Controlling Flight Into Terrain
As a defined sauce, accidents labelled CFIT, or “controlled flight into terrain”, represent a large percentage of the fatal mishaps experiences by business aircraft. The Flight Safety Foundation reported that CFIT remained the second greatest cause of commercial aircraft fatalities in 2008. And, historically, more deaths have resulted from CFIT than any other type of accident.
Avoiding this often-inexplicable consequence requires both study and resolve, first to recognize the signs of a set-up for CFIT and then to encourage an early decision to remove the aircraft from its clutches.
The FAA’s definition of a CFIT accident reads “…an airworthy aircraft…is flown into terrain with no demonstrated prior awareness of the impending collision on the part of the crew.” Clearly, a lack of situational awareness took the place of normal caution.
By this denotation, CFIT means the crew took no action to mitigate the crash, or did so only in the final seconds of flight when the calamity became starkly obvious. The flight continued with no awareness, or a disregard of any uncertainty, until the ground met the machine. Because the aircraft was often flown into the ground at normal speed, with no attempt made to avoid impact, the results are likely to be particularly disastrous.
CFIT accidents emanate almost entirely from a loss of situational awareness. For whatever reason, the flight crew misinterpreted the aircraft’s relationship with the ground; believing or assuming the terrain clearance existed at their location. This can involve a mistake in lateral navigation, as when the aircraft’s actual location is miles from where is should be, or vertical error, as when the altitude limit is ignored or a descent is begun too early. Further confusion can occur when an electronic navigational aid is misread, mistuned or disregarded.
Disorientation, as in simply being lost, is not the same as losing situational awareness. One might well be aware of one’s location, but be cognizant of that fact, proceed accordingly and take steps to maintain or regain a safe orientation. CFIT need not occur just because you’re off track. It is most likely to become a true threat when you “don’t know what you don’t know”.
Horrible Examples
In August 1997, Korean Air Flight 801 was flown into rising terrain on the island of Guam with the GPWS sounding a “sink rate” alarm, which was disregarded because there was no excessive sink rate. However, what the “prox box” was telling the Boeing 747’s crew was that the distance to the ground was rapidly diminishing; the airplane crashed into a slope three miles from the runway, the victim of a premature descent on a non-precision approach.
An earlier crash by an American Airliners Boeing 757 at Cali, Colombia in 1995, illustrated the ease with which unfamiliar circumstances can cause a loss of situational awareness. In his haste to land, the captain selected the wrong VOR station, and then misprogrammed the FMS, all while descending to an inappropriate altitude for their location. Disoriented and confused, the crew flew into a ridge after receiving a last-second warning from their early-generation GPWS.
Banishing CFIT
Through Technology
Over the years, our tools to prevent CFIT have grown ever more impressive, yet pilots still manage to find ways to crash. When GPWS (ground proximity warning systems) were developed, and improved in various iterations, it was thought that CFIT was gone for good because the “prox box” could deliver an aural pull-up warning of impending ground contact.
However, the original GPWS equipment of 40 years ago was never designed to take the place of situational awareness, but merely to be a last-ditch barrier to flying into the ground. The first ground proximity warning units relied on downward-looking radar altimetry to detect rising terrain, later to be supplemented by an onboard terrain database to create look-ahead capability.
To successfully employ GPWS, now replaced by TAWS (terrain awareness warning system) in its latest form, pilots have to be trained to react INSTANTLY to its warning, legalities aside. Without such prioritizing, it’s tempting to succumb to a desire to troubleshoot the unexpected alert – “where are we, what’s going on?” – While the aircraft draws ever closer to the terrain. When the “pull up” command sounds, an immediate pitch up and power application must be started, leaving deliberation and debate for the moment.
With the advent of satellite navigation and more capable computing power, the development of TAWS has brought not only aural alerts, but also detailed mapping of terrain threats into the cockpit. Regulatory mandates have made TAWS standard for all but the smallest turbine-powered aircraft (six or more passenger seats), and most business-class airplanes will be equipped.
The finest weapon in our arsenal is synthetic vision for glass-cockpit displays, a presentation of the world ahead that’s derived from a database of terrain coupled with GPS-based position information. With a VMC-like picture on the PFD and MFD map to aid with orientation, there should be little reason for a CFIT ending to any flight.
But, pilots can be terribly creative at defeating any system designed to protect them. The crew must stay in the loop, even with SV and other tools. When the autopilot is coupled to an arrival routing, there’s a tendency to disengage from flight management, particularly when distracted by ATC requests, cockpit duties, or an airplane problem. At a minimum, the pilot flying must maintain situational awareness throughout, other factors notwithstanding.
The most hazardous phase of the flight, from a CFIT standpoint, is obviously the period encompassing approach and landing. A Dutch study of 156 commercial CFIT accidents showed that nearly 70 percent occurred during approach and landing. The study also showed a precision approach to be a definite accidents involved aircraft on a non-precision approach.
It’s also important to avoid complacency just because there are no mountains nearby. In the aforementioned study group, the majority of the CFIT accidents were at airplanes into the ground short of the runway, due to a lack of awareness of their true altitude. With a loss of situational awareness, it’s easy to miss an altitude limit at a step-down fix or misprogram the altitude alerter.
