Go Back   Airline Pilot Central Forums - Find your next job as a Pilot > >
Technical Technical aspects of flying
 

Welcome to Airline Pilot Forums - Connect and get the inside scoop on Airline Companies

If this is your first visit, be sure to check out the FAQ. Join our community today and start interacting with existing members. Registration is fast, simple and absolutely free.


User Tag List

Reply
 
Thread Tools Search this Thread Display Modes
Old 01-30-2019, 07:02 AM   #1  
Line Holder
Thread Starter
 
Joined APC: Sep 2017
Posts: 92
Default ACARS vs dispatch release

Had a flight the other day (fly CRJ-900) ..
Dispatch paperwork said planned takeoff weight was something like 74,200 lbs. Max takeoff weight 79,000lbs, roughly.
Loaded the numbers into ACARS.. said our weight was about 74.2.. as planned.. however it said our max weight was 74.7 or something like that. Why?
Am I missing something basic here? Letís say we had extra bags and were overweight? We canít go. But what if ACARS is in-op and we do paper w/b.. we could be several THOUSANS pounds over and be ok according to the release, right?!

Other question, re: required landing length.
We need a certain length to stop the aircraft, but we add 60% to be legal and safe. ACARS will say our min length is, letís say 3000í but 4800í is the required. SO, if you if you get letís say, a Spoileron fail caution or whatever, you add 20% to the landing distance. Is that 20% of the lower or higher number? (Read an ASAP where a crew couldnít land in SBA because adding the 20% put them at needing more runway length than was available; they diverted)
If ACARS is in-op, we use the dispatch release which only has the distances with the 60% added already, correct? So if we had to add 20% do we add it to the releaseís numbers? Or figure out what the min landing length is off that number and add 20% to that?
MysteriousMrX is offline   Reply With Quote
Old 01-30-2019, 07:15 AM   #2  
Gets Weekends Off
 
Airbum's Avatar
 
Joined APC: Dec 2005
Posts: 564
Default

. At my company your questions most likely answer is that AERO data calculated the max allowed take off weight based on the current conditions you input into the program for your planned take off. Reference your Performance data section of your Aircraft Operating Manual. You can change the inputs into AERO data to increase your allowed max take off weight ie: use max thrust, change flap setting, change runway.

ACARS is a communication and data link system. At my company it does not do performance data or weight and balance problems.

We use AERO data which is a performance data program for dispatch in which we receive the information over the ACARS. AERO data program is also used for actual landing performance data while airborne.

AERO data takes MEL performance limitations and applies them to your landing data solution. For both dispatch and actual landing performance calculations
Airbum is offline   Reply With Quote
Old 01-30-2019, 08:39 AM   #3  
Line Holder
 
Joined APC: Dec 2012
Posts: 37
Default

Quote:
Originally Posted by MysteriousMrX View Post
Had a flight the other day (fly CRJ-900) ..

Other question, re: required landing length.
We need a certain length to stop the aircraft, but we add 60% to be legal and safe. ACARS will say our min length is, letís say 3000í but 4800í is the required. SO, if you if you get letís say, a Spoileron fail caution or whatever, you add 20% to the landing distance. Is that 20% of the lower or higher number? (Read an ASAP where a crew couldnít land in SBA because adding the 20% put them at needing more runway length than was available; they diverted)
If ACARS is in-op, we use the dispatch release which only has the distances with the 60% added already, correct? So if we had to add 20% do we add it to the releaseís numbers? Or figure out what the min landing length is off that number and add 20% to that?

Iím not sure I got your question correctly, but I as far as I understand, landing within 60% of the runway is for dispatch purposes only. Once youíre airborne, you use whatever your company provides for calculating your in-flight landig distance, with the actual conditions at the time including any failuers you may have had enroute. In addition to the company-provided software you may have on board, the QRH should have a section for calculating in-flight landing distances with failures.
sigler is offline   Reply With Quote
Old 01-30-2019, 10:41 AM   #4  
Gets Weekends Off
 
Twin Wasp's Avatar
 
Joined APC: Oct 2007
Position: Asst. button pusher
Posts: 2,392
Default

Did you compare the data the release was based on versus the numbers you imputed to get your numbers? Was there a change in runways, runway condition, temperature or wind? Did your numbers tell you what the limiting factor was, runway or climb performance? Did you call your dispatcher and ask about the difference?

