F-15C - How to apply brakes without going off the runway?

[Sweep]

Don't understand that one. How do apply brakes when the heels are on the floor?

 

"toe"brakes.*

 

*Might require excessively large feet.

[MikeMikeJuliet]

Don't understand that one. How do apply brakes when the heels are on the floor?

 

It depends on the pedals. Not all pedals allow you to do that. Mine are the Saitek Combat rudder pedals... the pedal-portion is a sort of cylinder at the "lower end" of each pedal, and the rest is the toe-brake... so I can just about break with my toes. There is no heel-stopper in the way so I can do that.

 

Now that I think about it, most pedals probably don't allow that to happen.

[SinusoidDelta]

...And on the point of crosswind. Fighters are not designed for strong crosswinds typically. Civil aircraft may, in many cases land at stronger crosswinds than a fighter jet, so no point in trying 30kt crosswind components.

 

 

Actually the F-15 had a development requirement for operation in a 30kts crosswind. And according to the -1, landing the F-15 is possible with a 30kts 90° crosswind component. Landing with a crosswind component exceeding 30kts is not recommended but it certainly doesn't say impossible.

 

Back to the DCS eagle, have you attempted a T/O or landing with a crosswind of 30kts? I haven't but the results should be interesting based on how severely it reacts to a 7kts crosswind.

 

Edited October 1, 2016 by SinusoidDelta

[Ramstein]

I am looking forward to all brand new high quality flight stick, pedals and gear, mine is cheap and worn out...

[sea2sky]

a trick is not to apply breaks continuously, but rather do it with pulses 2-3 seconds each. With a proper landing speed I count about 7-9 pulses is enough to make a nice complete stop.

[pr1malr8ge]

...And on the point of crosswind. Fighters are not designed for strong crosswinds typically. Civil aircraft may, in many cases land at stronger crosswinds than a fighter jet, so no point in trying 30kt crosswind components.

 

Not true m8.

 

 

[BSS_Sniper]

Not true m8.

 

 

 

I highly doubt that's a full 90 degree full 30-40 kt xwind

[BSS_Sniper]

a trick is not to apply breaks continuously, but rather do it with pulses 2-3 seconds each. With a proper landing speed I count about 7-9 pulses is enough to make a nice complete stop.

 

If that's the case, it's very wrong. You never brake like that. You apply brakes and you stay on them until you stop or slow to a taxi speed.

[MikeMikeJuliet]

If that's the case, it's very wrong. You never brake like that. You apply brakes and you stay on them until you stop or slow to a taxi speed.

 

That might be about using the keybind-brakes. If you don't have pedals with toe brakes it might be best to not hold them fully or you might burst a tire.

[speedbird5]

If that's the case, it's very wrong. You never brake like that. You apply brakes and you stay on them until you stop or slow to a taxi speed.

BSS_Sniper is correct. You should be able to apply brakes continuously and easily maintain directional control. That's how it is in the real world with real aircraft, both military and civilian.

The F-15 DCS simulation is deficient in fidelity with respect to braking characteristics and should be addressed. It greatly detracts from what is otherwise a great simulation for a desktop program.

Proof of my statement is because in the Mirage 2000-C, with precisely the same axis curves for brakes and rudder as with the F15, I can bring the Mirage to a stop commencing braking at 100 - 90 knots and keep it straight until a full stop. No weaving. No "pulsing of brakes".

This is definitely not the case with the F-15C.

Could the developer please address this issue as it has been brought up in many posts and threads.

Edited November 5, 2016 by speedbird5

[speedbird5]

? It's exactly the same with the DCS F-15. No directional control problems at all while applying full braking from 150kts down to 0kts.

I intentionally even started shallow turns at high speed while maintaining maxium braking.

BTW, maintain directional control in a heavy xwind isn't easy, neither IRL nor in the sim.

What are you using for rudder control? How is it calibrated? What does the curve look like?

What are you using for brake control? How is it calibrated? What does the curve look like?

Do you have individual/differential brakes set up or is the brake application the same for both wheels?

 

Why is it that I can use precisely the same curves and calibration for the Mirage 2000-C and not have any problems, yet with exactly the same settings in the F-15C, I get directional control problems?

