RTOW Min and Max Acc Heights

[AlphaFloor27]

Hello, I have the following question regarding RTOW charts:

http://s7.postimage.org/vfd7h9v9n/la_foto_1.jpg

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?

[AVApilot]

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.

[PIK3141]

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 ?

[safelife]

Min 400 ft max 1500 ft ARTE

[PT6A]

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.

[de facto]

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).

[mutt]

Axl Kowalski...... forgive me for shouting but it appears to be required:

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 :{:{:{

[PT6A]

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.

[john_tullamarine]

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.

[AlphaFloor27]

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.

[PT6A]

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.

[AlphaFloor27]

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.

[AVApilot]

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?

[PT6A]

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.

[Brotti]

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.

[Sciolistes]

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.

[hvogt]

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 (http://www.pprune.org/tech-log/396654-maximum-acceleration-altitude.html#post5338925) 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.

[mutt]

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.

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.

[FE Hoppy]

It's threads like this that make we wonder where it all went wrong :-(

[hvogt]

nope, its not industry standard, we have planes with 5 and 10 minutes takeoff thrust.Hence the 'more or less'.10 minutes of max continuous thrustHow silly of me. I meant TOGA thrust.

[KBPsen]

I prefered to delete it. ...So, if the mods would like this post to stay, so be it...You shouldn't just roll over and let the mod get away with it.

If moderators can assume ownership of posts made by others, then the announcement that is on top of all forums about post responsibility should be deleted, as you can not be responsibly for something that you have no control over.

It is frankly arrogant and outrageous behavior.

[HazelNuts39]

@PIK3141 (post#3)
You are basically correct. Perhaps it is useful to clarify that the limiting obstacle is likely to be significantly lower than 500 ft. The accel height on the RTOW chart is the gross acceleration height. The net acceleration height has to clear obstacles by 35 ft and is less than the gross height. How much less depends on the particular conditions.

@Brotti:
the max Accel Alt equals 10 min@togaThat is correct for airplanes which have obtained approval for the use of 10 minutes of TOGA after failure of an engine in takeoff, otherwise it is 5 min@toga. There is no specific requirement reference for that. The scheduling of performance data normally assumes that cleanup and acceleration to final takeoff climb speed is conducted with takeoff thrust or power. Hence it must be completed before the time limit for the use to TOGA is reached.

@hvogt:
Publishing a maximum acceleration altitude in the AFM might be a requirement according to CS 25.1585No, I don't think it is. The time limit(s) for the use of TOGA are limitation(s) that must be stated in the AFM Limitations section in accordance with CS 25.1521(c)(1)(ii). The net takeoff flight path data in the AFM Performance section required by CS 25.1587(b) must respect that limitation and will usually schedule the maximum acceleration altitude as a function of operational variables such as weight, altitude, temperature and configuration, as a 'limit of validity' of the net takeoff flight path data. The net flight path data is information provided in the AFM to permit compliance with operating rules such as FAR Part 121 or EU-OPS that contain obstacle clearance requirements.

[vilas]

I would recommend you to go through FOBN getting to grips with performance it will clear many doubts.

[john_tullamarine]

You shouldn't just roll over and let the mod get away with it.

Points of interest -

(a) deleting the first post deletes the thread - which is the problem. Not too concerned about posts past the first being deleted as only that post is deleted. If there are no posts other than the first post, and the thread subject is trivial or probably not of interest to others, usually I will let the deletion stand.

(b) I have no problem with thread deletions if there is a good reason - hence the suggestion to PM me with the details.

(c) if anyone has a problem with mod actions, simple redress is to complain up the chain with details. Airing angst in the thread is a waste of time.

Sorry if you feel put out ...

[HazelNuts39]

Vilas,

I've noted a minor error and a few omissions in the requirements references in Getting to Grips, but nothing that conflicts with my post. Apparently Airbus models have all been cleared for 10 min TOGA.

