Eurocopter Deutschland GMBH MBB-BK 117 C-1 accident near Fort Washington, Pennsylvania, May 19, 2025
On May 19, 2025 at about 11:41 pm local time, a 1997 Eurocopter Deutschland GMBH MBB-BK 117 C-1 (helicopter), registered N117NC, was substantially damaged in an accident during enroute (cruise) near Fort Washington, Pennsylvania (Wings Field Airport). It was a business flight under charter and air-taxi rules (Part 135). 3 people had minor injuries. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
Maintenance personnel’s failure to identify and replace damaged rivet nuts at the air conditioning louver assembly, which resulted in the separation of the louver assembly from the helicopter, the louver assembly’s impact with the tail rotor, and subsequent loss of helicopter control.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 19, 2025 · about 11:41 pm local time
- Place
- Fort Washington, Pennsylvania · Wings Field Airport · map
- Type
- Accident
- Injuries
- 3 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Eurocopter Deutschland GMBH MBB-BK 117 C-1, built 1997
- Registration
- N117NC · registry record · serial 7517
- Damage
- Substantial damage
- Flight
- Business flight · charter and air-taxi rules (Part 135)
The NTSB's narrative final · quoted from the NTSB record
The helicopter was returning to its home base following a patient transport mission when it became uncontrollable and began shuddering violently. The pilot experienced a total loss of tail rotor control with no warning. He performed an autorotation, and the helicopter came to rest on a residential lawn. Postaccident examination of the helicopter revealed that the air conditioning louver assembly, tail rotor gearbox, and tail rotor assembly had separated in flight. A recovered louver fragment exhibited contact damage from a tail rotor blade, and both tail rotor blades were destroyed. Examination of the louver’s forward attachment points revealed stripped rivet nuts and evidence of a prior repair; bolts for fastening the louver assembly to the rivet nuts were found within the airframe. Maintenance records indicated that the louver assembly had been removed and reinstalled about 16 flight hours before the accident. Based on the evidence, the rivet nuts for the air conditioning louver assembly were likely stripped during maintenance, resulting in the louver assembly separating from the helicopter in flight and impacting the tail rotor. The tail rotor assembly then separated from the helicopter, which led to a loss of control.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Part(s) separation from AC during enroute (cruise) defining event
- Loss of tail rotor effectiveness during emergency descent
- Autorotation Collision with terrain or object (not controlled flight into terrain)
- Aircraft maintenance event during prior to flight
The NTSB's findings
- Personnel issues › Task performance › Maintenance › Repair › Maintenance personnel
- Personnel issues › Action/decision › Action › Incorrect action performance › Maintenance personnel
Pilot
- Certificate: commercial pilot
- Ratings: instructor: helicopter; instructor: instrument helicopter; instrument: helicopter; rotorcraft: helicopter
- Flight time: 2,951 hours in all; 73 in this make and model; 41 in the last 90 days; 13 in the last 30 days; 2,551 as pilot in command; 800 on instruments
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: rgt
- Injury: minor injuries
Passenger
- Seat: left
- Injury: minor injuries
Passenger
- Seat: rgt
- Injury: minor injuries
The aircraft
- Airframe total time: 9,731.6 hours
- Last inspection: approved inspection programme, April 25, 2025; 24 hours since
- Maximum gross weight: 7,385 lb
- Seats: 6
- Landing gear: fixed
- Engine 1: Turbomeca Arriel 1 (turboshaft); 5,872 hours total
- Engine 2: Turbomeca Arriel 1 (turboshaft); 5,158 hours total
- Operator: Triple M Leasing LLC
The flight
- Departed from: PA39 Philadelphia PA at 11:33 pm
- Destination: LOM Philadelphia PA
Weather at the time
- Light: daylight
- Wind: from 300° at 7 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 64°F (18°C), dew point 48°F (9°C)
- Altimeter: 29.85 inHg
- Observation at 7:55 pm from KLOM, 1 miles away
Weather report (METAR): KLOM 192355Z AUTO 30007KT 270V330 10SM CLR 18/09 A2985 RMK AO2 T01830086 10203 20182 402070147
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 2 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
9 documents, released by the NTSB on August 19, 2026. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 10 pages | View Download |
| 2 | Pilot's Statement | PDF, 1 page | View Download |
| 3 | Memorandum for Record - FAA Inspector Statement | PDF, 1 page | View Download |
| 4 | Mor Airbus Examination Notes | PDF, 2 pages | View Download |
| 5 | Maintenance Record Excerpts | PDF, 8 pages | View Download |
| 6 | Maintenance Inspection Logs | PDF, 4 pages | View Download |
| 7 | Mor 14 CFR A� 43.13(A) A�� General Performance Rules | PDF, 1 page | View Download |
| 8 | Investigative Photos | PDF, 8 pages | View Download |
| 9 | Statement of Party Representatives to NTSB Investigation | PDF, 9 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number ERA25LA204.