Runway Elevation and Threshold Crossing Heights

[Guest shogun007]

The problem that I have is as follows: YMMLThe RWY 16 threshold information in the wpNavAPT is correct at 432ft. The RWY 34 threshold information in the wpNavAPT is correct at 330ft. When a RWY16 ILS App is loaded into the PMDG FMC it creates a Threshold Crossing Height (TCH) of 330ft. This is 102ft below the level of the RWY16 threshold, but would be correct for a RWY34 ILS (but without the additional 50ft TCH) There is no facility to program a TCH into the star coding so the FMC (ie PMDG) must get it's RWY information from the wpNavAPT file. The RWY 34 Elevation is correct at 330ft, I changed it to 600ft and the FMS loaded a TCH of 600ft for the RWY16 ILS App, and also for the RWY27 ILS App. After trialing different data in the wpNavAPT, I have deduced that the FMS (PMDG) looks at the lowest RWY elevation for the longest RWY and NOT the actual data for the RWY App in use. I have also come to the conclusion that the PMDG 744 is not adding 50ft to the RWY Elevation for the correct TCH.I am interested to hear comments and feedback from PMDG and its users. Regards Steve Power

[Chris Wright 0]

steve...your deductions are indeed correct.the add-on processes all rwy alts as that listed for the last rwy listed at the specified aerodrome in the wpnavapt file.so if rwy 34 @ 330' is the last one in the list for mel in the above file, that's taken as the aerodrome alt for all rwys.how to fix it? there's no easy way - for fs9 add-on's it'll be something you need to live with as i doubt further development work would be envisaged to fix the prob for those versions.you can of course adjust your approach alts from the relevant approach plate limits as part of your descent planning.hth!

[downscc 1,327]

FS9 forces all runways to the same elevation. It doesn't accomodate runway slope at all... the entire airport (runways, ramps, etc) is at one fixed elevation - often at least several feet different from real world. Oops... there I go again poking fun at the "as real as it gets" tagline. Sorry.I would like to see an ability to program the IAP with touchdown zone coordinates and elevation, and threshold crossing... but, we're still restricted to following the simulated FS9 ILS which often has the GS not at the exact spot, Localizer colocated with DME, etc.... The fidelity of the FS9 ILS system is marginal.