by Scott Dyer

Photos courtesy of Scott Dyer and David Montiverdi

The snow started falling at Westchester County Airport a little after midnight, light at first but then picking up in intensity around 2 AM to a solid “moderate” with steady accumulations.  As of about 12 hours earlier, the NWS forecasters hit it right on the head for time of onset and intensity increases. So far, so good. 

With the snow starting to accumulate, the HPN snow removal operation swung into the high-energy dance of clearing our taxiways and runways for the start of morning flight operations, a dance that had been planned months in advance and fine-tuned the previous afternoon for the oncoming storm.  

We rode along with the HPN Ops snow team one January night to see how they get the airport surfaces clean for our use during and after a storm.  It's a year-long operation to get ready for snow and ice events, with planning and equipment acquisition in the warmer months through the summer.  

Equipment to Move Snow

The airport has been active in securing all the winter equipment that can be funded by the FAA, and then some more with other funds so that the job gets done properly.  Westchester has at its disposal 5 Sweepsters, each a 15 foot wide behemoth of rotating brush powered by a 485 horsepower diesel engine.  They can individually push 7,500 tons of snow per hour, aided by a compressor that blasts air at 300 miles per hour to get the snow away from the surface being cleaned. Those brushes wear out, as the bristles degrade from snow and surface contact after 80 to at most 100 hours of use.  It’s a four hour job for 2 mechanics to change the bristled part so this is best done before a major snow event if the bristles are getting to be marginal.

These Sweepsters suffice for up to about 6-8” of accumulated snow on the runway. For more than that, the County has in its stable 4 Oshkosh heavy plows of various plow sizes  between 14 and 22 feet, plus 4 Snow Blasters that make a home Toro snowblower look laughable.  The blowers are critical in moving piles of snow well away from the shoulders of runways and taxiways, and away from areas that could affect ILS integrity.  There is a whole squad of low-tech orange markers in the ground in front of the glidseslope antennas to help technicians to determine if enough snow is on the ground to deleteriously affect the glideslope signal (not usually a problem, most winters, at HPN).

There’s also a tanker of 3,000 gallons capacity for Potassium Acetate runway deicer (CH₃COOK, a potassium salt of commonplace acetic acid) that can deal with freezing rain conditions sometimes as an anti-icer before the rain starts, and more normally as a deicer for freezing rain and some compacted snow.  The Potassium Acetate has a freezing point of roughly -50°C to power through anything that’s frozen in a zone of 90 feet either side of the centerline.  

There are also spreaders on the plow trucks that can lay down sand 60 feet either side of the centerline when slippery conditions prevail. It is not just any sand, but (don’t laugh) special FAA approved airfield sand, material that is free of any corrosive substances and debris, specially sieved and sourced from a mine in Delaware that produces this good stuff.  Rounding out the equipment are a Loader/blower for ramp work, and the command Chevrolet truck that includes a small plow for touchups, that finish out the list.

Seasonal Planning and User Involvement/Communication

With the equipment in hand, there is the planning. It’s a crew of about 30 that makes the snow removal happen, sometimes with people brought in for placement overnight before the snow starts falling.  That crew complement, which changes some each year, needs to be assembled and trained in all aspects of winter snow and ice removal.

Airport Operations runs an all-user snow planning meeting in the Fall, a meeting that comprehensively runs through the plan of attack and what users can expect.  Among other things, that meeting highlights the priority areas for snow clearing, including Runway 16/34 and the major taxiways of A, C, part of G, K and L. This priority ensures that runway access is available for all aircraft, the runway exits at either end are available, and the perimeter road and the emergency access adjacent to Taxiway C are among the first cleared of snow and ice. 

This doesn’t mean that Runway 11/29 and other taxiways are left in the deep freeze; but it does provide a focus to the snow ops forces about what to do first.  Often, the crosswind runway is brushed, plowed and snowblown for opening the same day as an overnight snow event, even if it is not the first priority.  For major events, it may reopen the following day.

Hours Leading Up To The Snow/Ice Event

In the 12-18 hour period before a snow or ice event, another meeting is held for all interested parties to go over when and what will be happening, to respond to user (GA and airline) needs and to answer any questions. Special operations needs can be identified and taken into account at this meeting, and it is here that the latest information about suspension of airline operations, overnighting of aircraft and the expected schedule of snow/ice clearing can be exchanged. Interested parties can be put on the list for email distribution for Veoci airfield alerts through Airport Operations that include notifications of snow alerts, when this pre-event meeting will be taking place, runway condition reports, and the like.  

Another great source of much of this information, with Notams, runway closures, public advisories of meetings, and the like is the Airfield Status page that can be found at https://veoci.com/v/p/dashboard/wxs3wx.

It's Action Time

With the snow starting to fall, the plans coalesce into action.  That’s what we wanted to see when observing snow clearing operations in the wee hours one January morning.  

The on-field operations are run by the Airfield Supervisor driving the “Ops 39” command vehicle.  This job was being done by Dave Montiverdi, a veteran of several years in the role.  He’s a busy person, monitoring a number of different radios and frequencies, cell phone communications and occasional glances at a smartphone app showing weather radar.  Ops 39 runs the snow removal team, determines what tactics to use, measures runway surface friction for the ever-desired reports to pilots (more on that to come), coordinating runway closures and openings and contributing to Notams on runway condition.  

