When to use SSHS Disconnect?

[DimSim]

It's right there on the stick, but under what scenarios should one use the Emergency SAAHS Disconnect?

[WeakLink]

I find any time you feel that the trim is running away. The A/C seems to be dancing up and down apply SAAHS Disconnect and the Caution lite will flash, level the A/C and let go of the disconnect . My disconnect is paddle switch + autopilot button, I use a TM warthog. But in reality use it anytime it just disconnects the Autopilot from the trim/ resets trim to neutral. 

 

WeakLink

[DimSim]

I wish it did reset trim.  As far as I can tell, 'Emergency SAAHS Disconnect ' does nothing more than flip the AFC off.

It does not turn it back on upon release, reset trim or turn off any of the three stability controls.

 

Test by turning on AFC + Alt Hold.

Throttle down. 

Observe the trim pitching up as your air speed drops. 

Try disconnect SAAHS.

Observe changes.

 

Realized I made a spelling mistake in the thread title, but can't edit now after forum upgrade.

Edited December 2, 2020 by DimSim

[DimSim]

Spent some more time playing with this last night.

Still not sure of any useful effect other than disengage auto pilot (AFC).

 

The scenario is when AFC causes trim to be at extreme position, so when you take control the aircraft wants to pitch.

Fighting against the trim is difficult and manually resetting trim is time consuming as it moves very slowly.

There is a chance pressing emergency disconnect after getting to level flight may help reset trim.

I'm not sure it does anything. Pressing Active Pause also helps AFC to reset. Other times it seems to reset at random.

[WeakLink]

I'm not sure how you  want to use SAASH reset, it I believe it is there to help U control a (runaway trim) that is when I apply it. And yes it turns off your autopilot and puts you back in control of the A/C. I find that it resets the trim to neutral position and allows  you to gain control of the aircraft. I have a TM warthog and I have the reset on the autopilot and combined with the paddle lever as a second level command so; for me when the AP is on/engaged and the A/C pitch's up (the usual A/C performance) and I don't wish to wrestle with it I engage the SAAHS reset, a quick engagement and if needed a longer engagement to control the A/C very rarely used in a nose down position (if ever). When it come to turns in the flight plan I convert ground speed to miles per minute, determine how many miles I need to make that turn (considering your ETA to point) so now I have a turn short point, and at that point (the est. turn short point) I 1. turn Autopilot off. 2. Start turn and use the rudder if the turn exceeds 30 degrees(hold altitude much better) 3. level out on course, engage autopilot. I have found that if the autopilot is engaged during the turn it tends to double the set trim attitude you have set causing pitch up and Attitude Hold disengaging and fighting with  the A/C again to control it. I hope I answered your question, and yes the Autopilot needs attention, with  a few flaws. Should have been flying it the day it came out boy that was a ride! What we have now is heaven.

[DimSim]

Thanks for your continued responses @WeakLink.  I carried out quite a bit more testing, but am not getting consistent effect resetting the trim with 'Emergency SAASH disconnect'.

When the trim has 'runaway', I've tried using the SAASH disconnect button and the AFC Off button.  Both turn AFC off. I've only ever seen trim reset on AFC On. 

If you are consistently able to reset a runway trim, that is not something I have been able to reproduce.  That is also the only thing that is useful to me. So if it's possible, I want it.

I've also tried the 'Automatic Flight Control Reset' input binding.  That had no effect for me.

Can you please check which bindings you have ie. 'Emergency SAASH disconnect',  'Automatic Flight Control Reset', 'Automatic Flight Control On/Off/Toggle'.

I have 'Automatic Flight Control Toggle' on throttle button and 'Emergency SAASH disconnect' on stick lever button similar to warthog.  I assume you have the same, but the wording of the sim bindings and our discussion is not precise.

