Load Distribution Using Spreaders
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Yes, there is certainly terminology in place, which is why I ref the entire document.
There is also the Load Factor on page 226 that is for the 'apparent weight' of a heavy load, ie the centroid of the mass which would include the height of the object.
Reference back to the OP diagram and the question. That is a uniform distributed load per the document.
There is also the Load Factor on page 226 that is for the 'apparent weight' of a heavy load, ie the centroid of the mass which would include the height of the object.
Reference back to the OP diagram and the question. That is a uniform distributed load per the document.
That is all true.
The OP posted the same question in another website (BRISTOL GROUND SCHOOL). This suggests that he/she is doing the ATPL course or has recently completed it (probably with BGS). In the context of EASA ATPL ground school the term Static Load means:
Static Load Load / Contact Area
Using this definition and the data in the question posed the answer would be 667.
It is also a situation in which the Contact load Limit must be applied.
Although you gave the title of the Airbus document, you actually quoted only the page that supported your argument. You did not quote the page that supported the view of JT and some others in this thread. That may help you to win arguments but it is not a good way to enhance mutual understanding.
The OP posted the same question in another website (BRISTOL GROUND SCHOOL). This suggests that he/she is doing the ATPL course or has recently completed it (probably with BGS). In the context of EASA ATPL ground school the term Static Load means:
Static Load Load / Contact Area
Using this definition and the data in the question posed the answer would be 667.
Reference back to the OP diagram and the question. That is a uniform distributed load per the document.
Although you gave the title of the Airbus document, you actually quoted only the page that supported your argument. You did not quote the page that supported the view of JT and some others in this thread. That may help you to win arguments but it is not a good way to enhance mutual understanding.
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More importantly, a generic document is not the appropriate reference to determine the OEM's views, rather the particular aircraft's Loading Manual (by whatever name titled).
While it is rational to follow the OEM's prescribed Type practices, in the absence of such, pragmatism requires that the reasonably most conservative interpretation should apply.
While it is rational to follow the OEM's prescribed Type practices, in the absence of such, pragmatism requires that the reasonably most conservative interpretation should apply.
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not at all...Note in the page ref, example #2 where running load is exceeded.
I also explained several posts back as to when you start looking at concentrated loads, and when you look at the height of the load.
The contact load portion you ref is not applicable to the OP. Contact loading assumes there are no spreaders, it is the direct contact point of the object. The OP specifically ref spreaders.
and speaking quoting only one page...
You quote page 221, note the next page, 222. Contact load with spreaders and without. Note the surface area used with the spreaders.
I also explained several posts back as to when you start looking at concentrated loads, and when you look at the height of the load.
The contact load portion you ref is not applicable to the OP. Contact loading assumes there are no spreaders, it is the direct contact point of the object. The OP specifically ref spreaders.
and speaking quoting only one page...
You quote page 221, note the next page, 222. Contact load with spreaders and without. Note the surface area used with the spreaders.
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I also explained .. when you look at the height of the load.
Perhaps you might expand on this ? Considerations of restraint we understand well, but for general loading considerations involving floor limitations ?
Perhaps you might expand on this ? Considerations of restraint we understand well, but for general loading considerations involving floor limitations ?
underfire
You state:
And:
But in the same post you have included a calculation for contact load, which includes spreaders:
If we apply exactly the same process to the OP we get
Contact Load = 2000 / 3 = 667 kg/m squared.
You state:
The contact load portion you ref is not applicable to the OP. Contact loading assumes there are no spreaders, it is the direct contact point of the object. The OP specifically ref spreaders.
You quote page 221, note the next page, 222. Contact load with spreaders and without. Note the surface area used with the spreaders.
Contact Load = (500 + 20 ) / 0.48 = 1084 kg/m squared.
Contact Load = 2000 / 3 = 667 kg/m squared.
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KW, That does not compute:
In the example shown in post, the area load with floor spreaders is 1.2x0.5,
In the OP example, the floor spreader load is 1.5x3=4.5, 2000/4.5=444.44
Note that area calc for a contact load with spreaders is the same as UDL.
