Can YOU stop a jet on a winter runway?
Whenever an airliner slides off a taxiway or runway in winter conditions, the public and the media asks dozens of questions related to one overriding concern: how could this happen?
But for every other flight that lands on a winter-affected runway without incident, there were dozens of questions correctly answered by pilots related to THIS overriding concern: how can we assure that DOESN’T happen?
I’ve been flying in and out of LaGuardia and Washington Reagan all winter, accommodating ice, low visibility and contaminated surfaces in what has been an exceptionally vigorous winter storm season. The questions and correct answers required to assure a safe flight under such conditions are neither straightforward nor simple. Here’s the decision process–YOU decide what to do.
First, before we even depart for an airport affected by winter weather, we think about the factors that affect our landing: weight, wind, landing distance required, and runway surface conditions. And there are no easy answers any of these questions.
Weight comes first: considering stopping, you’d want weight to be the lowest possible, right? If only it were that simple: the primary, most variable weight in flight is fuel–if you reduce fuel weight to the bare minimum, you also reduce flying time to the bare minimum. The facts of life when flying into a major metropolitan airport include delays–demanding MORE flying time, thus more fuel and thus more weight. If you have only the minimum fuel aboard required to fly the distance, you are screwed: at the first delay (and airborne holding assignments of up to 30 minutes are typical) you must divert.
What you need to do is carry enough fuel to fly the miles AND accommodate typical, historically predictable enroute holding. We’ll have to be sure that we can still accommodate that weight on landing (checking landing distance charts) but that’s a separate question to be dealt with: for now, tank as much fuel as required to fly the distance and hold for a reasonable duration enroute.
We don’t leave the rest of the questions for arrival, but we do answer them late in the flight when the variables have been sorted out: once we’re in the terminal area, we finally can predict an accurate landing weight.
So we request the data-linked landing distance chart for our specific weight which is calculated by computers back at our tech center and sent to our on-board printer. Problem for you is this: the chart also has variables you must resolve: what is the runway condition, and what is the braking effectiveness?
Those two variables can not be definitely determined because the informational reports are both very subjective: the “runway condition” must be determined in reference to varying standards. Our airline calls a runway “contaminated” when 25% of the landing surfaces is contaminated by ice, standing water or snow.
Another airline may allow 30%, another 60%, so there’s never any “contaminated” determination available other than reports from previous company aircraft. But even those are subjective–how do you eyeball 75%–and in winter storms, conditions can worsen by the minute.
Braking effectiveness is another subjective report: what I consider “fair” braking for my jet (and I report this to the tower after landing based on what I just experienced) might be “good” for a lighter regional jet or “poor” for a heavier aircraft or and aircraft with less effective brakes. And, in heavy precip, that can change drastically in just minutes.
The landing distance charts reference “good” or “fair” in the conditional determination of braking effectiveness–but you now know that “report” is vague at best. Still, you must decide which calculation to use.
There’s also more than one chart for landing distance. The first one assumes that you touch down at the Visual Approach Slope Indicator (VASI) aimpoint which is about 1,500 feet from the runway threshold. There’s another chart that computes stopping distance from the visual touchdown markings on the runway some 500 feet prior to the VASI aimpoint. That chart, with the additional distance from the earlier touchdown point, may allow you to land based on stopping distance.
But can you accomplish that? The “you” is key–no one on the ground can answer that. Ultimately, the captain decides, and here’s what he’s thinking: what are the winds? A tailwind will make that very difficult, a headwind will help. But can you count on either wind report? Those reports, like “braking effectiveness,” have a very short shelf life–winds change minute by minute. Do you think your landing wind is reliably a headwind, or at least not a tailwind? Again, YOU have to answer that based on subjective reports.
As far as the visual touchdown aimpoint, are you going to be transitioning to this new, shorter target from an instrument approach, which has a more distant touchdown point more like the VASIs? If so, do you have adequate distance, time and visibility to do so? And the skill?
Finally, landing rollout must be done exactly right: spoilers deployed, reverse thrust promptly initiated at the proper level, and brakes applied promptly and correctly. That sounds easier than it is.
First, spoilers normally are automatically deployed–but that deployment needs certain prompts: main wheel spin-up is a primary trigger, and patchy ice may keep wheels from spinning, delaying auto deployment, even as you eat up critical landing distance. Or, like last month, I landed my 737-800 on a wintery DCA runway without the auto-spoiler system working. I agreed before dispatch on the flight that I could and would do so manually. My judgmental call, a fact of life in airline flight operations.
Regardless, the point is, the crew must assure spoiler deployment and effective reverse thrust AND full braking–all in a millisecond when landing distance is critical.
As crucial, you must put the jet down on the exact spot–neither before nor absolutely, not beyond–and put it down firmly to ensure wheel spin-up, essential for traction and auto-spoilers. If you’re the ignorant smartass getting off the plane after that trying to be witty by saying “You must be a Navy pilot, that was a carrier landing” or “I guess the brakes work,” I’ll ignore you–but the crew will write you off as an ignorant smartass just the same.
There’s no feeling worse in the cockpit than the anti-skid system releasing the brakes on rollout, even if you’ve done everything correctly, but that’s essential too: the system applies braking force to the very brink of a skid, beyond which there’s no braking, just sliding. If you’ve calculated your stopping distance based on “fair” reports, you can expect some releasing as the brakes do their job. All the more reason for a firm and accurate touchdown.
I expect and require every landing to be on the correct speed (faster makes stopping more difficult) and on the right spot, even at DFW Airport with miles of runway to spare, simply because it must be (for me) the rule rather than the exception when I fly to LaGauardia, Washington Reagan or Santa Ana-Orange County with shorter runways. “Pretty” landings are a Hollywood contrivance and have no place in the actual profession.
When we stop safely and exit the runway, that’s because we correctly solved the puzzle: weights, speed, touchdown point, winds, and braking distance. For passengers, that means a safe trip completed. For the cockpit crew, the work is only beginning: all of these variables must be dealt with successfully again in order to execute a safe take-off or abort on that same winter-affected runway.
The airline industry in the United States has an enviable safety record, which is why the very rare incident gets so many media headlines. The real news is, overall, airline pilots are doing their job very well.