[WeakLink]

Hey DimSim as I said I have a TM warthog stick. On the throttle unit I have a autopilot button, as you might know the warthog is capable of layered programs levels, so for the most used actions are on the main level, and the secondary level are items that are niceties. When I want to engage the autopilot the (AFC control) I level the aircraft and engage the button. After I have levelled  the nose, the Altitude Hold function is on the landing gear horn button.  The reason I do not put Altitude hold on the secondary function of the autopilot is 1. I do not use it unless I'm level flight for any length of time high or low. 2 I find it temperamental and finicky.  3. the button maybe out of sync. (occasionally I fail to use enough pressure to activate the autopilot button) This also forces me to look at the SAAHS panel and ensure that the autopilot and altitude hold is engaged. I find that I use the disconnect 95% of the time when I start a turn and fail to disengage the autopilot before the turn, upon roll out the autopilot has almost doubled the pitch input and lost the  ability to maintain level flight. As suggested by RAZBAM_ELMO the autopilot will attempt to recover to level but may absorb the input that U the operator applied. For turns  up to 30 degrees I use the autopilot, anything greater I disconnect and fly the turn myself rollout and engage the autopilot. By using the paddle leveler  at the bottom of the joystick I activate the second level of the program, by using the paddle switch as a modifier, it is much easier to access the secondary level of programming. Now to activate the reset button U engage the paddle switch first then push and hold the autopilot button until U feel you can regain control of the A/C. I find a short press on the dual function and the control is regained, sometime a longer press of the function is need to gain control. I find it personally that a lower airspeed will cause a longer press i.e. less than 300 IAS will cause me a longer engagement of the function to regain control of the plane. I do not use the Automatic Flight control Toggle in my setup, (toggle implies ON/OFF or OFF/ON and it very easy to confuse where you are with that switch). For instance if you use the "Synchronize control of HOTAS at startup" under the tab MISC then where is your switch or button at when you start?? I don't check it and I don't use that function. I just the Emergency SAAHS Disconnect. The Automatic Flight Control maybe causing some conflict in your autopilot controls. Just use the Emergency SAAHS Disconnect and take control of the A/C and then engage the AFC (autopilot) again.

[DimSim]

5 hours ago, WeakLink said:

By using the paddle leveler  at the bottom of the joystick I activate the second level of the program, by using the paddle switch as a modifier, it is much easier to access the secondary level of programming. Now to activate the reset button U engage the paddle switch first then push and hold the autopilot button until U feel you can regain control of the A/C.

I'll have to test some more. I think you're saying:

 

1) You only have bound

Automatic Flight Control On (not toggle)

Emergency SAASH disconnect

Altitude hold On

 

2) Your disengage, reengage sequence looks like

SAASH disconnect

maneuver aircraft

Hold Emergency SAASH disconnect

Hold AFC On, until control is regained

 

I didn't realize AFC On could be held.

 

EDIT: Tried holding AFC On. Seemed to have no effect. If it could engage it would. If it could not engage, it would immediately flip back off. Holding had no effect. Instead I must press AFC On repeatedly to try again.  Holding SAASH disconnect appeared to persist as long as I held the lever button.  In all cases, trim only reset when AFC actually turned on.

Edited December 13, 2020 by DimSim

[WeakLink]

 Hey DimSim, my AFC switch is keybound to ONE button. I do not use the mouse to engage the AFC switch. It sounds as if you use the mouse to engage the AFC switch, I assume it should engage in the same way my Keybound ONE Button does if not then one of two things are happening, your AFC switch is double bound somewhere in your controller program, So I recommend you go through each sub heading of your key binds and check for a second binding.  The other problem might be the A/C if not level when you try to engage the AFC, I believe it is less than 5 degrees off level but you should check the manual on that one and the Altitude Hold also has a restriction on the degrees level you must be, to engage/activate the switch.

