Take off distance in j4xx

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peterd
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Re: Take off distance in j4xx

Unread post by peterd » Thu Jan 21, 2010 4:43 pm

any news on the stats ?
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Re: Take off distance in j4xx

Unread post by BigglesSA » Thu Jan 21, 2010 10:07 pm

peterd wrote:any news on the stats ?
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Peter, I am done with a table. I will shortly post a SUMMARY of what we have so far as soon as I get the thumbs up from all involved. The graph however it still a while away. I am done with a prototype plot but we will have to test that very thoroughly before posting.

Sorry for keeping everyone in suspense!!!!!
Last edited by BigglesSA on Sat Jan 23, 2010 9:14 am, edited 1 time in total.
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Re: Take off distance in j4xx

Unread post by peterd » Sat Jan 23, 2010 6:44 am

Thanks biggles. looking forward to it.
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Re: Take off distance in j4xx

Unread post by BigglesSA » Tue Jan 26, 2010 10:55 am

Disclaimer:
This test where carried out under controlled conditions with utmost safety considerations for Pilot and aircraft. This test are for the gathering of information only at this stage and should not be used as performance standards yet. Please refer to the POH for operational standards until our data has been tested and proven accurate!

It was rather interesting how some figure corresponded with the Brits exercise.
Worst run rounded at Brits per kg AUW =1.1m/kg
Worst run rounded at FAVV per kg AUW = 1.2m/kg
FAVV TO distance table of content.jpg
This is where we now need help!!!!

I have played around with the figures, and came out with a FLAT projected ground run distance increase. I would say that the increase should be a curved increase, for both weight and DA. This is where we need the math and stats gurus!!!!!

I refer to an earlier posting by Ben Smit:
BS GRAPH.jpg
This is the sort of graph we should strive to derive. Easy to plot and read. Our graphs should cater for weight and DA.

WHAT YOU SAY?

My thoughts:
Our TO run experiment results cater for the combined effect of weight and DA. Good, but not good enough. I would say that we need to repeat this exercise in future again with at least 4 aircraft. Two aircraft run with the same weight throughout the day, thus providing the accurate DA testing results for the control. The other two must do increase weight runs throughout the day. The runs should be at say 1 to 2 hour intervals throughout the day to record increase and decrease temperatures.

Sias, maybe you can slot this as an activity for the Jabiru Jaunt. We will have the aircraft and the people there to help. MMmmmhhh! Could work!
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Re: Take off distance in j4xx

Unread post by ZuluBen » Tue Jan 26, 2010 12:39 pm

Good job Biggles! =D> =D>

Interesting, Ben's graph looks pretty close to the data at 7500 DA.

Please table and post your Brits data for us as well.

And again, a very special thanks to Phillip, Elaine, Francois, Eddie and Henk, and to all the other assistants and groundcrew =D> =D>
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Re: Take off distance in j4xx

Unread post by BigglesSA » Tue Jan 26, 2010 1:17 pm

Previously posted.

Link to file: download/file.php?id=74268 for Brits data.
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Re: Take off distance in j4xx

Unread post by BenSmit » Tue Jan 26, 2010 8:53 pm

Now if we really want to get fancy, this is what we need.

It is based on the POH of the P166s, you read the first graph, PA, so distance increases as the PA increases.

Then transfer the distance value to the second graph, wind - distance decreases as head wind factor increases

Transfer that distance value to the third graph and add the distance that runway upslope gives.

Now THAT will be great! but there is a LOT of spesific controlled testing required.

REMEMBER thumb suck values input here, do not use it!
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Re: Take off distance in j4xx

Unread post by BigglesSA » Tue Jan 26, 2010 9:17 pm

Spot on Ben, this is exactly what we need =D>
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Re: Take off distance in j4xx

Unread post by NickG » Thu Jan 28, 2010 10:18 pm

Excellent work gents, very interesting too.

Ideally the all up weight should be concealed from the pilot (single blind) and the ground controller-co-ordinator (double blind), perhaps some sort of screen concealing the front starboard side foot-well and rear seats.
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Re: Take off distance in j4xx

Unread post by henk-indabush » Thu Jan 28, 2010 10:58 pm

NickG wrote:Ideally the all up weight should be concealed from the pilot (single blind) and the ground controller-co-ordinator (double blind), perhaps some sort of screen concealing the front starboard side foot-well and rear seats.
Ideally theoretically yes. But ask any test pilot and he will tell you that he will much rather know what he has to deal with than do to a double blind take-off.

I have not studied the results in-depth (will do when at work) but is density altitude not more important than pressure altitude? As we know, PA usually differs very little from elevation, whereas DA is the killer. :shock: I suppose you use DA in your graphs and "mistakenly"call it PA? Or am I missing something?
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Re: Take off distance in j4xx

Unread post by BigglesSA » Fri Jan 29, 2010 9:07 am

Ben illustrated the type of graph we should be striving for. It can be a graph of weight, fuel on board, DA, PA, wind, slope etc.

My opinion is that the two main factors in the life of a Jabi driver will be DA (PA, QNH and temp considered), Weight, Wind , Slope and surface. The two main ones to watch very carefully IN MY OPINION is DA and weight. Huge curved distance increments.

Slope and surface can be safely factored by say 1.2,1.3 etc. after some comparative and check calculations.
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Re: Take off distance in j4xx

Unread post by BenSmit » Fri Jan 29, 2010 4:52 pm

Nick is spot on, I used PA in the example because the POH refers to PA, thats all.
Ideally you will use DA, Weight, Wind and runway slope
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Re: Take off distance in j4xx

Unread post by henk-indabush » Thu Feb 25, 2010 8:27 am

BenSmit wrote:Nick is spot on, I used PA in the example because the POH refers to PA, thats all.
Ideally you will use DA, Weight, Wind and runway slope
Ben, I have been juggling the numbers a bit, your sample graphs are pretty much spot on, will it be possible for you to change the Y-axis numbers to the distances as per tests? Will save me from re-doing all your hard and excellent work!
We may then start testing the graphs - calculate the T/O distance according to the graphs, do the T/O and compare.
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Re: Take off distance in j4xx

Unread post by BigglesSA » Thu Feb 25, 2010 9:17 am

henk-indabush wrote:
BenSmit wrote:Nick is spot on, I used PA in the example because the POH refers to PA, thats all.
Ideally you will use DA, Weight, Wind and runway slope
Ben, I have been juggling the numbers a bit, your sample graphs are pretty much spot on, will it be possible for you to change the Y-axis numbers to the distances as per tests? Will save me from re-doing all your hard and excellent work!
We may then start testing the graphs - calculate the T/O distance according to the graphs, do the T/O and compare.
Ben, we know you are studying, but if you need the figures again I can mail them.

I have also posted a request to MikeA after his excellent post about DA to have a look at our figures for us. Lets see!!!
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Re: Take off distance in j4xx

Unread post by ZuluBen » Thu Feb 25, 2010 12:39 pm

I like the complex graphs as shown above and appearing in the exams, but the reality is that once past the exams, nobody EVER looks at them, especially when there is a load of family and friends around.... :oops:

For my worth, a small graph like one first done by Ben, for DA and weight, with a reminder about grass, slope and wind, business card size that could be laminated and stuck on a dash, is good value.... But that might just be me?
Like this one:
refer to an earlier posting by Ben Smit:


BS GRAPH.jpg (21.64 KiB) Viewed 84 times


This is the sort of graph we should strive to derive. Easy to plot and read. Our graphs should cater for weight and DA.

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