controlled flight into terrain

[tocafundo]

Da pauroso volevo chiarimenti in generale non per uno specifico incidente, ma per una tipologia (anche se so che ogni incidente/invonveniente è storia a se stante fatto di tante concause). In particolar modo mi riferisco a quegli episodi avvenuti durante l'avvicinamento all'aeroporto, con collisione contro colline, montagne ecc...Volevo capire perchè, nonostante le strumentazioni di volo che permettano di volare praticamente senza visibilità (penso) possano succedere ancora tali incidenti...

Cito questo lungo e mi sa datato articolo, però con alcune parti che fanno capire la mia domanda...grazie a tutti
http://www.ulm.it/hangar/mix/betland/Ca ... lo%201.htm

[JT8D]

La definizione corrente di cfit è:

CFIT: An event where a mechanically normally functioning airplane is inadvertently flown into ground, water, or an obstacle.

Nota il termine "inadvertently", ciòè l'impatto è inatteso e imprevisto, a causa dell'inconsapevolezza dei piloti riguardo alla propria posizione rispetto ad acqua, terreno od ostacoli.

I casi di Cfit avvengono prevalentemente in condizioni strumentali oppure di notte anche con buona visibilità ma con erronea interpretazione della propria posizione a causa di luci o altre immagini fuorvianti che prevalgono nei riferimenti del pilota rispetto alle indicazioni strumentali corrette.

Paolo

[tocafundo]

ciao, grazie della risposta, a questa conclusione ero arrivato anche io, ma volevo entrare ( se possibile) un po più nel tecnico della possibilità di tali eventi.
Nel senso...il tutto è riconducibile esclusivamente ed un errore umano di valutazione nel caso di strumenti funzionanti?
In caso di scarsa visibilità (quindi anche di notte) non esistono strumenti che riferiscono dell'altezza rispetto al suolo o ad eventuali ostacoli (penso di si)?Può essere la "routine" di una cosa "ritenuta normale da farsi" a scatenare tali eventi? se esistono delle procedure di controllo e valutazione della posizione e ostacoli in avvicinamento?...scusa se sono "noioso" ma è come se (nel mio campo) rispondessi ad una domanda che mi chiede perchè durante le costuzioni delle case perchè gli operai cadono dai ponteggi dicendo perchè mettono male il piede...quando le cause potrebbero essere disattenzione, mancanza di formazione, ponteggio non a norma ecc...

[JT8D]

Lo human factor è di solito determinante nel verificarsi di casi di cfit.
Ci sono delle situazioni in cui i piloti compiono degli errori di valutazione. Essi sono convinti di avere tutto sotto controllo, di sapere esattamente dove si è, ma la realtà invece è diversa.
Secondo gli studi effettuati, di solito i cfit avvengono con equipaggi o molto o poco esperti, nel primo caso per routine e abitudine, nel secondo per inesperienza.
Per evitare il ripetersi di questi eventi, dopo avere trovato l'errore e si cerca rimediare creando delle procedure diverse e più efficienti.

Tieni comunque presnte che un cfit, come tutti gli incidenti, è sempre dovuto ad una catena complessa di eventi che unendosi provocano l'evento.
Ti riporto qui un interessante testo, tratto da un articolo su airmanshiponline, sui fattori dello cfit:

CFIT factors

Flight Crew Complacency

Complacency can be defined as self-satisfaction, smugness, or contentment. You can understand why, after years in the same flight deck, on the same route structure to the same destinations, a flight crew could become content, smug, or selfsatisfied. Add to this equation a modern flightdeck with a well -functioning autopilot, and you have the formula for complacency.
Here is an example of flight crew complacency. The flight crew is flying an arrival. They get a nonstandard clearance to descend to a lower altitude, in an unfamiliar sector. Suddenly, the GPWS warning sounds: "Pull up! Pull up!" The flight crew is not sure what to do, because they have never experienced this before. They may hesitate to pull up, or they may ignore the warning-with disastrous results.
In this scenario, the GPWS warning may not have registered with the flight crew. They have flown into this airport hundreds of times, but because of complacency, their brains may very well have disregarded aural and visual cockpit warnings.
At the other extreme, flight crews may also be exposed to continued false GPWS warnings because of a particular terrain feature and a GPWS database that has not been customized for the arrival. The flight crew becomes conditioned to this situation since they have flown the approach many times. This can also lull the flight crew into complacency, and they may fail to react to an actual threat.
Note: The newer versions of GPWS can be programmed by the manufacturer for specific airfield approach requirements, so that these nuisance warnings are eliminated.
• Know that familiarity can lad to complacency.
• Do not assume that this flight will be like the last flight.
• Adhere to procedures.


Procedural Factors Associated With CFIT

Many studies show that operators with established, well thought out and implemented standard operating procedures (SOP) consistently have safer operations. It is through these procedures that the airline sets the standards that all flight crews are required to follow. CFIT accidents have occurred when flight crews did not know the procedures, did not understand them, and did not comply with them or when there were no procedures established.
More than one CFIT accident has occurred when the flight crew delayed its response to a GPWS warning during IMC.
If an SOP had addressed this situation and provided the flight crew with specific guidance, maybe an accident could have been avoided. In the absence of SOPs, flight crews will establish their own to fill the void in order to complete the flight. Some crews think the weather is never too bad to initiate an approach! It is the responsibility of management to develop the comprehensive procedures, train the flight crews, and quality control the results. It is the responsibility of the flight crew to learn and follow the procedures and provide feedback to management when the procedures are incorrect, inappropriate, or incomplete.
- Do not invent your own procedures.
- Management must provide satisfactory SOPs and effective training to the flight crew.
- Comply with these procedures.


