The Comments period on the FAA's ADS-B NPRM closes in a couple of hours, so hopefully you've submitted any comments. Mine are in, though I don't see them posted yet. Here's in part what I had to say:
ADS-B holds great promise as a key element of a NextGen solution. However, the current proposal could be improved upon so that it delivers the right benefits at the lowest cost. (Click below to see more)
From an engineering perspective, allowing two different ADS-B standards for aircraft below FL240 seems like a kludge, or a clumsy, inelegant solution. It appears that the goal of this is to 1) allow a lower cost system for low flying aircraft and 2) provide a FIS-B option for these aircraft. As a result, a workaround solution, ADS-R, is required to cobble together these two systems. This results in: 1) higher cost to install the ADS-R translator systems, and 2) poorer overall system performance. In particular, I’m concerned about low flying 1090ES-equipped aircraft being unable to detect UAT-equipped aircraft when one or both aircraft are not within range of a ADS-R site. With a single 1090ES standard, all aircraft would always be able to identify nearby aircraft regardless of the location of ground equipment.
Please examine what it would take to develop a 1090ES based solution for all aircraft. Given the recent development of excellent, near real-time, weather solutions such as satellite based XM Weather, I’m not convinced that the demand for FIS-B capability is real. While FIS-B was a valuable benefit when ADS-B was first developed, recent technology developments have marginalized its value. Hence, an illusory demand for FIS-B should no longer be used as a justification for using a separate UAT standard.
If a two standard system is implemented, please consider changing the FL240 requirement to FL250. A significant number of aircraft are certified to fly up to FL250. It would be absurd for them to be arbitrarily limited to FL240 if they are UAT equipped.
Mode C transponders are not required above 10,000 feet if one remains within 2,500 feet of the ground, however the ADS-B proposal does not include that exclusion. Please add this exclusion to the proposal. Doing so will enhance safety, since non-ADS-B equipped aircraft will not be required to fly precariously close to mountains, just to remain in compliance with this rulemaking.
The costs costs and benefits of this NPRM are asymmetrical. The FAA may save money by eliminating some radar installations, but that’s offset by the requirement for pilots to spend thousands of dollars to equip each aircraft with ADS-B. On the benefits side, the FAA may succeed in squeezing more aircraft into the en route structure, but pilots who opt for the minimum required ADS-B Out requirement derive little benefit, except for continued access to the NAS. The FAA should consider putting economic incentives in place for pilots to equip with ADS-B In. That way, pilots will get an important benefit (the ability to view nearby traffic) at little or no incremental cost above the mandated ADS-B Out.
Some of the potential savings to the FAA won’t be realized due to the need to retain a substantial number of secondary installations. Please consider alternative backup systems, such as a second ADS-B system based upon Loran or alternate sensors. This would allow: 1) the FAA to eliminate all secondary radar, 2) pilots to eliminate mode C transponders, and 3) an independent ADS-B system should WAAS or other sensors fail.
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