Other than being a little rude I can't see where ff has gone wrong. All he is saying is that a pilot should ensure that the A/C meets or beats the one engine out performance requirements for a departure or an arrival with a missed approach.

As to how all these requirements are developed, I don't think that was his argument.

The way i read the circular it seems that One engine out performance is considered in the missed approach.

theficklefinger's technical concerns and inferred questions were fine.

However,

(a) his comments were suggestive of a lack of detail knowledge as to how things can be done and a lack of interest in pursuing technical discussion on the same

(b) there comes a time when gratuitous insults thrown in the face of folks who are endeavouring to help out gets to the point of being a tad over the top

(c) there are other forums where such combatant behaviour is more welcome than here

Fair enough.

I got the impression that some posters were suggesting that one engine out performance was not considered when developing missed approach procedures. The way I read the posted circular suggests that it is.

Show me the error of my ways.

Thanks.

I got the impression that some posters were suggesting that one engine out performance was not considered when developing missed approach procedures

I think that's precisely what some posters were suggesting. FlightPathOBN, aterpster, and others, such as OzExpat (who hasn't spotted this thread yet) are expert in the procedures discipline and I defer to their expertise.

The OEI case is left to the airline operator and, for other operations, (quite inappropriately) the poor old pilot who has next to no real chance of figuring it out on the run.

OPS 1.510 goes some of the way to a sensible protocol but is still rather lacking, especially for the twin fraternity.

Checking the OEI gradient capability (for which configuration ?) is false comfort and doesn't consider performance capability with respect to reconfiguration during the miss.

Attempting to use the takeoff escape procedure for a miss carries with it a number of uncomfortable problems, potential and real.

For a difficult terrain runway, the only sensible way to approach the OEI problem is to have the ops eng folks do a relevant study for the miss. Any suggestion that the pilot can wing it on the day works only for benign terrain situations.

theficklefinger, having ventured into subject material in which his/her knowledge appears to be a little lacking in detail then received a bit of a friendly bollocking from the residents - goes with the territory in technical discussions and is something one needs to be able to withstand.

The post grad student has a far more intense time of it when defending his/her thesis.

Sorry JT...

It comes down to this...your either planning/recognizing for single engine performance to exceed any all obstacle and navigational aspects of your flight...or your not.

It's immaterial whether you can figure it out, or whether it's required, or whether your told to do it.

Simply put, if you can't meet Part 25 specs to fly around on one engine at any phase of flight, then you shouldn't be there.

AC No: 120-91



Gents. This tells me that OEI climb gradients are considered.

Also one can refer to FCOM 3.05.35 Approach Climb Gradient (%) to determine any odd %, other than the standard 2.5%.

What people are trying to point out to you is that Part 25 has nothing to do with TERP's/PAN OPS..... The aircraft is certified to specific Missed Approach Criteria, (all engine and one engine inop) as detailed in Part 25.

Prior to the AC, there was no FAA guidance telling airlines to do anything apart from clear all obstacles in the takeoff flight path. For Missed Approach procedures there was even less information.

I find it disappointing that the FAA have only issued an Advisory Circular, as they are there for information, you don't have to adhere to them. I would much prefer to see the word "MUST" used rather than "SHOULD". (Its the same with AC-91-6A regarding contaminated runways!)

Airbus757, even before the AC, we were reducing landing weights to comply with Missed Approach Climb Gradients in certain airports, even though this had a significant commercial impact on the operation.

Good development of the discussion in my view.

[First, for those who may not be aware, Mutt is (was ?) an ops engineering specialist (in his previous life and looked after this sort of stuff for a fairly large operation).]

Second, the problem which is being missed a little is that there are two supposedly complementary (but, often, in opposition) things in play -

(a) Design Standards - eg FAR 25

(b) Operational Standards - eg FAR 121, 135

The Design Standard gives you an aeroplane which is certificated to be compliant with a bunch of requirements and capabilities specified in the Standard. In general, however, it doesn't address much about what, when, where and how the operator might or should go about doing operational things.

The Operational Standard addresses what the Operator is required to do as a minimum.

For performance, one generally uses the data output from (a) via the AFM to figure out how to meet the requirements of (b). It helps if (a) and (b) are compatible and, while this usually is the case, one often sees the odd case of the left and right hands not knowing what the other is doing.

your either planning/recognizing for single engine performance to exceed any all obstacle and navigational aspects of your flight...or your not.

