HOTAS design: DLC/Maneuver Flaps Logic

[Nealius]

This is more of a HOTAS design question regarding the real Tomcat's pilot stick, but the logic of the rocker switch that controls DLC/Maneuver Flaps operation has me scratching my head a little.

 

With DLC engaged, rocker switch forward extends the inboard spoilers, and rocker switch aft retracts the inboard spoilers. This part is logical: Forward = Out, Aft = In.

 

With DLC off, rocker switch forward retracts the maneuver flaps, and rocker switch aft extends the maneuver flaps. This part is illogical to me: Forward = In, Aft = Out.

 

Why was the maneuver flaps operation logic designed to be the opposite of the DLC operation logic?.....on the same switch? I often find myself screwing things up between the DLC or maneuver flaps because my brain expects them to be the same.

[DarkStar79]

I also wonder this. it feels kinda akward..

[danny875]

I think it is because the logic of the manoeuvre flaps matches that of the soeedbrake (aft for extension).

I like to think of it as forward = go faster and backwards =go slower...

The DLC matches the logic of the flight stick pitch axis (aft for lift - spoilers down and forward for sink - spoilers up).

Edited March 19, 2019 by danny875

[VC]

I thought about this and tried to make up my own justifications.

 

 

Firstly, I believe it's a wheel not a switch (I bound it as such on my own controls). So I think it has something to do with the position you left it in. E.g. normally the manoeuvre flaps would be in, so wheel all the way forward, hit DLC button, hey presto spoilers are all the way out, now you can bring them back in.

 

 

Note this is pure speculation on my part.

[Pikey]

I have no idea if I've inverted from the real thing, but forward (aligned with pitch forward, ie down) is perfect and natural. A little press and the FPM drops a bit, exactly as I would have thought it should do.

 

 

So, my response would be, if it's not doing that, you get the luxury of redesigning your airplane to do it exactly as it should.

 

 

I very nearly reversed the wing sweep controls for exactly the same reasons.

 

 

Speedbrake mapping in my head is forward for fast, aft, for slow, which is the direction of the throttle.

 

 

 

Can't understand any reasoning for deviating from the natural hand movements.

[Nealius]

I have no idea if I've inverted from the real thing, but forward (aligned with pitch forward, ie down) is perfect and natural. A little press and the FPM drops a bit, exactly as I would have thought it should do.

 

 

 

Yes, with the DLC, which as I said is logical. It's the maneuver flaps that's backwards in relation to the DLC functions, when the control surfaces themselves are making the same movements (i.e. extend/retract).

[some1]

The cockpit controls for flaps in every aircraft I remember is forward to stow, and aft to extend. Just look at your flaps lever on the left panel.

 

The switch does not follow IN/OUT logic but rather slower/faster, while in DLC mode it matches the stick function (forward to increase sink rate, aft to decrease).

Edited March 19, 2019 by some1

[Victory205]

I think it is because the logic of the manoeuvre flaps matches that of the soeedbrake (aft for extension).

I like to think of it as forward = go faster and backwards =go slower...

The DLC matches the logic of the flight stick pitch axis (aft for lift - spoilers down and forward for sink - spoilers up).

 

This, sort of.

 

When maneuvering, to turn tighter you pull aft on the stick. Similarly, you pull aft on thumbwheel to extend flaps and tighten the turn. Same way the flap handle moves.

 

Landing config you push forward to descend and also push forward on thumbwheel to do the same.

 

It's quite natural to a pilot.

Edited March 19, 2019 by Victory205

[escaner]

The cockpit controls for flaps in every aircraft I remember is forward to stow, and aft to extend. Just look at your flaps lever on the left panel.

 

The switch does not follow IN/OUT logic but rather slower/faster, while in DLC mode it matches the stick function (forward to increase sink rate, aft to decrease).

 

 

Exactly, in every aircraft I know, flaps lever forward or up retracts them, while down or back extends.

 

 

What looks inverted to me is the DLC mode, as speedbrakes and spoiler controls are always designed to mimic the throttles, from glider aircraft to large airliners: forward is faster (retract), and aft is slower (extend). Maybe it has to do with mounting the control in the stick instead of in the throttles as you say.

[VC]

This, sort of.

 

When maneuvering, to turn tighter you pull aft on the stick. Similarly, you pull aft on thumbwheel to extend flaps and tighten the turn.

 

Landing config you push forward to descend and also push forward on thumbwheel to do the same.

 

It's quite natural to a pilot.