 

 So the process for me, A/C starts to pitch up( usually after a turn where I failed to disengage the AFC switch ((button push) for disconnect, or I disconnected the AFC switch seconds after I started turn and the AFC absorbed the trim I was applying prior to turn)) In the first case at roll out I  have to  disengage AFC, leave it off longer to get control of the A/C. Because of the way I have it setup, Paddle switch (as modifier and the AFC BTN when modifier is engaged becomes the AFC disengagement switch) I can maintain a view of the HUD and level the A/C as required, reset my trim within the required level parameter for the AFC and ALT Hold to engage. For me the length of time it takes to regain control seems to depend a lot on the speed (IAS) you are flying. Below 300IAS it seem it takes a bit loner to react to my inputs and above 300 IAS it appears quicker to react  to joystick inputs. 

If you are using the mouse to engage these switches then you are not looking at the HUD, So I suggest you bind them to single keys on the key board or your joystick or throttle. I use the Keybind "Automatic Flight control ON/OFF (A)". so in reality I only turn the AFC on or off. The Reset function is never activated, on that switch. The reset on that switch is not a toggle and stays engaged until U turn it off so the ZERO function it provides is never obtained with my action (AFC switch aft to OFF and re-trimming the A/C is part of my visual observation of the A/C performance and the HUD visual cues. As far as I can see if you use the reset function it is suppose to ZERO out the trim inputs and U are still in a lurk, and will have to retrim the A/C. So why not cut out the middle man, turn the AFC off, retrim and then turn the AFC back on and the Attitude Hold back on. 

Disconnecting the AFC switch (off) will also disengage the altitude hold switch so you basically have a new slate just correct the trim and reset/engage the autopilot. If you use the AFC reset remember it locks in the reset position and must be deactivated to retrim the A/C. Engage the Reset, gain control of the A/C and then deactivate the the Reset, trim the A/C and engage the AFC and Hold again. And all should be well.

[DimSim]

I think we're doing almost the same thing.
I use a HOTAS with 'AFC Toggle' and 'Alt Hold' buttons bound.
After reading Chucks guide, wondered about the 'SAASH Disconnect' because he shows it on the HOTAS setup, but never mentions it again.

 

We're speaking in circles a lot, so I'll try re-phrasing my question:
1) When the trim is in extreme position, is there a button you press that always centers the trim, other than AFC On?

(AFC On will re-center trim, but only if it actually turns on.)

2) Asking another way, do you ever have to manually center trim from an extreme position?

(Or is there a button that re-centers trim for you any time it's pressed.)

[WeakLink]

Hi DimSim, As to question 1 the answer is no, either you reset the trim i.e. AFC switch to far back position and recover the A/C  or you turn AFC off, regain control of A/C and when in parameter set AFC  back to on. There is no automatic re control of the A/C, the Harrier is a stick and rudder A/C YOU are in control at all times, AFC is just a pilot relief item. It too requires care and feeding. As for question 2 there is the reset function, if you find yourself in a position that is radically different from what you desire and if you think its the trim either reset the trim by pushing the AFC switch to the reset position, return it to AFC OFF, regain control of the A/C and and use your trim hat to reset your trim parameters, re-engage the AFC switch and you should be OK.   The reset button only zeros out trim and does not apply the correct amount of trim needed to fly straight and level. Say U are at 20,000, starting a dive to TGT and you want to hold 420 TAS or 20 degrees in the dive, first you nose over set the dive angle, control airspeed with slight idle throttle , or airbrake line up on TGT trim off control pressures continue dive and bomb-a-way start your pull out and re-trim the A/C. Your trim can make life easy or hard, when I was in flight training my instructor use to hammer and that was Cesena, and to this day it has not changed!!!!!. ( FLY the DAM Airplane ).

 

 

WeakLink

[DimSim]

Thanks WeakLink, I'll have to experiment more with that AFC Reset.

[WeakLink]

DimSim good luck, and just remember the AV 8 is a beast, Never let it fly you, just "Fly the Dam Airplane" and you will be ok. Happy Holidays!!!!!!!!!!!

 

WeakLink