Aircraft upset

From Wikipedia, the free encyclopedia

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.[1] Loss of control may be due to excessive altitude for the airplane's weight, turbulent weather, pilot disorientation, or a system failure.[2][3]

The U.S. NASA Aviation Safety Program[2][3] defines upset prevention and upset recovery as to prevent 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.[1] NTSB data for 1994–2003 count 32 accidents and more than 2,100 lives lost worldwide.[4]


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. NTSB stated that prior to the crash they "had issued a series of safety recommendations over a 24-year period, asking the 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."[5]

Some carriers did implement their own voluntary training programs, following those accidents, and the NTSB regarded those programs as "excellent".[5]

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".[1][5]

In 2004, the U.S. FAA issued its first Airplane Upset Recovery Training Aid.[6] The second revision of that document was released in 2008 and is available at the FAA's website.[7]

New FAA rules are expected to be finalized in 2010, requiring specific training for pilots to recover from aircraft upset incidents.[1] New training programs may be known under the term advanced maneuver – upset recovery training (AM-URT).[1]

In 2009, the Royal Aeronautical Society formed a new group of experts, who will form documentation to allow better simulations of aircraft upset conditions, and thus better training programs.[8] Upset Prevention and Recovery Training (UPRT) provider, Aviation Performance Solutions, joined the Royal Aeronautical Society team in 2009 to help develop global solutions for overcoming Loss of Control In-Flight (LOC-I), the possible resulting flight condition following an airplane upset.[9]

Detailed definition[edit]

From: The FAA's Pilot Guide to Airplane Upset Recovery.[3][7]

An airplane upset is defined as an airplane in flight unintentionally exceeding the parameters normally experienced in line operations or training. In other words, the airplane is not behaving normally or as intended; accordingly it will be approaching unsafe parameters.

Exact definition varies between documents and training programs. The 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."[10]

Calspan, which has been involved with upset research and training since teaming with NASA in 1997, holds that the generally accepted industry guidelines are incomplete in that they only take into consideration aircraft attitude and airspeed. Jet Upset 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:

This expanded definition is intended to more fully capture the maneuvers, events, conditions, and circumstances that the record has shown lead to LOC.[11]

Jet upset[edit]

The phrase jet upset refers to accidents and incidents (some crashed and some recovered, usually with significant damage to the structure), where a jet airliner was "upset" and ended up in a high-speed dive. That phenomenon was almost unknown in the days of piston-driven propeller airliners, which is why those accidents were referenced as "jet" upsets: because it was a repeated phenomenon that was unique to jet airliners, with swept-back wings, jet engines and movable horizontal stabilizers, none of which were found on the piston/propeller airliners. With the phasing out of piston-driven propeller airliners, that 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.[12] Contemporary authors tend to group the phenomenon under loss of control.[13]

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

  • February 1959: Pan Am Flight 115, a Pan American World Airways 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, leveled the wings and pulled out of the dive.[14]
  • February 1963: Northwest Airlines Flight 705 – A Northwest Airlines Boeing 720B was hit with a powerful updraft (it suddenly began climbing at 9,000 ft. per minute) while climbing through 17,000 ft as it tried to fly between thunderstorms shortly after takeoff. The nose pitched up so high that the pilot reacted by using full nose-down trim on the horizontal stabilizer (HS), while simultaneously pushing the elevators to the full down position. Then, an equally powerful down draft 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.[15]
  • July 1963: United Airlines Flight 746 Boeing 720-022 (C/N 18045, Registration N7213U), while climbing through FL 370 near O'Neill, Nebraska, was upset and resulted in a high-speed dive until recovery at 14,000 ft. The plane encountered severe turbulence, downdrafts and updrafts, which caused the plane to stall. The plane was approaching the coffin corner of its flight envelope, when the turbulence was encountered. After that near disaster, the stall mach buffet margins were widened on all jet aircraft, to preclude a plane getting into that situation again, where severe turbulence narrows the "coffin corner" margins so severely that the pilots do not have time to avoid a high altitude stall.[16]
  • November 1963: Trans-Canada Air Lines Flight 831 – All 118 on board a Trans-Canada Airlines DC-8-54F were killed, when the plane crashed 5 minutes after takeoff near Montreal, leaving a crater in the ground. 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."[17]
  • February 1964: Eastern Air Lines Flight 304 – An Eastern Airlines DC-8 crashed into Lake Pontchartrain about 5 minutes after taking off from the New Orleans Moisant Airport. All 58 on board perished. The water was only 20 ft. deep, yet 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, they used the maintenance records of that plane, and of other DC-8s, 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 HS back to the nose-up position, because of the severe G-forces generated by their pulling back on the yoke after the upset.[citation needed]
  • February 1985: China Airlines Flight 006: The number 4 engine flamed out on a China Airlines Boeing 747SP, 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. He was unable to recover from the dive until below 11,000 ft. when they emerged from the clouds. The plane exceeded the maximum operating airspeed (Vmo) twice, during the dive. After recovery, the plane landed safely at San Francisco. It suffered major structural damage and 2 occupants received serious injuries.[18]

