L-1011-250 A/P question

[radioguy]

Greetings -

I've looked in the Lockheed board and can't find a similar question so if it's been asked/answered/moved, please advise.

I'm able to set a good VS and good speed to get up to altitude, level off, etc., at which point the VS light switches to ALT.  That's fine, but why can't I select MACH without it releasing the ALT function?  Shouldn't I be able to switch between, say, IAS and MACH without it disengaging ALT or VS?  What I end up doing, once at cruise level, is let the ALT switch stay on, then turn off A/T and manually monitor throttles to maintain a certain Mach speed. 

Other aircraft allow switching between VS/ALT and IAS/MACH.  Is that just not available on the L-1011?  I've had this situation on at least one other aircraft so I brought in the stock FS9 A/P from the stock FS9 737 because (a) it works and, (b), it lets me adjust the IAS and Mach settings.

Other than my question above (and the wild swings with the vertical trim setting which I just deal with and get over it), it's a nice aircraft to fly.

Thanks.

George

[Peter Liddell - HJG Admin]

Hi George

I'm not sure what's going on so I'll try to replicate it.

Are you using the Tape or Standard panel?

[aerofoto - HJG Admin]

In IAS PITCH MODE (used below 25000 FT) the AP will constantly adjust the ROC .... in order to try'n maintain an acquired IAS airspeed .... and the same should be true of MACH PITCH MODE too (used above 25.000 FT).

AT functions in these simulations are annulled when using either AP IAS or MACH PITCH modes .... so far as I'm aware.

Any manual power adjustment/s during either AP IAS or MACH PITCH modes will cause the pitch to change .... power increases will cause the AP to increase the ROC .... and power reductions will cause the AP to reduce ROC .... that's all quite normal, but, if mishandled such could well result in excessive oscillation/s.

During AP controlled IAS pitch adjustments any VSI gauge indications may seem to be "quite acute" .... BUT .... in FS external viewing mode such adjustment/s don't appear to be anywhere near as acute as the VSI gauge suggests .... except in cases of excessive manual power adjustment/s. This has been reported/discussed previously .... approximate 2 or 3 years ago.

In regard to the ALT function .... ALT MODE can only perform a capture and "hold" if the ALT mode is first "ARMED".

I'm not aware of ALT HLD being disengaged by AT mode .... at least it never used to be .... unless we broke something when we uploaded the new gauges suite with the revised/improved WX Radar late last year.

I brought in the stock FS9 A/P from the stock FS9 737 because (a) it works and, (b), it lets me adjust the IAS and Mach settings.

I'd advocate extreem caution doing that ....

1. Because we can only provide support for what we produce

2. Because other editing or additions can't be guaranteed to work perfectly with what we provide .... a movie we've seen a number of in the past.

Mark C
AKL/NZ

[aerofoto - HJG Admin]

Here's that earlier discussion re AP IAS and MACH PITCH mode ....

tonymadgehjg.proboards.com/thread/7202/ias-function

As I hinted above .... and as was noted previously too (it was during 2014) .... there's definitely a very slow, but, noticeable reflex/oscillation displayed by the VSI gauge when using either AP IAS and MACH PITCH modes, however, as I mentioned above, and as is referenced within the above linked thread also, this oscillation was hardly noticeable, at all, in FS external viewing mode.

I'll look at the AP ALT HLD versus AT IAS/MACH function later (got a fair bit on my plate at the moment with R/W priorities), but, I don't recall ever experiencing such an issue .... and don't recall any such issue ever having been previously reported either.

Mark C
AKL/NZ

[aerofoto - HJG Admin]

I'm able to set a good VS and good speed to get up to altitude, level off, etc., at which point the VS light switches to ALT. That's fine, but why can't I select MACH without it releasing the ALT function? Shouldn't I be able to switch between, say, IAS and MACH without it disengaging ALT or VS?

I see what he's been doing.

This all appears to be an innocent misundertanding of how the AP and AT systems both function.

There's no problem with either the panel/s or their systems .... everything's working correctly .... and nothing needs to be edited or replaced

Allow me to explain

I've just performed a T/O and climb to cruising altitude/31000FT using the L-1011-150 .... FYI the AP and AT systems in each of our L-1011 simulations function identically.

