Pitch up / trim up after flaps usage

[Svsmokey]

"Fly-by-wire control systems for aircraft simulate the feel—that is, the feedback forces—that a pilot senses while flying the aircraft. When hydraulic controls first entered such systems, force feedback to the control stick was provided by springs and bob-weights that attempted to duplicate the forces (forces previously felt from direct linkages to the control surfaces) caused by airloads on the control surfaces, or by changes in the angle of attack at constant speed. This at times, and depending on the demands of the task, resulted in overcontrol and pilot-induced-oscillations (PIOs). Military specifications (8785b) and standards (8785) attempted to guide designers so that a “good feel” was presented to the pilot, and today these “flying qualities” are evaluated by test pilots skilled in the use of what is called the “Cooper-Harper” scale ."

 

And from the Natops .

 

"Although there is no aerodynamic feedback to the stick and rudder pedals, the effect is simulated by flight control computer scheduling of control surface deflection versus pilot input as a function of flight conditions."

 

Combine the above with the Hornet's spring-centered stick , with increasing stick force with increased stick travel , and you have (drum roll please) trim as a function of stick force in the Hornet landing mode .

Edited September 28, 2018 by Svsmokey

[Rackham]

A tip : I used this mod

https://www.digitalcombatsimulator.com/en/files/3300978/

to help trimming during the learning curve. Once full flaps and gear come down together, below 250kts, you just have to trim till the white indicator reach the level -2.5 : this is the maximum trim you will need. Then you wait till speed reaches 150 knots, then follows the curse of the plane and use throttle to E bracket, with anticipation. The ballooning effect will be smaller if flap and gear are activated below 200 kts.

[Svsmokey]

Thanks for that ! Between yours ,Trev's and Squirrel's suggestions , perhaps i can find a way to overcome my inabilities , (and lack of FFB )

:) and tighten up my patterns to a Natop standard , even if not procedure .

[bbrz]

I don't understand the lack of FFB problem at all.

If the F/A-18 balloons you have to apply forward stick pressure. Then you start trimming nose down until you don't have to apply any pressure on the stick anymore.

[Svsmokey]

I appreciate your interest , I answered that in post #22 . Thanks

[bbrz]

I honestly don't see a significant difference between FFB and springs in this case.

While you are trimming, you have to constantly remove stick pressure until it reaches zero. No trial & error required.

Why would you trim-relax-trim-relax....?

Edited September 28, 2018 by bbrz

[Svsmokey]

I am clearly a poor communicator . Both of your last two posts are entirely correct in real life . But in a simulator , i can hold the trim button down from now to Christmas , and my stick force will never change , unless i have a force-feedback stick . I can't trim to neutral pressure witout trial and error , which extends my downwind .Understand that my every post in this thread reflects my own inability . I wish to tighten up my patterns , which are currently extended about 1/2 mile , and I am willing to entertain other's ideas to do so , even if they are not strictly Natops . The whole trimming conversation arose from that , and I kinda regret mentioning it :)

[Svsmokey]

Perhaps we are using different definitions ? Im 'referring to the force one's hand applies to a stick . Or , in the case of trimming , the force the stick applies to the hand .

[bbrz]

But in a simulator , i can hold the trim button down from now to Christmas , and my stick force will never change , unless i have a force-feedback stick . I can't trim to neutral pressure witout trial and error...

The stick force will not change but the pitch attitude will and that's not what you want!

Let's say you are flying with a 5deg nose up attitude and extending the flaps would pitch the nose up to 10deg.

 

Since you want to keep the 5deg (or even decrease it to avoid ballooning) you have to apply forward pressure on the stick to keep the 5deg nose up pitch attitude.

 

As soon as you start trimming nose down, the pitch attitude will start to decrease below the 5deg target attitude if you maintain the same forward pressure on the stick.

 

The longer you trim nose down, the more you have to relax the pressure on the stick if you want to maintain your target pitch attitude.

 

Very soon there will be no more nose down trim required since the nose remains at the 5deg target pitch attitude without the need to apply any pressure to the stick.

[Flamin_Squirrel]

I think you might have a missunderstanding about what trim is for and how it's used.

 

You use the stick control where you want the nose of the aircraft to go. Once the nose is where you want it, if you find yourself having to apply pressure to keep it there, you use trim to remove those stick forces. That's it. There's no trial and error, you just keep trimming until you don't have to apply any more pressure.

