FA-65971 / Aviation weight and balance / Open access

Shift weight divided by the destination arm · case 01

Required shift weights are far too small for aft stations and do not depend on where the load comes from.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The divisor is the destination arm rather than the distance the load actually travels.

THE FAILURE

The divisor is the destination arm rather than the distance the load actually travels.

Unsuccessful approach: Measuring the distance from the current CG to the destination ignores the origin station.

Case contract

Input [total lb, current CG, target CG, from-station arm, to-station arm]. Weight to move = W*dCG/dArm, rounded UP to a whole pound after clearing float noise at 6 decimals. Same station -> 'ERR_SAME_STATION'; zero dCG -> 0; a move that shifts CG the wrong way -> 'ERR_DIRECTION'.

Why this case matters

The weight-shift formula moves existing load between stations without changing total weight; the answer must be conservative (rounded up).

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    W, cg0, cg1, a_from, a_to = x
    if a_from == a_to: return 'ERR_SAME_STATION'
    dcg = cg1 - cg0
    darm = a_to - a_from
    if dcg == 0: return 0
    if (dcg > 0) != (darm > 0): return 'ERR_DIRECTION'
    moved = W * dcg / a_to
    return math.ceil(round(moved, 6))
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['baggage moved aft', [2400, 40.0, 41.1, 70.0, 120.0], 53], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2610, 46.5, 45.0, 140.0, 60.0], 49], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 69.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [3980, 45.3, 44.23, 41.8, 92.7], 'ERR_DIRECTION'], ['sampled case 2', [2707, 38.32, 40.1, 125.8, 85.0], 'ERR_DIRECTION'], ['sampled case 3', [3239, 40.39, 40.5, 103.2, 113.0], 37]], [['baggage moved aft', [2400, 40.0, 41.2, 70.0, 120.0], 58], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2620, 46.5, 45.0, 140.0, 60.0], 50], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 68.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [2415, 40.34, 38.4, 91.5, 122.3], 'ERR_DIRECTION'], ['sampled case 2', [3730, 42.18, 40.8, 132.4, 79.3], 97], ['sampled case 3', [2931, 40.9, 40.9, 127.0, 108.6], 0]], [['baggage moved aft', [2400, 40.0, 41.3, 70.0, 120.0], 63], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2630, 46.5, 45.0, 140.0, 60.0], 50], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 67.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [3390, 43.8, 43.8, 81.2, 142.7], 0], ['sampled case 2', [2280, 42.43, 43.6, 91.3, 32.9], 'ERR_DIRECTION'], ['sampled case 3', [3550, 38.5, 38.5, 60.9, 57.1], 0]], [['baggage moved aft', [2400, 40.0, 41.4, 70.0, 120.0], 68], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2640, 46.5, 45.0, 140.0, 60.0], 50], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 66.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [2103, 45.94, 44.79, 82.0, 59.6], 108], ['sampled case 2', [1930, 43.1, 41.2, 104.4, 84.0], 180], ['sampled case 3', [2160, 40.97, 40.7, 113.1, 93.1], 30]], [['baggage moved aft', [2400, 40.0, 41.5, 70.0, 120.0], 72], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2650, 46.5, 45.0, 140.0, 60.0], 50], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 65.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [2243, 42.7, 42.6, 141.2, 133.0], 28], ['sampled case 2', [3954, 45.3, 43.62, 97.4, 126.8], 'ERR_DIRECTION'], ['sampled case 3', [3960, 41.6, 42.67, 35.8, 103.5], 63]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
baggage moved aft	`22`	`53`	Failed
exact whole-pound shift	`7`	`10`	Failed
shift forward	`-65`	`49`	Failed
wrong direction request	`ERR_DIRECTION`	`ERR_DIRECTION`	Passed
already at target	`0`	`0`	Passed
same station	`ERR_SAME_STATION`	`ERR_SAME_STATION`	Passed
sampled case 1	`ERR_DIRECTION`	`ERR_DIRECTION`	Passed
sampled case 2	`ERR_DIRECTION`	`ERR_DIRECTION`	Passed
sampled case 3	`4`	`37`	Failed

