However, like all "rules of thumb" in aviation, it is conservative. That is why aircraft structure limit loads are ALWAYS at least 25% below their design loads.
>No science at all, only BS. > >Most netters already know this, but just in case ...... > >If the aircraft weighs 900lb, then 1G (gravity) is 900lbs. >The rated load factor of 7G means the relevant part of the structure was >tested /calculated to withstand seven times static weight - it can thus >handle 7x900=6,300lb - that is what 7G means. > >You can literally put 6300lbs* of sand bags on the wing (properly spread >out to represent the load) to establish the -G limit - or load the >inverted airplane to establish the positive load factor. > >The structural strength does not change if we make it heavier, so the >tested or calculated capability is still 6300lbs. If we add another >100lbs of structure, fuel, cargo, passenger etc., the MAUW will be >1000lbs and the G capability will be 6300/1000=6.3G (not 7-1=6G) > >If we add 400lbs (increase the MAUW to 1300lbs), then 6300/1300=4.85G >(not 7-4=3G) > >Apply this rationale to a Cherokee typical MAUW of maybe 2000lbs and a >load factor of +5.6G > >2000x5.6=11,200. > >Apply the BS rule (1G /100lbs) > >2100lbs reduces the LF to +4.6G?? > >The truth: 11200/2100=5.33G > > >When we talk about load factors it is important to know: > >The aircraft has a CALCULATED load factor of +7G / -7G? >Or, the aircraft has a DEMONSTRATED load factor of .......? > >Tested (loaded) to +7G with no permanent structural damage /distortion? >Or, tested to destruction, i.e. failed (or permanent damage) at +7G >(often referred to as the ultimate load factor). > >Everything in /on the airplane is subjected to G forces, not only the >wing. A fuel tank could pop out the bottom of a wing if the mountings >are not capable of restraining the load of the tank plus fuel at X times >its static weight. Counter-balance weights (elevator) were discussed on >the net recently - they must also be able to withstand any G loads that >the airplane may be subjected to. > >We generally see G loads as pilot induced - steep turns, pull-ups etc. >The discomfort of G forces will keep the pilot aware of the effects - >may even cause him/her to black-out. (The blood trying to get to your >brain is also subjected to the same G load (acceleration). > >G loads caused by turbulence scare me, they are invariably unexpected >and can be very harsh. They are instantaneous, leaving no time to take >any compensating action. That is why store bought airplanes have a >placarded manoeuvring speed > > >(* not strictly true - some of the wing weight will be excluded) > > >Have a great weekend > >Steve J > > > > >_______________________________________ >to UNsubscribe from KRnet, send a message to [email protected] >please see other KRnet info at http://www.krnet.org/info.html Larry Severson Fountain Valley, CA 92708 (714) 968-9852 [email protected]
