Aircraft ground support equipment — General requirements — Part 2: Stability and strength requirements, calculations and test methods ICS 49.100... NORME EUROPÉENNE EUROPÄISCHE NORM
General
GSE must adhere to the safety standards and protective measures outlined in this clause, including compliance with EN 1915-1, EN 1915-3, and EN 1915-4, as well as the applicable sections of EN 12312 Furthermore, the machine's design must align with the principles established in EN ISO.
12100 for relevant but not significant hazards, which are not dealt with by this document."
NOTE Where a standard automotive chassis is used, the manufacturer of the GSE should pay attention to and appropriate gross mass rating for the intended use.
Requirements for the strength calculation of steel constructions
General remarks
The calculation method must consider the unique complexity of each type of GSE, and its relevance should be clearly outlined in the technical documentation.
Calculations shall be performed in accordance with either
recognized engineering design methods and engineering codes;
actual stress measurements or combinations of these
NOTE Information about load geometry is given in annex A
Design methods and engineering codes must be clearly referenced when using any unusual formulas or calculation methods If such sources are not readily available, only formulas or methods that can be easily verified should be employed.
The general stress analysis shall be carried out to ensure safe levels of stress in relation to the yield stress of the material used
Safe levels of stress related to the loading conditions shall be demonstrated for all supporting structures The principal dimensions, cross sections, materials and fastening means shall be stated
Significant effects of elastic deflection including results of tests (see 5.4.3) shall be considered in the stress analysis
The analysis of the load case combinations intended by the manufacturer shall be carried out to ensure that the severest individual load ratings can be identified
Design strength shall be proven for components under compression which may be susceptible to buckling or bulging using a verifiable method
High dynamic forces must be taken into account when operating safety devices designed to prevent unintentional movements, particularly in the event of fluid leaks in piping systems or failures of ropes, chains, nuts, or gears.
The design of mechanical restraint devices shall take into account all loads and forces occurring during blocking
Where a system has two or more lifting elements in parallel, design shall ensure the loads resulting from the failure of one element shall not have effects jeopardising safety
NOTE For calculation purposes, this situation corresponds to an exceptional loading.
Loads and load combinations
5.2.2.1 The following loads or worse combinations thereof shall be taken into account:
NOTE Load combinations are given in 5.4.5
5.2.2.2 Loads shall be used in the calculation of the strength of the elements concerned at the most unfavourable positions, values and directions
5.2.2.3 The rated load shall be stated by the manufacturer, and shall be not less than 3000 N/m² where the intended use of the GSE is to carry persons, the rated load shall be calculated on the basis of four persons per m², each person at 80 kg For the calculation of floors, local loads of a single person placed on a surface of 200 mm 200 mm shall be taken into account
5.2.2.4 Dynamic forces effective at the same time shall be measured under intended use conditions or be calculated For GSE not designed to be driven during operation, as a general rule (see also EN 12312 series), vertical dynamic forces may be considered to be at least 10 % of the component mass and rated load, subject to assessment by the manufacturer
5.2.2.5 For simplification of the calculation, secondary dynamic forces are introduced into the calculation as static forces by the formula:
F s = 200 N x Σ (1/i) i.e F s = 200 N (1/1+1/2+1/3+ +1/i) where: i is the number of persons on the entire GSE
5.2.2.6 The snow load shall be stated by the manufacturer
NOTE The snow load is depending on the geographical area of use of the GSE and may be agreed between manufacturer and user (see clause 0 – negotiation)
5.2.2.7 The wind force is generally calculated by the formula:
W = c q A where: c is the shape factor;
A is the surface area in square metres; q is the dynamic wind pressure in Pascals
The dynamic wind pressure is calculated by the formula:
2 pv 2 q = where: v is the wind velocity, in metres per second; ρ is the density of air at +15 °C = 1,225 kilograms per cubic metre
The maximum wind velocity shall be stated by the manufacturer A minimum constant wind velocity of 20,58 m/s (40 knots) shall be considered
NOTE The operating conditions to resist higher wind gust velocities may be agreed between manufacturer and user (see clause 0 – negotiation)
For simplification, the wind velocity shall be assumed to be constant over the height of the GSE
The shape factors c are given in annex B.
Materials
Type, grade, chemical composition, weldability and mechanical characteristics (e.g yield strength, modulus of elasticity, shear modulus) of materials used shall be stated in the technical file.
