Speed control doesn´t work after selecting an ILS approach at the map

Question

If you select an ILS approach at the map, the approach centerline is highlighted yellow and there is a pop-up menue where You can select NAV frequency and ILS approach. The plane is well positioned just before the initial point of this approach.

Now You have to adjust the parameters of Your AP, then switch on SPD, APP and CMD button (e. g. B737-800).

After this procedure I observe that the speed of the plane is increasing more and more and will not follow the adjusted speed of the AP. In this situation the AP is engaged and the speed button is indicated green.

What is going wrong or is this just a bug?

As work around I find out, that firstly disengage theAP, secondly make a manual 360 and thirdly switch on the AP funtionalities step by step.

1. Switch on F/D

2. Switch on A/T

3. Press the speed button

4. Press the CMD button

5. If You are back on the centerline of the selected ILS Approach, press the VOR-LOC button and observe the small diamond of the glidepath indicator

6. If You are established on the glidepath, press the APP button.

After this operation the plane will follow the adjusted speed,the glidepath and centerline and the touch down will be done properly.

I am using X-Plane 11 with the latest released Version.

Answer 1

Hi, I do not understand. The normal procedure would be as described after your 360 :

1. Sim loaded, engines running, throttle at idlle or half power (I tested both situations). The speed is already set to 140 and the altitude 3000 feet. My QNH is already set.

2. Start the scenario from map menu

3. A/T on

4. FD left and right ON

5. SPEED on

6. APP on

7. CMD on

The default B738 operates the autopilot normally, intercepts the localizer and the glide very well. The autothrottle responds correctly in both situations. You need to extend the landing gear and the flaps pretty quickly because the scenario starts very close to glide interception, and it is barely impossible to slow down on the glide solpe at clean configuration.

Tested at LFOH on X-plane 11.02b1, Default B737-800, Windows 8.1.

Guillaume

Comments

Hi Guillaume,

thank You for the quick response. I´ve done it as You described. It´s works properly, if You firstly will adjust the AP at the ground and then secondly select the ILS Approach on the map.

The only thing what makes some problems is the the following point. If You switch to ILS approach the AP is disengaged in this moment. So short before the initial point You have to activate the AP again, ok only some stress for the PIC, the Copilot has a little bit fun, whether the Captain will manage this situation or not, :-))),

Until now I do not found a way to repeat my observations as described before, I am a little bit surprised. I´ve run tests at several Airports in the last hours. Everytime all is working well, "system surprise" :-))). But anyway all is working well at the moment. If I can repeat the situation again, I will give a message to You.

 

All best regards,

 

Horst K