269. USS Forrestal disaster
With the war in Southeast Asia providing experience for all phases of naval operations, several carriers which normally belong to the Atlantic Fleet were occasionally routed to WESTPAC duty, and thus it was that on June 6, 1967, Forrestal left Norfolk, Virginia, for what was to be her first combat deployment.
Carrying Air Wing 17, Forrestal was the first U.S. carrier to be built from the keel up with an angled deck. She carried East Coast squadrons, two F-4B squadrons squadrons; VFs 11 and 74; VAs 106 and 46, flying A-4Es; RVAH-11, with RA-5C Vigilantes, for which the big carrier had undergone major modification for the IOIC reconnaissance intelligence system; the KA-3Bs of VAH-10; and VAW-123, flying E-2As.
Forrestal arrived on Yankee Station on July 25 and immediately began combat operations, her aircraft flying 150 sorties during the next 4 days, without the loss of a single aircraft. At 10:52 A.M. on July 29, the second launch was being readied when a Zuni rocket accidentally fired from an F-4 Phantom parked on the starboard side of the flight deck aft of the island.
The missile streaked across the deck into a 400 gallon belly fuel tank on a parked A-4D Skyhawk. The ruptured tank spew highly flammable JP-5 fuel onto the deck which ignited spreading flames over the flight deck under other fully loaded aircraft ready for launch. The ensuing fire caused ordinance to explode and other rockets to ignite.
Spread by the wind, the flames engulfed the aft end of the stricken ship turning the flight deck into a blazing inferno. Berthing spaces immediately below the flight deck became death traps for fifty men, while other crewmen were blown overboard by the explosion.
Nearby ships hastened to the Forrestal’s aid. The Oriskany, herself a victim of a tragic fire in October 1966, stood by to offer fire-fighting and medical aid to the larger carrier. Nearby escort vessels sprayed water on the burning Forrestal and within an hour the fire on the flight deck was under control. But secondary fires below deck took another 12 hours to contain. The damage and loss of life was catastrophic.
The four-and-a-half-acre flight deck was littered with pieces of aircraft, as men struggled to clear away bombs and ammunition, throwing the ordnance over the side. One young 130-pound lieutenant found the strength to heave a 250-pound bomb overboard.
The Zuni rocket that was accidentally fired from an F-4 Phantom and started the fire is believed to have been triggered by a combination of the powerful fields at deck level from the ship’s radar and an incorrectly fitted shielded cable connector.
270. Government admits radio towers, units were too close
Eastern Creek has emerged as a possible site for Sydney’s five commercial AM radio transmitters as the NSW Government admitted yesterday it approved residential development too close to the Homebush Bay towers. The Opposition has said the 1998 decision to allow Payce Constructions to build a 1200-unit residential development within 200 metres of the tower used by 2SM and 2UE was “a first-class bungle”. But the Minister for Planning, Andrew Refshauge, said his department had acted with the best evidence before it and that no one had raised the issue of electromagnetic radiation from the towers when the masterplan was advertised in 1998. “There was no information to suggest radio broadcasts would cause any problem despite the fact the proposal was advertised widely. There was no submission made that would suggest that there was any problem.”
The Herald reported yesterday that the Australian Communications Authority had warned PlanningNSW 14 months ago that there were concerns about electromagnetic radiation from the tower, which could cause serious interference with electrical and electronic equipment. The authority also raised potential health risks associated with exposure to high-powered electromagnetic radiation. Waterside, being built in Bennelong Road, is so close to the tower used by 2UE and 2SM that it is within the “drop zone” – the area usually kept clear in case a tower falls. This occurred recently in Brisbane, when DMG’s tower was sabotaged and toppled, putting the station off air for several days.
