope by a quite big margin! Your glide seems a litle slow and you overshoot the touch down AoA also.
 

"but the touchdown can be way slower."

That's ground effect.

[Lord_Pyro]

Going slow was the point of the whole exercise. And for touchdown aoa, i dont recall the exact number (it changed constantly anyway) but i did not tailstrike (which i believe starts somewhere around 26/27 deg) so its fine by me.

 

About the glideslope part - i let the plane settle down on where it wanted to be. Trimmed for a steady descent, almost hands off stick, so i just needed to play with the thrust a bit. I like it that way, its smooth

[Holbeach]

F-15E Max landing weight is 81000lb.

T/O at that weight, rotate at 167 kts.

Landing Approach speed at 80000lb is 222kts 21 units.

Landing distance over 50' is 11000' with aero braking, including airbrake. Zero wind, 20C.

Max touchdown at 240 fpm.

Try Mozdok for circuit practice, recommended wide at this weight. 12160' runway.

So far, landings at this weight and sticking to the numbers, have been between 9910' and 11126', with the qccasional jaunt into the field at the end, when I balls up.

Great fun!

..

Edited July 5, 2023 by Holbeach

[jaylw314]

FWIW the recommended book 'minimum run' landing is apparently trimmed to AOA of 23, 'dragging it in' with a more shallow approach angle of 1.5-2 deg, and on the wheelbrakes immediately after touchdown, as long as the weight is under 45,000 lbs.  When I tried this, there's some airframe buffet that starts around AOA 23, not sure if that is accurate or a little early, but it makes it a little uncomfortable.

OTOH, the landing distance chart goes all the way up to weights of 80,000 lbs with this technique, and shows a landing distance in ideal conditions of about 12,000' (ouch).  The fact that they've tested it suggests doing so probably doesn't automatically blow your tires, but I'm sure crew chiefs shudder at the thought.

In any case, in DCS you should feel free to hit the wheelbrakes at touchdown, especially for some of the shorter runways.  If you have any kind of mechanical sympathy, though, that will be challenging

 

Edited July 5, 2023 by jaylw314

[Avio]

I noticed coming in on short final at 22 AOA or so, the flight path marker gets very likely to disappear below the HUD (flashing) during the flare. Is this normal and correct in the real jet?

Also, in the overhead break landing, the manual says on downwind (at 1600 AGL) keep the runway sight picture between the wing tip and outer rack. Isn't that too close? Wouldn't keeping a small gap between wing tip and runway allow for a less stall-prone break turn through base to final? (I mostly keep to 1500 AGL).

Found that the jet needs quite a bit of increased power and tight turn on base turn just to keep it a safe margin from stall.

 

[Tenkom]

The ground effect is very strong compared to other jets so I often flare too much and end up landing much later than I intended. Never had a problem with stopping however. Good brakes. Except maybe the last 10-20 knots before stopping takes longer than I expect. Almost rear ended some guy during taxiing because it took longer to come to a stop than I thought.

[Sarge55]

Someone earlier in the thread said they crack the airbrake open in the flare if they are floating during the flare to make it settle to the runway. 
I tried that and it worked quite nicely. 

[jaylw314]

6 hours ago, Tenkom said:

The ground effect is very strong compared to other jets so I often flare too much and end up landing much later than I intended. Never had a problem with stopping however. Good brakes. Except maybe the last 10-20 knots before stopping takes longer than I expect. Almost rear ended some guy during taxiing because it took longer to come to a stop than I thought.

20 AOA is just about 10-11 degrees between the VV and the W in the HUD.  Since you're usually approaching at a 2.5-3 degree descent, that means during the entire roundout, flare and aerobraking, you need to only get the nose up about 3-5 degrees, it's not a huge pitch-up move, it's pretty subtle.

[GGTharos]

On 7/5/2023 at 12:02 PM, jaylw314 said:

OTOH, the landing distance chart goes all the way up to weights of 80,000 lbs with this technique, and shows a landing distance in ideal conditions of about 12,000' (ouch).  The fact that they've tested it suggests doing so probably doesn't automatically blow your tires, but I'm sure crew chiefs shudder at the thought.

It does automatically blow your tires.  While it might not blow them on the spot, the aircraft will be taken to a hot-brakes ramp and no one will be approaching from the side of the wheels until a certain amount has passed for them to cool, or more likely just explode.   The situation you describe isn't on the margins in a sort of 'maybe they will maybe they won't' deal, the wheels will explode and such things have killed people IRL.  You're right though, DCS does not model this or any kind of tyre wear so whatever

On 7/5/2023 at 1:27 AM, Lord_Pyro said:

About the glideslope part - i let the plane settle down on where it wanted to be. Trimmed for a steady descent, almost hands off stick, so i just needed to play with the thrust a bit. I like it that way, its smooth

It's supposed to settle where you want it to be   Your glideslope is bad, resulting in a more dangerous and potentially later flare, and a longer ground-run.  It is a good part of the reason you overran the runway   

[jaylw314]

5 minutes ago, GGTharos said:

It does automatically blow your tires.  While it might not blow them on the spot, the aircraft will be taken to a hot-brakes ramp and no one will be approaching from the side of the wheels until a certain amount has passed for them to cool, or more likely just explode.   The situation you describe isn't on the margins in a sort of 'maybe they will maybe they won't' deal, the wheels will explode and such things have killed people IRL.  You're right though, DCS does not model this or any kind of tyre wear so whatever

Yeah, I was speaking more in terms of SOMEBODY having to test that at 80,000 lbs at least once.  Clearly, the poor guy was able to get it done without exploding under ideal circumstances (maybe they had firehoses dousing the wheels), but I'm sure there was some clenching involved  

[GGTharos]

Yep, it depends - I don't know the exact procedures but hosing down the wheels can be a thing.  You m ight also be stuck in the cockpit for an hour (as I understand it, the exploding part is basically the wheel halves that the tyre is mounted on separating, so those metal ... disks shall we say, blow out to the sides).  So you just stay out of the way of that until it's safe.

The determination can also be done mathematically since you can calculate the energy that is imparted during braking from the friction.

[Iron Sights]

Maybe at some point we can a landing Weight and speed chart. I have not had any problems on landings, I bleed speed with the air brake as I touchdown and aero brake. I have landed with a full bomb load. Burning off fuel is key, 30,000 lbs of fuel is a lot, so I just run the afterburners or leave the bags off for shorter hops and set fuel to what you need for the mission, plus 30 minutes flight time.

[jaylw314]

As far as I can tell, landing at 80,000 lbs with immediate braking results in 'wheel damage and brake fires possible,' so it's not an automatic explosion.  I'm guessing that does not encapsulate the clenching that would be involved, though 

If you aerobrake down to 110 knots or so before braking, you're supposed to be in the clear, which is pretty mind-boggling to me.

2 hours ago, Iron Sights said:

Maybe at some point we can a landing Weight and speed chart. I have not had any problems on landings, I bleed speed with the air brake as I touchdown and aero brake. I have landed with a full bomb load. Burning off fuel is key, 30,000 lbs of fuel is a lot, so I just run the afterburners or leave the bags off for shorter hops and set fuel to what you need for the mission, plus 30 minutes flight time.

You have the fuel dumps too

Edited July 6, 2023 by jaylw314