121.195 says you can not depart to an airport unless at the planned landing weight you are able to stop within 60% of the landing distance available (not add 60%.) To make the math easy, if the performance date says you need 6000 feet to land, the runway you plan to land on must be 10,000 feet. Once you takeoff that goes out the window. Say your destination airport has two parallel runways, 10,000 and 7500 feet long. You can land on the shorter runway because you only need 6000 feet to stop. If you have an issue enroute and your procedure requires you to add a performance penalty you would add it to the 6000 landing distance.

As pointed out above your QRH should have some performance in flight tables to get an idea what your landing distance will be. And some airlines use an onboard computer to figure performance so it doesn't matter if ACARS is inop.

The FAA has been pushing manufacturers and airlines to use factored landing data which has an additional 15% added. So if the manufacturer determined that your aircraft with a given set of conditions needed 5000 feet to come to a stop the tables would say you 5750 to come to a stop.
Twin Wasp is offline   Reply With Quote
Old 01-30-2019, 11:33 AM   #5  
Line Holder
Thread Starter
 
Joined APC: Sep 2017
Posts: 92
Default

Thx for the responses. I may be overthinking some of it..
Iíll try putting in the exact weather conditions in the ACARS next time and see what it gives- just seemed odd it was so far off compared to the release.

Ok I worded the 60% thing wrong. I think.
So when ACARS says unfactored distance is 2968 and minimum required is 4312 (estimating numbers here) .. it just means I can stop the aircraft in 2968í. But weíre saying 4312 to be safe so the runway needs to be a length that is equal to 7186 (4312 is 60% of 7186)

So now letís say we have to add 20% to our length for some QRH reason. .. Iím a multiplying 2868 by 20% or 4312?

Now ACARS is out. Using the release. It says my min reqíd landing for the conditions that exist is, letís say 4455í (ACARS usually gives shorter lengths). Same Qrh scenario. Iím adding 20% to that number?
MysteriousMrX is offline   Reply With Quote
Old 01-30-2019, 12:41 PM   #6  
Line Holder
 
Joined APC: Dec 2012
Posts: 37
Default

Quote:
Originally Posted by MysteriousMrX View Post
Thx for the responses. I may be overthinking some of it..
Iíll try putting in the exact weather conditions in the ACARS next time and see what it gives- just seemed odd it was so far off compared to the release.

Ok I worded the 60% thing wrong. I think.
So when ACARS says unfactored distance is 2968 and minimum required is 4312 (estimating numbers here) .. it just means I can stop the aircraft in 2968í. But weíre saying 4312 to be safe so the runway needs to be a length that is equal to 7186 (4312 is 60% of 7186)

So now letís say we have to add 20% to our length for some QRH reason. .. Iím a multiplying 2868 by 20% or 4312?

Now ACARS is out. Using the release. It says my min reqíd landing for the conditions that exist is, letís say 4455í (ACARS usually gives shorter lengths). Same Qrh scenario. Iím adding 20% to that number?
Are you asking about a failure before take off, as in the airplane is dispatched with a MEL item that affects landing performance? If so, multiply your total RLD (4312í in your example) by whatever factor your MEL tells you to. Once in flight, or if you have a failure in flight, use whatever means your company gives you to calculate your in-flight landing distance, or the QRH. Forget about the numbers on your release, they no longer apply once youíre airborne.
sigler is offline   Reply With Quote
Old 01-30-2019, 06:46 PM   #7  
Line Holder
Thread Starter
 
