ASTM F2355-14(2022)
(Specification)Standard Specification for Design and Performance Requirements for Lighter-Than-Air Light Sport Aircraft
Standard Specification for Design and Performance Requirements for Lighter-Than-Air Light Sport Aircraft
ABSTRACT
This specification covers design and performance requirements that apply for the manufacture of lighter-than-air light sport aircraft. Performance requirements for balloons, airships and thermal airships are: proof of compliance; general performance; flight performance; climb; controllability and maneuverability; descent; landing; and stability and control. Structure requirements for airships, thermal airships, balloons and vectored thrust balloons are presented in details. The power plant installation shall be easily accessible for inspection and maintenance. The equipments for airships and free balloons are presented in details. The operating limitations and other information necessary for safe operation shall be established and documented in a flight manual, which will be made available to the pilot upon aircraft delivery.
SCOPE
1.1 This specification covers design and performance requirements that apply for the manufacture of lighter-than-air light sport aircraft.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory requirements prior to use.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2355 −14 (Reapproved 2022)
Standard Specification for
Design and Performance Requirements for Lighter-Than-Air
Light Sport Aircraft
This standard is issued under the fixed designation F2355; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This specification covers design and performance re- 3.1 Definitions:
quirements that apply for the manufacture of lighter-than-air 3.1.1 airship—engine-driven lighter-than-air aircraft that
light sport aircraft.
can be steered.
3.1.1.1 Discussion—This definition can include “and that
1.2 This standard does not purport to address all of the
sustains flight through the use of either gas buoyancy or an
safety concerns, if any, associated with its use. It is the
airborne heater, or both.”
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.1.2 balloon—lighter-than-air aircraft that is not engine-
mine the applicability of regulatory requirements prior to use. driven, and that sustains flight through the use of either gas
1.3 This international standard was developed in accor-
buoyancy or an airborne heater, or both.
dance with internationally recognized principles on standard-
3.1.3 design useful load—load (other than structure, engine,
ization established in the Decision on Principles for the
enclosure,andsystems)thatalighter-than-airaircraftcancarry
Development of International Standards, Guides and Recom-
while achieving the design defining performance requirements.
mendations issued by the World Trade Organization Technical
3.1.4 gross weight—total aircraft system weight(s) at take-
Barriers to Trade (TBT) Committee.
off.
3.1.5 lighter-than-air aircraft—aircraft that can rise and
2. Referenced Documents
remain suspended by using contained gas weighing less than
2.1 ASTM Standards:
the air that is displaced by the gas.
F2354 Specification for Aircraft Interaction of Systems and
3.1.5.1 Discussion—Airships may include dynamic lift that
Structures (Withdrawn 2022)
derive as much as 30 % lift from other than buoyancy.
F2356 Specification for ProductionAcceptance Testing Sys-
3.1.6 maximum takeoff weight—gross weight limit as de-
tem for Lighter-Than-Air Light Sport Aircraft
fined by the manufacturer, proven through compliance with
F2427 Specification for Required Product Information to be
this specification and placarded on the aircraft as the not-to-
Provided with Lighter-Than-Air Light Sport Aircraft
exceed gross weight.
F2483 Practice for Maintenance and the Development of
Maintenance Manuals for Light Sport Aircraft 3.1.7 thermal airship—airship using heated air for a portion
F2563 Practice for Kit Assembly Instructions of Aircraft of its lift, incorporating design features to prevent nose
Intended Primarily for Recreation collapse due to dynamic pressure and exempt from specific
F2972 Specification for Light Sport Aircraft Manufacturer’s pressurized envelope requirements.
Quality Assurance System
3.1.8 vectored thrust balloon—thermal balloon with thrust
capabilitythatdoesnothavedesignfeaturestopreventforward
envelope collapse due to dynamic pressure and is therefore
This specification is under the jurisdiction of ASTM Committee F37 on Light limited in its lateral speed capability.
Sport Aircraft and is the direct responsibility of Subcommittee F37.60 on Lighter
3.1.9 weight limitations—operational weight restrictions
than Air.
(maximum/minimum) as defined by the manufacturer and
Current edition approved Oct. 1, 2022. Published October 2022. Originally
approved in 2005. Last previous edition approved in 2014 as F2355 – 14. DOI:
proven through compliance with this specification to demon-
10.1520/F2355-14R22.
strate controllability.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on 4. Flight Requirements
the ASTM website.
