Airbus EFB T.O Performance
Thread Starter
Joined: Nov 2006
Posts: 367
Likes: 0
From: Tropics
Guys thanks for the discussion.
Is there anywhere at all we can get a copy of any document that explains what logic does the EFB calcuLates its figures on? Like he no reverser credit on dry runways.
Is there anywhere at all we can get a copy of any document that explains what logic does the EFB calcuLates its figures on? Like he no reverser credit on dry runways.
Joined: Aug 2015
Posts: 30
Likes: 0
From: Around 22N 113E
Interesting topic. In addition to all your assumptions, the line up distance used to offset Nose Wheel and MLG are important. Perhaps educating the end user too.
For dry assumptions, yes, the reverses are not considered, however, if your stop Margin shows 2m, that’s assuming the stopping action took place at V1 plus 2 sec reaction time. Decelerating is now with 50% of the referrers that you have anyway. (Practically speaking). Therefore the Stop margin is brought quite a way forward and will always look different from the computation versus the real thing. That’s what and how we try to educate our guys.
Also someone has mentioned before, the assumptions are based on an avaerge call to stop, cold and work brakes.
Wind components assumed for the calculation at this of 50 or 150% depending if it’s head or tail. Again very conservatively put, additional margins are built into the assumptions.
Your EFB administrator can set up the output of the performance module to display a range of Flex temps and or TOGA. However, you’re now not using the optimisation process ‘as advertised’
For dry assumptions, yes, the reverses are not considered, however, if your stop Margin shows 2m, that’s assuming the stopping action took place at V1 plus 2 sec reaction time. Decelerating is now with 50% of the referrers that you have anyway. (Practically speaking). Therefore the Stop margin is brought quite a way forward and will always look different from the computation versus the real thing. That’s what and how we try to educate our guys.
Also someone has mentioned before, the assumptions are based on an avaerge call to stop, cold and work brakes.
Wind components assumed for the calculation at this of 50 or 150% depending if it’s head or tail. Again very conservatively put, additional margins are built into the assumptions.
Your EFB administrator can set up the output of the performance module to display a range of Flex temps and or TOGA. However, you’re now not using the optimisation process ‘as advertised’
Joined: Sep 2011
Posts: 18
Likes: 0
From: india
EFB
Can aircraft movement be seen in EFB. Can the crew use EFB for identifying Runway so that take off incident on unassigned Runway or Taxiway can be avoided. There had been many such incidents in the world.
Joined: Jul 2015
Posts: 176
Likes: 230
From: UK
With TMAXFLEX you are calculating the maximum theoretical outside temperature for which a takeoff can be safely achieved and reducing the thrust output accordingly. If you're unable to alter that value, you can artificially alter the environment to create conditions which favour higher thrust.
Personally I have not reduced runway length to do so, however I frequently factor in a nil headwind or slight tailwind in order to "worst case" things. I've found even a slight tailwind has a significant impact on the takeoff performance, given the factorisation.
In addition we regularly use intersection departure calculations even when departing from full length.
Joined: May 2019
Posts: 66
Likes: 39
From: Ireland
We just got this feature this year. It's not supposed to be the primary way to identify runways or taxiways but it's a great tool for situational awareness
Joined: May 2007
Aviation Qualifications: ATP+Mil
Posts: 108
Likes: 88
From: Somewhere at the Milky Way
I've seen many people tweaking the EFB to make the remaining distance to something they like more. I am not very in to this procedure but I can understand their fears.
Joined: Mar 2001
Posts: 4,563
Likes: 35
From: I wouldn't know.
Yes you can do it, but the position depicted can be off by quite some feet depending on the GPS signal quality received on the EFB. The Airbus' SOP for this is identify runway and intersection on the lining up checklist. Inserting a TO shift at the PERF page also helps to raise awareness, and yes before somebody notes, I know that with GPS HIGH inserting a TO shift is not necessary, I am just pointing out that seeing a number there before lining up makes you remember that you are doing an intersecting departure and the numbers are for that case. Compare this number with the runway left behind and reassure yourselves the numbers look right.
I've seen many people tweaking the EFB to make the remaining distance to something they like more. I am not very in to this procedure but I can understand their fears.
I've seen many people tweaking the EFB to make the remaining distance to something they like more. I am not very in to this procedure but I can understand their fears.
Eidolon
Joined: May 2001
Posts: 2,244
Likes: 62
From: Some hole
Mind you, I get annoyed when people are looking at their phone when walking down the sidewalk or driving rather than looking where they are going.
Joined: Apr 2021
Posts: 74
Likes: 25
From: Southern Hemisphere
Maximum engine wear saving is achieved by the first few degrees of Flex. That benefit is lost with ‘creative accounting’.
The accelerate-stop distance on a dry runway is the greater of the following values:
a) ASDN-1 dry = Sum of the distances necessary to:
- Accelerate the airplane with all engines operating to VEF
,- Accelerate from VEF to V1 (1) assuming the critical engine fails at VEF and the pilot takes the first action to reject the takeoff at V1
- Come to a full stop (2,3)
- Plus a distance equivalent to 2 seconds at constant V1 speed
1 Delay between VEF and V1 = 1 second
2 ASD must be established with the “wheel brakes at the fully worn limit of their allowable wear range” [JAR/FAR 25.101]
3 ASD shall not be determined with reverse thrust on a dry runway
b) ASDN dry = Sum of the distances necessary to:
- Accelerate the airplane with all engines operating to V1
, assuming the pilot takes the first action to reject the takeoff at V1
- With all engines still operating come to a full stop
- Plus a distance equivalent to 2 seconds at constant V1 speed
ASDdry = max of {ASDN-1 dry, ASDN dry}
The accelerate-stop distance on a wet runway is the greater of the following values:
• ASDdry • ASDN-1 wet = same definition as ASDN-1 dry except the runway is wet1
• ASDN wet = same definition as ASDN dry except the runway is wet
ASDwet = max of {ASDdry, ASDN-1 wet, ASDN wet}
Influence of V1 on Accelerate-Go/Stop Distances
For a given takeoff weight, any increase in V1 leads to a reduction in both TODN-1 and TORN-1. The reason is that the all engine acceleration phase is longer with a higher V1 speed, and, consequently, in case of an engine failure occurring at VEF, the same V2 speed can be achieved at 35 feet at a shorter distance.
On the other hand, TODN and TORN are independent of V1 as there is no engine failure, and thus no consequence on the acceleration phase and the necessary distance to reach 35 feet.
On the contrary, for a given takeoff weight, any increase in V1 leads to an increase in both the ASDN-1 and ASDN. Indeed, with a higher V1 speed, the acceleration segment from brake release to V1 is longer, the deceleration segment from V1 to the complete stop is longer,
and the 2 second segment at constant V1 speed is longer.
Last edited by T54A; 21st January 2025 at 04:53.
Joined: Sep 2011
Posts: 18
Likes: 0
From: india
I think the best way to identify the runway is by looking ahead through the front window rather being distracted looking to the side at an iPad.
Mind you, I get annoyed when people are looking at their phone when walking down the sidewalk or driving rather than looking where they are going.
Mind you, I get annoyed when people are looking at their phone when walking down the sidewalk or driving rather than looking where they are going.
