Polar Track November: A/P wing level mode right over the NP

[19AB67 16]

Hi folks,

 

I've got a book ('Northbound Lady' by Karl Peter Ritter, German and English text) describing Lufthansa's MD11F routes EDDF/ESGG-PAFA.

The ESGG-PAFA route takes Polar Track November:

 

ESGG -D-> SABAK UL997 BBU UM609 TRM PTSN (--NORVA--LABAR=N75E011--N82E011=) NARVI N90E011 (NP!) N85W148 N80W148 N75W148 SCC J115 CQR PAFA.

 

Well, right over the pole the navigation, especially the autopilot gets into trouble: Only one heading is possible here, ie. South, but which? According to the quote book, MD solved the issue by switching the autopilot to the simplest mode: Keeping the wings level when approaching the poles to 2nm.

 

Now my question: Is it possible with the MD11 autopilot to set this mode not in the vicinity of the poles? IMU pushing autoflight at least sets heading mode. But how to set wing level actively?

 

Thanx.

[sandpatch 9]

The MD80 had such capability called turb (turbolence). It's main use was though simply to be used in turbolence. The MD11 has as far as I know nothing like it. If you press the heading button it will continue to fly the heading you are flying but but my guess is that it still is following a heading and not keeping the wings leveled.

Is my last sentence making any sense?

 

HTH,

Manfred

[xxJohnxx 21]

Hallo Andreas,

 

As I understand that book, the MD-11 will do that automatically for you. As soon as it gets close to it, it will switch to wings level.

I once planned to take off near the poles, at the Alert airport, and fly to both the magnetic and the geographic north pole. However I unfortunately haven't done the flight yet.

I wanted to see what the PDMG MD-11 does in such situations. The geographic north pole is also challenging for the FMC as the tangent of 90° is a pretty big number

Please report what the MD-11 did in that flight after you have flown it, I am very interested. :wink:

 

Schöne Grüße

 

Jonathan

[19AB67 16]

Jonathan,

 

during my flight I switched off autoflight in the vicinity of the NP, as the MD11 starts banking to the max value erratically.

So, I guess this tweak of the MD engineers was not implemented by PMDG. Fine for me.

 

My question was more on how a can set this very basic wing level mode anywhere else. I assume now that this not realised in the real MD11 at all.

[xxJohnxx 21]

Hi Andreas,

 

To my understanding the MD-11 can keep wings level when nessesary and commanded by the computer, however you can't press a button to do it manually.

 

Jonathan

[19AB67 16]

Yep, so now also my understanding. Let's fly to the pole... 8^)

[xxJohnxx 21]

Okay, I just wanted to make sure :wink:

[3-2-1-Now 126]

The reason for the wing levelling function is not because all points are south, but because the heading change is extreme, and ends up 180 degrees out of sync.

 

The aircraft will go into a coast mode over the pole, whereby the nav system will transit the pole, and once it is sure it is clear (time-based) it will reset the compass heading then resume normal navigation. No navigation system can transit the pole without coasting over the pole itself (satellites included), as the pole is technically a singularity that can not be resolved. By timing the transit, it is possible to compute where the nav system should be, based upon where it was and the earths rotation.

 

I've flown over the pole without issue, though I thiknk I had to disconnect the AP due to the lack of the transit function. I also seem to recall the compass was 180 degrees out of sync afterwards, too.

 

Best regards,

Robin.