View Full Version : V1 Cut obstacle clearance.

9th Mar 2009, 10:51

Question for you performance guru's....

IF there is no emergency turn published for a departure in your airline for your aircraft type. What are the basics for performance to clear obstacles? If I'm not mistaken it something like 900m left/right of extended centreline upto 1500AGL, the rest I'm not sure. Any ideas??:ugh:

Pugilistic Animus
9th Mar 2009, 16:56
IF there is no emergency turn published for a departure in your airline for your aircraft type. What are the basics for performance to clear obstacles?That question sounds frightening to me:\

it can take up to 10.4 NM to reach 1500' agl

I know that, For example Old Smokey, assures obstacle clearance to MSA and gives you a place to hold Mutt and John_Tullamarine are also very conservative, but the bare minima are all written up, in your case JAROPS1???

in the past one could add up the total distance of all of the segments and then use obstacle charts to determine max runway weight, but I don't think many folks do it that way anymore

I hope one of the performance guys here can clarify this; but it sounds bad at first glance


FE Hoppy
9th Mar 2009, 18:09
OPS 1.495
Take-off obstacle clearance
(a) An operator shall ensure that the net take-off flight path clears all obstacles by a vertical distance of at least 35 ft or by a horizontal distance of at least 90 m plus 0,125 x D, where D is the horizontal distance the aeroplane has travelled from the end of the take-off distance available or the end of the take-off distance if a turn is scheduled before the end of the take-off distance available. For aeroplanes with a wingspan of less than 60 m a horizontal obstacle clearance of half the aeroplane wingspan plus 60 m, plus 0,125 x D may be used.

10th Mar 2009, 08:17
V1 Cut? Just what is that then? A type of haircut?
If you mean an engine failure after take-off, then please say so.
In which case, post #3 explains it fully.

10th Mar 2009, 09:11
rubik101 - a V1 cut just a slang of having an engine failure AT V1. Something normally done in the sim training excerise...

Old Smokey
10th Mar 2009, 12:01
There are several ways to address this problem, this is one person’s approach. Irrespective of the approach taken, all aircraft required to comply with FAR 25 (and it’s equivalents) MUST make full analysis of all obstacles in the Takeoff path until reaching 1500 feet, or a higher altitude if dictated by obstacles.

Ideally (mandatory in some states) this higher safe altitude should be the MSA. (In Australia this is mandated in the AIP, but surprisingly, not in the applicable performance regulations, CAO 20.7.1B).

If we are to contain an EOSID procedure within the MSA altitude constraints, that implies that we must reach Safe Altitude within 25 miles, yet, for a 2 engined aircraft 1st, 2nd, and 3rd segments will often exceed 30 miles. Thus, it may be easily seen that for a 2 engined aircraft at it’s limiting weight, a turn is not desirable, but a necessity if we are to stay within 25 nm.

A certain Obstacle Analysis provider beginning with J (who have a far bigger litigation budget than mine) don’t provide any EOSID if there are no limiting obstacles within 30 miles straight ahead. Fine, but what do you do at 30 miles (often still in the 3rd segment)? I cite Melbourne RWY 34 as an example.” J” sees no problem straight ahead within 30 miles, so, after providing an increased Minimum Acceleration Altitude, lets you go and fly without any special procedure. There might be a mountain at 30.1 miles (there isn’t in this case), but their system does not consider it. What is the MSA? There is none, at 30 miles you have no reference MSA. If you make a Left turn back at MAA (as you would if still in the 3rd segment), terrain contact is a distinct PROBABILITY. If you make a Right turn back, you will survive, but might be deafened by the constant “Terrain, Terrain” calls from the GPWS. Lots of near misses.

The modus operandi that I use in creating EOSIDS is to –

(1) Maintain Runway Track for as long as possible, within terrain constraints, but with a turn (after considering turn radius and lateral splay) inside 25 miles,

(2) After the turn, track to a Holding Pattern shaped “Safe Climb” area, where continued climb to MSA may be conducted. After reaching MSA, FAR 25 et al is discarded, and Pans-OPS (TERPS) take over. Sometimes this is a published Holding Pattern, but more commonly a developed Radio-Nav pattern with the lowest terrain.

(3) This then is the Takeoff Area that I develop, Initial Runway Track (sometimes a Runway end turn), Track or Tracks to a “Safe Climb” Holding Pattern, and the Holding Pattern itself. Throughout this entire Takeoff Area, flight may be conducted at MAA with obstacle clearance assured, even though still below the MSA.

The basic Tracking requirements are as FE Hoppy describes them, i.e. the required Track (NOT HEADING) with a 7 Degree and 8 Minute splay on either side, plus 90M. The Splay continues until intersection with approved Radio Nav Tracking, whereafter the Radio-Nav tolerances apply.

Alternatively, for aircraft with on-board ability to fly Track, the lateral splay may cease upon reaching a nominal parallel margin. (I think that the Australian margin is too small, and use 1852M (1 nm), and 2 nm in the Holding Climb).

Before you can do any of this, you will need a GOOD obstacle analysis, and, guess what? Pilots are not issued with good obstacle data, unless you’ve had it supplied by the Company or a contract supplier. Australia is the exception with good Public Domain Obstacle GRADIENT data from Supplementary Takeoff Distances, but this is limited to 15,000 M (8 miles), a damned good start, but at a 1.6% Gradient, that will only “protect” you for the first 800 feet. After that, you’re on your own to MSA, or Minimum Radar Vectoring Altitude.

The “Normal” data given pilots, e.g. Approach charts are a long way from good enough. They only show the major obstacles, not the smaller “closer in obstacles” that are gonna getcha. Consider a 100 ft radio mast 1 mile from the runway end, being so low it will not be shown on any of the “regular” charts, but, for a 2 engined aircraft it IS a CRITICAL Obstacle after considering 1st Segment. A 500 ft obstacle at 6 miles from the Runway end will probably be shown on the chart, as it is higher. It LOOKS threatening, but, in fact, is not a critical obstacle.

So what to do? First, obtain data for the more dangerous closer in dangerous stuff. Easy in Australia, obtain Type ‘A’ charts elsewhere. (OLS charts are great if you can obtain them. J_T can, but he has friends in high places). After the limit of this closer in (note that I didn’t say close in) data, obtain High detail topographical charts with close contour intervals. For the proposed EOSID, account for the CVA (Chart Vertical Accuracy) at the next highest contour, CHA (Chart Horizontal Accuracy) all the way, build up a series of obstacle “steps”, and finally, obtain the elevation of the highest obstacle in the entire Takeoff Area. To all obstacles, make allowance for trees, man-made structures etc.

Plot the EOSID on the Topo chart, and apply the splay. Consider the maximum and minimum turning radii for all turns in the procedure.

Run a series of Runway Used Vs distance to obstacle performance checks to “zero-in” on the optimum Field/Obstacle limit considering 1st and 2nd segment climbs. Note the LOWEST Gradient usable for the 2nd Segment Climb (Important).

Calculate the height of the Highest Obstacle in the entire Takeoff Area above the Lowest point on the Runway. Multiply this Delta H by the Lowest 2nd Segment Gradient plus 0.8%, and divide by the Lowest 2nd Segment Gradient. Add to this the Highest Runway Elevation + 35 feet (or 50 feet for a Runway End Turn). This is the Minimum Acceleration Altitude (MAA). (I further increase MAA for the lowest AFM Temperature allowed, a cold weather correction, some don’t do this).

That’s the “back of a Postage Stamp” version, there’s a lot more to it, but Danny has band width limitations.

Now, what do you want to do? Aim it and go, hoping for the best, or insist that your operator spend a few (quite a few) bucks on getting proper airport analysis and EOSID development?

VERY IMPORTANT NOTE – The “J” that I spoke of in derogative terms earlier is DEFINATELY NOT John_Tullamarine, he’s a true professional. (Use your imagination).

Fly safe – Avoid the rocks!


Old Smokey

Tee Emm
11th Mar 2009, 11:18
Reminds me of when I flew the 737 Classic for a German charter operator. The runway analysis for a Greek island required a curved take off procedure through 90 degrees which was over the water. Flap retract height was 800 feet. Nothing else mentioned. Only problem was another island dead ahead at 10 miles from the departure runway with a spot height of around 1500 feet dead on track. In IMC we would have gone in during the acceleration phase.

