19th of July 2019, Nose down input, Blog #749

Seven years ago on this date, with a crew of four and 74 passengers, a de Havilland Canada DHC-8-402Q (Dash 8) was operating a domestic passenger flight in Canada between Fort McMurray Airport and Edmonton International Airport. The flight was conducted under instrument flight rules (IFR), and the estimated flight duration according to the flight plan was 1 hour and 2 minutes.

After cruising at flight level 240 (24,000 feet on a standard barometer setting of 29.92 inHg or 1013.2 mb) and descending towards Edmonton, the aircraft was cleared for a visual approach to runway 12. The pilot flying (PF) had briefed a flap 15 landing with an approach speed (Vref) of 122 knots. An alternative missed approach procedure was also briefed and approved by ATC due to thunderstorm activity.

The wrinkled right-hand nose section of the aircraft. Blue dry-erase marker has been added for clarity by investigators. (Source & © TSB Canada)

During the approach, Vref was increased by 20 knots in anticipation of a missed approach, as thunderstorms and possible wind shear conditions existed. Thirteen minutes prior to the aircraft's arrival, the following weather conditions were recorded:

• Wind: 220° at 8 knots, gusting to 15 knots

• Visibility: 15 miles in light thunderstorms and rain

• Broken cumulonimbus at 3,000 feet AGL and broken clouds at 8,300 feet

• Temperature: 16°C

• Dew point: 13°C

• Altimeter: 29.78 inHg

The landing was expected to be firm due to the anticipated gusty conditions close to the ground. Three miles from the runway, the flaps were set to 15° and the landing gear was lowered. The airspeed was Vref + 20, or 142 knots.

CCTV image of runway 12 with the incident aircraft on short final, indicated by the green arrow. (Source: TSB Canada © Edmonton Airport Authority)

At 17:13 local time, the aircraft touched down on the main landing gear in the touchdown zone of runway 12. The airspeed at touchdown was 142 knots. The aircraft bounced and became airborne again. The PF then made a full nose-down elevator input. A bang and a nose-wheel shimmy followed, and the aircraft pulled to the left during the landing roll.

After landing, the crew checked the aircraft's Integrated Communication and Application System for a hard-landing indication; no such indication was noted. The aircraft taxied clear of the runway and requested maintenance assistance, as the crew was concerned that the aircraft had been damaged during the landing.

Both nose landing gear wheels were replaced, and the aircraft taxied to its parking position, where the passengers disembarked. There were no injuries.

There was extensive damage to the nose section of the aircraft:

• Wrinkled fuselage skin

• Damaged left nose landing gear door

• Damaged nose landing gear

• Damaged forward pressure bulkhead

The aircraft was repaired and returned to service.

The accident was investigated by the Transportation Safety Board of Canada (TSB). No ICAO Annex 13 probable cause statement was issued in the final report, which is available below this blog The report however provides a little insight in the possible cause.

Given the gusty wind conditions on approach, normal procedures in the WestJet Encore Aircraft Operating Manual called for a target speed of VREF +5 knots, plus half of the gust of 15 knots, or a total of VREF +13 knots. Procedures also called for this speed to be reduced once over the threshold to achieve VREF at touchdown. However, the flight crew planned and flew the approach at VREF +20 knots. The airspeed was not reduced as the aircraft approached the runway threshold and the aircraft touched down at this airspeed.

In this occurrence, the aircraft’s speed was not reduced from its approach speed (VREF + 20 KIAS) to the touchdown speed (VREF). The nose of the aircraft was lowered at a higher rate than normal, resulting in damage to the aircraft. These highlight the importance of flight crews adhering to operational procedures and techniques.

Dash 8 Hard landing Edmonton.pdf

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