I do not know if this is a PMDG 737 problem so let me apologise in advance if it isn't !!!!

I am trying to setup the FMC for either a BNN1C star into Heathrow 27L or 27R

OR

A LAM3A into Heathrow 27L or 27R

When I look at the Plan and am STEPping through the route using the LEGS page on the FMC there is always a big loop in both approaches. How do I get rid of these so that it looks correct.

In the case of the LAM3 arrival it should be an S curve and in the case of BNN1c it should just be a smooth curve.

By the way in both cases the aircraft actually does fly the loop !!!

Any help or advice would be appreciated.

Regards Colin

Do you been the holds at BRASO and TAWNK/LAM are they the "loops" your referring to Colin? Like the holds below e.g. BNN

 

This is the plate for 27R

 

 

Any help or advice would be appreciated.

Regards Colin

 

Full names in the PMDG forums please, Colin.

 

Thanks to David for posting the graphic... I've flown the BNN many times but never come in from the East on the LAM (sounds like a personal problem haha).

 

Couple things about the EGLL arrivals:  First, the ND path forecast is based on navdata that has been revised extensively to fit in the sidstar syntax and it's not always pretty. Second, RW arrivals are almost always vectored by ATC so the path forecast is a moot point.  Finally, it is possible to manipulate the navdata such that the forecast path looks more like the charts but it needs updated every AIRAC cycle and even an OCD flight sim addict like myself tires of that eventually.

Strictly speaking, the curves after LAM/BNN etc are not part of the STAR, but part of the approach/approach transition.

 

As mentioned above, the transition is unlikely to ever be programmed in real life as everything is vectored from the stacks in any case. As Dan says, ND drawing errors do occur occasionally (even in real aircraft): my guess would be that one of the waypoints is confusing the ND path computation. You could try stepping through and deleting one or two of the transition waypoints near the error to see if you can trap the error.

 

Personally I rarely if ever select the transition and if there's no ATC online I just use HDG SEL and fly the standard vectors (essentially as depicted on the chart above).