Considering OEI one should certainly be doing. The relevant question is how do you go about doing that ? FAR 25 gives you some data but not much in the way of tools. FAR 121/135 spells out some requirements but doesn't give you much in the way of how to meet them. Enter ops engineering (or those pilots who have made it their task to get up to speed on the ways of doing performance work).

It's immaterial whether you can figure it out, or whether it's required, or whether your told to do it.

I'm not sure that I understand where you are going with this comment. Figuring it out is mechanistic, requirements are in the Regulations or follow from sensible governance considerations and "told" is a combination of airmanship and corporate/regulatory governance.

Simply put, if you can't meet Part 25 specs to fly around on one engine at any phase of flight, then you shouldn't be there.

Not quite the case but near enough for government business. However, FAR 25 only gives you some data - it doesn't bridge the gap between data and not bending the aeroplane.

do not specifically require an obstacle clearance analysis ... it is appropriate to provide information to the flightcrews on the safest way to perform such a maneuver should it be required

Now I'm only a dumb PE with a bit of airline flying experience - just how does one provide information on the safest way to perform such a manoeuvre without doing some analysis ? Sounds like black magic mumbo jumbo to this little black duck.

To accomplish this, the operator may develop the methods and criteria for the analysis of one-engine-inoperative procedures which best reflect that operator’s operational procedures.

I suspect that that goobledegook means "do some analyses" ?

Generally, published missed approach procedures provide adequate terrain clearance

they left out the bit which says "for minimum terrain requirements and AEO operations"

Published missed approach has a climb gradient requirement

this might require a reduction in weight but still only is considering AEO

Departure procedure for the runway has a published minimum climb gradient

if nothing else this alerts everyone to the idea that we have some serious terrain here ..

A special one-engine-inoperative takeoff procedure is required

often this will have little to do with the missed approach ?

There are runways that are used for landing but not for takeoff

the "why ?" is important but the inference still suggests the need for a closer looksee at things.

Gents. This tells me that OEI climb gradients are considered

ah, no, not at all. Main shoot down is how do you consider OEI for twins, three holers, and quads simultaneously without specifying a lot of information ?

Also one can refer to FCOM 3.05.35 Approach Climb Gradient (%) to determine any odd %, other than the standard 2.5%.

How do you intend to account for the progressive clean up from the landing configuration to the missed approach configuration to the enroute configuration .. with varying gradient capabilities throughout ? Not to mention the hills here and there and the possible need for turns ?

Hi JT,

In my company, if the published MAP climb gradient is >2.5%, we are required to calculate the "Approach Climb Gradient" (from the lap top) using Estimated Landing weight, Airfield conditions, Landing Config. If we can't make it - then we have to use the higher published minima.

If we can satisfy the required OEI climb gradient, and we suffer an engine failure then we raise the acceleration altitude to MSA or 1st published stop Altitude or level acceleration Alt (when published).

To add a bit to mutt's comments, FAR 25 deals only with certification while Tprocedures drawn using TERPS, PANS-OPS or any national standards differing from them (unusual, granted) are designed to achieve the lowest reasonable minimums and compatibility with the ATC structure. Many procedures, especially SIDs are drawn, not to optimize payloads or to minimize climb gradients, they are drawn to meet ATC needs. The procedure designer cannot anticipate the performance characteristics of each plane using the procedure, he assumes AEO operations. It is up to the operator to plan for the engine failure case, not the designer. Meeting FAR 25 OEI climb gradients is irrelevant to DP or MAP and to achieving optimum gross weights may not happen by using the published procedure and using the published procedure may not (likely not, in many cases) provide the greatest margins in the event of OEI.

It is, in many cases, erroneous to plan meeting the specified climb gradients means the operation is being done in the safest manner. Many think planning to fly the SID or MAP using OEI performance data is best, many would be wrong.

On the airbus these figures are presented on three charts. For a missed approach we select TOGA, gear up, and move flaps up one step to conf 3, conf 2, or conf 1+F. From their respective charts we can see the expected climb gradient and as long as it is equal to or greater than the required gradient all is good. This required gradient is listed on lido charts. It is 2.5% or a non standard requirement. Also if a turn is required we must allow for 0.9%. We maintain that configuration until the missed approach altitude is reached where we level off and clean up to hold or enroute speeds.