[vilas]

The FOBN is offcourse very old now but to understand basics it is pretty good. OEI TOGA 10 mts and all engines 5 mts. (outside FAA territory) is approved.

[HazelNuts39]

Vilas,

The option to obtain approval for 10 mins use of take-off thrust OEI was introduced in both US and EU regulations IIRC somewhere in the 1970's or 1980's. Approval is not automatic but requires specific substantiation from both the engine manufacturer and the airframe manufacturer. For some older aircraft that did not have that option in the original certification the manufacturers may have obtained approval later and offered it to their customers as a 'retrofit'.

[hvogt]

Thank you for the clarification, HazelNuts39. I'm afraid my above post was written in haste and not particularly well thought out. I appreciate you took the time to quote a reference.

[pilot-737]

I think you are confused by comparing 2 different situations !!
1st your company minimum acc height is 400 feet in case of 2 eng t/o
So your climb performance is much better at 400 ft with your present rate of climb you will be able to clear your obstacles
2nd situation you have an an egine failure at v1 : at this point disregard your company's minimum acc height and apply your minimum acc height delivered by your airport analysis table ! 529 ft in this case !
Minimum and max acc altitudes are 1eng out acc altitudes ... These altitudes are not applicable in both 2 eng and engine out conditions because
A) your clb gradient is different so yous minimum acc altitude is the most restrictive due to obstacles air density etc so single engine
B) the max is applicable to limit your engine to thrust time to 10 min (imagine if you needed 10 min to reach 1861 and to accelerate to green dot speed with 2 engines)
Now .... If your airport analysis height is much higher lets say 1400 ft and you engine fails just after your company's accelaration height of 400 ft ... You most probably have to reselect toga thrust / ( lever already in clb detent -> flx thrust not available anymore) and open clb with your present speed selected and present config until reaching 1500ft...
(this is the only point that you should discuss about with your managers about your sop ;) )

In your fmgs to page insert
1950/1950(thr red/acc) and 2080 (eng out acc altitude )
If your engine failure occurs between v1 and 1950 ft .... You should better be safe side and delay accelaration until reaching 2080ft ;)
Don't forget in case of eng failure the lvr clb is not displayed on your fma And your vertical mode will frozen in srs (until YOU change it by selecting vs0,op clb etc)so your 1950 ft should be disregarded if your engine out altitude (reminder purpose only-not affecting your autopilot/fd mode)is higher(2077) :)

[HazelNuts39]

pilot-737

If the engine-out accel height is 529 ft and you do your all-engine acceleration at 400 ft, I wonder if you have verified that at the end of the all-engine acceleration you have not penetrated the engine-out gross flight path?

P.S. Have you also considered a 4-engined airplane?

[pilot-737]

Hazelnuts39
The engine out accelaration procedure according to airbus is :
Push to level off at acc altitude...
Clean up the aircraft while maintaining this altitude (529 ft)
And then select green dot open climb mct thrust
With 2 engines you are in uninterrupted climb and you DON'T level off at 400ft
In addition you reach 400 feet in a shorter distance than in a OEI condition so yes you are able to to reach 529 ft while you climb and clean up simultaneously without penetrating your obstacle identification surface ! Imagine the inertia and your rate of Climb at 400 ft With 2 engines...if you suddenly lose an engine you will be at 529 ft before your failed engine fails in windmilling condition (129 ft : 1500 ft / min = 5.16 sec ) Don't forget that in OEI you have less than 50% of your 2 engines gradient...
I'm always talking about 2 eng acft and the second segment as this is the point when talking about the MINIMUM acceleration altitude :)
I think a 4 engine acft may have a final segment concern which may affect your max acceleration altitude but this is an other story ;)
as I said the problem may arise If your min acc altitude is much higher than your standard acceleration altitude and if you experience an engine failure AFTER your standard thrust reduction altitude in this case :)

[de facto]

Pilot-737

If you are using RTOW charts you must not accelerate below the published engine out acceleration height even if you have not had an engine failure and your company sop calls for a standard lower acceleartion.

