Pitch, Roll, Yaw and Trim
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I know the settings are shown on the Manual Trim Panel. Is there any popup overly for the screen that shows the current position of the trim settings for pitch, roll and Yaw?
Is there a quick way to zero out these axis settings?
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Not that I’m aware of, as far as display of the settings goes - the book says you have to look at the MAN TRIM panel.
I do recall a key command to center the stick from way back, but I can’t find it in the manual just now, and I bet it won’t center yaw Trim if you have any dialed in.
EDIT: according to the keyboard reference, alt+return is the key command to Reset Trim.
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@Stevie [alt+Enter] will toggle fullscreen-exclusive mode. I think there was a “collision” with reset-trim in a previous release … latest stock key files have [alt+F1] mapped to
AFResetTrim
also note [alt+C][J] sequence will recalibrate your joystick center, in flight, if that’s the other thing you were referring…
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It’s worth noting there are 2 sets of trim callbacks for pitch and roll. One set is meant to represent the dials on the back-left console… the other is meant to represent the trim-hat on the stick.
tbh not sure if AFResetTrim zeroes them both, or just the dials? I’ve never had stick-trim mapped on my hotas…
SimTrimRollLeft 309 0 0X43 5 0 0 1 "TRIM: ROLL TRIM Wheel - L WING DN" SimTrimRollRight 309 0 0X44 5 0 0 1 "TRIM: ROLL TRIM Wheel - R WING DN" SimTrimAPDisc 310 0 0X58 5 0 0 1 "TRIM: TRIM/AP DISC Switch - Toggle" SimTrimAPDISC 310 0 0XFFFFFFFF 0 0 0 1 "TRIM: TRIM/AP DISC Switch - DISC" SimTrimAPNORM 310 0 0XFFFFFFFF 0 0 0 1 "TRIM: TRIM/AP DISC Switch - NORM" SimTrimYawLeft 116 0 0X43 6 0 0 1 "TRIM: YAW TRIM Knob - L" SimTrimYawRight 116 0 0X44 6 0 0 1 "TRIM: YAW TRIM Knob - R" SimTrimNoseUp 309 0 0X57 5 0 0 1 "TRIM: PITCH TRIM Wheel - NOSE UP" SimTrimNoseDown 309 0 0X57 6 0 0 1 "TRIM: PITCH TRIM Wheel - NOSE DN"
AFElevatorTrimUp -1 0 0XC8 2 0 0 1 "STICK: TRIM Up - Nose Down" AFElevatorTrimDown -1 0 0XD0 2 0 0 1 "STICK: TRIM Down - Nose Up" AFAileronTrimLeft -1 0 0XCB 2 0 0 1 "STICK: TRIM Left - Roll Left" AFAileronTrimRight -1 0 0XCD 2 0 0 1 "STICK: TRIM Right - Roll Right"
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@Stevie Thanks. I will try that.
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@jcook
callbackAFResetTrim -1 0 0XC8 1 0 0 1 "TRIM: Trim-Reset -> changeable here"
works for me. (this mapping is SHIFT UP ARROW)
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An additional question on the hat switch trim… When I use pitch trim either up or down the aircraft just climbs or descends the plane. I am wondering if pitch trim works differently than I am familiar with. As a real work pilot pitch trim is used to offset the forward or back pressure on the yoke. And you can easily trim for level flight after a speed / altitude change - you trim the aircraft and it basically flies level.
This is not what I am seeing with my Cougar joystick - I have the “Large” deadzone set, because it is older hardware, and can manage to get it more-or-less level, but I can never trim out the aircraft with the nose up / nose down hat switch. Doing so just simulates forward or back pitch on the stick.
Do other Cougar joystick users experience the same thing or is pitch trim performing a different function on the F16 than in the Cessna?
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@jcook - so, really…the Pitch Trim in the Viper does work pretty much like a Cessna, but the effect is most notable if/when you change the configuration of the jet - drop weapons, put the gear/flaps down - AND it’s effect is far more pronounced/sensitive to changes in power.