After T/O and clean up I engaged the AP.

I then engaged AP VS climb mode .... then selected and initial ROC of 2500 FPM.

I then selected a target altitude/31000 FT .... and engaged AP ALT ARM.

I also then selected a target airspeed of 295 KTS .... and engaged the AT .... at around 285 KTS.

Other than applying subtle manual adjustments to the ROC at various intervals between 10000 FT and 31000 FT .... along with modest airspeed adjustments too .... nothing else needs to be done apart from whatever navigational adjustments are necessary using AP HDG and AP NAV modes. For these basic AP and AT settings the simulation will automatically find it's way up to the target cruising altitude and level off .... with airspeed being controlled by the AT.


I think the key to undertanding the reported issue is to remember that the AT .... which controls airspeed/velocity .... functions independently of the AP.

Using the AT .... only IAS airspeed is selectable .... per the selector knob located below the AT switch.

MACH velocity is displayed within the ASI gauge .... in accordance with the actual IAS indication too .... but .... an actual AT MACH value can't be selected .... again only AT IAS values are selectable.

HERE'S WHERE HIS CONFUSION ARISES .... I think ....

When the simulation captures any target cruising altitude, and assuming AP VS mode has been engaged .... and assuming the AT has also been engaged with a selected/target IAS too, then, upon acquiring the selected/target cruising altitude both AP VS and AP ALT ARM indicators will auto-disengage and AP ALT indicator will auto-engage .... in order for the simulations capture and maintain the selected/target altitude.

If he's then been selecting either AP IAS or AP MACH modes .... probably mistaking these for AT modes, then, that's a misunderstanding.

Doing such will disengage both AP ALT mode and the AT too. This's how the AP and AT are supposed to function in these simulations .... and how they "do" in fact work.

Remember .... AP IAS and AP MACH are "pitch modes only". Their only relationship with speed is during either climb/descent and is via the AP .... which adjusts the actual pitch of the simulation in order to try'n maintain the airspeed/velocity that was acquired when either mode was first engaged.

Once the AP has established the simulation in the cruise .... then .... these AP pitch modes (like AP VS mode too) have done their job and are finished with. AP ALT mode then controls altitude .... and .... speed is controlled using the AT with the actual airspeed/velocity both being displayed within the ASI gauge.

Using AP VS climb mode the above is all that needs to be done (apart from using AP HDG to intercept a previously selected VOR course) .... and can be engaged from almost immediately after T/O.

AP IAS PITCH mode shouldn't be engaged until about 10000 FT .... and only once an airspeed of approximately 290 KTS has first been acquired.

AP MACH PITCH mode shouldn't be engaged until about 25000 FT .... and only once an airspeed of approximately 300 KTS has been acquired.

If either AP PITCH mode are engaged too soon .... or at too slow a speed .... then .... such could intensify any pitch hunting evident per the VSI gauge as the AP may struggle to maintain a selected airspeed/velocity using constant and automatic pitch adjustments.

If engine thrust is manually increased/decreased after engaging either AP IAS PITCH or AP MACH PITCH modes .... then this will influence the ROC/ROD positively or negatively also .... with the added danger of a constant and increasing vertical oscillation then becoming evident.

The rest is as reported within my previous above 2 replies .... and within the above-linked 2014 discussion too.

Mark C
AKL/NZ

[aerofoto - HJG Admin]

It's recommended that our forum based/online L-1011 manual be referenced for description/s regrding all procedures ....

L-1011 bASIC INSTALLATION & HANDLING NOtES
tonymadgehjg.proboards.com/thread/3888/l1011-tristar-panel-installation-handling

This manual covers "almost" everything that must be known in order to be able to use these simulations properly/derive maximum enjoyment from them.

The following is "a very basic procedural guide" for our L-1011 simulations using AP VS, AP IAS, and AP MAcH pitch mode options .... again this is "A VERY BASIC/ROUGH GUIDE ONLY" ....


