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Author Topic: Climb Vrs Acceleration Part Deux AFDU data  (Read 703 times)

Offline niklas

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #15 on: July 21, 2002, 06:47:10 PM »
And at which airspeed do you start the inital acceleration?

Imagine a fighter that has a stall speed of  50mph, the other at 100mph. Now how do you want to compare initial acceleration at 75mph when the 2nd aircraft can´t even fly at this speed????

Imagine a aircraft with a topspeed of 300mph, the other of 400mph (Similar shape, just different engine). Of course the 2nd aircraft will accelerate faster at 295mph where the other one is very very close to its own topspeed.

So where did they start the acceleration process? You have to know it, else it´s useless.

The AFDU made some dive acceleration comparisons, maybe this accelerations refer to dive acceleration.

niklas
« Last Edit: July 21, 2002, 06:49:29 PM by niklas »
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Offline Holden McGroin

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #16 on: July 22, 2002, 08:10:57 PM »
perhaps initial accelleration is the wrong term...

dv/dt is a better definition, at whatever V your interested in...
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Offline niklas

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #17 on: July 23, 2002, 07:07:10 AM »
Right, but dv/dt is a curve, with endless many data points. This chart shows only ONE single point out of it, the reference for ONE conditition. So if you want to interpret this table, you have to know WHAT single point they took out of a large group of possibillities.
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Offline F4UDOA

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #18 on: July 23, 2002, 11:41:55 AM »
Niklas,

Don't you think it's curious that the Acceleration of the Tempest is not as good as the P-51 and only marginally better than the P-47??

I would think the Luftwaffles would be all over this??

BTW, this is the second set of test data I have provided with A/C climbing and accelerating in a different order. I guess actual test results don't account for much?
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Offline hitech

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #19 on: July 23, 2002, 03:28:10 PM »
F4UDOA: You are turning into a true posting duffas.

When mutliple people all with degrees in  math,physics,eng excetera, are all telling you the exact same thing. I would tend do belive them first, then try figure out why the document is confusing you, not try show how all these people are wrong.

Read, belive, try to understand, what we are trying to tell you. Wrather than grasping at straws trying to prove somthing that is incorect.
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Offline BigGun

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #20 on: July 23, 2002, 04:22:54 PM »
Quote
Originally posted by hitech
F4UDOA: You are turning into a true posting duffas.  


All right..there is my laugh today...back to work
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Offline Puke

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #21 on: July 23, 2002, 06:01:33 PM »
I've actually found this thread very interesting and have been following it.   In my opinion, Hitech's post was a bit nasty and really uncalled for...I think he must be taking something personally (which maybe I'm missing.)  Anyway, some people like to understand facts instead of just accepting them on face value.  Kudos to all those who are taking the time to help those of us who are without the knowledge try to understand how it works.

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Offline Puke

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #22 on: July 23, 2002, 06:03:00 PM »
Stupid freakin' BBS kept timing out on me trying to post this...now there are two.  Let's see if 3 show up now.

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Offline F4UDOA

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #23 on: July 23, 2002, 08:20:02 PM »
Hitech,

I think Pyro should censor your post and ban you from the boards for name calling:o

Seriously I've been called allot worse than dufus even just today.

However if I am a dufus I guess the pilots that flew the AFDU were also. As well as the pilots that from SETP that flew the A/C in 1989.

What I see on these boards is a number of people with a greater understanding of the math behind flight than I do. What I do not see is any explanation of the data I have presented. I'm not trying not to see it. In fact I'm trying very hard to see it.

Please humor one more time.

Maybe I have chosen a bad example. Take a look at the FW190A. It is at both ends of the spectrum and at all altitudes near the worst in climb and top speed, but near the best in acceleration.

If someone with better math skills than I using the data I have provided explain why the FW190A is at different ends of the spectrum in climb and acceleration as shown clearly in this test.

Please do not show me a generic equation. I have Aeronautics books too. But I do not have the backround to put together these equations.So please stop being so condesending and do the math.

