The default behaviour when you switch on the AP in FSX with no modes selected is pitch hold and wing level hold and there is generally nothing in the annunciator panel to show that these conditions have been set. I can see that this configuration is useful after take-off to maintain runway heading and a good climb rate but to me it makes more sense that you switch the AP on, then select the modes that you want the AP to use, with the settings clearly showing on the panel.

 

I was hoping someone could let me know how the autopliot in RW GA aircraft is configured to behave when the AP is activated but no modes seleted.

Hi,

 

You can change this behavior in the autopilot section of the aircraft.cfg.

 

default_bank_mode=2 //Default to Heading Hold

 

You can change this to another value:

default_bank_mode This determines the default bank mode when the autopilot logic is turned on.

0 = None

1 = Wing Level Hold

2 = Heading Hold (current heading).

If no value is set, Wing Level Hold will be the default. Douglas DC-3( default_bank_mode=2 )

 

Miscellaneous default AP modes:

 

The following flags are legacy, and were enabled to allow aircraft to be configured with no pitch and/or bank modes. While these flags are still supported, the preferred flags are included above in the respective vertical and lateral sections.

Property Description Examples use_no_default_pitch Setting this flag to 1 will cause the default pitch mode to be "None". It will actually set the variable default_pitch_mode to zero, so that there is no default pitch mode when the autopilot logic is activated.

The preferred method is to tset the default_pitch_mode directly. use_no_default_bank Setting this flag to 1 will cause the default bank mode to be "None". It will actually set the variable default_bank_mode to zero, so that there is no default bank mode when the autopilot logic is activated.

The preferred method is to tset the default_bank_mode directly. See examples for default_bank_mode

 

Quick google search on aircraft.cfg gave this page:

 

http://msdn.microsoft.com/en-us/library/cc526949.aspx#mozTocId942782

I have already amended the aircraft.cfg file, setting the default pitch and default bank to 0, but doing so made me wander if I was doing the right thing if I want to mirror what happens in real world flights as closely as possible. Hence my question was specifically to try to understand how real world APs operate when you turn the AP on but do not have any mode(s) selected.

 

I do appreciate your taking the time to post so fully and apologies for any confusion.

I think it depends on the installed autopilot. There are a lot of different implementations around, in the real world.

Just take your pick.

 

For jets its often a seperate function, not sure of GA aircraft.

 

But I have a hard time to accept that in real life when you enable the AP the plane banks to a heading immediatly because of an automatic heading hold.

Maybe some real life pilots may chime in?

From memory, I am sure the real KFC-225 when fitted to a Cessna 340 II, would hold wings level and pitch, when the AP button was first pressed. It would be normal to almost immediately then select a lateral mode and press 'ARM' which would then use selected VS to climb or descent to the pre-dialed in altitude.

 

I believe the reason for the Wings Level / Pitch Held default command, is to prevent any unexpected changes in heading or pitch upon activating the AP ...... the required modes then being selected after AP activation.

This is normal for the G1000 C172 with either a KAP140 or GFC700. This is the default mode when the AP is engaged.

 

Also if you are in a NAV mode the autopilot will default back to wings level and not track any heading when you change the NAV source. The VS, pitch or altitude mode will remain engaged.

 

Both of these autopilots indicate what Roll and Pitch mode they are in even when in their default mode. A quick glance will tell you what it is up to.