The Opposition spokesman on planning, Andrew Humpherson, yesterday accused the Government of trying to cover up the debacle which he said had exposed taxpayers to substantial costs and claims for compensation, not just from the radio stations, but also from the developer and people who had bought the units. “We need answers. Just what was the Government aware of in 1998?” Mr Humpherson said. Dr Refshauge’s office said yesterday that there had been no submission from the broadcasters when the 1998 plan for residential development was exhibited. But the chief executive of Commercial Radio Australia, Joan Warner, said the industry had commented on the plan.
PlanningNSW, the Sydney Olympic Park Authority, broadcasters and the Australian Communications Authority are studying Eastern Creek as a relocation option.
(By Anne Davies, Urban Affairs Editor, Sydney Morning Herald, February 18 2003, http://www.smh.com.au/articles/2003/02/16/1045330466812.html, sent in by Chris Zombolas of EMC Technologies Pty Ltd., http://www.emctech.com.au.)
271. New type of light bulb claimed to interfere with satellite communications
A Maryland company will soon be manufacturing energy-saving light bulbs that almost never wear out. But a host of satellite radio broadcasters are crying interference.
According to a recent article in the Wall Street Journal, Fusion Lighting, Inc., of Rockville, MD, the manufacturer of the microwave powered bulbs, is drawing fire from Sirius Satellite Radio, Inc. and XM Satellite Radio Holdings, Inc. because the bulbs emit radio waves that directly interfere with satellite radio broadcasts. The year-long battle has seen the combatants engage in debate before the Federal Communications Commission (FCC), a private testing laboratory in Columbia, MD, and, in the near future, it appears, in courtrooms in Texas and Maryland.
Fusion began manufacturing specialty light bulbs in the 1970s, when its microwave powered ultraviolet bulbs were used in ink drying equipment in specialty industrial applications. The bulbs operated in frequency bands reserved for industrial, scientific and medical equipment.
When the company sold the ultraviolet business in 1994, Fusion’s investors looked for broader applications for the light bulb technology, and hit on the idea of marketing the microwave bulb’s energy efficiency and long life for broader commercial applications. Fusion says that it’s now about a year away from commercial sales of the bulbs for use in lighting applications as diverse as gas stations and airport runways.
Trouble is that the lights make real the prospect of highways being lit up at night by hundreds of microwave bulbs that could, claim some, silence the satellite broadcasts. Understandably, the satellite broadcasters aren’t standing for it, each having paid the government more than $80 million dollars for the right to broadcast on the contested frequencies.
Last year, the FCC attempted to broker a compromise between the parties, with Fusion eventually agreeing to reduce emissions from its bulbs by 95% by putting a metal casing around the microwave generator, using a metal reflector and coating the glass over the light. Not good enough, said the satellite broadcasters, who insisted on an emissions reduction of 99.9%. The FCC says that it’s still months away from reaching a decision on the matter.
Meanwhile, Sirius has brought suit against Fusion, charging that Fusion executives “charged Sirius with securities fraud and dishonesty” in that company’s efforts to raise additional capital. In its prospectus, Sirius mentions that “new devices may interfere with our service,” but makes no mention of light bulbs. The CEO of Fusion reportedly raised the issue of Sirius’ limited disclosure with a friend at Lehman Brothers Holdings, which was offering the Sirius shares, and the concern was eventually escalated to the underwriters handling the offering. Fusion has filed a countersuit against Sirius alleging defamation. (From “Bulb Manufacturer Lights Up Spectrum Wars”, News Breaks. Conformity, Vol. 6 No. 10, October 2001.)
272. Power Line Communication can interfere with radio astronomy
Power line communication (PLC) system which extends the available frequency bandwidth up to 30 MHz has been proposed in Japan. The electromagnetic interference problems on PLC had been investigated by the PLC study group organized by the Ministry of Public Management Home Affairs, Post and Telecommunications (MPHPT). The study group held collaborated field experiments of the PLC facility and we measured interferences caused by the PLC facility in the HF and UHF bands in order to evaluate the influences of the expansion of PLC bandwidth on radio astronomical observations.