I'm a big boy so you can call me names. But if it were not for people like me asking why people like you would still think the earth was flat;)
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Offline wells

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #24 on: July 23, 2002, 08:58:57 PM »
DOA,

Compare the 190 vs Meteor.  The 190 will outclimb the Meteor at whatever speed and height the 'initial acceleration' test was done at.  Likewise, when flown at the Meteor's best climb speed of 220 mph, the Meteor will accelerate better.  The speeds have to be the same if you're going to compare climb and acceleration directly.
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Offline bozon

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #25 on: July 23, 2002, 09:08:02 PM »
F4UDOA,
this acceleration/climbrate problem has enough variables in it to allow just a bout any possible result.

If you wanted to show that the p-47 was a better plane than the spit, you could do the tests at 400mph. the p-47 in some speeds and altitudes will outclimb and out accelerate the spit.
on other conditions it won't.
actually on most of the possible spectrum of condition it won't so we say the spit is a better climber than the p-47, and so on.

If the guys that made the report really wanted to get a certain conclusion, they will get it, more or less. you can see this happening in reports in science and medicine as well.

I can't for some reason view the first pic you attached now (I could on the univercity computer), so I can't see what what conditions the experiment was done. anyway, the data will only tell a part of the story.

Bozon
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Offline Mino

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #26 on: July 24, 2002, 05:23:00 AM »
Quote
Originally posted by Holden McGroin
Initial accelleration is the accelleration that happens initially.

If we are talking level acceleration, and that is the only acceleartion that horsepower has anything to do with, then just after you max out the throttle, initially, that is initial acceleration. :)  Otherwise, a rock initially accelerates at 32.2 ft/sec sq

The thing that makes the difference is aerodynamics.  Drag at whatever the climb speed is varies greatly among all these designs. The aerodynamic qualities of the wing, prop, and fuselage make a great deal of difference. Excess horsepower is not the only climb factor; weight and aerodynamics balance the equation.


A rock?  No way, I am sure we are not talking rocks here.  Apples maybe?  Holden are you really I. Newton incognito?

BTW to all you pin head aeronautical ninjaqueers, I'm with F4UDOA all the way on this one.  At least I can understand what HE is complaining about, for the rest I have no clue. :)
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Offline Cogen

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Rocks - Who said anything about rocks?
« Reply #27 on: July 24, 2002, 05:33:27 AM »
Quote
Originally posted by Holden McGroin
Initial accelleration is the accelleration that happens initially.

Otherwise, a rock initially accelerates at 32.2 ft/sec sq


There you go again messing everything up by throwing rocks into the fray.

OK, what kind of rock; granite, quartz, or pumie.

I just got interested in the alphabet that was preceeded by the letter "d"  (i.e. dv/dt).  What does "d" mean?

Can it accelerate also?;)
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Offline Guppy

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #28 on: July 24, 2002, 08:09:21 AM »
For a current perspective, http://www.dfrc.nasa.gov/trc/ftintro/accel/nasaccel.html discusses the NASA Dryden Flight Research Center's procedures for level acceleration tests.

Note the document states that level acceleration results are directly used to compute maximum rates of climb.

One point about the Fw 190A--it's stated in a US test report that the 190A had an advantage in acceleration tests because it had simpler engine controls than US fighters, and full power could be applied more quickly. Depending on the test procedure, this might have been enough to bump it up the acceleration rankings a bit.
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Offline F4UDOA

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Climb Vrs Acceleration Part Deux AFDU data
« Reply #29 on: July 24, 2002, 10:05:58 AM »
Quote
F4UDOA,
this acceleration/climbrate problem has enough variables in it to allow just a bout any possible result.


Thank you Bozon. You just made my point for me.

Quote
DOA,

Compare the 190 vs Meteor. The 190 will outclimb the Meteor at whatever speed and height the 'initial acceleration' test was done at. Likewise, when flown at the Meteor's best climb speed of 220 mph, the Meteor will accelerate better. The speeds have to be the same if you're going to compare climb and acceleration directly.


Wells, like you said the speed has to be the same. And thats not all. How about AoA. That has to be the same as well or you can't compare Cdi either. My point is that there are many variables in to determine best climb because speed and AoA vary when measuring climb but have nothing to do with level acceleration.

So if my last staement is true then you can say that climb and accleration are not directly linked because climb uses more variables

For instance. How can you say that an A/C has high induced drag if you don't know what the Cl is at the AoA used in it's climb?? And none of that matters in acceleration. Is this not a true staement??
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