Pinnacle Airlines Flight 3701
Encyclopedia
Pinnacle Airlines
Flight 3701 (ICAO: FLG3701, IATA: 9E3701, or Flagship 3701) crashed on October 14, 2004, near Jefferson City, Missouri
, United States. It was an overnight ferry flight
(with no passengers) from Little Rock, Arkansas
, U.S. to Minneapolis-St. Paul International Airport, U.S. Both crew members were killed.
(operating under the Northwest Airlink
banner) Flight 3701 was an empty 50-seat Bombardier CRJ-200
(CL-600-2B19), , on ferry from Little Rock, Arkansas
(Little Rock National Airport
) to Minneapolis-St. Paul International Airport, manned by two pilots, Captain Jesse Rhodes and First Officer Peter Cesarz. The jet crashed when the engines could not be restarted and they could not glide to an airport. There were no casualties on the ground.
Both pilots were trained at Gulfstream Academy in Florida
, eventually hired on with Pinnacle Airlines
after their time spent with Gulfstream International Airlines
.
and the cockpit voice recorder
. This is the official version of events as determined by that investigation.
The two pilots were exploring the performance limits of the empty CRJ-200 on the ferry flight. The pilots decided to test the limits of the CRJ, and join the "410 Club," referring to pilots who pushed CRJs to their maximum approved altitude of Flight Level
410 (41,000 feet).
The accident sequence started when the pilots performed several non-standard maneuvers at 15,000 feet, 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 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), 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 kt 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-knot 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 300 knots.
However, the turbine blades expanded contacting the honeycomb labyrinth seals allowing the metal to scrape on each other when the engine overheated with zero core rotation. When the engine is shutdown 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 faster 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 (NTSB Accident Information Brief Update for October 29, 2004.) 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 kt 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 power the aircraft, and the crew donned oxygen mask
s as the cabin slowly depressurized due to loss of pressurization air from the engines.
The crew glided for several minutes. The crew then tried to restart engines using the APU at 13,000 ft. 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. After continuing unsuccessfully to attempt to restart both the left engine (two times) and the right engine (two times) for over 14 minutes, while utilizing the emergency restart procedure, much altitude was lost. 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. It was after these unsuccessful attempts that they declared to ATC that they had in fact lost both engines.
Unable to reach the assigned diversion airport, Jefferson City Memorial Airport
, they crashed six minutes later outside Jefferson City, Missouri
, behind a row of houses (the 600 block of Hutton Lane — two-and-a-half miles short of the airport), and the plane caught fire. Both pilots were killed. There was some damage to houses and a garage, but no one on the ground was hurt.
The National Transportation Safety Board
has determined from the Flight Data Recorder that the turbofan
jet engine
(General Electric CF34-3B1) engine 2 turbine was operating at 300 °C above the maximum redline temperature of 900 °C at 41,000 ft. Engine 1 HPT stayed 100 °C below the redline.
In its final Accident Report, the NTSB determined as the probable causes of the accident:
Pinnacle Airlines
Pinnacle Airlines, Inc. is an American regional airline, which is a subsidiary of Pinnacle Airlines Corp., and operates as Delta Connection for Delta Air Lines...
Flight 3701 (ICAO: FLG3701, IATA: 9E3701, or Flagship 3701) crashed on October 14, 2004, near Jefferson City, Missouri
Jefferson City, Missouri
Jefferson City is the capital of the U.S. state of Missouri and the county seat of Cole County. Located in Callaway and Cole counties, it is the principal city of the Jefferson City metropolitan area, which encompasses the entirety of both counties. As of the 2010 census, the population was 43,079...
, United States. It was an overnight ferry flight
Ferry flying
Ferry flying refers to delivery flights for the purpose of returning an aircraft to base, moving an aircraft from one base of operations to another or moving an aircraft to or from a maintenance facility for repairs, overhaul or other work.-Ferry permit:...
(with no passengers) from Little Rock, Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...
, U.S. to Minneapolis-St. Paul International Airport, U.S. Both crew members were killed.