In the field experiment, two sets of PLC modems (SS and OFDM) were tested as an access system. During the PLC modems were on, the HF spectra observed showed strong increase of the noise-floor level, and it was found that the PLC noise exceeded the level of galactic noise by more than 30 dB. In UHF band, spurious emission around 327 MHz was identified. In both HF and UHF band, the interferences exceeded the limit of harmful interference level for radio astronomical observation which is given in Recommendation ITU-R TA769-1. Safety distances where the Recommendation was satisfied are estimated to be 219 km and 12 km at 9.2 MHz and 327 MHz, respectively. PLC seems to be a harmful interference source for the radio astronomical observation in both HF and UHF bands.
(From: “Interference measurements in HF and UHF bands caused by extension of power line communication bandwidth for astronomical purpose.”)
273. Interference with early ABS and Airbag systems
Early ABS systems on both aircraft and automobiles were susceptible to EMI. Accidents occurred when the brakes functioned improperly because EMI disrupted the ABS control system. For aircraft, the initial solution was to provide a manual switch to lock out the ABS function when it was inoperable due to EMI and to use the normal braking system. Later, the solution was to qualify the ABS system prior to flight, based in the expected electromagnetic environment they would be exposed to.
For automobile systems, the solution was to ensure, if EMI occurs, that the ABS system degrade gracefully to normal braking – essentially an automatic version of the aircraft manual switch. Eventually, automobile ABS was qualified by EMI testing before procurement.
During the early years of ABS, a particular make of automobile equipped with ABS had severe braking problems along a certain stretch of the German Autobahn. The brakes were affected by a nearby radio transmitter as drivers applied them on a curved section of highway. The near-term solution was to erect a mesh screen along the highway to attenuate the EMI.
Mobile phones and passing taxi radios have been known to interfere with Anti-skid Braking Systems (ABS) and airbags, causing drivers to lose control of the car.
(The above examples include items 2.3.1.16 and 2.3.1.17 from NASA Reference Publication 1374 (RP-1374), “Electronic Systems Failures and Anomalies Attributed to Electromagnetic Interference”, which can be downloaded from: http://trs.nis.nasa.gov/archive/00000296/01/rp1374.pdf. They also include examples taken from “Study to predict the electromagnetic interference for a typical house in 2010” by Anita Woogara, Bristol University, & Smith Group, 17 September 1999 – this and many other interesting documents may be found by hunting around the (legacy) Radiocommunication Agency’s website hosted on Ofcom’s site at: http://www.ofcom.org.uk/static/archive/ra/rahome.htm.)
274. RSGB advice on identifying and locating sources of interference
The RSGB EMC Committee receives many enquiries from members about interference to reception of amateur radio signals. Accordingly, the RSGB (Radio Society of Great Britain) has produced a leaflet that gives advice about identifying and locating sources of Radio Frequency Interference (RFI, also called electromagnetic interference or EMI). Issues covered include…
- TVs, set-top boxes, Cable TV
- Switch-mode power supplies (e.g. ‘lump in a cord’ or ‘plug-top’ devices)
- Lighting
- Electric motors
- Thermostats
- Computers
- Intruder alarm systems
- Telephones and fax machines
(Taken from the Radiocommunication Agency’s useful “EMC Awareness” site at http://www.ofcom.org.uk/static/archive/ra/topics/research/RAwebPages/Radiocomms/index.htm, from its “Interference” section on: “Household Appliances and Electronic Equipment”.
(Note that since the RA was subsumed into OFCOM, http://www.ofcom.org.uk, in December 2003, all the old RA webpages are now running in the ‘legacy’ section OFCOM’s website. The RA’s site, of course, contains a great deal of valuable research that they had done into EMC, and this is also on OFCOM’s legacy site as part of the original RA website. How long this valuable resource will be maintained by OFCOM is unknown. It is also not known if OFCOM are going to continue the RA’s valuable research on EMC – more important, in these days of increasing spectrum use and more novel sources of interference, than ever before. If any OFCOM representatives would like to comment on these issues, we will be pleased to print their letters.)
