Excerpts from U.S. Federal Aviation Regulations (FAR)
Part 101 related to unmanned free balloons.


Prepared and footnoted by Mike Manes, W5VSI, for Edge of Space Sciences

28 Nov 01

For the current official regulations try:

Direct link to FAA FAR 101 At the FAA website





Subpart A -- General

§101.1  Applicability.

(a) This part prescribes rules governing the operation in the United States, of the following:

(4) Except as provided for in §101.7, any unmanned free balloon[1] that --

(i) Carries a payload package that weighs more than four pounds and has a weight/size ratio of more than three ounces per square inch on any surface of the package, determined by dividing the total weight in ounces of the payload package by the area in square inches of its smallest surface;

(ii) Carries a payload package that weighs more than six pounds;

(iii) Carries a payload, of two or more packages, that weighs more than 12 pounds; or

(iv) Uses a rope or other device for suspension of the payload that requires an impact force of more than 50 pounds to separate the suspended payload from the balloon.[2]


§101.3   Waivers.

No person may conduct operations that require a deviation from this part except under a certificate of waiver issued by the Administrator.


§101.5   Operations in prohibited or restricted areas.

No person may operate a moored balloon, kite, unmanned rocket, or unmanned free balloon in a prohibited or restricted area unless he has permission from the using or controlling agency, as appropriate.


§101.7   Hazardous operations.

(a) No person may operate any moored balloon, kite, unmanned rocket, or unmanned free balloon in a manner that creates a hazard to other persons, or their property. [3]

(b) No person operating any moored balloon, kite, unmanned rocket, or unmanned free balloon may allow an object to be dropped therefrom, if such action creates a hazard to other persons or their property.

Subpart D -- Unmanned Free Balloons [4]

§101.31   Applicability.

This subpart applies to the operation of unmanned free balloons. However, a person operating an unmanned free balloon within a restricted area must comply only with §101.33 (d) and (e) and with any additional limitations that are imposed by the using or controlling agency, as appropriate.


§101.33   Operating limitations.

No person may operate an unmanned free balloon --

(a) Unless otherwise authorized by ATC, below 2,000 feet above the surface within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport;

(b) At any altitude where there are clouds or obscuring phenomena of more than five-tenths coverage;

(c) At any altitude below 60,000 feet standard pressure altitude where the horizontal visibility is less than five miles;

(d) During the first 1,000 feet of ascent, over a congested area of a city, town, or settlement or an open-air assembly of persons not associated with the operation; or

(e) In such a manner that impact of the balloon, or part thereof including its payload, with the surface creates a hazard to persons or property not associated with the operation.


§101.35   Equipment and marking requirements.

(a) No person may operate an unmanned free balloon unless --

(1) It is equipped with at least two payload cut-down systems or devices that operate independently of each other; [5]

(2) At least two methods, systems, devices, or combinations thereof, that function independently of each other, are employed for terminating the flight of the balloon envelope;[6] and

(3) The balloon envelope is equipped with a radar reflective device(s) or material that will present an echo to surface radar operating in the 200 MHz to 2700 MHz frequency range. [7]

The operator shall activate the appropriate devices required by paragraphs (a) (1) and (2) of this section when weather conditions are less than those prescribed for operation under this subpart, or if a malfunction or any other reason makes the further operation hazardous to other air traffic or to persons and property on the surface. [8]

(b) No person may operate an unmanned free balloon below 60,000 feet standard pressure altitude between sunset and sunrise (as corrected to the altitude of operation) unless the balloon and its attachments and payload, whether or not they become separated during the operation, are equipped with lights that are visible for at least 5 miles and have a flash frequency of at least 40, and not more than 100, cycles per minute. [9]

(c) No person may operate an unmanned free balloon that is equipped with a trailing antenna that requires an impact force of more than 50 pounds to break it at any point, unless the antenna has colored pennants or streamers that are attached at not more than 50 foot intervals and that are visible for at least one mile. [10]

(d) No person may operate between sunrise and sunset an unmanned free balloon that is equipped with a suspension device (other than a highly conspicuously colored open parachute) more than 50 feet along, unless the suspension device is colored in alternate bands of high conspicuity colors or has colored pennants or streamers attached which are visible for at least one mile.


§101.37   Notice requirements.

(a) Prelaunch notice: Except as provided in paragraph (b) of this section, no person may operate an unmanned free balloon unless, within 6 to 24 hours before beginning the operation, he gives the following information to the FAA ATC facility that is nearest to the place of intended operation: [11]

(1) The balloon identification.

(2) The estimated date and time of launching, amended as necessary to remain within plus or minus 30 minutes.

(3) The location of the launching site.

(4) The cruising altitude.

(5) The forecast trajectory and estimated time to cruising altitude or 60,000 feet standard pressure altitude, whichever is lower.

(6) The length and diameter of the balloon, length of the suspension device, weight of the payload, and length of the trailing antenna.

(7) The duration of flight.

(8) The forecast time and location of impact with the surface of the earth.

(b) For solar or cosmic disturbance investigations involving a critical time element, the information in paragraph (a) of this section shall be given within 30 minutes to 24 hours before beginning the operation.

(c) Cancellation notice: If the operation is canceled, the person who intended to conduct the operation shall immediately notify the nearest FAA ATC facility.