Related accidents[edit]

See also[edit]


Public Domain This article incorporates public domain material from Airplane Upset Recovery Training Aid (PDF). Federal Aviation Administration.

  1. ^ a b c d e "Getting control of LOC". Flightglobal. January 27, 2009. Retrieved December 1, 2015.
  2. ^ a b "Archived copy" (PDF). Archived from the original (PDF) on 2011-10-30. Retrieved 2009-01-31.{{cite web}}: CS1 maint: archived copy as title (link)
  3. ^ a b c Note: 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.
  4. ^[permanent dead link]
  5. ^ a b c USAir Flight 427 Accident report, pg. 283 Archived March 3, 2016, at the Wayback Machine
  6. ^ "Airplane Upset Recovery / High Altitude Operations". Archived from the original on February 27, 2009.
  7. ^ a b "U.S. FAA Airplane Upset Recovery Training Aid, Revision 2" (PDF). Retrieved 2019-10-28. U.S. FAA Airplane Upset Recovery Training Aid, Revision 2, 443 pages, 25.8 MB
  8. ^ Croft, John (2009-11-14). "Upset training group to hold first meeting". Air Transport Intelligence news. Archived from the original on 19 November 2009. Retrieved 2009-11-15. The devices are not currently required to perform accurately in the realm outside of the flight or wind tunnel test points, nor are pilots currently trained to fly in those conditions.
  9. ^ Mark, Rob (June 5, 2018). "APS Creates Critical Issues Addendum to NTSB LOC-I Roundtable". Flying Magazine. Retrieved August 16, 2018.
  10. ^ Aeroplane Upset Recovery Training, History, Core Concepts & Mitigation (PDF). London: Royal Aeronautics Society. 2010. Retrieved December 17, 2014.
  11. ^ Priest, James; Ernisse, Brian; McMahon, Ryan (August 2010). "Comprehensive In-Flight Simulation Based Advanced Maneuver & Upset Recovery Training Study". AIAA Guidance, NAvigation, and Control Conference. doi:10.2514/6.2010-8009. ISBN 978-1-60086-962-4. S2CID 61726759. Retrieved December 17, 2014.
  12. ^ Books listing for jet upset term[permanent dead link]
  13. ^ Books listing for loss of control term[permanent dead link]
  14. ^ |CAB Aircraft Accident Report|Pan Am B707, Over The Atlantic, between London and Gander, February 3, 1959
  15. ^ |CAB Aircraft Accident Report|NWA B720B, Everglades, near Miami, February 12, 1963
  16. ^ |NASA Turbulence Penetration Study, pgs. 18 & 19|UAL B720, Upset near O'Neal Nebraska, July 12, 1963
  17. ^ "ASN Aircraft accident Douglas DC-8-54F CF-TJN Ste-Thérèse-de-Blainville, QC". Archived from the original on 2013-10-20. Retrieved 2013-07-08.
  18. ^ NTSB Report China Airlines Flight 006 Archived June 17, 2016, at the Wayback Machine
  • Moynahan, Brian (1978). Airport International. Pan. p. 184.

Further reading[edit]

  • Dismukes, Key, Benjamin A. Berman and Loukia D. Loukopoulos. The Limits of Expertise. Aldershot: Ashgate, 2007. ISBN 978-0-7546-4965-6

External links[edit]