Aircraft upset is an unacceptable condition in aircraft operations in which the aircraft flight attitude or airspeed is outside the normally intended limits. This may result in the loss of control (LOC) of the aircraft, and sometimes the total loss of the aircraft itself. Loss of control may be due to excessive altitude for the airplane's weight, turbulent weather, pilot disorientation, or a system failure.

The U.S. NASA Aviation Safety ProgramNote: Partial text copied from referenced FAA or NASA document. As a public work of the U.S. Government, the document is in the public domain and has no copyright. defines upset prevention and upset recovery as pertinent to loss-of-control accidents due to aircraft upset after inadvertently entering an extreme or abnormal flight attitude.

A Boeing-compiled list determined that 2,051 people died in 22 accidents in the years 1998–2007 due to LOC accidents. NTSB data for 1994–2003 count 32 accidents and more than 2,100 lives lost worldwide.http://www.nastarcenter.com/news/view.php?volume=2&issue=4&article=101

Overview

Loss of control as a factor in aviation accidents came into the spotlight with the 1994 crash of USAir Flight 427, which killed all 127 passengers and 5 crew members on board. In their report on the crash, the U.S. National Transportation Safety Board (NTSB) stated that prior to the crash they "had issued a series of safety recommendations over a 24-year period, asking the US Federal Aviation Administration (FAA) to require air carriers to train pilots in recoveries from unusual flight attitudes. Throughout this period, the Safety Board was generally not satisfied with the FAA's responses to these recommendations; specifically, the Board disagreed with the FAA's responses that cited the inadequacy of flight simulators as a reason for not providing pilots with the requested training. However, after the USAir Flight 427 accident and the October 31, 1994, ATR-72 accident involving American Eagle Flight 4184 near Roselawn, Indiana, the FAA issued guidance to air carriers, acknowledging the value of flight simulator training in unusual attitude recoveries and encouraging air carriers to voluntarily provide this training to their pilots."

Following those accidents, some carriers did implement their own voluntary training programs and the NTSB regarded those programs as "excellent".

In October 1996, the NTSB issued a formal Safety Recommendation (A-96-120), which requested the FAA to require all airlines to provide simulator training for flight crews which would enable them to recognize and recover from "unusual attitudes and upset maneuvers, including upsets that occur while the aircraft is being controlled by automatic flight control systems, and unusual attitudes that result from flight control malfunctions and uncommanded flight control surface movements".

In 2004, the FAA issued its first Airplane Upset Recovery Training Aid, which dealt with aircraft of more than 100 seats. The second revision of that document was released in 2008 and dealt with issues for aircraft in a high altitude environment. U.S. FAA Airplane Upset Recovery Training Aid, Revision 2, 443 pages, 25.8 MB A third revision dealing with transport category aircraft was released in February 2017, and is available on the FAA's website.

In April 2015, the FAA issued an Advisory Circular describing a detailed program of Upset Prevention and Recovery Training (UPRT) for pilots. Although the advisory circular was directed primarily at Part 121 air carriers, i.e. airlines, it encouraged all airplane operators, pilot schools, and training centers to implement UPRT.

The FAA later mandated that after 12 March 2019 all high fidelity full flight simulators used by Part 121 air carriers must be specifically qualified to conduct Upset Prevention and Recovery Training intended to prepare pilots to recover from aircraft upset incidents, including advanced maneuvers.

Detailed definition

From: The FAA's Pilot Guide to Airplane Upset Recovery.

An airplane upset is defined by the FAA as "an airplane in flight unintentionally exceeding the parameters normally experienced in line operations or training. This includes:

• Pitch attitude greater than 25 degrees nose up;

• Pitch attitude greater than 10 degrees nose down;

• Bank angle greater than 45 degrees; or

• Within the above parameters, but flying at airspeeds inappropriate for the conditions."

In other words, the airplane is not behaving normally or as intended, and accordingly will be approaching unsafe parameters.

The exact definition of aircraft upset varies between documents and training programs. For example, the British Royal Aeronautics Society states: "An upset is not necessarily a departure from controlled flight (i.e. a stall/spin) but it also includes abnormal attitudes and gross over/under-speed conditions." The Accident Investigation Division of aerospace technology company Calspan holds that the generally accepted industry guidelines for aircraft upset are incomplete in that they only take into consideration aircraft attitude and airspeed. Such expanded definitions are intended to more fully capture the maneuvers, events, conditions, and circumstances that the record has shown lead to loss of control.

Jet upset

The related category of "jet upset"–where a jet airliner is 'upset' and ends up in a high-speed dive–is defined by Calspan as: an airplane unintentionally exceeding the parameters normally experienced in line operations or a control failure or disturbance that alters the normal response of the airplane to pilot input such that the pilot must adopt an alternate control strategy to regain and sustain controlled flight.

Normal flight parameters are defined as: Pitch attitude between 25° nose-up and 10° nose-down. Bank angle less than 45°. Airspeed versus maneuver loading within the normal flight envelope.

