# NTSB SEA98FA100: Aero Commander 680FL, N446JR, Helena, MT, June 17, 1998 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: June 16, 1998, 18:00 local (Jun 17, 1998, 00:00 UTC) - Place: Helena, MT - Coordinates: 46.5302, -112.209831 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=46.5302&lon=-112.2098&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report January 11, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 42718 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA98FA100 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42718/pdf - Page: https://openairdocs.org/ntsb/SEA98FA100 ## Probable cause The pilot's failure to maintain the correct altitude while turning inbound during a procedure turn to the ILS final approach course. Factors include hilly/mountainous terrain and clouds in the area where the course reversal was performed. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight collision with terrain/water, approach - iaf to faf/outer marker (ifr) - proper altitude - not maintained, pilot in command (cause) - terrain condition - mountainous/hilly (contributing factor) - weather condition - clouds (contributing factor) ## Analysis The pilot of the Part 135 cargo flight was executing the 'full' ILS runway 27 approach at Helena Regional Airport in a non-radar environment. Although the approach calls for the pilot to maintain 7,000 feet until intercepting the glideslope, the aircraft impacted the terrain at 5,300 about 1.5 miles prior to reaching the point where the pilot should have crossed the Hauser NDB at an altitude of 6,741 feet. According to the approach plate, the aircraft should not have descended to an altitude below 5,400 feet until reaching the outer marker, which is located about five and one-half miles west of the impact site. ## Factual narrative HISTORY OF FLIGHT On June 16, 1998, approximately 1800 mountain daylight time, an Aero Commander 680FL, N446JR, impacted the terrain while on approach to runway 27 at Helena Regional Airport, Helena, Montana. The commercial pilot, who was the sole occupant, received fatal injuries and the aircraft was destroyed. The 14 CFR Part 135 cargo flight, which departed Kalispell, Montana, about 55 minutes earlier, was operating in instrument meteorological conditions at the time of the accident. The aircraft, which was owned and operated by Corporate Air, of Billings, Montana, was on an IFR flight plan, and the ELT transmissions that were triggered by the impact played a role in locating the wreckage. On the day of the accident, the pilot departed Kalispell, Montana, about 1705, for the first segment of a multi-leg cargo flight. After departure, he climbed to 15,000 feet, and about 15 minutes after departure reported that he was accumulating traces of rime ice. About 30 minutes after takeoff, he requested a lower altitude, and Salt Lake Center cleared him to 13,000 feet. About 1740, Center terminated radar service and instructed the pilot to contact Helena Approach, a non-radar facility. About one minute later, the pilot contacted Helena Approach and advised that he was at 13,000 feet on the 300 radial of Helena VOR at 27.9 DME. Approach asked the pilot to reduce his speed for sequencing, and advised him to remain at 13,000 feet. About 30 seconds later, the pilot advised that he was picking up some ice, and Approach advised that they would try to get him a lower altitude. About one minute later, Approach cleared the pilot to 12,000 feet, and about 90 seconds after that cleared him to 11,000 feet. Just after being cleared to 11,000 feet, the pilot asked if he should be expecting a "...back course Charlie approach" and was advised that the controller would probably not be able to clear him for that specific approach. During that same radio transmission, the controller told the pilot that he was "...cleared to the Helena VOR via a 13 mile arc and the 270 degree radial..." and asked him to report intercepting the arc. The controller also reminded the pilot to "... keep your speed back." The pilot incorrectly read the clearance back as "... cleared to the VOR on a 270 and report the VOR." About 10 seconds after the read-back, the controller responded with " If it don't work right you can plan a no delay on a VOR Alpha or an ILS." There were no further communications between the controller and pilot for a little over three minutes. Then, about 1747, the pilot advised Approach that he was at 10 DME. The controller responded with "Airspur 31, I thought you were going to fly the arc," and the pilot stated "Negative, thought I was going direct to the VOR." The controller then advised the pilot that it was "no problem" and that "...we'll fix it up." The controller immediately changed the clearance for Airspur 31 to "...cleared to the Helena VOR, hold west, expect further clearance at 2355," while maintaining 11,000 feet. The pilot read back that clearance correctly, and about one minute later, the controller asked the pilot if he would like to fly the ILS. When the pilot responded affirmatively, the controller issued a new clearance of "... descend and maintain 9,500, cleared to the Hauser radio beacon via the VOR, direct Hauser, report crossing the VOR, expect approach at that time, resume normal speed." The pilot then incorrectly read back the clearance as "... descend and maintain 9,500, cleared to Hauser VOR and expect further clearance at that time..." The controller clarified the fact that the clearance was "...via the VOR, direct Hauser," and the pilot read back the clarification. At 1751, the controller issued the final clearance for the pilot to "...cross Helena VOR at or above 9,500, cleared ILS approach via the VOR direct Hauser, report