 

In the DCS Hornet using your desktop stick, trimming allows you to move the stick back to neutral, thereby removing the force you were applying, as described above. This is exactly how the real Hornet works too. I'm not sure why you think there's a difference.

[majapahit]

I am clearly a poor communicator . Both of your last two posts are entirely correct in real life . But in a simulator , i can hold the trim button down from now to Christmas , and my stick force will never change , unless i have a force-feedback stick . I can't trim to neutral pressure witout trial and error , which extends my downwind .Understand that my every post in this thread reflects my own inability . I wish to tighten up my patterns , which are currently extended about 1/2 mile , and I am willing to entertain other's ideas to do so , even if they are not strictly Natops . The whole trimming conversation arose from that , and I kinda regret mentioning it

This is what I noticed.

 

Off the deck, wheels up, flaps up, which signals the FCS controller to kick in and this FCS aware you're now in clean configuration even if in any bank or climbing out steady at your controlled 170-220kts upwards and FCS takes over trim for controlled AOA flight (stay under 250kts is a good idea when exercising this manoeuvre, after which you can try it at 600 kts, which is much of the same but more exhilarating).

 

You’re now already set up trim wise for an immediate go-around break (or in any other situation if you’re above in the pattern coming in or circling under FSC in clean config),

 

in short you necessarily only have to 'steady' your flight path for a sec whilst in clean config, a steady continuous bank will do, levelling out and wait-a-instant will do, and you’re all set up to go for this (unapproved and watched by hawk eyes, who can send you land based if they think you behaved like a dick) ‘fast’ break, the FCS ready for ‘normal’ and ‘manoeuvring’ mode(s) when clean,

 

then you bank hard entering this particular (short) break, you lower gear an flaps full and because of the hard banking (and therefore induced added pitch at speed) you throttle towards an appropriate ‘on speed’ as you already had planned for, that works for this particular manoeuvre, you anticipate and counteract all the unrolling flight envelope changes,

 

your start trimming towards that particular 'on speed' trim that is dictated at the egress of the break when merging out of the break and into the groove and that’s half a century away,

 

at the half way of the break you're now full dirty and you check everything is OK (your speed, your height, your bank, your semi-pitch, your decent rate as planned, your indicators, your hook, your trim indicator moving towards the appeared E bracket in the HUD when dirty which doesn’t mean anything much whilst in this move, but none-the-less you know exactly what it shows) and you calculate the rest of the turn glancing the deck of the Stennis vis-a-vis where you are and how to go about it from here,

 

you’re already hard throttling towards the 45 and trying to find the wake and control everything that needs controlling to get to the merge,

 

and then the ICLS bars pop up and you check if your estimated trim that you dialled in blindly would be at the proper number according to the behaviour of the F-18 under your butt, which depends on your weight and your loads etcetera, and this is quite hard, for you did this trimming blindly with just timing your trimmer thumb.

 

You’re egressing from your break into the merge and you can have a - very - short check concerning your much exercised blind trimming compared to the planned and wished for trimming,

 

whilst you also landed exactly on the ICLS bars where you wanted to be and you compare all this with the F-18 behaviour that is now level under your butt with its particular load-out of the day and weight and fuel remaining and weather and wind shear,

 

you can make a last - very quick - adjustment of the trim if need be according to all the parameters at hand, your AOA, your speed, your necessary throttle yanking, your situational awareness of distance and attitude toward the deck, and with full view of the ICLS bars and the Stennis deck in view, or if in the dark, the deck lights that are hobbling on the waves and are approaching pretty fast now.

 

And there you go, you’re on wire #3.

Edited September 28, 2018 by majapahit

[bbrz]

Your suggestion makes a new pilot very frustrated and that's not a good way to learn.

I'd guess there are different ways of learning. E.g. I'd rather drop the gear and full flaps at once and concentrate just on the flying part afterwards, instead of multiple configuration changes over a longer time span.

[Flamin_Squirrel]

I know that and you know that but he's having difficulty. That was the point. He's still learning how to control the aircraft, so he's not as able to spank a 90 degree roll into a 4 G turn from 400 KIAS while popping board and dumping gear and flaps halfway through the turn.

 

Your suggestion makes a new pilot very frustrated and that's not a good way to learn.

 

I agree overwhelming a new pilot isn't good but the specific issue here is how to avoid ballooning while flying a case I recovery. They're already flying the break. Following NATOPS and dropping flap during the break not before (or after) helps solve this issue, it doesn't make anything harder.

