Stacking the Odds in the Mountains
The MU 300 Diamond touched down in the first thousand feet of the bare and dry 4500 ft. Jasper Hinton runway. The captain applied maximum braking, but he quickly realized that he would not be able to stop on the runway remaining. He initiated a series of "S" turns, believing that, by increasing the distance travelled, he would improve his chances of stopping before running off the pavement. He could not.
The aircraft skidded to a stop 225 ft. off the end, with the left main and nose gears collapsed. Numerous wrinkles in the fuselage skin and structure indicated serious airframe damage. Jet fuel leaked into the ground from the ruptured left wing tank (TSB Report A95W0034). Thankfully, fire did not break out, and the four on board walked away uninjured.
Both pilots had flown into Jasper Hinton before. So how did this experienced crew stack the odds so high against a successful landing?
At the pre-flight planning stage, the crew might have noted that there are no readily available weather observations for the Jasper Hinton aerodrome. (There are automated observations recorded at Jasper Hinton, stored and forwarded twice daily to Environment Canada. Human observations have since ceased at Jasper, also replaced by an autostation. Neither of these autostations meet aviation standards. There is an Automated Weather Observation System (AWOS) in Edson, 45 mi. east of Jasper Hinton. Since 1991, these observations have been available on normal weather information circuits and were available to ATS. They are not available by local voice generator module.)
At the time, the nearest official weather observations were taken at the Jasper townsite, 7 NM from the Jasper airstrip, and 30 NM from the Jasper Hinton aerodrome and separated from it by 8000 ft. mountains. When the FSS briefer gave them the "Jasper" weather, the crew members assumed that they were getting Jasper Hinton information and the specialist was merely abbreviating the name. They made the same assumption later when the Edmonton Centre controller passed them the latest "Jasper" weather before clearing them for descent. The regulations require ATS to give pilots the nearest official weather and altimeter setting.
Potential name confusion is not unique to these two aerodromes. There are numerous opportunities across Canada to duplicate the mistake: Moose Jaw/Moose Jaw Muni; Edmonton Intl/Edmonton Muni; Cold Lake/Cold Lake Regional; Gods Lake/Gods Lake Narrows; and La Grande 3/La Grande 4, just to name a few. So if you are aiming for Gods Lake and are told that "Gods Lake Weather is...," beware: Gods Lake does not report weather. Gods Lake Narrows does, but it's 30 NM to the west of your destination.
While the weather was basically clear at both sites, the winds at Jasper were calm, while the winds at Jasper Hinton, on the other side of the mountain range, were out of the southwest at 14 kt., gusting to 21 kt.
Subsidence of the air coming out of the mountains and the funnelling effect of the valley to the west of the airport both mean that the Jasper Hinton winds are generally stronger. Because of the unpredictable variable winds, Jasper Hinton has three windsocks serving the one runway: one at each end, and a lighted sock at centre field.
It is not unusual for winds and weather in the mountains to vary widely over short distances.
Previous experience (both pilots had been there before) and a pre departure review of aerodrome information should have reminded the crew that, except for the first 400 ft., Runway 02 has a distinct downslope.
Arriving at Jasper Hinton, the crew did not follow the procedures recommended for uncontrolled aerodromes. Those procedures suggest that a pilot should overfly the aerodrome prior to landing to determine wind and verify that the runway is unobstructed.
Believing that the winds were calm, and with 25 mi. visibility, the pilots did not feel that a visual inspection was needed. They proceeded with a straight in approach for landing on Runway 02.
On approach, the captain decided to add 10 kt. to the reference speed (Vref) to compensate for subsiding air, turbulence and airspeed fluctuations. (All of these factors should have alerted the crew to strong winds. Observing smoke, trees and water during their descent would also have warned them of the wind's strength and direction.)
On short final, the crew observed the windsock extended parallel to the ground and varying in direction. What they failed to take in was that it was not varying off the nose, but straight up the tailpipe.
So here's how the odds stacked up:
- inadequate preflight planning;
- winds and weather for a site 30 mi. away, on the other side of a high mountain ridge;
- a lack of appreciation of mountain weather;
- unclear preflight briefing and en route radio communications;
- disregard for recommended practices;
- failure to use the clues the strong winds were giving;
- observation of, but failure to see, the windsock; and
- a landing downwind, downslope, at 10 kt. above Vref.
A last second rejected landing might have saved the day, but, with those odds, the result was almost a sure bet.
Originally Published: 2/1997
Original Article: Stacking the Odds in the Mountains