And what country can preserve its liberties if their rulers are not warned from time to time that their people preserve the spirit of resistance? Let them take arms. The remedy is to set them right as to facts, pardon and pacify them. What signify a few lives lost in a century or two? The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants.
To get to a landing when in poor weather, planes use instrument approaches...very commonly the Instrument Landing System (ILS). There are 3 levels of ILS approaches....Category I, Category II, and Category III [read: "CAT One", "Cat Two", and "Cat Three"....and don't ask me why they use Roman numbers--the "I" and not the "1", "2", or "3"].
CAT III approaches require the Captain to fly the approach while using the autopilot all the way through the landing. There is no requirement to see the runway or any runway lighting until after touchdown.
CAT IIIa is 50' DH (where the runway environment must be positively identified and the ship stable, established to land; the runway visual range or RVR is 200'). The more restricted categories of weather (IIIB and IIIC are lower minima up to zero/zero with automatic runway turnoff and taxi guidance. Not many airports are IIIB/C capable. In any poor weather the workout in the flight deck is impressive, as is the preparation by maintenance crews verifying the ship is capable.
I've been retired a year and a half now, but my former airline used Alert Heights (as opposed to Decision Heights) for CAT III operations.
From one of our manuals..... "Alert heights are used for fail operational Category III operations. Alert height is a height above the runway, above which a Category III approach must be discontinued and a missed approach initiated if a specified failure occurs. Radio altimeters are set to an alert height to assist in monitoring autoland status. Most regulatory agencies do not require visual references below alert height."
DId a few of those in my flying days. You just have to put you trust in the automation and hope the smart guys at their computer desks on the ground knew what they were doing.
The 747 was the first zero/zero capable a/c as I remember. You are more than 30 feet off the deck, so even with bare minimum visibility, you are in the soup. Very cool to see what they can do. I did a jump seat on a A310, and it was automated for the whole trip, even in CAVU. Very interesting to realize you are at the mercy of systems managers imputing correct data to the flying computer. It isn't surprising when the systems managers crash the bird when they have to put their hands on the stick. c.f. Air France 447
Bob Dentice flew the first Cat III. He flew a C-170 that he modified. Bob was my A&P.
A funny story was when he was cleared to land at LAX in weather blo mins. Heard on freq were the airliners holding in the stack all complaining, Why does he get cleared?
He more than earned that paycheck!
ReplyDeleteCAT IIIa
ReplyDeleteDan is probably right.
ReplyDeleteTo get to a landing when in poor weather, planes use instrument approaches...very commonly the Instrument Landing System (ILS). There are 3 levels of ILS approaches....Category I, Category II, and Category III [read: "CAT One", "Cat Two", and "Cat Three"....and don't ask me why they use Roman numbers--the "I" and not the "1", "2", or "3"].
CAT III approaches require the Captain to fly the approach while using the autopilot all the way through the landing. There is no requirement to see the runway or any runway lighting until after touchdown.
azlibertarian
CAT IIIa is 50' DH (where the runway environment must be positively identified and the ship stable, established to land; the runway visual range or RVR is 200'). The more restricted categories of weather (IIIB and IIIC are lower minima up to zero/zero with automatic runway turnoff and taxi guidance. Not many airports are IIIB/C capable.
DeleteIn any poor weather the workout in the flight deck is impressive, as is the preparation by maintenance crews verifying the ship is capable.
Dan already said it. Good job, Dan.
DeleteI've been retired a year and a half now, but my former airline used Alert Heights (as opposed to Decision Heights) for CAT III operations.
DeleteFrom one of our manuals.....
"Alert heights are used for fail operational Category III operations. Alert height is a height above the runway, above which a Category III approach must be discontinued and a missed approach initiated if a specified failure occurs. Radio altimeters are set to an alert height to assist in monitoring autoland status. Most regulatory agencies do not require visual references below alert height."
azlibertarian
DId a few of those in my flying days. You just have to put you trust in the automation and hope the smart guys at their computer desks on the ground knew what they were doing.
ReplyDeleteThe 747 was the first zero/zero capable a/c as I remember. You are more than 30 feet off the deck, so even with bare minimum visibility, you are in the soup. Very cool to see what they can do. I did a jump seat on a A310, and it was automated for the whole trip, even in CAVU. Very interesting to realize you are at the mercy of systems managers imputing correct data to the flying computer. It isn't surprising when the systems managers crash the bird when they have to put their hands on the stick. c.f. Air France 447
ReplyDeleteBob Dentice flew the first Cat III. He flew a C-170 that he modified. Bob was my A&P.
DeleteA funny story was when he was cleared to land at LAX in weather blo mins. Heard on freq were the airliners holding in the stack all complaining, Why does he get cleared?