[Svsmokey]

God , I can be incredibly dense sometimes ! Thanks to everyone . You're talking about using the mark 1 eyeball as feedback , and i was justifying my extended patterns by the lack of tactile feedback . So thank you all , i'm gonna sleep for a week now , and please accept my apologies .

[bbrz]

You're talking about using the mark 1 eyeball as feedback , and i was justifying my extended patterns by the lack of tactile feedback.

 

For really useful tactile feedback you need to be in a motion sim. As long as you are sitting in a chair in front of your PC you have to rely onto your mark 1 eyeball. ;)

(btw, I don't see anything you would need to apologize for)

[_e10]

Just updated stable branch. I have the problem with the pitch up on stable too :/

 

 

Just to make sure, the little cross (marked in blue color) indicates flaps position, correct?

[_e10]

Okay found a "workaround"... I guess...

 

 

When flaps are UP and the weird cross is still down:

- Flip flap switch to down (or half) -> indicator cross jump back to center

- Immediatly flip flap switch to up again -> indicator stops and keeps near the center.

 

 

I am out of ideas.

Also there is no different in cross position whether flaps are HALF or DOWN. Cross is in the same position.

 

 

Good God why??? Gimme my weekend and let me try the new campaign :megalol:

[majapahit]

Just updated stable branch. I have the problem with the pitch up on stable too :/

 

 

Just to make sure, the little cross (marked in blue color) indicates flaps position, correct?

I'd say that cross in the indicator is trim.

 

Trim 12 I would guess.

 

Wheels on the ground ready for take off / per the FCS

All is well, nothing to do with flaps.

 

When you put flaps up, the FCS will notice and tries to set you up for 'normal' AOA flight, hence the trim moves to center.

 

EDIT: The erratic behavior of the trim, parked when moving the Flaps probably is because the FCS had to little data, airspeed, AOA, you need to power down the runway for the FCS to decide what to do, and be in the air, and clean, and the FCS will switch to 'normal' flight mode.

 

When you 'pitch up when stable' you're not watching your airspeed? Which would mean you would be stalling and the craft will pitch up (1 reason). When clean you have to be on speed.

 

 

'When I takeoff the plane pitches up even if I go full stick forward... ' lessen throttle until you pitch as desired, when stable climb you throttle up.

 

You should take off with half flaps, perhaps when you're taking off 0-flaps, and you're heavy, you quasi 'stall' when wheels come off the ground, and that's what making you pitch up.

Edited September 29, 2018 by majapahit

[majapahit]

Thinking about this, you could test if you're too slow climbing out with 0-flaps (and perhaps heavy), by taking a lot more runway and rotate like over 220kts, or 240, see what happens.

[_e10]

Hi guys, thanks for all the input. Problem is solved, I have no idea what was causing it and what exactly solved it.

I detached all inputs except keyboard and mouse and deleted the whole "[...]/Saved Games\DCS" folder.

Then I tried again but I accidently set flaps to UP so this could not work.

But after this ("stupid") test I reattached all controls and set again all key bindings since I could not import the old ones... dont know why.

I dont know why but now everything works again... :joystick:

[Bankler]

_e10

 

You're not alone. In our group, we have seen the same thing happen a couple of times. After takeoff, gear retracted, auto flaps, no trim, and suddenly it felt like an invisible monkey is pulling the stick 100% and no trim in the world can compensate for it. Regardless of speed or flap setting. It was not subtle, but litterally felt like you fully pulled the stick all the time.

 

We never found out how to reproduce it, and it was rare. So conclusion was that either it was 1) a random bug with how the sim read pitch input from the hardware stick (just like you're suggesting), OR 2) it happened if you pressed those buttons (flaps, fcs reset, takeoff trim) in the wrong order during startup. We never found out exactly why it happened, and now we haven't seen it for a couple of weeks.

[aaron886]

I've also encountered it. Especially when taking off flaps AUTO (demonstration flying,) and then accelerating above approximately 225-250 KCAS range. The pitch-up will not stop until decelerating such that flaps can be lowered to HALF (not in ORIDE) and then back to AUTO.

 

It's some kind of pitch integrator windup, and definitely a bug.

[_e10]

Good to hear that I am (maybe) not creazy :megalol:

[VFA41_Lion]

Did it seriously take you guys five full pages to realize the OP was never talking about landing the aircraft? He was clearly stating he was experiencing pitch up movement on takeoff.

[Flamin_Squirrel]

Did it seriously take you guys five full pages to realize the OP was never talking about landing the aircraft? He was clearly stating he was experiencing pitch up movement on takeoff.

 

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