Accident
Pinnacle AirlinesPinnacle Airlines
Pinnacle Airlines, Inc. is an American regional airline, which is a subsidiary of Pinnacle Airlines Corp., and operates as Delta Connection for Delta Air Lines...
(operating under the Northwest Airlink
Delta Connection
Delta Connection is the name under which a number of individually owned regional airlines and one wholly owned regional carrier operate short and medium haul routes in association with Delta Air Lines Inc...
banner) Flight 3701 was an empty 50-seat Bombardier CRJ-200
Bombardier CRJ200
The Bombardier CRJ100 and CRJ200 are a family of regional airliner manufactured by Bombardier, and based on the Canadair Challenger business jet.-Development:...
(CL-600-2B19), , on ferry from Little Rock, Arkansas
Little Rock, Arkansas
Little Rock is the capital and the largest city of the U.S. state of Arkansas. The Metropolitan Statistical Area had a population of 699,757 people in the 2010 census...
(Little Rock National Airport
Little Rock National Airport
Little Rock National Airport , officially Little Rock National Airport/Adams Field, is located 2 miles east of the central business district of Little Rock, a city in Pulaski County, Arkansas, United States. It is Arkansas' largest commercial service airport, serving more than 2.1 million...
) to Minneapolis-St. Paul International Airport, manned by two pilots, Captain Jesse Rhodes and First Officer Peter Cesarz. The jet crashed when the engines could not be restarted and they could not glide to an airport. There were no casualties on the ground.
Both pilots were trained at Gulfstream Academy in Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, eventually hired on with Pinnacle Airlines
Pinnacle Airlines
Pinnacle Airlines, Inc. is an American regional airline, which is a subsidiary of Pinnacle Airlines Corp., and operates as Delta Connection for Delta Air Lines...
after their time spent with Gulfstream International Airlines
Gulfstream International Airlines
Gulfstream International Group, Inc., operating as Gulfstream International Airlines , is a United States airline based in Fort Lauderdale, Florida. It operates scheduled and charter services to Florida and Bahamas and the Caribbean. It operates as a United Express carrier for United Airlines...
.
Ferry Flight
Due to urgent but routine maintenance, the aircraft was unavailable for a scheduled flight earlier in the day. As do many airlines, Pinnacle had a spare aircraft available, which it used. The aircraft involved in the accident was then required at Minneapolis-St. Paul International Airport (MSP), where it would have been had it undertaken its originally scheduled flight. For this reason it was necessary to ferry the aircraft to MSP.Investigation
The investigation into the accident focused mainly on information contained on the flight data recorderFlight data recorder
A flight data recorder is an electronic device employed to record any instructions sent to any electronic systems on an aircraft. It is a device used to record specific aircraft performance parameters...
and the cockpit voice recorder
Cockpit voice recorder
A cockpit voice recorder , often referred to as a "black box", is a flight recorder used to record the audio environment in the flight deck of an aircraft for the purpose of investigation of accidents and incidents...
. This is the official version of events as determined by that investigation.
The two pilots were exploring the performance limits of the empty CRJ-200 on the ferry flight. The pilots decided to test the limits of the CRJ, and join the "410 Club," referring to pilots who pushed CRJs to their maximum approved altitude of Flight Level
Flight level
A Flight Level is a standard nominal altitude of an aircraft, in hundreds of feet. This altitude is calculated from the International standard pressure datum of 1013.25 hPa , the average sea-level pressure, and therefore is not necessarily the same as the aircraft's true altitude either...
410 (41,000 feet).
The accident sequence started when the pilots performed several non-standard maneuvers at 15,000 feet, including a pitch-up at 2.3g
G-force
The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...
(23 m/s²) that induced a stall
Stall (flight)
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded...
warning. They set the autopilot
Autopilot
An autopilot is a mechanical, electrical, or hydraulic system used to guide a vehicle without assistance from a human being. An autopilot can refer specifically to aircraft, self-steering gear for boats, or auto guidance of space craft and missiles...
to climb at 500 ft/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), 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
Flameout
A flameout refers to the failure of a jet engine caused by the extinction of the flame in the combustion chamber. It can be caused by a number of factors, including fuel exhaustion; compressor stall; insufficient oxygen supply; foreign object damage ; severe inclement weather; and mechanical...