Forex - if you Trim nose up and are getting climb, you are carrying too much power and need to throttle back until you are at power for level flight (PLF) and kill the climb. If/when you transition from a Cessna to something heavier and with higher (200+) hp you’ll also notice this, and what flying a “power approach” really means. Trim in a jet fighter and/or heavier aircraft is far more sensitive to power setting.
The best way get the hang of this with BMS is to learn to land using the Indexer and to Trim/fly to on-speed (not fast, like the book would have you do) and land on-speed. You’ll note that you spend far more time flying with the throttle than with the stick.
May not sound intuitive, but once you get it, you’ve got it.
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@Stevie Ok - that’s good info. I can try that out and incorporate it into my training. Thanks!
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@jcook I think there are a few fundamental differences, not sure which you’re describing…
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F-16 doesn’t have separate trim-tabs on the elevators, the way most (?) small planes do. not sure that really makes a difference, for what you’re describing, just an implementation detail
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F-16 is fly-by-wire meaning your stick pressure isn’t directly controlling the elevators, it’s manipulating a “target nose attitude” and/or “target aoa” and the computer is controlling the hydraulics for the elevators
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F-16 isn’t stable, in aerodynamic sense… you know, in a Cessna, how if the nose dips down, speed increases, which increases lift, which brings the nose up. so it’s possible to settle into a stable equilibrium in level 1G flight, that way. not so, with the Viper
closest analog to trimming a Cessna for level flight… I sometimes use att-hold to have the flight control computer fix the nose at say 5° attitude, and then I use throttle to maintain level altitude. with attitude fixed, it becomes stable in the sense any changes in altitude become changes in airspeed, which self-corrects. and that sometimes feels “smoother” than using alt-hold, for whatever reason (real or bms quirk, I dunno)
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@airtex2019 Sir, this post was amazing. I am not a pilot but a huge wannabe pilot. And this explains some stuff so great. Thanks for sharing. And thank you all, 'cause I know there are many real pilots here with same knowledge and you all contribute to this community.
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@bbostjan I am a lapsed pilot… haven’t flown since late 90s.
I have some concept of the theory of flight but others have better understanding than me, especially re F-16
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@jcook oh ps it may be interesting to try the A-10 in BMS.
I think it has the most sophisticated flight model of the non-fbw planes.
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@airtex2019 - so, one more thing to understand about trimming a jet - or any aircraft with a powered control system - is that you are not really “trimming to relieve control pressures”. It’s more like you are simply resetting the zero of the stick in accord with the current/demanded Angle of Attack (AOA) based on your aircraft attitude to the relative wind. Control of AOA which is of most import in an E-M diagram and management of energy state (high AOA means bleeding speed/energy) during a dogfight…and/or landing.
In general - increases in AOA translate into an increase in lift…which is why you climb if you don’t decrease power with nose up trim. And why being able to know/determine where your throttle(s) belong to set PLF is an important training point.
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@Stevie said in Pitch, Roll, Yaw and Trim:
@airtex2019 - so, one more thing to understand about trimming a jet - or any aircraft with a powered control system - is that you are not really “trimming to relieve control pressures”. It’s more like you are simply resetting the zero of the stick in accord with the current/demanded Angle of Attack (AOA) based on your aircraft attitude to the relative wind. Control of AOA which is of most import in an E-M diagram and management of energy state (high AOA means bleeding speed/energy) during a dogfight…and/or landing.
In general - increases in AOA translate into an increase in lift…which is why you climb if you don’t decrease power with nose up trim. And why being able to know/determine where your throttle(s) belong to set PLF is an important training point.
Not strictly true with the F-16 I’m afraid, In “cruise” gains the trim inputs do not really have much to do with AoA as they simply change the G loading that the FLCS is trying to achieve when the controls are neutralized. If you trim to 1.5G then the Jet will try and attain and hold 1.5G regardless of AoA required to do so up until 15 degrees AoA. This is why pitch trim is barely, if ever required in cruise gains, because the 1G base trim is ideal for most circumstances, and because its not linked to AoA, big changes in aircraft config, like dropping or jettisoning weapons are handled automatically, and don’t need to be adjusted for.
