Pinnacle Airlines Flight 3701
A Northwest Airlink CRJ-200 similar to the one involved.
|Date||October 14, 2004|
|Summary||Engine flameout, pilot disregard for procedure|
|Site||Jefferson City, Missouri, United States|
|Aircraft type||Bombardier CRJ-200|
(d/b/a Northwest Airlink)
On October 14, 2004, Pinnacle Airlines Flight 3701 (ICAO: FLG3701, IATA: 9E3701, or Flagship 3701) crashed while flying from Little Rock, Arkansas to Minneapolis–Saint Paul International Airport in Minnesota. No passengers were aboard. Both pilots were killed. Federal investigators determined the crash was due to the pilots' unprofessional behaviour and disregard for training and procedures.
Aircraft and crew
Pinnacle Airlines (operating under the Northwest Airlink banner) Flight 3701 was a repositioning flight[a] of an empty 50-seat Bombardier CRJ-200 (aircraft registration N8396A). The aircraft was built in 2000, and had accumulated 10,168 hours of flight time and completed 9,613 flight cycles[b] at the time of the crash.
Earlier in the day on October 14, 2004, a different Pinnacle Airlines flight crew were scheduled to fly the incident aircraft from Little Rock National Airport in Little Rock, Arkansas to Minneapolis–Saint Paul International Airport in Minnesota. However, the flight crew received an error message while attempting to take off, and aborted their takeoff. Pinnacle Airlines dispatched maintenance crews to Little Rock to resolve the problem. The problem was identified and fixed. Because the aircraft was needed in Minneapolis the next morning, Flight 3701 was scheduled overnight as a repositioning flight, to move the plane from Little Rock from Minneapolis.:11
The only persons on board Flight 3701 were the two pilots, captain Jesse Rhodes and first officer Peter Cesarz. Both pilots were trained at Gulfstream Academy in Florida and flew for Gulfstream International Airlines before being hired for Pinnacle Airlines.:11
Flight 3701 departed Little Rock at 21:21 Central Daylight Time[c]. The flight plan from Little Rock to Minneapolis indicated a planned cruising altitude of 33,000 feet (10,000 m).:1 After departing Little Rock, the plane pitched up sharply several times during its ascent, briefly reaching 10,000 feet (3,000 m) per minute.:2
At 21:35, Flight 3701 requested clearance to climb to 41,000 feet (12,000 m), the maximum operating altitude of the Bombardier CRJ series. Clearance was granted by air traffic control (ATC) at 21:36, and the plane climbed to its new cruising altitude shortly thereafter.:2 At 21:54, the pilots began to struggle with control of their plane. Both engines lost power and the plane's stick shaker warned the pilots of an impending stall. The pilots declared an emergency and descended, temporarily regaining control of their aircraft at 34,000 feet (10,000 m).:4
The pilots attempted to restart the engines, but could not do so. At 22:09, Flight 3701 asked ATC to direct them to the nearest airport for an emergency landing, and the controller on duty directed them to Jefferson City Memorial Airport in Jefferson City, Missouri. At 22:14, the pilots realized they were not going to make it to the airport, and began looking for a road or highway to land on.:5-6
At approximately 22:15, the plane crashed into the ground outside of Jefferson City. Both crew members were killed. There were no casualties on the ground.
The investigation into the accident focused mainly on information contained on the flight data recorder and the cockpit voice recorder. This is the official version of events as determined by that investigation.
Investigators determined that the two pilots were exploring the performance limits of the empty CRJ-200 on the flight. The pilots decided to test the limits of the CRJ and join the "410 club", referring to pilots who pushed CRJs to their maximal approved altitude of flight level 410 (FL410; 41,000 feet (12,000 m)).
The accident sequence started when the pilots performed several non-standard maneuvers at 15,000 feet (4,600 m), including a pitch-up at 2.3g (23 m/s²) that induced a stall warning. They set the autopilot to climb at 500 ft/min (150 m/min) to FL410. This exceeded the manufacturer's recommended climb rate at altitudes above FL380. In the attempt to reach FL410, the plane was pulled up at over 1.2g, and the angle of attack became excessive to maintain climb rate in the thinner upper atmosphere. After reaching FL410, the plane was cruising at 150 knots (280 km/h; 170 mph), barely above stall speed, and had over-stressed the engines.