As with most things there is more than 1 way to skin a cat. Other options are available if required gradients are not attainable.

mutt:


If AC 120-91 stated "must" or "shall" then instead of being an advisory circular, it would be a de facto amendment of F.A.R. 121.189 and related regulatory sections. The FAA cannot make rules via ACs. If they tried to do that, it would likely throw the entire issue into a "full press" rule-making process, including formal public hearings, etc. Simply put, there are marginal operators that do not wish to be bound by AC 120-91. Rather, they use a very sharp pencil to "comply" with the 600 foot wide 121.189 OEI path beyond the airport boundary.

Having said that, for benefit of the lurkers, a very good example of the missed approach case, and how it bears absolutely no relationship to FAR 121.189 is KBIH, Bishop, California. Bishop has a good RNP AR IAP to Runway 30, but Runway 12 would not qualify. So, two LNAV IAPs were developed to Runway 12, one with very low straight-in minimums for this airport and a climb-gradient missed approach, and the other with a missed approach that is 40:1 clear and, thus, with much higher minimums. These IAPs are strictly TERPs. The procedures folks who designed them know nothing about performance engineering, nor should they. They are making normal ops IAPs for every conceivable type of airplane, from a well-performing light airplane to an Airbus 320 or Boeing 767.

Low minimums with climb gradient:

http://aeronav.faa.gov/d-tpp/1108/05737RZ12.PDF

High minimums with 40:1 clear missed approach (assumes not less than 200 feet per mile CG):

http://aeronav.faa.gov/d-tpp/1108/05737RY12.PDF

As you can readily see the missed approach flight track for either of these IAPs, particulary the "Z" (low minimums) approach is very likely where the performance engineer would not want to send his airplane in the event of an engine failure at, or near, MDA. He might rather continue down the valley, where there are airspace and steeper terrain problems, nonetheless a fairly wide valley for 70 miles, or so.

What makes this airport and, in particular, Runway 12 very interesting is that IFR takeoff minimums are not authorized because of the close proximity of terrain to the D.E.R. (This issue is avoided with the IAPs by having the MAP prior to the runway threshold, plus even being at the lower MDA, you have a "running start" as opposed to an engine failure just above V1 on takeoff).

KBIH takeoff minimums (you have to scroll down a bit to located Bishop):

http://aeronav.faa.gov/d-tpp/1108/SW2TO.PDF

Now, let's say the missed approach engine failure occurs after turning east into the "merry go round" missed approach track. Do I want to continue around towards higher terrain or do I want to escape through the saddle into the valley to the east? Only performance engineering tailored to the specific airplane type can make that determination. Because engines can fail at varying points from MDA (or even prior to MDA) to infinately varying points along the missed approach flight track, is the very reason why AC 120-91 states that more than one OEI missed approach path may have to be provided for a given runway at a location as complex (terrain rich) as Bishop.

Another aspect, if the decision is to continue with the missed approach path back to BIH VOR because of an engine failure fairly late in the game, does holding have to be considered? Of course not, the holding pattern is what drives the 13,000 final altitude. Proceeding OEI up the valley to the north could result in a less demanding OEI path.

What is very apparent to the trained person is that none of this bears any relationship to TERPs, other than the performance engineer may elect to continue with the charted missed approach flight track, albeit without TERPs containment assessments.

In my considered opinion AC 120-91 should be regulatory and it should be updated to provide RNAV and even tight RNP OEI flight path options. But, this is a classic case of the "tombstone factor" at the FAA when something as critical as payload politics is involved. If the day comes when a marginal operator who does not use AC 120-91 pastes a bird on a mountain side while OEI then that would get things moving. :)

Finally, I can come up with many airports with OEI issues every bit as demanding as Bishop. And, as we know, these types of airports exist throughout the world. Latin American is rich with them.

Note: The URLs provided here will expire on August 25. But, the same charts would be available after that with a bit more searching at:

Digital Terminal Procedures/Airport Diagrams

Adding to the specifics of my Bishop message a better overview of the topography is provided by an overlay of the missed approach flight track on the 1:500,000 San Francisco visual sectional aeronautical chart:

http://tinyurl.com/3j338o9

This clearly shows the option to design the OEI flight path down the Owens Valley instead of encountering the mountains overflown in the TERPS missed approach procedure. If the engine failure occurred between MDA and PULIE, it very well may be better to have the OEI flight path depart the TERPS track at, or prior to, PULIE and continue down the valley.

Or, if the engine failure occurred well after PULIE it might be desirable to depart the TERPs track between TEVOC and NEBSE and proceed over lower terrain to the valley to the northeast.

