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Old 26th Feb 2013, 18:51   #1 (permalink)
 
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RTOW Min and Max Acc Heights

Hello, I have the following question regarding RTOW charts:



That's for a runway with an elevation of 1548' AMSL as per chart. It says that your min acc height should be 529'. My airline uses 400' as the standard acc height for almost all runways, including this particular one, so the acc altitude in this case would be 1.950', as per airline SOP. That's of course below what the RTOW charts says it should be (2.077'). Not much but still.

So? Am I missing something? FCOM says those heights and altitudes in the chart are just the "min and max acc height/altitude", nothing about EO condition or something that would explain that difference between what the RTOW charts says it's the minimum (2.077' QNH) and what my airline uses all the time (1.950' QNH).

Any thoughts?

Last edited by AlphaFloor27; 28th Feb 2013 at 02:34.
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Old 26th Feb 2013, 19:50   #2 (permalink)
 
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The minimum Accel. Alt is there due to obstacle clearance, the maximum Accel Alt equals 10min@TOGA

I really don't see a good reason reason to accelerate 130ft below the calculated Accel Alt, why go against something calculated by the Airbus Airport Analysis software? Might as well make up your own Vspeeds while you're at it.

What is the OEI accel alt for SCL rwy 17L? I hope it isn't 400ft agl.
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Old 26th Feb 2013, 19:53   #3 (permalink)
 
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You have to clear your limiting obstacle using the engine out Net Take-Off Flight Path NTOFP by 35 feet. So, in your example is there an obstacle near 500 ft agl that pushes your acceleration height upwards, given the RTOW will be seeking to calculate a best weight ?
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Old 26th Feb 2013, 22:07   #4 (permalink)
 
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Min 400 ft max 1500 ft ARTE
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Old 26th Feb 2013, 22:43   #5 (permalink)
 
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I honestly think your airline needs to revisit it's SOP.

As you are not using the LPC-NG a good practice would be for them to conduct a study of the route network and then select an AA that would be suitable for all airports on the network.

This would help to allow a standard EO strategy that is easier for crews to remember when things go south.

Of course, depending on your route network there may be a handful of airports that require their own EOSID and a different AA due to obstacles / terrain.

Can you tell me if your airline is teaching you to stop ECAM actions at 400' accelerate and then resume ECAM? Or are they teaching you to accelerate once above AA and engine is secured?

Here is an example from my company: -

STD is used for all procedures when a straight climb to 1500ft above the runway end threshold can be obtained before turning towards the engine failure point. If the clean-up has been performed before 1500ft AAL then climb straight ahead to 1500ft AAL before initiating a turn as described in the EOSID. (the minimum ENG OUT ACCEL altitude is usually 1000ft AAL).
The procedure is designed such that acceleration is allowed to be completed before
commencing the turn.
e.g. STD. At 1600’ turn left to XXX HP.
Note: Once MSA is reached or in VMC, or when under radar control it is not necessary to continue to the hold as long as obstacle clearance can be assured.

NON-STD is used for all procedures that cannot be categorized as STD !.
Usually they have an initial turn before 1500’ above the runway end threshold.
e.g. NON-STD. At D4 XXX turn right to intercept R360 XXX. At 2000’ turn right to XXX HP.
Due to obstacle clearance requirements, it is imperative that any NON-STD EOSID is followed exactly – even if the engine is not secure at the specified turn point, the turn must still be commenced at the specified point.
An additional note ‘maintain V2 TKOF flaps until..../ during first turn’ may also be used. This requires the acceleration is not commenced until a defined point.

Last edited by PT6A; 26th Feb 2013 at 22:48.
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Old 27th Feb 2013, 01:43   #6 (permalink)
 
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Let your Company know about this issue.
If you use speeds based on this table then you MUST use an Acceleration stated in this table.(your pic is reeaaaaally bad)..
Min Acc is based on obstacle /level off and Max Acc on 10 min TOGA(one engine).
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Old 27th Feb 2013, 04:42   #7 (permalink)
 
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Axl Kowalski...... forgive me for shouting but it appears to be required:

Quote:
ALL TAKEOFF PERFORMANCE IS BASED ON ENGINE FAILURE AT VEF, YOU AIRLINE SOP IS DOWNRIGHT DANGEROUS AND ILLEGAL
Now you can bring that statement to your airline standards department and see what they think! Just remind them that you are planning to clear any obstacles by 35 feet (net), if the Airbus software has increased the Min Acceleration Height to 529 feet rather than 400 feet, then this is the minimum height that you can accelerate and CLEAR THE OBSTACLE. In your case you will crash into the obstacle 94 feet below the peak.

Gotta love SOP's
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Old 27th Feb 2013, 05:25   #8 (permalink)
 
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Axl Kowalskii,

I don't mean to offend, but are you a type qualified and line released pilot? If not - that's fine and it's great you are seeking further understanding about performance and interpreting the RTOW charts.

If however you are a line released pilot.. then it is rather worrying as pilots in your airline either are unclear about the SOP or worse your airline has the SOP's exactly as you describe and are not meeting the minimum performance requirements on some takeoffs - thus invalidating any obstacle clearance and RTOW calculations.
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Old 27th Feb 2013, 22:29   #9 (permalink)
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We prefer that threads are not deleted as others may be interested in the discussion.

