Gums
Forum God
 
Registration Date: 03-25-2002
Posts: 2824
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| Groundspeed is true airspeed? |
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Salute!
Way I see it is that the "ground speed" we see is true airspeed ( TAS).
The TAS is the primary velocity vector for any 3-d reference frame. It's velocity thru the airmass. So if we have a "wind", the airmass reference frame is moving across the geographical frame - the xpos, ypos. No vertical component.
So I did a loop and sure enough, the third data entity in the hudrecord file stayed right with the IAS (mph for Goebel's script). It was TAS, not GS. The actual HUD display that says GS was the same, and it should have gone close to zero regardless of my IAS. My HUDRECORD file showed the same.
So conclusion? We are seeing the basic velocity vector thru the airmass. Now all we have to do to confirm this is to enter wind or get on a boat.
FOR MOUSEY!!!! You might want to try to find a few strings that increment the xpos/ypos. Somewhere in there there's a variable that represents the velocity vector, and it this doofer that is also gonna be used for firing your guns and for calculating where your bomb hits ( basic dive bomb), etc.
So I'll ask the beta team if the velocity vector can be obtained. It may be the "mph" value of the no sierra velocity vector corrected for air density.
Meanwhile, I'll also try to run Goebel's script along with the HUDRECORD to see what is being recorded by both scripts for "MPH". The xpos/ypos data strings I get should also provide the horizontal velocity, i.e. the actual ground speed.
Gums sends ...
__________________ Gums
***305th BG(H)***
God in your guts, good men at your back, wings that stay on- and Tally Ho!
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02-11-2010 11:51 |
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Gums
Forum God
 
Registration Date: 03-25-2002
Posts: 2824
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| FltLogger versus HUDRECORD |
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Salute!
Thanks Mouse and Goebel. So I award Mouse-breath 15 Gums' "attaboys".
So I flew with both the fltlogger doofer and the HUDRECORD doofer running at the same time.
1) Same data. Hooooray!
2) The HUDRECORD has gaps, FltLogger has zero gaps, heh heh.
I have to fly again to make sure, but looks like the HUDRECORD is a no sierra HUD recorder. Huh? So we buff pukes use the Nord front view to make smooth turns and retain the otto-pilot climbspeed or alt hold. When we are in the Nord we lose the basic HUD display.
So being the old data reduction expert ( read about ATARS recce system from early 90's), I deleted the extra data records from FltLogger to agree with the HUDRECORD records. perfect match. In fact, the HUDRECORD is not exactly the entered increment, and Goebel's FltLogger is exactly what you set. So the HUDRECORD 5 sec interval was slightly more than 5 sec, like 5.05 or something. After 40 or 50 intervals it was off by a second, then it kept going that way. No biggie.
3) The FltLogger "GAUGE" MPH agrees with the HUDRECORD value. So the TAS, or GS we see in the HUD display is TAS, not actual GS. Did some more loops and watched the "GS" remain just what it should be for TAS, not actual velocity across the ground ( going strtaight down we should see close to zero GS, heh heh).
+++++++++++++
So what does all this mean?
It means we can use Goebel's FltLogger to get almost anything we want except the actual velocity vector in the airmass.
For flight test purposes, it's not hard to get TAS from the IAS and ALT. I have a second order polynomial that is extremely accurate, but for practical purposes you can use the following and it will get you within a mph or two up to 25K:
TAS=IAS+IAS*(ALT*.02), where ALT is thousands of feet. Or, TAS=IAS*(1+ALT*.00002), where ALT is in basic feet. I was taught this "2% rule" by a mossback fighter pilot in my first ops unit, and it works. So at 25K you are going 50% faster than your IAS gauge reads. At 50K you're going twice what the indicator shows.
later,
Gums sends ...
edit: Yep, the "hudrecord" stops when we're in the Nord. Just tested it.
P.S. My data reduction war story upon request, heh heh.
__________________ Gums
***305th BG(H)***
God in your guts, good men at your back, wings that stay on- and Tally Ho!
This post has been edited 1 time(s), it was last edited by Gums on 02-11-2010 at 18:56.
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02-11-2010 18:34 |
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Gums
Forum God
 
