FAA Accident Report discrepancy.

On 17/07/2011 19:09, Bruce Hoult wrote:

http://en.wikipedia.org/wiki/Cessna_172

Empty: 1691 lb
Gross: 2450 lb
Rate of climb: 721 fpm (at gross as these things are)

Useful load: 759 lb.
Fuel: 56 USgal, 212 litres ~= 170 kg, 374 lb

Four adults and golf clubs? Maybe 800 lb?

Come on! Each man AND his golf clubs (up to 14 clubs, bag, balls, etc)
weighs only 200lbs total??

And nobody took a change of underpants? Deodorant? Shaving cream?
The aeroplane didn't have a fuel drain test set? A litre of oil? A
tiedown kit? Control locks? Chocks? Maps, Jeppesen, GPS? No
instruments installed? No u/c spats full of mud?

Here's what's realistic:
The 4 men and their overnight bags weighed about 400kg (880lbs)
The four bags of golf clubs (and balls, shoes, etc) weighed 40kg (88lbs)
minimum.
The fuel SG was .75 max so the fuel weighed only 160kg (say 350lbs)
The 172 was one of the vast majority with max wts of 22-2300lbs.

So It'll be overloaded by about 415 lb, weighing a total of about 2865
instead of 2450, or about 17% overload.

I do the maths differently. It was probably overloaded by between 25 -
40% and the density altitude was probably significantly above the MSL
from which it will climb at 721fpm (I love that "1").

I find it very hard to believe that an aircraft that can climb at 721
fpm at gross weight can not fly at all with a 17% overload!

Use more runway, sure. Climb slower, sure. But not fly? Inconceivable.

You're quite right, Bruce. Of course it will fly - eventually. But I
have a reasonable amount of tired 172 time behind me and I'm with the
guy from the FAA. For all practical purposes - it won't fly.

GC

On Jul 18, 6:30*am, GC wrote:
On 17/07/2011 19:09, Bruce Hoult wrote:

http://en.wikipedia.org/wiki/Cessna_172

Empty: 1691 lb
Gross: 2450 lb
Rate of climb: 721 fpm (at gross as these things are)

Useful load: 759 lb.
Fuel: 56 USgal, 212 litres ~= 170 kg, 374 lb

Four adults and golf clubs? Maybe 800 lb?

Come on! *Each man AND his golf clubs (up to 14 clubs, bag, balls, etc)
weighs only 200lbs total??

Four sets of gold clubs? OK, sure, that's a big difference. I read it
as four people and one set of clubs.

I do the maths differently. *It was probably overloaded by between 25 -
40% and the density altitude was probably significantly above the MSL
from which it will climb at 721fpm (I love that "1").

Yup, that's getting to be extremely dodgy unless you've got a runway
suitable for a 747, at sea level. I sure wouldn't try it.

I absolutely agree that you've got to take the limitations seriously,
but I do get annoyed at people who say "we'd be 10 lbs over gross
weight so we can't fly". Which I've been told multiple times, at
different places.

A lot of pilots don't seem to realize that published specifications
are huge compromises. Sure, manufacturers like to be able to advertise
high payloads, but they like to be able to quote short takeoff
distance and high rates of climb even more –*far above what is
actually necessary for many flights. Those things can be traded off
against each other, over some limited range of values.

(and of course cruise speed, service ceiling, allowed maneuvers all
come into it too)