In the July issue (page 28) Kathleen Kocks did a good job summarizing the spectrum tug of war that goes on today. But I thought it would be educational for people to know that for well over 15 years the National Telecommunications and Information Administration (NTIA) has urged the U.S. Federal Communications Commission (FCC) to enact some receiver standards--any standards.
We suggested Mil-Std-461. We suggested harmonized European standards. We suggested some industry standards. All to no avail.
Now, suddenly, we hear of the idea of interference temperatures. That has been a part of the government assignment-nominating program within (the Department of Defense-Joint Spectrum Center's) Spectrum XXI for about nine years already. But it's nice to hope that all receivers of the future may have to be designed to some measurable standard, as government receivers have had to be designed for decades.
Richard (Randy) Lancaster
Office of Spectrum Management
National Telecommunications and Information Administration
Regarding the article, "ADS-B's Global Advance," by Brian Evans (August 2004, page 24), specifically, automatic dependent surveillance-broadcast can't replace the traffic alert collision avoidance system (TCAS). This is aside from the fact that all RF systems are subject to environmental conditions, along with many other parameters.
The claim that TCAS is a short-range system of 30 nautical miles (nm) is inaccurate. TCAS is capable of monitoring Mode S extended squitter-equipped aircraft up to 200 nm away. This depends on the installation; you need a control head with the proper ARINC 429 bus and a display capable of presenting such a range. But it is in operation today.
Roger D. Block
IP Licensing Engineering Lead
I always enjoy reading the Editor's Note in Avionics Magazine every month. In the June 2004 issue (page 6) you wrote about some of the proposed missile defense systems that are under consideration for airliners and how they would work.
I have been bothered by the proposal to use a laser on an airliner to "blind" an incoming infrared-guided, surface-to-air missile. I believe the system may do more harm than good.
If the laser "blinds" the missile guidance system, the missile will continue in a "ballistic" mode and explode upon impact or within close proximity of the aircraft. If left alone, the missile will most likely score a direct hit on an engine.
It seems that the aircraft would have a better chance of survival with the hit on the engine. It would concentrate most of the missile's explosive power in a large structural mass that would better absorb the power and localize the damage to a redundant component of the aircraft.
A "close miss," on the other hand, could cause the missile to impact the wing, tail or the fuselage, which would cause a much greater problem with control issues.
Electronics Engineer Staff
Modular Mission Computers,
Weapons and Stores Management
Lockheed Martin Aeronautics Co.
Fort Worth, Texas
Regarding the October Editor's Note (page 6), titled "Cell Phones, Social Issues," thank you for being so straight to the point. Just seeing people using phones as they drive is infuriating, and it is intolerable and unacceptable to have to sit next to someone with his ear glued to the thing. Another reason for general aviation.
I have no qualm with someone needing to use the phone. But the social status symbol in using one is for the birds. And I think a majority of use is just that--the same as bottled water, ghetto-buster boom boxes, etc.
Regarding the safety of flight--"...this network will take control of it. It will limit phone emissions to levels considered safe..."--we all know that anything made by man can and will fail. Consider failure due to RF interference on a loaded "mega-passenger" airliner during an ILS to Category III minima.
I have a notice to turn cell phones off when entering my office. I perform flight physical examinations.
Aviation Safety Counselor