 

 

That makes a great deal of sense and also explains why the wheel is on the stick (as opposed to the throttle). My setup at home, my throttle has way more buttons and axes than my stick, so a lot of functions (including DLC) that are on the stick in the real Tomcat are on the throttle for me. This makes it a bit less "natural", shame I can't map it realistically and take advantage of the feeling as you describe it.

[Lex Talionis]

As some have said, the logic is "forward = relitively less lift and less drag, aft = relitively more lift more drag."

 

The intelectual dissonance may be explained by,

The aerodynamic logic is probably trading the parasitic drag created by the spoilers, for the considerably more drag created by the flaps both by parasitic and induced from the lift created.

 

The result is probably that, even though the spoilers are out in one instance and not in the other, the total drag is less than the flaps.

 

What's more, the "maneuvering" flaps are controlled by the CADC (not the pilot). (Consider) The aircraft rolls through a combination of spoilers and stabalators. With the wings forward the CADC can then also make use of, what would otherwise only be the "flaps" as controlled by the pilot, taking some of that "flap" and making it an "aileron". When you roll the DLC aft it returns some of that "aileron" function back to "flap" . Because of this it fairs the spoilers which now allows roll authority when deployed asymmetricaly, countering the roll authority lost from the "maneuvering flaps" (aileron) returning to "regular flaps". Why "maneuvering flaps" is opposite DLC.

 

In short:

DLC forward, less lift less drag, roll control from "Maneuvering flaps, *some* spoliers and stab. Roll DLC aft, lift created by returning "maneuvering flaps" to regular flaps, roll authority lost from maneuvering flaps "removal" restored by fairing *some* spoilers and useing asymmetricaly faired. Increased drag from flaps also counterd by the retracted spolers.

 

Symantec nightmare.

 

Only reason i explain this (other than it is an interesting mental exercise in aerodynamics) is that, you just can't think of the DLC as a "moves surfaces X in Y fashion " as you would with the SB slider. It is something that creats more lift and drag as dictated through a computer that solves the best way to accomplish it. Probably why it is called a "Direct Lift Control " and not a "flap control " ... something like that.

 

:)

Edited March 19, 2019 by Lex Talionis

[some1]

Exactly, in every aircraft I know, flaps lever forward or up retracts them, while down or back extends.

 

 

What looks inverted to me is the DLC mode, as speedbrakes and spoiler controls are always designed to mimic the throttles, from glider aircraft to large airliners: forward is faster (retract), and aft is slower (extend). Maybe it has to do with mounting the control in the stick instead of in the throttles as you say.

 

It's because the purpose of the DLC is not to slow you down or make faster, but to control your position on the glidepath, and there it follows the stick movement. Too high on the glidepath - move forward (stick/DLC), too low, move aft (stick/DLC).

 

Don't think about DLC as flaps, spoilers or whatever, it's higher level of abstraction. Just a magic switch that adjusts your sink rate.

[escaner]

It's because the purpose of the DLC is not to slow you down or make faster, but to control your position on the glidepath, and there it follows the stick movement. Too high on the glidepath - move forward (stick/DLC), too low, move aft (stick/DLC).

 

Don't think about DLC as flaps, spoilers or whatever, it's higher level of abstraction. Just a magic switch that adjusts your sink rate.

 

 

That is precisely its weirdness: for a trimmed AoA, what controls your sinkrate is the throttle and now you are supposed to do it with DLC. The stick pitch controls AoA

[Victory205]

As some have said, the logic is "forward = relitively less lift and less drag, aft = relitively more lift more drag."

 

The intelectual dissonance may be explained by,

The aerodynamic logic is probably trading the parasitic drag created by the spoilers, for the considerably more drag created by the flaps both by parasitic and induced from the lift created.

 

The result is probably that, even though the spoilers are out in one instance and not in the other, the total drag is less than the flaps.

 

What's more, the "maneuvering" flaps are controlled by the CADC (not the pilot). (Consider) The aircraft rolls through a combination of spoilers and stabalators. With the wings forward the CADC can then also make use of, what would otherwise only be the "flaps" as controlled by the pilot, taking some of that "flap" and making it an "aileron". When you roll the DLC aft it returns some of that "aileron" function back to "flap" . Because of this it fairs the spoilers which now allows roll authority when deployed asymmetricaly, countering the roll authority lost from the "maneuvering flaps" (aileron) returning to "regular flaps". Why "maneuvering flaps" is opposite DLC.

 

In short:

DLC forward, less lift less drag, roll control from "Maneuvering flaps, *some* spoliers and stab. Roll DLC aft, lift created by returning "maneuvering flaps" to regular flaps, roll authority lost from maneuvering flaps "removal" restored by fairing *some* spoilers and useing asymmetricaly faired. Increased drag from flaps also counterd by the retracted spolers.

