In another thread, there was an excellent chart from a weather balloon sounding. One question, are these an aviation hazard? Also, I thought at one time folks were looking at setting up a system so airliners could become weather condition reporting systems. Both climb and descent would (could) offer a significant increase in detailed temperature, wind, and with a hydrometer, humidity. If automatically reported, it could significantly improve mapping of weather systems and conditions. I thought I once read about it as a proposal. Anyone hear any more about it? Thanks, Bob Wilson
Hi Bob, The skew-T diagram that I posted in your other thread would not constitute a LLWS. Generally, you need a relatively calm boundary layer (generally below 2000 feet) with a strong speed shear gradient above the boundary layer. So essentially you're going from a, e.g., 40 knot headwind to essentially calm conditions which could affect the stability of the plane while landing (you would know better than I about that; I'm not a pilot). Normally, LLWS conditions are encountered during transitional seasons (Spring, Fall) when high wind damage occurs in high terrain (e.g., Smoky Mountains) but the boundary layer in the valley locations is nearly calm. I'm aware of airliners carrying sounding equipment (called ACARS, IIRC; don't know what that acronym stands for). NWS has access to those data through AWIPS, but I don't recall everything that's available with those ACARS soundings (temp/dew point available, IIRC).
"40 knot headwind to essentially calm conditions" That would not be good on short final. This is why Bob & I keep one hand on the throttle when we get close to the ground, and are mentally spring-loaded to push it towards the firewall if the bottom falls out. . There are great opportunities for monitoring many things from aircraft platforms. Some are being done now, with more in the future. Cost is an issue. Japan Airlines makes a lot of CO2 measurements at the flight levels. Maybe other airlines as well. We have talked here about climate models being too coarsely grained. It is not just a cell-size problem, it is an initial values problem. We don't know what values to assign for T, H, U, V, W, etc. for small atmospheric cells, even if the model could crank them. More fine-grain data would be really helpful.
Funny you should mention this, I've had direct experience: On a flight from Hilton Head SC back to Hyde Field, MD, we were chasing behind a strong front. At altitude we had a 40 mph tail wind which for a Cherokee 140 cruising at 100 mph was a heck of a lot of fun. But as we got closer to Newport News, we landed to get fuel and wait out the increasing scud. But within an hour, we saw the whole area to DC clearing and I mean unlimited ceilings and visibility. We took off on the last 100 mile leg and even at 7,000 ft. we had an even stronger tail wind. It was so strong we were not descending fast enough to fly under the TCA. So I did a 180 and for a goof, slowed the plane and put down full flaps . . . and we were suspended in space. No detectable motion relative to the ground. A little power and there we were hovering, yet there was no turbulence. Still we needed to land so I lowered the nose, raised the flaps and did a 180 . . . and suddenly I was dizzy . . . vertigo. Having my field of vision change so much from hover to 140 mph (ground speed) was all it took to 'trip' vertigo. With stars above and urban lights to the horizon, I flipped into 'instrument mode' until the vertigo passed in a couple of minutes. By then we were under the TCA. So I entered downwind, still a pretty good tailwind at 1,000 ft above ground level. The airspeed was right and I proceeded to do a normal downwind, cross-wind with crab, and turned final. Partial flaps, carb heat, and the plane in a steady descent, everything was fine. On downwind, I'd keyed UNICOM and the runway lights were on. Just as I passed over the high power lines, the plane became 'soft.' I had flown through the boundary layer between the laminar headwind and the near still air on the ground. My 75 mph final approach airspeed had suddenly dropped to 60-65 mph in moments. Now Hyde field has an upper and lower section with the runway lights on the upper section. So I lowered the nose, found the runway numbers with the landing light, and flared on the upgrade. With heavy braking, I probably could have turned off at the beginning of the runway lights. When we shutdown the plane at the T-hangar, we could barely feel a slight breeze and it was as quiet as an airport can be at 3:00 AM. Beautiful night sky, you could not tell that just a couple of thousand feet above us the air was zipping along at nearly 50 mph. I could have pushed the throttle in but that would not have given me the airspeed needed RIGHT THEN. Fortunately, I trained at Hyde field and knew the runway well. Lowering the nose was the fastest way to get airspeed and control needed for a safe landing. Bob Wilson
NEVER come in below the glideslope. It limits this option of dropping the nose. My vertigo story involves night flight over a small Carib. island. Turn away from the coast and you see...nothing. Gulp. Look at 'the 6' and make a coordinated turn back towards something you can see.
Are you asking if the weather balloon package is a hazard to flight? Perhaps. Not aware of any encounters between aircraft and a rawinsonde train (the balloon and instrument package). These balloons are released twice daily and rapidly ascend to 50,000 to 70,000 feet and usually spend maybe 45 minutes in the commercial flight envelope. There are 92 rawinsonde reporting stations in North America, so at least that many balloon packages ascending through the atmosphere and drifting with the wind twice a day.
In theory? Yes. In practice however the "big sky, small plane" strategy has been working just fine You are proposing adding extra weight to the planes. Weight costs money. The airlines are fiends about trimming out every excess ounce from their fleets.
Just to be clear, sounding data from commercial aircraft are and have been available to specific user groups (e.g., NOAA). These data are a specific menu item in AWIPS (NWS advanced wx system). ESRL/GSD Aircraft Data Information
We used to land our J-3 across the runway in a strong cross wind! Richard Bach wrote a pretty fun book called "biplane" whe he chronicles flying an old slow biplane across the country. He talks about landing somewhere in central CA iirc, with a wind so strong, he flew the plane right up to the gas pumps! Icarus