Jet upset was almost unknown in the days of piston-driven propeller airliners since they lacked the swept-back wings, jet engines, and movable horizontal stabilizers that are unique to jet airliners. With the phasing out of piston-driven propeller airliners, the phrase has gradually given way to "loss of control inflight", which includes, but is not limited to, the upset/high-speed dive type of accidents. The term jet upset was most heavily used in the 1960s and 1970s as the phenomenon was not well understood and was still being researched.Books listing for jet upset term Contemporary authors tend to group the phenomenon under loss of control.Books listing for loss of control term

There have been a variety of causes and contributing factors, in past jet upset accidents:

February 1959: Pan Am Flight 115, a Boeing 707, upset and went into a high-speed dive while cruising over the Atlantic at flight level 350. Control was not recovered until reaching 6,000 ft. After landing safely at Gander, extensive structural damage was found, but there were only a few minor injuries. The Captain was in the cabin when the autopilot disconnected without adequate warning to the First Officer, who was distracted with a "howgozit" report form. It wasn't until the first officer felt the stall buffet that he realized they were descending rapidly and about to turn upside down. He was unable to level the wings. Fortunately, the Captain was able to return to the cockpit and strap into his seat while enduring significant G-forces. He took over the controls, levelled the wings, and pulled out of the dive.|CAB Aircraft Accident Report|Pan Am B707, Over The Atlantic, between London and Gander, February 3, 1959 February 1963: Northwest Airlines Flight 705, a Boeing 720B, was hit with a powerful updraft while trying to fly between thunderstorms shortly after takeoff, and suddenly began climbing at 9,000 ft. per minute while climbing through 17,000 ft. The nose pitched up so high that the pilot reacted by using full nose-down trim on the horizontal stabilizer while simultaneously pushing the elevators to the full-down position. Then an equally powerful downdraft hit the plane and it went straight down in a matter of seconds. The pilot then pulled back on the yoke, moving the elevators to the full-up position. This imposed high G-load on the plane, resulting in binding of the horizontal stabilizer jackscrew such that it remained in a full trimmed down position. The plane came apart in the air, before hitting the ground.|CAB Aircraft Accident Report|NWA B720B, Everglades, near Miami, February 12, 1963 July 1963: United Airlines Flight 746, a Boeing 720-022 (C/N 18045, Registration N7213U), was upset while climbing through FL 370 near O'Neill, Nebraska, resulting in a high-speed dive until recovery at 14,000 ft. The plane encountered all of severe turbulence, downdrafts, and updrafts, with turbulence causing the plane to stall as it was approaching the coffin corner of its flight envelope. After that near disaster the Stall and Mach buffet margins were widened on all jet aircraft in order to preclude a plane getting into the situation of severe turbulence narrowing the "coffin corner" margins so severely that the pilots do not have time to avoid a high altitude stall.|NASA Turbulence Penetration Study, pgs. 18 & 19|UAL B720, Upset near O'Neal Nebraska, July 12, 1963 November 1963: Trans-Canada Air Lines Flight 831, a DC-8-54F, crashed 5 minutes after takeoff near Montreal, leaving a crater in the ground and killing all 118 on board. Impact speed was over 500 mph. Investigators found the pitch trim compensator actuator was in the extended position and the horizontal stabilizer trim setting was at 1.65 to 2 degrees nosedown (both were improper positions for that stage of flight). "The probable cause of this accident could not be determined with certainty. Certain possible causes which were put forward could not be ruled out: 1) icing of the Pitot system; 2) failure of the vertical gyro; 3) an unprogrammed and unnoticed extension of the pitch trim compensator." February 1964: Eastern Air Lines Flight 304, a DC-8, crashed into Lake Pontchartrain about 5 minutes after taking off from the New Orleans Moisant Airport and all 58 on board perished. Despite the water being only 20 ft. deep, only 60% of the wreckage was recovered because the breakup was so extensive. The flight data recorder tape was too damaged to help the analysis. Instead, the maintenance records of that plane and of other DC-8s were used to conclude that the pilots had trimmed the stabilizer to the full nose-down position to counter the excessive nose-up attitude that, in turn, was caused by a malfunctioning pitch trim compensator that had extended too far. Once the upset occurred, it was not possible to trim the horizontal stabilizer back to the nose-up position because of the severe G-forces generated by the pilots pulling back on the yoke after the upset. February 1985: China Airlines Flight 006, a Boeing 747SP, had its number 4 engine flame out while cruising at FL 410 over the Pacific Ocean. The captain ordered an attempt to restart the engine while remaining at flight level 410 and with the autopilot controlling the plane. He failed to use left rudder to counteract the asymmetrical thrust, and the plane rolled rapidly to the right and entered a high dive attitude and was unable to recover from the dive until emerging from the clouds at 11,000 ft. The plane exceeded the maximum operating airspeed (Vmo) twice during the dive. After recovery, the plane landed safely at San Francisco, but suffered major structural damage and two occupants received serious injuries.NTSB Report China Airlines Flight 006

Related accidents 3 March 1974 Turkish Airlines Flight 981 (cargo door failure, caused severing of essential flight control cables). 4 April 1979 TWA Flight 841 (Improper manipulation of flaps/slats by pilots; the plane high dived from 39,000 ft. to 5,000 ft in 63 seconds. Landed safely.)