NTSB Factual Report

HISTORY OF FLIGHT

On November 19, 1993, at 0346 central standard time, a Hughes 369HS, N9179F, operated as a public use aircraft by the Drug Enforcement Administration (DEA), impacted trees and terrain while on a training mission near Antonia, Missouri. The pilot sustained serious injuries and the passenger (observer) received fatal injuries. The helicopter sustained substantial damage. The 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The local flight departed Spirit of St. Louis Airport, at St. Louis, Missouri, at 0130.

The purpose of the flight was for training using a Forward Looking Infrared (FLIR) system. Persons involved in the training were the DEA pilot, and the Missouri State Police observer to operate the FLIR system in the helicopter; two DEA agents and one Missouri State Policeman, on the ground. The pre-arranged plan was to have the two DEA agents and the policeman travel to a pre-selected location by motor vehicle and the helicopter to follow and maintain an altitude of approximately 1,500 feet above ground level (agl). After arriving at the location, the FLIR operator was to locate one of the individuals on the ground and follow him to a private residence while remaining at the pre-arranged altitude. The operation was to take place under the cover of darkness. There was no plan to land the helicopter at the location. Two way radio communication was maintained between the helicopter and the DEA agents on the ground.

During the night of the operation, one landing at an athletic field was conducted to make a repair to the FLIR system. The mission was aborted at another location when the FLIR operator was unable to identify the residence selected. A decision was made at that time to proceed to another location.

The DEA agents and the policeman arrived at the pre-selected location at 0344. The two DEA agents remained at the motor vehicle. The policeman began to approach the residence, walking west on a road. Both of the DEA agents indicated in their statements, that as the policeman was making his way west toward the residence they became aware that the helicopter was descending. The agents observations of the helicopter were based on their observance of the navigation lights on the helicopter and noises they heard during the event. They reported that the helicopter missed striking the policeman on the road by approximately 10 feet. The helicopter then touched down in an open field ringed by trees south of the road where the policeman was walking and west of where the agents were situated.

The DEA agents stated that the helicopter was observed to touch down on the rear of the skids first, flatten out, and skid forward. Both DEA agents stated that the helicopter then lifted off and continued south. One DEA agent stated that as the helicopter began to gain altitude, he heard a noise which he believed to be the main rotor hitting something. The DEA agents then observed the helicopter continue south approximately 50 to 75 yards and gain about 50 feet of altitude. They stated the helicopter initiated an abrupt right turn and the noise of the main rotor hitting trees became evident. They stated that the helicopter then rolled inverted and impacted the terrain. At no time did the witnesses observe the landing light to be illuminated on the helicopter, nor were there any radio transmissions heard from the helicopter.

A radar plot of the accident helicopter's flight path, just prior to impact, indicated that the helicopter was maintaining between 1,200 and 1,300 feet mean sea level (msl), in the area of the impact site, coincident with the approximate time of the accident. A copy of the Recorded Radar Study compiled by the NTSB, Office of Research and Engineering is attached as an addendum to this report. (Note: From surface charts the approximate elevation of the accident site was 900 feet msl).

OTHER DAMAGE

Trees and foliage were damaged during the accident.

PERSONAL INFORMATION

The pilot held a commercial certificate for helicopters and single engine airplanes. He also held an airline transport certificate for multi-engine airplanes. He had a total pilot time of 3,091 hours in all types of aircraft, with 289 hours in rotorcraft, and 220 hours in the make and model of the accident helicopter at the time of the accident. He was the holder of a first class medical certificate issued on July 2, 1993, with no limitations. His most recent biennial flight review was received in this make and model of helicopter one month prior to the accident.

AIRCRAFT INFORMATION

The helicopter was a Hughes 369HS, N9179F, serial number 140554S. The helicopter had accumulated 4,154 hours time in service at the time of the accident. An annual inspection was conducted on November 12, 1993, and the helicopter had accumulated eight hours time in service since the inspection. The total time on the engine was the same as the airframe and had accumulated 678 hours since the last overhaul.

WRECKAGE AND IMPACT INFORMATION

Marks corresponding with the size of the landing skids were found at the location described by witnesses to be the initial touchdown point on a heading of 185 degrees. These marks corresponded to a level attitude on terrain sloping forward and to the right approximately 10 to 15 degrees. The ground scars ended within about 15 feet. Multiple small branches of a tree 20 feet beyond the initial ground scars, 10 feet above ground level, were severed. A tree which was seven inches in diameter and located 150 feet beyond the initial ground contact marks was severed about 25 feet above ground level. The tree had numerous scars on the east side of it. The helicopter came to rest inverted 15 feet beyond the tree, on a heading of 330 degrees.

A continuity check of the flight control system (collective, cyclic, and directional) was completed with no pre-impact discrepancies noted.

An inspection of the collective/throttle control linkage to the governor/fuel control system showed no evidence of damage.

The helicopter was equipped with dual flight controls. Both systems were inspected. The left seat cyclic control stick was fractured at the base. The right directional control pedal for the left seat/pilot position was fractured. The right directional control pedal for the right seat position was fractured. Witness statements showed that the fracture was the result of efforts by fire/crash rescue team members to facilitate the rescue of the occupants.

