Airborne Silent Movies
In your "Outlook" coverage in the January 2001 issue (page 30), you say in-flight movies go back more than 35 years. In fact, they go back much more than 35 years.
German airlines were showing movies in airplanes by April 1925. The movies were silent, and perhaps this was just as well in view of the noisy engines.
R.H. Atkinson
Columbia Crossroads, Penn.
A Suspicious Argument
I notice in your Safety in Avionics column (November 2000, page 55) that Dr. Peter Ladkin asserts in dispassionate language that the maximum possible energy that could have been radiated by all the potential sources in the vicinity of the TWA 800 crash would have been insufficient to ignite fuel vapor. We know that these sources do not continuously emit their maximum output; the likely emission strength for any given moment is at least 20,000 times less than the minimum level that might possibly pose a fuel vapor ignition danger.
Dr. Elaine Scarry seems to write in a much different tone. Hers is a cleverly constructed argument, advocating her EMI (electromagnetic interference) theory. It is not a scientific argument, but is to persuade readers that EMI may well be the root cause of crashes.
Aircraft transmit and receive lots of radio signals, and frequency interference might cause problems with these signals–most likely lost messages. Less likely would be spoofed RF systems in which interference might be mistaken for meaningful messages, resulting in navigation or flight operation errors. Even less likely, but not impossible, EMI might affect the electrons within non-RF aircraft systems.
Scarry cites a case of military aircraft in Libya. Such aircraft communicate with each other and with command-and-control systems using very sophisticated RF messaging. I believe the Libya incident is a case of "bugs" in these complex systems that resulted in messages intended for one aircraft being received and thought to be legitimate by another.
Scarry relates this incident to Swissair 111, but fails to point out the vast differences in scenarios. She also cites numerous examples of EMI "incidents" and asserts that these support her view regarding TWA 800. But she fails to point out that none of these incidents involved fuel vapor explosions or wire arcing. Rather, they are examples low-energy RF interference.
Scarry is smart and an adept advocate. But I find her motive to be curious. Does she believe that there is a conspiracy afoot to cover up a grave danger? I’m concerned that her approach may have the effect of blurring public focus on issues that, unlike EMI, are supported by hard evidence.
Mark Fetherolf
Plastic Shields
I enjoyed reading your article, "" (August 2000, page 47), especially with plastic alternatives. Could you explain the performance of plastic or composite connectors in terms of providing adequate shielding for HIRF/EMI (high-intensity radiated field/electromagnetic interference) or indirect lightning and providing continuity for direct lightning? Can the equivalent current capacity of lightning be provided by the metal surfaces of a plastic composite connector?
Bambang
Electrical Engineer
Response:
Achieving identical electrical performance with composite connector shells is difficult. Even if performance starts similar, surface wear and damage soon make the composite connector less effective as a shield path, and the bulk conductivity is far worse–an important issue for lightning-related protection. Generally, only a few extreme weight or corrosion situations make the composite housing attractive. If good shielding and ground path conductivity, as well as light weight, are issues, a metal shell selection from MIL-C-38999 is likely to be the best. –Walter Shawlee 2
C-130s in Australia
I refer to your July 2000 cover story article titled "Not Your Father’s C-130" (page 20). You make no mention of Australia as an operator of the C-130. For your information, the Royal Australian Air Force (RAAF) was the first non-U.S. operator of the Hercules back in 1958, when 12 C-130As were purchased. Twelve C-130Es were purchased in 1966-67; the As were replaced with 12 C-130H models in 1978-79, and the C-130Es were replaced with 12 stretched C-130Js in 2000. In fact, along with the UK Royal Air Force, the RAAF was a lead customer for the C-130J.
In addition, the aircraft featured on the cover of the magazine is an RAAF aircraft. You may be interested to know that the RAAF has never had a major accident with the Hercules aircraft, and they have been flown more than 645,000 hours.
Air Commodore G.I. Lumsden AM (Rtd.)
Castle Hill, New South Wales, Australia
Response:
Sometimes the obvious is the easiest to overlook. The cover photo was, in fact, an RAAF C-130J flying over Australia’s Blue Mountains, which we did note on the table of contents page. However, we should have added Australia to the list of operators on page 24. Thanks for your letter and the historical information. –Editor