Things do change in landing gains a bit, at which point the FLCS operates as a pitch rate command system until 10 degrees AOA and a pitch rate and AOA command system above 10 degrees AOA. Which is where trimming becomes much more applicable, although I can’t say I ever do.
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@SOBO-87 - yes, the foregoing is true even for an F-16. FCS Gains have nothing to do with the state to which an aircraft is trimmed, and for ANY powered control system the control forces are totally artificial…so even though you can still “fly by feel” if the system is designed properly, what the control system is actually doing/controlling is something different from what you may be feeling. This is how the Gain actually applies.
Besides - the physics of aerodynamics are still the same, regardless of the control system implementation. Thus the aircraft is ALWAYS flying at some AOA - which is the angle between the aircraft body axis and the relative wind - regardless of any control gains. In order to fly in the first place, the jet has to be at some AOA greater than the zero lift line in order to produce lift - otherwise it is ballistic.
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@Stevie said in Pitch, Roll, Yaw and Trim:
@SOBO-87 - yes, the foregoing is true even for an F-16. FCS Gains have nothing to do with the state to which an aircraft is trimmed, and for ANY powered control system the control forces are totally artificial…so even though you can still “fly by feel” if the system is designed properly, what the control system is actually doing/controlling is something different from what you may be feeling. This is how the Gain actually applies.
Besides - the physics of aerodynamics are still the same, regardless of the control system implementation. Thus the aircraft is ALWAYS flying at some AOA - which is the angle between the aircraft body axis and the relative wind - regardless of any control gains. In order to fly in the first place, the jet has to be at some AOA greater than the zero lift line in order to produce lift - otherwise it is ballistic.
I’m sorry, but you’re incorrect. In cruise gains the F-16 FLCS trims for G, not AOA. Dunno what else to tell you. If you slow the aircraft down, the FLCS will increase the AOA to maintain the selected G, and vice versa.
Your statement of
“It’s more like you are simply resetting the zero of the stick in accord with the current/demanded Angle of Attack (AOA) based on your aircraft attitude to the relative wind.”
is not applicable to the F-16 when its flying around normally. You’re welcome to dig into the FLCS system diagrams to see how it works and confirm it for yourself.
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@SOBO-87 - yes, even when flying around “normally”…trim impacts the energy state of the jet in that as the AOA increases (or decreases) to maintain 1 G, the jet slows down and runs out of (or gains) energy. This has nothing to do with the gains other than how quickly it happens, but everything to do with the physics, and the FACT that when you trim you are re-establishing the steady state (or static) condition of the aircraft wrt it’s energy required for that condition.
As an example - I had a student fly us into the ground in the Trainer that I instruct in on a low level a few times a couple days ago, for just the reasons I state.
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@Stevie I suggest you go back and re-read my first reply, where have I suggested that AoA doesn’t impact the energy state of the jet?
I just refuted your claim that trimming equates to “resetting the zero of the stick in accord with the current/demanded Angle of Attack (AOA) based on your aircraft attitude to the relative wind.”, that is an accurate statement for the vast majority of aircraft, but simply not accurate when it comes to the F-16.
When in normal cruise gains, the pilot does not have to trim (IE using either the trim hat or trim wheels) to account for the changing energy state of the aircraft, he just doesn’t. The trim only effects the G that the FLCS will maintain. So to go from 150 knots to 600 knots the only thing the pilot need do, in level flight is advance the throttle. No trimming to take account for the new energy state is required, as is required in a conventional aircraft. Now if you wish to argue that the FLCS “trims” the aircraft to alter the AOA to result in the requested G, well sure. But that isn’t something the pilot has any decision in, so isn’t really worth mentioning, and In my opinion is outside the purview of this conversation and is more about how the FLCS flies the F-16 and less about how the pilot flies the jet, which I thought was the point of this conversation.
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@SOBO-87 - this conversation isn’t about “having to trim” …it’s about making a “decision to use trim”. I don’t care what your gains are, or what phase of flight the jet is in, or if it’s an F-16 or not…if you choose to invoke Trim, you are going to have to make an associated change in throttle setting in accord with what you want the jet to do - in the case of the OP’s question, to halt climb you need to reduce power if you trim nose up.