HSI Questions
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Hi Kaiza
Thanks for a nice practical explanation -
buying a whiz-wheel is more fun and lets you do the same thing, plus with a handy circular slide rule : )
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To all - I AM using the NAV setting on the HSI, it appears I need to point that out better, my appologies. I’ve got a E6-B8, which only does wind crossing calc.s to 270 knots. Here’s what I determined last night, before I nodded off. For my indicated speed I used what the GUI recommended speed was, since I couldn’t remember. So IAS was 225 knots. My altitude was 15,000 feet. It should have been 30C, since I don’t know if Falcon changes temps and at what amount for height above surface, on a sunny day. The wind speed and direction were 4 knots @ 319. Once I started using my slider I determined my true airspeed to be 308 knots, ground speed to be 304 knots. How valid that is I’m not sure, since I was near lala land. And I’m not sure how important this is in Falcon, but my density alt. should have been 20k’. At present I haven’t determined how far off track I got there, my head had been bugging me all afternoon (weather related light sensitivity - cloudy then BRIGHT cause me light headaches) so I stopped there. Now I’m back to my normal state and will plug away some more.
@ Frederf - I’m jealous now. Yes, WCA is correct
@ caper - I am using the HSI in nav mode, that’s how I get the cdi to move for each steerpoint. Used like this when I set the course knob to the heading given for the steerpoint in the GUI flight brief the CDI pointer will be in the same direction as the HSD connecter lines, and the deviator will move relative to which side my bird is of that line/course, and roughly the same amount (when HSD is in the 8nm scale).
@ Kaiza - Thats one vote for 5* per dot, and the original vote for 2.5* per dot. I’d love one of the DEVs to chime in and set the record straight for BMS. Without that information the CDI will only be useful to me for intercepting nav. points, and not for determining how far off I really am. Your explenation for wind correction sounds right, it’s just been so long since I’ve done it …
@ Blu3wolf - Whiz wheel? That’s what I say when I mean a cutoff wheel! Can’t fit one in the A/C, and it does very bad things to body parts while spinning. NowIcan’tusespacebecauseIcutoffmythumbswiththewhizwheel!!! Wink wink.
-Babite
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To all - I AM using the NAV setting on the HSI, it appears I need to point that out better, my appologies. I’ve got a E6-B8, which only does wind crossing calc.s to 270 knots. Here’s what I determined last night, before I nodded off. For my indicated speed I used what the GUI recommended speed was, since I couldn’t remember. So IAS was 225 knots. My altitude was 15,000 feet. It should have been 30C, since I don’t know if Falcon changes temps and at what amount for height above surface, on a sunny day. The wind speed and direction were 4 knots @ 319. Once I started using my slider I determined my true airspeed to be 308 knots, ground speed to be 304 knots. How valid that is I’m not sure, since I was near lala land. And I’m not sure how important this is in Falcon, but my density alt. should have been 20k’. At present I haven’t determined how far off track I got there, my head had been bugging me all afternoon (weather related light sensitivity - cloudy then BRIGHT cause me light headaches) so I stopped there. Now I’m back to my normal state and will plug away some more.
@ Frederf - I’m jealous now. Yes, WCA is correct
@ caper - I am using the HSI in nav mode, that’s how I get the cdi to move for each steerpoint. Used like this when I set the course knob to the heading given for the steerpoint in the GUI flight brief the CDI pointer will be in the same direction as the HSD connecter lines, and the deviator will move relative to which side my bird is of that line/course, and roughly the same amount (when HSD is in the 8nm scale).
@ Kaiza - Thats one vote for 5* per dot, and the original vote for 2.5* per dot. I’d love one of the DEVs to chime in and set the record straight for BMS. Without that information the CDI will only be useful to me for intercepting nav. points, and not for determining how far off I really am. Your explenation for wind correction sounds right, it’s just been so long since I’ve done it …
@ Blu3wolf - Whiz wheel? That’s what I say when I mean a cutoff wheel! Can’t fit one in the A/C, and it does very bad things to body parts while spinning. NowIcan’tusespacebecauseIcutoffmythumbswiththewhizwheel!!! Wink wink.
