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A couple of fmc questions

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When on autopilot and flying  a flight plan when and where do you activate the approach button? Another question is it only  ILS cat II and cat III that offers autoland or can a cat I also offer autoland?

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When on autopilot and flying a flight plan when and where do you activate the approach button?

What kind of plane are you flying? Typically you're safe to engage the approach button when established on the localizer and below the glide slope. You'll want to have your speed in check prior to doing so and be prepared for landing and approach configuration.


Another question is it only ILS cat II and cat III that offers autoland or can a cat I also offer autoland?

Read both quoted sections below from Kyle with PMDG for the best explanation.


This one is one of the most incredibly odd simisms to me. I've never quite understood where it came from. In a - probably futile - effort to help dispel this myth, I'll attempt to be very clear:


Autoland is rarely used in aircraft operations. It is used when the weather is terrible and it is necessary to conduct a certain type of approach, and it is used to maintain aircraft and crew currency. Heck, some carriers don't pay for the certification and equipment necessary for autoland, and instead use the HGS to sidestep the autoland requirement on certain approaches (which, at the moment, is really only one type, but I'm avoiding naming it because I want to be absolutely clear that autoland and approach type are separate issues - related, but separate).


When a controller clears you for an ILS approach, 99% of the time, you are going to take over manually at some point and land the plane yourself. Despite the - forgive the bluntness here - stupid commentary that people use all the time about how automated aircraft are, airlines, and most actual pilots know how valuable stick time is, and strive to maintain that proficiency in the critical segments of flight (takeoff and landing) at the very least.


That being said, in theory, you can use an ILS signal to autoland in any aircraft that is capable of autoland. The only difference between a CAT I and a CAT III is certification level: the signal has been verified as accurate, with little interference, and is otherwise fault tolerant to ensure it doesn't quit when you really, really need it. It's the same antenna array, sitting at the end of the runway, with the same glide slope shack sitting next to it. That being said, the inverse is also true. Some CAT I installations, though they have LOC/GS arrays capable of CAT III certification, are only certified to a CAT I because of the amount of signal interference, or terrain issues, and so on. The ILS at CRW is an example of this: normal straight in mins for a CAT I approach are 200 AFE, but they are 500 AFE at CRW because of terrain and related signal quality issues.


If we're certifying approaches and changing mins due to signal quality issues, do you really want your aircraft using that signal to autoland? Probably not. For that reason, autolands are generally restricted to CAT III installations (by airline OPSPEC, which is essentially "FAR" if approved by the FAA - note that the FARs do not reference autoland next to any particular approach), due to their being certified at the highest standard. At the same time, if I were flying into IAD, I do not need to be cleared for the CAT III approach over the standard (CAT I) ILS approach in order to use autoland - the array is the same, the signal is the same, the equipment on the plane is the same. You would not want to autoland on a visual approach day, though, as the controllers will not be protecting the signal areas by instructing aircraft to hold short of the ILS Critical Area. Without this, the signal could be compromised. As such, on a visual day, request it from the controller, and they will coordinate it with the tower.


Firstly, CAT IIIa/b/c doesn't have an autoland function. In fact, ILS approaches (regardless of CAT) have no "functions" at all apart from the provisions of a horizontal and vertical path for an aircraft to follow. The CATs simply denote signal strength, clarity and reliability, to a particular certification standard (a CAT III certified array that fails 5 times in a 6 month period gets automatically kicked down to a CAT II array, as an example - all the same equipment though). How an aircraft interprets and acts upon that info (again, regardless of CAT) is a completely separate topic.


To fly a CAT III a/b/c approach requires autoland (AC120-28D), but this is a regulatory requirement alone. This is evident in the fact that if a HGS is installed and approved by the administration, CAT III approaches may be flown manually.


The inverse - autoland requires CAT III - is not true. Therein lies the simism, and that is what I was addressing:

  • ILS approaches, by and large, are not completed in autolands.
  • Autolands can be conducted on any ILS CAT, in theory

    The equipment is all the same - approval may vary. If the OpSpecs approved by the administration only refers to autolands on CAT III arrays, then autolands can only be conducted on the runway with a CAT III certified array at a particular facility.

It is, however, approved if you've included it in your OpSpecs:

FSIMS 8900.1 4-342:


CAT I Autoland or HUD to Touchdown Operations. Autoland or HUD to touchdown operations are required for all CAT III operations, and many operators use autoland or HUD for CAT II, CAT I, and visual flight rules (VFR) operations as well. Part 121, § 121.579©; part 125, § 125.329(d); and part 135, § 135.93(d) prohibit the use of autoland or HUD to touchdown in any operation unless the operator is specifically authorized via OpSpecs. OpSpec C059 and C060 authorize autoland or HUD to touchdown in CAT II and CAT III operations, respectively. OpSpec C061 or H110 authorizes autoland operations in other than CAT II/III operations and OpSpec C062 or H111 authorizes HUD to touchdown in other than CAT II/III operations.

This isn't true, unless it's specified in the OpSpec. You would want to be careful of autolanding in visual conditions as the controllers are not protecting the ILS critical areas, which means signal interference could be an issue. That close to the ground, you wouldn't want that. They would be protecting this area when conducting ILS approaches (at any CAT), so if they only cleared you for the run-of-the-mill ILS approach, you can still autoland (in theory, it's capable; legality is in question if it's a non CAT III array, depending on your OpSpec - see above reference to FSIMS) if you so choose, without getting a specific clearance. To be even more clear, "autoland" is only mentioned in the controller handbook to advise the controller to issue a warning to the crew if a crewmember advises (note: not "requests clearance for") that they will be conducting an autoland when weather is above the LVP cutoff:


7110.65V 3-7-5 b 2:


b. Operators commonly conduct “coupled” or “autoland” approaches to satisfy maintenance, training, or reliability program requirements. Promptly issue an advisory if the critical area will not be protected when an arriving aircraft advises that a “coupled,” “CATIII,” “autoland,” or similar type approach will be conducted and the weather indicates a reported ceiling of 800 feet or more, or the visibility is 2 miles or more.



Note that, while the 7110 refers to "CATIII" in the above text, this is simply because of the connection between the CAT III approach and the requirement for autoland when flying those approaches (if they had a HGS exemption, they wouldn't need to be be testing the autoland, which means they wouldn't be advising ATC of anything).

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 Some aircraft operators recommend that their pilots perform autoland operations routinely in order to reduce pilot work load during marginal MET conditions and after long haul flight,. even when Autoland operations when LVP are not  in operation.



Gerry Howard

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