Jump to content

Sign in to follow this  
Guest depot_haldol

High Altitude Airports

Recommended Posts

Guest depot_haldol

Are there any known issues with high altitude airports picking up the winds aloft and using them as surface winds? I flew out of Aspen, Colorado, last night and the sirface winds were about 10 kts. But on the takeoff roll I suddenly experienced a sustained 55 kt crosswind, which blew me off the runway before I could get airborne. Any ideas? Thanks.

Share this post


Link to post
Share on other sites
Guest depot_haldol

Hi, I was with FS9, not FSX. Thanks for your speedy reply. I don't know if this was an ActiveSky problem or not. I was using ActiveSky and Radar Contact. Radar Contact reported the following winds:...WIND 040 AT 12...And that agreed with the weather packet that I printed from ActiveSky. So there was agreement between the two. The problem was that the actual FS9 winds were over 50 kts, and a direct crosswind at that. The field elevation was about 8400 feet, so I thought maybe there was confusion with winds aloft. I don't have any other explanation than to say it was "one of those things." I tried unsuccessfully to repeat it tonight. I'll report back if it happens again.For the record, ActiveSky is a great product and I'm a very happy user.---Will

Share this post


Link to post
Share on other sites

Hi,Do you have the exact zulu time when this happend?I'd like to try this myself.@JimI have seen this happen before a couple of times. Though it was a long time ago and it might have been fixed.What happen is that the winds aloft are high, but the metar report calm on ground. So when you get off the ground and up a few hundred feet the winds aloft take over and cause a big change in winds.Never seen it happen instantly as you leave the ground though...Same thing with wind direction. It can be 180 degrees oposite of the airport wind just above the ground layer. Dont know if this happens in the real world as I am no pilot.

Share this post


Link to post
Share on other sites
Guest depot_haldol

Yes, as a matter of fact I do. First of all, here are the relevant METAR and TAF, printed before flight, probably close to 2345Z:KASE 242253Z 04012G17KT 10SM FEW070 BKN085 07/02 A3015 RMK A02 SLP148 T00720017KASE 242337Z 250024 35010G18KT P6SM VCSH FEW060 BKN080 FM0200 20005KT P6SM VCSH FEW060 BKN080 FM0600 21006KT P6SM SCT090 FM1400 VRB04KT P6SM SKC FM1900 34007KT P6SM SKCFL030: 268/07 (19.10) FL060: 268/07 (13.00) FL090: 266/08 (9.20)FL120: 242/17 (-5.70) FL180: 257/56 (-14.90) FL240: 260/83 (-23.20)FL300: 257/91 (-40.70) FL340: 260/89 (-48.30) FL390: 260/70 (-51.40)Then I listened to the ATIS at KASE, probably at 0020Z:KASE 36010KT 26SM BKN850 07/03 A3019 RWY33This seems consistent with a new observation having replacing the one in the METAR (from 2253Z). The ATIS is in line with the forecast.I taxied out to RWY33 at 0046Z. Takeoff roll started at 0052Z. I don't remember what tower said the winds were as the takeoff roll started, but I remember that it wasn't remarkable. My first indication that anything was wrong was a massive pull to the LEFT, so much so that despite full rudder the plane wouldn't stay on the runway. I had been messing with joystick axis controls in FS so my first thought was that a brake was dragging. When I saw that a catastrope was about to happen, I hit SLEW and moved the plane back to the beginning of the runway and put it back on the center line. I tried again to continue the takeoff, now paying special attention to the brakes, which actually seemed to be working perfectly. Next, I thought I may he having a rudder "hardover" or a jammed control, so I looked at both the control surfaces and the cockpit indications. Everything was operating normally. At this point I was very confused about what might be going wrong.At any rate, I finally had ehough airspeed to rotate, and when I did the aircraft instantly began to drift massively to the RIGHT, so much that by the time I was about one runway length ahead of the departure end of RWY 33, I was also about half a mile to the right. I've never experienced drift like that before. I glanced at the ESHI wind indication as soon as I recognized the drift, and it was showing 55KT left crosswind, immediately after rotation. The crosswind rapidly build to 85KT in the initial 2000 feet of the climb.The remainder of the flight, including landing in Oslo at 0940Z, went uneventfully. There were no problems with brakes or control surfaces, and the winds at Oslo were mild, and just as forecast.So in the interim I reflew this a few times and I can't duplicate the problem.Trial #1: KASE, everything the same as on the original flight, axcept no ActiveSky and no Radar Contact. Winds forced calm. Normal takeoff.Trial #2: KASE, same as above, except surface winds forced to 255 at 55 kts. Normal takeoff roll, normal takeoff.Trial #3: KASE, same as above, except surface winds forced to 255 at 200(!) kts. Normal takeoff roll, normal takeoff.Trial #4: KASE, same as above, except surface winds forced calm and winds aloft forced to 255 at 200 kts, with the winds aloft "zone" set to 6000 feet MSL and above, i.e. below field elevation. Normal takeoff roll, normal takeoff.In other words, I couldn't reproduce the problem. Also, on all of my trials, the airspeed increased only slowly after rotation. The wind sock at the airport was standing straight out, but the indicated airspeed on the EHSI (after rotation) was never higher than about 25 kts. (I checked FSUIPC and I don't have any limitations to surface winds.)Anyway, everything has worked fine in all flights since. I'd love to hear your theories.My best-fit explanation for what I saw remains that there was a massive crosswind from the left, causing the plane to weathervane to the left and depart the runway, followed by a massive drift to the right with the wind once airborne, despite benign weather on ATIS and in the forecast. Thanks for your help.---Will

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...