The directional control rod was fractured at fuselage station 219.0 where the tailboom separation occurred. The control rod remained attached to the tail rotor gearbox bellcrank and when moved, showed no damage or malfunction of the tail rotor pitch control system.

The main rotor system (hub assembly) showed extensive damage with lead/lag excursions and excessive blade flapping. The hub assembly had impact marks consistent with main rotor blade strikes.

The tail rotor system (hub assembly) had minor damage, in the form of small dents and scratches.

On the airframe, the forward windscreen and framing were fractured and separated. The right cockpit door frame was crushed and bent.

The right front seat pan was buckled from the right/forward to left/rear.

The tailboom fractured at fuselage station 219.0, and was bent at the point of separation.

According to witness statements, the engine was still operating after the helicopter came to rest. The exact power setting is unknown. They stated the engine was shut down by the local fire department when they dispensed a fire suppressing agent into both exhausts.

The drive system was examined. The over-running clutch functioned when inspected; rotating in one direction, while engaging when rotated in the opposite direction. The engine to transmission driveshaft showed no evidence of damage. The main rotor system and tail rotor driveshaft rotated when the driveshaft was turned by hand.

The main rotor driveshaft and static mast were fractured approximately eight inches from the bottom.

The tail rotor driveshaft was fractured at fuselage station 219.0. The tail rotor driveshaft (forward of fuselage station 219.0 and aft) rotated freely in both directions. The aft portion remained connected via a Bendix coupling to the tail rotor gearbox. The forward portion of the drive shaft remained attached via a Bendix coupling.

The main transmission rotated freely when the main rotor system and/or the engine to transmission driveshaft was rotated by hand. The magnetic chip detector plug was examined and found to be free of chips.

The tail rotor gearbox rotated in both directions and showed no evidence of lockup or ratcheting. The magnetic chip detector plug was examined and found to be free of chips.

The yellow main rotor blade was separated from the main rotor system at the pitch case housing. The strap pack was fractured. The pitch change link was fractured at the upper portion while the rod end remained intact with the main rotor hub assembly. The trailing edge damper arm was bent. The vibration absorber attaching bracket was fractured and the vibration absorber weight was missing. The blade had a partial fracture at blade station 30 and a complete fracture at blade station 117. The trailing edge of the blade had extensive damage and the outboard section (from blade station 117) was located approximately 150 feet north of the main wreckage. The remaining section of the blade with the pitch case housing was found approximately 70 feet to the rear of the helicopter.

The white main rotor blade remained attached to the main rotor hub assembly, but exhibited a complete fracture at blade station 132. The vibration absorber attaching bracket was fractured and the pitch change link had two fractures resulting in approximately four inches of the barrel missing. Both pitch link rod ends remained intact.

The blue main rotor blade had bending at blade station 142. The pitch change link was fractured at the upper end while both rod ends remained intact.

The red main rotor blade had trailing edge damage and partial fractures at blade stations 20 and 73. The blade was bent both spanwise and chordwise. The strap pack had a fracture of the forward leg. The vibration absorber attaching bracket was fractured and the vibration absorber weight was missing. The pitch change link was fractured at the upper end and both rod ends were intact.

The red, blue, and white main rotor blades remained attached to the main rotor hub assembly which came to rest approximately 10 feet north of the helicopter, at the base of a tree which was described above as being severed at 25 feet and having damage on the east side.

The engine showed no evidence of displacement or damage. The governor and fuel control settings correlated with the collective and throttle controls. All engine fuel and air lines were inspected and no evidence of damage or looseness was observed.

Inspection of the fuel system revealed that the helicopter was equipped with an auxiliary fuel tank which remained intact and showed no evidence of leakage. The main fuel tank showed no evidence of damage, or leaking and contained fuel.

The fuel vent system was inspected to verify that the vent was open. No restriction was noted.

A vacuum check of the fuel system was conducted. A vacuum pressure of 10 inches was held for two minutes.

After the on-scene examination the helicopter was removed from the accident site to test run the engine at another location.

TESTS AND RESEARCH

On December 1, 1993, the engine was removed from the airframe. On December 2, 1993, the engine was test run at Aviall, Dallas, Texas. An engine test log provided by Aviall is attached to this report.

During the inspection and run of the accident helicopter engine, no failed or distressed parts were found within the engine nor any of its components.

During testing the engine was subjected to a power calibration with stabilized running at various power levels. Engine operation was found to be acceptable throughout the testing with no operational problems encountered. Start times, acceleration and deceleration time responses were within acceptable overhaul limits. Engine performance was found to be 3.3% below new engine acceptance standards and at maximum power, and 4.3% below for "Cruise B" power.

ADDITIONAL DATA/INFORMATION

Parties to the investigation were The Federal Aviation Administration, Flight Standards District Office, Saint Louis, Missouri; the Drug Enforcement Administration, Dallas, Texas; Allison Engine Company, Indianapolis, Indiana; and McDonnell Douglas, Mesa, Arizona.

The aircraft wreckage was released to the Drug Enforcement Administration on November 20, 1993.

NTSB Probable Cause

THE PILOT'S FAILURE TO MAINTAIN PROPER ALTITUDE. A FACTOR WAS THE DARK NIGHT.