SEA96FA209

The pilot received a full weather briefing from a Flight Service Station (FSS) on the morning of the accident. The FSS briefer told the pilot that moderate turbulence and icing prevailed along the pilot's intended route of flight, and that there were forecasts for isolated thundershowers. The briefer advised the pilot to call for an update just prior to departure. The pilot departed on the flight almost 3 hours later without calling for an update. He received an IFR clearance after 15 minutes of delays, then proceeded on course to his destination. About 35 minutes after departure, while cruising at 16,000 feet, the pilot reported that he was 'in the clouds and the bumps are big time.' About 3 minutes later, the pilot radioed that he was 'in a dive and I don't...' The airplane impacted terrain in a nose-down, inverted attitude and exploded. Analysis of recorded radar and meteorological data indicates that the airplane encountered a thunderstorm, strong updrafts, downdrafts, and turbulence.

History of flight

On September 5, 1996, at 1157 mountain daylight time, N128RP, a Cessna 340A, operated by the owner/pilot, collided with terrain near Wise River, Montana, and was destroyed during an uncontrolled descent. The uncontrolled descent was precipitated by a loss of control during a climb to cruise. The commercial pilot, the sole occupant, was fatally injured. There was a ground fire. Instrument meteorological conditions (IMC) prevailed and an instrument flight rules (IFR) flight plan had been filed. The personal flight departed from Butte, Montana, at 1117 and was en route to McCall, Idaho. The flight was conducted under 14 CFR 91.

An acquaintance of the pilot (statement attached) stated that she flew with the pilot as a passenger from McCall, Idaho, to Butte, Montana, one day before the accident. The pilot had just purchased a home in McCall and the airplane was based there. The acquaintance stated that the pilot stayed overnight at her home in the Butte area. She stated that he "felt fine" and "got a good night's sleep." She also stated that he did not indicate that he was having any problems with himself or the airplane on the evening prior to, or morning of, the accident. On the morning of the accident, the pilot woke up, collected his fishing equipment, and left for the Butte Airport. This was the last time that she saw or heard from the pilot.

According to voice communications recorded by the Federal Aviation Administration's (FAA) Great Falls Automated Flight Service Station (AFSS), Great Falls, Montana, a person identifying himself as the pilot of N128RP telephoned the AFSS at 0825 on the morning of the accident to receive a weather briefing. The telephone conversation was 10 minutes in length, and concluded with the pilot filing an IFR flight plan. The pilot asked the FSS briefer: "... tell me what I'm going to run into..." and he told the briefer that he was planning to depart from Butte at 1000 and fly to McCall.

The briefer began to describe the overall weather conditions affecting the pilot's proposed route of flight. The briefer stated that the pilot "... may see some mountain obscuration," and "...occasional to moderate turbulence up to [30,000 feet]." He also told the pilot that "... from Butte all the way over, you'll be in an area of occasional moderate rime or mixed icing... between the 7,000 foot level and [18,000 feet]."

The briefer further discussed that radar showed a "... line of showers to the west of you that runs from McCall northeastward, north of Salmon through the Missoula-Kalispell area, and those areas of showers will be moving eastward... so, right now, heading down to McCall you may not get into too many showers." The pilot acknowledged this and asked about "... the current word on the [cloud] tops." The briefer read the pilot two pilot reports (PIREPs). One of them indicated that a pilot flying from Billings to Helena, Montana, in an "AC12" reported the base of the clouds at 8,300 feet with "occasional light chop." The other PIREP, reported by a pilot flying a Cessna 310 at 11,000 feet and 22 miles west of Helena, reported "moderate rime ice." The briefer then stated "... there is ice in that stuff," and the pilot responded with "yea."

The briefer then provided an outlook for the pilot's intended route of flight. The outlook for the central Idaho area called for "...widely scattered light rain showers with isolated thundershowers. Tops of the thundershowers at [38,000 feet]. Now I'm not showing any thundershowers, at least nothing that's... very big." The briefer then described more favorable weather conditions in southern Idaho and for Boise, Idaho, after 1100. The pilot replied: "So it's clearing." The briefer responded with "Yes, but before you go, I'd call and get an update." The pilot responded with "right."