On return to base I asked the performance engineers how come the spot height of 1500 ft was not taken into account? Their reply was the Greek CAA supplied obstacle charts did not include the island on track. The performance engineers said it was up to the pilots to know about the spot height and turn to avoid it.

11th Mar 2009, 12:03
If I may add some comments to OS's comprehensive post..

(a) MUST make full analysis of all obstacles in the Takeoff path until reaching 1500 feet, or a higher altitude if dictated by obstacles.

It is a great concern that many operators don't worry too much about this ... ie there is some good fortune associated with the reliability of modern aircraft.

(b) In Australia this is mandated in the AIP, but surprisingly, not in the applicable performance regulations, CAO 20.7.1B.

The operational implementation (20.7.1B) of the airworthiness requirement (101.5/6 - now long gone) made inference of such a requirement. The AIP words were introduced quite some years ago by a Canberra operations chap motivated by the best of honorable intentions but not much background understanding of the realities of the engineering. The amendment was made to require the GA pilot to play operations engineer with his light twins in a manner roughly similar to what the airlines did with their far greater resources. After considerable argument I got agreement from higher up the chain to rescind the amendment (which I thought was a bit onerous and impracticable) .. however, as often happens, behind the scenes backroom manoevring saw that squashed and I eventually gave up .. however, I did frame the letter so that I could have the occasional giggle over the whole matter ...

(b) will often exceed 30 miles.

For a critical twin OEI operation, 50 miles is a useful ROM for the distance to a useful height (we all used to cite the Diesel 9 as being the archetypical example of this ..

but a necessity if we are to stay within 25 nm.

The alternative is to do a lot of obstacle work yourself for those difficult places ..

(c) A certain Obstacle Analysis provider

If I am inferring who OS is referring to correctly, I would say that, on the basis of an audit I did quite some years ago, they do a good job in what they do .. but, as cited by OS, there is a gap between that and what would be nice (necessary ?) to have for the operation. There were reasons for their policy and, if I am reading OS correctly, I am surprised that they haven't varied the approach as we had some detailed discussions on just this sort of problem.

(d) Australia is the exception with good Public Domain Obstacle GRADIENT data from Supplementary Takeoff Distances

As the surveys normally are done in the conventional manner, rather than being a strict inclinometer survey, the published gradients are calculated from the (x,y,z) triplets .. so, if you ask the right person .. you can get the specified obstacle data.

(e) So what to do? First, obtain data

And if you still don't have adequate data, you throw a theodolite over the shoulder and go bush for the time it takes to run a check survey to satisfy yourself that the data you propose to use is OK.

(f) Now, what do you want to do? Aim it and go, hoping for the best, or insist that your operator spend a few (quite a few) bucks on getting proper airport analysis and EOSID development?

This is an underlying consideration that OS, Mutt and I keeping trying to push in these sort of PPRuNe threads .. while there is no reason why a non-engineer pilot who knows the ropes can't do the work (and Tee Emm, in the previous post, is an example I could cite) the majority of pilots don't have the training or knowledge to do so. Far too often we hear tales from pilot colleagues (more so in the corporate/GA sector, but sometimes with the scheduled carriers) involving eyeballing a departure rather than doing the sums in a rational and constructive manner. It just doesn't work that way unless you are driving an F18 or similar triumph of thrust over aerodynamics .. The fact that we don't see CFITs day in day out is a reflection of aircraft engine reliability more than anything else.

Tee Emm's example is not atypical and that worthy gentleman can cite quite a few other operator instances of less than desirable policies from his very lengthy experience with a variety of airlines ...

Pugilistic Animus
11th Mar 2009, 21:50
One question???

Would one of you like to comment on the US DACS digital obstacle data? it's utility in performance engineering , sorry for the quality of this post but I MUST GO !!!


galaxy flyer
12th Mar 2009, 00:06
OS & J_T

If I may add a plug for a company in Colorado that does runway analysis for operators based on FAA AC 120-91, Runway Analysis. My employer subscribes, it is Ops Manual requirement to use them. I have found them very good, once each pilot has received training on the problem and the analysis. In the spirit of the thread, the company is A.P.G.; also available if one subscribes to brand AR Incorporated flight planning.


A Comfy Chair
12th Mar 2009, 10:24
Old Smokey -

Thank you for your "postage stamp" reply... you must have very large postage stamps where you are!

To those here who are "in the know" (ie OS, J_T, mutt etc) do you think that leaving the preparation of this data for individual airlines should be how it is done? Or should all places that provide IFR departures also have a standard EOSID published, so that everybody (crew and ATC) are on the same page when faced with the engine failure on takeoff?

As I'm sure you are aware a lot of airlines don't really put the appropriate emphasis on preparing these contingencies (whether it be through complacency or the sheer difficulty in obtaining data and accessing currently qualified individuals able to prepare these plans) so should state aviation authorities be putting more emphasis on it?

I know it would cause headaches with different airlines favouring different methods, but it seems odd to me that something that is so critical to flight safety is so widely misunderstood by pilots and inadequately considered by airlines, and that the governing bodies don't produce their own charts.

12th Mar 2009, 13:22
Or should all places ... also have a standard EOSID published

No reason why not (unless it's changed, one could cite 30 HBA as a for instance, although that's all departures ..AEO and OEI). However, the commercial reality is that one size doesn't fit all due to engine/airframe differences .. each needs to be optimised to the location if the airline is to end up with a "good" RTOW.

state aviation authorities be putting more emphasis on it?

Nice thought but an operator responsibility so I fear that few Regulators will want to get involved.

so widely misunderstood by pilots and inadequately considered by airlines

A matter of corporate will and training. I'm sure that Mutt, OS, and I have spent quite a considerable effort over the years in educating those operator crews for whom we have provided charts ... unfortunately many pilots are given minimalist training and some operators appear not to know what they don't know ...

Old Smokey
12th Mar 2009, 14:10
I wondered why I couldn't reply J_T, it seems that we were replying together!

A Comfy Chair, you've asked a very good question, one which I've discussed with one of these forums "Normal" procedure designers. I don't think that Oz_Expat would mind my re-telling some of his wise words, mixed with those (just posted) by J_T) and a few of my own.

There are far too many variables between aircraft types to create standard "Government Issue" OESIDs. Consider, for example, that the performance requirements for 2,3, and 4 engined aircraft are markedly different. A limiting obstacle for a 2 engined aircraft may require an early turn, whereas the same obstacle may not be critical for the 4 engined aircraft with it's increased climb gradient requirement and capability. To impose the increased climb requirement on the twin would limit it's payload carrying ability.

Consider also the very wide range of speeds flown by commercial aircraft. One aircraft that I do work for has a maximum V2 of 130 Kt, another has a maximum V2 approaching 180 Kt, a massive difference in turn radius, which will require different turning points for the OEISID. Hobart 30 (which I've done work for, and referred to by J_T) is a very good example. Minimum V2 has a similar effect for the "inside" splay. Again, we would be imposing another aircraft's limits on one type for the sake of uniformity, with associated penalties.

My favourite project relating to the turn radius problem was at Petropavlosk Chamkatsky (UHPP) in Eastern Russia. The OEISID requires a LARGE radius turn to contain the procedure within a "bowl" of very high mountains, but circumnavigating a large "hump" in the middle. For the B777 at the nominal OEI 15 degrees of bank at it's much higher speeds, it was a very standard calculation. For another much slower aircraft, the same very precise turn required 9 degrees of bank, a big "ask" for the operating pilots. The solution for the slower aircraft was to create precise Lat and Long for a series of FMC/FMS waypoints, and to fly the procedure using LNAV (in a non-WGS84 country).

A further problem arises due to Takeoff Thrust Time Limitations. At a very obstacle strewn airport in the land of Oz, I spent days finding the optimum escape route to avoid the obstacles, all of which required a fairly large Acceleration Altitude. The aircraft I was working for had a 5 minute Takeoff Thrust Limit, and further calculations found that the 5 minute limit would be reached just upon achieving MAA, with no excess for acceleration. After all of the work, the only solution was to impose a much higher Gradient requirement to reach MAA sooner (greatly out-climbing the obstacles), allowing for acceleration to Vcl. If a 10 minute Takeoff Thrust Limit aircraft had the same requirement imposed, again that aircraft would pay the price for complying with another aircraft's requirements.

