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Take-Off Runway Change (FMS A/C)  
User currently offlineAM From Mexico, joined Oct 1999, 589 posts, RR: 2
Posted (11 years 8 months 2 weeks 1 day 22 hours ago) and read 2898 times:
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Hi everyone,

Think about busy, multiple takeoff runway airports, like ORD, DFW, IAH, DTW, etc.

Once you monitor ATIS you know about which runways are being used for takeoff, and you make your initial takeoff calculations (Vspeeds, TO power, etc.) based on a "guessed" runway which is entered into the FMS.

What steps have to be followed, what new calculations are required, what has to be done through the MCDU/CDU in order to plan your takeoff on the new runway?

And for example, let's say ORD is "departing" runways 32L, 32L T10, 14L, 04L, 09L. Due to weight restrictions and other variables, you can't use 09L, but you could use 04L with an almost underated, no-flex, TO/GA power takeoff, or a more "comfortable" takeoff on 32L with a more derated TO power. If ground assigns you 09L, I know you just say "Negative due to weight". But what if they assign you 04L? Do you have to accept it or would you rather request a 32L departure? Hope my example was asked well.

What more complicated calculations would you have to make in aircraft that don't have the assistance of a FMS?

Thanks in advance,
AM


"... for there you have been and there you will long to return."
8 replies: All unread, jump to last
 
User currently offlineAM From Mexico, joined Oct 1999, 589 posts, RR: 2
Reply 1, posted (11 years 8 months 1 week 3 hours ago) and read 2801 times:
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Anyone?

Rick767, AAR90, CXflyboy?



"... for there you have been and there you will long to return."
User currently onlineAJ From Australia, joined Nov 1999, 2395 posts, RR: 24
Reply 2, posted (11 years 8 months 1 week 1 hour ago) and read 2780 times:

Changing runways is a fairly simple change in the FMC. A button push to the DEP/ARR page, another to line select the new runway, and perhaps a third to line select a new departure (if applicable). Some departure procedures (SRD/SID) apply to more than one runway so selecting only the runway makes the applicable changes. A quick check of the LEGS page checks that the plan is all linked up and that's it for the departure track.
New takeoff speeds and thrust need to be determined. In our company the performance manual has to be consulted to derive the new settings, which are then entered into the FMC/TMC. Some companies allow FMC derived data.
The changes are simple, but important, as a Pan Am 747 found out at SFO after a runway change. If necessary the aircraft is stopped while the data is checked before committing to a departure.


User currently offlineAAR90 From United States of America, joined Jan 2000, 3474 posts, RR: 47
Reply 3, posted (11 years 8 months 1 week ago) and read 2780 times:

But what if they assign you 04L? Do you have to accept it or would you rather request a 32L departure?

One never has to accept anything. You can specify a specific runway you want to use, but you'll also have to accept the time delay while ATC makes necessary arrangements so you can use it. The vast majority of times one simply accepts the assigned runway unless there is a specific reason you can not accept it. The delays can easily exceed 60 minutes at ORD.

What more complicated calculations would you have to make in aircraft that don't have the assistance of a FMS?

AA Departure Plan includes all necessary data for the 5 "most likely" runway assignments. If what you need is not there, a simple ACARS request will provide exactly what you want in a couple of minutes. Same for V-speed calculations. One can read the performance charts in the Performance Section of the OpMan, or one can request updated numbers for the specific runway via ACARS. ACARS is most pilots' preferred method since it takes the same amount of time and is presented exactly the way you expected it. The charts require a slight amount of thinking.... something no self-respecting airline pilot would willingly do.  Nuts



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently onlineAJ From Australia, joined Nov 1999, 2395 posts, RR: 24
Reply 4, posted (11 years 8 months 1 week ago) and read 2778 times:

Took a while to find, but here are the reports into the Pan Am 747 I mentioned, NTSB summary, and the full NTSB report (pdf).

AAR90, unfortunately the flight dispatcher role in the USA is not available to us in Australia, all our performance calculations are performed by the pilots.


User currently offlineAM From Mexico, joined Oct 1999, 589 posts, RR: 2
Reply 5, posted (11 years 8 months 6 days 23 hours ago) and read 2784 times:
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Thanks a lot for your replies, I really appreciate it.

I didn't know one could request that kind of information via ACARS, sounds very practical. Now I know what's going on when I hear a flight telling ground or tower "...not ready to go yet, waiting for our numbers".