The OEI assessment, just like a TERPs assessment, should be done on the best available topographic data. In the case of the US this is the USGS 1:24,000 topographic map. (I have found to my distress that some performance engineering entities do not use topographical data this good).

To the USGS topo map the procedures designer (for TERPs) or the performance engineer (for OEI) must plot and add all antennas or other structures of record. In the U.S. all such structures of 200' height or greater are recorded (lower heights close to the airport in accordance with the FAR 77 model).

The FAA has all of this high-fidelity and recorded structures in an automated system. And, they have all the TERPs design criteria semi-automated. Designing an OEI procedure in the U.S. would be far easier if the performance engineer had access to this FAA system (known as IAPA).

Here is a portion of the Bishop missed approach track at 1:24,000:

http://tinyurl.com/3l7jwsn

Airbus757

Yes, it is possible for a pilot to make a few spot checks of expected climb gradients in various configurations and compare them to the overall gradient required by a Missed Approach.

But doing so is not the same as a full performance analysis computed by the professional engineering entities.

As you are no doubt aware, airplanes do NOT climb along linear paths -- aka "gradients".

During climb (all engines or OEI) thrust is decaying, time limits for power settings are reached, acceleration segments are required for cleanup, etc.

Our actual climb paths are anything BUT "gradients".

Payload politics for sure...
In working with these performance profiles, it really is very difficult given the number of variants, engines, configurations, bleeds, etc that is would be difficult for the FAA to regulate how this is accomplished.
For the most part, when the carrier is shown the EO performance, it is usually a bit of a shock with the weight limits or temperature limits. Many regulators then default to EO as 'emergency operations' and let it go at that, again, thank goodness for the reliability of todays engines.

For the most part, the people back at Ops are using BCOP or something similar, to load the aircraft, with assumptions for the destination, as well as departure.
The pilot should do a quick check on approach to make sure the assumptions are close to real time conditions, namely temperature and weight, and adjust if necessary.

Here is a test example.

Input

http://operationsbasednavigation.com.../Capture03.jpg

Resultant performance...note the difference even between same aircraft type, F30 vs F40, and add icing makes a huge hit...or temps above 30.

http://operationsbasednavigation.com.../climbperf.jpg

terpster,

in answer to your very well presented case...

in regards to the OE path following the published missed, or an EO departure following anything published, 2 points...1. Cant do it the 70% answer...2. Dont even think about it.. 30%

and we suffer an engine failure then we raise the acceleration altitude to MSA

We maintain that configuration until the missed approach altitude is reached where we level off and clean up to hold or enroute speeds

That gets us out of the configuration change/gradient problem. However, given that thrust for GA generally is the same as/similar to TO, do we give any concern to time limits at GA thrust ?

Also if a turn is required we must allow for 0.9%.

Good (although a tad higher than I might have expected) but how do we account for turn radius/terrain ?

Quote:

---

and we suffer an engine failure then we raise the acceleration altitude to MSA

---

Policies like that are why a full-route OEI path is needed where radar services are not available. The MSA may be several thousand feet higher than is necessary.

rrrHow well would that method work in the example procedure provided by aterpster?

http://i202.photobucket.com/albums/a...KBIHRNAV12.png

MDA = 4580

First published altitude = 13,000

Would the company have us going all the way from 4580 to 13,000 in an approach climb configuration? :ouch::ouch:

MSA = 15,500

And as JT noted, we probably shouldn't omit to take into account the time limit at GA thrust...

:hmm: :hmm:

This plate is a basket case....

The * on MDA notes that you must climb to 11000, if able...that altitude makes sense with the controlling obstacle listed, and the mountainous ROC.

climb to 13000 direct KUPLE...this is about a 500' DA...so one goes from 4580 to 13000 for the missed? Where the heck does that come from?

3.68 GPA???? CAT C...wow...VGSI and GPA not coincident...no ****...

one has to love the FAA exempting themselves from the criteria...

FlightPathOBN:

It's a good procedure that provides access to high-performance birds that previously has not been available. It is an LNAV only procedure, thus the desent angle; this is normal TERPs. A vertically guided procedure would not qualify because of GQS problems. Otherwise, this runway would have had an RNP AR IAP.

The minimum holding altitude in that valley is 13,000 feet, thus the climb to 13,000. If there were no hold the missed approach would still have to go to 12,500 to 13,000.

Did you check the "Y" procedure for the average performing aircraft?

Obviously, this procedure is impractical for other than turbine airplane.

j.t.,

Quote:

---

and we suffer an engine failure then we raise the acceleration altitude to MSA

---

All factors in why more than one OEI route is required for a complex location, as recommened in AC 90-121.

