# NTSB NYC99LA050: Douglas DC-9, N300ME, Plainfield, PA, January 15, 1999 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: January 15, 1999, 11:20 local (16:20 UTC) - Place: Plainfield, PA - Coordinates: 40.200008, -77.280303 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.2000&lon=-77.2803&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 1 serious, 59 uninjured - Status: Completed, report April 25, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 45670 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC99LA050 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/45670/pdf - Page: https://openairdocs.org/ntsb/NYC99LA050 ## Probable cause The wake turbulence from the proceeding Boeing 747. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Vortex turbulence encountered, descent - normal - wake turbulence - encountered (cause) ## Analysis The DC-9 departed and climbed to flight level 290. About 1 hour and 35 minutes after departure, the airplane was cleared by ATC to 17,000 feet msl. Upon receiving the clearance, the captain initiated approximately a 3,500 foot per minute descent, and slowed to 280 knots. While in the descent and passing flight level 235, the airplane encountered the wake turbulence of a cargo Boeing 747, which was 12 nautical miles ahead and also descending to 17,000 feet msl. The captain of the DC-9 pitched the airplane's nose up to exit the wake turbulence, and requested additional separation between the two airplanes from ATC. During the wake turbulence encounter, a flight attendant in the galley slipped, and seriously injured her right ankle. ## Factual narrative On January 15, 1999, about 1120, eastern standard time, a Douglas DC-9, N300ME, operated by Midwest Express Airlines as flight 150, encountered wake turbulence while descending through flight level 235 over Plainfield, Pennsylvania. The airplane was not damaged. Two flight crewmembers, 2 flight attendants, and 55 passengers were not injured. A third flight attendant sustained a serious injury to her right ankle. Visual meteorological conditions prevailed, and an instrument flight rules flight plan had been filed for the scheduled passenger flight that departed General Mitchell International Airport (MKE), Milwaukee, Wisconsin, destined for Philadelphia International Airport, Philadelphia, Pennsylvania. The flight was conducted under 14 CFR Part 121. The captain stated that they departed MKE at 1010, and climbed to flight level 290. About 1 hour and 35 minutes after departure, he was cleared by air traffic control (ATC) to 17,000 feet msl. Upon receiving the clearance, he briefed the first officer he would to stay above a proceeding Boeing 747 descent path. The Boeing 747 was 12 nautical miles ahead and also descending to 17,000 feet MSL. The captain then initiated approximately a 3,500 foot per minute descent and slowed to 280 knots. While in the descent and passing flight level 235, the airplane encountered a "moderate jolt" which the captain assumed was from the Boeing 747. The captain pitched the airplane's nose up to exit the turbulence, and requested additional separation between the two airplanes from ATC. The flight continued to its schedule destination without further incident. During the wake turbulence encounter, a flight attendant in the galley slipped and seriously injured her right ankle. A passenger, who was also a registered nurse, applied ice, and splinted the injured ankle. The flight attendant was then seated in the aft jump-seat for landing. Radar data revealed that the accident airplane was about 2 minutes in trail, 1,000 feet below, and 3 miles to the north of the Boeing 747. Radiosonde data recorded about 23,000 feet over Pittsburgh, Pennsylvania, at 0700, showed the winds were 195 degrees at 90 knots. According to the 1998, Aeronautical Information Manual (AIM), "Flight tests have shown that the 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." ## Aircraft - Registration: N300ME (not matched to a registry record) - Reported make and model: Douglas DC-9 - Category: Airplane - Serial number: 45718 - Airframe hours: 65241 - Engines: P&W JT8D-7B 14000 lbs thrust turbo fan - Damage: No damage - Flight: Part 121 - Registered owner: Midwest Express Airlines - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, January 13, 1999, 15 hours before - Departed: MKE, MILWAUKEE, WI - Destination: PHL, PHILADELPHIA, PA - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 39; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 10,039 total, 3,367 in this make and model, 3,816 as pilot in command, 136 in the last 90 days, 78 in the last 30 days, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 240° at 9 knots - Visibility: 4 statute miles - Lowest ceiling: 2,500 ft broken - Temperature: 16 °F, dew point 12 °F - Altimeter: 30.00 inHg - Observed at: PIT, 130 nm away ## 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 19990115041929A](https://openairdocs.org/incident/19990115041929A), Jan 15, 1999: Doug DC915, Plainfield, PA. (.4)The DC-9 departed and climbed to flight level 290. About 1 hour and 35 minutes after departure, the airplane was cleared by ATC to 17,000 feet MSL. Upon… 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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.