SHA-256 / 3b6439efb0ae155d85bff03ee0f976181c30048ff7d43ac9db4d99ea9bcd0a74

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    W, cg0, cg1, a_from, a_to = x
    if a_from == a_to: return 'ERR_SAME_STATION'
    dcg = cg1 - cg0
    darm = a_to - a_from
    if dcg == 0: return 0
    if (dcg > 0) != (darm > 0): return 'ERR_DIRECTION'
    moved = W * dcg / (a_to - cg0)
    return math.ceil(round(moved, 6))
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['baggage moved aft', [2400, 40.0, 41.1, 70.0, 120.0], 53], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2610, 46.5, 45.0, 140.0, 60.0], 49], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 69.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [3980, 45.3, 44.23, 41.8, 92.7], 'ERR_DIRECTION'], ['sampled case 2', [2707, 38.32, 40.1, 125.8, 85.0], 'ERR_DIRECTION'], ['sampled case 3', [3239, 40.39, 40.5, 103.2, 113.0], 37]], [['baggage moved aft', [2400, 40.0, 41.2, 70.0, 120.0], 58], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2620, 46.5, 45.0, 140.0, 60.0], 50], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 68.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [2415, 40.34, 38.4, 91.5, 122.3], 'ERR_DIRECTION'], ['sampled case 2', [3730, 42.18, 40.8, 132.4, 79.3], 97], ['sampled case 3', [2931, 40.9, 40.9, 127.0, 108.6], 0]], [['baggage moved aft', [2400, 40.0, 41.3, 70.0, 120.0], 63], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2630, 46.5, 45.0, 140.0, 60.0], 50], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 67.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [3390, 43.8, 43.8, 81.2, 142.7], 0], ['sampled case 2', [2280, 42.43, 43.6, 91.3, 32.9], 'ERR_DIRECTION'], ['sampled case 3', [3550, 38.5, 38.5, 60.9, 57.1], 0]], [['baggage moved aft', [2400, 40.0, 41.4, 70.0, 120.0], 68], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2640, 46.5, 45.0, 140.0, 60.0], 50], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 66.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [2103, 45.94, 44.79, 82.0, 59.6], 108], ['sampled case 2', [1930, 43.1, 41.2, 104.4, 84.0], 180], ['sampled case 3', [2160, 40.97, 40.7, 113.1, 93.1], 30]], [['baggage moved aft', [2400, 40.0, 41.5, 70.0, 120.0], 72], ['exact whole-pound shift', [3000, 42.0, 42.3, 50.0, 140.0], 10], ['shift forward', [2650, 46.5, 45.0, 140.0, 60.0], 50], ['wrong direction request', [2500, 40.0, 41.0, 120.0, 65.0], 'ERR_DIRECTION'], ['already at target', [2300, 43.2, 43.2, 70.0, 120.0], 0], ['same station', [2300, 43.2, 44.0, 95.0, 95.0], 'ERR_SAME_STATION'], ['sampled case 1', [2243, 42.7, 42.6, 141.2, 133.0], 28], ['sampled case 2', [3954, 45.3, 43.62, 97.4, 126.8], 'ERR_DIRECTION'], ['sampled case 3', [3960, 41.6, 42.67, 35.8, 103.5], 63]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
baggage moved aft	`33`	`53`	Failed
exact whole-pound shift	`10`	`10`	Passed
shift forward	`-290`	`49`	Failed
wrong direction request	`ERR_DIRECTION`	`ERR_DIRECTION`	Passed
already at target	`0`	`0`	Passed
same station	`ERR_SAME_STATION`	`ERR_SAME_STATION`	Passed
sampled case 1	`ERR_DIRECTION`	`ERR_DIRECTION`	Passed
sampled case 2	`ERR_DIRECTION`	`ERR_DIRECTION`	Passed
sampled case 3	`5`	`37`	Failed

SHA-256 / eebd2f6bc0aa42397ca8c69baa93aa9d5f2f4a2bea340bb07187f19f9c656fd1

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 9 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic toy loading model with stipulated constants; it is not an approved aircraft flight manual procedure and makes no claim of regulatory conformance. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:47:39.115907+00:00.

Case digest / ddf1a0d333cbb339c84d7f54bede47f3ad32c7347bad1ddb920272e0b05f8a27