A question for the J model guys

[SET 18]

Guys, I fly often with you all. What a pleasure it is too!

I noticed quite a while ago that all weights of a J are given as AUM, or ZFM (as in Mass)etc.

As you will remember, we in the K world use the last initial W as in "weight"

My question is simple:how so? From my physics days, the equation was always weight =mass times gravity (w=mg) Now the J always talks about masses and not weights.

I am sure this is a simple explanation for this, but aren't all the numbers inaccurate by a factor of 10? (10m/s squared being our gravity force)

Just a question , not a dig or anything, I am just curious. Thanks

[P-T-Gamekeeper]

Technically, we should all be talking mass, not weight. Mass=kg, Weight=Newtons(force)

We both use kg, so you guys should really be calling it a Zero Fuel Mass as well, as we are talking about how heavy it is, not what force it exerts.

I believe the term weight is an Americanism.

[Runaway Gun]

And Mass does not alter with G, but Weight influenced by Gravity (at 9.8 m/s/s) does.

[average pilot]

This is school boy stuff, isn't it ?:ok:

[Now a 'J' Bloke!!]

Hi Gang;:cool:

On the computer thingy we have, the page is called the 'Weight & Balance' with references to things like 'Operating Weight' too. But when you get into some other pages, it is referred to as 'Mass'.

Most 'J' blokes that I know use the term with 100% interchangeability and I often pass a ZFW to the Captain when discussing the load!!!

Clear as Mud, huh!

Notwithstanding that, one 'J' bloke came in last week saying that he wanted to refresh his knowledge of the GTC!!!:confused:

Regards to Most;
'J' Bloke:ok:

[propulike]

As I remember it, the term was changed when someone's career push at Group made Lyneham go metric. It was meant to differentiate between the old system of working in lbs to the new way of working in kgs.

The terms are interchangable in real life though.... ;)

[Wappy Tupper]

... and it was a great idea by the Muppets to simplify things by working on a conversion rate of 1lb = 1kg. ;)

[SET 18]

OK, so as I see it, we are saying that we use mass now on the J solely to differentiate form the K. Is that it?

The argument that we should be using Mass and not weight is incorrect I think, because we are talking exactly about somethings weight, not it's mass.

The aircraft flys (by nature of the fact that we are on Earth) with regard to weight. Does it not? (honest question, not sarcy back-up) I still think that the J model definition is wrong, and that weight is the more correct term to use. As I said before, weight= mass times gravity or force =mass times acceleration.

These are essentially both the same equation

[propulike]

J and K both use kgs - the conversion of the K to kgs happened before the J arrived and the J was procured in kgs. Don't ask me why, it was just a silly idea that no-one on high ever stopped.

As for weight and mass, mass is constant, weight varies depending on how much 'g' you pull.

[P-T-Gamekeeper]

If we should all be using weight, you should have a typical ZFW of 450 N (newtons), unless you are pulling g, then your loady should rapidly inform you that the ZFW has increased to 900 N.

also g = GMm/r2 so as your altitude increases, so should your weight.

All sound a bit too much? Yes, I think we should all be using ZFM after all!

[amb_211085]

But that said, there would be very little difference in g using that equation as I'm guessing the accuracy in measuring the variables would not be accurate enough to have a noticable effect.

As an aside, take up flying in gliders, the only weights you need to worry about are if the person in the front is too light or too heavy then you add and remove respectively! Easy, save all this curfuffle.

[SET 18]

Yes, but if a J model gives its ZFM of 39tonnes, then surley this is wrong. It WEIGHS that much. Its mass is apporoximately one tenth of this total. If it really did have a Mass of this much then it would weigh 390 tonnes on the pan.

The aircraft behaves according to its weight, not it's mass. So why do they call the 39 tonne figure a mass? It is not a mass it is a weight.

So surely the J should be calling the figures ZFW and AUW like the old K. As i said before, to call them AUMs makes them inaccurate by a factor of ten.

[Runaway Gun]

Can someone error check me please.

