In my “personal” wording, fuselages made of composite are called “plastic planes”. By extension, diesel engines are “plastic engines” and glass-cockpits “plastic instruments”. Something is modern ? Call it plastic. What I forgot until today is an important part of the IFR system: approach procedures. Not only plastic approaches exist, but in the USA there will soon be more numerous than classical ILS, VOR and NDB approaches.

Plastic approaches ? Yes, I’m referring to WAAS, or GPS approaches. I flew a couple of them in France, but they were not comparable to the WAAS version. The one I flew were non-precision approaches – no vertical guidance was provided. The CDI was driven by the GPS, and I had no glide-slope indication. The WAAS approaches now in use also include vertical guidance, but they require special on-board equipment.

From a navigation point of view, flying such an approach is extremely easy. No navaid to identify, no change of ILS / VOR / DME frequency during the approach, no need to switch from GPS to VLOC (all GNS430 / 530 or G1000 users will understand). As there are no more constraints related to beacon locations, or radio-signal coverages, it is possible to fly direclty to final approach, unless otherwise required for traffic separation.

Another great benefit of WAAS approaches it that no equipment at all is required on ground. No ILS, no VOR, no NDB. Almost any airport can be “equipped”. I don’t know all the subtleties of the requirements – which for classical approaches include runway markings, lighting systems, power supply, and much more. Given the cost of such equipment, and the price of their maintenance (including calibration flights) are prohibitive. Because of the markings and lightings requirement, not all airstrip will get its approach. And mountain strips requiring good climb gradients are not good candidates for procedures to be flown in IMC.

Nevertheless, WAAS approaches will revolutionize the way general aviation can take profit from IFR. Oh. I obviously ment that WAAS approches DO revolutionize it. I got the idea of this post when I read an information on www.avweb.com, relaying an information from FAA: there are more WAAS than ILS procedures published in the USA.

The plastic revolution is on its way, and nothing seems to stop it ! If you have any personal feed-back about WAAS approaches, I’d really like to read more from you.