# NTSB FTW04LA069: MBB BK 117 B-2, N440HH, Conroe, TX, November 29, 2003 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: November 29, 2003, 02:50 local (08:50 UTC) - Place: Conroe, TX - Coordinates: 30.391666, -95.32833 - Nearby events: https://openairdocs.org/map.md?lat=30.3917&lon=-95.3283&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report June 2, 2004 - Report: Approved by Office Director - Parties: Federal Aviation Administration SW09 - NTSB case key (mKey): 58697 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW04LA069 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/58697/pdf - Page: https://openairdocs.org/ntsb/FTW04LA069 ## Probable cause The pilot's failure to maintain clearance from trees while repositioning in a confined landing zone. Contributing factors were the dark night light conditions and the confined area available to the pilot. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight collision with object, hover - terrain condition - congested/confined area (cause) - object - tree(s) - clearance - not maintained, pilot in command (cause) - light condition - dark night (contributing factor) ## Analysis While maneuvering in dark night conditions in a confined landing zone, the air ambulance helicopter's tail rotor blades struck a tree. After impacting the tree, the pilot felt no vibration in the anti-torque pedals or airframe and landed safely. After landing, the pilot elected to not shut down the aircraft, inspected the tail rotor, and returned to the hospital. While at the hospital he inspected the tail rotor again, with the assistance of the company mechanic on duty, and they decided that the aircraft was airworthy. While performing a preflight inspection on the following day, another pilot discovered the damage on the tail rotor blades. The tail rotor blades were then removed and replaced. ## Factual narrative On November 29, 2003, approximately 0250 central standard time, a MBB BK 117 B-2 twin-engine helicopter, N440HH, sustained substantial damage when the tail rotor blades impacted trees while maneuvering near Conroe, Texas. The commercial pilot, flight paramedic, and flight nurse were not injured. The helicopter was registered to and operated by Memorial Hermann Hospital System, Inc., of Houston, Texas. Dark night visual meteorological conditions prevailed, and company flight plan was filed for the 14 Code of Federal Regulations Part 91 positioning flight. The air ambulance flight departed the David Wayne Hooks Memorial Airport, near Houston, Texas, at 0236. According to the pilot's statement, prior to landing, he performed a "high recon" of the landing zone (LZ). The LZ was marked by four lighted traffic cones, and the wind was from the north. After the on-board medical crew cleared the helicopter from obstacles on the left and right side, the pilot terminated the approach at 200 feet agl. The helicopter was then flown vertically down to the LZ, and at approximately 3-5 feet agl, the pilot initiated a180-degree left pedal turn. Approximately 95-120 degrees into the turn, the pilot heard "what sounded like the rotor's hitting leaves and [tree] limbs." The pilot felt no abnormal vibration with the anti-torque pedals or the helicopter and completed the turn. After landing, the pilot elected not to shut down the helicopter, and inspected the tail rotor. The pilot stated, "Based on the lack of vibration in [the] pedals and airframe, the decision was made not to shut [the aircraft] down and continue the flight back to [the] hospital." Upon returning to the hospital, the 6,346-hour pilot initiated a post-flight inspection, "paying close attention to the tail rotor." The pilot noted no signs of scratches, dents, or any other types of abnormalities, with the exception of two "small" areas where paint was chipped off. The pilot then contacted the company mechanic on duty, discussed the airworthiness of the aircraft, and "the decision was made, mutually, that the aircraft was airworthy." The flight crew then returned the helicopter to another company facility. While performing a preflight inspection on the following day, another pilot discovered the damage on the tail rotor blades. He then grounded the aircraft and awaited the arrival of a company mechanic. The pilot reported to operation safety officials that he saw "ripples" in the tail rotor blades paint. On February 3, 2004, an FAA inspector reported to the NTSB investigator-in-charge that due to the damage sustained, both tail rotor blades were removed and replaced. ## Aircraft - Registration: N440HH (not matched to a registry record) - Reported make and model: MBB BK 117 B-2 - Category: Helicopter - Serial number: 7238 - Airframe hours: 6438.9 - Engines: Lycoming LTS101-750-B1 700 horsepower turbo shaft - Damage: Substantial damage - Flight: Positioning, Part 91 - Registered owner: Memorial Hermann Hospital System, Inc. - Airworthiness certificate: Special, Limited (Special); Standard, Normal - Last inspection: AAIP, December 1, 2003, 5.4 hours before - Departed: DWH, Houston, TX - Destination: Conroe, TX - Flight plan: Company VFR - Airport: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 55; injuries: none; commercial; instrument ratings: helicopter; medical: class 2, valid medical--w/ waivers/lim; last flight review March 27, 2003; seat: right; flight hours: 6,346 total, 3,170 in this make and model, 6,146 as pilot in command, 77 in the last 90 days, 17 in the last 30 days, 36 in the last 24 hours ## Weather - Conditions: Visual (VMC), Night/dark - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 30 °F, dew point 30 °F - Altimeter: 30.45 inHg - Observed at: CXO, 5 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 20031129034419A](https://openairdocs.org/incident/20031129034419A), Nov 29, 2003: Bolkms BK117B2, Houston, TX, Substantial damage. (-23) Local medical evacuation flight was dispatched to unprepared remote landing site for pick up of a patient. Obstructing tall trees bounded the landing… 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.