Most critical to situational awareness is knowing where you are, and what altitude is appropriate for that location. Never presume immunity because of your array of flat panel displays. GPS moving maps tend to embolden a crew into total reliance on the MFD to keep the airplane out of the rocks, when in reality it should be used as a confirmation tool, assuring us that the procedure we’re following is indeed the correct one.
The Flight Safety Foundation (not to be confused with Flight Safety International) has an excellent CFIT Prevention Checklist that rates a flight’s potential for a CFIT confrontation. For many years, FSF gas offered products that have been successful in preventing CFIT accidents. The checklist and other tools can be found at /flightsafety.org/ current-safety-initiatives/ controlled-flight-into-terrain-cfit/cfit-reduction-products.
Common ingredients for blissfully flying into the ground include those responsible for loss of situational awareness; poor weather, darkness, hurried flying and complex approach procedures with overlooked restrictions. Fatigue often plays a role, as the arrival comes at the end of a long duty day, perhaps when the crew is fighting lethargy on a night approach.
The lack of vertical guidance from an electronic glideslope amplifies the CFIT risk; thankfully, the increasing number of LPV and LNAV/VNAV satellite-based approaches can be expected to reduce the exposure. In the case of rapidly sequencing step-down fixes, it’s all too easy to lose track of oddly named points and the twists and turns along the way. And it is often the airports in mountainous terrain that require just such restrictions, in order to make an approach possible.
DME distances can be misinterpreted when more than one facility is present, requiring careful attention to the identifier associated with the mileage.
In the press of preparation for landing misreading the distances and altitude restrictions when lying off the wrong facility can be fatal. An alert pilot might spot something that doesn’t look right, but a tired crew is a set-up for disaster.
It’s also necessary to guard against controller errors, most particularly in non-radar environments and when there’s language difficulty. If instructions are given only semi-intelligibly, perhaps with non-standard phraseology, don’t be afraid to clarify the intent, and even challenge the instructions if it appears that ATC has misunderstood your position. Never blindly follow a heading into a hill, even if issued by higher authority.
When receiving a clearance, both pilots should agree that they have heard the same thing, by discussing the details and cross checking them. If in doubt at all, verify the instructions. Years ago, a Flying Tigers Boeing 747 crashed into a hill just outside the final approach fix at Kuala Lumpur International airport. The controller issued a clearance that stated, “descend two-four-zero-zero”, which was the FAF crossing altitude on the approach plate. Unfortunately, the crew understood the clearance as “descend to four-zero-zero”, and let down to 400 feet. Two GPWS warnings sounded, one 16 seconds prior to impact and another eight seconds later, but because the crew mistakenly believed they were cleared for the lower altitude, they ignored the warnings. Always be alert for suspicious wording of instructions.
Standard Operating Procedures for CFIT Deterrence
Business jet captain J.D. Lewis, well-versed in giving and receiving CFIT training, offers the following points: Always check your CFIT prevention equipment during preflight; Always select terrain on your MFD during initial descent; Always set the radar altimeter to its highest limit so it will remind you that you’re entering the CFIT “window of risk” and back up the TAWS; Have SOPs for callouts at certain altitudes to keep the crew alert as to situational awareness.
Testing our CFIT logic, he asked “If a crew is going into an airport in mountainous terrain for the first time, who should fly the approach, the old gray-haired captain or the young first officer?” If you said the old captain, you’re wrong. For CFIT prevention, he contends, “It’s better to have the sharp youngster doing the flying and have the wise eyes of the experience captain monitoring everything.”
Captain Lewis further recommends asking the instructor to concentrate on CFIT scenarios during simulator training; If the pilot has a CFIT crash in the simulator, he’s likely to never have one in real life.
SUMMING UP
To modernize an old proverb, “A gram of prevention is worth a kilo of cure”.
Taking time to run a CFIT checklist before a flight, and particularly before beginning the approach, can catch the oversight that would have set up a CFIT accident. Here are the salient points:
1. Consider the terrain along the departure and arrival routes, and discuss how you’re going to stay clear of these hazards with the other crewmembers.
2. Communicate clearly with crewmembers and controllers. Make sure both pilots agree on what was heard in the clearance, and if there’s any hint of miscommunication, get it clarified before proceeding.
3. Cover all the published information showing the proper altitudes at each segment; in most CFIT accidents, the information was readily available on the chart, but was ignored in the heat of battle, as distractions occurred.
4. Capitalize on using the on-board equipment, like TAWS, synthetic vision and altitude alerting. Sadly, in several CFIT accidents, the terrain feature was turned off or warnings were ignored. Be sure to use what you have.
5. Callouts should be standard operating procedure in every cockpit, even a single-pilot one. A verbal reminder of key altitudes is a wake-up call for a crew occupied with other duties.
6. Even when compared with all of general aviation, where the causes of accidents are much more varied, CFIT still accounts for 17% of all fatalities. We need to be continually aware of the CFIT danger and take steps to avoid the set-up for such an event.