Factors for stress calculations
The stress factors S as specified in Table 1 are applicable for constructional steel up to a yield of 355 N/mm²
Structural elements Butt welds *) Fillet welds *)
*) The stress factors between brackets may be used for welding quality B according to !EN ISO 5817" and welds in accordance with !EN ISO 3834-1 to EN ISO 3834-4."
The factors to be used shall take into account materials used, methods of calculation and/or measurement
The established stress resulting from the multiplication of the calculated stress by the stress factor S shall not exceed the yield stress of the respective material.
Combined stresses
Where situations of combined stresses exist, the equivalent stress shall be verified, paying attention to the plus or minus signs, as follows:
Fatigue
A fatigue calculation shall be carried out The conditions for calculation shall be given by the manufacturer, taking into account the intended load spectrum (see clause 0 – negotiation)
For constructional steel with a yield strength of up to 355 N/mm², fatigue calculations are unnecessary for intended cycles below 20,000 For other materials, applicable limits must be considered.
For constructional steel with a yield strength of up to 355 N/mm², when subjected to cycles of 2 x 10^4 or more, the stress factor S from Table 1 must be multiplied by the fatigue strength factor D from Table 2.
The notch effect also needs to be considered.
Requirements for the calculation of safety related machinery parts
Chain lifting elements
5.3.1.1 The safety factor for load carrying chains shall be at least four Where persons are to be lifted by load carrying chains, the safety factor of the chain shall be at least eight The safety factor is the ratio between the minimum breaking force of the chain and the force which can occur in the chain under maximum static load conditions
5.3.1.2 Chain terminations shall have a breaking force of at least 100 % of the minimum breaking force of the chain.
Cylinders, pipes and hoses used in lifting systems
Calculations of the strength of cylinders, pipes and hoses shall be based on the maximum working pressure (see EN 982)
Pressure in a system is typically restricted by the limits set by a pressure relief valve or the capacity of an accumulator, storage vessel, or pump It is essential to consider potential pressure surges that may arise during the operation of any service within the system.
Cylinders, pipes, and their connections must be demonstrated through calculations to endure at least double the maximum working pressure without experiencing permanent deformation Additionally, for cylinders and piston rods under compression, it is essential to analyze the buckling strength of the piston rod when fully extended.
Fatigue behaviour of piston rods under tension shall be considered
Brittle materials, e.g certain cast iron stock shall not be used for cylinders or connecting links
The bursting pressure of hoses with their fittings shall be not less than three times the related setting pressure of the pressure relief valve.
Wire rope lifting elements
5.3.3.1 Load carrying wire ropes shall be made from galvanized or stainless steel wires and shall have a minimum nominal diameter of 6 mm independent from calculation
In other aspects they shall conform to !ISO 2408"
5.3.3.2 The safety factor for wire ropes used for lifting functions shall be at least five, and where persons are lifted ten The safety factor is the ratio between the minimum breaking force of the wire rope and the maximum static force which can occur in the wire rope with the rated load in the most unfavourable position (see also 5.3.5.2)
5.3.3.3 Wire rope terminations shall have a breaking force of at least 80 % of the minimum breaking force of the wire rope.
Winches
5.3.4.1 Winches shall be designed for 1,6 times the intended nominal load of the wire rope
5.3.4.2 The ratio between the diameters of the drum and the wire rope shall not be less than 20 The diameter of the drum shall be measured from centre to centre of the first layer of wire rope around the drum
5.3.4.3 Drums of winches shall be grooved The grooves shall have a radius of 0,525 times the rope diameter
The flange of drums shall exceed the maximum height of layers plus 1,6 times the diameter of the wire rope used.
Winching plants
5.3.5.1 Winching plants shall be designed such that the angle of divergence from the line normal to the winch/pulley axle does not exceed 4°
5.3.5.2 If a winching plant is designed with pulleys, the number and efficiency of the pulleys have to be considered in the calculation of the rope's load
5.3.5.3 The ratio between the diameter of pulleys and ropes shall not be less than 22 The diameter of the pulley shall be measured from centre to centre of the rope around the pulley.
Stabilizers
Strength calculations of stabilizers shall take into account 5.2.2.2
To assess the loads on the base plate of a stationary Ground Support Equipment (GSE), the relevant load combinations specified in section 5.4.5 must be utilized This evaluation assumes the base plate is positioned at the tipping edge of the GSE, taking into account the most unfavorable load locations and directions Additionally, the manufacturer should provide the maximum ground pressure for the stabilizers.
