Despite Headway, CFIT Remains Persistent, Deadly Threat

Air Safety Week, Jan 10, 2005

More than 190 pilots and passengers were killed and nearly 30 aircraft were destroyed in 2004 by crashes involving controlled flight into terrain (CFIT). Most of the aircraft involved were not required or, if required, had not yet installed terrain awareness and avoidance warning systems (TAWS), according to a new study.

The study was prepared by Don Bateman, chief flight safety systems engineer at Honeywell [NYSE: HON], one of the world's leading suppliers of TAWS equipment. To be sure, the company has a business interest in highlighting the persistence of the CFIT hazard, but the study findings reflect a deadly problem that has been of continuing concern for years (see ASW, Aug. 30, 1999).

Most of the accidents in the Honeywell study involved smaller aircraft, as nearly all large passenger-carrying aircraft have been equipped with TAWS (the International Civil Aviation Organization established a Jan. 1, 2003, deadline for installation on aircraft carrying 30 or more passengers). TAWS is the generic acronym for what also are known as enhanced ground proximity warning systems (EGPWS). Unlike the earlier and more limited GPWS, EGPWS features a "look ahead" function that provides earlier warning of dangerous terrain. Not only does the EGPWS technology warn pilots of rising terrain ahead, it warns of threatening terrain off to the side, thereby providing additional protection during turns. It is estimated that EGPWS probably prevented about 45 deaths in 2004, although Bateman hastened to add, "EGPWS is not the panacea for all CFIT situations; the big variable remains the pilot's response."

The deadly toll involving smaller aircraft reinforces the recent call by Jim Hall, former chairman of the National Transportation Safety Board (NTSB), to install TAWS (EGPWS) on smaller aircraft (see ASW, Jan. 3). Indeed, in less than 90 days, by March 29, all turbine powered aircraft in U.S. registry carrying six or more passengers must have TAWS installed or face grounding. If this mandate date had been four years earlier, in March 2000, about 180 lives might have been saved, Bateman estimated. Moreover, the requirement does not cover aircraft of lesser capacity or piston-powered aircraft. By one estimate, turbine powered aircraft constitute barely 7 percent of the general aviation (GA) fleet.

In a five-day period last October three CFIT accidents occurred involving aircraft covered by the March 29 deadline but not yet equipped:

* Oct. 19, 2004 at Kirksville, Mo., 13 fatalities. Part 121, scheduled carrier (classic GPWS installed but no warning as aircraft was in the landing configuration; EGPWS purchased but not yet installed).

* Oct. 23, 2004, Brown Field, Calif., 5 fatalities. Part 135, on-demand carrier.

* Oct. 24, 2004, Blue Ridge, Va., 10 fatalities. Part 91, GA.

In short, airplanes fitted with EGPWS are less vulnerable to CFIT. For pilots not thinking far enough ahead to be ready for a missed approach (i.e., they get behind the aircraft), as may have been the case in the Oct. 24 crash, EGPWS can be their "second chance." Light poles, tall towers with guy wires and such in the vicinity of airports, particularly GA airports, can pose a real hazard to the unwary. These man-made hazards are incorporated into the terrain database by which EGPWS compares the airplane's position in space to the ground. "Bargain basement" versions of EGPWS are now available for GA aircraft and can go a long ways toward blunting the "one strike and you're out" penalty so characteristic of CFIT accidents.

Below, profiles of descents to disaster involving a number of recent CFIT crashes. It is evident from these portrayals that hundreds of lives might have been saved by mandatory and more urgent deployment of EGPWS technology. There is a way yet to go in CFIT interruptus.

Profile 1: Oct. 19, 2004, Kirksville, Mo. Jetstream 32; 12 killed, 2 survivors

Classic GPWS was installed but no warning was given as the aircraft was in the landing configuration. EGPWS had been purchased and was awaiting installation; if installed, it would have provided 19 seconds warning. All profiles courtesy Honeywell, with slight modifications by ASW

Profile 2: Oct. 23, 2004, Brown Field, Calif., Learjet 35A; 5 killed

Probable flight path into Otay Mountain. Had EGPWS been installed, it would have provided nearly half a minute warning.

Profile 3: Oct. 24, 2004, Martinsville, Va., Beech 200; 10 killed

Probable flight path profile to impact on Bull Mountain. No GPWS or EGPWS installed. EGPWS would have provided multiple warnings.

Profile 4: Nov. 22, 2004, Houston's Hobby Airport, Texas, G-III; three killed

Assumed flight path and predicted EGPWS warning. The accident aircraft was fitted with GPWS but not EGPWS. If EGPWS had been installed, it would have given a 25 second warning before impact independent of the GPWS glideslope signal. The 125 ft. light poles were not in the FAA obstacle database.

Profile 5: Feb. 26, 2004, Mostar, Bosnia-Herzegovina, Beech 200; 9 killed, including Macedonia's president