4.1 Performance Requirements for Airships and Thermal
The last approved version of this historical standard is referenced on
www.astm.org. Airships, except as noted:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2355 − 14 (2022)
4.1.1 Proof of Compliance—Each of the following require- minimum of in-flight turbulence. The three conditions are
ments shall be met at the maximum takeoff weight and most ascent, descent, and level flight.
critical center of gravity (CG) position. To the extent that CG
4.1.8.3 Longitudinal Control—With all engines operating at
adjustment devices may be adjusted for flight, these compo-
maximum power, the airship must be capable of:
nents will be evaluated in the least favorable recommended
(1) A nose-down pitch from a stabilized climb with a 30°
position as it affects either performance or structural strength.
nose-up deck angle,
4.1.2 General Performance—All performance requirements
(2) A nose-up pitch from a stabilized descent with a 30°
apply in and shall be corrected to International Civil Aviation nose-down deck angle, and
Organization (ICAO) defined standard atmosphere in still air
(3) Longitudinal upset response shall be evaluated by
conditionsatsealevel.Speedsshallbegiveninindicated(IAS) analysisortest,orboth,toshowthatitdoesnotresultinunsafe
and calibrated (CAS) airspeeds in knots.
conditions.
4.1.3 Flight Performance—For all flight operations it shall
4.1.8.4 Lateral and Directional Stability:
be shown that control sufficient to safely maneuver or land the
(1) Lateral stability will be demonstrated by maintaining
airship, or both, can be maintained. thesurfacecontrolsinafixedposition,whichwillinitiallygive
an unaccelerated level flight condition. The aircraft must not
4.1.4 Climb—The following shall be measured:
enter into a dangerous altitude during the 2 min that the flight
4.1.4.1 Distance to clear a 15 m (50 ft) obstacle not to
control surfaces are fixed. A test must be conducted at
exceed 213 m (700 ft) from point of lift-off. Compliance with
maximum operating weight, with minimum in-flight turbu-
therequirementsofthissectionmustbeshownateachextreme
lence.
of altitude and ambient temperature for which approval is
(2) Directional stability will be demonstrated by a separate
sought.
andfulldeflectionofeachdirectionalflightcontrolsurfacesfor
4.1.4.2 Climb rates of 1.5 m/s (300 fpm) and 0.5 m/s (100
three full turns of 360° without the aircraft entering any
fpm) with one engine inoperable for multi-engine configura-
dangerous flight altitude during the maneuver. A test must be
tions.
conducted at minimum flight weight, with minimum in-flight
4.1.5 Controllability and Maneuverability—The aircraft
turbulence. The demonstrated turn rate shall not be less than
shall be safely controllable and maneuverable during takeoff,
6°/s (60 s for a 360° turn) in either direction.
climb, level flight (cruise), approach, and landing.
4.1.5.1 Demonstrate a smooth transition between all flight 4.2 Performance Requirements for Balloons:
conditions shall be possible without excessive pilot skills nor
4.2.1 Proof of Compliance—Each of the following require-
exceeding pilot forces of 59.1 kg (130 lb) for the foot-operated
ments shall be met at the maximum takeoff weight.
control, 9.1 kg (20 lb) prolonged application, or 29.5 kg (65 lb)
4.2.2 General Performance—All performance requirements
hand controls, 4.5 kg (10 lb) prolonged operation.
apply and shall be corrected to International Civil Aviation
4.1.6 Descent—The following shall be measured.
Association Organization (ICAO) defined standard atmosphere
4.1.6.1 It must be shown that in the event of the most
in still air conditions at sea level.
critical uncontrolled descent from either: (1) an engine or
4.2.3 Flight Performance—For level flight, climbs,
propeller failure, (2) burner failure for thermal airship, (3)
descents, and landing, it shall be shown that control sufficient
valve leak for either hot air or captive gas airship, or (4) the
to safely land the balloon can be maintained.
maximum permitted envelope failure as specified in 5.1.2.
4.2.3.1 Climb—Eachballoonmustbecapableofclimbingat
least 300 ft in the first minute after takeoff with a steady rate of
NOTE 1—Procedures must be established for landing at the maximum
vertical velocity attained and procedures must be established for arresting climb. Compliance with the requirements of this section must
the maximum descent rate within the manufacturer’s specified altitude.
be shown at each altitude and ambient temperature for which
approval is sought.
4.1.7 Landing—It must be shown that a pilot of normal skill
4.2.3.2 Controllability—The balloon shall be controllable
canachievelandingsinkratesofnomorethan0.77m/s(2ft/s).
during takeoff, climb, level flight, approach, and landing.
4.1.8 Stability and Control:
4.2.3.3 Descent—The following shall be measured. It must
4.1.8.1 Vertical Stability and Control—Stability and control
be shown that in the event of the most critical uncontrolled
of the airship shall be determined at maximum gross weight,
descent from either: (1) burner failure for hot air balloon, (2)
with minimum in-flight turbulence/wind for:
valve leak for either hot air or captive gas, and (3) the
(1) Maximum duration of envelope valve operation (if
maximum permitted envelope failure as specified in 5.2.2.
equipped), during which the airship must not enter into a
Procedures must be established for landing at the maximum
dangerous descent.
vertical velocity attained and procedures must be established
(2) Minimum burner fuel pressures (if equipped), which
for arresting the maximum descent rate within the manufac-
will arrest the maximum descent rate as determined in 4.1.6
turer’s specified altitude.
and climb as determined in 4.1.4.