The anti-stall devices activated while they were at altitude, but the pilots overrode the automatic nose-down that would increase speed to prevent stall. After four overrides, both engines experienced flameout and shut down. The plane then stalled, and the pilots recovered from the stall at FL380 while still having no engines. At that altitude, there were six airports within reach for a forced landing. This led the pilots to pitch nose down in an attempt to restart the engines, which requires a dive sharp enough to attain the required 300 knots (560 km/h; 350 mph) for a windmill restart to make the blades in the turbines windmill at 10% N2 (turbine rotational speed). The captain did not take the necessary steps to ensure that the first officer achieved the 300 knots (560 km/h; 350 mph) or greater airspeed required for the windmill engine restart procedure and then did not demonstrate command authority by taking control of the airplane and accelerating it to at least that speed.
The turbine blades expanded, however, contacting the honeycomb labyrinth seals and allowing the metal to scrape together when the engine overheated, with zero core rotation. When the engine is shut down at altitude, the core begins to cool, and the stator, including the static interstage static seal (ISS), contracts at a faster rate than the adjacent rotating parts in both the radial and axial direction because of its smaller thermal time constant. The relative rate of cooling of the stator and rotor results in an alignment of the rotating-seal knife edges aft of the normal operating groove in the static seal. If the clearances are tight enough and the relative cooling rates are right, contact can occur between the static and rotating seal elements. The resulting stiction can temporarily prevent the rotor from turning when only the force of ram air is applied to the core. Air turbine starter (ATS) torque has been shown adequate to overcome this restriction. Thus, when the engine cooled, the assembly did not match anymore, and the blades could not rotate freely. The crew ended the descent when they had reached 230 knots (430 km/h; 260 mph) but neither engine core (N2) ever indicated any rotation during the entire descent. Since they were too high for an APU start, the ram air turbine (known as an "air-driven generator" on Bombardier products) was deployed to provide electric power for the aircraft, and the crew donned oxygen masks, as the cabin slowly depressurized due to loss of pressurization air from the engines.
The crew glided for several minutes and then tried to restart engines using the APU at 13,000 feet (4,000 m). This was again unsuccessful. They then declared to Air Traffic Control (ATC) that they had a single-engine flameout. At this point they had four diversion airports available to them. They lost considerable altitude while continuing unsuccessfully to attempt to restart both the left engine (two times) and the right engine (two times) for over 14 minutes, using the emergency restart procedure. Despite their four auxiliary power-unit-assisted engine restart attempts, the pilots were unable to restart the engines because their cores had locked. Without core rotation, recovery from the double engine failure was not possible. At that point, the pilots finally declared to ATC that they had in fact lost both engines.
The NTSB also determined from flight data recorder information that the turbofan jet engine (General Electric CF34-3B1) engine 2 turbine was operating at 300 °C above the maximal redline temperature of 900 °C at 41,000 feet (12,000 m). Engine 1 HPT stayed 100 °C below the redline.
On January 9, 2007, the NTSB issued its final report on Flight 3701. In its report, the NTSB concluded that the probable causes of the accident were:
- the pilots' unprofessional behavior, deviation from standard operating procedures, and poor airmanship;
- the pilots' failure to prepare for an emergency landing in a timely manner, including communicating with air traffic controllers immediately after the emergency about the loss of both engines and the availability of landing sites; and
- the pilots' improper management of the double engine failure checklist.
Pinnacle Airlines has restricted flights to a maximum of FL370. It has also changed its training program to include high-altitude operations in ground school and simulator training. In addition, each crew is taken in the simulator up to FL410 and shown what the airplane did on the night Flight 3701 crashed.
Thomas Palmer, former manager of Pinnacle's training program, said about the crash: "It's beyond belief that a professional air crew would act in that manner."
- Aircraft Accident Report, Crash of Pinnacle Airlines Flight 3701, Bombardier CL-600-2B19, N8396A, Jefferson City, Missouri, October 14, 2004 (PDF). National Transportation Safety Board. January 9, 2007. NTSB/AAR-07-01. Retrieved December 28, 2017.
- Wald, Matthew L. (June 14, 2005). "Just Before Dying, a Thrill at 41,000 Feet". The New York Times. Retrieved December 28, 2017.
- "FAA Registry (N8396A)". Federal Aviation Administration.
- "What Went Wrong: The Crash Of Flight 3701". Popular Mechanics. January 5, 2006.
- NTSB Accident Information Brief Update for October 29, 2004.
- 2004 Darwin Award nominee 4-1-0 Club
- Crash From Dual Engine Flameout Spurs Wide Ranging Review (Air Safety Week)
- ALPA responds to the crash of Pinnacle Flight 3701 – Air Line Pilot