# NTSB IAD04CA015: Waco ASO, N11253, Lexington, KY, April 9, 2004

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Data collection · Final report
- Date: April 9, 2004, 19:23 local (23:23 UTC)
- Place: Lexington, KY
- Coordinates: 38.036945, -84.605278
- Nearby events: https://openairdocs.org/map.md?lat=38.0369&lon=-84.6053&mi=10
- Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report June 28, 2006
- Report: Approved by Office Director
- NTSB case key (mKey): 59364
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=IAD04CA015
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/59364/pdf
- Page: https://openairdocs.org/ntsb/IAD04CA015

## Probable cause

The pilot's inadequate remedial action to wake turbulence.  A factor was the pilot's failure to recognize that the takeoff conditions were conducive to wake turbulence.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Vortex turbulence encountered, takeoff - roll/run
  - remedial action - inadequate, pilot in command (cause)
  - wake turbulence - not recognized, pilot in command (contributing factor)
- Nose over, takeoff - roll/run

## Analysis

The pilot initiated his takeoff roll from a runway position where a transport airplane had previously touched down.  When the pilot began the takeoff roll, the transport airplane had just cleared the runway.  During the takeoff roll, airplane's tail elevation was normal until it "spontaneously" went higher.  The pilot lowered the tail; however, it again went higher, and the propeller hit the runway.  The pilot again tried to lower the tail, but it went higher still, with a "heavier contact of the propeller," and the airplane then nosed over.  The pilot also noted that there "seemed to be some lateral turbulence during the takeoff."  At the time of the accident, there was a 3-knot, quartering tailwind.  According to FAA Advisory Circular 90-23F, "Aircraft Wake Turbulence," a light quartering tailwind "requires maximum caution."  In addition, "Whether or not a warning or information has been given, the pilot is expected to adjust aircraft operations and flight path as necessary to preclude serious wake encounters."

## Factual narrative

On April 9, 2004, at 1923 eastern daylight time, a Waco ASO, N11253, was substantially damaged during takeoff at Lexington-Bluegrass Airport (LEX), Lexington, Kentucky.  The certificated private pilot was not injured.  Visual meteorological conditions prevailed, and no flight plan had been filed for local personal flight, conducted under 14 CFR Part 91.

The pilot reported that he had initiated the takeoff roll from a position on the runway where an MD-80 had previously touched down.  When the pilot began the takeoff roll, the airplane's tail elevation was normal until it "spontaneously" went higher.  The pilot lowered the tail; however, it again went higher, and the propeller hit the runway.  The pilot again tried to lower the tail, but it went higher still, with a "heavier contact of the propeller," and the airplane then nosed over.  The pilot also noted that, "there seemed to be some lateral turbulence during the takeoff."

According to a Federal Aviation Administration (FAA) inspector, the pilot initiated the takeoff attempt on runway 22, at intersection C.  The airplane rolled approximately 200 feet, then nosed over.  Two additional FAA inspectors confirmed that the accident airplane entered the runway just after an MD-80 had landed, and when the pilot began his takeoff roll, the MD-80 had just taxied clear of the runway.  Runway 22 was 7,003 feet long and 150 wide, and intersection C was about 1,500 feet from the approach end.  Winds recorded at the airport, about 15 minutes before the accident, were from 020 degrees true at 3 knots.

According to FAA Advisory Circular 90-23F, "Aircraft Wake Turbulence,"  wing vortex circulation "is outward, upward and around the wing tips," and "vortices from larger (transport category) aircraft sink at a rate of several hundred feet per minute, slowing their descent and diminishing in strength with time and distance behind the generating aircraft."  In addition, "when vortices of larger aircraft sink close to the ground (within 100 to 200 feet) they tend to move over laterally over the ground at a speed of 2 to 3 knots."

The advisory circular also noted that, "a tailwind condition can move the vortices of the preceding aircraft forward into the touchdown zone," and that, "the light quartering tailwind requires maximum caution."   It also stated that pilots should be "particularly alert" in conditions where vortices could remain in a touchdown area, and in capital letters stated, "WHETHER OR NOT A WARNING OR INFORMATION HAS BEEN GIVEN, THE PILOT IS EXPECTED TO ADJUST AIRCRAFT OPERATIONS AND FLIGHT PATH AS NECESSARY TO PRECLUDE SERIOUS WAKE ENCOUNTERS."

## Aircraft

- Registration: [N11253](https://openairdocs.org/aircraft/N11253), registered now, S/N 3212, built 1931 (OpenAirDocs)
- Reported make and model: Waco ASO
- Registry model: [Waco ASO](https://openairdocs.org/model/waco-aso) (registry code 9601202) (OpenAirDocs)
- Registry engine: [Continental W670 series](https://openairdocs.org/engine/continental-w670-series) (registry code 17018, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 3212
- Airframe hours: 4407
- Engines: Continental W670-6N 220 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, June 4, 2003, 21 hours before
- Departed: LEX, Lexington, KY
- Destination: Lexington, KY
- Airport: LEX, Blue Grass Airport, runway 22, 7,003 × 150 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 77; injuries: none; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; last flight review October 21, 2002; seat: front; flight hours: 3,526 total, 1,051 in this make and model, 7 in the last 90 days, 3 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 20° at 3 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 61 °F, dew point 45 °F
- Altimeter: 29.96 inHg
- Observed at: LEX

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 20040409005189A](https://openairdocs.org/incident/20040409005189A), Apr 9, 2004: Waco ASO, Lexington, KY, Substantial damage. (-23) Apparent wake turbulence. Subject a/c took off shortly after an MD-80 series landed. The pilot believes wake turbulence was the cause of the accident.

## Other investigations on N11253 (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB IAD79FLQ03](https://openairdocs.org/ntsb/IAD79FLQ03), Oct 29, 1978: Waco ASO (N11253), Mt Sterling, KY, substantial damage

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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