NOTE The maximum allowable ground pressure is depending on the type of surface where the GSE is intended to be used (see clause 0 – negotiation)
Pneumatic cylinders shall not be used.
Stability calculations
Loads and forces
The following loads and forces shall be considered:
snow load (where intended by the manufacturer);
rated load outboard of tipping edge.
Ground slope
The stability calculation must consider the manufacturer's specified maximum ground slope, with a minimum requirement of 1.5° If a self-levelling stabilizing system can accommodate the maximum ground slope, it will not be factored into the stability assessment.
NOTE The ground slope depends on the airport of use and may be stipulated between manufacturer and user (see clause 0 – negotiation).
Elastic deflection
The effect of elastic deflection shall be included in the stability calculation The deflection shall be verified by test and the calculations modified if significant differences are found.
Flat tyres
Where pneumatic tyres are used, the calculations shall take into account at least one flat tyre in the worst position at the tipping edge.
Load combinations
The GSE shall be stable under the load combinations of Table 3 and any other load combination which can occur under intended use conditions
Table 3 outlines the various load combinations affecting tyres, including scenarios for both unloaded and loaded conditions while extended It details the impact of stabilizers in both unloaded and loaded states, as well as driving conditions The component mass and rated load are specified, along with considerations for snow load, vertical forces, secondary dynamic forces, and overall dynamic forces Additionally, spring reaction forces and wind load are addressed, highlighting the effects of flat tyres under different conditions.
NOTES: 1 ) outboard of tipping edge, if designed for or possible
2) and also any other worst case
4) acting in the worst direction
Stability criteria
A GSE is deemed to be stable if the restoring moment is greater than the tipping moment by a factor of 1,2
Information for use shall conform to EN 1915-1:2001 and the appropriate European Standard of the EN 12312 series
7 Verification of safety requirements and/or measures
General
Verification shall be done on the basis of type testing The test results shall be recorded
Verification of strength shall conform to 7.2
When conducting stability calculations through tipping tests, it is essential that these tests adhere to section 7.3 For ground support equipment (GSE) not designed for lifting, stability must be confirmed if the calculated restoring moment is less than 1.5 times the tipping moment.
When the GSE is intended to be operated on pneumatic tyres, the tyre pressure shall correspond to the figures given by the manufacturer.
Verification of strength
Test loads
7.2.1.1 The static test load, by means of test weights, shall be distributed in such a way that
its centre of gravity corresponds to the calculated centre of gravity of the rated load including local loads;
it corresponds to calculation and intended use
7.2.1.2 The snow load shall be simulated by means of test weights, which shall be distributed and applied in such a way that
its centre of gravity corresponds to the calculated centre of gravity;
7.2.1.3 The calculated wind load shall be simulated and applied at the centre of pressure and in the wind direction as stated in the calculations
7.2.1.4 The calculated secondary dynamic forces shall be simulated and applied at the centres of gravity as stated in the calculations
7.2.1.5 Where the specific standard of the EN 12312 series gives local loads, the static test load shall be 1,25 times these loads, acting in vertical direction at the same time on GSE or parts of it under intended use conditions Where the specific standard of the EN 12312 series gives higher factors, these factors shall be used.
Test procedure
7.2.2.1 All loads shall be applied as stated in 7.2.1.1 to 7.2.1.5 to those components on which they act When the loads cannot be applied to the calculated points of application, a conversion to the next possible point of application shall be done The real forces on the structural components shall be simulated
7.2.2.2 The GSE shall be placed in its operational state in the most unfavourable position and configuration, inclined at the ground slope as stated in the calculations
7.2.2.3 Tests shall be carried out for those operational conditions which give the highest calculated stresses in the individual structure components
7.2.2.4 When the test of GSE cannot satisfy the worst loading conditions of components, these components shall be tested separately according to the relevant EN standards or ISO standards, where EN standards are not available Where such standards are not existing, the verification of requirements including description of the test procedure shall be recorded.
Test results
A test is deemed successful when the stresses experienced during testing remain below the yield limit This can be demonstrated through various methods, such as stress measurement or visual inspection for permanent deformations or cracks on an unpainted Ground Support Equipment (GSE), depending on the complexity of its structure.