-Babite
you can calculate crosswinds at ANY speed using an E-6B, you just need to apply a sensible multiplier… for instance, if you multiply all the values by 10, or by 2…
for the same stunt to work for the opposite side, on the circ slide rule side, you need to multiply all values by 10 (or some power of 10, ie 10^2, 10^-1…)
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So I’ve re-flown my TE to get a look at how the #s change in relation to eachother. When I check my airspeed indicator, I show ~ 228knots. At this point I’m pausing the sim to see what it claims to have for a true speed and a ground speed, VIA the hud. I have been flying by instruments, remember. So when I flick the speed switch to TAS I’m shown 287 knots, and when I flick it to GS I see 283 knots. Now remember this is on a 30C SUNNY DAY. Now I set the pressure altitude already to 29.92, since my height is supposed to be at 15.0M, or FL15. As I punch the needed numbers into my E6-B8 (yes, it’s not the fanciest, yet…) I need my pressure altitude, which is 15020, rounding down to 15000, set to the air temp of 30C. Then I read from my IAS on the inner circle to get my TAS from the outer circle. So 228 on the inside gives 287 TRUE for this height and temp. So the TEMPERATURE of the air doesn’t change with altitude in BMS then, in my case here. Anybody else wish to confirm?
-Babite -
@ Kaiza - Thats one vote for 5* per dot, and the original vote for 2.5* per dot. I’d love one of the DEVs to chime in and set the record straight for BMS. Without that information the CDI will only be useful to me for intercepting nav. points, and not for determining how far off I really am. Your explenation for wind correction sounds right, it’s just been so long since I’ve done it …
You dont need a dev to answer that one, you can work it out in 5 secs in the pit. Just dial the course bar around till it is 1 dot off and see the difference between the course bar and the needle.
I use the modified CCIP pit which has a modified HSI, so I can’t confirm. When I did it, 5 degrees was just over one dot, so a dot was about ~4 degrees, maybe just a bit over. This is probably just an error with the HSI scaling of my modified pit though.
Remember though, the scale will change depending what mode you are in, so this is only valid for TACAN.
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Or you could just go to page 3-9 of the manual that states 5 degrees for tacan/nav and 2.5 for ILS…
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Yes, but what about NAV? NAV defaults to 2 dots = 4 NM but the airplane should have an option (I’ll have to check BMS) for 2 dots = 3 degrees for most waypoint types (not STP 21-30).
Babite, if the temperature doesn’t change with altitude in BMS that could be a very significant finding and would lead to some rather odd results.
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Just reporting the information I have. If anyone else has either the know how or tools to run their own test on this and would like to report their own findings, I’m all ears. To an extent it should be warmer the higher up you go, since hot air rises and cold air falls, but after a certain point you would start to cool down the higher you went. Funny contradiction there.
Kaiza - Thanks for catching that, I new I must have missed something. That’s in the old brick manual, b.t.w. (glad the old resources still exhist). My question there still stands though. Did that change for BMS or does the old ruling still apply? Although your HSI is so much easier to read than stock … much clearer, but how are you changing it? I don’t see the HDG or CRS knobs, are they still in the same place painted black or do you manipulate them elsewhere?
Frederf - 2 dots = 4 nm? at what distance from station/steerpoint? As Kaiza states from the good old brick 5* is for TACAN and NAV, while 2.5* is for ILS TACAN & ILS NAV. 3* isn’t mentioned anywher, I’m guessing you’re rounding? Still would like to know how BMS handled this - my math skills in the pit are S…L…O…W. I never was superfast with big numbers, without a calculator doing trig problems would be hours, looking up coefs. for angles and x^2 roots & such, might be days. And I still wouldn’t have an exact fix on my location, which keeps changing unless I’m on the ground, and even then it changes. Per the temp., what issues did you have in mind? I.e. Worse engine performance due to hoter high alt. air? Funny handling characteristics?
To update the vote, since I misunderstood Kaiza the first time - 2 votes for how the brick states it, possibly 3 depending on Frederfs’ response.
Maybe I should have titled the thread “AIRMASS CHARACTERISTICS, MATH, AND BMS” due to the way things are playing out at the moment?
-Babite -
Hot air does rise but it also expands. The hotter the more buoyant and tends to find a place at low pressures which causes it to spread out and have less energy per volume and be colder. Higher, lower pressure, lower temperature is the overriding trend. Initial temperature more determines the destination than what to expect when it arrives. Depending on how things are calculated things could be very weird or already accounted for, but yeah, low air density, poor engine performance, that sort of thing.
2dots/4nm at all distances and that’s straight out of the book. Cross range error per dot would be constant no matter if the STPT was 10nm away or 1000nm. The computer takes your destination and desired course and determines what path (great circle no less I think) travels through that destination on that course. This imaginary pencil line on the map is compared against your current position and a measurement is taken how far you are from that line. The distance is displayed by deflecting the CDI.
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You oughtta figure for a 2 degree drop in temperature per thousand feet of altitude gained.
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You don’t need to figure out Wind Correction angle with an HSI. Set the OBS and keep the needle centered you have corrected for the wind. In real life you would slave it to the GPS or the INS. I guess it depends on what you’re trying to figure out.