To cut a long story short, no, one size does not fit all. There are many airports (e.g. over water) where it could, but this would be the exception.

I've recently had an email from a client who is changeing their aircraft type to one with a totally different speed range. His enquiry was "Can we continue to use the existing OEISIDs?". My reply was "We start from scratch". He hasn't replied yet!:ooh:

A damned good proposal Comfy Chair, I wish it were possible.


Old Smokey

Old Smokey
12th Mar 2009, 14:17
PS Pugilistic Animus and galaxy flyer,

Thank you both for the excellent references. Expect a PM as soon as my present 25 hours per day roster drops back to a normal frenzy.

You certainly have my interest.

P A, long long overdue email. I haven't forgotten to reply :ok:


Old Smokey

13th Mar 2009, 09:35
"Can we continue to use the existing OEISIDs?"

Our initial stab at EFP's uses a range of speeds that cover all of our aircraft, if the resulting weights are sufficient for the sectors operated from that airport, then the procedure is adopted for all aircraft, if payload isnt sufficient, then the procedure is altered for 1 aircraft type, i.e. max speed 150KIAS.

It makes life easier, especially as we operate about 12 aircraft types!


Old Smokey
14th Mar 2009, 15:55
A good proposal, as usual Mutt, and certainly achievable within one airline, albeit with 12 types. We're in a fairly similar position, with 9 types in the main airline and it's subsidiaries..

The problem arises when the system goes global, and we're trying to accomodate ALL types, from light jets through to heavy metal, 2,3, and 4 engines, 5 and 10 minute T/O Thrust limits, and widely differing operating speeds.

An example - We once chatted about Surabaya, where both of our companys fly to. The discussion was about use of Clearway, not obstacles (which aren't a particular problem there), but it's an example. If we created an "all embracing" procedure there to cover the "worst performing" type, it wouldn't worry us at all, we only have to fly 90 minutes from there to our hub, and even a hefty RTOW penalty wouldn't really matter. For you, however, with about 10 hours to destination, you'll probably be scratching for the last Kg of RTOW, and cursing the more conservative analysis for the worst case aircraft.

Perhaps the ideal compromise is to create a "Government Issue" OEISID for each runway, with individual operators reserving the right to re-develop their own procedure if the standard procedure was too limiting.:ok:


Old Smokey

Oz-Expat, where the hell are you when we need you?

galaxy flyer
14th Mar 2009, 17:22

Very good idea on standardized OEI procedures with individual operators customizing it for their particular aircraft and operation. In fact, Rio's Galeao (SBGL) did have published OEI procedures, issued by Brasil's CAA, as part of their SIDs. I planned several USAF missions out of there with MTOGW issues for C-5s and the procedures were operational advantageous. This was before we had service provider J's OEI procedures. I don't have access to a Jepp subscription at home, but will look, next I'm in the office.


15th Mar 2009, 00:15
I have a big question for you experts:

In the airtaxi ops we go all over the world with very short notice.

We are not able to estabilish contingency procedures for various reasons, AFMs are very complicated, AIPs are not available.

How can we do to have a contingency procedures available for a runway in a couple of hours ?

Can we use the SID single engine ? if gradients bigger than 3.3 is required for "noise" or "ATC" does it means that obstacles require still 3.3 ?

I have found something "web-based" but it is to have a MTOM for runway and segments, contingency procedure is only made available for some particulars situations. Another company offer the service but they require to much time.


How can I estabilish a safe procedure to come back to the airport ?

galaxy flyer
15th Mar 2009, 00:23
We use APG out of Castle Rock, CO, USA. Absolutely excellent, service is done on-line or thru Blackberry link, they can fax it and, if you subscribe to ARINC Flight Planning service, it is on their website. Analysis is done virtually immediately, in my experience over two years. Special procedures are included, if needed. They are used by charter operators, airlines and corporate flight departments.

PM, me if I can be of assistance


Danny does NOT endorse this or any other product.

To be consistent, I have removed the APG link. However, Mr Google can provide it (in an instant) for those who may be interested. - JT

15th Mar 2009, 01:01
How can we do to have a contingency procedures available for a runway in a couple of hours ?

That is the problem over which all reputable operators concern themselves. There is no easy way around the problem and all solutions cost resources both in terms of dollars and time.

There are various organisations around who will do the work for a dollar (or many) or you can train up internal resources to do the work. The difficulty is not with the actual calculations .. they are comparatively straightforward and can be done either manually or via computer. The latter requires either the OEM performance package or the development either of lookup tables or regression equations to fit the AFM data).

The routine effort has to be directed towards getting adequate obstacle data. Generally, and especially if you don't need the very last kilo, you can run up a one off calculation without too much delay .. once you have decided that your obstacle profile is of sufficient accuracy.

Can we use the SID single engine ?

Of course, provided that you match the actual obstruction profile to your aircraft's capability and accept whatever RTOWs fall out of the sausage machine. A side issue relates to imposing an increased level of precision on turning points ..

galaxy flyer
15th Mar 2009, 01:12

Can we use the SID single engine ?

I might add OS's cautions about take-off power limitations, that acceleration heights/segments on SIDs are not factored and it will probably be very limiting in most planes in most situations. Lastly, in some planes computing an accurate OEI climb gradient is not an easy trick, either.

Probably not a factor in most planes, but I (and I'll bet you, too) have flown planes that can be easily challenged at some airports in the AEO case. And I don't Aspen, Colorado only.


15th Mar 2009, 01:22
Oh dear .. appears I have been a tad lax again with my words. Perhaps I should have said something like .. one can use the SID OEI but it is no different to working out your own escape .. you still have to get all the relevant obstacle data and do all the sums and work out the limiting case for the takeoff to determine the relevant RTOW. The only advantage of the SID is that it fits in with ATC ... if may very well not give you anything like an acceptable commercial RTOW...

galaxy flyer
15th Mar 2009, 01:25

I am humbled by your reply


15th Mar 2009, 01:31
.. pity you weren't able to come over with your team .. you missed some interesting presentations ... and the dinner was fine.

galaxy flyer
15th Mar 2009, 02:37

I am sure I did!


Old Smokey
15th Mar 2009, 07:52
I'm in complete agreement with J_T, yes, you can use the normal All Engine SIDs for OEI procedures, but there is a VERY large caveat!

The SIDs are for Gross Performance, and "reverse engineering" can be applied to establish the actual obstacles considered when creating the SID, then you can apply the OEI data. First part of problem solved.:ok:

Now comes the big one. If we use the "reverse engineered" SID data for 2nd segment, what is the Minimum Acceleration Altitude (MAA)? Assuming that we are using the SID data, and nothing else, we must assume the highest obstacle to be 1000 feet below the MSA. Last night, I operated to an airport with MSA of 5500 Ft in the Takeoff area, that means the worst obstacle was 4500 Ft. A 4500 Ft highest obstacle, after applying Gross/Net corrections for OEI means a MAA of 6785 Ft, or MSA of 5500 Ft as that is a safe altitude. That is an impossible "ask" for an aircraft with even a 10 minute limitation on Takeoff thrust.

The only alternative is to establish a "OEI break off" point for the SID, so, out come the survey charts, which nobody carries in the cockpit. We're screwed.:eek:

I'm guilty of converting a few SIDs to OEI procedures, NOT as a standard procedure, but to cover that insideous situation where an early SID turn followed by an engine failure puts the aircraft in "No Man's Land". If the pilot cannot accept the SID with it's attendant RTOW penalties, then refuse it, and advise ATC of the alternative normal OEISID requirement!

As I've proposed in this and other forums, we DO need "government Issue" OEISIDs at ALL airports, even if conservative for some operators. The right to develop alternative OEISIDs must be preserved as an alternative - more work for you Oz_Expat!

I note that one of the contributors identified "J", it wasn't me your honour, "J" has a far bigger litigation budget than I do!!!!!!!!!!!!!!!

VERY IMPORTANT NOTE - A common question on these forums is "Can I use the SID following Engine Failure?" Categorically, the answer is NO, unless (except in a few safe cases) the SID is reverse engineered to FAR 25 criteria, and a suitable break-off point established:ugh::ugh::ugh:


Old Smokey

A Comfy Chair
15th Mar 2009, 13:37
Old Smokey,

I like the idea of a generic EOSID for "general" issue, reserving the right for the bigger players to also create their own more specific charts for various reasons (including payload of course!).

