An Illegitimate Son Of DREADLE?
After years of carping irritation from the NTSB, the FAA has decided to proof-test a system that will alert a pilot directly if there’s an impending or actual runway incursion underway that will affect his safe landing.
The FAA’s system is called FAROS (Final Approach Runway Occupancy Signal) and it utilizes the PAPI (Precision Approach Path Indicator) to warn the oncoming aircraft on approach about any interlopers on “his” runway.
The similarities to DREADLE, a 1999 concept, are quite striking (see tinyurl.com/2szzfv and ASW July 16, 2001). But there are some fundamental differences. FAROS uses distant blinking lights and DREADLE uses strobe-lights and unmistakable attention-getting aural alerts over VHF radio. FAROS uses limited activation zones in high threat runway entry and crossing areas and DREADLE covers the entire runway system (tinyurl.com/yrk5de).
Who’s PAPI?
PAPI is simply a wing-bar of four sharp-transition glideslope lights set in a row well down (almost halfway) on the runway’s left side (although it can be on both sides). On the correct approach slope the pilot should see the light-pair nearest the runway as red and the two furthest from the runway as white.
Below the nominal 3� slope the three nearest the runway show as red and so on. However, if another aircraft should enter the runway due to pilot or ATC error, it will trip a treadle (a weight-sensitive sensor loop across the taxiway’s holding point) and those lights will flash. The FAROS central processor polls each loop twice a second. (tinyurl.com/2zd7tb )
Pharos was the great maritime lighthouse of Alexandria. It dated from the 3rd Century BC and was one of the Seven Wonders of the Ancient World. The modern FAROS has been in use at Long Beach over spring 2006 and it too has some pilots wondering, as the usage might appear to be a little convoluted.
There are three stages on the approach whereupon, having seen the PAPI blink at you, there are different actions for the approaching pilot, depending upon the scenario: (tinyurl.com/2hlkf5)
a. Scenario One: PAPI lights flash above the “contact height”
b. Scenario Two: PAPI lights flash crossing through the Contact Height
c. Scenario Three: PAPI lights flash inside the Contact Height
d. Scenario Four: Report the PAPI lights to ATC as being “blinking well” unserviceable
Bewitched And Bewildered?
With a little use of the imagination, one should be able to envisage international pilots from faraway places rubbing their eyes and plodding on in awe and wonder at what it all means. Acceptance is by no means assured.
Compare that with DREADLE’s philosophy. Once the runway is “armed” by ATC for a landing or takeoff, any taxiing traffic (trucks included) crossing that self-same foul-line would trigger an automated aural DREADLE Alert, overtransmitting (if necessary) on the tower and ground frequencies in use. “Whoop, whoop! DREADLE Alert! DREADLE Alert! Unauthorized Traffic entering runway 02 at the threshold”.
In the DREADLE case, both the pilot and ATC get the radio’d warning but also the infringing pilot or trucker who’s just blundered onto the active runway. And what’s more, it would work for low visibility ops (LVP) where aircraft are required to hold even shorter so as to not mask the ILS beams for Cat III auto-landers.
In that case of low landing visibility, the PAPI may not even be seen at all. It would be blinking in the blind. FAROS requires “pilot training”. DREADLE requires a set of human ears. With there being at least two such sets in the average cockpit, DREADLE’s alerting should be doubly safe.
Not to belabor the point, DREADLE also works for aircraft taking off in low visibility. That’s the other side of the question that’s being artfully avoided by supporters of FAROS. In the FAROS FAQ pilots are advised that upon entering the Runway 30 Departure zone at Long Beach, they will cause the PAPI’s to flash; but pilots are exhorted just to ignore that anomaly and “to continue their takeoff procedure”. Once again, try to imagine the bewildered foreign pilot.
Recall the Milan Italy (Linate Airport) collision on October 8, 2001. A bizjet (D-IEVX) became lost on the taxi-out and blundered onto the main runway in the fog just as Flight 686, an SAS MD80, was taking off. The two planes collided at approximately 270 km/hr in a visibility of around 200m.
