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Cited by 77Biomimetic flight and propulsion mechanismsFluid dynamics and aerodynamics studiesAerospace and Aviation Technology

Diving-Flight Aerodynamics of a Peregrine Falcon (Falco peregrinus)

Open access
Ponitz, Benjamin, Schmitz, Anke, Fischer, Dominik, Bleckmann, Horst, Brücker, Christoph·2014·PLoS ONE
DOI 10.1371/journal.pone.0086506PMC PMC3914994
Open this paper in CoChat — free accountOpen PDF

Abstract

This study investigates the aerodynamics of the falcon Falco peregrinus while diving. During a dive peregrines can reach velocities of more than 320 km h⁻¹. Unfortunately, in freely roaming falcons, these high velocities prohibit a precise determination of flight parameters such as velocity and acceleration as well as body shape and wing contour. Therefore, individual F. peregrinus were trained to dive in front of a vertical dam with a height of 60 m. The presence of a well-defined background allowed us to reconstruct the flight path and the body shape of the falcon during certain flight phases. Flight trajectories were obtained with a stereo high-speed camera system. In addition, body images of the falcon were taken from two perspectives with a high-resolution digital camera. The dam allowed us to match the high-resolution images obtained from the digital camera with the corresponding images taken with the high-speed cameras. Using these data we built a life-size model of F. peregrinus and used it to measure the drag and lift forces in a wind-tunnel. We compared these forces acting on the model with the data obtained from the 3-D flight path trajectory of the diving F. peregrinus. Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon's body, which suggests local regions with separation of flow. High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions, where flow separation in the model falcon occurred.

AI snapshot

Written from the paper’s full text.

TL;DR

The study combined 3-D flight-path tracking of trained peregrine falcons diving along a dam with wind-tunnel force and flow measurements on a life-size falcon model. It derived the angle of attack at maximum diving speed in the experiment and found flow-separation regions on the model that correspond to popped-up feathers on the living falcon.

Key findings

  • During the analyzed dive, the falcon reached a maximum velocity of 22.5 m s−1 (80 km h−1), with phase-1 acceleration of 6.8 m s−2 from 15.0 to 22.5 m s−1 and a flight path angle of 50.75° at maximum diving velocity.
  • For equilibrium flight at maximum speed, the wind-tunnel polar diagram gave an angle of attack of α = 5°, with lift coefficient CL = 0.0870 and drag coefficient CD = 0.0941; at α = 0°, CL = 0.0445 and CD = 0.0860, corresponding to a 96% increase in lift and a 10% increase in drag.
  • Oil-painting flow visualization and PIV revealed local flow separation on the model, including on the head and in the last third of the body; high-resolution images of the diving falcon showed feathers popped-up in the equivalent regions.
  • The authors suggest these popped-up feathers may act as passive flow-control units that prevent local flow separation during diving.

Methods

  • Flight experiments used adult male and female *Falco peregrinus* trained to dive in front of the 60 m high Olef-Talsperre dam wall; 35 flights were recorded, and one representative flight was analyzed in detail. The investigated falcon’s mass was 0.5 kg.
  • A stereo high-speed camera system recorded the 3-D flight path at 400 Hz for 6 s, with a third high-resolution camera capturing body and wing shape; velocity and acceleration were obtained after moving-spline interpolation.
  • A one-to-one polyvinyl chloride falcon model was built from a modified stuffed female peregrine and tested in a Göttingen-type wind tunnel with force balances, oil-painting flow visualization, and PIV at free-stream velocities including 22.5 m s−1.

Limitations

  • The paper states that due to the low height of the dam wall, falcons only reached velocities up to 80 km h−1 in the experiments; they showed the classical diamond shape but not the wrap dive vacuum pack, and further experiments are needed for speeds above 80 km h−1.
  • Evident from the text: although 35 flights were recorded, only one representative flight was analyzed in detail for acceleration and body-shape information.
  • Evident from the text: the wind-tunnel model was based on a stuffed female peregrine whose wings were manually modified to match a diving image, and the force/flow analysis focused on the equilibrium condition with zero acceleration.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1371/journal.pone.0086506

Cites

31 of 31 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

1 of 19 cited sources checked · 1 supported · 0 flagged

  • Findingown data

    A second change of flight direction at the pull out phase led to an acceleration of 9.3 m s−2 at t = 3.2 s.

