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Author Topic: Eco - Could you answer a question?  (Read 4657 times)
TX-Gunslinger
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« on: January 05, 2010, 07:57:17 pm »

Eco,

I remember discussions that we've had about "time-to-altitude" type tests.  Some tests are done from "wheels up" and some are done from when the aircraft starts rolling down the runway.

If you were going to test climbing rates in some sim - how would you do it?  What reference would you use....

2nd question,

Let's say I'm trying to achieve maximum ROC in an aircraft - how do I know what IAS should produce max climb?

Thanks

Gunny
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GOZR
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« Reply #1 on: January 05, 2010, 08:50:52 pm »

In RL ?
You'll find this useful , There is different methods but here a little sample quick find online. (We do this quite often )

Here sample book of the test Sawtooth..

For you gunny:
Books here
« Last Edit: January 06, 2010, 01:07:53 pm by GOZR » Logged

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« Reply #2 on: January 06, 2010, 03:28:19 am »

Yep - it's the sawtooth climb that you're looking for:

http://www.dfrc.nasa.gov/Education/OnlineEd/Intro2Flight/nassawt.html

Be advised that it takes  lot of time to do this correctly.

"Time to Climb" values are usually based on the time from brake release to a given altitude. . .this is not rate of climb data.
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« Reply #3 on: January 06, 2010, 11:25:07 am »

Thanks guys!

I'm trying to apply this to a particular sim. 

More later - Off to work.

Really appreciate the links......

S~

Gunny
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« Reply #4 on: January 06, 2010, 11:30:42 am »

So basically ROC data is compilied from the data derived from multiple sawteeth?

S~

Gunny
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« Reply #5 on: January 06, 2010, 01:06:49 pm »

Well the sawtooth is basically to find the best speeds, angles etc.. cross wind flight .. Read it well..

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« Reply #6 on: January 07, 2010, 12:02:32 am »

So basically ROC data is compilied from the data derived from multiple sawteeth?

S~

Gunny


Yes. . .essentially you will establish a climb using climb power (remember to set mixture) at a given airspeed and heading, and plan this such that airspeed has stabilized once you cross the floor of the altitude range which you are testing the ROC. Timing starts once you cross that altitude floor, and ends when you cross the upper limit of that altitude range. So for initial ROC determinations you would fly fairly low over the ground at an airspeed close to that which you will use for the climb, and then pitch up while adding throttle to climb power and adjusting pitch to control airspeed. After this you will want to maintain this power setting, keep the wings level, maintain coordinated flight, and focus on maintaining a constant airspeed. Once you cross through the altitude block you will repeat this test at a slightly different airspeed,

So suppose you wanted to determine the ROC from 500 feet to 1,500 feet, and terrain elevation is 50 feet, and you think the best rate of climb airspeed is somewhere between 60 and 70 knots. As such you will want to pass through this altitude range multiple times at slightly different airspeeds. . .in this example you might use 60, 65, 70, 75, 80 and once you've found the two highest ROC values for those data points say 75 and 80, you will then use smaller airspeed increments to find the exact speed at that altitude range. Once you have found Vy (best rate of climb speed) for this altitude range you will then move the altitude range up and perform the test again at that altitude. As you climb Vy will decrease so you should have a fairly good idea as you climb what speeds should get you close.


« Last Edit: January 08, 2010, 02:56:49 am by TX-EcoDragon » Logged

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« Reply #7 on: January 08, 2010, 12:55:34 am »

Thank you!!!!


I got it.  Seems to me (prior to attempted practical application) that the biggest challege in the flying will be to maintain the constant airspeed, consistently, but I can do it if I manage (select) the segments limits (in altitude) wisely.

If I'm testing aircraft whose maximum level flight speeds are less than 230 Kmh (best climb speeds I'm guessing are a fraction of this value) - then I should be able to get by with IAS values and not have to deal with TAS measurement or conversion.

I've made some progress on building missions which are orientated to testing.  I have one for example, which I made to test sustained turn rates - by placing balloons on cardinal compass points at the same altitude.  By recording a track, and the replaying it a 1/4 speed - I can get decimal point measurements of time to conduct 360 sustained turns.

I'm conducting the initial turn tests by flying level to say the 000T balloon, then rolling into my turn and waiting to measure until transistion to sustained turn state.  Sustained turn (to my understanding) is the point at which I'm maintaining altitude and airspeed does not get to stall.

As I've done a few of these tests, who's results seem reasonable - I thought I'd start working on some way to measure climbing performance - for plane to plane comparisons and to be able to document best performance envelopes for these simulated aircraft.

Good to hear from you,

S~

Gunny
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