Joined APC: Sep 2017
Posts: 92
Default

Quote:
Originally Posted by sigler View Post
Are you asking about a failure before take off, as in the airplane is dispatched with a MEL item that affects landing performance? If so, multiply your total RLD (4312í in your example) by whatever factor your MEL tells you to. Once in flight, or if you have a failure in flight, use whatever means your company gives you to calculate your in-flight landing distance, or the QRH. Forget about the numbers on your release, they no longer apply once youíre airborne.
No.. no MEL. weíre in flight. All is good. ACARS says runway is 8500í long, so I guess we need 5100í to stop. But given our weight, winds, etc.. it says we can conceivable stop in 3500í. Now weíre descending and we get a caution message and run the QRH. It says add 20% to the landing distance. Am I adding 20% to 3500 or 5100? (I know either way I can land.. but I want to be right about this)

Question 2: same scenario but ACARS went no-comm and Iím relying on the release. It says dry runway at this weight requires 5250, letís say. Do I add 20% to that? If thatís the case then I should be adding 20% to the higher number w/ ACARS, right?
MysteriousMrX is offline   Reply With Quote
Old 01-30-2019, 07:38 PM   #8  
Gets Weekends Off
 
2StgTurbine's Avatar
 
Joined APC: Feb 2010
Posts: 1,285
Default

This stuff should have been covered in indoc. I suggest you write an ASAP so your airline's training department will include this in their training program.
2StgTurbine is offline   Reply With Quote
Old 01-31-2019, 06:19 AM   #9  
Line Holder
Thread Starter
 
Joined APC: Sep 2017
Posts: 92
Default

Quote:
Originally Posted by 2StgTurbine View Post
This stuff should have been covered in indoc. I suggest you write an ASAP so your airline's training department will include this in their training program.
k.. and the answer is? or you donít know?
MysteriousMrX is offline   Reply With Quote
Old 01-31-2019, 06:35 AM   #10  
Line Holder
 
Joined APC: Dec 2012
Posts: 37
Default

Quote:
Originally Posted by MysteriousMrX View Post
No.. no MEL. weíre in flight. All is good. ACARS says runway is 8500í long, so I guess we need 5100í to stop. But given our weight, winds, etc.. it says we can conceivable stop in 3500í. Now weíre descending and we get a caution message and run the QRH. It says add 20% to the landing distance. Am I adding 20% to 3500 or 5100? (I know either way I can land.. but I want to be right about this)

Question 2: same scenario but ACARS went no-comm and Iím relying on the release. It says dry runway at this weight requires 5250, letís say. Do I add 20% to that? If thatís the case then I should be adding 20% to the higher number w/ ACARS, right?
Once youíre in flight, you no longer use the numbers on your release. I am not sure what method your company uses for figuring out in-flight performance calculations (mine uses Airbusí FlySmart on ipads), but regardless of what it is, it will be derived from the same source the QRH uses. So you can always rely on the QRH. There should be a section for landing distances with failures in there somewhere. If there isnít, you just use the regular landing distance section and multiply whatever result you get by the factor listed for that particular failure, and then by 1.15.
sigler is offline   Reply With Quote
 
 
 

 
Reply
 



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Related Topics
Thread Thread Starter Forum Replies Last Post
Open Time Release ... Pathetic GetRealDude FedEx 16 11-29-2016 04:44 PM
Ozone RA tool on flight plan release 155mm Cargo 9 01-25-2016 07:05 AM
Delta to buy stake in China Eastern Airlines snowdawg Delta 263 08-19-2015 02:17 PM
ACARS technical info thingsthatfly Technical 4 04-06-2010 05:10 PM
ACARS chime? GOCKY Major 17 10-28-2009 04:11 PM


All times are GMT -8. The time now is 01:53 AM.


vBulletin® v3.9.3.5, Copyright ©2000-2019, MH Sub I, LLC dba vBulletin
User Alert System provided by Advanced User Tagging v3.3.0 (Lite) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Website Copyright ©2000 - 2017 MH Sub I, LLC dba Internet Brands

Search Engine Optimization by vBSEO 3.6.1