"Lift Loading"

[hitech]

hitech i asked you this on another board, sort of.

are there some planes that for one reason or another much more difficult for you to get a FM that you feel very successful about?

or aspects of flight in general that are just hard to get "right" on a computer ...

i ask just because i think of some things like say "how a 38 rolls" you know "neutral" torque not on the center line etc, slat effects in the 109 ...

i just think how the @$%$ would someone approach such different aircraft in a computer representation.

nothing but sincere interest and a chance for an interesting discussion, not suggesting you have not achieved good results sir, i just think insights into the problems and problem solving would be very interesting.

i understand if you might be apprehensive with this question and or me posting it considering past discussions.

i am just interested/curious ...

What you believe is difficult i.e. the 38 engines quite frankly is trivial, I am making an assumption you have never had much physics or calculus if am I wrong I apologize but to put it simply , torque is torque no mater where it is applied on an object, the net result is the same. So the engine modeling is 100% the same for a p38 or any other plane. You just change 1 +- sign and apply all forces to a different point.

The modeling of things like slats again is fairly simple, finding all the correct numbers on slats can be difficult, and when some thing is missing in the data trying to find a method to extract it from other know data points can take a lot of work.

The basic modeling system is very simple physics. You  first calculate a Mass and a Moment of Inertia,(changes only with fuel consumption and expending ordinance) then start calculating and summing up forces on the object. When you have them all summed up, you use the simple equations A = R / M , V = A * T + OldV, and P = V * T  + OldpP For the 6 axis and wala, you have a new plane position, rinse and repeat.


HiTech

[thorsim]

i just thought the torque not being on the center line would effect the roll character and wondering how you approached it.  in films the 38 always seems to have a drift in its roll like a little barrel roll just different than a plane with the engine on the center line.

but those were things that struck me as seeming to be difficult, i was more asking about your problems and problem solving day to day coding work.  what if anything you find more challenging than others ...

just curious ...

a little sympathy for the devil

+S+

t

 

[hitech]

i just thought the torque not being on the center line would effect the roll character

Torque not being on center line has absolutely no effect.

HiTech

[thorsim]

Torque not being on center line has absolutely no effect.

HiTech

yea ok, i really wasn't trying to start an argument, i just was inviting you to share the "interesting" parts of what you do.

[hitech]

The reality is most of my time is not all that interesting. 95% of a programmers life is trying to figure out how we screwed up.

For instance right now I am working on the fixed pitch prop model for WWI lots of trying to find information to verify methologies. Which requires lots of reading, and again more testing and fixing what I screwed up on.

[gyrene81]

The reality is most of my time is not all that interesting. 95% of a programmers life is trying to figure out how we screwed up.

For instance right now I am working on the fixed pitch prop model for WWI lots of trying to find information to verify methologies. Which requires lots of reading, and again more testing and fixing what I screwed up on.

I have several extra boxes of Tylenol I can send you...got them at closeout prices when a nearby pharmacy closed down...   

Sadly no whiskey though... ...none of the liquor stores seem to be having money problems these days so I can't get it cheap.

[gripen]

The lift equation is the consensus.  If you know the speed of an aircraft, you can compute the Clmax at any condition.  Now, if you're interested in breaking out the varying components of the plane, and their contribution to lift, there are different methods used (for example, to determine the fuselages contribution) but overall, the lift equation tells you everything you need to know.

Eh... We can calculate coefficient of lift (Cl) at any condition using lift equation (altitude, speed, weight and wing area), no problem. However, we are talking about the proper value of Clmax, 1g stall speed gives some idea but it's not particularly accurate at the other conditions.

[Stoney]

Eh... We can calculate coefficient of lift (Cl) at any condition using lift equation (altitude, speed, weight and wing area), no problem. However, we are talking about the proper value of Clmax, 1g stall speed gives some idea but it's not particularly accurate at the other conditions.

Which other conditions?  I'm not trying to be obtuse, just understand your statement.  At any condition, the lift equation will tell us the necessary Cl for that condition.  Obviously, its a static condition, but if we're merely comparing aircraft, and not trying to derive how much lift the wing is producing by itself, for example, it works.

[gripen]

Which other conditions?  I'm not trying to be obtuse, just understand your statement.  At any condition, the lift equation will tell us the necessary Cl for that condition.  Obviously, its a static condition, but if we're merely comparing aircraft, and not trying to derive how much lift the wing is producing by itself, for example, it works.

See above how hitech defined lift loading. It's not about what is the Cl at given flight condition but what Clmax can be reached at given conditions. As an example see page 28 in the document below.

http://naca.central.cranfield.ac.uk/reports/1946/naca-tn-1044.pdf

That example is at high altitude but same way Clmax varies also at low altitude depending on speed, power setting, flaps etc.

[Ardy123]

The reality is most of my time is not all that interesting. 95% of a programmers life is trying to figure out how we screwed up.

For instance right now I am working on the fixed pitch prop model for WWI lots of trying to find information to verify methologies. Which requires lots of reading, and again more testing and fixing what I screwed up on.

Just out of curiosity, where do you find info such as the clmax of a particular airplane wing?
Especially for WW1 airplanes, did people actually understand that stuff back then, I thought most of that technology was developed in the 20s. I was under the impression that most early airplanes were almost, trial and error, complete with strange wing & airfoil shapes and odd control surfaces (such as wing warping, etc).
 

[Ex-jazz]

See above how hitech defined lift loading. It's not about what is the Cl at given flight condition but what Clmax can be reached at given conditions. As an example see page 28 in the document below.

http://naca.central.cranfield.ac.uk/reports/1946/naca-tn-1044.pdf

That example is at high altitude but same way Clmax varies also at low altitude depending on speed, power setting, flaps etc.

Thanks Gripen,

Very interesting document.

[Charge]

"Eh... We can calculate coefficient of lift (Cl) at any condition using lift equation (altitude, speed, weight and wing area), no problem."

What do you mean?

Cl=L/qA where L is Lift force and q is dynamic pressure and A is planform area and the L is not a simple component to determine.

http://en.wikipedia.org/wiki/Lift_(force)

However the linked document nicely represents how complex the calculation gets when the profile is also considered. Nice link, thx.

-C+

[Stoney]

"Eh... We can calculate coefficient of lift (Cl) at any condition using lift equation (altitude, speed, weight and wing area), no problem."

What do you mean?

Cl=L/qA where L is Lift force and q is dynamic pressure and A is planform area and the L is not a simple component to determine.

http://en.wikipedia.org/wiki/Lift_(force)

However the linked document nicely represents how complex the calculation gets when the profile is also considered. Nice link, thx.

-C+

If you know the weight of the aircraft, the speed of the aircraft, and the altitude of the aircraft, the lift equation will give you the Cl at that weight and speed.  If you know the weight of the aircraft, the stall speed of the aircraft at that weight, and the altitude of the aircraft, the lift equation will give you the Clmax at that weight, regardless of aspect ratio, "e", or anything else.