Edited November 6, 2016 by speedbird5

[speedbird5]

? It's exactly the same with the DCS F-15. No directional control problems at all while applying full braking from 150kts down to 0kts.

I intentionally even started shallow turns at high speed while maintaining maxium braking.

BTW, maintain directional control in a heavy xwind isn't easy, neither IRL nor in the sim.

 

OK, so I disconnected my rudder pedals and did some tests:

 

Conditions:

 

1. No wind or cloud or turbulence in mission.

2. Mirage 2000 and F15, both landing at Groom.

3. Used the W key for brakes which applies brakes perfectly symmetrically (this is an assumption on my part) on both wheels (Right Ctrl+Enter to verify brake application)

 

 

Results:

 

1. Mirage, landing on centreline - nosewheel on at about 135 knots. Press W key and hold until full stop. Dead straight and does not veer from centreline.

 

2. F15, landing on centreline - nosewheel on at about 135 knots. Press W key and hold until full stop. Veer from centreline at about 100 knots and off the runway into the dirt.

 

3. If you watch the control inputs on roll out (Right Ctrl+Enter), when you press and hold the W key, both brakes are applied in a symmetrical fashion and there is no rudder input at all.

 

4. From these tests I can conclude there is something in the F15 which either applies asymmetrical braking or some other type of lateral input which causes the divergence. The Mirage does not exhibit this problem under identical conditions.

Edited November 6, 2016 by speedbird5

[speedbird5]

3. Because the F-15 has the almost identical wheelbase and track width, but the F-15s empty weight is almost double the weight of the Mirage! CG is higher, and the wingspan is almost 50% larger.

Btw, mine also very slowly starts to turn to the left at around 100kts and that's the beauty of DCSs realism, that even tiny variations in shock strut loading and/or tiny L/R weight differences have an effect.

 

No, I will have to disagree. You might call it realism, but IMO it is quite unrealistic.

If the F-15 handled like that, with increasingly divergent oscillations as you try to correct to centreline, it couldn't have been certified.

The original poster asked the question.... "F-15C - How to apply brakes without going off the runway?"

We really shouldn't have to be answering that question.

Edited November 6, 2016 by speedbird5

[Bushmanni]

PIO is a function of control lag. If your steering inputs cause reaction only after some time you will get easily into PIO. More lag causes PIO more easily. While the F-15 in DCS is controllable with very careful steering, if it was in my power I would definitely send it back to drawing board to get nosewheel steering work with less lag and with more positive feel of control.

[speedbird5]

It's certainly not the planes fault if you experience 'increasingly divergent oscillations', that's simply a classic case of PIOs.

 

And that's the point, isn't it? No aircraft I have flown induces PIO's in that manner.

 

In my experience ( and I have 16000+ hours in military types and jet airliners in the real world ), the behavior of the DCS F-15 is unrealistic in that it induces these PIO's on the landing roll out with no wind, under normal, symmetrical braking.

 

BTW, I can make the aircraft track the centreline, but you have to use techniques which one does not normally use.

 

PIO is a function of control lag. If your steering inputs cause reaction only after some time you will get easily into PIO. More lag causes PIO more easily. While the F-15 in DCS is controllable with very careful steering, if it was in my power I would definitely send it back to drawing board to get nosewheel steering work with less lag and with more positive feel of control.

 

I agree that it needs to go back to the drawing board, and to me it would seem to be a rudder responsiveness problem (i.e. the lag to which you refer) which needs to be addressed - more so than the nosewheel steering.

Edited November 6, 2016 by speedbird5

[speedbird5]

1. I don't see that the F-15 induces PIOs. If she starts to leave the centerline I just steer her back with minimal inputs.

 

Well, I don't experience that with the F-15 in DCS and it would seem the OP, and others, don't either.

 

I guess we will just have to agree to disagree.

Edited November 6, 2016 by speedbird5

[Bushmanni]

PIO doesn't need control lag to happen. You can even get into PIOs with strictly mechanical direct control input with zero lag.

If the F-15 slowly leaves the centerline and you start overcorrecting you will get into PIOs, with or without control lag.