The goal is a black pavement, albeit it may be wet, something that is challenging to accomplish when a gusty wind is blowing dry snow over the runway surface.  It takes continuous trips of snow removal vehicles when it is still snowing or blowing. Those snow removal priority areas (e.g., Runway 16/34 and the critical taxiways) get continuous attention from the snow removers, as the runway will close if there are Pireps of Nil braking, several consecutive Pireps of poor braking, one-half inch of wet snow or slush, or 2 inches of dry snow.

Working with Ops 39 is an Operations Supervisor with a broader mandate of ensuring the safe, efficient and secure operation of the airport as a whole (including rescue and firefighting, and the landside snow removal contractors charged with making the airport safe for passengers and employees).  A Snow Bridge (Ops base station overlooking the airline ramp) that coordinates Notams and other team activities rounds out the structure.

While we mentioned earlier the individual snow removal capabilities of the Sweepster monster brushes, they aren’t used alone.  They are deployed often in echelon formations, first simultaneously clearing a zone left and right of the runway centerline, and then moving to the sides of the runways for the next pass.  The idea is to maintain 15-20 miles per hour or so, being slow enough for the brushes to do a good job but also fast enough that passes down the runway don’t take forever. Lather, rinse, repeat. It takes many passes to keep the fast-accumulating snow in check and the runway grooves clear of packed snow, one trip down the runway after another with the vehicles doing a choreographed turn on taxiways at either end of the runway before starting their run in the other direction.  Visibility is often down to ½ mile or less; blowing snow from wind and from the vehicles in front make this a hard job for the drivers who have to keep just a bit of overlap with the truck in front for the best cleaning.  The last driver on the side also has the most snow to move as the preceding vehicles push or brush it over to that side.

The cleaning gets interrupted when a departure or arrival needs to use the pavement, with Ops 39 coordinating with ATC on how that is best accomplished.  Then it is all equipment off the runway, including those working on taxiways that may be coming close to or over the hold short lines, until the aircraft operation has taken place.  Then it is back on the runway to keep things clean while the snow is still falling or blowing in the wind.

Fortunate, too, is that after an overnight snow event, the airport is a bit slower waking up to air operations than on a more normal morning.  It takes longer to deice the aircraft before departure, taxiing is slower, and those leaving the airport may be doing so up to an hour after the usual schedule.  All this means there is more time for the snow crew to give them the best runway possible. It is a joy to see a departure off a runway that the removal vehicles have just been working hard on and exited.

It's All About Friction

Many pilots grew up with the highly subjective reports of braking action, ranging from Good through Fair and Poor to Nil, and the report depending on who was at the controls, the type of aircraft, and autobraking in use, if not the phase of the moon.  Some measure of objectivity has been imposed by FAA for some contaminated runway surfaces, and a key component of that is using a µ (mu, pronounced myew) meter.

The device, used by the Ops 39 command vehicle, is made by Bowmonk and it’s a decelerometer.  We had thought it was a simple measurement made while driving down the runway but it is a lot more sporty than that, sometimes bordering on the violent.  In each zone of the runway, touchdown (basically first 3,000 feet of Runway 16/34), midpoint (middle section, as you’d expect) and rollout (last few thousand feet of the runway), three readings are taken just off centerline.  The truck is moving about 20 miles per hour when the brakes are sharply applied, and the unit calculates runway friction.  It is the average of the three readings in each portion of the runway that is the useable value.  You can feel immediate friction, or some sliding and then grabbing, depending on the runway friction being experienced.  It is not exactly gentle but far better than trying out the braking in an aircraft. 

µ values get added into a Runway Condition Assessment Matrix, that also factors in temperature and type of runway contaminant, to come up with a Runway Condition Code (RCC)  of 6 (clear and dry, the best) to 0 (minimal to no braking). All sorts of rules apply to when a µ reading can increase (make better) a RCC (basically the µ report can only improve a RCC of 0 or 1, not higher RCCs), but all pilots really have to know is the basic RCC number for each zone and then consult their materials to determine required runway lengths for the prevailing conditions.

Share the Love

Taxiways get their attention too, whether on the airline side of the field or on the west side.  While within the Priority 1 group Runway 16/34 takes the most attention, the Priority 1 taxiways get their care too especially as the snow slows.  The same echelon deployment of the snow-removers clears the taxiways.  A good leader will work an efficient pattern of turns while keeping brushes and plows in the same direction as much as possible.  There is an art to the snow clearing, not inviolate rules and procedures by any means as higher winds may cause different clearing patterns to be used, but it is a joy to see a similar finesse in the snow removal process as we see in the cockpit, with smoothness and no wasted motion.

Wait for the Movie 

Our visit with the snow removal crew was highly informative, and we cannot thank John Starace (who spent hours educating us on what his crews do), Dave Montiverdi and the Operations staff enough for their unstinting sharing of time and the warm welcome that we received.  Steve Ferguson, Assistant Airport Manager, provided support and jumped on the suggestion for this article.  Pilots and FBO denizens do not often have occasion to interact with the folks in Operations but they dedicated, hardworking, love aviation and are critical to our success as an airport. 

This video is a tribute to the HPN Snow Removal Team.  Enjoy!