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him225

The request to taxi message

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what does it refer to when pilot asks atc for taxi route to departure "..with "Charlie" ready to taxi IFR"? At first I thought it could be the taxiway the plane is at but that doesn't seem to match up in the sim.

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"Charlie" refers to the current ATIS in affect.  Lets the controller know that pilot has received and acknowledged.

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As Tom said.

You can try it yourself. In sim tune in to atis for the airport you are at and listen to it all. You will hear information Charlie, or information whatever along with all the other info for winds, runways in use, clouds and pressure etc.

If the pilot requesting gives the wrong designator it means he won't have the most up to date information. Atis changes every hour or when conditions have changed enough to warrant an update.

 

I don't mean to patronise you as I don't know how much you know about atis so apologies if you know all this.

 

Here is a link with some real world examples and explanations of atis.

 

https://en.m.wikipedia.org/wiki/Automatic_terminal_information_service

 

 

Chris

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Just tried it in the sim and it matched. Hadn't realty given much attention to the atis designator at the beginning before. 

 

How useful would this be though (except for minimizing conflict with expected departure runway) as ATIS/conditions might change by the time aircraft reaches the runway? For the purpose of pilot awareness/flight safety I would imagine it be more appropriate to mention it when asking takeoff clearance, or during clearance delivery if it is more about flight planning?

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Just tried it in the sim and it matched. Hadn't realty given much attention to the atis designator at the beginning before. 

 

How useful would this be though (except for minimizing conflict with expected departure runway) as ATIS/conditions might change by the time aircraft reaches the runway? For the purpose I would imagine it be more appropriate to mention it when asking takeoff clearance?

 

First of all, weather doesn't change that soon. Secondly, you need to prepare for instance the FMC for take off (SID) and so on: if you would be at the runway and ask for takeoff clearance, it would be a bit odd, to say the least, if ATC would tell you to taxi to another runway and you would have to reprogram everything. Not only odd, it would become an uncontrollable mess on the airport. :wink: So they simply decided to do it this way and once you have received clearance, you will proceed accordingly, no matter what. Even if ATIS changes during taxi, you will proceed with 'your' ATIS in mind and ATC knows that.

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Sorry I edited the post to be more specific while you replied.

 

I thought of the issues you mention, but I think the call serves as an assurance and wouldn't lead to as much operational problems.

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Currently in training for a PPL in England at Cambridge airport and have learned that ATIS is very important.  It is not just for the benefit of the pilot but for the ATC as well.  If you didn't have  ATIS  at the larger airports, you would have many pilots calling ATC just to find out the latest weather conditions, runway in use, barometric pressure (for setting altimeter), etc and this would take a lot of controllers just to pass this information along to the pilots. ATIS allows the pilots to get this information without taking the valuable time of the air traffic controllers . This frees up the controllers to focus on monitoring traffic and giving clearances and other instructions to the pilots.

 

When you get ready to depart on a flight, you start your engine do preliminary engine checks, and then you turn on your radio and listen to ATIS, copying the details onto your kneepad. Here in the UK, once you have performed preliminary engine checks and listened to ATIS, you make your first contact with ATC, and tell the the controller that you are ready to taxi and have "information charlie" or whatever the latest ATIS message. The only thing you repeat back to the controller is the barometric pressure. The controller confirms that you have the current ATIS information and that your barometric pressure is correct, and gives you instructions to taxi. If the ATIS message has changed (from charlie to delta, e.g. he/she will tell you.

 

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I do get the requirement of a way for confirming latest atis between pilot and atc, I do not suggest otherwise or pilot stop using atis and rely on atc for weather. I imagine things would function mostly as they do if pilots were not required to confirm knowledge of latest atis to atc. I am just wondering of the stage at which the confirmation is done, why not at clearance delivery (which would be first contact with atc?) or at takeoff clearance?

Any particular reason why baro pressure is stated separately as well when already mentioning the atis code?

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ATIS should be confirmed as close to departure as possible - for GA aircraft, this can be done at the hold as part of a VFR clearance. IFR is usually confirmed earlier (often at pushback) to make sure the pilot has set the altimeter correctly (as part of a checklist).

 

The reason for confirming the QNH is because it is THE most important piece of information in the ATIS - if you have not set your altimeter correctly then you will be flying at the wrong altitude, which can cause you problems with, to name a few, other traffic, landing in IMC conditions, Autopilot not slamming you into the ground  and mountains!!!

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