 

I can get into a PIO with a direct mechanical control input while driving a big boat (extreme example to illustrate my point). The issue isn't how fast rudder starts turning when you turn the helm but how quickly the vehicle responds to your steering inputs (which in case of a big boat is very slow). There's also the issue about being able to perceive the response. In the case of the big boat it'll turn only slow regardless of your control inputs and it will keep turning slowly in the same direction long after you turn the helm into opposite direction. You need to pay attention to see the slow turn in time before the boat is going in a wrong direction or you end up in a never ending zig zag (i.e. PIO). If the response to control input is is hard to see or the sensory data of the response is lagging, the effect is the same, PIO is much more easier to get into. Bottom line is, that PIO is a function of lag between control input and perceived control response, regardless of where the actual lag happens in the control loop.

 

Overcorrecting only happens when the response to your control input comes late and you keep increasing the control input in hopes of seeing response and then suddenly you get more than you wanted. You can overcome this by knowing how much lag the control system has and anticipate it. But regardless how good you get at anticipating how the laggy streering works, it's much harder to control a laggy control system and you can only make smaller control adjustments than with one that has less lag.

 

Overcontrolling without laggy controls happens only with noobs who are completely unfamiliar with the system and pay attention to wrong things (sensory lag) or outright use maximum control inputs because they don't know better.

 

Control lag is one of the reasons why in a gunzo match between F-15 and Su-27 flown by ace pilots the Eagle pilot has a better chance of winning as he can hit the Flanker with snapshots from much harder shooting situations because of much faster control response of the Eagle. Eagle pilot can easily track the Flanker with the gunsight and the Flanker can't dodge it while in the reverse situation Eagle pilot can easily (as long as the Eagle has speed) dodge the Flanker gunsight and there's nothing the Flanker pilot can do about it as the Flankers nose follows the control inputs with too much lag. When the flankers nose starts to turn towards the Eagle, he has already changed his direction again. The funny thing is that Flanker can actually turn it's nose faster in a steady turn.

 

PIO is a function of control lag and with more lag PIO comes more easily regardless of how experienced the operator is.

Edited November 6, 2016 by Bushmanni

[SinusoidDelta]

No, I will have to disagree. You might call it realism, but IMO it is quite unrealistic.

If the F-15 handled like that, with increasingly divergent oscillations as you try to correct to centreline, it couldn't have been certified.

The original poster asked the question.... "F-15C - How to apply brakes without going off the runway?"

We really shouldn't have to be answering that question.

 

I agree. The eagle is equipped with anti-skid and a pulser brake system. Between those two systems I don't think the skidding behavior is accurate.

[GGTharos]

I'll bring this up with cofcorpse when the time is right.

[proletariat23]

Just wanted to say, after many crashes and learning on my own for 3 weeks in the dark- if you use the kneeboard and study the flight profiles for viziani, and you follow the pattern made for landing f15cs on that strip, it almost lands itself.

 

if you eyeball it and try to ball it out maverick over the city, you have shitty visibility and you come in way too hot, low, fighting the throttle with power lines in your face.

 

Know those patterns for your divert and your main, practice Instrument landings with your head down. best way is to jump in the deep end. sink or swim.

[carcinomic]

So this has been a really helpful thread. I'm obsessed with this method now, it was such a pain trying to control the F-15C on the ground using brakes, rudder, and a prayer. I did it enough to know how at least... :doh:

 

The takeaway I got from this--

-watch your speed (160-180 kts), rate of descent/AoA (20+),

-try to keep your nose around 5 degrees above horizon line, but your velocity vector on the start of the runway no more than 5 degrees below the horizon line,

-flare appropriately/apply airbrakes/cut throttle at the right place and time,

-let back tires land first, hold the stick up so your elevators contribute to air resistance, flaps are more useful on approach than here

-never push your nose up more than 10-13 degrees above horizon until around 100 kts before bringing the nose gear down gently and pumping the brakes until a stop. above 15 degrees results in damage.

-More payload, more forward power but stay below 200 kts, lower your approach altitude so there's minimal impact on landing.

 

This is a really cool way to be gentle about landing, and the best part-- have directional control of the aircraft on touchdown which was the biggest issue on my end. Now I can manage a clean landing with a busted tire.

 

Speaking of which, anyone know how/why the F-15C's tires just pop on takeoff sometimes? Or why sometimes it seems really difficult to just keep the F-15C going straight down the runway?