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 kt 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-knot 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 300 knots.
However, the turbine blades expanded contacting the honeycomb labyrinth seals allowing the metal to scrape on each other when the engine overheated with zero core rotation. When the engine is shutdown 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 faster 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 (NTSB Accident Information Brief Update for October 29, 2004.) 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 kt but neither engine core (N2) ever indicated any rotation during the entire descent. Since they were too high for an APU
Auxiliary power unit
An auxiliary power unit is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft, as well as some large land vehicles.-Function:...
start, the ram air turbine
Ram air turbine
A ram air turbine is a small turbine that is connected to a hydraulic pump, or electrical generator, installed in an aircraft and used as a power source...
(known as an "Air Driven Generator" on Bombardier
Bombardier Aerospace
Bombardier Aerospace is a division of Bombardier Inc. and is the third-largest airplane manufacturer in the world. It is headquartered in Dorval, Quebec, Canada.- History :...
products) was deployed to power the aircraft, and the crew donned oxygen mask
Oxygen mask
An oxygen mask provides a method to transfer breathing oxygen gas from a storage tank to the lungs. Oxygen masks may cover the nose and mouth or the entire face...
s as the cabin slowly depressurized due to loss of pressurization air from the engines.
The crew glided for several minutes. The crew then tried to restart engines using the APU at 13,000 ft. This was again unsuccessful. They then declared to Air Traffic Control
Air traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
(ATC) that they had a single engine flameout. At this point they had four diversion airports available to them. After continuing unsuccessfully to attempt to restart both the left engine (two times) and the right engine (two times) for over 14 minutes, while utilizing the emergency restart procedure, much altitude was lost. Despite their four auxiliary power unit-assisted engine restart attempts, the pilots
were unable to restart the engines because their cores had locked
Core lock
Core lock is a jet engine failure that can happen on aircraft in flight, after an engine stops working for a period. When a jet engine has a flameout, the cooling air no longer circulates normally. If an aircraft is moving slowly, the sizes of some engine parts may change quicker than others, such...
. Without core rotation, recovery from the double engine failure was not possible. It was after these unsuccessful attempts that they declared to ATC that they had in fact lost both engines.
Unable to reach the assigned diversion airport, Jefferson City Memorial Airport
Jefferson City Memorial Airport
Jefferson City Memorial Airport is a public airport located two miles northeast of the central business district of Jefferson City, in Callaway County, Missouri, United States...
, they crashed six minutes later outside Jefferson City, Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
, behind a row of houses (the 600 block of Hutton Lane — two-and-a-half miles short of the airport), and the plane caught fire. Both pilots were killed. There was some damage to houses and a garage, but no one on the ground was hurt.
Aftermath
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.The National Transportation Safety Board
National Transportation Safety Board
The National Transportation Safety Board is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and incidents, certain types of highway crashes, ship and marine...
has determined from the Flight Data Recorder that the turbofan
Turbofan
The turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...
jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
(General Electric CF34-3B1) engine 2 turbine was operating at 300 °C above the maximum redline temperature of 900 °C at 41,000 ft. Engine 1 HPT stayed 100 °C below the redline.
In its final Accident Report, the NTSB determined as the probable causes of the accident:
- 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;
- the pilots' improper management of the double engine failure checklist.
External links
- Pinnacle Airlines (d.b.a. Northwest Airlink) Flight 3701 Jefferson City, Missouri October 14, 2004 DCA05MA003 (NTSB)
- Cockpit voice recorder transcript (NTSB)
- Crash From Dual Engine Flameout Spurs Wide Ranging Review (Air Safety Week)
- PM Staff. What Went Wrong: The Crash Of Flight 3701 Popular MechanicsPopular MechanicsPopular Mechanics is an American magazine first published January 11, 1902 by H. H. Windsor, and has been owned since 1958 by the Hearst Corporation...
. January 5, 2006.