Flying Qualities

Five-mode longitudinal and lateral-directional response from JET11 geometry, inertia, and stability derivatives.

Demonstration aircraft loaded. Import a JET11 file to use aircraft-specific data.

Selected mode—estimated

Short-period attitude response

Fast pitch and angle-of-attack motion of the solid aircraft model about the CG

Flight conditionKTAS—KIAS—Altitude—Dynamic pressure—Load factor—

t = 0.00 sδe = 0.0 deg

Short-period response

pitch attitude θ and elevator command δe

Short-period data reduction

Model interpretation

Mass moments of inertia

slug·ft²

JET predictions

Longitudinal derivatives (from JET11)

	Value	Use

Standards references

Open the local library documents:

These sources require program-specific tailoring. Simulator estimates are teaching results, not certification findings or formal risk acceptance.

Selected-mode standards

Live data reduction

Waiting for response samples.

Tail geometry

H-tail moment arm —V-tail moment arm —

Horizontal tail projection —Vertical tail projection —

Flying Qualities in AE 456

Course slide decks:

Simulation method & assumptions

The five traces are reduced-order teaching demonstrations: second-order short-period, phugoid, and Dutch-roll responses plus first-order roll-subsidence and spiral responses. They expose the dominant motion and are not a full six-degree-of-freedom simulation.
JET11 workbook imports use C_Lα from Main!L7 (deg⁻¹), pitch derivatives from S&C B81–B85, and lateral-directional derivatives from B43, B50, B70, B72–B74, and B76–B78. JSON imports use AeroModel.Official.CLa (deg⁻¹). Displayed angular derivatives use deg⁻¹; the simulator applies the appropriate conversion inside its equations. Missing values receive clearly bounded demonstration defaults.
Roll mode: JET11 does not provide C_lδa directly. The workbook supplies dC_L/dδ_a in Struct!J26 per degree. The simulator multiplies that derivative by the aileron area-weighted spanwise arm ratio y_a/b and applies the appropriate internal angle conversion to obtain C_lδa. The displayed C_lδa uses deg⁻¹. JET11 S&C!B78 contains the vertical-tail contribution to C_lp; because its formula omits the wing contribution, the simulator adds the standard tapered-wing estimate C_lp,wing = −C_Lα(1 + 3λ)/[12(1 + λ)]. The Roll Stick Input slider multiplies the 25 deg maximum aileron deflection (default 50% = 12.5 deg) after the one-second hold, and the simulator integrates I_xxṗ = qSbC_lδaδ_a + qSb²C_lpp/(2V). The aileron centers when bank angle reaches +30 deg. The Roll-damping multiplier scales the combined wing-plus-tail C_lp; 1.00× uses the calculated value.
Standard-day pressure and density convert the selected ideal indicated airspeed into true airspeed and dynamic pressure using compressible pitot relations. These live values follow the simulated speed disturbance. The displayed normal load factor is a reduced-order aerodynamic estimate using the live dynamic-pressure ratio plus incremental lift from angle of attack and elevator deflection; the undisturbed condition is trimmed to 1.00 g.
JET11 Iyy from S&C I97 anchors the inertia estimate when present. JET11 JSON principal inertias and cross terms are used when supplied. Otherwise Ixx and Izz use Daniel P. Raymer’s non-dimensional radii-of-gyration method with representative jet-fighter values Rx = 0.23, Ry = 0.38, and Rz = 0.52, scaled by imported Iyy when available. Raymer’s method estimates the principal moments only; it does not provide the products of inertia Ixy, Ixz, or Iyz, which default to zero unless supplied by JET11 JSON. All six inertia terms are editable, and the simulator uses the resulting full symmetric inertia tensor in its rotational dynamics.

Inertia source pending.

Reference: Daniel P. Raymer, Aircraft Design: A Conceptual Approach, 4th ed., Table 16.1 (non-dimensional radii of gyration). See Raymer’s book page and the official Moment of Inertia Spreadsheet.

This early engineering visualization is not a certified flight-dynamics model. Check derivative signs, units, and fidelity before using results for decisions.