As a first step, however, would it be fair to say that the aerodrome operators should be required to be able to supply, quickly, the required detailed surveys that are necessary to generate the procedures?

It seems that a lot of this survey detail is just not readily available, which would certainly dissuade a smaller operator from being able to come up with plans quickly and efficiently.

Question the 2nd - Do your airlines share their E/O SIDS and procedures with the local ATC's? Obviously some places in the world its best to keep the trap shut as more info would just cause confusion, but there are plenty of ATC departments who I'm sure would be interested to know roughly what we plan to do, before we actually have to do it.

Old Smokey
15th Mar 2009, 14:09
A good response A Comfy Chair, I agree with all that you say, but the "quick" availability of the requisite data (except for Straight Ahead) is not all that easy to come by from the local authorities. The data is certainly available, but the time taken to acquire it may extend to weeks or even months, so much for "fast" data.

There's very good high quality digital data that exists for the entire planet, but the next question arises, does the regulatory authority accept it as an accurate and approved source?

When creating OEISIDs, I use all of the approved data, and then check against all other data (including non-approved Google Earth) for any other obstacles that MAY be there. Once or twice, it has paid off. Literally, you can leave no stone unturned (pun intended).

To answer your second question, yes, I do personally visit each ATC unit and brief them on our intended procedures following engine failure, leaving them with copies of the particular procedures in map form. It has surprised me when many (most) have commented that this is the first such visit that they've had, so apparently it's not common practice. (Try doing it in Russian).


Old Smokey

15th Mar 2009, 16:12
O_S and J_T,

With no intention to divert the thread, can I throw in the following:

My understanding of the meaning of paras 12.1B and 12.4 is that the planning must go to either MSA if there is no navaid or the enroute OCA (1360'?) in the safety height containment area where there is a navaid.

I also understand that AIP is only a place to publish the effect of proper legislative instruments and cannot mandate anything in its own right. Any statement in AIP about takeoff performance and obstacle clearance would only be based on the regulators view of the effect of CAO 20.7.1b or any amending instruments.

Stay Alive...

15th Mar 2009, 16:43
I'm guilty of converting a few SIDs to OEI procedures, NOT as a standard procedure, but to cover that insideous situation where an early SID turn followed by an engine failure puts the aircraft in "No Man's Land".

Always wondered about that one... When we used to use J, ZRH 28 had a SID which went left and a SE emergency turn which went right (at 400ft). Company manual said "if the engine fails while already on the SID, turn the nearest way towards SE procedure holding point". I was far from convinced that would keep us clear of obstacles! Surely we would have been better off requesting a SID which at least went it the same overall direction as the SE procedure?


galaxy flyer
15th Mar 2009, 19:00

Last night, I operated to an airport with MSA of 5500 Ft in the Takeoff area, that means the worst obstacle was 4500 Ft. A 4500 Ft highest obstacle, after applying Gross/Net corrections for OEI means a MAA of 6785 Ft, or MSA of 5500 Ft as that is a safe altitude.

While I understand Gross/Net as applied to climb gradient, could you expound on Gross/Net in regards to MAA?

Thanks, GF

Old Smokey
16th Mar 2009, 14:10

Much better that you leave that one to John_Tullamarine, he's an extraordinary engineer, but just as extraordinary in twisting the legislator's tails, something I'm not good at.


You describe the nightmare scenario. I'm well familiar with ZRH, and as I read your post I get goose bumps. ZRH is definately NOT a good place to turn in ANY safe direction following engine failure on the RWY 28 Left-Turn SID (or just about any of the ZRH SIDs for that matter). I don't want to sound as though I'm beating my own drum, but I've advocated over hundreds of posts in these forums that if SIDs are to be used - Fine, but FORMALLY establish procedures for MAA and a "break-off" point from the SID following engine failure. It's NOT difficult to do, it just costs your operator extra money. I do it for all of the "critical" SIDs that my clients use. I define critical as a turn during the SID before the aircraft has achieved a safe altitude should an engine fail after the SID turn.

galaxy flyer,

The principals involved in establishing MAA and the length of the 3rd segment are quite similar to the protocols used for Gross Vs Net performance in the 2nd segment. Using a 2 engined aircraft as the example, Gross climb gradient is estableshed by flight testing, and arbitrarily degraded by 0.8% to achieve the Net performance. (3 and 4 engined aircraft use the same principle, but the increments differ).

As an example, consider a Sea Level Runway which requires a 2.0% climb gradient to clear a 2nd segment obstacle. The aircraft should, if in new condition and flown by the Test Pilot, achieve an actual Gross Gradient of 2.8%. Therefore, the ratio of Gross to Net is 2.8 : 2.0, a factor of 1.4 (a comfortable margin).

Now, let's say that the highest obstacle in the Takeoff Area is 1000 Ft above the runway. The Net flight path need only clear this obstacle by 35 ft, not acceptable to anyone! Thus, the Minimum Acceleration Altitude (MAA or 3rd Segment Altitude) is factored in exactly the same way as was the 2nd segment glimb, i.e. 2.8 : 2.0 or 1.4. The "base" MAA will then be 1000 X 1.4 or 1400 Ft. To this is added the screen height of 35 ft (or 50 ft for a turning manoeuvre) plus the Airport elevation, yielding a MAA of 1435 ft (as we used a Sea Level Runway). If you want to put this into a long-hand formula -

MAA = Obstacle Height above the lowest point on the Runway X (Required Net Gradient + 0.8%) divided by Required Net Gradient + Screen Height + Highest Runway Elevation.

3rd Segment horizontal Distance is similarly factored. If the actual (Gross) 3rd Segment distance was, for example, 20,000 M, this is multiplied by the same factor (1.4 used here) to achieve a Net 3rd Segment distance of 20,000 X 1.4 = 28,000 M.

After all of this, you're PROBABLY still below MSA, so you'd better go lookin' for a safe place to climb to MSA. A FAR 25 principle developed "safe climb" holding pattern is this person's preferred choice here.:ok:

Sadly, there are still people "out there" who want to 'eye-ball' it!:ugh:

A personal viewpoint - The Gross Vs Net margins for the continued Takeoff following engine failure are generous. With FPA / FPV displays available on most modern aircraft, I've observed even average pilots tend to fly closer to the "Test Pilot's" Gross gradient than the Net. It lends great strength to the GO case, as the margins for Accelerate Stop are much much less.:ok:


Old Smokey

16th Mar 2009, 16:18
If I may throw in a curved ball to OS which is slightly off thread but neverthless in the same vein:

So we have lost an engine in a twin jet just after V1 at, say ZRH, we successfully negotiate the EO SID to the HP and prepare for an ILS - hopefully to our runway of choice - OEI at or just under MLW (3 changes of landing R/W in 20 mins last night at ZRH).

Unfortunately, for reasons unthinkable, we have to G/A from MDA/DA. I don't believe there are any notes on the J plates concerning min alts for level acceleration and so my Company would have me follow the standard MAP and accelerate at 1000agl

Any thoughts on that?

Cheers all

Pugilistic Animus
16th Mar 2009, 21:41
This is a very informative thread:

For further information is seemed to have made an error OS
but interestingly enough the Flight Standards Branch in the USA offers numerous digital productions for free download or on CD ROM
DACS is a different product, but the formatting is the most useful [ARINC 424] for airway/navaid dat and all referenced to WGS84 geodectic standards.

