ashfordeOU Stall Characteristics Testing (flight-test-operations/envelope/stall-characteristics-testing)
Use when the task is the stall characteristics flight test: stall test matrix, entry techniques, stall warning onset, natural versus accelerated stall, and recovery characteristics.
Domain quick reference
- Stall test matrix: repeat each stall point in the clean, takeoff, and landing configurations, at idle and at maximum continuous power, and at the aft and forward c.g. limits; the aft c.g. condition is the critical one for stall characteristics.
- Entry techniques: the natural stall is entered wings level with a gradual deceleration of about one knot per second (0.5144 m/s^2) holding the trim attitude; the power-on stall adds climb power and a nose-up attitude; the turning stall is entered in a coordinated bank so the stall occurs at a higher speed; the accelerated stall is entered at an elevated load factor n, so the wing stalls at V = Vs * sqrt(n) where Vs is the 1g stall speed.
- Stall warning (FAR 25.207 / CS-25.207 context, paraphrased): the warning must be clear and distinct, either natural aerodynamic warning or an artificial device (stick shaker, horn), and must begin at a speed at least five percent above the stalling speed, or three knots, whichever is greater, in every configuration.
- Natural stall versus accelerated stall: the natural stall develops at 1g during a slow deceleration, with buffet, pitch break, and possible wing drop as first evidence; the accelerated stall is reached at the same CL_max but at a higher dynamic pressure and speed, and it probes high-AOA behavior, roll-off, and departure resistance before the normal stall regime.
- Recovery characteristics (FAR 25.203 / CS-25.203 context, paraphrased): at stall the aeroplane must show no excessive pitch-up, no uncontrollable rolling or yawing, and no tendency to spin or depart; recovery must be prompt with normal use of the flight controls (power reduction, pitch down, wings level) and with a limited altitude loss.
Workflow
- Build the stall test matrix: configurations, power settings, and c.g. conditions per test point.
- Compute the entry load factor for a turning stall with level_turn_load_factor(bank_deg) and the corresponding stall speed with accelerated_stall_speed(vs1g, load_factor).
- Derive the required warning speed with stall_warning_speed(vs1g, margin) and check the observed warning onset with stall_warning_on_time(warning_speed, vs1g, margin).
- Size the entry deceleration with entry_deceleration_time(entry_speed, stall_speed, decel_rate).
- Judge the observed recovery with stall_recovery_verdict(altitude loss, pitch-up, roll-off) and gate the stall test program on the verdict.
Pitfalls
- Calling the turning stall speed the 1g stall speed: in a banked turn the wing stalls at V = Vs * sqrt(n) with n = 1/cos(bank); a 60 degree bank doubles the load factor and raises the stall speed by about 41 percent.
- Entering the accelerated stall with a rapid pull instead of a stabilized entry: the load factor must be held and the deceleration controlled, otherwise the observed speed and angle of attack do not represent the steady accelerated stall.
- Treating stick shaker onset as the stall itself: the shaker is a warning device that must fire ahead of the stall with margin; the stall evidence is buffet, pitch break, or roll-off.
- Checking the warning margin in only one configuration: the warning onset requirement applies in every configuration and power setting in the matrix.
- Ignoring the aft c.g. condition: stall and recovery behavior degrade toward the aft c.g. limit, so a clean test at the forward c.g. hides the critical case.
- Reporting altitude loss without the recovery procedure used: the recovery altitude loss only means something when power reduction and pitch-down are applied promptly and consistently.
- Passing zero or negative inputs to the logic functions; the module raises ValueError instead of returning a meaningless speed, time, or verdict.
Behavior contract (gate 3)
The accelerated stall speed, level turn load factor, warning onset, entry deceleration, and recovery verdict logic is exercised by the gate 3 contract test: scripts/test_stall_characteristics_testing.py against scripts/stall_characteristics_testing_logic.py (stdlib unittest, offline). Run: python3 scripts/test_stall_characteristics_testing.py
Compliance
- Standards referenced, not reproduced: FAR-25 is US government work (public domain) and CS-25 is a free EASA download; the stall entry techniques, warning margin, and recovery requirements are common flight test methodology, summary-only per standards-map.yaml.
- compliance: STANDARDS-REF, gated: false.