 

Symantec nightmare.

 

Only reason i explain this (other than it is an interesting mental exercise in aerodynamics) is that, you just can't think of the DLC as a "moves surfaces X in Y fashion " as you would with the SB slider. It is something that creats more lift and drag as dictated through a computer that solves the best way to accomplish it. Probably why it is called a "Direct Lift Control " and not a "flap control " ... something like that.

 

:)

 

Good grief. I've known how the system works and how to use it for 35 years. After reading that, I'm not so sure anymore. ;) ;)

 

Fighter Pilot Logic -

 

Dirty

 

Push on Stick- Houses get bigger. Push on DLC thumbwheel- Houses get bigger.

Pull on Stick- Houses get smaller. Pull on DLC thumbwheel- Houses get smaller.

 

Clean

 

Pull on Flap Handle- Flaps extend. Pull on DLC thumbwheel. Maneuvering Flaps Extend...

Etc, etc, etc.

 

Better yet, just let the maneuvering flaps work automatically.

 

In a week, this will all be second nature. You are making more complicated than it is.

 

Get out there and fly!

[Victory205]

That is precisely its weirdness: for a trimmed AoA, what controls your sinkrate is the throttle and now you are supposed to do it with DLC. The stick pitch controls AoA

 

No, you control rate of descent with power. DLC on the aircraft for a single, particular scenario. Read the Case I tips, you'll save yourself a lot of agony.

[Mule]

A question asked on another part of this forum which has more to do with binding an axis was this.

 

"is the DLC thumbwheel an axis IRL? ATM it does not allow for permanently driving the LE controls to a certain state. It deploys an retracts the spoilers which results in a momentary effect. Maybe this is the real thing but I‘m not sure here. Anybody knows how this works IRL?"

 

Can you former fighter pilots help make that clear?

[VC]

A question asked on another part of this forum which has more to do with binding an axis was this.

 

"is the DLC thumbwheel an axis IRL? ATM it does not allow for permanently driving the LE controls to a certain state. It deploys an retracts the spoilers which results in a momentary effect. Maybe this is the real thing but I‘m not sure here. Anybody knows how this works IRL?"

 

Can you former fighter pilots help make that clear?

 

 

If you bind it to a rotary or slider axis it stays where you put it.

Edited March 19, 2019 by VC

[kengou]

No, you control rate of descent with power. DLC on the aircraft for a single, particular scenario. Read the Case I tips, you'll save yourself a lot of agony.

Is there a good reason not to set power and trim to level on-speed flight, then using DLC alone to adjust glideslope? Seems like this would be possible.

[Victory205]

Is there a good reason not to set power and trim to level on-speed flight, then using DLC alone to adjust glideslope? Seems like this would be possible.

 

If my office chair had an ejection function, I'd be pulling the handle right now!

[VampireNZ]

If my office chair had an ejection function, I'd be pulling the handle right now!

 

:megalol:

 

I think that is fighter pilot-speak for 'No my good sir, I believe that approach to DLC use would be counter-productive to achieving a positive outcome.'

[Supmua]

Yeah but this is DCS, so people are going to try weird things such as landing the Harrier on a moving train or vertically landing the F-14 on the Tarawa.

[Naquaii]

The real DLC wheel is springloaded to center afaik, so as soon as you release it the DLC would reset to the neutral position. That's why we don't have a keybind to leave it in another position.

[VC]

The real DLC wheel is springloaded to center afaik, so as soon as you release it the DLC would reset to the neutral position. That's why we don't have a keybind to leave it in another position.

 

 

So it's wrong to bind it to a wheel that stays where you put it?

 

 

Do the manoeuvre flaps go back in when you stop holding the wheel too?

[Nealius]

I admit, I've never bothered looking at how the flaps levers in aircraft work as I'm always hitting the Foxtrot key :lol:

[escaner]

Better yet, just let the maneuvering flaps work automatically.

 

 

Once I have manually fiddled with maneuvering flaps, how can I revert them to auto?

 

 

No, you control rate of descent with power. DLC on the aircraft for a single, particular scenario. Read the Case I tips, you'll save yourself a lot of agony.

 

 

Thanks, very interesting read!

But I didn't really understand the DLC part. Could you rephrase the expression "flat over the ramp"?

 

 

I see that you keep looking at the VDI for pitch reference. Is that instrument IFR certified?

 

 

Thanks a lot!