JT,
With heavier loads, especially irregular shapes, you must look at the CG of the load. The resultant force, when the aircraft rotates or banks is very important. Restraints, depending on the angle of restraint, size, shape, or where the object is located, may not be able adequately distribute the load to the floor uniformly. The spreaders must be designed not to flex and create a punching shear or excessive bending moment in the floor. Max angle on a strap is 30 degrees, so a high CG of the load is going make things difficult. Straps are not infinitely rigid, so any flex redistributes the load to others.
Bank the ac 25 degrees, and that offset cg load will distribute unevenly to the spreaders, and any flex in the spreader will create a concentrated load.
In general, this is addressed in the Load Factors and Apparent Weight calcs, and these are certainly oversimplified with a perfect center of mass. It is the unusual loads, especially the ones that are near floor limits, that should be addressed.
In the example shown in post, the area load with floor spreaders is 1.2x0.5,
In the OP example, the floor spreader load is 1.5x3=4.5, 2000/4.5=444.44
Note that area calc for a contact load with spreaders is the same as UDL.
JT,
With heavier loads, especially irregular shapes, you must look at the CG of the load. The resultant force, when the aircraft rotates or banks is very important. Restraints, depending on the angle of restraint, size, shape, or where the object is located, may not be able adequately distribute the load to the floor uniformly. The spreaders must be designed not to flex and create a punching shear or excessive bending moment in the floor. Max angle on a strap is 30 degrees, so a high CG of the load is going make things difficult. Straps are not infinitely rigid, so any flex redistributes the load to others.
Bank the ac 25 degrees, and that offset cg load will distribute unevenly to the spreaders, and any flex in the spreader will create a concentrated load.
In general, this is addressed in the Load Factors and Apparent Weight calcs, and these are certainly oversimplified with a perfect center of mass. It is the unusual loads, especially the ones that are near floor limits, that should be addressed.
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underfire,
Perhaps you could PM me with a synopsis of your background so that we don't waste too much time going around in circles ? I do find some of your posts rather perplexing .. as does my good colleague, Mr Williams, I suspect ...
you must look at the CG of the load.
fair comment. However, other than for very asymmetric loads, I don't think folks generally worry too much in practice .. although the design folk certainly run this consideration into restraint system calculations.
Restraints .. may not be able adequately distribute the load to the floor uniformly.
an innovative thought ... the restraints are more likely to do just as well in turning flight as for straight and level. As to whether that be good or bad is the province of the design folks.
The spreaders must be designed not to flex and create a punching shear or excessive bending moment in the floor.
as suggested previously in several spots.
Max angle on a strap is 30 degrees
why ever might that be ? The restraint designer will use whatever angles suit the circumstances, considering geometric limitations, practical workability, and the boss's preferences ....
so a high CG of the load is going make things difficult.
why ? All taken care of in the back room head scratching.
Bank the ac 25 degrees, and that offset cg load will distribute unevenly to the spreaders, and any flex in the spreader will create a concentrated load.
again, unless we are looking at wildly unbalanced flight - and we ought not need to worry too much about that - how does the bank angle cause this to happen in a manner different to straight and level flight ?
For any real life half sensible spreader, the second statement is invalid.
In general, this is addressed in the Load Factors and Apparent Weight calcs
matters for the design PE folks to concern themselves with .. the pilots etc., only have to follow the load system requirements which should make the exercise very straightforward. Unless one is looking, say, at a basic pilot weight and balance theory course in which such things might be introduced for background understanding ... ?
It is the unusual loads, especially the ones that are near floor limits, that should be addressed.
likewise. The pilots etc. should just follow the system specified and the back room folks should have made sure that it all works according to Hoyle.
I look forward to your continuing responses ...
Perhaps you could PM me with a synopsis of your background so that we don't waste too much time going around in circles ? I do find some of your posts rather perplexing .. as does my good colleague, Mr Williams, I suspect ...
you must look at the CG of the load.
fair comment. However, other than for very asymmetric loads, I don't think folks generally worry too much in practice .. although the design folk certainly run this consideration into restraint system calculations.
Restraints .. may not be able adequately distribute the load to the floor uniformly.
an innovative thought ... the restraints are more likely to do just as well in turning flight as for straight and level. As to whether that be good or bad is the province of the design folks.