leaving 9,000 feet." The pilot read that clearance back as "... cross the VOR at 9,500, cleared for the ILS, report leaving 9,500 feet..." About one minute later, the pilot reported crossing the VOR and leaving 9,500 feet, and the controller instructed him to report Hauser inbound. About two minutes after giving the pilot his approach clearance, the controller asked him his altitude, and the pilot reported that he was out of 8,500 and was at 6.9 DME (1.5 miles west of Hauser). About four and one-half minutes later the controller asked the pilot what his position was, and he responded that he was "... over Hauser, just turning inbound, out of 7,000." The controller then instructed the pilot to switch to tower and to report FERRI (the outer marker). When the pilot had not contacted the tower after about one and one-half minutes, the tower transmitted "Airspur 31, say altitude passing." The tower attempted two more times to contact Airspur 31, and at 1759:35 (about two minutes after the pilot had been instructed to switch to tower), the pilot transmitted "Airspur 31. Go ahead." The tower again asked what altitude he was leaving, and the pilot responded with "... Airspur 31 is out of 5,500." The tower then cleared the pilot to land on runway 27, and the pilot repeated the clearance. About one minute later, the tower transmitted "Airspur 31, say your distance." There was no response to this transmission, and there was no further contact with the aircraft. WRECKAGE AND IMPACT INFORMATION The aircraft impacted the terrain about 500 feet north of and 150 feet below the top of the highest ridge of the Spokane Hills. The accident site, which was located at 46 degrees 34.12 minutes North, 111 degrees 43.03 minutes West, was located about one and one-half mile east of the Hauser NDB. The aircraft initially impacted several trees about 75 feet above the ground, and settled into a dense forest on a northerly heading. Except for the right engine and the left propeller, the complete aircraft came to rest at one location. The right engine had come to rest about 40 feet north of the main wreckage, and the left propeller was found about 25 feet west. The fuselage, from the aft part of the cabin to the nose of the aircraft, was almost completely consumed by the intense post-crash fire. The aft portion of the fuselage, including the empennage, was extensively damaged by fire, but remained as an identifiable structure. The right wing, outboard of the engine nacelle, had been torn off and was located just behind and to the east of the empennage. The inboard portion of the right wing had been shredded and torn into numerous small pieces and was extensively damaged by the fire. The left wing, from just outboard of the engine nacelle, had separated into two distinct sections, both of which had been torn, crushed and distorted by impact with the trees. Both of these sections, as well as the inboard portion of the wing, had been extensively damaged or melted by the fire. The position of the nose gear could not be determined because of the extent of damage, but both main gear were in the up position. The position of the flaps, most of which had been torn from the wings during the impact sequence or destroyed by the post-impact fire, could not be determined. Aileron control system continuity could not be established due to the extent of damage, but elevator and rudder continuity was established from the aft portion of the cabin to the flight controls themselves. Both propeller hubs had separated from their crankshafts, and one blade of the right propeller had separated from the hub at the hub-to-blade clamp. Two of the three blades of the left propeller showed a numerous leading edge gouges and indentations. The third blade showed only light leading edge indentations, but contained chord-wise scarring on the outboard third of its span. Both of the blades with significant leading edge damage also showed longitudinal twisting, and on one about two inches of the tip had been torn off. All three blades of the right propeller showed varying degre ## Aircraft - Registration: [N446JR](https://openairdocs.org/deregistered/N446JR-1998-12-16), registration cancelled 1998-12-16, S/N 132510 (OpenAirDocs) - Reported make and model: Aero Commander 680FL - Registry model: [Aero Commander 680FL](https://openairdocs.org/model/aero-commander-680fl) (registry code 0141608) (OpenAirDocs) - Category: Airplane - Serial number: 1325-10 - Airframe hours: 17972 - Engines: Lycoming IO-720-B1B 400 horsepower reciprocating - Damage: Destroyed - Fire: On-Ground - Flight: Part 135 - Registered owner: Corporate Air - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, May 7, 1998, 85 hours before - Departed: FCA, KALLISPELL, MT - Destination: HLN, HELENA, MT - Flight plan: IFR - Airport: HLN, Helena Regional Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 42; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; toxicology performed; flight hours: 1,506 total, 344 in this make and model, 1,480 as pilot in command, 199 in the last 90 days, 54 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Instrument (IMC), Day - Wind: 290° at 76 knots - Visibility: 6 statute miles - Lowest ceiling: 2,600 ft broken - Temperature: 48 °F, dew point 46 °F - Altimeter: 29.00 inHg - Observed at: KHL, 10 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 19980616035479A](https://openairdocs.org/incident/19980616035479A), Jun 16, 1998: Gulstm 680FL, Helena, MT, Destroyed, 1 fatal. On June 16, 1998, a GA-680-FL, N446JR, crashed while on an IFR instrument approach to the Helena, Montana airport. The aircraft was operated by corporate air… 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.