Ie:If your company sop is 800 ft ACC two engines and RTOW chart min acc height is 400 ft then 800 ft acceleration is ok.
However if the RTOW chart gives you a 900 ft height acc,you must not accelerate at 800 but at 900.
The reason behind it is mentionned in post #30 by hazelnut39.
as I said the problem may arise If your min acc altitude is much higher than your standard acceleration altitude and if you experience an engine failure AFTER your standard thrust reduction altitude in this case

Who decides and sets the automatic thrust reduction or manually select it in your aircraft?

[pilot-737]

Defacto
With engine failure at v1 and a minimum accelaration height of 900 ft you need x distance
If you t/o with 2 engines your climb performance is more than 50% better (basic 1engine vs 2 engines theory) so you will be at 800 ft in in less than x distance
Considering your climb performance, your aircraft's inertia and the reaction time ( thrust set from t/o to clb) you will be at 900 ft in a shorter distance than X(so b4 your obstacles) even if your engine fails. Now if during your thrust reduction you experience an engine failure YES you should re apply to thrust(to be able to accelerate ) and level off at 900 ft (you will actually be well above) I say again this is not the theory.This is my own opinion for your example 800 vs 900 ft and this in not applicable to all cases !!!

[mustafagander]

All engine performance on a twin is way, way better than that. Remember that it is certified to fly safely on one but you almost invariably have two. Remember also that climb performance is directly related to excess thrust available and on both you have it in spades. That's one reason why it feels simply tragic in the sim with a V1 cut.

[john_tullamarine]

Several considerations follow from the requirement to make the AEO operation OK so far as OEI is concerned -

Providing that the AEO takeoff is constrained to

(a) remain above the calculated OEI profile at all times and in all circumstances

(b) remain at a higher energy state than the OEI profile

(c) track as per the OEI escape (this can be a problem with turn radius)

you will be able to sort out the failure case along the departure without too much angst.

There is the sideline consideration where the OEI tracking is different to the AEO departure. In this case, the ops eng group SHOULD have done the sums to make sure you stay sweet. I have it on good authority that such does not always happen .. about the only things you can do there is

(a) work for a good operator, as I have been fortunate to do

(b) make sure you have a good general knowledge of the subject so you are well placed to know when to ask awkward questions ...

The devil is in the detail and it is NOT amenable to winging it on the fly.

Your ops engineering folks are paid to do the sums for you and, indeed, the company's normal operating procedures should be incorporated into the OEI special procedures so the pilot ends up with a one size fits all for each runway procedure ....

[de facto]

Pilot737

Your assertions may well lead you to disater one day.

The 900 vs 800 was just an example as a general guideline NOT to start acceleration (with 2 engines) BEFORE the single engine out published acc height.

Your perf ops know more than a simplistic view on excess thrust.

mustafagander
. Remember also that climb performance is directly related to excess thrust available and on both you have it in spades. That's one reason why it feels simply tragic in the sim with a V1 cut.


The reason may simply be lack of training/skills.

[pilot-737]

De facto ... As I said I'm talking about 100 or 129 ft difference and not 1000 ft difference (read my 1st post please ) .... In aviation and more specifically in abnormal situations ... We must THINK and analyse our current status as abnormal and emergency procedures cover about 95 to 99 % of the possible scenarios but not every particular case with any unpredictable factor (multiple failures etc) .If you apply only the theory and you don't adjust your theory knowledge + your skills to the rest 5-1 % you may end to a disaster ...
Don't forget ... After some incidents the abnormal / emergency procedures may change and follow the "non standard actions" of the crew involved if proven more efficient than the current procedure ;)
My answer is not a guideline as you said but just an answer about the initial question... We must have a practical way of thinking ....

[de facto]

As JT wrote:The devil is in the detail and it is NOT amenable to winging it on the fly.