The spreaders must be designed not to flex and create a punching shear or excessive bending moment in the floor.
as suggested previously in several spots.
Max angle on a strap is 30 degrees
why ever might that be ? The restraint designer will use whatever angles suit the circumstances, considering geometric limitations, practical workability, and the boss's preferences ....
so a high CG of the load is going make things difficult.
why ? All taken care of in the back room head scratching.
Bank the ac 25 degrees, and that offset cg load will distribute unevenly to the spreaders, and any flex in the spreader will create a concentrated load.
again, unless we are looking at wildly unbalanced flight - and we ought not need to worry too much about that - how does the bank angle cause this to happen in a manner different to straight and level flight ?
For any real life half sensible spreader, the second statement is invalid.
In general, this is addressed in the Load Factors and Apparent Weight calcs
matters for the design PE folks to concern themselves with .. the pilots etc., only have to follow the load system requirements which should make the exercise very straightforward. Unless one is looking, say, at a basic pilot weight and balance theory course in which such things might be introduced for background understanding ... ?
It is the unusual loads, especially the ones that are near floor limits, that should be addressed.
likewise. The pilots etc. should just follow the system specified and the back room folks should have made sure that it all works according to Hoyle.
I look forward to your continuing responses ...
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I agree with JT's analysis of the physics and the ultimate authority of the OEM.
Reference the terminology and exam questions, there is no apparent dispute about what 'running load' means so I will disregard that. It seems we have two Airbus definitions which are 'Contact load' and 'Area Load'. There is only one definition in the JAA learning objectives which is related to this and that is:
Area Load or Floor Load
The load (or Mass) distributed over a defined area. Units of measurement used:
SI: N/m2, kg/m2 ; Non-SI: psi, lb/ft2
That definition could match either the Airbus 'Contact load' or the 'Area load', depending on the defined area.
KW, 'static load' is not an LO term, and I do not see, given the imprecise definition above, that you can deduce that 'area load'/'floor load' as defined in the LOs = the Airbus term 'contact load'. Do you have any more info on this?
Reference the terminology and exam questions, there is no apparent dispute about what 'running load' means so I will disregard that. It seems we have two Airbus definitions which are 'Contact load' and 'Area Load'. There is only one definition in the JAA learning objectives which is related to this and that is:
Area Load or Floor Load
The load (or Mass) distributed over a defined area. Units of measurement used:
SI: N/m2, kg/m2 ; Non-SI: psi, lb/ft2
That definition could match either the Airbus 'Contact load' or the 'Area load', depending on the defined area.
KW, 'static load' is not an LO term, and I do not see, given the imprecise definition above, that you can deduce that 'area load'/'floor load' as defined in the LOs = the Airbus term 'contact load'. Do you have any more info on this?
Alex, I must confess that I had not spotted the fact that the old “Static Load” had been replaced by “Area Load” in the learning objectives.
You are quite correct in saying that the definition now used in the LO’s, could match either the Airbus 'Contact load' or the 'Area load', depending on the defined area.
The thing that caught my eye in all of this was the fact that both of the numbers given in the original question (667 and 444) could be correct. 667 is correct for the AIRBUS Contact Load and 444 is correct for the AIRBUS Area Load.
As you say
But your instructor appears to have done exactly that. When this same question appeared in your company website, he selected 667 (which matches the AIRBUS Contact Load) as being the correct answer.
You are quite correct in saying that the definition now used in the LO’s, could match either the Airbus 'Contact load' or the 'Area load', depending on the defined area.
The thing that caught my eye in all of this was the fact that both of the numbers given in the original question (667 and 444) could be correct. 667 is correct for the AIRBUS Contact Load and 444 is correct for the AIRBUS Area Load.
As you say
I do not see, given the imprecise definition above, that you can deduce that 'area load'/'floor load' as defined in the LOs = the Airbus term 'contact load'
Last edited by keith williams; 14th Mar 2014 at 16:37.
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That is true, as we have never seen this distinction drawn in the exams we are a bit uncertain how to answer it as an 'exam question'. We are considering whether we should modify the training material to include both definitions but are rather stumped as to what the LOs require.
