HSI Questions
-
Frederf - Where are you getting the 50F over 20000’? All I have depicted in that graph is feet and temperature in *Cel. I took those #s from the first spreadsheet, so you should be able to relate ~ where each point is. Can you elaborate more on your comment?
Kaiza - No, it wasn’t a cloud. Somehow I rolled into a thunderstorm. I think the storm height was around 12,000 feet. When I was at 2k feet I could see lots of precip. and occasional lightning. Moral of the story is PAUSE doesn’t PAUSE everything, just the fighting and the clock. The weather doesn’t follow those rules.
-Babite -
Forget what I said. I found an article titled ‘Mother Nature’s lapse rate limits" which kicks my brain into better thinking. I saw temp drop from +20 at 0’ to -30 at 20,000’ and thought this can’t be measured in C since DALR should be 2C/1000’ or less (It isn’t). Of course it’s C, F is on the order 5.5F/1000’ (what was I thinking). In any case the DALR is 3C/1000’ and I wouldn’t expect environmental lapse rates in excessive of that. The 50C delta divided by 20,000’ is nicely bounded by the 2C/1000’ ISA rule and the 3C/1000’ DALR expected maximum at 2.5C/1000’.
Your results paint a picture of BMS having a temperature-altitude profile true to real life. I would even go so far as to guess the type of weather present, rather dry and clear. I wonder if a rainy wet day would show the lapse rate below ISA or lower than 2.5C/1000’.
-
Your results paint a picture of BMS having a temperature-altitude profile true to real life. I would even go so far as to guess the type of weather present, rather dry and clear. I wonder if a rainy wet day would show the lapse rate below ISA or lower than 2.5C/1000’.
Perhaps the overall average ELR is similar to a typical lapse rate, however I personally wouldn’t have considered portions of this a typical temperature altitude profile. A ~12deg increase in temperature in a cliimb of 3000’ is pretty extreme, especially following an ELR of what looks to be close to 16deg/1000’ at low level. I have never seen a real world tephigram that resembles anything like this before, but I am no means a met expert. At any rate the reason I thought there would be cloud was because of that extremely unstable layer at low level. Its impossible to tell without a dew point of course but there would be some serious lifting going on. If the CBs were stong enough to push through that stable layer at 2K, then they would continue through the unstable layers fairly high I would imagine making some nice Tcu’s.
That 6-10K band might give you some nice glaze icing as well.
-
I was talking about the fitted trendline, not the graph points specifically. I’m only so confident on the accuracy of the temperature derived from the actual data gathered. My starting point is assuming BMS is overly simple in modeling weather and the fluctuations in the results were due to the difficult way how they were calculated and not how the temperature actually evolved over altitude until shown otherwise.
-
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.
That is true but winds aloft in real life are forecasted at your particular altitude and in my experience that’s great for planning but rarely does it work out that way. Hence all you have to do is center the needle when flying and if you have a wind you will turn to a heading that will hold the needled in the center. Again WCA is great for planning purposes but you will update all that stuff in the cockpit when actually get there.
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.
Yes air temp is great for helping you calculate airspeed and performance. Piston engines are very sensitive to temps. Jets are too but not as much given where they operate. In the end all you’re trying to figure out is ETE fuel burn which is based on Ground Speed which is effected by the wind. Great stuff for planning purposes. When planning the flight we look at all of those factors and pick the best Altitudes etc. to give us the performance we want.
I’ll peak at the video link you gave when I’m away from my slow connection.
-Babite -
Per the graph data - I should mention that I started at 20k’ and then stepped down. I was having a rough time with “excel” at the time I made that graph, the way it’s shown is just how I got the #'s to behave. Look at the sheet I made to get a better idea of what was going on. Also bear in mind that I had to pause the sim to get all the data recorded, which could take anywhere from 20 seconds to a minute, and then add in the fact that I would try to get =/- 5 Ft to the altitude, and then have to fight the speed back to 250 Kt. Lots of time passed from 1 height to the next for those reasons. I’ve got another one ready to go, just have to send it from an alternate connect point.
-Babite -
You said the weather was changing when you recorded these? Maybe the problem is the change, not your recording. Did you have random weather on? If yes, not good for the tests.
If not, then forget what I said. -
TKorho - It started out sunny for the first two tests. Then things got worse.
For my third test - performed 18/4/2014 - I ran from a different TE using another aircraft. The first test was a block 52 C I think, the second test was forced to be a D block 52, and THIS THIRD was performed using a block 50 C. If you can read the chart you’ll see I forced the weather to not be able to change for some time. This allowed me to hit pause and not un-pause back into some funny change. The forum won’t let me upload a .xls file. Trying PDF.
-Babite
-
The included training TEs (some) are notoriously weird in terms of how rapid the weather changes are scheduled in them. The safest values would come from a bone-blank TE. What would be nice is some way to extract temperature directly or at least the TAS/Mach values v altitude (that’s what was used, right?) data directly, say via Tacview.
-
If I had the resources I’d do that. My current setup is on the slower side. My best flights see 27/28 fps. With bloom settings turned way down. So at present I think that’s a test I just can’t run. Though it would be simpler.
-Babite -
Tacview is pretty light. I could record a .vhs file in a Falcon TE that is probably 50MB/hour at most. Then collecting the data from the .vhs file in tacview might be easier. I dunno, haven’t tried it myself.
-
Anyone have any tips for getting the HSI needle to go from 5* per click to 1* per click? The zoom in millions of steps per try is getting old, and what I can find per the key file is just 5 degrees/button. Ideas? Or does anyone know the correct zoom level to go from 5* to 1*?
-Babite -
Stand down - found my own answer. Didn’t remember seeing it in the extra keyfiles, but the first one by Kolbe had it. For reference:
SimHsiCrsIncBy1 -1 0 0X33 2 0 0 1 “MAIN: HSI CRS Knob - Increase (1°)”
SimHsiCrsDecBy1 -1 0 0X33 4 0 0 1 “MAIN: HSI CRS Knob - Decrease (1°)”
-Babite