Master Caution Lights and Beeping Upon Landing

[gary palmer]

Often when I land M2000C just after touch down I frequently set off the Master Caution Lights

(top left of cockpit) and associated buzzer sound...beep, beep, beep.

 

Not sure what is causing this and wonder if anyone has any ideas. Seems to be worse upon a harder landing? What is the fix? Can happen also upon a reasonably soft landing too. . . Gary

[Moafuleum]

It was discussed very recently. If you look one level higher inthe forum in the general RAZBAM section, it is even on the very top.

 

Here's the link

 

https://forums.eagle.ru/showthread.php?t=200034

[Martini]

Autopilot on>Autopilot off

 

This will reset the trim, the plane is telling you it's not in takeoff configuration (trim).

[Frederf]

Alarm is for trim not correct for next takeoff. Apparently best technique is to hold autopilot suspend lever on stick throughout touchdown and rollout.

[myHelljumper]

Alarm is for trim not correct for next takeoff. Apparently best technique is to hold autopilot suspend lever on stick throughout touchdown and rollout.

 

You can double tap the AP standby to reset the trim too ;).

[gary palmer]

Where is this button on the stick..does not seem to exist??

 

You can double tap the 'AP standby/autopilot suspend lever' to reset the trim too ;).

 

 

Where is this button on the stick..does not seem to exist?? Can see it in manual but is not accessible and on other side (not visible) in cockpit on stick

[Azrayen]

Why reviving this topic? :huh:

[gary palmer]

I have worked out the button is not a clickable on the stick. But answers on two posts so far are:

 

"Autopilot on>Autopilot off"

"You can double tap the AP standby to reset the trim" Does this mean LALT-A twice?

"trim before landing, by pressing on Autopilot Standby"

"Reset FBW'

"Use LALT-A to put autopilot into standby mode"

 

Nothing consistent though, so shall just experiment until one of these works better than the others.

I was looking for one straightforward action to reset trim before landing. I gather all of these are about resetting the trim to a neutral position before landing and take off.

 

Thankyou..Gary

[myHelljumper]

I have worked out the button is not a clickable on the stick. But answers on two posts so far are:

 

"Autopilot on>Autopilot off"

"You can double tap the AP standby to reset the trim" Does this mean LALT-A twice?

"trim before landing, by pressing on Autopilot Standby"

"Reset FBW'

"Use LALT-A to put autopilot into standby mode"

 

Nothing consistent though, so shall just experiment until one of these works better than the others.

I was looking for one straightforward action to reset trim before landing. I gather all of these are about resetting the trim to a neutral position before landing and take off.

 

Thankyou..Gary

 

You don't reset the trim before landing.... why would you ? :huh:

 

You land, when the nose gear touch the ground you have the decol alarm, you then just double tap the auto pilot stand-by button (ALT-A on keyboard as you say ).

 

You should map this command on you stick, you are supposed to use it all the time when flying.

[gary palmer]

Effective Solution

 

After much trial and error this is what works consistently: LALT-A to put autopilot into standby mode

before landing/touchdown which will set trim to neutral position.

 

*There is no clickable button on joystick to reset trim to neutral setting*

 

"Autopilot on>Autopilot off" does not work consistently

"You can double tap the AP standby to reset the trim" just one execution of LALT-A is enough

"trim before landing, by pressing on Autopilot Standby" cannot be pressed as in no such button available on joystick ... use LALT-A

 

Hope this helps others, as it will get rid of that annoying Master Caution Lights (top left of cockpit) and associated buzzer sound...beep, beep, beep......Gary

[bzhnono]

Don't reset trim before touchdown ! Do it just after touchdown, you should be trimmed correctly for landing and if you reset it you may experience some issues :O

 

And yes, AP standby is one of the most important button to have on the stick :)

[Frederf]

You can't reset trim while in the air. You wouldn't want to anyway. Trim should serve it's normal flight purpose until after touchdown. Trim is reset on AP suspend lever squeezed on and weight on nose landing gear.

