Skip to comments.Totally Irrelevant Weather Fact for the Day
Posted on 06/05/2005 9:09:28 PM PDT by raygun
On this day:
1912: Mt. Katmai (AK) erupted and spewed a glowing flood of hot ash that traveled ~15 miles into an area known today as "the land of a thousand smokes". Ash from this eruption was deposited to a 12" depth within 100 miles of the eruption (although this ash thankfully wasn't glowing).
1993: an F3 tornado w/60-mile path tracked from Bertrand, NE to Cushing, NE over the course of ~4.5 hours. While near the Amherst, NE area, it remained stationary for ~90 minutes (time to get out the dirtbikes and go for a ride). Only two people were injured (probably the two who thought riding motorcycles near a stationary tornado to be a good idea) during the storm.
1997: outflow winds from NW AZ thunderstorms produced a wall of dust that swept through Las Vegas Valley and reduced visibility to ~0'. All departing flights from McCarran Airport were grounded for 0.75 hour. It is unclear on how incoming flights got on in all that.
As to the 1997 McCarran incident, I can answer that. It is called ILS, or Instrument Landing System. With it, a pilot can land in a rain barrel of his/her choice.
I know this all means something, and probably ties in to the fact that a moose bit my sister while a tornado was going through our hometown's only cheese factory in 1988. It is seared, seared in my memory....
That ain't nothing. Back in my day, we had to walk to school dodging snowflakes big as cars.
Yeah, well, we had to walk uphill to and from school, in a blinding July snowstorm. Barefoot & penniless. With my little brother on my back.
The rain in Spain stays mainly on the Plain, unless they are in the middle of a drought.
With the exceptions of some extremely recent automation existing in certain jumbo jets, pilots still have to go visual within at least 100' of the runway. Whether or not McCarren is even capable of handling jumbo jets is unknown. With the most sophisticated equipment, ILS has the capability to guide a pilot right down to the runway - zero Decision-Height (DH) and zero visibility, but whether or not McCarren has the necessary equipment to allow zero DH (or fully automatic landings) is another story entirely.
Instrument landing system (ILS) facilities are a highly accurate and dependable means of navigating to the runway in IFR conditions. When using the ILS, the pilot determines aircraft position primarily by reference to instruments. The ILS consists of:
ILS is classified by category in accordance with the capabilities of the ground equipment. Category I ILS provides guidance information down to a decision height (DH) of not less than 200 ft. Improved equipment (airborne and ground) provide for Category II ILS approaches.
A DH of not less than 100 ft. on the radar altimeter is authorized for Category II ILS approaches.
In order to land, the pilot must be able to see appropriate visual aids not later than the arrival at the decision height (DH) or the missed approach point (MAP).
Any or all of the following lighting systems may be provided at a given facility: approach light system (ALS), sequenced flashing light (SFL), touchdown zone lights (TDZ) and centerline lights (CLL-required for Category II [Cat II] operations.)
For the longest time, the minimums for an ILS approach were 3000' visibility and a 200 ft. ceiling. However, once the reliability, accuracy, and capability of the autopilot increased, runway-visual-range (RVR) tramsissometers (a more reliable measurement of visibility began to become commonplace, ILS minimums began to appear on approach plates, too.
As these changes evolved, the FAA designated three categories of ILS approaches, with successively lower minimums. Later, they decided that three categories didn't fit all of the desired situations and further expanded it. The following shows the full range of ILS approaches:
|I||200 feet||2400 feet|
|I||200 feet||1800 feet||With touchdown zone and runway centerline lighting .|
|II||100 feet||1200 feet||Half the minimums of a standard Cat I approach|
|IIIa||below 100 feet||700 feet|
|IIIb||below 50 feet||less than 700 feet but not less than 150 feet|
|IIIc||No DH||No RVR limitation||Pray that your electronics and autopilot are reliable.|
You'll notice that the Cat. IIIc approach is a zero-zero approach.
While the autopilot is in full control of the aircraft for any approach below Cat. I, Cat. II or Cat. III approaches can't be initiated capriciously on the whim of the pilot at just any airport simply because the weather minimums require it. Those approaches, like all the others, must be approved and published.
Even the foregoing was utterly notwithstanding, I'm unsure how many pilots would deliberately pilot an aircraft into a dirt/air suspension lithometeor with zero visibility unless they were interested in engine restarts on approach in IFR conditions. I think that would make a fine Olympic sport however.
I'm calling you on that one xJones. I did some digging, and there's no record of a cheese factory in your hometown. And frankly, moose aren't even indiginous to the area. I think you're pulling our leg on that.
The era of zero zero pilots in the pilot and co-pilot seats is coming. Of course, ALPA might have something to say about that!
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