If, on the other hand, there is some good reason for removing a thread, the OP is always at liberty to raise that with the mods.
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Old 27th Feb 2013, 22:54   #10 (permalink)
 
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Just to clarify some things:

I am a line released A320 FO.

We do not use this charts, we use LPC NG, I just wanted to gain some knowledge beyond what the FCOM says about the RTOW charts, that's all. We have tailor made EO SIDs for all runways that need one. EO ACC ALT is 1500' AFE for most of the runways we operate, some special runways have their own AA, always higher than 1500' AFE.

Having said that, I thought the replys to my post would be focused on solving a very reasonable question, but I feel asumptions were made that got this post into another kind of discussion. Of course is somewhat my fault by not giving the complete picture right away. That's why I prefered to delete it.

So, if the mods would like this post to stay, so be it, but if that's the case, I feel obligated to clarify the things I mentioned above.

Cheers.

Last edited by AlphaFloor27; 27th Feb 2013 at 22:56.
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Old 27th Feb 2013, 23:11   #11 (permalink)
 
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Axl,

You said:

"That's for a runway with an elevation of 1548' AMSL as per chart. It says that your min acc height should be 529'. My airline uses 400' as the standard acc height for almost all runways, including this particular one, so the acc altitude in this case would be 1.950', as per airline SOP. That's of course below what the RTOW charts says it should be (2.077'). Not much but still."

Now you say:

"We do not use this charts, we use LPC NG, I just wanted to gain some knowledge beyond what the FCOM says about the RTOW charts, that's all. We have tailor made EO SIDs for all runways that need one. EO ACC ALT is 1500' AFE for most of the runways we operate, some special runways have their own AA, always higher than 1500' AFE."

If you are using LPC NG why does you're FCOM talk about RTOW charts at all? We use LPC NG and my FCOM only talks about LPC NG.

Something does not sit right with the question you asked! However, hopefully you may of now informed your airline what they are / were doing is dangerous.
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Old 27th Feb 2013, 23:57   #12 (permalink)
 
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I don't know why the FCOM has a RTOW chapter, but it does, and we use LPC NG for our every day operations. What I have told you are the facts, you all are free to make whatever assumptions you want.

My interest in this forum is purely academical, hope this topic stays that way.
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Old 28th Feb 2013, 03:17   #13 (permalink)
 
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Axl, I apologize if I somehow offended you, please understand that it does seem strange for any company to go against something as basic as this.
If you are using LPC NG for your everyday ops make sure the values entered into the MCDU reflect those from the software, if not then have a chat with the pilot (or copilot) and insert the correct values even if these go against company policy, it'll save your butt should things go sour on the day you least expect it.

I'm guessing you fly for LAN?
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Old 28th Feb 2013, 03:36   #14 (permalink)
 
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AVA,

He needs to go further than that. The data that is in the LPC needs to be crosschecked because at the end of the day it is only as good as the LPC Administrator.










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Old 1st Mar 2013, 13:47   #15 (permalink)
 
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Max. Accel. Alt on rtow charts

Quote:
the mac Accel Alt equals 10 min@toga
Can anyone post me a ref. for that? I've come across with this somewhere but can not find it again..
Thanks.
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Old 1st Mar 2013, 14:24   #16 (permalink)
 
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Quote:
The minimum Accel. Alt is there due to obstacle clearance, the maximum Accel Alt equals 10min@TOGA
I reckon extending the second segment too far could compromise obstacle clearance in the fourth segment too.
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Old 1st Mar 2013, 15:49   #17 (permalink)
 
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Quote:
Can anyone post me a ref. for that? I've come across with this somewhere but can not find it again..
I just asked myself the same question. From this post I gather the 10 minutes are, more or less, an industry standard.

Publishing a maximum acceleration altitude in the AFM might be a requirement according to CS 25.1585, although I couldn't find further specifications in the relevant AMCs. Maximum TOGA thrust time must be published according to CS 25.1583 (b) (1) and 25.1521 (c) (1) (ii).

I wonder if there is indeed any provision that prescribes 10 minutes of TOGA thrust to be available. I guess CS-E might even require demonstrations of longer periods at TOGA thrust which are then factored with safety margins and end up as 10 minutes in the AFMs, but I'm really guessing here.

Like Brotti, I would appreciate a little help with references.

Last edited by hvogt; 1st Mar 2013 at 22:36.
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Old 1st Mar 2013, 17:34   #18 (permalink)
 
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Quote:
I gather the 10 minutes are, more or less, an industry standard.
nope, its not industry standard, we have planes with 5 and 10 minutes takeoff thrust.

Quote:
prescribes 10 minutes of max continuous thrust to be available.
Whats your concept of "continuous"?

Look at the definition of stage 2, its based on takeoff power, therefore if the takeoff limit is 5 minutes or 10 minutes will depend on the AFM limitations for takeoff thrust.
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Old 1st Mar 2013, 18:13   #19 (permalink)
 
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It's threads like this that make we wonder where it all went wrong :-(
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Old 1st Mar 2013, 18:15   #20 (permalink)
 
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Quote:
nope, its not industry standard, we have planes with 5 and 10 minutes takeoff thrust.
Hence the 'more or less'.
Quote:
10 minutes of max continuous thrust
How silly of me. I meant TOGA thrust.
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