Registration Date: 03-25-2002
Posts: 2824
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Salute!
If you all wanna know what my experience is in these things, here' a short vitae.
I was a systems engineer for a small company that had 100% government contracts to integrate weapons on planes. New missiles on old planes, old missiles on new planes, new missiles on new planes, and the beat goes on. We also designed stores management systems to control the weapons, and I was primarily the cockpit controls and displays dude. This was the result of my experience in the SLUF and Viper.
In early 90's we got to help on the ATARS - Advanced Tactical Recce System. It was to replace the older film systems with digital imagery. I wound up the lead engineer for the data reduction facility. So I had to develop and implement the specification for the place.
Our data recorders were analog and digital. We recorded everything on huge tapes - 14" or so AMPEX doofers, 7 channels +/-. Digital stuff on one channel and analog stuff on the other channels. So another engineer worked out how to digitize the analog stuff like vibration, accel, pressure, and temperature. Multiplexed FM stuff, so we could capture a few dozen presure sensors and accelerometers and ...... The digital was from a MIL-STD-1553B bus recorder.
So I had to provide the sfwe geeks all the conversions and scaling and .... for the variety of digital "words" we recorded. Some systems had basic 1553 words ( 16 data bits, plus 3 synch and 1 parity). Others from older components had 10 bit words that we had to "pad" to get everything into 16 bit format to make things easier.
So the damned thing worked and we could crank out "quick look" data for the engineers and managers real fast after the planes landed from a test run.
I got very good at grabbing parameters of interest and plotting them for the slide show presentations the next day.
Being a pilot, I took special interest in how well the test pilot flew the profile for each test. I would post his altitude, speed and other stuff to show folks how well USAF met the profile requirements. One of our pilots is now the chief astronaut at NASA - Steve Lindsey. So I know more about him than you do, heh heh.
So that's it, and why I value no sierra data records versus war stories about how the plane flies.
Gums sends....
__________________ Gums
***305th BG(H)***
God in your guts, good men at your back, wings that stay on- and Tally Ho!
This post has been edited 1 time(s), it was last edited by Gums on 02-12-2010 at 11:29.
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02-12-2010 11:25 |
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Gums
Forum God
 
Registration Date: 03-25-2002
Posts: 2824
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Salute!
Ok, Goebel, another 15 "attaboys".
Tried some different data entities and they worked, except for the "AOA" doofer.
I'll try to figure out what the hell that is, but I changed the recorded data entities and the" power" data is invaluable.
The other thing that is neat is that the recorder keeps logging when in the Nord, and HUDRECORD does not.
"mph" is IAS, and somewhere in the code is the actual velocity vector, which is related to TAS. I was able to get the vector using pythagorus' thingie and xpos/ypos, and it was spot on. That was horizontal, and I'll try "Ypos" or just use "alt" and see what I get.
Again, thanks.
Gums...
__________________ Gums
***305th BG(H)***
God in your guts, good men at your back, wings that stay on- and Tally Ho!
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02-12-2010 15:34 |
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Gums
Forum God
 
Registration Date: 03-25-2002
Posts: 2824
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| Need support decoding the FltLogger data |
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Salute!
Have not checked all data entities, as I have to edit the script each time.
The pitch, roll, yaw stuff must be coded, as it doesn't look like angles to me- radians or degrees. Could be rates.
The Gee seems to be "times ten", but still not as good as "hudrecord".
The "stall" doofer could be a switch setting by the user on the main page option menu. i.e. a "discrete". Will check that one by changing my entry settings.
About to check all the trim and surface postions. Still need another test dude.
I shall continue to bug iEN to get the "power" on the "hudrecord" script, as that really helps with flight testing.
The "GS" reading on "hudrecord" is TAS, not ground speed. Screw the groundspeed, as it's too easy to do on the spreadsheet, courtesy of Mr Pythagorus. It's not much help, anyway.
later,
Gums...
__________________ Gums
***305th BG(H)***
God in your guts, good men at your back, wings that stay on- and Tally Ho!
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02-13-2010 17:37 |
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