Here's the direct reference from the FAA AIM for anyone interested:

e. Digital Products.
1. The Digital Aeronautical Information CD (DAICD). The DAICD is a combination of the NAVAID Digital Data File, the Digital Chart Supplement, and the Digital Obstacle File on one Compact Disk. These three digital products are no longer sold separately. The files are updated every 56 days and are available by subscription only.
(a) The NAVAID Digital Data File. This file contains a current listing of NAVAIDs that are compatible with the National Airspace System. This file contains all NAVAIDs including ILS and its components, in the U.S., Puerto Rico, and the Virgin Islands plus bordering facilities in Canada, Mexico, and the Atlantic and Pacific areas.
(b) The Digital Obstacle File. This file describes all obstacles of interest to aviation users in the U.S., with limited coverage of the Pacific, Caribbean, Canada, and Mexico. The obstacles are assigned unique numerical identifiers, accuracy codes, and listed in order of ascending latitude within each state or area.
(c) The Digital Aeronautical Chart Supplement (DACS). The DACS is specifically designed to provide digital airspace data not otherwise readily available. The supplement includes a Change Notice for IAPFIX.dat at the mid-point between revisions. The Change Notice is available only by free download from the NACO website.
The DACS individual data files are:
ENHIGH.DAT: High altitude airways (conterminous U.S.)
ENLOW.DAT: Low altitude airways (conterminous U.S.)
IAPFIX.DAT: Selected instrument approach procedure NAVAID and fix data.
MTRFIX.DAT: Military training routes data.
ALHIGH.DAT: Alaska high altitude airways data.
ALLOW.DAT: Alaska low altitude airways data.
PR.DAT: Puerto Rico airways data.
HAWAII.DAT: Hawaii airways data.
BAHAMA.DAT: Bahamas routes data.
OCEANIC.DAT: Oceanic routes data.
STARS.DAT: Standard terminal arrivals data.
DP.DAT: Instrument departure procedures data.
LOPREF.DAT: Preferred low altitude IFR routes data.
HIPREF.DAT: Preferred high altitude IFR routes data.
ARF.DAT: Air route radar facilities data.
ASR.DAT: Airport surveillance radar facilities data.
2. The National Flight Database (NFD) (ARINC 424 [Ver 13 & 15]). The NFD is a basic digital dataset, modeled to an international standard, which can be used as a basis to support GPS navigation. Initial data elements included are: Airport and Helicopter Records, VHF and NDB Navigation aids, en route waypoints and airways. Additional data elements will be added in subsequent releases to include: departure procedures, standard terminal arrivals, and GPS/RNAV instrument approach procedures. The database is updated every 28 days. The data is available by subscription only and is distributed on CD-ROM or by ftp download.
3. Sectional Raster Aeronautical Charts (SRAC). These digital VFR charts are geo-referenced scanned images of FAA sectional charts. Additional digital data may easily be overlaid on the raster image using commonly available Geographic Information System software. Data such as weather, temporary flight restrictions, obstacles, or other geospatial data can be combined with SRAC data to support a variety of needs. Most SRACs are provided in two halves, a north side and a south side. The file resolution is 200 dots per inch and the data is 8-bit color. The data is provided as a GeoTIFF and distributed on DVD-R media. The root mean square error of the transformation will not exceed two pixels. SRACs DVDs are updated every 28 days and are available by subscription only.

MCHDU I've always wondered myself if a good OEI procedure will allow for an OEI LDG climb, in spite of the '8 sec rule for climb thrust?

The way you guys do this stuff; I don't believe is written down in any publication:ok:

'Principles and Practice,...Art Science and Technique' [ Rev. R Lacanster and T. Shimizu]

but I would not mind some assistance in aquiring the 'Boeing
engineers Book' ;)

Sorry,.... most of my posts are made on the Newest Comador 64:}


16th Mar 2009, 22:01
Thanks Old Smokey. And very interesting answer to galaxy flyer's question - definitely one for the Bookmark folder.

Now looking forward to what you have to say about mcdhu's question :ok: Been wondering about that myself...


16th Mar 2009, 23:29
Great to see that this thread has fired up a good deal of interest .. some comments ..

would it be fair to say that the aerodrome operators should be required to be able to supply, quickly, the required detailed surveys that are necessary to generate the procedures?

I suggest not. Depending on the jurisdiction, the owners will provide that which is required (and this costs someone - ultimately the operators - dollars). At present, one might see one or more of Type A (or its diminutives), Type B, Type C (I can't ever recall having seen one of these) and several other sets of OLS data. Given the variety of performance needs for a variety of aircraft Types, unless the surroundings are simple (eg a ridge or big hill and not much more) it would become a tad messy ... Probably better for the operator (or operators in conjunction/service providers) to do the work and contain the costs to the end users.

The Oz aerodrome MOS (http://www.casa.gov.au/rules/1998casr/139/139mfull.pdf) is a useful reference document for those who fancy a little light bedtime reading ..

It seems that a lot of this survey detail is just not readily available

For most places, the problems are relatively easy to determine and address. Certainly, one needs to have cultivated a range of suitable contacts for obstacle data and, on occasion, one needs to throw the theodolite over the shoulder and go forth into the hinterland .. at the end of the day it is just a matter of the will to do the work .. and this comes down to corporate risk assessment for the operator.

Do your airlines share their E/O SIDS and procedures with the local ATC's?

I believe that most don't. Some of us will make sure that any unusual escapes are notified to ATC or equivalent. Clearly, if the procedure is compatible with "normal" traffic handling, the need is somewhat less.

the meaning of paras 12.1B and 12.4 is that the planning must go to either MSA if there is no navaid or the enroute OCA (1360'?) in the safety height containment area where there is a navaid.

Oz CAO 20.7.1b (http://www.casa.gov.au/download/orders/Cao20/200701b.pdf) has always been an interesting animal. It is similar to the US 23/25-91/121 type of approach where there is a separation of airworthiness and operational standards. In the case of the Australian vehicles (historically) a few gremlins sneaked through the process with the result that we have had some discrepancies over the years.

For the younger folk who don't recall the "old" ANOs etc., the airworthiness bits were in ANO 101.5 and 6 for the heavies with the operational data in ANO 20.7.1B. 101.5/6 largely called up the relevant UK/US standards .. if we go back further to the times of ANOs which had more subordinate identifying numbers than you could poke a stick at, we would find detailed standards. These later became CAOs and, in line with the harmonisation processes, the Australian airworthiness vehicles were dumped without ceremony in the WPB ... This process has had both its good and bad points for the local Industry.

Functionally, how one implements the requirement depends on how much work you want to throw at the problem. In most cases use of declared data, such as MSA saves some time and effort.

I also understand that AIP is only a place to publish

A question for the legal folk to offer comment ...

However, it has always been understood generally that a requirement is mandated via the Act, Regs and Orders with notes and AIP providing expanded information. However, the potential risk is that, if one were to depart from an AIP "requirement", then one would need to be very certain that the requirement wasn't glued to a Reg, etc. The easier process is to adopt the AIP as mandatory .. unless the context clearly indicates an option. Just my opinion.

I was far from convinced that would keep us clear of obstacles! Surely we would have been better off requesting a SID which at least went it the same overall direction as the SE procedure?

Presuming that the operator has done the sums, then the matter should be prescribed in SOP. If SOP is a bit rubbery, then one should enquire of the operator's management what the rubbery bits really mean. At the end of the day one can always decline the SID if the concern is considered significant and reasonable.

I've observed even average pilots tend to fly closer to the "Test Pilot's" Gross gradient than the Net.

I've no problem with that observation. However, and this goes back to earlier steam driven aircraft, the then DCA's Ian C did a study (TAA, as I recall - I have no doubt that the results would have been similar elsewhere) and looked at the set of actual sim OEI tracks following failure. Some of the folk didn't track all that well. Hence my concern being more with how to make the tracking requirements easy for the pilot in anger ...

The way you guys do this stuff; I don't believe is written down in any publication

The requirements are specified (eg NFP has to be ...). The way that the regs are implemented is fairly common with the main difference being how much money an operator is prepared to throw at getting the last kilo out of the analysis.. and that, naturally, is a cost/benefit exercise.

There is no point spending a fortune getting a gold plated escape if the cheapie back of a fag packet version gave you similar RTOW data. For those of us who play with this stuff, a difficult aerodrome can cause us head scratching for several days while we play with this or that (or half a dozen more) different escape tracks ... places like Canberra and Gladstone in Oz fit this class of aerodromes ..

but I would not mind some assistance in aquiring the 'Boeing engineers Book'

Boeing Performance Engineer Training Manual (Doc D6-1420). Provided to students on the Boeing course and usually found in Mech/Aero Eng uni libraries. Excellent undergrad level text.

and so my Company would have me follow the standard MAP and accelerate at 1000agl

I can only observe that a reputable operator will have reviewed the runways and run OEI missed approach analyses similar to the takeoff analyses to get the aircraft up and away from the bumpy bits. Nothing new to this - Ansett and TAA (and, presumably, Qantas) were doing just this in the 60s for critical runways .. and spending considerable effort on the work. I think I still have a copy of one of John Walshe's studies on file somewhere ...