About the AA Departure Plan, is that how the flight plan is called, or do you have a separate plan for departure data at AA?

How does one know, or find out about a certain runway that is simply not usable for takeoff given the present variables? Does the departure plan state that? Here in Mexico City, flights to Europe request 05R over 05L 95% of the time. Many flights to South America and some flights to USA/Canada (i.e. A320 flts MEX-YYZ, MD80 flts MEX-DFW, etc.) make this request as well.




"... for there you have been and there you will long to return."
User currently onlineAJ From Australia, joined Nov 1999, 2395 posts, RR: 24
Reply 6, posted (11 years 8 months 6 days 22 hours ago) and read 2765 times:

A request for a longer runway is usually made with Clearance Delivery when requesting an airways clearance.
It is very common in Sydney when the shorter runway 07/25 is in use for long haul aircraft, especially LA services, to request runway 16R/34L, even with a crosswind. When the charts start to encroach on maximum performance capabilities a longer runway will be requested.
In fact, here in Sydney recently (and probably again today) with the temperatures in the low forties (celcius) some flights have been forced to stay on the ground until the temperature falls later in the day, even with the longer runway!
The NOTAMS issued to the crew will contain any information that may affect the performance requirements for the flight's departure. Erecting of cranes or other objects near the runway end can cause perfomance penalties, or even close a runway. The flight dispatcher planning the flight will impose any perfomance limits necessary or plan the flight from another runway. Our takeoff weight may be limited for this reason, so load control is also notified.
This information is also broadcast on the ATIS if it affects the airport's normal operation.
I'll leave the AA stuff to AAR90!


User currently offlineAAR90 From United States of America, joined Jan 2000, 3474 posts, RR: 47
Reply 7, posted (11 years 8 months 6 days 19 hours ago) and read 2759 times:

AAR90, unfortunately the flight dispatcher role in the USA is not available to us in Australia, all our performance calculations are performed by the pilots.

Oops, sorry to confuse y'all. The dispatcher has nothing to do with the ACARS & TPS functions I mentioned. If the info you're requesting is already calculated DECS (Dispatch Environmental Control System) provides the data automatically. If not, an alert is sounded at the appropriate Load Controller desk and that controller (or any Load Controller seeing the alert) can send the data in about 5 keystrokes. Virtually everything is automated.

"...not ready to go yet, waiting for our numbers".

This usually means the flight crew is awaiting the final load "closeout" information (weight/balance, pax count, etc.). This info is required prior to takeoff to verify the TPS (Takeoff Performance System) data is accurate and usable. If new information is required, then the phrase means the crew is awaiting the additional info --pretty rare for N.A. operations.  Wink/being sarcastic

About the AA Departure Plan, is that how the flight plan is called, or do you have a separate plan for departure data at AA?

The Departure Plan is but one small part of the entire AA Flight Plan/Release. For a "domestic" operation the Departure Plan uses less than 10% of the paper the rest of the Flight Plan/Release requires.

How does one know, or find out about a certain runway that is simply not usable for takeoff given the present variables? Does the departure plan state that?

"NOT USABLE -- WEIGHT" (or whatever parameter prevents its use). We'll also see zeros (000 000 000) or dashes (--- --- ---) where data would normally be so we can't screw up and use invalid data.

Here in Mexico City, flights to Europe request 05R over 05L 95% of the time. Many flights to South America and some flights to USA/Canada (i.e. A320 flts MEX-YYZ, MD80 flts MEX-DFW, etc.) make this request as well.

DECS is not accessable from home so I don't know the specifics of MEX runways, but a quick look at Jeppesen charts shows 05R takeoff distance available is 12,795 feet while 05L takeoff distance available is 11,325 feet (page 10-9A).

I'll leave the AA stuff to AAR90!

AA dispatchers & load controllers have the ability to manually place limitations on the flight and the computer programs will automatically consider those when doing all of their calculations. All-in-all a pretty nifty and very reliable system. Which explains why AA has found no need to upgrade it even though it is mostly vintage 1970's technology.



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineLdaops From , joined Dec 1969, posts, RR:
Reply 8, posted (11 years 8 months 5 days 7 hours ago) and read 2712 times:

Change the data in the FMC is more easy to do than explain it.
For the performance we calculate the performance according the ATIS and also we calculate the perfomance for a second rwy.


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