    “A second change of flight direction, which occurred at the pull out phase, led to an acceleration of 9.3 m s−2 at t = 3.2 seconds.”
    Quote in the paperNot a substantial claim
  • Findingown data

    Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon's body, which suggests local regions with separation of flow.

    “Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon’s body, which suggests local regions with separation of flow.”
    Quote in the paperSubstantial claim
  • Findingown data

    High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions where flow separation in the model falcon occurred.

    “High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions, where flow separation in the model falcon occurred.”
    Quote in the paperSubstantial claim
  • Findingown data

    The force balances measurements showed an abrupt decrease in drag at a Reynolds number where the boundary layer became turbulent.

    “Our measurements showed an abrupt decrease in drag at a Reynolds number (Fig. 6) where the boundary layer became turbulent.”
    Quote in the paperSubstantial claim
  • Findingown data

    The geometry of the falcon at maximum flight velocity in the experiment was V-shaped.

    “The geometry of the falcon in this flight situation was V-shaped (Fig. 4).”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim. 19
  • May combine two claims. 18
  • The quote only partly states this claim. 2

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    An error analysis of stereo techniques was carried out according to a procedure given by Lawson.

    “For that reason an error analysis of stereo techniques was carried out according to a procedure given by Lawson [21].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [21] NJ Lawson, 1997, Three-dimensional particle image velocimetry: error analysis of stereoscopic techniques. Meas. Sci. Technol source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    After 180 seconds of air flow, near-surface streamlines on the model surface became visible.

    “After 180 seconds of air flow the near-surface streamlines on the surface of the model became visible.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    After a short period of nearly constant diving speed, the falcon decelerated and within 1.2 s its velocity decreased from 22.5 m s−1 to 19.4 m s−1.

    “After a short period of nearly constant diving speed (2) the falcon decelerated (3) and within 1.2 s its velocity decreased from 22.5 m s−1 to 19.4 m s−1.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    During the pull out phase the falcon significantly decreased its flight path angle θ and most notably its velocity.

    “During the pull out phase the falcon significantly decreased its flight path angle θ and most notably its velocity.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The flight was divided into six phases: acceleration/diving (0 to 1.1 s), transient roughly constant speed (1.1 to 1.3 s), deceleration and flight path correction (1.3 to 2.3 s), pull out (2.3 to 3.5 s), landing constant speed (3.5 to 5.0 s), and landing deceleration with touchdown (5.0 to 6.8 s).

    “- acceleration/diving phase (0 to 1.1 s); - transient phase with roughly constant speed (1.1 to 1.3 s); - deceleration and flight path correction phase (1.3 to 2.3 s); - pull out phase (2.3 to 3.5 s); - landing phase with constant speed (3.5 to 5.0 s); - landing phase with deceleration and touchdown (5.0 to 6.8 s).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The first prominent change of flight direction (pull out) caused a maximum acceleration of 11.5 m s−2 at t = 2.8 s, which is nearly 1.2 times the gravitation constant g.

    “This first prominent change of flight direction (pull out) caused a maximum acceleration of 11.5 m s- 2 at t = 2.8 s which is nearly 1.2 times the gravitation constant g (Fig. 10B).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    The mass of the investigated falcon was 0.5 kg.

    “The mass of the investigated falcon was 0.5 kg.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    At α = 0°, the lift coefficient was CL = 0.0445 and the drag coefficient was CD = 0.0860.

    “| Lift coefficient CL | 0.0445 | 0.0870 |”
    • Also stated in: § Wind Tunnel Investigations with a Life-size Model · plain
      “| Drag coefficient CD | 0.0860 | 0.0941 |”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    The falcons showed the classical diamond shape but not the wrap dive vacuum pack, i.e. their wings were not completely laid against their body.