275. Spacecraft engine disabled by voltage spikes
Europe’s Smart-1 spacecraft, which is en route to the moon, has an engine problem that could leave the vehicle stranded in space. Engineers at the European Space Agency are hard at work on software they hope will rescue the probe, and plan to transmit it to the spacecraft next week. Smart-1 is powered by an ion thruster, which produces thrust in one direction by accelerating xenon ions in an electric field in the other direction. Although this creates only about the same thrust as the weight of a postcard, the engine works continuously, gradually increasing the size of the spacecraft’s elliptical orbit until it is captured by the moon’s gravitational field, a process that takes 15 months.
Soon after the spacecraft was launched, the engine started switching off repeatedly. The spacecraft’s circuitry is sensitive to high-energy protons from the sun, which generate rogue voltage spikes. Engineers routinely build capacitors into circuits to mop up any voltage induced in this way. But after launch, the team found to its dismay that the mopping up feature had been omitted from some key circuits. Each time a high-energy proton hits a particular optical sensor, it generates a spike that causes the on-board computer to switch off the engine, called a “flameout”.
(Taken from the “This Week” section, New Scientist, 31 January 2004, page 14.)
276. 25,000 complaints of telephone interference in 1994
In 1994 the Federal Communications Commission (FCC) in the U.S.A. was receiving about 25,000 complaints per year from people unable to use their telephones because of interference from nearby radio stations. It is believed that this number represents only a tiny fraction of the actual instances of this type of interference.
The FCC’s Field Operations Bureau (FOB) conducted a study, which found that although most residential telephones are susceptible to receiving interference, manufacturers can design telephones to be interference-free.
The transmitting stations most likely to be involved in interference complaints are citizens band (CB), broadcast, and amateurs. Transmitted power was not a significant factor: one-third of the transmitters used under ten watts. The study also found that filters cannot be relied upon to eliminate telephone interference. In two out of three cases in which they were tried during the study, they did not work.
(Taken from: “Interference Free Telephones”, FCC (Federal Communications Commission, Washington D.C., U.S.A., News media information 202/632-5050, May 4, 1994, download from: http://www.fcc.gov/Bureaus/Common_Carrier/News_Releases/1994/nrcc4019.txt.)
277. CAA tests reinforce the decision to restrict use of cellphones in aircraft
In October 2002, a set of avionic equipment was tested under controlled conditions in a test chamber for susceptibility to cellphone interference. General aviation avionic equipment, representative of earlier analogue and digital technologies, was used. The equipment, comprising a VHF communication transceiver, a VOR/ILS navigation receiver and associated indicators, together with a gyro-stabilised remote reading compass system, was assembled to create an integrated system.
The tests covered the cellphone transmission frequencies of 412MHz (TETRA), 940MHz (GSM900) and 1719MHz (GSM1800), including simultaneous exposure to 940 and 1719MHz. The applied interference field strengths were up to 50 volts/metre for a single frequency, and 35 volts/metre for dual frequencies.
The following anomalies were seen at interference levels above 30 volts/metre, a level that can be produced by a cellphone operating at maximum power and located 30cms from the victim equipment or its wiring harness.
- Compass froze or overshot actual magnetic bearing.
- Instability of indicators.
- Digital VOR navigation bearing display errors up to 5 degrees.
- VOR navigation To/From indicator reversal.
- VOR and ILS course deviation indicator errors with and without a failure flag.
- Reduced sensitivity of the ILS Localiser receiver.
- Background noise on audio outputs.
Most anomalies were observed at 1719MHz.
The results of the tests endorse current policy that restricts the use of cellphones in aircraft.
The CAA will remind operators about the specific risk from cellphone usage on the flight deck, and recommend that confirmation be obtained from passengers at check-in that cellphones in their luggage have been switched off.
(Taken from the Radiocommunication Agency’s “EMC Awareness” website, now at: http://www.ofcom.org.uk/static/archive/ra/topics/research/RAwebPages/Radiocomms/index.htm.)