Pilot737,
De facto ... As I said I'm talking about 100 or 129 ft difference and not 1000 ft difference
I agree but when do you put a stop at your guessing game?300,400,700ft?999ft?
In aviation and more specifically in abnormal situations ... We must THINK and analyse our current status as abnormal and emergency procedures cover about 95 to 99 % of the possible scenarios but not every particular case with any unpredictable factor (multiple failures etc) .

We are talking about delaying a normal 2 engines acceleration to a min acceleration height,,,you are not in an abnormal situation nor in multiple failure scenario.
You are already making holes to your cheese in a normal situation.
If you apply only the theory and you don't adjust your theory knowledge + your skills to the rest 5-1 % you may end to a disaster
With theory comes knowledge,a safe pilot is one who would follow standard procedures and use his knowledge not to put his aircraft in a situation where superior skills are needed in the first place.
Don't forget ... After some incidents the abnormal / emergency procedures may change and follow the "non standard actions" of the crew involved if proven more efficient than the current procedure
The Captain can deviate from SOPs if the out of the ordinary/abnormal situation requires such action.In that case,he better be damn sure of his knowledge/experience as if his detour fails,he will be hanged by the balls..

[john_tullamarine]

My suggestion for consideration is

(a) if things are going normally follow the company SOP - one presumes that the company has been responsible and reputable and done all the right things .. .doesn't guarantee the outcome but ticks all the boxes

(b) if something goes awry, generally a reputable ops manual will have something in the way of guidance for the crew. For something as straightforward as a simple engine failure .. the SOP should cover it

(c) if you find yourself in a situation of multiple significant problems (Sioux City comes to mind) you do the best you can with the information, circumstances and skills you and your crew and external resources can muster. Good reason for making sure one knows more than the basics about the aeroplane ...

[pilot-737]

I agree but when do you put a stop at your guessing game?300,400,700ft?999ft?

As I Already wrote Each situation is different ...
If you want me to give you a standard value you don't understand my answer !
It's an other situation if the difference is 1500 - 1700
An other situation if you have 3000 (noise abatement ) and 3300
And an other situation if you have 400-529.
Of course If your sops give 400ft and your engine out is 1400 ... It's out of the common sense To reduce your thrust at 400 ft !
So De facto if you think we must stick to the procedure ... In case of suspected windshear / turbulence during departure should we apply 529 ft height as thrust reduction / acceleration altitude ? ;)
I know 1st of all we must delay our t/o ... But when you finally decide to depart will you stick to the SOP ? Or use your judgment to adjust your thrust reduction height to this SUPPLEMENTARY but not abnormal / emergency situation ? ;)

[de facto]

This is becoming silly,but lets bite..
So De facto if you think we must stick to the procedure ... In case of suspected windshear / turbulence during departure should we apply 529 ft height as thrust reduction / acceleration altitude ?

Standard thrust reduction (A/B/1/2) dont start before 800 AAL,i guess you know that.
Windshear,you mean convective? or gusts?
Convective windshear a no go obviously.
If you suspect or are reported gust windshear or turbulence,thrust reduction and acceleration would be initiated as normal(acceleration not below minim acc height) and full thrust would be used.
If you encounter turbulence,tighten your harness bit more.
If the turbulence happens to be severe and you decide to accelerate below the engine min acc height and below the noise level altitude,(reduce load factor on your flaps and pax)then i think it is OK because you are now dealing with a situation that requires an acceleration rather than a theorytical engine failure.

If you actually encounter windshear,(windshear alert on your ND)apply the windshear recovery procedure which is to disconnect the AT and maintain your config,flaps...
If you get out of it and start accelerating(retracting flaps) and it is below the noise acceleration point then it is not a problem.

But if you think i will plan to accelerate at 400ft(lets say it is the minimum) and reduce thrust at (800 ft minimum by std noise) just because there is turbulence or windshear reported,the answer is NO.

This what you posted pilot737 and what i dont agree with and flying into airports like chambery or Innsbruck you may understand..
Minimum and max acc altitudes are 1eng out acc altitudes ... These altitudes are not applicable in both 2 eng and engine out conditions because