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Approach Climb Gradient vs EOSID

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Approach Climb Gradient vs EOSID

Old 4th Apr 2011, 02:11
  #81 (permalink)  
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What I am having trouble with is is explaining to this forum, the plain and simple fact that TERPS and PANOPS public procedure designs are ALL engine missed

I don't think any of us have a problem with understanding that simple matter .. and that OEI remains the operator's (pilot's) problem.

you are telling me that the engines are spooled up, flaps are at Flaps 1, and you are climbing at ..

I presume you are talking 737. If a pilot couldn't do the miss and be reconfigured for the initial missed approach with GA thrust and climbing within 8 seconds ... one would be looking a bit seriously at him/her, I think.

A while since I last flew the 737 and my recollection might have faded a tad .. but why flap 1 ? My recollection is that the missed approach configuration is 15° and that 1° comes along a bit later during the climb.
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Old 4th Apr 2011, 02:31
  #82 (permalink)  
 
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Cool Apples and Oranges and Bananas

Folks,

It seems to me that there have been a lot of posts mixing up a number of concepts.

The Certification rules determine minimum installed power in an obstacle free environment - it is done by requiring minimum gradients in various configurations.

The Operating rules determine maximum allowable mass in a real world environment - it is done by requiring obstacle clearance in various configurations.

Instrument Procedure designs determine obstacle clear planes regardless of various configurations.

How does it all come together for me as a pilot: fairly simply really, because I have to obey the operating rules and that satisfies the others. The mass at which I operate must take into account the limiting obstacle clearance requirements, regardless of the particular procedure and considering contingencies, the most common of which is OEI.

If there is no procedural requirement related to obstacles, then my operating rules limit is WAT. If there are procedural limits, then I operate to a mass that allows me to follow my operating techniques and remain above the obstacle clearance plane. That mass needs to calculated by performance folks who take into account where the operating techniques place the aircraft in relation to the obstacles.

Much good work is done every day on operational take-off procedure design. Operational missed approach procedural design is much more difficult and not as commonly done due to the difficulty of establishing the actual commencement point of the climb and the related issue of keeping the operational missed approach flightpath above the Instrument Procedure obstacle clearance plane.

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Old 4th Apr 2011, 08:27
  #83 (permalink)  
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This issue is more simple that it first seems.

Generally, the procedure designer will select a missed approach that requires the minimum climb gradient.

Even where there are no obstacles in the missed approach area, the standard minimum climb gradient is 2.5%.

So with no other factors one expects that the procedure designer has already selected a missed approach routing that requires the minimum climb gradient even if this is greather than 2.5%.

However, in some cases, ATC, airspace and other issues can prevent the route of least obstacles and the actual missed approach area is designed over an area of higher obstacles.

In this case it would be possible to design a missed approach procedure for emergency purposes that avoided the higher obstacles.

This procedure could not simply be the OEI take-off route since the dimensions of that are different to a missed approach area, the obstacle clearance requirments are different and while on lift-off the aircraft will never be more than 1/2 runway from the centerline at the missed approach point it can be much further depending on navaid accuracy etc etc.
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Old 4th Apr 2011, 08:35
  #84 (permalink)  
 
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Originally Posted by 4 Dogs
Operational missed approach procedural design is much more difficult and not as commonly done due to the difficulty of establishing the actual commencement point of the climb and the related issue of keeping the operational missed approach flightpath above the Instrument Procedure obstacle clearance plane.
So it's left up to Capt and FO Bloggs to work it out themselves. How are we going to do that, given only some basic graphs in the AFM? I know that if I am below the APPR Climb weight we'll do the G/A OK, and that if I maintain at least 2.5% and follow the Missed Approach procedure I'll miss the hills by at least 100ft, the question is, just how do I work out a suitable weight to achieve that? For example, with say an MSA of 5000 ft, that's a temperature drop of 10° before I even start thinking of turns.

That's why I asked FlightPathOBN what he uses as terrain clearance parameters for his Missed Approach procedures.

Alternatively, here was I thinking that RNP approaches and their Missed Approaches would provide adequate terrain clearance OEI. Perhaps that is not the case.
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Old 4th Apr 2011, 08:44
  #85 (permalink)  
 
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OEI G/A transition

Originally Posted by John Tullamarine
If a pilot couldn't do the miss and be reconfigured for the initial missed approach with GA thrust and climbing within 8 seconds ...
It's not quite so simple. In rules that have been discussed in rule making circles, the critical engine is assumed to fail at the initiation of go-around. The relation between Vref and the stall speed in the approach configuration permits immediate retraction of flaps by one notch. According to the rule makers, retraction of the undercarriage must wait until the airplane has achieved a steady rate of climb of 100 ft/min, at Vref, approach flap, gear down, one engine inoperative. A tough nut to crack in 8 seconds. The U/C then needs another 5-7 seconds to retract.

