GLS/RNP vs LPV
Aterpster,
I agree with you 100%. As an individual that is involved with procedure design and has design many and flown hundreds of LPV approaches, LPV is a vastly superior system than GLS/RNP. I state that for the following reasons:
Procedure Design
- the design criteria affords a very tight final, tighter than RNP (even 0.1 in close). There are a handful of places in the world where RNP 0.1 would yield lower approach limits than LPV
- the vertical path of RNP, being barometric altimetry driven, is subject to all of the barometric altimetry problems in both warm weather (a flight path angle that is steeper than the nominal path) and cold weather (flatter than the nominal path). As well, there are temperature restrictions at both ends of the temperature spectrum
- GLS may solve the barometric altimetry issue however it creates many others (discussed shortly)
- LPV uses satellite-derived height, thus eliminating all of the limitations of barometric altimetry
- how would it work at airports and not just the ones where airlines go exclusively? For each runway end there would be an GLS/RNP approach for the airliners and an RNAV (GPS and LPV) for the bizjets and GA aircraft?
Financial
- North America is covered with WAAS coverage; my understanding of the European Galileo satnav system is that it will have the qualities (accuracy, integrity, etc) to support Cat 1 ILS like approaches, ie LPV/APV
- with WAAS the navigation source is free; with Galileo it will come with a small licensing fee
- Galileo will have worldwide coverage
- GLS means, last time I heard, a $3 million per airport investment in the ground infrastructure; the investment in the aircraft to either install new multimode receivers or modify the existing ones is massive (last I heard about $250K per box)
- naturally, Honeywell, Boeing, Airbus and the others would love to have the airports and airlines pony up that kind of dough
- it is interesting to note that a brand new, certified WAAS receiver from Garmin is about $14K; upgrading an existing box to WAAS is $3K. Why Honeywell and the others can't do it for something similar (or even double) is beyond me.
- $3 million per airport times how many airports? Big, big dough.
- Given that there is no operational benefit there is no financial benefit from the cost to the industry of GLS boxes on the ground and expensive MMR's in the aircraft
With the knowledge the industry has with LPV/APV and with Galileo on the threshold of operational capability, the only logical and financially responsible solution is LPV/APV - airlines should be pushing the avionics providers to get with the program and upgrade the existing GPS's and FMS's to a WAAS/Galileo capability that would provide the best operational capability with the lowest (by a large margin) implementation cost to the industry.