There were no survivors from either aircraft and further deaths in an airport building hit by the crippled passenger jet. That accident is eminently repeatable. As FAROS is only being trialed on the one 10,000ft runway at Long Beach, it’s not known (but doubtful) whether it can, like DREADLE, protect against landing or take-off collision risks at runway intersections. It’s common-place to have ATC use one intersecting runway for takeoffs and another for landing traffic.
How FAROS Works
When the foul line is crossed and any monitored zone on the runway becomes occupied by a stationary or slow-moving target, a signal is provided to pilots on approach that the runway is occupied.
It can be imagined that pilots will get used to seeing those lights flashing more often than not at a busy airport where the intervals between takeoff and landing are quite abbreviated. “Cry wolf” springs to mind, particularly because aircraft entering the runway and taking off will also trigger the FAROS PAPI blinkathon.
So how has FAROS been doing so far? Jaime Figueroa, FAA’s Surface Systems Manager in Washington, D.C. was asked to blink twice for a thumbs up “yes”, and just once for no.
“We turned it on in August and it’s been performing well,” Figueroa said unblinkingly. “Will it save the day? It’s too early to tell.”
Long Beach has held two records and has one characteristic that qualified it for the trial.
Most air carrier flights during the preceding period: 28,939 in 2005.
Most general aviation flights: 475,364 in 1999.
Five intersecting runways.
The FAA needs a full year of statistics before it can evaluate performance, Figueroa said. FAROS also needs at least a one-year evaluation before it can become an officially commissioned FAA program. Not only will FAROS be judged by engineering standards and how it impacts runway incursion rates in a realistic multiple and parallel runway environment, but also on whether it makes economic sense.
“Is there a business case for it? And what are the costs and benefits?” Figueroa posed. But with an annual rate of 63 million takeoffs and landings across the United States annually, reducing runway incursions is a top priority. At least one incursion a day occurs somewhere in the continental US.
The Need
The NTSB is investigating a Jan. 5, 2007 runway incursion at Denver International Airport involving two airliners. At 7:28 a.m. MST, Frontier Airlines flight 297, an Airbus A- 319, broke out of low clouds just as it was about to land on runway 35 left.
The Frontier flight crew saw a Swearingen Metroliner, Key Lime Air flight 4216, which had inadvertently entered the runway. The Frontier flight immediately executed a missed approach. It is estimated that the aircraft came within 50 feet of each other.
The Airport Movement Area Safety System (AMASS radar) alerted the control tower personnel of the situation at the same time the Frontier crew saw the Metroliner on the runway. Weather at the time of the incident was one-half mile visibility, ceiling 600 feet overcast, snow and mist.
Cliff Honeycutt, owner and president of Key Lime Air based at Centennial Airport, said the snow and the snowpiles partially to completely obscured the ground markings, the signs and the runway lights. Think about that statement and reflect upon the FAROS warning methodology.
Obviously there’s no benefit in a system such as ASDE-3/AMASS telling ATC that they’ve just had a runway collision. That’s the sad record of AMASS (tinyurl.com/32m44d ). ATC will have seen it happening simultaneously (as above) and would have been powerless to warn the pilots in time.
The same limitation applies to the newer radar-based ASDE systems (Airport Surface Detection Equipment). Only a direct aural “heads up” warning to the pilots involved will work to save the day – and radio is the conventionally classic (and universally understood) means by which that should be done. However. DREADLE does also incorporate a bright laser- strobe that will flash at taxiway intersection points in order to instantly highlight the physical location of the intruder.
Whatever the outcome of the FAROS Trial, it is encouraging to see the FAA moving forward, however slowly, on an NTSB top priority safety topic. But to really appreciate the size of the problem you have to look at somewhere like LAX (tinyurl.com/2fw7g8).
LAX is working on its more serious problems with more serious money. There seems to be no easy way to deal with the fact that 900 big jets a day cross its active runway to get to terminals, so the plan is to spend $1.5 billion to move the two sets of parallel runways further apart. That seems like a lot to spend for a relatively modest improvement, and considerable opposition to the plan has sidetracked it , which are two more reasons LAX needs something like FAROS, or DREADLE.