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RTOW Min and Max Acc Heights

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RTOW Min and Max Acc Heights

Old 1st Mar 2013, 18:21
  #21 (permalink)  
 
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Originally Posted by AlphaFloor
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.
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Old 1st Mar 2013, 22:05
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@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@toga
That 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 25.1585
No, 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.
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Old 2nd Mar 2013, 03:16
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I would recommend you to go through FOBN getting to grips with performance it will clear many doubts.
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Old 2nd Mar 2013, 08:45
  #24 (permalink)  
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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 ...
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Old 2nd Mar 2013, 09:02
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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.
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Old 2nd Mar 2013, 09:43
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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.
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Old 2nd Mar 2013, 10:18
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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'.

Last edited by HazelNuts39; 2nd Mar 2013 at 10:29. Reason: missing plural 's'
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Old 2nd Mar 2013, 11:41
  #28 (permalink)  
 
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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.
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Old 3rd Mar 2013, 09:17
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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)

Last edited by pilot-737; 3rd Mar 2013 at 09:37.
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Old 3rd Mar 2013, 18:59
  #30 (permalink)  
 
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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?

Last edited by HazelNuts39; 3rd Mar 2013 at 19:01. Reason: P.S. added
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Old 3rd Mar 2013, 20:59
  #31 (permalink)  
 
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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
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Old 5th Mar 2013, 06:52
  #32 (permalink)  
 
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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?

Last edited by de facto; 5th Mar 2013 at 06:59.
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Old 6th Mar 2013, 15:00
  #33 (permalink)  
 
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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 !!!

Last edited by pilot-737; 6th Mar 2013 at 15:02.
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Old 6th Mar 2013, 21:27
  #34 (permalink)  
 
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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.
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Old 6th Mar 2013, 21:56
  #35 (permalink)  
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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 ....
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Old 7th Mar 2013, 01:26
  #36 (permalink)  
 
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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.

Last edited by de facto; 7th Mar 2013 at 03:32.
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Old 7th Mar 2013, 20:39
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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 ....

Last edited by pilot-737; 7th Mar 2013 at 20:40.
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Old 8th Mar 2013, 02:06
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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..

Last edited by de facto; 8th Mar 2013 at 02:09.
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Old 8th Mar 2013, 02:21
  #39 (permalink)  
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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 ...
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Old 8th Mar 2013, 07:29
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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 ?

Last edited by pilot-737; 8th Mar 2013 at 07:36.
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