ADHD Friendly Stabcon Flashcards

Name the 5 dynamic modes.

Phugoid, short period, roll, spiral, Dutch roll.

Name the longitudinal modes.

Phugoid and short period.

Name the lateral modes.

Roll, spiral, Dutch roll.

What is phugoid?

Slow speed–altitude oscillation.

What is short period?

Fast pitch/angle-of-attack oscillation.

What is roll subsidence?

Roll rate decays without oscillating.

What is spiral mode?

Slow bank/heading change.

What is Dutch roll?

Coupled yaw and sideslip oscillation.

What is DATCOM?

Handbook estimating stability/control derivatives.

Does DATCOM replace testing?

No. Validate its estimates.

Define static stability.

Initial return tendency after disturbance.

Define dynamic stability.

Motion decays, persists, or grows.

Static stable, dynamic unstable?

Yes. Restoring force ≠ sufficient damping.

What is trim?

Forces and moments balanced.

What means stick-fixed?

Control deflections held fixed.

Define 6 degrees of freedom.

3 translations + 3 rotations.

What is an eigenvalue?

Natural motion's decay and frequency.

Real root part means?

Negative: decay. Positive: growth.

Imaginary root part means?

Oscillation frequency.

What is yaw damping?

Moment opposing yaw rate.

Define weathercock stability.

Tail aligns aircraft with airflow.

Define dihedral effect.

Sideslip causes rolling moment.

What is adverse yaw?

Yaw opposite commanded roll.

Why need pitch damping?

Reduces oscillation and pilot workload.

Why tolerate slow spiral divergence?

Pilot/autopilot can correct it.

Steady trim: angular rates?

p₀ = q₀ = r₀ = 0.

No roll or sideslip?

φ₀ = β₀ = 0.

Only forward motion?

Other velocities, rotations = 0.

Pure pitching: zero rates?

p = r = 0.

Pure rolling: zero rates?

q = r = 0.

Pure yawing: zero rates?

p = q = 0.

Controls fixed: perturbations?

Δδ = 0.

Unforced state-space model?

u(t) = 0.

Roll starts from rest?

p(0) = 0.

Neglect wing/fuselage contribution?

Set specified contributions to zero.

Neglect fuselage yaw effect?

Cnβ,wf = 0.

Neglect sidewash?

dσ/dβ = 0.

Neglect downwash gradient?

dε/dα = 0.

Neglect downwash lag?

Cmα̇ ≈ 0.

Full tail efficiency?

ηv = 1.

Ignore Mach drag effects?

CDu ≈ 0; retain 2CD₀.

Ignore Mach lift effects?

CLu ≈ 0; retain 2CL₀.

Thrust independent of speed?

CTu = 0.

Bilateral aircraft symmetry?

Ixy = Iyz = 0.

Assume Ixz = 0?

Ignore inertial roll–yaw coupling.

Only longitudinal motion?

Ignore lateral disturbances.

Only lateral motion?

Ignore longitudinal disturbances.

Phugoid approximation?

Angle of attack nearly constant.

Short-period approximation?

Δu ≈ 0.

Steady rolling response?

ṗ = 0; p may be nonzero.

Real root part η = 0?

No exponential decay or growth.

Real root part η < 0?

Amplitude decays.

Imaginary part ω = 0?

No oscillation.

Neglect body inertia?

Exclude body from I.

Ideal thin-airfoil slope?

a₀ = 2π/rad.

What tail area should count?

Use specified area convention.

Degrees with per-radian coefficients?

Convert degrees to radians.

Neglect β̇ derivatives?

Set β̇ coefficients to zero.

Asymmetric thrust: decoupled motion?

Not necessarily.

Stick-fixed means no damping?

No. Aerodynamic damping remains.

Wing aspect ratio?

AR = b²/S.

Taper ratio?

λ = ctip/croot.

Weight to mass?

m = W/g.

Lift equation?

Lift = Q S CL.

Drag equation?

Drag = Q S CD.

Rolling moment equation?

L = Q S b Cl.

Rolling moment coefficient?

Cl = L/(Q S b).

Pitching moment equation?

M = Q S c̄ Cm.

Yawing moment equation?

N = Q S b Cn.

Control derivative definition?

Clδ = ∂Cl/∂δ.

Small-angle lift change?

ΔCL ≈ CLα Δα.

Ideal 2D lift slope?

a₀ = 2π/rad.

Finite-wing lift slope?

a = a₀/[1+a₀/(πeAR)].

Small sideslip approximation?

β ≈ v/u₀.

Nondimensional roll rate?

p̂ = pb/(2V).

Nondimensional yaw rate?

r̂ = rb/(2V).

Roll-induced angle change?

Δα ≈ py/V.

Rectangular-wing roll damping?

Clp ≈ −a/6.

Differential-incidence roll control?

Clδ ≈ a/4.

Thin-plate roll inertia?

Ix ≈ mb²/12.

Rolling torque from forces?

Sum force × moment arm.

Plate mass equation?

m = density × volume.

Convert lbm to slugs?

Divide by 32.174.

Newton's yaw equation?

Iz ψ̈ = N.

Linear yaw coefficient?

ΔCn = CnβΔβ + Cnr r̂.

Fixed-pivot yaw relationships?

β ≈ −ψ; r = ψ̇.

Pure-yaw equation?

Izψ̈ + cψψ̇ + kψψ = 0.

Yaw restoring stiffness?

kψ = QS Bref Cnβ.

Yaw damping coefficient?

cψ = −QS Bref² Cnr/(2V).

Fixed-pivot angle relations?

Pitch: α≈θ. Yaw: β≈−ψ.

Steady-state calculation?

Set derivatives = 0.

Velocity to angle?

Δα≈Δw/u₀; Δβ≈Δv/u₀.

Mach-speed relation?

V = Ma.

Normalized speed derivative?

Cu = M(∂C/∂M).

Wing-strip lift force?

dF = Q c a Δα dy.

Initial roll acceleration?

ṗ(0) = Lδ δ.

Stabilizing dihedral sign?

Lβ < 0.

Yaw damping sign?

Nr < 0.

Directional stability sign?

Nβ > 0.

Typical roll-from-yaw sign?

Lr > 0.