Are you FAR 103 Legal?

(Note 1: input fields at the ends of numbered lines, output fields flush left.
You can change input fields and see the results. Once you've changed a field, click outside the box to force a re-calculation.)
(Note 2: For the FAA's definitions of the factors contact: Jon Steiger's Ultralight Home Page
Click on regulations, then USA. )

(Note 3: If you are having trouble making this calculator work under MS Internet Explorer, let me know. And know you are not alone...:(

Determining Max Level Airspeed

1. Pilot Drag Factor =
Choose a number from the list:
*Not Enclosed -prone .............................. 1.2 -supine .............................. 4.5 -seated upright ....................... 5.5 *Partially Enclosed -lower half of body enclosed .......... 3.5 -only head exposed .................... 2.5 -streamlined, head behind windshield... 2.0 *Totally Enclosed -streamlined fuselage ................. 1.5 -boxy fuselage ........................ 2.0

2. Wing Drag Factor =
Enter the wing surface area (sq. ft.).

3. Stabilizing Surface Drag Factor =
Enter the vertical/horizontal tail/canard surface area (sq. ft.).

4. Exposed Wire Drag =
Enter total exposed wires over 4 ft. long.

5. Exposed Strut Drag =
Enter total exposed struts over 4 ft. long.

6. Landing Gear Drag =
Number of Faired Wheels:
Number of Unfaired Wheels:
(If I were you I'd count that modified doughnut on the tail of your tri-geared UL.. ;-)

7. Engine Drag factor =
Choose from:
*completely exposed = 2.5
*partially exposed = 1.5
*some components exposed = 0.5


Your computed total drag factor is:


INSTRUCTIONS: Enter the bottom of the chart at the engine manufacturer's maximum horsepower rating of the installed engine. (Example: 45 horsepower). Proceed directly up the horsepower line until encountering the total drag factor curve computed for the ultralight (Example: 15). Note horizontal line which also intersects at that point, proceed to the left along that line to the edge of the graph, read maximum airspeed.

DETERMINING POWER-OFF STALL SPEED

1. Total gross weight =
e.g. Empty weight plus 170 lbs. for the pilot and 30 lbs. for fuel.

2. Your wing loading is =
(lbs. per sq. ft.)
3. Airfoil Lift Factor
Choose from the following:
1.4 Airfoils with less than 7 percent camber and no flaps.
1.6 Airfoils with greater than 7 percent camber.
1.8 Airfoils with flaps less than 50 persent span.
2.0 Airfoils with flaps greater than 50 percent span.


Enter the bottom of the chart at the computed wing loading of the ultralight. Proceed straight up the wing-loading line to the point where it intersects the applicable lift factor curve. Note horizontal line which also intersects at that point, proceed to the left side of the chart via that line. Read power-off stall speed.


Cudos, Complaints, Confusions? email: Del Ogren del@n-lemma.com