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To ALL - As I read this post I see that it may come across as a HOSTILE ATTACK. That is not my intent. I’m trying to bridge the gap in my mind between REALITY and the BMS world. What I’m noticing is REALITY isn’t always happening in BMS. Test data #s from others would be a real help if you can provide it.
Frederf - The “brick” manual states on pp. 3-8, “Each dot represents either 5* or 2.5*, depending on which mode the HSI is in. When the needle is fully deflected, the aircraft is 10* or geater from the selected course.” Which book are you refering to, then? As I’ve stated before I haven’t seen ANY information in the newer documents/manuals on changes to the HSI. PLEASE LIST supporting reference.
Blu3wolf - That’s not what my math has shown. I wouldn’t be suprised to find that I did something wrong, but my answers line up with what is shown on the HUD depending on speed mode for 30C. I ASSUME that the 30C is the ground level temp., since I’m not positive on the weather implementation in BMS. Having said that, the data I have supports that the temperature has NOT changed from ground level up to FL15. I reiterate that I’m in STOCK KOREA, BMS v4.32 + u7. If you have the #'s to back this up for BMS I’m all ears.
Capt.Stubing - by OBS I assume you mean On Board Sensor. If that were doable in BMS things might be easier. But you’d still be off-heading to keep the needle centered. So you’d still want to know what heading would be the correction for wind to stay on line.
-Babite
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Not true… OBS is the Omni bearing selector which moves the little green arrow and sets the course you want to track on. There is a knob for it on the HSI. If you’re tracking a course of a radial of a TACAN and center the needle regardless of heading you will be on course with an automatic wind correction. That is why there is a needle. The HSI can be slaved to GPS and INS as other sources of navigation though I don’t know if BMS supports this function. Needle sensitivity is relative to what you’re tracking. An ILS is 4X as sensitive than a TACAN or VOR. Quite simply a TACAN is a VOR with DME or distance measuring equipment. An ILS is a different system all together. Instrument Landing Systems provide a Localizer course and a Glide Slope hence the two needles depicted in your HUD and on the HSI. What exactly are you trying to figure out in terms of Temperature?
This will help you understand.
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Capt.Stubing - Ahh, difference of term. Thanks for clarifying. Yes, if you kept the deflectable part in line with the course arrow lines you would have compensated for the wind problem. 100% agree. That is done much easier and with much more consistancy IF you know the propper correction to apply. I’m not trying to critisize, although when I read it back I can see it that way. Let me try an analogy, to get on the same wavelength with you. You have a multiple choice test, answers being either true or false. Right off the bat if you don’t study for the test you have a 50/50 shot at being right on each question. But if you studied before the test you have a better than 50/50 chance on each question of being right, as long as you studdied the correct material beforehand. I.E. studying philosophy might be a bad choise for a math test. (Unless the philosophy was to cheat and you had the answer sheet!)
Getting back on track, if you know the wind correction for the situation you can keep the cdi centered when you apply it.
As to temp - temp alters the air density. Higher temp the air will be less dense, which would degrade normal flight - your attitude would be higher on a hotter day than a colder one to maintain the same altitude, wouldn’t it? Engine performance would be lower on a hotter day than a colder day, less burnable molecules of oxygen and nitrogen that like combustion, right? So if it’s hotter higher up then your engine wouldn’t be putting out as much thrust as it could, right? Maybe at 10-20 fps that isn’t really much of an issue, but still.
I’ll peak at the video link you gave when I’m away from my slow connection.
-Babite -
The F4.0 manual may be correct to the simulator. I don’t know what specific block the original F4.0 software was simulating, how its HSI worked, and if anyone bothered or was able to change its behavior as time went on.
PX III Except for UTM’s and markpoints (steerpoints
2130), each steerpoint can have an associated CDI
deflection. the selected deflection scales the HSI for
course deviation as represented by a twodot
deflection of the CDI. From the STPT L/L or DEST
DIR pages, DCS SEQ can be used to display a DED
page to program these functions. Two options for CDI
lateral deflection are available: 4 NMI (default) or 3
DEG. The 3degree selection will be displayed in the
lower left corner of the HUD as ANG. UTM’s and
markpoints always use 4 nm scaling.The PX III aircraft are 60 “Peace Xenia III” BLK 52 C and D models delivered to Greece in 2002-2004. The quote is from the GR1-F16CJ-1 (2003). I would expect 2003-era USAF F-16s to be the same. This is normal for airplanes with INS to have CDI angular deflection scales for radio navaids since they must but have options for the INS deflection scales. The (DCS) A-10C has four options for the INS scale (enroute, terminal, high acc, approach) for example of which one is angular and the rest are absolute crossrange.