A big concern relates to the distance required to reconfigure to the missed approach configuration and commence the climb ...

Old Smokey
17th Mar 2009, 05:54

Only 3 runway changes in 20 minutes? You must know someone there! I was under the impression that they changed the runway direction every 5 minutes to spread the wear, the Swiss are very economical people.:O

To address your question - Most operators do NOT establish OEI missed approach procedures, they should:* As J_T says, the Australian operators did take this seriously, and I'm a product of that system.

A few points about PANS-OPS missed Approach procedures -

(1) They provide for a 2.5% Obstacle-Clear Gradient with 100 feet clearance of obstacles during the missed approach. This gradient may be higher if required, e.g. Hong Kong,

(2) A 2 engined aircraft at it's Approach Climb Limit is only required to achieve 2.1% climb gradient....... Oh dear!

There's no legislative requirement, as there is for Takeoff, for the Missed Approach with One Engine Inoperative.

There's several ways to address the problem.

First, limit your landing weight to one which will meet a 2.5% (or greater) climb gradient during missed approach (I believe that the JAA is addressing this, but am unsure if they have done so yet). In the Ops Manuals that I prepare, I throw the AFM Approach Climb data into the WPB, and re-issue "new" data for 2.5% with adjustments for those occasions when the required gradient may be higher. This should not be too difficult for the pilot to do, Approach Climb Flap is usually one of the approved Takeoff Flap settings, and data is available.

The biggest problem is the Acceleration Altitude, these are often-times very high (for ATC purposes), and you have no way of knowing if these are created for ATC or Obstacle Clearance purposes. If you want to go all the way to Missed Approach Altitude, you'll probably "bust" the 5 or 10 minute Takeoff Thrust limit. If TRULY caught out, I couldn't give a damn, these limits are created for engine life expectancy, thousands of hours down the track, and I'm far more interested in MY life expectancy.

The best of all proposals carries a SEVERE caveat. The SUGGESTION about to be made ONLY applies only to aircraft with very accurate LNAV systems, preferrably GPS/IRS. Most DEFINATELY the suggestion applies to aircraft with a DIRECT means of flying Track, NOT Heading. Here it is -

Fly the OEISID for the runway, simple, but ensure accurate Tracking of the highest order. The Takeoff splays for the OEISID on Takeoff commence at the Departure end of the Runway, the missed approach begins before the Approach end of the runway. The tolerance for straying off the RWY centre-line until passing the Departure end of the Runway (DER) is ZERO!!!! Any straying outside Runway direction puts you immediately into the mine-field of No Man's Land! One big plus, is that you are commencing the procedure already several hundred feet above the runway, as opposed to from the runway.

A good example of reverting to the OEISID for a missed approach is Hong Kong RWYs 25L and 25R. Both missed approaches make a Right turn, and take the aircraft over the most horrendouus course of obstacles, whilst the OEISID (intended for Takeoff) makes a Left turn after a suitable distance to a Southerly heading over water. You could maintain this Southerly Track all the way to the Philippines in complete comfort. In this same case, any straying off RWY centre-line (to the Left) would almost guarantee terrain impact.

Pugilistic Animus,

Expect that looooong overdue E-mail. You've certainly given me a lot more to talk about than before!

"The way you guys do this stuff; I don't believe is written down in any publication".

The mode de emploi is not written anywhere, the requirements ARE and at least CASA Australia do provide good guidance material. There's 100 ways to "skin a cat", so long as we all end up with suitably skinned cats is the bottom line (where did that stupid expression come from?)


Thanks for the link to the light reading. Being an insomnia sufferer, that contribution is a welcome addition to my E-Library. Thanks John!

I do agree with Mr. C's observations WRT average line pilot's ability to achieve "better than Net" climb performance, and agree with his concerns about lateral tracking capability. (It must have been Ansett pilots that IC was watching, TAA pilots would never do that :})Hmmm, the latter did apply in an earlier era, but in the modern day with good Track flying data capability, extended RWY centre-lines on the Map display etc., it can one day be shelved with other tomes relating to weird raw data 'happenings'. This is particularly so in our training where the trainees are hammered, "Don't just correct the swing and initial tracking error, get back on the bleedin' track!".

I'll be sorry when this thread fizzles out, I'm having fun!

I deleted Ian's surname just in case he might not want to be identified .. it probably would be crass of me to ring him to enquire .. JT

17th Mar 2009, 11:47
the Australian operators did take this seriously, and I'm a product of that system.

As am I ... which is why, I guess, we speak similar concerns and priorities.

There's no legislative requirement, as there is for Takeoff, for the Missed Approach with One Engine Inoperative.

.. but he who ignores it for critical runways may make page 3 (or page 1) of the newspapers .. depending on the number of folk killed in the ensuing CFIT

If TRULY caught out, I couldn't give a damn, these limits are created for engine life expectancy

A pertinent post from barit1 (http://www.pprune.org/tech-log/366129-toga-time-limit.html) earlier today on this very topic (post #13 in the TOGA thread)

Any straying outside Runway direction puts you immediately into the mine-field of No Man's Land!

One of the reasons we push these sort of threads is the general lack of understanding about just how tight the initial splay tracking tolerances are ..

but in the modern day with good Track flying data capability, extended RWY centre-lines on the Map display etc., it can one day be shelved

.. but, as you and I both know from sitting in back at the organ player's station ... one has to provide plenty of practice to get the message across. Hence my game of getting initial commands (in particular) to the stage where they could handle a min speed, aft CG seizure (or similar .. the blue crane bird strike programmed into the 732 in a land far away was very illustrative on this point) during the rotation flare ... with a requirement to backtrack the other end localiser .. it was always a buzz, when the pilot got to a comfortable standard, .. to say something along the lines of "oh well .. that's as hard as it gets ... guess you deserve a coffee" and watch the individual waltz out of the sim with a head twice the diameter of the shoulder width ..

The 733/4 aren't in the league of 777s and the like .. but, even then, with track up etc., it took some practice exposure for folk to get on top of the pushing and pulling needed to handle a critical takeoff failure.

Mind you .. "routine" failures thereafter rarely raised more than a bored yawn from the front seat.

17th Mar 2009, 20:36
Thank you, Old Smokey. Please can I now explore further the App/Climb Gradient with you; my queries may seem simplistic to you guys, but it seems to me that the level of knowledge out there generally leaves quite a lot to be desired!

First, the SID is built around 2.5%, but I guess that is an instantaneous figure achievable as we establish the climb at the appropriate speed and config which, it is assumed by the designer of the procedure, that we will maintain as we climb towards the Accn Alt. My question is can we expect to maintain that gradient, or will it degrade as we climb through an increment of, say, 2000'?

Next, for those of us who have a Company imposed Accn Alt below the MAP, does the 2.5% mean all the way to the MAP including the level accn or is there some (fudge) factor built in for this.

Sorry if this seems rushed and poorly explained, but am being pressurised to make way for MSN. Night all!!


Old Smokey
18th Mar 2009, 08:10

I'm by no means a PANS-OPS or TERPS "expert", I do have a good working knowledge of it because of it's relationship to other Performance areas where I am required to know a bit more.

I have put it to my employer and other clients that we should take this matter just as seriously as the Takeoff case, and fully "engineer" it. The inevitable reply is "Is it a LEGAL requirement ?" That usually ends the conversation.

If there is any commonality between FAR 25 (and equivalents) and PANS-OPS(and equivalents), and there isn't, but similar principals MAY be involved.

FAR 25 does not require the user to account for the performance degradation during the climb in 2nd segment. (I do, at the mid-point between end of 1st Segment and MAA, but that's me). The airfield elevation applies, thus, you may consider it as an INITIAL 2.5%, degrading thereafter. (Wonderful isn't it?). Even conservative Australia does not require application of QNH, which may well 'bump up' the prevailing Pressure Height by 1,000 ft or so. (Boeing DO:ok:, and so do I).