 

It's not double-tap of L_Alt-A, just once. The alarm goes away when on the ground (nose wheel weight) and the lever is squeezed on. You can tap it or hold it for an hour. All that matters is the "begin press" event.

 

It is possible to avoid the alarm entirely if you squeeze after MLG WOW but before NG WOW. If you squeeze before MLG WOW the alarm goes off when the nose comes down. If you squeeze after NG WOW the alarm goes off. You have to squeeze between the 2-point and 3-point attitude to avoid the alarm. That's kinda silly.

 

No Action -> MLG WOW -> NLG WOW -> Alarm

Squeeze -> MLG WOW -> NLG WOW -> Alarm

MLG WOW -> Squeeze -> NLG WOW -> No Alarm

NLG WOW -> MLG WOW -> Huge Firey Crash

[myHelljumper]

NLG WOW -> MLG WOW -> Huge Firey Crash

 

Challenge accepted ! :D

[Azrayen]

Don't reset trim before touchdown ! Do it just after touchdown, you should be trimmed correctly for landing and if you reset it you may experience some issues :O

 

And yes, AP standby is one of the most important button to have on the stick :)

 

Agreed with both those points.

 

This is straightforward, and by the way this is also how it's done IRL.

 

Pre-requisite: Have the AP Stand By button mapped on your joystick. For those having a HOTAS Warthog, my personal advice is to use the "trigger" in front of the stick for this mapping.

 

 

Now, the sequence:

- aircraft with AP On (green) takes the approach path

- at 200ft or before, the pilot shuts off the AP; there is also a button for this on the stick (*)

=> the aircraft is now flown manually, and has been trimmed for correct approach by the AP before it was shut off

- land the aircraft (flare, touch down)

- during the aerodynamic braking (main wheels on the ground, nose wheel still in the air), press once the AP stand by.

=> the trim is resetted to default T/O setting; hence no alarm will be triggered when the A/C will sense it has all wheels on the ground

- before deccelerating to 100kt, land the nose wheel

- use wheel brakes (and parachute if emergency/abnormal situation)

- vacate runway, taxi to parking

- debrief, have a beer.

 

++

Az'

[Azrayen]

That's kinda silly.

Is it? I feel it's totally logic.:huh:

[Frederf]

Take example of AP approach to 100' and then AP standby is squeezed. Then there is round out to touchdown. About 80 knots nose is lowered to contact runway. Alarm! Danger! Death!

 

It makes no sense. Every pilot action has been reasonable. There is a straightforward method to design trim reset and alarm logic such that AP standby held throughout landing is acceptable. The only concern is that trim is not suitable for next takeoff. So it is desired that trim is set for T/O sometime during the landing. What is the smartest time to do this action?

 

In between 2-point and 3-point attitude I say is a stupid time! Workload is high. Changing trim here may upset the airplane aerodynamically. What happens if the act of releasing AP standby in the two-point attitude in order to reapply it the AP resumes flight control? WOW sensors are notoriously unreliable especially in the transient light loading of the two-point attitude near touchdown speeds. It's entirely possible to have AP green while on the ground (shouldn't WOW suspend AP?).

 

Why not wait until the 3-point attitude to reset trim? Make NLG WOW + AP Standby = reset trim. Now you take the same situation as before: coupled approach, squeeze to round out, MLG touchdown, NLG touchdown, trim reset, release AP standby. Safer, less work, compatible with rejected landing, everything!

 

===

 

Then there is the question of rudder trim. The yaw trim changes dramatically on MLG WOW regardless of pilot button input. Try setting full yaw trim and then countering it with pedal input before landing. The nanosecond you land the gains change and suddenly your centered rudder jumps to about 50% on the side of the pedal input. It's crazy!