AP VS PITCH MODE

- Engage AP after T/O .... set "CMD" mode ("CWS" mode is also available but cancels "CMD" mode).
- Set and engage AP VS mode as required (2500 FPM clin recommended at MGW).
- Set target altitude as required .... and engage "AP ALT ARM".
- Set and engage AT as required (290-295 KTS climb recommended .... 295-290 KTS descent recommended).
- Set and engage AP HDG mode as required.
- Set and engage AP NAV mode required .... or engage pre-programmed INS NAV.
- Adjust AP controlled ROC throughout climb to cruising altitude.
- Adjust AT controlled IAS airspeed throughout climb to cruising altitude .... MACH velocity is indicated within ASI but only IAS can be engaged.

Simulation will climb/descend to selected altitude in accordance selected ROC/ROD and AT controlled airspeed/velocity.
AP VS PITCH mode cancels both AP IAS and AP MACH PITCH modes.
AT remains available throughout climb, cruise, and descent.


AP IAS PITCH MODE and AP MACH PITCH MODE

- Engage AP after T/O .... set "CMD" mode ("CWS" mode is also available but cancels "CMD" mode).
- Set and engage AP VS mode as required (2500 FPM recommended at MGW).
- Set target altitude as required .... and engage "AP ALT ARM".
- Set and engage AP HDG mode as required.
- Set and engage AP NAV mode required .... or engaged pre-programmed INS NAV.
- Accelerate to 290-295 KTS climb .... decelerate to 295-290 KTS descent.
- Engage AP "IAS" pitch mode "at approximately 10000 FT" upon acquiring 290 KTS (climb) .... switch to AP "MACH" pitch mode "at approximately 25000 FT" upon acquiring 300 KTS (climb).

AP IAS PITCH mode should be used between 10000 FT and 25000 FT and only and between 290-295 KTS.
AP MACH PICH mode mode should be used between 25000 FT and cruising altitude and only and between 295-300 KTS.
AP will adjust pitch (ROC/ROD) to maintain speed acquired when either mode is first engaged.
ROC/ROD is determined by AP IAS/MACH PITCH modes.
AP IAS/MACH PITCH modes cancel the AT
AP IAS/MACH PITCH modes cancel AP VS PITCH mode.
AP IAS/MACH PITCH modes cannot be engaged during cruise .... these are climb modes only.
Power may be manually adjusted during climb/descent but any such adjustments should be applied cautiously/subtly .... power adjustments will impact airspeed/velocity and ROC/ROD.


Kindly be aware HJG can only support the files it offers so long these "ARE NOT" modified .... this implies editing and additional utilities "not" offered by HJG as part of it's simulations.

Given the complexity of some of the FS logic associated with what we offer it cannot be guaranteed that such modifications won't adversely impact what we provide.

Mark C
AKL/NZ

[radioguy]

Hi again -

Your step-by-step info is pretty much what I do. I just thought that if I were at say 30000' and, just as an example, wanted to set a Mach speed of, say, .75, I assumed if there was a MACH button on the panel that selecting it would hold a Mach preset...if there was a preset. Oh well. I guess it's one of those, "You can't there from here" deals. No biggie. I'll survive and the sun will come up tomorrow morning as scheduled.

Thanks to you both for your expertise. The biggest plus is that you actually answer questions. So many boards don't. I appreciate it.

George

[aerofoto - HJG Admin]

Once again .... there's no relationship between MACH velocity and the AT .... MACH HLD "is not" available.

Only AT IAS can be selected/engaged.

The selectable IAS and MACH tabs (on the MCU) are AP Pitch modes .... for climb and descent only. Engaging either of these modes during AP controlled cruise will (intentionally) disengage both AP ALT HLD and the AT.

That's how it's all intended to work .... with these simulations

The biggest plus is that you actually answer questions. So many boards don't. I appreciate it.

We try .... "very hard" .... to support what we offer in order to help people enjoy it and usually with a greater than 90% success rate

Thanks for taking the time to comment .... "appreciated"

Mark C
AKL/NZ

[radioguy]

It's finally registered in my head that, guess what?, there's no Mach hold. As the years go on, it sometimes takes a little longer for information to burrow into my brain.

Thanks again for your patience.

[aerofoto - HJG Admin]

YEP .... that's what I was trying to say ....

Only AT IAS can be selected/engaged.

No worries "RADIOMAN" .... you got there .... and that's the main thing

Mark C
AKL/NZ