    “As expected, they showed the classical diamond shape but not the wrap dive vacuum pack [17], i.e. their wings were not completely laid against their body.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [17] Seitz K (1999) Vertical flight. NAFA Journal: 68–72.

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    For a flight velocity of 22.5 m s−1 and an angle of attack of 5°, the lift coefficient was CL = 0.0870 and the drag coefficient was CD = 0.0941.

    “The corresponding values of lift and drag coefficients for the equilibrium flight phase at an angle of attack of α = 5° are given in Table 4.”
    • Also stated in: § Discussion · plain
      “For a flight velocity of 22.5 m s−1 and an angle of attack of 5° the lift coefficient was CL = 0.0870 and the drag coefficient was CD = 0.0941 (Table 4).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The lift coefficient at α = 5° was 96% higher and the drag coefficient was 10% higher than at α = 0°.

    “This was equal to a 96% increase for lift and a 10% increase for drag compared to the values obtained at a zero angle of attack (α = 0°).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    PIV was used for verification of oil-painting-based flow visualizations.

    “For the verification of the oil-painting-based flow visualizations we used the method of particle image velocimetry (PIV) [26].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [26] RJ Adrian, 1991, Particle-imaging techniques for experimental fluid mechanics. Annu. Rev, Fluid Mech source

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Calibration of the force balances was performed using defined loads and drag measurements on a sphere in a wind tunnel for different flow velocities.

    “Calibration of the force balances was performed using defined loads and using measurements of the drag forces on a sphere in a wind tunnel for different flow velocities.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    The drag crisis phenomenon was used to verify the force balances and to demonstrate the independence of measured drag and lift forces.

    “This phenomenon of the so-called ‘drag crisis’ [23], [24] was used to verify the force balances and to demonstrate the independence of measured drag and lift forces.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [23] E Achenbach, 1972, Experiments on the flow past spheres at very high Reynolds numbers. J. Fluid Mech source
    • cites [24] Schlichting H (1979) Boundary-Layer Theory. McGraw-Hill, New York n. 7th ed.

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    The front side of the dam wall points south ensuring optimal light conditions for image recordings; at noon shadowing effects were minimal.

    “The front side of the wall points to the south ensuring optimal light conditions for image recordings with high-speed cameras. At noon, shadowing effects were minimal.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Time stamps ensured synchronized observations between the third camera and the two high-speed cameras.

    “The position of this camera within the 3-D reconstruction space was also determined and time stamps ensured synchronized observations between the third camera and the both high-speed cameras.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The oil-painting method is typically applied to wind-tunnel experiments to visualize flow structure and location of possible separation regions at the surface of aerodynamic bodies.

    “This method is typically applied to wind-tunnel experiments to visualize the flow structure and the location of possible separation regions at the surface of aerodynamic bodies [18].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] FK Lu, 2010, Surface oil flow visualization. Eur. Phys, J. Special Topics source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Study design and conductreasoning

    Due to professional dive training by the falconer, all 35 flights exhibit nearly identical characteristics.

    “Due to the professional dive training by the falconer all 35 flights exhibit nearly identical characteristics.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims. The quote only partly states this claim.

    Study design and conductreasoning

    The ring buffer mode and manual trigger ensured that the entire flight was captured within a recording sequence.

    “This method ensured that the entire flight was captured within a recording sequence.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The force balances have an accuracy class C3 (0.02%).

    “This measurement device consists of three analog load cells (HBM PW15AH) with an accuracy class C3 (0.02%).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Peregrines are exposed to high mechanical loads.

    “This suggests that peregrines are exposed to high mechanical loads.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Peregrines maintain remarkable maneuverability at high speeds.

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    A cable connection between both cameras via BNC and TTL signal synchronization ensured a simultaneous frame capture.

    “A cable connection between both cameras via BNC (bayonet neill concelman) and TTL (transistor–transistor logic) signal synchronization ensured a simultaneous frame capture.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The verification of the qualitative visualisation results was done by comparing oil-painting structures with measured velocity fields gained with PIV.