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Last edited by HazelNuts39; 4th Apr 2011 at 11:41. Reason: text in italics added
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Old 4th Apr 2011, 09:37
  #86 (permalink)  
 
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DFC:

In this case it would be possible to design a missed approach procedure for emergency purposes that avoided the higher obstacles.
That certainly could be done at some locations. But, where the published missed approach is 40:1-clear (2.5% clear) what would be the point?

And, unlike OEI contingency procedures, any alternate missed approach would have to have full TERPs or PANS-OPs lateral containment areas. And, unlike any OEI contingency procedure, the alternate missed approach would have to be accepted by the approving authority.
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Old 4th Apr 2011, 10:40
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5 pages

.......5 pages.....86th replies...
seems like alot of different opinion....who has the correct answer....my poor brain can't handle this much info
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Old 4th Apr 2011, 21:54
  #88 (permalink)  
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That certainly could be done at some locations. But, where the published missed approach is 40:1-clear (2.5% clear) what would be the point?

And, unlike OEI contingency procedures, any alternate missed approach would have to have full TERPs or PANS-OPs lateral containment areas. And, unlike any OEI contingency procedure, the alternate missed approach would have to be accepted by the approving authority.
If the lowest minima are based on a 2.5% missed approach gradient then there is no need to do any more work. If however, there are minima provided for the 2.5% missed approach and lower minima provided for aircraft that can acheive a higher missed approach gradient, there may be something to be gained by revisiting the missed approach design with a few to making the route over more favourable terrain or even tailoring the procedure for example to the specific aircraft type that will be used (it might be at the lower end of the C/D speed range for example.

Yes indeed the alternative missed approach would have to meet all the PANS-OPS or TERPS criteria and not only that but when the publsihed missed approach involves a significant turn, one has to consider the posibility of an engine failure during or just after the turn perhaps when the aircraft has now turned towards the significant obstacles.

As far as obtaining authority approval, there would be no difference between this alternative OEI missed approach and the OEI departure. They are acheiving the exact same thing at different stages of the flight - allowing higher operating weights or in some cases operation in cases which would be impossible otherwise. Provided that the design is correct and the numbers work then safety is ensured.
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Old 4th Apr 2011, 23:30
  #89 (permalink)  
 
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Too many questions!

That's why I asked FlightPathOBN what he uses as terrain clearance parameters for his Missed Approach procedures.

Alternatively, here was I thinking that RNP approaches and their Missed Approaches would provide adequate terrain clearance OEI. Perhaps that is not the case.
For standard missed approach, the TERPS/ PansOps criteria.

For RNP, 8260.52, the standard missed approach is all engine. The criteria are based on the following assumptions: (page 4-1 8260.52)
• Aircraft climb at a rate of at least 200 ft/NM (3.29%) in the missed
approach segment.
• A 50-ft height loss is inherent in MA initiation.
The standard MA construction is a continuation of the final approach course. The OEA expands at a 15° splay from the FAS RNP value to a value of 1.0, using a 40:1 OCS slope ratio. Missed approach RF turns that are speed limited must limit bank angles to 15° maximum.

For RNP EO missed, this is a custom design that looks at all segments, with emphasis on turns/bank angles.
OCH determination. 4.7.2.1 First, determine the height of the highest approach obstacle penetrating the final approach OAS or the horizontal plane from Dveb to the origin of the Z surface.
4.7.2.2 Next, reduce the heights of all missed approach obstacles to the height of equivalent approach obstacles by the formula given below:
ha = [(hma*cot Z) - (XZ-X)]/(cot VPA+cot Z)
where:
ha = height of the equivalent approach obstacle
hma = height of the missed approach obstacle
cot Z = cotangent of the Z surface angle
cot VPA = cotangent of the VPA
XZ = origin of the missed approach surface (Z) relative to LTP (Fictitious LTP if appropriate). It is
positive before the LTP/FTP and negative after.
X = Obstacle distance from threshold
and
Missed Approach MOC is:
50 m (164 ft) (Cat H, 40 m (132 ft)) for turns more than 15 degrees and
30 m (98 ft) for turns 15 degrees or less
and a few other borish calcs...

RNP EO procedures are sim and flight checked. THE EO tracks in RNP will be on the specific operators approach charts. Here is a generic example (page 8)

According to the rule makers, retraction of the undercarriage must wait until the airplane has achieved a steady rate of climb of 100 ft/min, at Vref, approach flap, gear down, one engine inoperative. A tough nut to crack in 8 seconds. The U/C then needs another 5-7 seconds to retract.
Hence the AC120...