4.2.3.4 Landing—It must be shown that the pilot can
4.1.8.2 Longitudinal Stability—Longitudinal stability of the
achieve a landing sink rate of not more than 1 m/s.
aircraft will be demonstrated by performing 2 min of flight
without control input for three conditions. In each case, the 4.2.4 Stability and Control—Stability and control of the
aircraft must not enter into dangerous or unusual altitudes. A balloon shall be determined at maximum gross weight, with
test must be conducted at maximum gross weight, with a minimum in flight turbulence/wind for:
F2355 − 14 (2022)
4.2.4.1 Maximum duration of envelope valve operation, 5.1.7.1 Design Stall Speed, V(SI)—shall be calculated based
during which the balloon must not enter into a dangerous on area, lift coefficient estimates, and maximum negative
descent. boyance.
4.2.4.2 Minimum burner fuel pressures that will arrest the
5.1.7.2 Design Maximum Level Flight Airspeed, V(H)—
maximum descent rate as determined in 4.2.3.3 and climb as
V(H) is the maximum speed obtainable in level flight with all
determined in section 4.2.3.1.
engines operating at maximum continuous power and the
airship loaded to achieve minimum drag.
5. Structure Requirements
5.1.7.3 Design Airspeed for Maximum Gust Intensity,
V(B)—V(B) shall not be less than 35 knots or 0.65 V(H),
5.1 Structure for Airships and Thermal Airships (except as
whichever is least.
noted):
5.1.7.4 Maneuver loads considering the maximum forces
5.1.1 Loads—Unless otherwise specified, all requirements
that can be generated by the envelope and surfaces at V(H) and
are specified in terms of limit load.
maximum control deflections, unless placarded to limit deflec-
5.1.1.1 Ultimate loads are limit loads multiplied by the
tion at specific conditions.
factor of safety defined below. Loads shall be redistributed if
the deformations affect them significantly. 5.1.7.5 Gust loads of a discrete gust of 7.6 m/s (25 fps) at
V(H) and 10.6 m/s (35 fps) at V(B).
5.1.2 Factors of Safety—The factor of safety is 1.5, except
as shown in the following:
5.1.8 Control Surface Loads—Control surface loads on the
5.1.2.1 3.0 on castings, airship shall be evaluated at loads defined in flight tests of the
5.1.2.2 1.8 on fittings, envelope by the envelope manufacturer.
5.1.2.3 6.67 on control surface hinges,
5.1.9 Ground Mooring Conditions (when equipped)—An
5.1.2.4 3.3 on push-pull control systems,
airship that is normally moored to a mooring mast when not in
5.1.2.5 2.0 on cable control systems, and flight, such as overnight. The mooring mast system shall be
5.1.2.6 5.0 on envelope structures (fibrous or non-metallic
adequate to allow the airship to swing around the mast 360° as
parts) and rigging. wind direction changes. The strength of the mast shall be
5.1.2.7 In applying factors of safety, the effect of tempera- sufficient to safely moor the airship in high or gust wind
tureandotheroperatingcharacteristics,orboth,thatmayaffect conditions as specified by the manufacturer. Accommodation
strength of the balloon must be accounted for. shall be made to allow the car to accept these sideward
5.1.2.8 For design purposes, an occupant weight of at least movements without damage.
170 lb must be assumed.
5.1.10 Control System and Supporting Structure—The con-
5.1.3 Strength and Deformation:
trol system structure shall be designed to withstand maximum
5.1.3.1 The structure must be able to support limit loads
forces, and in the case of dual controls, the relevant system
without permanent deformation of the structure.
shall be designed for the pilots operating in opposition, if
5.1.3.2 The structure must be shown by analysis, test, or
greater than the control system forces.
analysissupportedbytesttobeabletowithstandultimateloads
5.1.11 GroundLoadConditions—Designfeaturesshalllimit
without failure.
the landing sink rate to less than or equal to 1 m/s (3.3 ft/s).
5.1.3.3 The structure shall be able to withstand ultimate
Testing by drop test will use a drop height to achievea1m/s
loads for 3 s without failure when proof is by static test. When
(3.3 ft/s) drop rate. This will be a dead drop test of the car
dynamic tests are used to demonstrate strength, the 3-s require-
without envelope lift at maximum takeoff weight.
ment does not apply. Local failures or structural instabilities
5.1.12 Emergency Landing Conditions—Design structure to
between limit load and ultimate load are acceptable if the
protect each occupant from serious injury when the aircraft
structure ca
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