Boeing 737-522 N905UA

Summary

On 24 April 1993 at about 02:20 local time, a Boeing 737-522 registered N905UA was involved in an incident near Denver, Colorado, United States. 133 people were on board and nobody was injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

24 April 1993 at 02:20

Classification

Incident

Location

Denver, Colorado, United States

Nearest airport

Stapleton International (DEN)

Coordinates

39.7598, -104.9193

Aircraft

Boeing 737-522

Registration

N905UA

Category

Airplane

Engines

2

Operator

Not recorded

Operating rule

Part 121: Air Carrier

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

San Antonio → Unknown

Aircraft damage

Not recorded

Weather

VMC

Light

Dusk

NTSB number

DEN93IA044

Nobody was injured.

THE PILOT-IN-COMMAND'S FAILURE TO MAINTAIN ADEQUATE SEPARATION FROM THE BOEING 757, AND HIS FAILURE TO STAY ABOVE THE PROBABLE PATH OF THE BOEING'S WAKE VORTICES, WHICH RESULTED IN THE VORTEX ENCOUNTER. FACTORS RELATED TO THE ACCIDENT WERE: THE CROSSWIND, AND AN INADEQUACY IN ATC PROCEDURES CONCERNING VISUAL APPROACHES OF AIRCRAFT, BEHIND AND DOWNWIND FROM APPROACHES OF HEAVIER AIRCRAFT TO PARALLEL OR ADJACENT RUNWAYS.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

ON A VISUAL APPROACH TO RUNWAY 26L, UNITED FLIGHT 409, A BOEING 737, EXPERIENCED AN UNCOMMANDED ROLL OF ABOUT 23 DEG AT AN ALTITUDE OF 882' AGL. THE CREW WAS ABLE TO CORRECT THE ROLL & MADE A GO-AROUND TO AN UNEVENTFUL SECOND APPROACH & LANDING. THE BOEING 737 WAS FOLLOWING A BOEING 757, WHICH WAS ON A VISUAL APPROACH TO RUNWAY 26R. THE TWO RUNWAYS WERE 900' APART FROM CENTERLINE TO CENTERLINE & THE THRESHOLD OF 26L WAS OFFSET ABOUT 1300' EAST OF 26R. ACCORDING TO DATA FROM THE FLIGHT RECORDER, THE WIND AT THE ONSET OF THE INCIDENT WAS FROM THE NORTHWEST AT 5 TO 10 KNOTS. THE SURFACE WIND WAS FROM 360 DEGREES AT 10 KNOTS. THE TWO AIRCRAFT WERE 1.32 NAUTICAL MILES APART IN AN OFFSET TRAIL POSITION. BOTH AIRCRAFT WERE ON 3 DEG GLIDE SLOPES. THE WAKE VORTICES HAD SETTLED ABOUT 100' & MOVED LATERALLY TOWARD THE GLIDE PATH OF 26L. WEATHER DATA SHOWED EVIDENCE OF POSSIBLE INTERACTION BETWEEN WAKE TURBULENCE FROM THE 757 & AN OUTFLOW BOUNDRY, WHICH WAS MOVING THROUGH THE AREA.

Quoted verbatim from the NTSB record.