"EOPs are NOT TERPS Or PANS-OPS Criteria
EOPs Do Not Provide Takeoff Data
EOPs Do Not Provide Standard ATC Departure
EOPs Are Not Developed or “Flight Checked”
EOPs Are Not Promulgated Under CFR Part 97
EOPs Are Not “Approved” By The FAA they Are “Accepted”
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Old 5th Apr 2011, 00:41
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A tough nut to crack in 8 seconds. The U/C then needs another 5-7 seconds to retract.
You think 8 seconds is tough, look what the criteria thinks you do...



Turn this into an MDA....
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Old 5th Apr 2011, 16:47
  #91 (permalink)  
 
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The DA/MDA on the plates is based on a very simple concept. You decide to go missed, and 8 seconds later, the aircraft climbs at 2.5%. This is the basis for the 'level' section. The 8 seconds takes into account the decision and aircraft reaction time. Again, you are at flaps 30 or 40, idle descent, around 140kts...and in 8 seconds, you are telling me that the engines are spooled up, flaps are at Flaps 1, and you are climbing at 2.5%? This is what the obstacle clearance surfaces are based on.
Although certification standards require this it's usually SOP to be spooled up to approach thrust settings

"EOPs are NOT TERPS Or PANS-OPS Criteria
EOPs Do Not Provide Takeoff Data
EOPs Do Not Provide Standard ATC Departure
EOPs Are Not Developed or “Flight Checked”
EOPs Are Not Promulgated Under CFR Part 97
EOPs Are Not “Approved” By The FAA they Are “Accepted”
but again from AC -120 those contraventions are speaking about SIDS and DPs...what about approaches?...that diagram [from what I understand] shows that from the MAP a gradient 200' nm -3.3% must maintained above the obstacle clearance plane [dotted line segement? - if that is the technically correct term-but at lower gradient it's seems you'd still have clearance-to get around the obstacles...for the various engine numbers---while you don't get the full protection of an assumed 3.3% gradient. it seems the FAR 25 provisions still allow obstacle clearance-as long as WAT allows for certificated gradients?
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Old 5th Apr 2011, 17:40
  #92 (permalink)  
 
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PA,

When you say at approach thrust settings, Vref is thrust 0, which is the SOP setting that you are talking about? There is the FOQUA...

For obstacle protection, its best to look at the different standards. There is the Part 77 surfaces and the ICAO stds, and if the aerodrome is certified.
This means that the agency is active in surveying and maintaining the obstacle surfaces.

The various P77 surfaces range from 2%, 2.9% and 5% in various distances and configs from the runway endpoints. There is also the blanket requirement for all structures over 200' tall to be submitted to the FAA for eval, but this is little enforced.
What is interesting is the P77 looks at the approach surface, but little for the missed.


NOAA source

To be clear, that diagram from the other post is from 8260.52, RNP....illustrating one method to avoid an obstacle by raising CG. Getting this approved is virtually impossible.

A better diagram is the figure 4.2, which the basic MA OCS.