Using the Bishop RNAV RWY 12 "Z" IAP as the case study:

1. If the engine fails at MDA the OEI path should depart the missed approach path at ROCOS and proceed down the valley on a preplanned database RNAV OEI route. Clean up would be complete at 1,500 feet with acceleration to enroute climb and a left turn out of the valley perhaps many miles later when terrain on the east side of the valley could be safety overflown.

2. If the engine failure doesn't occur until PULIE and if we are adhering to the normal ops climb gradient we are long since cleaned up, at almost 11,000 and probably 250 KIAS. So, another evaluation needs to be preplanned at that point as to whether to continue to 13,000 along the missed approach path, or depart into the adjacent valley to the east passing TEVOC.

This can be so easily accomplished with today's state-of-the-art FMS flight plan options. It has indeed been tailored into some air carriers FMS/navigation systems by the likes of Naverus.

Alas, the industry in general is way, way, behind in taking full advantage of the capabilities of their FMS/navigation system.

Sensing an engine failure, the system could offer the crew the OEI RNAV flight path options, depended upon ship's position. The required vertical profile could also be displayed at that time.

Im sorry, but I really think that banning FF was not justified at all. I read these posts, and i know that he must be very experienced and has alot to offer to this discussion. He is the reason the thread evolved to this depth. I like to keep an open mind at all times. I dont think he insulted anyone. Some peoples ego might be so high that they refuse any suggestion that they may be wrong. So you ban him because he is politically incorrect with not much finesse. I can tell that he has alot of common sense and very experienced and is quite intelligent... and you decide to ban him...

My thoughts, you have Approach Climbs requirements (1 engine inop.), you have Landing Climb requirements (all engines), both based on airport altitude. You have Missed Approach requirements which are published on the chart and based on DA or MDA. The chart might specify a gradient, and this gradient must be satisfied. My understanding is that what FF was saying is that this gradient must be MET point. If you cannot meet it because you are performing an overweight landing, or if your engine is out, or your gear is stuck down, you must find an alternate path which operations will work out for you, this alternate path might be the same as the T/O engine inop path. This is what I think FF is saying. You seemed to be all ganging up on him to tell him read this and read that, as if he is illiterate. You insulted him as much as he insulted others. BTW, please dont ban me, i meant no harm...

I really think that banning FF was not justified at all.

Your opinion is respected.

Some peoples ego might be so high that they refuse any suggestion that they may be wrong.

Not at all a problem if a poster wishes to indicate that he/she considers someone else's comments to be incorrect. If it were not for incorrect opinions sites such as PPRuNe would lose their way, I suspect.

The problem is the manner of so indicating.

BTW, please dont ban me

We don't ban folks for holding opinions.

Im not grasping it
Speaking OPS 1, is it a dispatch requirement to limit landing weight based on single engine go around performance at destination?

Thanks for your reply JT.

Some gradient requirements have to do with OBSTACLE clearance, some dont. For example Landing Climb or Approach Climb gradients dont consider obstacles. They are just gradients that must be satisfied.

However, SIDS coinsider Obstacles with a 3.3% gradient. If you cannot meet this 3.3% for ANY reasons whatsoever, you need an alternate path (the companies engine out procedure) otherwise you might fly into an obstacle.

Similarly, the Missed Approach also considers OBSTACLES in the path. If you cannot meet this gradient for ANY reasons whatsoever, you might fly into an obstacle. So whether it considers engine out or not is irrelevant. I dont understand the question. If you follow the missed approach but cannot meet the gradient for obstacle clearance you might fly into something. So yes, if you have to limit your landing weight, but most probably you would simply raise your landing minimums or follow your companies engine out procedure for that runway.

So are you actually admitting that there are correct and/or incorrect opinions ... or ... you are more interested in outcomes?

So are you actually admitting that there are correct and/or incorrect opinions ... or ... you are more interested in outcomes?

Not quite sure where you are leading.

However, all of the above. Correct/incorrect refers to factual basis for an opinion, in which case some are correct, others incorrect.

If an opinion is a value judgement, rather than a point of fact, then correct/incorrect is not the consideration, rather reasonableness and, to a large extent, that involves peer review.

.. and we should all have a directed interest in outcomes as those are what gets us to the other aerodrome in one piece or find us scattered about the hillside.

... just waiting for your correct answer! And you did ...
:ok: :ok: