Source: http://www.trikebuggy.com/far103.htm
Timestamp: 2019-04-21 18:35:41+00:00

Document:
4) has a power-off stall speed which does not exceed 24 knots calibrated airspeed.
A. Any person operating an ultralight vehicle under this part shall, upon request, allow the Administrator, or his designee, to inspect the vehicle to determine the applicability of this part.
B. The pilot or operator of an ultralight vehicle must, upon request of the Administrator, furnish satisfactory evidence that the vehicle is subject only to the provisions of this part.
A. Notwithstanding any other section pertaining to certification of aircraft or their parts or equipment, ultralight vehicles and their component parts and equipment are not required to meet the airworthiness certification standards specified for aircraft or to have certificates of airworthiness.
B. Notwithstanding any other section pertaining to airman certification, operators of ultralight vehicles are not required to meet any aeronautical knowledge, age, or experience requirements to operate those vehicles or to have airman or medical certificates.
C. Notwithstanding any other section pertaining to registration and marking of aircraft, ultralight vehicles are not required to bear markings of any type.
A. No person may operate any ultralight vehicle in a manner that creates a hazard to other persons or property.
B. No person may allow an object to be dropped from an ultralight vehicle if such action creates a hazard to other persons or property.
A. No person may operate an ultralight vehicle except between the hours of sunrise and sunset.
2) all operations are conducted in uncontrolled airspace.
103.13 OPERATION NEAR AIRCRAFT;RIGHT-OF-WAY RULES.
A. Each person operating an ultralight vehicle shall maintain vigilance so as to see and avoid aircraft and shall yield the right-of-way to all aircraft.
2. No person may operate an ultralight vehicle in a manner that creates a collision hazard with respect to any aircraft.
3. Powered ultralights shall yield the right-of-way to unpowered ultralights.
No person may operate an ultralight vehicle over any congested area of a city, town, or settlement, or over any open air assembly of persons.
No person may operate an ultralight vehicle within Class A, Class B, Class C, or Class D airspace or within the lateral boundaries of the surface area of Class E airspace designated for an airport unless that person has prior authorization from the air traffic control facility (ATC) having jurisdiction over that airspace.
No person may operate an ultralight vehicle in areas designated in a Notice to Airmen under §91.143* or §91.141** of this chapter unless authorized by ATC.
* §91.143: Flight limitation in the proximity of space flight operations.
- No person may operate any aircraft of U.S. registry, or pilot any aircraft under the authority of an airman certificate issued by the Federal Aviation Administration within areas designated in a Notice to Airmen (NOTAM) for space flight operations except when authorized by ATC, or operated under the control of the Department of Defense Manager for Space Transportation System Contingency Support Operations.
** §91.141: Flight restrictions in the proximity of the Presidential and other parties.
No person may operate an ultralight vehicle except by visual reference with the surface.
No person may operate an ultralight vehicle when the flight visibility or distance from clouds is less than that in the table below. All operations in Class A, Class B, Class C, and Class D airspace or Class E airspace designated for an airport must receive prior ATC authorization as required in §103.17 of this part.
We’ve all read and sort of absorbed the minimum safe altitude numbers in 14 CFR 91.119 and generally know that we’re supposed to stay 500 feet above the ground and 1,000 feet above congested areas. However, the regulation is a little more complex than those basic numbers.
The problem is “congested area.” Rather than publish a definition so pilots can know how to shape their aeronautical behavior, the FAA purposefully doesn’t—it comes up with its definition on a case-by-case basis. The FAA says it does that so it can balance the pilot’s interests with the need to protect persons and property. In enforcement actions, the FAA has successfully declared that a congested area includes a group of people on an airport ramp, sunbathers on a beach, a small subdivision covering less than a quarter mile, and traffic on an Interstate highway.
If there is a group of people on the ramp watching airplanes, the FAA has considered that group to make the area “congested.” That triggers the clearance distances of 14 CFR 91.119(b). If the pilot is within 2,000 feet horizontally, he or she must be flying 1,000 feet above the highest obstruction unless it’s necessary for taking off or landing. The FAA has long held that a low pass is not necessary for taking off or landing (and if the gear and flaps were up on final, the FAA has taken the position that the pilot wasn’t approaching to land and then executed a go-around). So, if a group of people is hanging around the ramp at a fly-in and you want to make a low pass down the runway, make sure the runway is more than 2,000 feet away—although you may still be subject to the 500-foot minimum altitude regulation. If no one is around and the runway area is considered sparsely populated, the only minimum altitude is to be high enough to land safely if the engine quits; however, you still have to be more than 500 feet horizontally from vehicles and structures—including an airplane parked near the runway.
Today, everyone has a cellphone camera, and those images will be used against you if you are charged with illegal low flying. In addition, the FAA will subpoena your GPS data and use it.
Part 103 also uses the term "congested area"
§103.15 Operations over congested areas.

References: §91
 §91
 §91
 §91
 §103

§103