Out of Control
During the winter, flying an ILS to minimums is the easy part. Once you break out of the crud, finding and landing on a snowbound runway holds more hazard than most pilots realize.
During the winter, dozens of aircraft come to grief on ice and snow-covered runways, sometimes after completing an otherwise uneventful instrument approach.
These accidents are rarely fatal but they do illustrate a harsh reality of winter flying. We worry incessantly about airframe icing but slick runways, snowbanks and low visibility test the limits of man and machine and very often, neither is up to the task. A spectacular accident a few winters ago shows how condtions can conspire to undo the best efforts of even an experienced airline crew.
USAir Express Flight 5108, a British Aerospace Jetstream, was on a flight from Charlotte, North Carolina to Beckley, West Virginia, an uncontrolled airport in the southern part of the state. The date was March 17, 1993, a few days after the infamous Storm of the Century had dumped 31 inches of snow on the Raleigh County Airport in Beckley.
As secondary airports go, Raleigh County is typical. It has two runways and four approaches, including an ILS with standard 200-and-a-half minimums to runway 19. Following the big storm, the airport was closed for two days but the weather had cleared enough for crews to plow the runway. On the night of the accident, another weather system had moved in, bringing low ceilings, freezing drizzle and fog.
As Flight 5108 approached Beckley just after sundown, the NWS observer on the field reported a measured 200-foot overcast, with a mile of visibility in light drizzle, light snow and fog. Runway 19 had been plowed but a notam warned that the surface had been cleared to only 130 feet of its 150-foot width. Two-foot high snow berms encroached on both edges of the runway but the edge lights were reportedly visible. The Jetstream's flight from Charlotte was uneventful, although it overflew a scheduled stop at Bluefield, West Virginia because the weather was below landing minimums and because there were no passengers to drop or pick up. Flight 5108 arrived in the Beckley area just before 7 p.m. local time. As required by the regulations, the crew checked the weather and learned that it was above minimums, although they would have a 7-knot tailwind.
The crew performed its in-range checklist and the Captain briefed the approach carefully with the First Officer. Shortly after the Jetstream turned onto the localizer, the First Officer confirmed with the Unicom operator that the runway lights were at full intensity. As the aircraft neared decision altitude, the FO called off altitudes. Seven seconds after calling "one-hundred above," the FO announced lights in sight.
First Officer: "I got the lead-in lights, continue."
Firrt Officer "There's the end of it."
First Officer: "There's the REILs."
Captain: "Taxi light's on, right?" (sound of click)
Captain: "Jeez...oh #, we've lost it...oh man, I don't believe it..."
The next day, the NTSB accident investigator discovered that the Jetstream had touched down on the runway, but well left of the centerline and on the unplowed portion of the runway. It rolled through the thick snow for 435 feet, at which point the right gear leg sheared off and the left gear began collapsing.
The airplane then slid out onto the plowed portion of the runway and nearly reversed direction before coming to rest atop the snow berm along the runway edge. The crew and two passengers escaped without serious injuries.
As wintertime runway accidents go, Flight 5108's wild ride was unusual only in its severity. To put things in perspective, we recently looked at several years worth of icing accident data. The overall totals from two years-1988 and 1989-are typical. In 1988, the NTSB's records show that there were 20 icy runway accidents; in 1989, the total was 15. Viewed against the big picture, runway excursions rank third behind airframe icing and carb icing, the leading cause of icing-related accidents.
However, we suspect that the actual number of runway accidents is much higher because many simply go unreported. We know of incidents in which airplanes careened into runway lights or skidded into snowbanks with only minor damage. No accident reports were filed.
Touch and Goes
If there's such a thing as a "routine" runway excursion accident, it's probably the student pilot who suddenly finds himself parked in a snowbank while practicing touch and goes. Having an instructor aboard is no guarantee of a safe outcome, either. On a dry runway, an alert instructor can correct a student's minor squiggles with a quick stab on the rudder. When the pavement is covered by snow or ice, a minor drift can instantly turn into a headlong careen off the runway.
Sometimes, an instructor's attempts to salvage a landing gone bad only makes things worse. In one accident in North Dakota, a CFI was checking out a pilot in a Cessna 172RG. The student was attempting a touch and go on a 2800-foot, snowcovered runway. The trainee landed long, then caught the CFI by surprise when he attempted takeoff with only 800 feet of runway remaining. The instructor reacted, but too late. As the aircraft slid to stop, it departed the left side of the runway and nosed over in a snowbank, causing serious damage.
Earlier in the same week, a pilot attempting to land a Piper 180 at a Vermont airport had a similar run-in with a snowbank. When he started to slide after touching down, he tried to go around. The left main was sheared off by a high snow pile and the pilot returned to land on the right main, significantly damaging the left wing.
If the 1988-89 winter seasons are an accurate indication, the majority of slick runway accidents occur at uncontrolled fields. No surprise there. Outlying airports tend to have narrower, shorter runways and runway lighting tends to be minimal or non-existent. More important, as the crew of Flight 5108 discovered, a major storm can overwhelm the snow removal capabilities of small airports.
Give It A Try?
Knowing this, you'd think that pilots would give small, snow-covered airports a wide berth and most probably do. But there are always a few who are willing to tempt fate by landing or taking off on short, snow or slush-covered runways. That's exactly what the pilot of a Cessna 182 did at small Wisconsin airport. He elected to land on a 2500-foot snow-covered grass strip but wound up nosed over off the end of the runway. He told accident investigators that he flew the approach fast and touched down long, virtually assuring that he would have insufficient distance to stop.