Verification of stability
General
The following loads and procedures shall be used for the stability test, unless the specific standard of the EN
Test loads
7.3.2.1 The rated load, by means of test weights, shall be distributed as calculated and placed in such a way that its centre of gravity corresponds to the calculated centre of gravity of the rated load
7.3.2.2 The snow load, by means of test weights, shall be distributed as calculated and placed in such a way that its centre of gravity corresponds to the calculated centre of gravity
7.3.2.3 The calculated wind load shall be applied at the centre of pressure and in the wind direction as stated in the calculations
7.3.2.4 The calculated secondary dynamic forces shall be applied at the centre of gravity as stated in the calculations
7.3.2.5 When wind loads and retardation forces are acting cumulative, thus affecting the stability of GSE, the retardation force shall be considered as a quasi static force applied at the center of gravity as stated in the calculation.
Test procedure
7.3.3.1 During the stationary tipping test the GSE shall be secured against tipping over This safeguard shall not influence the test result
7.3.3.2 Test loads shall be applied as stated under 7.3.2.1 to 7.3.2.5 to the components on which they act
If the test loads cannot be applied at the calculated point of application, they will be converted to the nearest feasible point This ensures that the actual forces on the structural components are accurately simulated.
7.3.3.3 Tipping tests shall be carried out for load combinations with the greatest tipping moment and the smallest restoring moment
7.3.3.4 Retardation forces shall be determined by full braking of the GSE from the maximum speed to zero
7.3.3.5 For stationary tipping tests the GSE shall be placed in its operational state in the most unfavourable position, inclined at the ground slope as stated in the calculations
7.3.3.6 During stationary tipping tests, at least one flat tyre in the worst position at the tipping edge shall be considered on GSE designed to be operated on pneumatic tyres
7.3.3.7 For GSE where the total rated load or parts of it are outside the tipping edge, the test shall be carried out at maximum elevation, considering exclusively the rated load outside the tipping edge
7.3.3.8 For GSE which is designed to be moved without the rated load in the elevated position, the test shall be carried out without rated load, at maximum elevation for driving, considering retardation forces
7.3.3.9 For GSE which is designed to be moved with rated load in the elevated position, the test shall be carried out with rated load, at maximum elevation for driving, considering retardation forces resulting from full braking from the maximum speed
7.3.3.10 During dynamic tests test loads shall be secured against unintentional movements.
Test results
A stability test shall be considered as successful if the GSE remains on at least three supporting points (stabilizers, wheels) which are not situated in one line
Table A.1 — Symbols, units and descriptions
C – centre of gravity , assuming a rigid structure
C ' – centre of gravity with the structure deflected
F N vertical forces, e g forces due to component mass, rated load
F P N component of vertical force, parallel to the ground
F N N component of vertical force, normal to the ground
F S N secondary dynamic force (acting horizontally)
F SP N component of secondary dynamic force, parallel to the ground
F SN N component of secondary dynamic force, normal to the ground
M R Nm tipping moment due to retardation forces
M S Nm tipping moment due to secondary dynamic forces
M W Nm tipping moment due to wind load
M F Nm restoring moment due to vertical force
W B N wind load acting normal to base area
W S N wind load acting normal to side area
W BP N component of wind load on base area, parallel to the ground
W BN N component of wind load on base area, normal to the ground
W SP N component of wind load on side area, parallel to the ground
The wind load component on the side area, denoted as \( W_{SN} \), is influenced by the distance \( a \) from the center of gravity to the tipping edge, assuming a rigid structure Additionally, the deflection of the structure is measured at a distance \( b \) from the center of gravity, also normal to the ground The mass of the structure is represented as \( m \) kg, with a retardation of \( r \) m/s² The angle of ground slope is indicated as \( \alpha \) °, and if applicable, the angle of deflection due to flat pneumatic tires is represented as \( \beta \) °.
Figure A.1 — Geometric relations of stability criteria
For simplification, for small deflections it is assumed that b* = b and β = arc sin b
Figure A.2 — Vertical forces: Forces due to component mass, rated load, mass of persons b' = b - ∆ b = b cos β F P = F sin α a' = a - ∆a = a - b sin β F N = F cos α
Restoring moment M F = F cos α (a - b sin β)-F sin α b cos β
Where no significant deflection (