Descent, Approach, and Landing Factors

CFIT accidents have occurred during departures, but the overwhelming majority of accidents occur during the descent, approach, and landing phases of the flight.
CFIT accidents make up the majority of these accidents.
An enlightening analysis of 40 CFIT accidents and incidents was accomplished for a 5-year period, 1986 to 1990. The airplanes' lateral position in relation to the airport runway and the vertical profile were plotted. (Figures 1 and 2). One of the interesting things is that almost all the position plots in Figure 1 are on the runway centerline inside of 10 mi from the intended airport. The vertical profiles shown in Figure 2 are also significant. The flight paths are relatively constant 3-deg paths-right into the ground! Most of the impacts are between the outer marker and the runway.
The geographical Iocations of CFIT accidents during the 1970s show a different pattern than those in the late 1980s and 1990s. During the 5 year period from 1972 through 1977, there were 75 CFIT accidents or incidents. Twenty-five of these accidents/incidents were greater than 8 nm from the runway. The preponderance of the remaining accidents/incidents were inside the middle marker. However, for the period 1986 to 1990, the distribulion of accidents/incidents was relatively even. This difference may be the result of improvements made in runway approach aids that took place during this time period. Additional ILS were installed, as well as runway approach lighting systems. Continued capital investment in runway precision approach and lighting systems needs to be made worldwide.
- Know what approach and runway aids are available before initiating an approach.
- Use all available approach and runway aids.
- Use every aid to assist you in knowing your position and the required altitudes at that position.
Most CFIT accidents occur during non-precision approaches, specifically VOR and VOR/DME approaches. Inaccurate or poorly designed approach procedures coupled with a variety of depictions can be part of the problem. Figure 3 is an example of an approach procedure produced by different sources. There are documented cases that the minimum terrain clearances on some published approach charts have contributed to both accidents and incidents. For more than a decade, a worldwide effort has been under way to both raise and standardize the descent gradient of non-precision approaches. There are gradients as little as 0.7 deg in some VOR approach procedures. ASRS report #254276 illustrates the hazard of shallow approaches coupled with other confusion associated with the procedure design. In addition to the shallow approach gradients, many approaches use multiple altitude step-down procedures. This increases flight crew workload and the potential for making errors.
- Study the approach procedure(s) before departure.
- Identify unique gradient and step-down requirements.
- Review approach procedures during the approach briefing.
- Use autoflight systems. when available.
There is more than one standard for approach procedures in the world.
The U.S. standard is Terminal Instrument Procedures (TERPS).
The ICAO standard is Procedures for Air Navigation Services-Aircraft Operations (PANS-OPS), and the Russian Federation uses still another.
Flight crews, therefore, may be exposed to different standards and different margins of terrain clearances.
-Study anticipated approach procedures before departure.
-Know that there are different approach design standards.
Different approach procedure charting requirements and printing can also make it more difficult for flight crews to safely fly an approach. High elevation obstacles and terrain surrounding airports have been annotated on charts for years, but the actual terrain has not been depicted. Slowly, the publishing and printing organizations for aeronautical and approach charts have begun to use color and depict terrain or minimum safe altitude contours. Recently, some of the larger international operators have started printing their own customized charts that include these features. This greatly helps the flight crews to recognize the proximity of high terrain to the approach courses. Hopefully, this will result in fewer accidents.
Unstable approaches contribute to many CFIT accidents or incidents. Unstable approaches increase the possibility of diverting a flight crew's attention to regaining better control of the airplane and away from the approach procedure. A stabilized approach is defined by many operators as a constant rate of descent along an approximate 3deg flight path with stable airspeed, power setting, and trim, with the airplane configured for landing.
- Fly stabilized approaches.
- Execute a missed approach if not stabilized by 500 ft above ground level or the altitude specified by your airline.
In some modern glass-cockpit aircraft, the flight guidance system has the capability to display flight path vector/flight path angle. Use of this mode enables a stabilized approach to be flown at the required slope during a non-precision approach, with automatic correction for the effects of wind.
Flight management systems also have the capability to provide a computed profile for a non-precision approach. Required conditions for the use of lateral and vertical navigation functions for this purpose are that the approach profile is included in the database, that it is verified in accordance with obstacle clearance criteria, and that the FMS accuracy is confirmed to be high.
The use of these techniques, in conjunction with the autoflight system, reduces crew workload and should ensure a higher level of safety. Procedures specific to the airline type are given in the applicable Flight Crew Operating Manual. Crews should be adequately trained, either in the simulator or in flight, to use the procedures associated with these features.
- If a non-precision approach is necessary, use the recommended flight guidance system function to fly a stabilized profile at the required angle whenever possible.
- Continuously monitor position and track by reference to the basic approach aid(s).

Paolo

[tocafundo]

grazie mille!molto interessante