 

Do the same trick with aileron trim and you find that if you trim roll fully one direction and then apply left stick you'll see the commanded rudder position is not centered! Clearly if the combination of aileron trim and stick roll input exactly cancel then the commanded rudder position should be identical to the situation where there is no roll trim and neutral stick roll input (i.e. exactly center). It's not. The ARI needs to be based on actual commanded roll.

[Winterz]

First, you are going for three points before 100kts, 80kts is way too late.

 

Second, In real life the pilot does press the AP Standby when he got his hands on the stick so the problem ain't the same as in our sim.

[Frederf]

I knew someone was going to mention that specific 3-point speed. The exact speed is immaterial.

 

I have a stick where I can hold AP standby at will. Recognize that if you hold AP standby throughout the landing you will get the alarm. To avoid the alarm from an autopilot approach you have to hold AP standby, transition to the two-point attitude, release AP standby, press AP standby, and then transition to the three-point attitude.

 

It's really fiddly. I don't see why the design couldn't be one where you press AP standby before touchdown and hold it throughout the rollout.

[Winterz]

I have a stick where I can hold AP standby at will. Recognize that if you hold AP standby throughout the landing you will get the alarm.

 

Well I thought the alarm din't pop up when keeping it pressed. Anyway I just press Autopilot standby to get rid of it and I dont get why people think it's that ankward.

[Azrayen]

Take example of AP approach to 100' and then AP standby is squeezed. Then there is round out to touchdown. About 80 knots nose is lowered to contact runway. Alarm! Danger! Death!

I don't agree that it's "crazy" or "unacceptable"; but then I don't understand what you mean by "Then there is round out to touchdown".

 

Remind that in the real aircraft, if you have the stick firmly in hand (which you DO when you pilot a landing), then you press the AP standby; by design; without thinking it.

You would have to let go the stick to get to the "AP standby not pressed" situation.

=> This is what pilots do, consciously: they open their fingers, the AP stand by gets unpressed = the trims are resetted, then almost immediately they close their hand on the stick and resume manual flying (the AP stand by get re-pressed of course as soon as they close their hand on the stick).

 

What you were expecting: trim reset while AP standby pressed.

What is (correctly BTW) happening: trim reset when AP standby is released.

 

++

Az'

Edited February 10, 2018 by Azrayen

[Frederf]

In DCS M2000C the trim reset happens when AP standby is pressed, not on release. It is easy to test. From runway start give some rudder trim, alarm sounds immediately. Press but do not release AP standby button, alarm stops. While holding AP standby add rudder trim and alarm resumes. Alarm continues when AP standby is released.

 

I am not saying "unacceptable" just that it is surprising. These are minor details but engineers for human interface and flight control systems are notorious for attention to fine detail. I think it is like having to push missile launch button twice to fire. It is not a severe problem but makes you ask why.

 

Round out is another term for flare or transition from approach attitude to landing attitude. You can replace it with "And what happens next is main wheel touchdown" with no change in meaning.

[Azrayen]

In DCS M2000C the trim reset happens when AP standby is pressed, not on release. It is easy to test.

OK you're right on that. :)

The fact remains that you can't just maintain AP standby from before touching down, because then the trim will have been set when you were still flying, and assuming correct approach flight path, it won't be neutral trim.

So, in effect, the virtual pilot maintaining the AP standby pressed during touch down will, like the real pilot, have to release his grip, then press it again, to get the alarm off.

You may say (and be right) that the RL pilot would only need to release it, but remember where is this command in the RL aircraft: I you take the stick in hand firmly, you press it!

 

I think it is like having to push missile launch button twice to fire. It is not a severe problem but makes you ask why.

Uh? I didn't ever have this on the 2000. Not now, not earlier. :huh:

 

Round out is another term for flare or transition from approach attitude to landing attitude. You can replace it with "And what happens next is main wheel touchdown" with no change in meaning.

Oh, OK thanks :thumbup:

 

Take example of AP approach to 100' (...)

Not that important, but anyway: you're supposed to switch off AP at or before 200ft height in this aircraft. :book:

 

Regards,

Az'