Orgins of Occupant Mass

[verymadmac]

So for FAR23 "post dynamic seats", "pre ASTM", the minimum occupant mass is 215 lb. Can any point me in the direction of a report regarding the origins of this limit, it doesn't seem to be in NPRM. Basically I want to know does it have a statistical basis.

My current interest is regarding a step on a GA passenger aircraft. All passengers use it all to on and off the aircraft, and since gust loads and emergency landing loads are occasional loads, there is several orders of magnitude difference in the occurrence rate. In practice I am just going to use 275 lb which is 95 percentile mass & just want a good reference supporting the use of a higher mass.

 

[LittleInch]

Try this and following the links embedded in it?

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_120-27F.pdf

There's a lot of links saying the new passenger weights to be used increased around this time 2019-2020.

Also try this?

https://www.cdc.gov/nchs/fastats/body-measurements.htm

and

https://www.cdc.gov/nchs/data/series/sr_03/sr03-046-508.pdf

tables 4 and 6 might help?

From those tables the 95th percentile male max looks more like 308 lbs (!), NOT including the weight of the carry on bag they are holding or clothes they are wearing, so maybe add 10-15 lbs to any of your body weight numbers?
y
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[rb1957]

"minimum" occupant "mass" ? ... maybe maximum [1] occupant weight ?

[1] maximum from a certification perspective, since we know the real maximum is higher !! Makes you would why seats aren't placarded ?? obviously because people don't want to be weighed at check-in

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[verymadmac]

"minimum" occupant "mass" ? ... maybe maximum [1] occupant weight ?

FAR 23.785 (a)
Each seat/restraint system and the supporting structure must be designed to support occupants weighing at least 215 pounds when subjected to the maximum load factors

If I had to quote it off the top of my head, I would have gone with a 215 lb being a max. It does have the feel of a giant can of worms that everyone is trying hard not to find.

From those tables the 95th percentile male max looks more like 308 lbs (!), NOT including the weight of the carry on bag they are holding or clothes they are wearing, so maybe add 10-15 lbs to any of your body weight numbers?

Its a step and a grab handle, so I am not inclined to worry about carry on.

I had found the raw data sets but not the "National Centre For Health Statistics, Vital and Health Statistics" report.

The 275 lb was the average of the 95% weights between both sexs (yes its less than great math). Playing with this Link which uses the CDC data sets, the numbers appear to go pretty asymptotic about 95%. In reality, discounting the anomaly of professionals sports people, the upper practical limit is probably set by the physical ability to use the step but only god knows what that number looks looks like, so 95% it is at this point.

The FAR requirements were set in 1988, I note the text book I normally use for this type of data was published in 1996 and its 95% percentile male weight is 59 lb light of the current data set.

 

[SWComposites]

Basically I want to know does it have a statistical basis.

LOL, it probably does, but it is likely based on FAA voodoo/political statistics which you will never find documented anywhere. Everyone knows the FAA cert weights for passengers should be higher, but they won't change them as it would have very significant effects on aircraft manufacturers and operators. So its likely not going to happen short of a Congressional mandate to change them.

 

[rb1957]

ok, what an oddly worded requirement ... "at least" ?? so someone lighter can't sit there ??

but you've got a step ... ok, abuse load ... some people use 300 lbs (limit or ultimate) and a "dynamic load factor" of maybe 2.

Frankly, I'd apply a "hopelessly" conservative load that "no one" would question ... maybe 1000 lbs ? The impact on your step design should be minimal.
I guess an advantage is no flight loads, no impact to flight safety ... maybe more an OHSA requirement ??

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.