    “The verification of the qualitative visualisation results was done by comparing oil-painting structures with measured velocity fields gained with the itative method named particle image velocimetry (PIV).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    During a dive, peregrines alter the shape of their wings; while accelerating, they move them closer and closer to their body.

    “During a dive, peregrines also alter the shape of their wings; while accelerating, they move them closer and closer to their body [10].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [10] DC Franklin, 1999, Evidence of disarray amongst granivorous bird assemblages in the savannas of northern Australia, a region of sparse human settlement, Biological Conservation source

  • May combine two claims.

    Study design and conductown data

    The cross-section ratio of the falcon model and the wind tunnel is 4.1%, so blockage effects are negligible.

    “The cross-section ratio of the falcon model and the wind tunnel amounts to 4.1%, so that blockage effects are negligible.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    PIV results were obtained by a cross-correlation algorithm and validated by range and moving average filters of the velocity vectors.

    “The results were obtained by a cross-correlation algorithm and subsequently validated by range and moving average filters of the velocity vectors.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    The distance between camera sensors and a reference point on the wall was determined by a laser-based distance sensor; for distances up to 250 meters the measuring error was ±1.0 mm.

    “The distance between the camera sensors and a reference point on the wall were determined by a laser-based distance sensor (BOSCH GLM 250 VF Professional). For distances up to 250 meters the measuring error was ±1.0 mm.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In the flight phase up to 240 km/h, the front part of the wings have a cupped-like profile.

    “This is followed by a tight vertical tuck of the wings up to speeds of 240 km h−1. In this flight phase the front part of the wings have a cupped-like profile [14], [15], [16], [9].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [14] Ratcliffe DA (1980) The peregrine falcon. Vermillion, S.D: Buteo Books.

      Not checked in the free run.

    • cites [15] K Hustler, 1983, Breeding biology of the peregrine falcon in Zimbabwe, Ostrich source
    • cites [16] VA Tucker, 1990, Body drag, feathers drag and interference drag of the mounting strut in a peregrine falcon, <italic>Falco peregrinus</italic>, Journal of Experimental Biology source

  • May combine two claims.

    Study design and conductown data

    Mean reprojection errors were 0.23 pixel in x- and 0.07 pixel in y-direction.

    “Mean values of reprojection errors were 0.23 pixel in x- and 0.07 pixel in y-direction.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    A moving-spline interpolation using a simple central difference scheme was applied to smooth the original data prior to taking the time-derivatives.

    “Therefore, a moving-spline interpolation using a simple central difference scheme was applied to smooth the original data prior to taking the time-derivatives (see Lüthi et al. [27]).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Lüthi et al. [27] B Lüthi, 2005, Lagrangian measurement of vorticity dynamics in turbulent flow. J. Fluid Mech source

  • May combine two claims.

    Study design and conductcitation

    The calibration process determined the internal parameters of each camera and the relative orientation among the cameras.

    “Within the calibration process the internal parameters of each camera as well as the relative orientation among the cameras were determined [20].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] Hartley R, Zisserman A (2003) Multiple view geometry in computer vision. 2<sup>a</sup> ed. Cambridge, UK, New York: Cambridge University Press. source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Nearly all bird species can alter the shape of their wings and thus change their aerodynamic properties.

    “Nearly all bird species can alter the shape of their wings and thus can change their aerodynamic properties [11], [12]”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [11] W Nachtigall, 1975, Vogelflügel und Gleitflug. Einführung in die aerodynamische Betrachtungsweise des Flügels, Journal für Ornithologie source
    • cites [12] Nachtigall W (1998) Der Gleitflug von Vögeln. Physik in unserer Zeit n. 1, 29. source

  • The quote only partly states this claim.

    Interpretationreasoning

    The boundary layer flow around the falcon was turbulent at the maximum diving speed of 22.5 m s−1.

    “Hence, the boundary layer flow around the falcon was turbulent at this speed.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    At the maximum speed reached in the experiment, the phase had zero acceleration, allowing the condition of equilibrium of the sum of aerodynamic forces with the gravitational force to be applied.

