GPS TRK in Gustav Winds

[Tom Goodrick]

Flying in Gustav's winds taught me something. All these years I have been flying with the GPS map in my panels I missed the fact that the number at the top of the map is TRK for ground track! It took the strong wind field around southern Louisiana geneerated by Hurricane Gustav to teach me this. I got RW at 9:30 this morning as the eye of Gustav was on the coast just south of Houma, LA. I took off in the Merlin III and flew south at 9,000 ft in HDG mode on the autopilot. I had 180 set in the HDG window. But the number on top of the GPS map was indicating 190 degrees. The winds at 9,000 ft were 52 kts from 86 degrees. I thought something was wrong with the airplane. I switched to the Beech 350 in which I have a lot of confidence, having flown it for over 100 hours all over the world. It showed the same heading. Then I hitched up my bifocals and leaned closer. The letters TRK began to mean something. I turned around to fly HDG of 360 and saw 349. OK, adjusting HDG to 011 gave me exactly 360 for my ground track. It made sense. I thought TRK only had significance when the autopilot was in NAV mode.

Gustav taught me something new. We can use TRK in HDG mode to compensate for wind to fly a desired track.

Now to fly the eye and then land at Houma.

[flaminghotsauce]

I tried d/l ing real weather last night when the hurricane was just off the coast. I got 44 degrees, light winds, and a few clouds. ?!?

I'll have to try again here in a bit, but it's a Cat 1 now.

[Tom Goodrick]

I could send you a zip of the weather file from this morning at 9:30 if you wish. I intend to get another one now that it is entirely over land. It is still a Cat 1.

[flaminghotsauce]

Yes, do send them to me. I tried it again tonight and I got 54 degrees, some stratus at 2000' and 26 mph winds. What temps did yours show? I thought it very strange it was so cool.

[hanspetter]

Please send me some hurricane weather too!

[Tom Goodrick]

Flaming with regard to the temperatures you saw, you might be reading the temp under the wrong conditions. If you read the temp when the sim is paused, you will not get a valid reading. The tempreverts to the Standard Day temp for whatever altitude you have. You must be active in the sim to get a good reading. But even then you will not get a good reading on the Bell206 thermometer if you are moving. If flying above 1000 ft, expect a significant reduction in the ambient temperature.It will be low because it shows an extreme amount of cooling in the moving air if you are flying. I made a thermometer for use in flight that does not show cooling effects but it reads in degrees C for use with turboprops and jets.

To determine the temperature at a distant airport, go there and park. Then unpause the sim and read the temp in degrees F on the Bell206 thermometer.

If flying at some significant altitude, the temp would normally be reduced substantially from that at the surface. here are some standard day temps:

ALT__TEMP F
0_______59.0
2000____51.9
4000____44.7
6000____30.5
10,000___23.3
15,000___5.5
20,000___-12.3

Reduce these low temps by the speed effect on the Bell206 thermometer and you really have cool temps, even in summer. By the way unless you are using a wet-bulb thermometer, the cooling effect on the Bell thermometer is totally bogus.

[hanspetter]

Regarding temperatures I got 33 on the ground! This might make sense if it's Celsius while it's next to freezing conditions if it's Fahrenheit.

I found Gustav to be quite manageable. Previously, any "big" weather has kicked my planes around violently to the point of making them unflyable. I assume my improved hardware to be part of the explanation. Well, how could that be? Quite simple, previously the graphics didn't keep up with the calculations. I got stuttering and may have missed out on transitions between changes in attitude. Thus, I saw the planes zigzagging between extremes when they were really supposed to be swaying. I'm likely to have overcompensated, always staying behind the action and giving delayed inputs that exacerbated the situation. Another thing is that better 3D graphics produce softer overcasts. The cloud cover used to be a white blanket that blocked the terrain completely. Now I see a seamless transition between a complete white-out and hazy conditions, meaning that most of the time I can see what I'm doing once I get close to the ground.

[hanspetter]

Sept 4, 2008 23:26:36 GMT -5 Tom Goodrick said:

It will be low because it shows an extreme amount of cooling in the moving air if you are flying.

I don't understand this part. It seems to imply wind chill factor ("real feel") but that's of no consequence unless you happen to be an object that tries to retain a different temperature. A piece of aluminum will be at ambient temperature whether the air is stagnant or moving. The only difference is that when it starts out at a different temperature it will reach the new ambient temperature faster with a high wind chill factor.

There's heat of compression and heat loss due to decompression. A thermometer that's exposed to the ram pressure of an aircraft should read a bit higher than the real ambient temperature and vice versa. There's also the heat of friction that creates extreme skin temperatures in supersonic aircraft.

[Tom Goodrick]

All hurricane files are "manageable" until you try to land at some of the airports. Try making a landing at Jackson, Mississippi, KJAN, just a 100 nm or so north of Baton Rouge. I tried it in my Learjet 35 and decided I didn't want to land there. I aborted the approach and flew on to KHSV after my tour of the area near Gustav. The interesting thing is how the winds extend so far from the eye which is on the coast in this file. Flying into and out of Houma should also be interesting but that is near the eye.

I find strong turbulence knocks my plane around just as it should in real life. You can get jerked out of your seat easily if not belted in. That's the kind of turbulence I found on the approach to KJAN. You don't want to get low and slow in winds like that. But you can fly fine at altitude.

Regarding temperature, I did not say there was any validity to the performance of the Bell temp gauge. It is clearly wrong. M$ screwed up. It is handy to read the temp in F when sitting still on the ground. It does a good job of that. But get up and moving and it shows bad info.

That gauge is the one named Bell_206B.Temperature.gau and the one that should be used in all cases is named Digital!AMP_TEMP_C.xml which I wrote. It reads a temperature inthe sim that is not changed by the speed of the aircraft. "Wind chill" does not occur in inanimate objects. You are right that there is a thermal warming effect on the skin of any aircraft moving very fast - at least Mach 2.5. We don't see that effect in FS9. But the Bell thermometer can easily be off by 10 degrees at 150 KIAS.

You didn't say what gauge was showing you 33 degrees on the ground. If the wind was strong and you were using the Bell gauge, it would indicate low. It should be clear what units are used in any case as either a C or an F appears on the gauge.

I reported on this about a year ago and developed my AMB_TEMP gauge so that I could read the ambient temperature during the flight of jets where that temp has an effect on performance.

I recorded a weather file during hanna as well - when the eye had passed inland over North Carolina. It takes a while to find the high winds in the storm area of a tropical storm or hurricane because that area has a diameter of about 500 nm. You mainly find trouble at some airports when you try to taxi and takeoff or land. I don't think your equipment has any significant effect. Of course I seldom fly on manual except for landing and taking off.

[hanspetter]

The temperature that I referred to came from the ATC. There's a text strip running across the top of the screen and a voice message being repeated all the time in the vicinity of Houma. I landed at Houma, rwy 11 since that was what the message advised. I chose a higher landing speed than normal (about 100 knots) and didn't manage to get perfectly aligned but the landing was fair. I'm sure other locations would be impossible under these conditions.

[Tom Goodrick]

That is 33 Celsius. ATC always gives the temp in Celsius. This is southern Louisiana in early September. The Baron shows 91 F on the runway with 5 kt wind.