With their wider runways and superior snow removal, towered airports-especially air carrier airports-have fewer runway excursion incidents. However, as in the case of Flight 5108, the most damaging runway excursions seem to involve faster, heavier aircraft, whether at towered airports or not. The NTSB's records contain numerous accidents in which relatively fast airplanes (medium twins and up) complete an instrument approach only to touchdown in a snowbank or careen out of control off the end of the runway. Even if the crew is acutely aware of the hazards and prepared to counter them, suprises may yet lurk upon touchdown. Two accidents illustrate the point.
In the first, an MU-2 on a cargo flight into Spokane, Washington had completed an ILS just after dawn. Spokane is a towered field and even though the runway had been plowed, it was still covered by 2 inches of ice and snow, some of which had been heaped up on the left side of the runway, burying the lights. The pilot said he thought he had landed on the centerline but the aircraft drifted left and went out of control in a snowbank.
In the second accident, the crew of a Lear 25 was inbound to Bend, Oregon, an uncontrolled airport. The weather was clear but the crew suspected the runway might be icy. Before landing, the crew made a low pass to examine the surface and, seeing no evidence of ice or snow, they returned for landing.
On rollout, some 2000 feet beyond the landing threshold, the Lear began to skid. The aircraft was equipped with a drag chute but it was inoperative. Unable to stop, the Lear overran the 5000-foot runway, struck a fence and came to rest in a ditch. A post-accident inspection revealed that the last half of the runway was coated by black ice, which is all but invisible.
Avoid the Hazard
From the warm comfort of an armchair, it's great sport to second-guess any pilot who comes to rest in a snow-filled ditch or tears off out of control, chopping off edge lights like so many bowling pins. After all, isn't the hazard obvious and anyway, why not just cancel the flight entirely or land somewhere else? The hazard is obvious. But most experienced snowbelt pilots will tell you that judging the degree to which a snowy runway will affect aircraft control is next to impossible. Then there's the challenge of actually seeing the runway on a snowy, gray day or at night.
In the case of Flight 5108, the Captain was no newcomer. He had more than 12,000 hours, some of it flown in snowy West Virginia. As we said, no cause has been deter mined but judging from the NTSB factual report and CVR recording, the crew carried out the flight professionally and with all due care and yet were caught completely by surprise when the aircraft wound up in the snow.
The all-time, bulletproof option is to just bag the entire flight. For-hire crews have that option, but it's not always easy to exercise it; there's enormous pressure (often unspoken) to deliver the paying passengers. The pressure is less for Part 91 pilots but it's still there. One go/no-go test is this: how important is the trip compared to the prospect of ending it nosed over in a snow drift? A variation of this is IFR contributor Bob Gardner's all-purpose test: How will I look in the accident report?
Still want to go? Stack the odds in your favor by flying into an air carrier airport or one that has known snow-removal capability. A long drive to the destination is better than a short skid into the runway lights. Avoid short, narrow paved runways and turf strips. Even if the runway and taxiways are dry, snowberms can do massive damage to wings and landing gear.
If you must use a small airport, try to arrive in daylight and don't rely on notams for field conditions. Call ahead for a detailed report on conditions, including lights. Is the runway plowed to its full width and length? Is the asphalt dry or covered by thin, patchy snow? Has it been sanded? Are lights on both sides of the runway visible? Be extremely cautious when a sub-freezing dusk follows a warm day; the meltwater from plowed snow can freeze into sheets of ice. If possible, have a vehicle check the runway before takeoff or landing.
Stick to Daylight
Clearly, the accident record and common sense suggest that the risk goes way up at night, in low visibility or in a crosswind or downwind landing. If you attempt an approach in any of these conditions (or all three), the risk is much higher. Again, the long, wide and well lighted runways at air carrier airports are the best option.
When approaching at night in the snow, it may be better to leave the landing light off until just before touchdown. The reflection off airborne snow can be mesmerizing and will make it harder to see the runway. When operating on snowy and icy surfaces, slow is better and that applies equally to landing and taxiing. Those slow, short-field techniques you learned as a student but probably haven't used much since are suitable for landing on slippery surfaces. One fact of winter flying is that the same conditions that put ice on the runway may put ice on the airframe. In that case, a slow approach won't do. You'll have to keep the speed up, land without flaps and take your chances .
Another technique-a low-level drag before actually landing- isn't a bad idea, either. Although it didn't help that Lear crew in Oregon, dragging the field may reveal snow or slush that's too deep to chance. Or maybe it'll scare you into landing elsewhere.
On a dry runway, touching down in a slight crab is sloppy technique but no big deal; once the tires grab, the aircraft cocks itself straight. Try that on a slick runway and you'll all but guarantee a skid. If that happens, regain control with vigorous rudder input and judicious power. In a twin, differential power may be more effective than rudder. Don't try to steer with brakes; they'll probably be useless.
Salvaging a skid by attempting an immediate takeoff would appear to be chancy, too, according to the accident record. On a slippery runway, the tires lack the traction to counteract torque and P-factor so unless you're quick on the rudder, firewalling it could worsen the skid. And if you don't get airborne before hitting the snowbanks, you'll do more damage because you'll be going faster. A slow-speed slide into snow might be more acceptable.
The only good thing about snow on runways is that it eventually melts, sometimes in a matter of hours. Waiting for that to happen seems a small price to pay to avoid the ignominy of a surprise sleigh ride through the airport boondocks.