Aircraft Sizing — The Drafting Table

1 Category & Configuration

This sets every default formula range used downstream. Choose the closest fit — you can change it later.

Aircraft Category i

Part 103 Ultralight

Single-seat, ≤254 lb empty, slow & light. Strictest limits.

Experimental Amateur-Built

Most homebuilt 2-seaters. Flexible, builder-defined limits.

Light Sport (LSA)

Up to ~1320 lb MTOW, 2 seats, defined performance caps.

Seating Configuration i

Single Seat

Lightest, shortest fuselage.

Tandem 2-Seat

Narrow fuselage, longer tail arm.

Side-by-Side 2-Seat

Wider fuselage, shorter tail arm.

Mission Emphasis i

STOL / Bush

Short takeoff/landing, low stall speed, rough strips.

Balanced

General-purpose, no extreme priorities.

Cruise-Efficient

Speed and range over short-field capability.

Propulsion Layout

Units

Wing Vertical Position i

High Wing

Stable, simple construction. Popular for STOL/bush. Pendulum stability effect.

Mid Wing

Aerodynamic compromise. Complex fuselage junction. Less common in homebuilts.

Low Wing

Better visibility, sleeker profile. More dihedral needed. Common in LSA/cruise designs.

Tail Configuration i

Conventional

Horizontal stab at fuselage base. Simplest, most proven. Recommended default.

T-Tail

Stab on fin tip. Avoids downwash. Adds fin weight, deep-stall risk.

Cruciform

Stab at mid-fin. Compromise. Used on some bush designs for prop clearance.

2 Weight Estimation

Total weight (MTOW) is the master input — almost everything else scales from it.

Pilot Weight lb i

Fuel Capacity gal i

Baggage Allowance lb

Empty Weight Estimate lb i

Maximum Takeoff Weight (MTOW) lb i

3 Wing Loading & Stall Speed

This is the core trade-off: lower stall speed and lower wing loading mean a bigger wing for the same weight.

Target Stall Speed (Vs) mph i

Max Lift Coefficient (CLmax) i

Wing Loading (W/S) lb/ft² i

4 Wing Area, Span & Chord

From wing loading and aspect ratio, we derive the wing's physical dimensions.

Aspect Ratio (AR) i

Wing Area (S) ft² i

Wingspan (b) ft i

Mean Chord ft i

5 Airfoil Selection & Angles

We estimate your Reynolds number from cruise speed and chord, then suggest airfoils matched to your flight regime. All values are editable.

Target Cruise Speed mph i

Reynolds Number (cruise) i

Suggested Airfoils i

Selecting an airfoil updates your CLmax. If the new value differs from Step 3, wing area will recalculate automatically.

Wing Angles

Wing Incidence Angle (°) i

Proposed: 3° — typical for light aircraft (fuselage level at cruise). Adjust based on your airfoil's zero-lift angle.

Cruise Angle of Attack (α) (°) i

Estimated once cruise speed is entered.

Flap Configuration

Flap Type i

None

Simplest. Fixed-geometry wing.

Plain Flap

Simple hinge. Easy to build, moderate lift gain.

Slotted Flap

Best lift/drag for STOL. More complex.

Split Flap

High drag (good for steep approaches), moderate lift.

Flap Deflection (°) i

ΔCLmax from Flaps i

6 Fuselage & Tail Arm

Fuselage length determines your tail arm — the leverage your tail surfaces have. Longer arm = smaller tail area needed for the same stability.

Engine / Powerplant i

Fuselage Length ft i

Tail Arm (L_t) ft i

Tail Incidence

Horizontal Tail Incidence (°) i

Proposed: −1.5° (gives natural pitch-up correction — aircraft tends to lower nose if AoA increases). Adjust during flight testing.

Vertical Fin Offset (°) i

Default: 0°. Some designers offset 0.5–1° right (tractor) to counteract engine torque. Verify empirically.

7 Tail Sizing

Tail volume coefficients translate your tail arm and wing geometry into the required tail surface areas. Typical ranges shown — edit if you have a specific design in mind.

Tail Volume Coefficients

Horizontal Tail Volume (V_h) i

Vertical Tail Volume (V_v) i

Horizontal Tail (Stabiliser)

H-Tail Area ft² i

H-Tail Span ft i

H-Tail Chord ft

Vertical Tail (Fin & Rudder)

V-Tail Area ft² i

Fin Height ft i

Fin Chord ft

8 Power & Propeller

Power loading ties your engine choice to your aircraft's weight. Propeller diameter is a rough estimate — consult your engine manufacturer's charts for final selection.

Power Loading lb/hp i

Required Power hp i

Select Engine (optional) i

Actual Power Loading (if engine selected) lb/hp

Propeller Estimate

Suggested Prop Diameter Range ft

Prop Type Suggestion

⚠ Propeller sizing shown here is a rough starting estimate only. Final prop selection (diameter, pitch, blade count) depends on your engine's specific torque curve, RPM, and reduction ratio. Consult your engine manufacturer's propeller charts before purchasing.

9 Design Summary

Your complete sizing results. Compare with reference aircraft, review any flags, then export or email to yourself.

How Your Design Compares

Complete Results

Take Your Design Further

These numbers are your starting point — a structured set of constraints you can hand directly to a modeling tool. Export to CSV or JSON to feed your geometry into OpenVSP for 3D shaping, XFLR5 for aerodynamic analysis, or a custom spreadsheet. Save a PDF to keep a timestamped record of this sizing pass — useful when you iterate and want to compare where you started. Nothing here replaces an engineering review, but it gives you a defensible, traceable baseline to walk into that review with.

The Drafting Table // Aircraft Sizing