If my Mass is 100kg, then my Weight (at 1 G) is 980 Newtons.
At 2G's my Mass is 100kg, and my weight is 1960 Newtons.

Body Mass Index medical charts will have to become 3 dimensional to represent this...


That's a requested Gross Error Check, not Net ;)

[Now a 'J' Bloke!!]

SET (a ludicrous power setting....)

You said at the start of this thread that you were not procrastinating......:rolleyes:

Now you are splitting hairs after several posters (inc me) said that the difference in mass or weight didn't matter....

On the ramp...weight is the same as mass....:ok:

On acceleration or intro of 'G' Forces...(fairly limited on the C130..as against other pointy things)...the performance/Vs/ Vcma graphs should account for the acceleration curves...

Stop Arguing!!!:mad:

Regards to Most..
'J' Bloke:cool:

Edited for Red Wine SSpelling (hereby known as RWSs)

[SET 18]

Not a J bloke: I don't mention procrastinating at any stage.

My point is that the fugures given are not masses they are weights. Aren't they? I know that, because g is constant (vitrtually) on our planet, the mass in relation to the weight remains the same, but the figures given by the J are weights, not masses.

So why are they called masses?

[P-T-Gamekeeper]

SET 18

You appear to be confusing yourself. The word WEIGHT has been americanised. Scientifically, weight relates to a force. The word "weigh", in comon usage, is being misused.

Weight is a force - eg on earth a 10kg object exerts a gravitational force of 98 N - It weighs 98 N - It has a mass of 10 kg.

Just because your ACM calls it a ZFW does not make it scientificly correct.

I suggest a seance with Isaac Newton to straighten this out.

As you say in an earlier post Weight = Mass x Gravity or F = ma or in SI unit terms N = kgms2. Is your ZFM/ZFW or whatever you use measured in Newtons or HP? No - it is in Kg, so it is a mass.

[Now a 'J' Bloke!!]

SET (something)

If you remember physics...

W=MA

Weight equals mass x acceleration.....

therefore mass is the constant...add acceleration ( eg.. in a turn or take off roll and weight will increase) Result ...weight is the variable.

Are you an Air Eng...that may explain it... we don't have them, which is why we get on with the job rather than worrying over some grammar sh1t

I'm getting tired now...

Edited for RWS

Regards to Most
'J'Bloke

[Pass-A-Frozo]

also g = GMm/r2 so as your altitude increases, so should your weight.

As your altitude increases your weight decreases. Otherwise the further away we are from an object, the greater the attraction between the two bodies of mass.

I would have thought the whole thing is simple. Weight in Newtons, Mass in Kilograms or pounds.

:ugh:

[P-T-Gamekeeper]

Oops - I knew what I meant - good spot.

[BEagle]

With the exception of the correct use of units in aerodynamics and principles of flight, for all intents and purposes, the words 'weight' and 'mass' are synonymous as far as aircrew and loading personnel are concerned.

JAR-OPS has tried to introduce 'mass', but most people are ignoring it and sticking to 'weight'.

Still, it could be worse - we could go back to 'slugs', 'poundals' and all the other schoolday horrors of the Imperial system of measurements..... 'Rods', 'Poles', 'Perches', 'Pecks' - and perhaps measure speed, oops, 'velocity' in furlongs per fortnight?

[EasySqueezy]

I hear that the microwave in the J is very good. Are the pies measured by weight or mass?

[Always_broken_in_wilts]

Microwave is ok but some of us do miss the potential of the oven to produce the odd "speciality" dish:ok:

As regards pies we all know that the content constant is directly proportional to the average of the "kipper fleet circumference":E

all spelling mistakes are "df" alcohol induced

[Pass-A-Frozo]

Microwave is ok but some of us do miss the potential of the oven to produce the odd "speciality" dish

Get your friendly loady to bring an oven and plug it in down the back. :D

[Always_broken_in_wilts]

I am friendly, I am a loadie, the plugs in the back, and front "work", where do I get the oven from:ok:

all spelling mistakes are "df" alcohol induced

[Pass-A-Frozo]

Dunno about your particular country. Can't you rob a K model? :E