    “This phase with zero acceleration allowed us to apply the condition of equilibrium of the sum of aerodynamic forces with the gravitational force that should cancel out each other to zero.”
    Quote in the paperSubstantial claim
34 of 34

  • The paper relies on this without support.

    Exact measurements of acceleration forces, drag forces, flight path angles and the corresponding aerodynamics of the flow around the body have not been determined.

    “Although the nose-diving flight of peregrines has been investigated numerous times, exact measurements of acceleration forces, drag forces, flight path angles and the corresponding aerodynamics of the flow around the body have not been determined.”

  • The paper relies on this without support.

    The dive of a wild peregrine is a brief, rare event that takes place at unpredictable places and times, usually at a long distance from the observer.

    “The dive of a wild peregrine is a brief, rare event that takes place at unpredictable places and times, usually at a long distance from the observer.”

  • The paper relies on this without support.

    Peregrines maintain remarkable maneuverability at high speeds.

    “Peregrines are not only extremely fast flyers but also maintain remarkable manuverability at high speeds.”

  • The authors state this as an assumption.

    The specific arrangement of popped-up feathers prevents local flow separation on the falcon body during diving flight.

    “It is assumed that this specific arrangement of the feathers prevents local flow separation on the falcon body in nature.”
    “It is assumed that the presence of the popped-up feathers prevents this local flow separation during the diving flight of the peregrine falcon, similar to what has been shown to occur in experiments and simulations on airfoils covered with self-adaptive flaps (see [32], [33], [31], [34], [35], [36]).”
4 of 4

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Flight duration differs between the trajectory description and phase timings

    Minor

    The trajectory is described as covering the flight until landing over 6 s, whereas the listed landing phase extends to 6.8 s.

1 of 1

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. WS Clark, 1995, How fast is the fastest bird?, WildBird, 9, 42
  2. Seitz K (1999) Vertical flight. NAFA Journal: 68–72.

Cited by

Sorted by citations

Related

Authors
Ponitz, B., Schmitz, A., Fischer, D., Bleckmann, H., & Brücker, C.
Affiliations
  • TU Bergakademie Freiberg (DE)
  • University of Bonn (DE)
  • Justus-Liebig-Universität Gießen (DE)
Corresponding author
Ponitz, Benjamin
ORCID
Venue
PLoS ONE
Publisher
Public Library of Science (PLoS)
Published
2014-02-05
Volume
9
Issue
2
Pages
e86506
ISSN
1932-6203 (ISSN-L)
DOI
10.1371/journal.pone.0086506
PMC
PMC3914994
OpenAlex
W1986032999
Semantic Scholar
43b5a703a96f2eb4f23f9b250643a4511d315b95
Cited by
77
References
31
Citations by year
2026: 6 · 2025: 8 · 2024: 6 · 2023: 18 · 2022: 10 · 2021: 10 · 2020: 4 · 2019: 2 · 2018: 4 · 2017: 1 · 2016: 2 · 2015: 2 · 2014: 4
FWCI
4.43
Type
journal article
Language
en
Open access
Licence
Locations
  • PLoS ONE (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • City Research Online (City University London) (acceptedVersion)
  • Europe PMC (PubMed Central) (submittedVersion, cc-by)
  • PubMed Central (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Deutsche Forschungsgemeinschaft (BR 1494/21-1, BL 242/19-1)
Topics
  • Physical Sciences › Engineering › Aerospace Engineering › Biomimetic flight and propulsion mechanisms
  • Physical Sciences › Engineering › Computational Mechanics › Fluid dynamics and aerodynamics studies
  • Physical Sciences › Engineering › Aerospace Engineering › Aerospace and Aviation Technology
Keywords
Falco peregrinus, aerodynamics, drag force, lift force, flight path, body shape, flow separation, wind tunnel model, high-speed video, bird flight
MeSH terms
Animals, Flight, Animal, Models, Theoretical, Video Recording, Falconiformes

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

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Statistics and arithmetic are recomputed, not judged.

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