by Bernard Maugis, Civil Aviation Safety Inspector, System Safety, Quebec Region, Civil Aviation, Transport Canada
A recent search of Transportation Safety Board of Canada (TSB) statistics for occurrences involving helicopters in a "collision with terrain" accident from 1998 to 2008 yielded 303 hits. Of those 303 accidents, 18 occurred in whiteout conditions. There were 45 passengers on those 18 flights; 23 were injured and 13 lost their lives. The pilot’s experience level did not appear to be a factor. In anticipation of the upcoming winter season, and considering the above statistics on the dangerous whiteout phenomenon, we felt it would be worthwhile to reprint the following article, titled "Whiteout," which was originally published in Aviation Safety Vortex 4/2003.
Back in the old days, a Canso was on a very long IFR ferry trip in the Arctic Islands. For the crew it was a monotonous routine-monitoring the instruments and listening to the roar of the two big radial engines just above their heads. There was nothing to see out of the windows, just a white, featureless blank.
It was a boring and undemanding afternoon, until the captain looked out through the windscreen and saw his flight engineer standing in front of the aircraft with a big grin on his face. This came as quite a surprise to the captain, whose training and background had not prepared him for coming face-to-face with anyone while in cruising flight, let alone a member of his crew.
The Canso had flown into very gentle rising snow-covered and featureless terrain. The impact had been so soft and gentle that amidst the rattling, roaring and vibrating that constitutes cruising flight in this type of aircraft, the crew hadn't noticed the deceleration at all. The flight engineer had happened to look out of one of the Perspex blisters in the tail of the aircraft and discovered that he could see the ground, quite motionless just a few feet below him. So he got the aluminum ladder out, climbed down to the ground and walked round to the front to get the pilot’s attention.
Maybe it’s urban legend; maybe it’s a true story-who knows? I suppose, considering the boat-shape of the Canso hull, that it could happen, but one thing's for sure-it’s not likely to happen in a helicopter. I do know one chap who claims to have hit the ice at cruise speed in a Bell 206 on fixed floats, and suffered nothing but a gentle bounce, but the more likely scenario involves a catastrophic break-up, and debris field.
Whiteout conditions mean a gradual loss of all visual references
If you are a VFR commercial pilot flying in Canada, sooner or later you are going to experience loss of visual reference to some extent. If you're lucky, it will be for only a second or two before your frantic eyes find a clump of trees or something else that tells you which way is up. If you/re not lucky, you’ll likely join the ranks of those who have found out the hard way that the "seat of your pants" is easily fooled. For those who haven’t experienced it, it can happen something like this:
The weather is deteriorating. You know the situation is not good, but you press on, hoping it will improve. It doesn't-it gets worse, and you find yourself losing good reference. Your eyes are darting from side to side and your pulse increases. You slow the aircraft, still searching for visual clues. Your breathing speeds up, and your pulse is now racing. You feel a cold rush flood through your body, and a strange sensation of your insides relaxing as adrenalin and fear overcome concentration and reasoned thought. Then comes the disbelief; the absolute unwillingness to accept that your body has let you down and you are helpless.
Let’s look at some examples of descriptions taken from Canadian accident reports from the past few years:
- During approach for landing on a glacier and at 8000ft above sea level (ASL), the pilot of the 205 entered a whiteout-like condition in swirling snow. He lost all visual reference and touched down hard, causing damage to the skid-gear.
- Nearing destination, the aircraft flew into whiteout conditions. All visual reference was lost before the pilot could complete a landing, and the helicopter rolled over on touchdown.
- The main rotor hit the ground after the left skid dug into snow surface during a mountaintop landing. The aircraft was still in forward motion at touchdown due to wind shift and whiteout.
- The sling load proved heavier than the pilot expected, and he couldn’t get airborne. He hovered with the load resting on snow-covered ice and lost visual reference in the blowing snow. The pilot released the sling load, while the helicopter was in a nose-high attitude. The tail rotor struck the snow surface and the machine rolled over.
- The pilot encountered whiteout conditions and attempted to turn back. The aircraft crashed on the Arctic sea ice during the turn.
- The pilot lost visual reference in whiteout over an ice-covered inlet and flew into the ice.
- The pilot aborted his third take-off attempt in blizzard conditions. On touchdown in whiteout conditions, the helicopter rolled on its side.
- The aircraft struck ice in nearly flat attitude in whiteout conditions...
- The 206 pilot took off on a charter with two passengers for some survey work. The weather was marginal but there were no weather reporting stations in the area, so they decided to "have a look at it." When they turned out over the sea ice to look for some fuel barrels, the pilot soon found himself in whiteout. He asked a passenger to keep an eye on the altitude while he turned the 206 to regain visual reference with the shoreline. In the turn he lost altitude and the helicopter struck the ice.
This accident resulted in three serious injuries. One has to wonder about what was going through the pilot’s mind when he asked the passenger to "keep an eye on the altitude." -Ed.
- The ceiling was low and the visibility was poor, in falling snow, but the 206 pilot spotted his party on the lake. Day-Glo cloth markers indicated their location. The ice was covered with four inches of fresh loose snow. As the helicopter entered a pre-landing hover, the rotor wash blew up the loose snow and the pilot became disoriented. The machine rolled and the main rotor blades struck the ice.
- The 206 was number two in a group of six helicopters en route from Charlottetown, P.E.I., to an ice flow in the Gulf of St. Lawrence to observe the seal-hunting operation. As the group approached the halfway point, they encountered whiteout conditions in light-to-moderate snow. The ice they were flying over was relatively flat and also featureless. The accident helicopter reduced speed to about 60 kt and descended in an attempt to maintain visual contact with the ice. As the helicopter neared the ice, number-three aircraft radioed a warning to pull up, but the warning came too late. The 206 hit the ice with sufficient force to tear the float gear off and crush the crew and passenger seats.
- The pilot landed in a mountain meadow to pick up skiers. As the helicopter did not come out of the whiteout as expected on takeoff, the pilot aborted. The right skid dug in and the machine rolled over.
Sadly, there are many more examples; they happen every year. What may surprise you is that many of them happen in the summer months, when Mother Nature has't yet released her grip on winter in our northern regions. One study found that in the preceding nine years, 25 percent of the whiteout accidents took place during the summer operational season. This may indicate that currency plays a role in both the hands-on skills and decision making required to deal with winter weather.
The vast majority of low-speed take-off and landing accidents are preventable by good decision making, with careful consideration given to:
- the conditions of the area;
- the recent weather, wind, temperature (is the snow heavy, or light and fluffy?);
- patience; and
- technique(see "Snow Landing and Take-off Techniques" in Aviation Safety Vortex 1/2003).
In the en route phase of flight, many human factors gurus and experienced pilots theorize that the stage is set for the accident long before the whiteout condition exists. They believe that if you start the trip with the mindset that you'll return or divert if the weather deteriorates beyond a given point, you are more likely to do so when it does. Conversely, if you have nothing but the destination or an optimistic forecast in mind, you're more likely to press on. This is definitely something to consider when planning your next flight into the frozen Canadian winter.