The briefer then concluded the briefing and said "... got the mountain obscuration that would be mostly north of you... we know about the ice... that's about what we're looking at." The pilot acknowledged and filed an IFR flight plan from Butte to McCall. He reported that he had five hours of fuel on board, and that his flight time was scheduled to be one hour and ten minutes.

According to radar data and voice communications (data and transcripts attached) recorded by the FAA Air Route Traffic Control Center (ARTCC) in Salt Lake City, Utah, the pilot of the accident airplane initiated contact with the ARTCC at 1120:57, after having just departed from Butte. This contact was initiated 2 hours and 46 minutes after receiving his first and only weather briefing. The ARTCC instructed the pilot to "... maintain a position VFR, expect an IFR clearance in five minutes."

At 1122:31, the ARTCC informed the pilot that there was a "regional jet" in the area, and another aircraft executing a precision approach into Butte. The pilot stated "...I'll stay below the clouds below him." At 1125:47, the ARTCC informed the pilot that another aircraft was executing a non-precision approach into Butte and "as soon as he's clear you can expect a clearance." The accident pilot acknowledged. At 1129:34, the ARTCC asked the pilot where the base of the clouds were. The pilot said that they were "...right at [7,600 feet]." The ARTCC replied with "Roger. You may want to monitor unicom and see if you can talk to this sky west regional coming inbound...." At 1132:27, the ARTCC informed the pilot to "...expect an additional five minute delay as I get an altitude that clears you from the sky west...."

At 1135:16, the pilot received an IFR clearance from the ARTCC to climb to 13,000 feet above mean sea level (msl). At 1142:41, the pilot reported that he was over the Coppertown VOR at 13,000 feet and was turning southwest bound to intercept his course to McCall. At 1147:08, the pilot was cleared to his proposed cruising altitude of 16,000 feet msl. The airplane arrived at 16,000 feet msl about 1150:00.

At 1154:00, the pilot radioed to the ARTCC that he was "... in the clouds and the bumps are big time..." and he requested clearance for a climb to 18,000 feet msl. The ARTCC controller cleared the airplane to a block altitude from 17,000 feet msl to 19,000 feet msl. The pilot acknowledged, initiated a climb, and stated that the turbulence was "moderate, sometimes worse."

At 1156:52, the pilot radioed that he was at 17,000 feet and "... having a problem." The ARTCC controller said "go ahead," and the pilot radioed: "Romeo pappa is in a dive and I don't...." This was the pilot's last transmission, despite several attempts from the ARTCC to hail the pilot. The airplane disappeared from radar 38 seconds later.

According to a Recorded Radar Study (report attached) performed by the Safety Board's Office of Research and Engineering, the airplane was cruising at 16,000 feet msl at the time the pilot radioed that he was "... in the clouds and the bumps are big time...." During the previous 30 seconds to this radio call, the airplane's indicated airspeed had decreased from 192.8 knots to 139.7 knots, while its heading and altitude remained constant. One minute and 17 seconds later, as the pilot was describing the turbulence as "moderate, sometimes worse," the airplane had slowed to 99.1 knots.

During the subsequent 60 seconds, the airplane's track angle abruptly changed from 260 degrees to 115 degrees, and it began a 4,000 foot-per-minute descent. The airplane descended from 17,300 feet msl to 15,900 feet msl. The airplane then climbed back up to 17,300 feet msl in 20 seconds, then descended to 15,500 feet msl nine seconds later. The calculated indicated airspeed fluctuated from a high of 155 knots to a low of 92 knots during this time period.

At this point in time, at 1157:02, the pilot stated that he was "in a dive...." The airplane was then observed to climb from 15,500 feet to 16,300 feet msl in 19 seconds, t