To address the second part of your question, unless an Acceleration Altitude is specified, you are required to maintain the 2.5% Gradient all the way to Missed Approach Altitude. Not having a "deep" knowledge of PANS-OPS, I don't know how long the Acceleration Segment is (if quoted), but bear in mind that OEI, this may be veeery long, anything up to 30,000 M. I doubt that this is built into the Missed Approach procedures, but I stand by to be corrected.

Pretty vague answers I'm afraid mcdhu, but guidance for your further reaearch. All will become clear when Oz_Expat emerges from his cave.:D

J_T, "I deleted Ian's surname just in case he might not want to be identified .. it probably would be crass of me to ring him to enquire .. JT". Sorry for breaking one of the cardinal rules, actually Prooners, the "C" stands for Claus, Santa Claus that is, to whom the gentleman referred to has acquired a remarkable resemblance.:}

Thanks for the cross reference to Barit1's post, nice to see that we speak the same language.

Oz_Expat, where are you when we need you? :O


Old Smokey

18th Mar 2009, 08:51
Old Smokey (and JT) - many thanks for your wisdom thus far. To draw a drinking analagy, I feel as though I am slowly emerging from a performance induced hangover as your replies help to make it all a little bit clearer each time. I look forward to Oz_Expat's input - should he surface!

It's a lovely day here in Blighty, the sun is shining and the temp has risen from 3 C when I got up to 9C now and we are told it's heading for 17!!

Cheers all,

Old Smokey
18th Mar 2009, 10:46
Don't get heat stroke mcdhu, we'd miss you!

You're not the only one getting the bad breaks you know. The Rotten Sods (otherwise known as Crew Scheduling) have sent me off for a sojourn in Bali, dusky maidens, sipping a G & T under swaying palm trees, about 28 degrees, you know the sort of lousy rosters we all have to face from time to time, but, someone's got to do the dirty work!:ok:

Might just find Oz_Expat with Greenie in hand under one of the swaying palms!


Old Smokey

galaxy flyer
18th Mar 2009, 15:47

Some guys have all the luck! I went a whole boreal (that would northern US) winter with nary a trip to the Southern Hemisphere. I did go to KMIA with a day off-15C, hot coffee, no dusky or blonde bikini-clad maidens there-mostly bundled-up, blue-haired elderly.


Pugilistic Animus
18th Mar 2009, 21:40
Hello again to all on frequency:

I believe I've read and understood everything, with some of you guys I have to revisit the thread afew times to make sure that I understand; especially as so many regulations come into play; I'm not sure if this is what is the 'basic question regarding the missed approach?

As J_T inplies: in the US we actually do have provision in the air carrier rules 121/135 etc.. for an Approach climb OEI/AEO and it is a 3.2% gradient,...this statement was not correct I confused the asummed gross gradient with net gradients ---sorry PA:O
...But we don't have provision For a 'landing climb' OEI; where the AEO-ONLY gradient is 3.3%
that's why 'I mentioned the eight second rule' to infer a critical but unlikey scenario, I mean your OIS would't extend all the way to the DER as would a critical TO OEI scenario , but surely your TO OEI procedures could be used provided you don't extend spoilers or use the reversers ..."OEI touch and GO?" :\

edited to add 'of course in proper deference to Vmcl considerations'

For those not familar wwith the FAA:

An aicraft is CERTIFIED for airworthiness [23/25/29] and then CERTIFCATED for Comercial operations [121/125/135,

.....it seems not all states follow that practice; something I just learned here:ok:


19th Mar 2009, 00:30
can we expect to maintain that gradient, or will it degrade as we climb through an increment of, say, 2000'?

Actual steady climb gradient tapers off as height increases.

A similar concern has existed for years in respect of takeoff segment gradient capability... and some AFMs are a bit better than others when it comes to working out what is what. On occasion the user has to be very careful and check at what level the chart data applies. Consider the case of an extended second segment when the AFM probably is based on a minimum climb profile .. one needs to do some iteration to match capability with requirement.

When I was starting out in the aviation sandpit, this was a hot topic in Australian ops engineering circles and there was much arm waving about performance at 35 ft and 400 ft etc., largely for the F27 and the general view was that one should meet the requirement throughout the second segment and not just at the commencement.

At the end of the day, what the rules might actually require/mean is determined by the Judge at the enquiry after the event ...

for those of us who have a Company imposed Accn Alt below the MAP,

I don't claim to be a procedures expert so the detail is best addressed by OzEx. However, the operator/pilot ought to be concerned that the actual obstacle profile is matched to the aircraft capability, including any profile/configuration changes during the miss.

"Is it a LEGAL requirement ?"

Unfortunately, that argument provides little comfort during the damages actions after the enquiry/BOI/etc. A more rational approach for an operator to adopt is to look at this in that same way as anything else .. and run a normal corporate risk assessment to determine how many dollars are reasonable to throw at getting a better answer .. considering the potential penalties associated with just winging it.

All will become clear when Oz_Expat emerges from his cave

I hope the raskols haven't caught up with him ...

Santa Claus that is, to whom the gentleman referred to has acquired a remarkable resemblance

I haven't seen Ian for a while but, if I read your comments correctly, we probably are acquiring a similar profile ... except I'm better looking, of course ... just my opinion, naturally .. he might opine to the contrary.

But we don't have provision For a 'landing climb' OEI

Nor will you; the airworthiness design standards (FAR 25 etc) require certification to address an OEI miss in the approach, and AEO in the landing configuration .. hence the ops engineering concern with transitioning from the landing configuration to the miss and the potential for the elapsed distance to impact on obstacle clearance in the case of critical runways. For the ops folk to mandate a landing configuration OEI capability would put them right out on the proverbial limb ...

surely your TO OEI procedures could be used provided you don't extend spoilers or use the reversers ..."OEI touch and GO?"

If you end up on the runway during the miss (ie Cat III type situation) things are a bit easier as the aircraft is physically located in space and the main problem is matching the actual liftoff point to the normal takeoff ie initial tracking fidelity is the concern. If the miss is all airborne, then initial tracking becomes a critical concern, not to mention height profiles during the reconfiguration period.

This is a lot easier with the fancy tracking gadgetry on later aircraft .. but consider the olden days case where we pitched up from a non-precision approach with not a whole lot of confidence as to just where we might have been over the ground (in terms of missing the hard bit two or three miles away ..) There was a lot to be said for being conservative in respect of what minimum level was used for the approach ... considering the extent to which the overshoot traversed tiger country.

An aicraft is CERTIFIED for airworthiness [23/25/29] and then CERTIFCATED for Comercial operations [121/125/135,

The terminology depends on one's view of life, death, and the Universe. Quite some years ago in Oz, Ian Mc was in the chair and he put together some very useful booklets on certification. His view was that, for a process resulting in a (Type) Certificate's being issued, the appropriate term was "certificated" for the airworthiness side of things ... of course, it doesn't really matter .. we all have a basic understanding of what the gameplan is.

Then again, I am reminded of my father's many career years in the mental health game wherein "certified" applied to those folk who went through the legal system, were so deemed, and ended up in various institutions of restricted independence .. hence I tend to use "certificated" across the board for aviation work.

Old Smokey
19th Mar 2009, 06:53
galaxy flyer,

"no dusky or blonde bikini-clad maidens there-mostly bundled-up, blue-haired elderly."

Wow!!!! Where's that? I'm 60+ now you know, the dusky maidens only laugh at the old man! What you describe sounds more like my speed!:bored:

In brief, agree with J_T about the OEI landing climb, so long as you can re-configure to at least the Missed Approach configuration. At least you should be able to avail yourself of the Takeoff splays, even with less than "state of the art" navigation systems. Landing Climb is based upon ALL engines operating in the Landing configuration. NONE of this in the regulations, but a good start for research would be your "Performance" people who have crunched the numbers for runways suitable for Touch and Go training, and applied the appropriate safety factors.


Old Smokey

19th Mar 2009, 07:26
What you describe sounds more like my speed!

If I may be permitted a little licence (even to the point of approaching a lack of PC) .. and to support my colleague's opinions ... it's a little like the proposition put to me by the wise old chap (I was still reasonably young then and all the old folk on the aircraft were, indeed, and by comparison, wise old chaps) who trained me on the 727 ... when he was a young chap, he would get all agitated, hot and bothered whenever a sweet young lass might pass by ... then, in his 40s he might glance over his lookovers at the said sweet young lass .. but contemplate the probability of her mother's being very attractive .... while, as he approached retirement ... it was a case of, through the pentafocals - looking over the lookovers, as a capability, having long been consigned to the woodheap of life .. revelling in the thought that "she must have an absolutely gorgeous grandmother" .. proving, of course, that all things are relative to the frame of reference from which one constructs one's universe and the mathematics relating thereto ....