Be aware that in reality ILS CDI deflection is a bit of a crap shoot what angular error is associated with what dot position. The actual angular position error reported by the same CDI-deflecting signal varies from installation to installation as the ILS fans vary in width. TACAN/VOR type navaids are trustworthy when not broken as 360 degrees worth of signal has to cover 360 degrees of pattern and there’s no room to get creative.
OBS is “omni bearing selector” a rather charming term that’s synonymous with the course knob.
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There are a dozen ways to find the WCH (I should have used that term instead of WCA) in the F-16. Guess and check keeping to an HSI picture, rules of thumb, E6-B, eyeballing the crab angle by FPM displacement, etc. and etc. I like the pencil and paper ways to do it more because it makes an enlightening homework problem that fosters understanding rather than being the most operationally expedient.
Good luck testing temperature in BMS. I’m curious the results of your experiement.
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I ran a test today of altitude/airspeed/temperature, using TE mission 01 for stock KOREA. The weather changed on me while performing this test, so some fields will start out blank since I didn’t realise they would apply at first. And I noticed that EVEN THOUGH I had the sim PAUSED while trying to jot down data the wind kept changing. As you read through the sheet you’ll notice that at first my IAS varries, then stabilses. This is due to me not getting a consistant speed before checking things at first. I eventually settle down to 250 Knots. And the IAS I was pulling from the indicator, then comparing it to the HUD as seen with HUDCAS. Those two fields should be the same all the way through since the HUD repeats what the airspeed indicator says but in DIGITAL format. I’m not quite as accurate at reading the needle as the system is, that’s the reason for variation there. And when I transitioned from FL14 to local pressure altitude you’ll see the values first for 2992 mb and then for the local pressure 14000 Ft. The pressure kept dropping when I hit 11k’, I couldn’t keep up with it at first. So 3 entries for that for that reason.
If you want to try to compare my results with a test of your own, my Weather Control Settings are currently:
[Weather] Model - Probabilistic, Current Weather - Sunny, Min Change Interval - 600 sec, Max Change Interval - 680 sec, Probability - Sunny - 25%, Fair - 25%, Poor - 25%, Inclement - 25%[Atmosphere] Temps (*C) Night - Sunny/Fair/Poor/Inclement 12/12/10/9, Temps (*C) Dawn - 18/18/15/14, Day - 30/28/25/22
Pressure (mb) Night - 1034/1007/989/978, Dawn - 1036/1009/991/980, Day - 1040/1013/995/994[Turbulence] {Cumulus} ROTxWindSpeed - 5 Kt, ROTxRotSpeed - 45 DPS, RyWS - 7 kt, RyRS - 134 DPS RzWS - 3 Kt, RzRS - 240 DPS
{Troposphere} RxWS - 3 Kt, RxRS - 45 DPS, RyWS - 4 Kt, RyRS - 134 DPS, RzWS - 2 Kt, RzRS - 240 DPS
{Low} Max occurence time - 60 sec, Max duration time - 20 sec,
(Mech) Layer - 500 Ft, Wind 30 Kt, RxWS - 4 Kt, RxRS - 45 DPS, RyWS - 5 Kt, RyRS - 134 DPS, RzWS - 2 Kt, RzRS - 240 DPS
(Heat) Layer - 1500 Ft, Water, RxWS - 1 Kt, RxRS - 45 DPS, RyWS - 3 Kt, RyRS - 193 DPS, RzWS - 3 Kt, RzRS - 240 DPS
Cities, RxWS - 3 Kt, RxRS - 45 DPS, RyWS - 4 Kt, RyRS - 193 DPS, RzWS - 4 Kt, RzRS - 240 DPS
Other, RxWS - 1 Kt, RxRS - 45 DPS, RyWS - 1 Kt, RyRS - 193 DPS, RzWS - 0 Kt, RzRS - 240 DPS
[Wind] Heading - Probabilistic, Max speed (Kt) Night - 0/5/10/15, Dawn - 2/10/15/20, Day - 5/15/20/25, Wind Burst: Interval (sec) - 30/20/15/5, Duration (sec) - 5/10/10/6, Speed (Kt) - 2/9/13/16, Direction (*) - 10/20/30/30
[Fog] Distance Start (Ft) - 8000/4000/0/0, End (Ft) - 200000/160000/70000/25000I’ve tried to attach a spreadsheet in PDF form, posting attachments hasn’t worked too well for me lately.
-Babite
Update: Second test results posted.
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Could you graph the temperature vs altitude and apply a best fit line (ax+b) in excel?
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This is the best I can get at the moment. I haven’t played with excel & charts in years.
-Babite -
That’s not bad, good trend. 50F (I hope that’s F) over 20,000’ is 2.5F / kft which is bounded nicely by the dry adiabatic lapse rate of ~3F/kft (real environment should be no more than dry adiabatic).