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The Good and the Bad and the Ugly


The advent of the microchip has lead to high-speed integrated circuits that lead to compact and more powerful avionics, compared with those found in earlier jet aircraft.

When it became clear that it is possible to shoot down an aircraft with a surface-to-air missile (SAM), the new tactic was to fly closer to the ground, and systems were developed to make it possible to do so effectively. In the development of these systems, electronics played a major role. This new tactic in turn led to the development of a technology that made it possible for higher flying aircraft to discern an enemy aircraft from its background, being the ground below. And that was when stealth entered the equation.

But this article is not about stealth. That is another story. This article is about the vulnerability of electronics, and the vulnerability due to electronics.

The Black Hawk disasters, and more than ten years thereafter

In an article in the Chicago Tribune of 11 November 1987, it was reported that the U.S Army was alarmed by test results showing that radio waves can shut down the vital hydraulic system of its Black Hawk helicopter, and that the Army would therefore shield the system’s electronic controls from such interference. According to the test results, radio waves triggered a complete hydraulic failure on a UH-60 Black Hawk by generating a false electrical command in the system. The article goes on to report that the Army’s decision came after a series of crashes in which the helicopters nose-dived into the ground. The report furthermore states that 22 servicemen have been killed in five Black Hawk crashes during the period 1982 to 1987.

That was in 1987. More than 10 years later the situation does not seem to have improved, as will appear from what an eminent computer scientist has to say.

In a paper titled, “Computer Security in Aviation: Vulnerabilities, Threats, and Risks”, delivered by Dr. Peter G. Neumann during January 1997 at the International Conference on Aviation Safety and Security in the 21st Century, that was held at George Washington University, he dealt, inter alia,  with computer-related aircraft accidents. Neumann is a Principal Scientist at the Computer Science Laboratory of SRI International in Menlo Park, California, and he holds two doctorates from Harvard and the Technische Hochschule, Darmstadt, Germany. He stated that “The list of computer-related aircraft accidents is not encouraging. Undeserved faith in the infallibility of computer systems and the people who use them played a role in the Korean Airlines 007 shootdown, the Vincennes' Aegis shootdown of the Iranian Airbus, the F-15 shootdowns of two U.S. BlackHawks over Iraq, the Air New Zealand crash into Mt Erebus, the Lauda Air thrust-reverser problem, NW flight 255, the British Midlands 737 crash, several Airbus A320 crashes, the American Airlines Cali crash, the Ilyushin Il-114 crash -- to name just a few.”

The laptop computer Electromagnetic Interference hazard

Although it appears that the effect of laptop computers with cable attached devices on aircraft electronics (which includes aircraft onboard computers), are still not fully understood, they are indeed a source of radiation that appears to create a very real risk. Electromagnetic Interference (EMI) has reportedly been considered as a possible explanation for the fact that a F-16 of the U.S. Air Force accidentally dropped a bomb on rural West Georgia on 4 May 1989 and, as previously mentioned, has also been found to be the cause of hydraulic failures of several UH-60 Black Hawk helicopters.

Uncovering the real cause of mishaps

It is conceivable that aviation glitches may often be attributed to human error on the part of aircrew or air traffic controllers when, in actual fact, the cause of the glitch may emanate from a particular system that was utilized during the aviation operation.

It is therefore imperative that, after an aviation accident, a thorough investigation be done on all factors that may affect electronic systems that are used in flight functions such a flight control, navigation, communication, and data storage/retrieval.  

Malicious intent: Terrorism and Sabotage

Neumann deals with the possibility of malicious action in the form of physical or logical attacks on computers, and communication and radar facilities.

He points out that the use of the Internet could create further risks and that the increasingly widespread availability of system-cracking software tools points to the possibility that certain types of attacks may became more frequent as the techniques became more widely known and adequate defences fail to materialize. The dangers posed why the prolific use of the Internet and the World Wide Web and the ease with which web pages of the CIA, NASA and the U.S. Air Force have been altered by intruders, is indicative of the depth of the problem. The risks become ever greater as air industry-related activities became more dependent on the Internet and computer systems.

No easy answers

It appears that there are no easy answers. Since security, safety and reliability, each considered on its own, is a very difficult problem, the combination of all three factors are even more complicated.

The spanner in the works has become a stray signal in the electronics

The advances in aviation technology have given us the moving map, the Ground Proximity Warning System (GPWS), the Beacon Collision Avoidance System (BCAS) and a number of other truly impressive electronic systems, of which the unique facilities of the MD-11 is an example.

The long-haul McDonnell-Douglas MD-11 is derived from the DC-10 and the collaborative endeavours of 1500 software engineers and pilots from thirty-seven airlines lead to the creation of an aircraft that could, when it needs to do so, carry out incredible feats of self-repair. For example; if more than one electrical fault was to occur in the aircraft, then its computers would "reconfigure" the electrical systems and instantly redistribute tasks among the aircraft’s three electrical systems, thereby affording the aircrew more time to deal appropriately with the particular contingency.

Furthermore, the fact that the formation flight of a number of C-17 Globemasters can be “managed avionically” when flying in cloud, is also impressive. By “managed avionically” I mean that by using avionics the aircraft fly in formation without human intervention.

But how safe is all this electronic wizardry? The following explanation of how an autopilot disconnects in situations of electromagnetic interference, gives some perspective regarding the question.

There are two ways in which an autopilot can disconnect. The autopilot may automatically disconnect, either because it receives a stray electrical command, which shuts it off, or because it becomes baffled by the random information it is receiving, and shuts down.


It has therefore become clear that it only takes a tray stray signal in the electronics, to put a spanner in the works, and continuous concerted efforts are therefore necessary to develop the technology that is needed to shield and protect the electronics on aircraft, spacecraft, and all other electronic facilities that are required for their safe, successful flight.