He had some other delightful tales but I shall refrain ....

galaxy flyer
19th Mar 2009, 17:46

An worthy example of Einstein's General Theory as applied to the aviation.

Back to the thread, it was my understanding, based on old airline training, that Landing Climb was based on AEO due to the assumption that once fully configured, the aircraft was AEO and a miss would be with AEO, if it wasn't AEO, it would committed to land, hence no need for a OEI Landing Climb. That might be B727-specific.


19th Mar 2009, 22:57
Certainly not tied to any one Type. The AEO/OEI climb requirements are tied up with the certification philosophy and history .. the original explanatory words would be lost deep in the bowels of CAR 4b, I guess. Certainly, the basics haven't changed all that much in a long time. I probably have some earlier versions gathering dust in a filing cabinet somewhere but CAR 4b.119(b) and 120(d) (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgccab.nsf/0/c7b2e7d52e78a5ed86256f9d005ce447) is the earliest electronic version I can find - at 1953.

More practically, a requirement which might impose OEI capability in the landing configuration would mean we could all retire and go fishing as the payloads wouldn't impress the beancounters ...

At the end of the day, the various Design Standard climb requirements provide lines in the sand so that the aircraft on the line is reasonably likely to have a chance of getting away from the ground at whichever maximum weight is relevant to the circumstances.

(I shall consider myself ticked off for indulging in wilful and gratuitous thread creep ....)

Old Smokey
20th Mar 2009, 09:34
A simplified way of considering Landing Climb (AEO in the Landing Config) and the Approach Climb (OEI in the Missed Approach config) is to compare them to the WAT limits. Both provide a certain guarantee of aircraft performance, with no considerations whatsoever for Obstacle Clearance.

It is up to the wise operator to "marry" the two into a hopefully, harmonious relationship.

Feel free to "thread creep" all you like J_T, keep the thread alive and all that you know. Might give some time to hear Mutt's opinion of handling obstacle clearance during the missed approach, his silence is noticeable, and his opinion is, as always, worth it's weight in gold!:ok:


Old Smokey

20th Mar 2009, 10:26
Off to the sim for a 4 day stint tomorrow, but it will give me unfettered access to the Airbus performance laptop (every cloud has a silver lining!).

So if I run a landing 'inflight' perf calculation at a high GW and temp for a SL airport and run it again with the same parameters for say, MAD (elev 2000') and compare the app/clb gradient, that should give some indication of the degradation of the gradient as we climb away OEI. Presumably, though, if the OAT is below the flat rated temp for the engine (ISA+30 in my case), since the thrust will stay the same, only the small increase in TAS as we climb will account for any fall off in gradient.........

............unless you know different!!

Enjoy the weekend - if you're off!

20th Mar 2009, 14:03
OS & J_T, et, al.

I enjoyed this post immensely! I thought it was very informative and an excellent overview of OEI obstacle performance engineering. :D

If anyone is interested in a PDF copy of a certain cited performance engineering manual, please contact me off line. I also have a PDF copy of CAO AirOps Doc 7401 - Final Report on the Standing Committee on Performance, dated 1954 which is the origin of most the transport airplane performance rules.

Once again, great job!

Rich Boll
Wichita, KS

Old Smokey
20th Mar 2009, 14:45

Welcome back, it's been a long while since we last communicated, the Aspen Co exercise comes to mind. What is that damned 50 foot obstacle at the runway end by the way ?, always wondered..... (I have visions of J_T with hunting rifle and theodolite over his shoulder, suitably equipped with snow shoes and skis, wending his way along the OEISID, making due obstacle allowance for snow depth of course). (Sorry John, I couldn't resist).

Do expect a PM soon WRT the documents offered, I've already reserved some space on my new hard drive for your offering...........


It will be interesting what you observe. Damned Flat ratings, they do make a mess of conventional wisdom sometimes. One factor to consider is that, if within the Flat Rating limits, but below the maximum Pressure Height for the Flat rating, thrust can slightly increase with increasing altitude. Being a simulator, there are instances where data has been "cut to fit", and a realistic but not quite so precise results may occur.


Old Smokey

Paradise Lost
20th Mar 2009, 14:47
Me too, enjoyed it I mean, though I only understood a quarter of it!

Fundamentally it would be nice to know that in the event of one motor failing at V1 (worst case), that you would not become an unfortunate statistic, due to performance that failed to ensure clearance of the hard bits ahead.
As several non-airline bods have observed, it is often extremely difficult to obtain ANY obstacle data, thus making the calculation of required climb gradient impossible. However same authorities/aeronautical information providers were capable of surveying their airports in order to establish separation fom the hard bits on the way down, so even though they publish a required climb gradient on the way up, why could they not publish OEISIDS for different performing a/c?
Rather as there are different DAs/circling minima for different approach speeds, OEISIDs could be published for Cat A,B,C,or D V2 speeds, each giving a minimum required SE climb gradient.

I reserve the right to feel stupid depending on the ferocity of the replies. PL

Old Smokey
20th Mar 2009, 15:13
Ferocity of the replies Paradise Lost? I think not.

I believe that the general consensus expressed in this thread is that "Categorised" OEISIDs would be a good thing, a very good thing indeed!:ok:

An operation penalised by having to consider the "worst case" aircraft that may be using it, is infinitely better than no procedure at all.

I do agree with Oz_Expat's words many threads ago that it would be a huge task, but, as people like Mutt have indicated, the operator may reserve the right to independantly develop a procedure for a particular type if adversely affected.

There genuinely are numerous considerations to make, and I do not envy the people developing the various categories if this could be implemented. Many differences, even for the same performance category aircraft have been mentioned, having named a few myself, in hind-sight differences in 1st Segment Gradient and Distance would probably be the worst difference of all.


Old Smokey

galaxy flyer
20th Mar 2009, 23:01

Wow!!!! Where's that?

KMIA, Miami. It was no warmer than 16C both times I was there this winter on trips, and nary a Southern Hemisphere trip except a hard working trip to SYD, where I went to work at 3 am.


22nd Mar 2009, 21:43
that should give some indication of the degradation of the gradient as we climb away OEI.

Depends on how the software presents the data (and I have negligible background on Airbus). Unless the individual limits are specified, you may get caught with behind the scenes change in limits .. similar to obstacle limited takeoff where obstacle #1 is replaced by #2 as the critical case etc. ..

OEISIDs could be published for Cat A,B,C,or D V2 speeds

problem is cost unless the process is mandated .. and then the Fiscal Fiends will want their pound of flesh from the punters

I reserve the right to feel stupid depending on the ferocity of the replies

No-one is permitted to feel studid on Tech Log .. and ferocity is metered ... having said that .. I regularly am confronted by the limitations of my own knowledge base with many of the threads which come up on the Forum.

22nd Mar 2009, 23:55
Thanks for this outstanding discussion.

galaxy flyer
23rd Mar 2009, 01:25

Quite agree, everyone's limits of knowledge is explored on Tech Log, that's the beauty of it. Best, is that everyone (mostly, anyway) is respected and get a chance to learn from our betters. It is great that fellows like you can share the accumulated knowledge.


23rd Mar 2009, 04:50
Agree with g_f.

Awesome thread. :D:DThe muddy waters are becoming a bit clearer, again, thanks to this forum love it :ok:

Thanks all:)


24th Mar 2009, 23:17
I'm doing a short presentation on Aircraft Performance and trying to throw in some comments on where did it all came from. I've got pretty good documenttation on where much of the TO Performance came from - Specifications from TWA for what turned out to be the DC-1.

I recall reading (I think in PPRUNE) about the 35' above the takeoff surface coming from ground effect being considered to be 1/2 the wingspan and the DC-1 had a wingspan of 70'. That was a great story until I read that the wingspan of a DC-1 was 95'.

Does anyone have information on this or a link to a thread on it.

Great thread from the true Performance Gurus of the industry.

Thanks for any suggestions or information.


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