|Title:||Low-altitude microburst encounter, McDonnell Douglas DC-9-82, April 26, 1993|
|Micro summary:||This McDonnell Douglas DC-9-82 encountered a microburst at low altitude, causing substantial damage to the airplane.|
|Event Time:||1993-04-26 at 1722 MDT|
|Publishing Agency:||National Transportation Safety Board (NTSB)|
|Site of event:||Denver, CO|
|Departure:||Salt Lake City International Airport, Salt Lake City, Utah, USA|
|Destination:||Denver International Airport, Denver, Colorado, USA|
|Airplane Type(s):||McDonnell Douglas DC-9-82 (MD-82)|
|Type of flight:||Revenue|
NTSB short summary:
An inflight encounter with a microburst at an altitude insufficient to effect recovery.
While on final approach, at approximately 100 feet agl, the aircraft experienced a significant loss of indicated airspeed and encountered a high sink rate which terminated in a hard landing. The lower aft body of the aircraft in the area of the tail skid was crushed inward causing structural damage. At 47 feet above touchdown and 126 knots the airplane began to rotate and descended to 3 feet above touchdown, with an airspeed of 109 knots, in 3 seconds. Touchdown occurred with a nose up attitude of 8.334 Degrees with a vertical acceleration of 2.246 G. Touchdown occurred at 110 knots with full power being developed. The llwas did not activate. NCAR researchers reported that a localized microburst could occur without activating the LLWAS.
NTSB factual narrative text:
HISTORY OF FLIGHT
On Monday, April 26, 1993, at 1722 mountain daylight time, a McDonnell Douglas DC-9-82, N14816, operating as Continental Airlines Flight 182, incurred damage to the lower aft body on landing at Stapleton International Airport, Denver, Colorado. The two pilots, four flight attendants, and 84 passengers were not injured; however, the aircraft sustained substantial damage. The aircraft was being operated under 14 CFR Part 121 when the accident occurred. Visual meteorological conditions prevailed and an IFR flight plan was filed. The flight originated in Salt Lake City, Utah, at 1616.
Details of flight crew qualifications and experience is depicted in this document and attached crew supplement. The captain on this flight was the model manager for the DC-9 fleet and was a qualified check airman in the aircraft.
Recorded Stapleton International Airport weather at the time of the accident is attached and provides information that the airport weather at the time of the accident was visual meteorological conditions and that the recorded surface wind was from the northeast at 8 knots. The remarks section indicated that cumulonimbus clouds and virga were present in all quadrants and was moving to the northeast.
The attached witness statement submitted by the captain of Continental Flight 1284, which was conducting a visual approach to runway 26L at 1720, describes what that crew experienced. A rapid gain in indicated airspeed was followed by a loss. Based on that experience, the activation of the on board wind alert system, and after witnessing the landing of the accident aircraft, they performed a go-around. The captain stated that virga was present in all quadrants and they encountered gusting conditions during the approach.
A review of the low level wind shear alert system (LLWAS) was conducted. The recording tapes of that system did not indicate any activation of the system during the time period when the accident occurred.
Interviews were conducted with personnel from the National Center for Atmospheric Research (NCAR), located in Boulder, Colorado. The researchers indicated that it was possible for a localized microburst to occur, which would not trigger the LLWAS system.
Stapleton International Airport is served by an advanced LLWAS system which was determined to be fully operational at the time of the accident.
The accident aircraft and the aircraft which conducted a go around, as discussed above, were conducting visual approaches to runways 26R and 26L respectively. These runways are parallel and are 900 feet apart centerline to centerline.
The flight data recorder and voice recorder were removed from the accident aircraft and sent to the National Transportation Safety Board Laboratory in Washington, D.C. The reports from the recorders are attached.
WRECKAGE AND IMPACT INFORMATION
Flight recorder data indicated that at 47 feet above touchdown, the aircraft began to rotate and descended to 3 feet above touchdown in three seconds. Touchdown occurred with a nose up attitude of 8.334 degrees with a vertical acceleration of 2.246 Gs. At 47 feet, the indicated airspeed was 126 knots and decreased to 109 knots in 2 seconds. Touchdown occurred at 110 knots with full power being developed.
Tower personnel witnessed the touchdown and related that sparks and smoke emitted from the aircraft. This was reported to the crew.
The captain's statement is quoted as follows:
"Final approach was smooth and final landing configuration was established at approximately 1000 ft. AGL, with landing flaps at 40 degrees and a target speed of Vref plus 10 kts. on VASI. At approximately 200 ft. AGL a slight increase in airspeed was noted - to approximately Vref plus 15kts. - throttles were left at 1.25 EPR. The flight continued to an altitude of 100 ft. AGL - then experienced a rapid loss of airspeed (estimated to be greater than 25 kts.) and a large sink rate developed immediately. The throttles were advanced to mechanical stops and pitch attitude was increased to arrest sink rate, which appeared to increase until the aircraft touched down firmly on the runway. The control tower advised us that smoke and sparks were observed on touch down - First officer Gordon advised the tower of the airspeed loss. During the landing roll out we heard a number of pilots reporting large airspeed fluctuations on short final, and one or more missed approaches. The landing roll out and taxi to the gate were normal and uneventful."
Inspection of the aircraft revealed general crushing of the skin and structure on the lower aft body in the area of the tail skid. Longitudinal scarring and scrapping were present on the skin surface.
The wreckage was verbally released to Continental Airlines maintenance personnel the day of the accident following inspection. The flight data recorder and cockpit voice recorder were released after they were examined.
|Learning Keywords:||Operations - Hard Landing|
|Operations - Windshear or Microburst|
|Close match:||Hard landing in windshear, Boeing 747-436, G-BNLD, 11 October 1997|
|Hard landing, Boeing 727-2P1, VP-CZY, Luton, October 30, 2001|
|Hard landing, Boeing 767-300, I-DEIL, May 22, 1997|
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