Question about DP on IFD vs Charts differences

• If the IFD were to automatically intercept the leg GCN - BISOP versus fly course 196 to BESOP, the issue would be solved because as Catani correctly points out, GCN - BISOP define the GCN 196 radial no matter what the resulting actual magnetic course is.
  
  
• There is a step on the GRAND4 departure that has been omitted in this discussion, after 210 degrees to 7000', turn left heading 178 to intercept the GCN 196 radial. Clearly the departure description intends for the GCN 196 radial at that point to be to the left of the aircraft, not the right.
  
  
• Frequently, VOR radials do not match their magnetic courses. Nowhere in this departure diagram or text does it every indicate to fly a specific magnetic course, only headings and eventually the GCN 196 radial.
  
  
• As pointed out earlier, the IFD really works in a true world that is converted to/from magnetic for our display benefit.
  
  Knowing the true course of a VOR radial is really only good at the VOR; not necessarily at a waypoint along the radial. The further one is north or south of the equator, and the further one is primarily east or west of a VOR, the more the true course of a radial differs from the true course of that same radial at the VOR. Eastbound along a radial in the Northern Hemisphere, the true course of a VOR radial will increase. Conversely, the true course westbound along a VOR radial will decrease. The Southern Hemisphere would be the reverse.
  
  Even if one knew the exact true course of the GCN 196 radial at the GCN VOR to a decimal place or two, it will not be identical to the inbound true course of the GCN 196 radial 26 miles away at BISOP. If you could ask the IFD to fly a true course to BISOP that exactly matched the known true course from GCN, you would find that the two courses ultimately diverge. The divergence of courses would be more pronounced if we were discussing a waypoint more east or west of GCN.
  
  Fun fact...if GCN and BISOP shared the same exact longitude or both of them were exactly on the equator, then the true course out of GCN would match true course into BISOP.
  
  My point is that even if GCN were perfectly aligned with what the IFD knows the magnetic variation to be, the method of choosing to define an inbound course to BISOP exactly identical a known outbound course from GCN would still introduce some level of error.
  
  Hence my first point, automatically intercepting a leg that already connects the two waypoints and by doing so defines the desired VOR radial, would yield the most exact way to fly this DP as published.

1. The 203 heading ultimately points the aircraft for an PYE R-151 intercept SSE of WAMMY resulting in the IFD not automatically sequencing to join the PYE R-151 to SEGUL. Without intervention, the IFD map view just continues on a 203 heading until it terminates about 100NM from where the heading started, then shows a next routing direct back to WAMMY.
   
   
2. While WAMMY is physically shown on the DP overview as a waypoint located on the PYE R-151, it is not indicated that WAMMY is ever indicated as a waypoint needs to be transitioned to or over during this departure. The overview of the OFFSH2 shows even depicts an intercept of the PYE R-151 SSE of WAMMY and there is no mention of routing over WAMMY in the text description of the DP.

3. BACKGROUND.

a. Latent Hazard. Many operators are using RNAV/FMS navigation equipment to fly non- RNAV/FMS Standard Instrument Departures (SID) and Standard Terminal Arrival Routes (STAR). In some cases, because of the software programming, this has led to inaccuracies in the required tracking of the procedures. These tracking inaccuracies have resulted in less-than required air traffic control separation and air traffic control intervention to prevent a possible Controlled Flight Into Terrain (CFIT) accident. Non-RNAV/FMS procedures often require navigational tracking over all the specified fixes. Unless RNAV/FMS software is programmed to fly precisely over a given fix, it will compute, and commence, a turn prior to the fix so as to join the required track on the other side of the fix, with the minimal amount of track excursion on the outbound course. This turn anticipation could result in a turn being started miles prior to the expected turn point depending on the amount of required track change, wind, and true airspeed.

b. One Example. The WAGGE TWO DEPARTURE at Reno/Tahoe International Airport is an example of this type of procedure. History has shown that some RNAV/FMS software treat the WAGGE intersection as a FLY BY waypoint and not a FLY OVER waypoint. Because of the large course change at this fix, some aircraft have started the turn 5 miles prior to the intersection. A turn prior to WAGGE intersection may create a CFIT danger depending on the climb performance of the aircraft. This problem is not unique to the WAGGE TWO DEPARTURE but only an example of a more widespread problem.