Radio Altimeter effectiveness and CFIT How can technology be used to effectively diminish CFIT and ALA incidents?

Air travel is one of the safest means of traveling from one location to another in the world. Without air traffic, the business world would come to a screeching halt. Although businesses can transfer mass amounts of digital communications DATA, thus eliminating much of the demand on mail and fax transmissions of just a decade ago, businesses organizations can still not transfer products, mail, personnel, and other hard goods through electronic blips on the internet. Travel still relies on airliners and cargo air-busses which fill the skies around the world and around the clock. The experts are agreed that global commercial air traffic will grow at an average 5% per year over the next 20 years. This means that traffic will double in 15 years and will practically triple by the end of the second decade of the next century. (Interavia, 1999)

The air travel industry is built on principles which have established and maintained its safety records. These principles have been the foundation of the industry. One of these principles is that of multiple redundant systems. Once an airliner is in the air, the forces of physics and gravity will control its flight path. If there is a mistake, or a failed system, no one can ask gravity and inertia to take a break while the problem is fixed. So each airplane is built with multiple control redundancies in order to prepare for any possible problem.

A second principle, which can work counter to the first, is that the pilot and crew are always in final control of the aircraft. (Luccio, 2001) If the systems malfunction, the pilot can override them to control the craft. If the conditions so warrant, the pilot can turn off individual controls in order to maintain control of the air craft. Neither pilots nor air line companies want to have an accident from a failed system, or poor weather conditions in which an automated system locked out the crew and the resulting disaster was due to a "technical malfunction."

During the past 4 decades, the aviation industry has realized that the combination of equipment and personnel needs to be actively managed. The following chart tracks the growing body of knowledge which has accumulated in the aviation industry regarding air safety.

Perceived Accident Main Causality

Focus of Airline Safety Efforts

Focus of Manufacturer's Safety Efforts

1960's

Accidents result from individual pilot error, mainly attributed to a lack of basic flying skills

Selection of appropriate psychomotor skills. Handling training oriented toward handling proficiency.

Designing more reliable aircraft.

1970's

Accidents result from individual pilot error, mainly attributed to a lark of technical proficiency.

Selection of appropriate psychomotor and cognitive skills. Intense use of (increasing fidelity) simulators.

Designing more reliable and easy to fly aircraft. Built in redundancy; fail safe and fail operational concepts. More automation assistance to flight control

1980's

Accidents result from cockpit crew errors mainly attributed to team synergy failures and to a poor management of resources available in the cockpit.

Selection of "right stuff" with proper cooperation skills. Crew resource management training

Focus on crew workload. Reducing pilot involvement in direct flight control actions (fly-by-wire stability, more and more auto flight capabilities; providing for more and more error protections (GPWS).

1990's

Every accident is a failure or organization" (Prof K.R. Andrews). Front line operator behavior is strongly (even if not totally) determined by systemic forces (selection, training, procedures, cultures, work conditions, organization structures). Human error is not a failure per se, but an intrinsic component of Cognitive processes. Accidents result from a loss of control of the crew (and the larger team) on their error management process.

Fourth -- and fifth- generation CRM training: -situation awareness augmentation, error management strategies, and facilitation of metacognition. --Company Resource Management.

Providing for situation awareness augmentation and decision aids (Navigational Display, Centralized Monitoring, ECAM procedures). More automatic protections against consequences of undetected errors: EGPWs, Closer communication with airlines: --Prevention strategies. (Adapted from Amalberti and Sarter, 2000)

For these reasons, discussions of overcoming specific safety and technical issues which are commonplace in the aviation industry must be a combined discussion of technology and human interface with the same. While capable of operating the plane in 80% of the situations, and through 80% of a flight, the technology cannot replace the need for human judgment that pilots the craft through the other 20% of a flight. Until technology advances to the creation of artificial intelligence...

While atmospheric barometers determine altitude above sea level and are affected by changing weather patterns, radio altimeters measure the aircrafts height above the ground, and can be useful in determining actual flight paths for aircraft during approach and landing events when visibility is diminished.
First-generation GPWS technology looks straight down, using the airplane's radio altimeter to provide warning of threatening terrain. Against gently rising terrain, its warning is better than nothing. But, as one pilot described its limitation, GPWS would remain silent in an airplane flying across level ground -- and straight toward a vertical cliff. Less than 5 per cent of the world's commercial aircraft fleet is not equipped with GPWS; it is these unequipped aircraft which are involved in nearly 50 per cent of CFIT accidents. (Flightsafety.org.au, online)

Literature Review

Controlled Flight into Terrain

Two specific air incidents are considered, the main objective to overcome the incidents, and evaluate a warning system built around a radio altimeter. The controlled flight into terrain (CFIT) is one of the most pressing incidents to address. Since the beginning of commercial jet transport, over 9,000 people have died worldwide because of CFIT.

Controlled Flight Into Terrain (CFIT) is responsible for more than half of all commercial aviation fatalities - making it one of the international aviation community's most pressing safety problems. (flightsafety.org.au, online)

When an air craft is landing, the physics of the plane are changing dynamically and instantaneously throughout the landing procedure. Many times, if the craft's safety is threatened, the craft is warned too late to make changes and avoid the crash. At other times, although occurring less frequently, an aircraft can wander off course during turbulent weather conditions, and fly into elevated terrain. However, this is the minority of occurrences when discussing CFIT.

For example, the following actual incident and accident summaries illustrate some typical accident scenarios:

At night in IMC, the pilot misread the NAV-DME due to fatigue. Read DME on wrong NAV radio, descended too early on back course LOC approach and penetrated prohibited airspace, after flying 7 hours and having been on duty for 10 hours. A low- altitude alert issued by the Approach Controller prevented an accident.

The pilot likely lost situational awareness and inadvertently flew the aircraft into the ice surface while in controlled flight because of the combined effects of the lack of external visual references and weak instrument flying skills.

The pilot continued flight in adverse weather conditions and probably did not have the necessary visual references to avoid hitting the steep slope of the mountain. Likely contributing to this accident was the pilot's over-reliance on GPS while attempting to maintain visual meteorological conditions

The Nov. 24, 2001, fatal crash of a Crossair regional jet underscores the need for action. It was a classic "dark and stormy night" when the Avro RJ-100 jet was approaching Zurich International airport after a one-hour flight from Berlin. Time: about 10 p.m. Weather: light snow. Visibility: two miles (3.2 km) with scattered clouds at 600 feet (183 meters) above the ground-significantly below the minimum descent altitude of 974 feet (300 meters) for the non-precision approach to Zurich's runway 28. It appears from the preliminary account of the Swiss accident investigation bureau that Lutz's RJ-100 was too low by about 1,000 feet (305 meters) a good three to four minutes before the crash. At 10:06 P.M., the radar altimeter, set to alarm at 300 feet (91 meters), sounded its warning. At this point, the airplane was too low by a good 600 feet (182 meters), given that the minimum safe altitude was 974 feet.

There were scant seconds for the Crossair crew to react when trees loomed out of the darkness. Just moments before impact, Lutz called for a go-around. It was too late. A surviving passenger reported that the approach to landing was smooth, and that at first he thought the airplane had landed "hard" on the runway, not crashed into the forest. Of the 33 passengers and crew on board, 24 were killed, including pilot and copilot. (Evans, 2002)

Approach and Landing Accidents

Almost 20% of routine flights examined by researchers showed errors or other departures from standard procedures that raised the risk of an approach-and-landing accident (ALA), according to Dr. Ratan Khatwa, a senior flight-deck research engineer…