Edited March 22, 2017 by carcinomic

[Sweep]

I would disregard speed, fly the 2-3 degree glideslope at 20-22 units AOA (10-12 degrees...Eagle displays units). Flare to 23uAOA and pull power as required on the flare - If you're overweight, you won't be pulling power too fast.

 

As for takeoff - Nose UP (and of course nose wheel) at 120kts to 10 degrees, mains come off at 145-160, normally. Many people have this tendency to wait until 160-180 to rotate and it pops the mains in game - It shouldn't, but it does.

[Crew Dog]

Also, don't forget that the Eagle has NWS (Nose Wheel Steering) disengage and anti skid. When on roll after touchdown, I pop my air brake and keep my stick pulled back to maintain approx. 10 deg indicated pitch till the frame physically can't maintain it. Once the NLG is on the deck, I hold the NWS disengage (mapped to the paddle on my X-55 in Mode 1) and keep on the brakes till about 20kts indicated. Only then is when I release NWS disengage.

Edited March 23, 2017 by Crew Dog

[GGTharos]

So this has been a really helpful thread. I'm obsessed with this method now, it was such a pain trying to control the F-15C on the ground using brakes, rudder, and a prayer. I did it enough to know how at least... :doh:

 

It depends on which landing technique you want to use ... shortest ground-roll will be all brakes, zero aero-braking.

 

The takeaway I got from this--

-watch your speed (160-180 kts), rate of descent/AoA (20+),

Nope. Just watch the AoA. If you have less than 21 you might float, especially if light, if you have more, you might find yourself quickly getting even more, so be precise. It's not that hard :)

 

-try to keep your nose around 5 degrees above horizon line, but your velocity vector on the start of the runway no more than 5 degrees below the horizon line,

Nope. VV on runway at -3deg. Or -2.5 ... not 'up to -5', that's way too steep. Less then -2.5 is too shallow (unless going for min ground roll). Move the aim from the threshold to the 500' or 1000' markers, your choice.

 

Again, precision is key.

 

-flare appropriately/apply airbrakes/cut throttle at the right place and time,

Yes. but what is the right place/time? :)

 

-let back tires land first, hold the stick up so your elevators contribute to air resistance, flaps are more useful on approach than here

Flaps are irrelevant unless on min-ground roll (raise flaps immediately when on ground). Your elevators are also irrelevant well, mostly. Just keep the nose up 13-15 deg for effective aero-braking above 90kts.

-never push your nose up more than 10-13 degrees above horizon until around 100 kts before bringing the nose gear down gently and pumping the brakes until a stop. above 15 degrees results in damage.

Less than 13 deg is pointless, effective aero-braking is at 13. Keep it there accurately.

 

-More payload, more forward power but stay below 200 kts, lower your approach altitude so there's minimal impact on landing.

AOA at 21 on approach and glideslope as before, forget the speed and this altitude BS unless you are super-heavy, in which case a slightly shallower approach might be ok but other parameters as before! What's super-heavy? You just took off full of fuel, 3 bags and missiles and are going right around to land again. The main difference in technique is to delay throttling back in the flare, not to change other landing parameters.

 

Speaking of which, anyone know how/why the F-15C's tires just pop on takeoff sometimes? Or why sometimes it seems really difficult to just keep the F-15C going straight down the runway?

Bad T/O technique? Ground roll too long? I find it's easy to control if you're gentle on the rudder and you don't get yourself into a PIO - adjust rudder axis curves as necessary.

 

Edit: Maintain -2, -1.5 deg glide-slope and 23 uAoA for min ground roll Be precise, less makes you float or faster, your landing aimpoint ends up further down the runway, more puts you in the ground quickly - as in possibly before the runway. Do NOT flare into a float, only flare slightly to reduce descent rate. Throttle idle immediately upon touch down, NLG on the ground and constant brake application (in-game, pump as required to maintain steering).

 

This is all about flying a stable, precise approach. It's also the landing technique from the real aircraft's manual. There are others, but these are the standard ones.

Edited March 23, 2017 by GGTharos

[oldpop]

F15 NWS

 

There are 2 controls for NWS, engauge and range. Looking at the A/c ext view the nose wheel will move with the rudders no matter what I choose!

What am I missing???