188:. A pilot aiming for a 500-foot per minute descent, for example, may find themselves descending more rapidly than intended. They begin to apply up elevator until the vertical speed indicator shows 500 feet per minute. However, because the vertical speed indicator lags the actual vertical speed, the aircraft is actually descending at much less than 500 feet per minute. The pilot then begins applying down elevator until the vertical speed indicator reads 500 feet per minute, starting the cycle over. In this way, stabilizing vertical speed can be difficult due to constantly variable airspeed. In a controls sense, the oscillation is the result of reduced phase margin induced by the lag of the pilot's response. The problem has been mitigated in some cases by adding a latency term to the instruments – for example, to cause the climb rate indication to not only reflect the current climb rate, but also be sensitive to the rate of change of the climb rate.
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inadvertently commands an often increasing series of corrections in opposite directions, each an attempt to cover the aircraft's reaction to the previous input with an overcorrection in the opposite direction. An aircraft in such a condition can appear to be "porpoising" switching between upward and
252:) was on a high-speed taxi test when PIO caused the aircraft to veer off to the left of the runway. The test pilot decided to take off and landed safely after six minutes. After that unintentional maiden flight, the development team reduced the roll gain of the
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downward directions. As such it is a coupling of the frequency of the pilot's inputs and the aircraft's own frequency. In order to avoid any assumption that oscillation is necessarily the fault of the pilot, new terms have been suggested to replace
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when landing in Linköping, Sweden. Pilot-induced oscillation as a result of an over-sensitive, yet slow-response flight control system was determined to be the cause. Subsequently, the flight control system was redesigned.
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in comparison to the response rate of the aircraft itself. For example, an increase in power will not result in an immediate increase in indicated airspeed, nor will an increase in climb rate show up immediately on the
229:. A natural reaction to this is to push the nose down harder than one pulled it up, but then the pilot ends up staring at the ground. An even larger amount of up elevator starts the cycle over again.
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Witte, Joel B., An
Investigation Relating Longitudinal Pilot-Induced Oscillation Tendency Rating To Describing Function Predictions For Rate-Limited Actuators
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Pilot-induced oscillations may be the fault of the aircraft, the pilot, or both. It is a common problem for inexperienced pilots, and especially
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make such oscillations more probable for pilots than for automobile drivers. An attempt to cause the aircraft to climb, say, by applying up-
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factors that is analyzed, with the aircraft being graded by an established scale (chart at right).
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sustained or uncontrollable oscillations resulting from efforts of the pilot to control the aircraft
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DEPARTMENT OF DEFENSE INTERFACE STANDARD, Flying qualities of piloted airplanes, Washington, D.C.
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in
California. This crash was linked to actuator rate limiting, causing the pilot,
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On 20 January 1974, a YF-16 (a development prototype for what was to become the
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Video of Space
Shuttle Enterprise landing with PIO during a test flight (NASA)
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Pilot-induced oscillation rating scale, with start position at bottom left.
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Pilot-induced oscillation was blamed for the 1992 crash of the prototype
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335:(July 1995). "Pilot-Induced Oscillations and Human Dynamic Behavior".
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can result in the plane getting dangerously slow and threatening to
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are close together in so called "short coupled" aircraft. During
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The most dangerous pilot-induced oscillations can occur during
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computer to eliminate similar PIO during takeoff or landing.
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While pilot-induced oscillations often start with fairly low
360:"That Time When the F-16 Accidentally Had Its First Flight"
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program. The problem is most acute when the wing and
49:. Unsourced material may be challenged and removed.
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387:, p. xvii, 2002, University Press of Kentucky,
236:, which can adequately be treated with small
321:https://apps.dtic.mil/sti/pdfs/ADA424366.pdf
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210:, pilot-induced oscillation is one of the
159:pilot-assisted (or augmented) oscillations
132:(PIOs), as defined by MIL-HDBK-1797A, are
109:Learn how and when to remove this message
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410:Video of an F-8 Landing with PIO (NASA)
385:Wingless Flight: The Lifting Body Story
339:. Dryden Space Flight Research Center.
179:Another factor is the response rate of
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419:Aircraft Owners and Pilots Association
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250:General Dynamics F-16 Fighting Falcon
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358:Mizokami, Kyle (23 January 2020).
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58:"Pilot-induced oscillation"
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383:Reed, Lister, Yaeger,
277:Edwards Air Force Base
136:. They occur when the
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