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Stop Margin is based on OAT / FLEX Temp?

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Stop Margin is based on OAT / FLEX Temp?

Old 17th Feb 2019, 23:39
  #21 (permalink)  
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are manufacturers required to punish RTOW further by flexing the speeds also?

Short answer is no. The speeds largely come out as a result of the available (presumed) thrust and weight. As a very general observation, and presuming we are above the Vmc limiting weight range, V2 will relate to weight (stall speed), VR will relate to thrust and weight and is calculated to result in achieving V2 at screen height, while V1 will depend on the relationship between thrust, drag, ambients (including assumed temperature) and runway distances.

I wouldn't sweat it too much. The protocols require a degree of conservatism ... if you want to have a bit more up your sleeve then don't flex quite so much but that, really, is not necessary routinely.
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Old 18th Feb 2019, 15:59
  #22 (permalink)  
 
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OP,

Great question, and kudos to you for bringing it up, resulting in an indepth conversation!

Good to question the automation and to fully understand the resultants (and question them)
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Old 19th Feb 2019, 12:12
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That was a very good question with nice replies and links to interesting documents.
After 20 years of flying the A320 series I learned something new today.

I'll admit then, until now, whenever Flysmart came up with a small stop margin with a high FLEX temp (At much lower OAT), I went into 'conservative mode'. If possible I would use intersection t.o. figures from full rwy or 'modify' the runway with a length reduction at the end or some other way to create some extra stop margin.

I'll become a little bit less conservative now that I've learned the effect on the stop margin caused by the difference between FLEX and OAT temperatures.

There's one small advice I'd like to give to Ondraayyy though (Off topic)
Originally Posted by Ondraayyy
...Of course I did not argue with him, but I kinda disagreed with him on that....
Ondraaayyy, why did you say 'of course'? Was it because you thought that doing it his way was safe and legal anyway and the timing was not good to start a discussion at that point in time, or was it because he's the captain, you're the f/o and challenging your captain is not part of the normal cultural behavior in your part of the world?

The first reason is fine. The fact that your captain brought it up himself in cruise is a credit to him. The second reason would be a very dangerous attitude.

In any airline, in any part of the world, the f/o challenging the captain (and vice versa) when one does not understand or agree with what the other one is doing should be perfectly normal!
Never ever let a captain talk you into a situation that you would consider unsafe. Don't be a pain in the ass nagging about any minor deviation from SOP, but DO speak up when you suspect it might be important!
(Don't feel offended if you personally didn't need this advice.)
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Old 19th Feb 2019, 14:41
  #24 (permalink)  

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sabenaboy, now you're assimilated. If your SW has the option of showing extended results, check TOD (all engines). Measured on a chart, it can be compared with the actual performance at about 10 ft RA if DRY, or at lift-off point when WET.
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Old 19th Feb 2019, 16:55
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Originally Posted by FlightDetent
If your SW has the option of showing extended results...
The company I used to fly for allowed us to do that. The software of the company I fly for now, (They 'assimilated' my previous employer) doesn't allow it.
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