(d) Launch notice: Each person operating an unmanned free balloon shall notify the nearest FAA or military ATC facility of the launch time immediately after the balloon is launched. [12]


§101.39   Balloon position reports. [13]

(a) Each person operating an unmanned free balloon shall:

(1) Unless ATC requires otherwise, monitor the course of the balloon and record its position at least every two hours; and

(2) Forward any balloon position reports requested by ATC.

(b) One hour before beginning descent, each person operating an unmanned free balloon shall forward to the nearest FAA ATC facility the following information regarding the balloon:

(1) The current geographical position.

(2) The altitude.

(3) The forecast time of penetration of 60,000 feet standard pressure altitude (if applicable).

(4) The forecast trajectory for the balance of the flight.

(5) The forecast time and location of impact with the surface of the earth.

(c) If a balloon position report is not recorded for any two-hour period of flight, the person operating an unmanned free balloon shall immediately notify the nearest FAA ATC facility. The notice shall include the last recorded position and any revision of the forecast trajectory. The nearest FAA ATC facility shall be notified immediately when tracking of the balloon is re-established.

(d) Each person operating an unmanned free balloon shall notify the nearest FAA ATC facility when the operation is ended.

EOSS Annotations:

[1] Payload strings that don’t exceed any of these four limits are exempted from all other FAR 101 provisions, except 101.7.  EOSS reads “payload” to mean those parts of the flight string that do the work of the mission, independent of how they get to altitude and back down.  Thus we do not include the weight of the balloon, parachute or cutdowns in this tally; the latter are members of the “flight system”.  Tracking beacons, although arguably flight system components, are included in payload weight, however, since they are critical to the payload recovery mission goal.


[2] This applies only to the load line between the balloon and parachute.  “Impact strength” is undefined, but should not be equated to the line’s rated tensile strength; a 50 lb tensile line will break during launch.  The intent of this limit is to ensure that the balloon detaches in the event of collision with an aircraft.  EOSS uses 250 lb woven nylon kite line which did break at a knot during “post-burst chaos” on one flight.

[3] This is the dreaded “Catch 22” clause that the FAA may impose on those who have gained its unfavorable attention.  One cannot successfully argue that a payload string in flight is totally free from all risks to others.  However, taking all reasonable steps to mitigate those risks, such as keeping the flight crews and controllers up to date on your location and altitude and avoiding heavily populated areas, will garner the FAA’s respect and cooperation.


[4] This subPart applies only to those payloads which are not exempt according to Section 101.1 (a) (4).  However, it’s still advisable to adhere to as many of these requirements as reasonably possible (Ibid).

[5] A latex balloon which will burst at altitude is considered to be its own independent cutdown device.   The second device should be a radio-commandable cutter. Plastic balloons must have a commandable primary cutdown and an independent timer-based backup.


[6] A plastic balloon must have some means to dump the fill gas to ensure that it returns to the surface.  A latex “burster” serves as its own destruct device.


[7] The FAA rarely tracks “primary returns” from balloons, relying more on Mode C transponders, and they may require one on “heavy” non-exempt flights.  However, having a GPS-based beacon and a reputation for accurate and timely reports on prior exempt flights may alleviate you from having to carry along this expensive and heavy (7 lb) RFI generator.


[8] A balloon which fails to return to the surface via either commanded or timed termination means or burst is labeled a “derelict” and presents a serious hazard to air navigation.  It will descend into commercial airspace at night, and if its batteries die, its location and altitude are unknown except by visual encounter by flight crews.  Flying a derelict is the surest means to gain the unfavorable attention mentioned in footnote 3 above.


[9] Battery-operated xenon flashtube strobe lights, available at sporting goods stores, have been used for this service, but special care should be taken to conformal coat the high-voltage circuitry which may develop corona or destructive arcover at altitude.  The latest generation of high intensity LEDs, such as those seen more and more in traffic lights, may met this requirement while avoiding high-voltage problems.

[10] These visibility requirements highlight the FAA’s reliance upon visual collision avoidance by flight crews.  Thus it is a good idea to give your payloads a light coat of dayglo orange.  This also helps the recovery crew make a tally-ho call at a distance.  The physical dimensions conforming to the one mile visibility requirement are unclear and may be highly dependent upon the viewer’s visual acuity.


[11] This section describes the minimum content of the “HiBal Prelaunch Notice” filed with ARTCC, the TRACON of the nearest airport and FSS.  EOSS faxes this notice about 1 week in advance to give the ARTCC Airways and Procedures folks a chance to respond.  The EOSS HiBal requests a written response with “special provisions” instructions to be returned a couple of days before the launch.  Those provisions typically include a prelaunch call with forecast trajectory thru several flight levels.  This FAA response has served to alleviate concerns by visitors from time to time.


[12] EOSS also makes a T-0:30 phone call to ARTCC and TRACON per the “special provisions”.  The operations folks invariably have a copy of our HiBal Notice, so there are no surprises.  EOSS uses Rick von Glahn’s Balloon Track with the latest NWS RAOB winds for our forecast position and altitude estimates.  The FAA controllers prefer position reports in  radial and NM range from the nearest high altitude VOR.  This prelaunch call also includes the launch site cell phone number.  If launch is delayed by over 10  minutes, we call in a new estimated launch time.


[13] The TRACON operations folks are typically interested in position reports below FL240, and ARTCC usually requests reports out of FL260, 450 and 600 in ascent and descent.  Position accuracy to within a 5-mile radius is sufficient.  The GPS-based APRS beacon makes this simple, but good RDF fixes and barometric altitude telemetry will serve just fine. 


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