Last edited by FlightPathOBN; 5th Apr 2011 at 17:55. Reason: add MA
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Old 5th Apr 2011, 18:05
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The following civil airport imaginary surfaces are established with relation to the airport and to each runway. The size of each such imaginary surface is based on the category of each runway according to the type of approach available or planned for that runway. The slope and dimensions of the approach surface applied to each end of a runway are determined by the most precise approach procedure existing or planned for that runway end.
(a) Horizontal surface. A horizontal plane 150 feet above the established airport elevation, the perimeter of which is constructed by SW.inging arcs of a specified radii from the center of each end of the primary surface of each runway of each airport and connecting the adjacent arcs by lines tangent to those arcs. The radius of each arc is:
(1) 5,000 feet for all runways designated as utility or visual;
(2) 10,000 feet for all other runways. The radius of the arc specified for each end of a runway will have the same arithmetical value. That value will be the highest determined for either end of the runway. When a 5,000-foot arc is encompassed by tangents connecting two adjacent 10,000-foot arcs, the 5,000-foot arc shall be disregarded on the construction of the perimeter of the horizontal surface.
(b) Conical surface. A surface extending outward and upward from the periphery of the horizontal surface at a slope of 20 to 1 for a horizontal distance of 4,000 feet.
(c) Primary surface. A surface longitudinally centered on a runway. When the runway has a specially prepared hard surface, the primary surface extends 200 feet beyond each end of that runway; but when the runway has no specially prepared hard surface, the primary surface ends at each end of that runway. The elevation of any point on the primary surface is the same as the elevation of the nearest point on the runway centerline. The width of the primary surface is:
(1) 250 feet for utility runways having only visual approaches.
(2) 500 feet for utility runways having non-precision instrument approaches.
(3) For other than utility runways, the width is:
(i) 500 feet for visual runways having only visual approaches.
(ii) 500 feet for non-precision instrument runways having visibility minimums greater than three-fourths statue mile.
(iii) 1,000 feet for a non-precision instrument runway having a non-precision instrument approach with visibility minimums as low as three-fourths of a statute mile, and for precision instrument runways.
(iv) The width of the primary surface of a runway will be that width prescribed in this section for the most precise approach existing or planned for either end of that runway.
(d) Approach surface. A surface longitudinally centered on the extended runway centerline and extending outward and upward from each end of the primary surface. An approach surface is applied to each end of each runway based upon the type of approach available or planned for that runway end.
(1) The inner edge of the approach surface is the same width as the primary surface and it expands uniformly to a width of:
(i) 1,250 feet for that end of a utility runway with only visual approaches;
(ii) 1,500 feet for that end of a runway other than a utility runway with only visual approaches;
(iii) 2,000 feet for that end of a utility runway with a non-precision instrument approach;
(iv) 3,500 feet for that end of a non-precision instrument runway other than utility, having visibility minimums greater that three-fourths of a statute mile;
(v) 4,000 feet for that end of a non-precision instrument runway, other than utility, having a non-precision instrument approach with visibility minimums as low as three-fourths statute mile; and
(vi) 16,000 feet for precision instrument runways.
(2) The approach surface extends for a horizontal distance of:
(i) 5,000 feet at a slope of 20 to 1 for all utility and visual runways;
(ii) 10,000 feet at a slope of 34 to 1 for all non-precision instrument runways other than utility; and
(iii) 10,000 feet at a slope of 50 to 1 with an additional 40,000 feet at a slope of 40 to 1 for all precision instrument runways.
(3) The outer width of an approach surface to an end of a runway will be that width prescribed in this subsection for the most precise approach existing or planned for that runway end.
(e) Transitional surface. These surfaces extend outward and upward at right angles to the runway centerline and the runway centerline extended at a slope of 7 to 1 from the sides of the primary surface and from the sides of the approach surfaces. Transitional surfaces for those portions of the precision approach surface which project through and beyond the limits of the conical surface, extend a distance of 5,000 feet measured horizontally from the edge of the approach surface and at right angles to the runway centerline.


PA,

When you say at approach thrust settings, Vref is thrust 0, which is the SOP setting that you are talking about? There is the FOQUA...
Approach thrust settings allow for rapid engine acceleration to GA thrust ---SOP ususally have a minimum altitude for having the engines spooled...in readiness-it's not a good idea in general to be at idle setting so low down---could mean windshear as one possibility...if speed chasing requires an idle setting or for that matter a very high setting---

the designer's assumption is evaluated for the worst case it seems-as would be good enginering practice anyway...but

even with plane at a lower gradient must not the aircraft flying the MA in question maintain -A FAR 25 specified gradient above that OCP? and that in this case [like second climb segment info] the ability to maintain far 25 gradient is implicit in 121/135 operations
hence would not meeting FAR 25 standards automatically qualify for 121 operating procedures...obviously far 25 allows a lower gradient than AEO over the OCP but the MAP OCP allows for 121 operators to perform at the minimum specifies gradients using the nornal IAP MA

I can't see how TERPS and FAR 25 /121 can be so diverged?
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Old 5th Apr 2011, 18:29
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Approach thrust settings allow for rapid engine acceleration to GA thrust ---SOP ususally have a minimum altitude for having the engines spooled...in readiness-it's not a good idea in general to be at idle setting so low down
Concur. This is why I have issues with the criteria speeds for each class of aircraft for the final approach segment.

the designer's assumption is evaluated for the worst case it seems-as would be good enginering practice anyway
Exactly. in design, if you take the worst case for the missed, the airport alt, highest temp for that airport, max weight, all the bleeds, etc...you use this CG for the EO missed. In my experience, for a twin, this is less than 2.5%. For RNP, this means doing obstacle surveys for the MA corridor.

As you can see, there is little the P77 survey does for the missed..the OCS is 2.5%, so if your climb is at 2.5%, you have no ROC.

I can't see how TERPS and FAR 25 /121 can be so diverged?
Good comment! When you look through and try to design procedures to meet all of the applicable rules, you find many conflicts. The FAA exempts themselves on the rules when designing procedures, but unless you are able to dig into the 8260 forms, you dont know what they have exempted.
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Old 5th Apr 2011, 19:04
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FlightPathOBN:

From your Post #92:

To be clear, that diagram from the other post is from 8260.52, RNP....illustrating one method to avoid an obstacle by raising CG. Getting this approved is virtually impossible.
The FAA the RNP AR procedures designers routinely use climb gradient missed approach procedure, and more than a few to the max of 425 feet per mile. No approval is required because it is permitted by Chapter 4 of 8260.52.

And, from your Post #94:

Good comment! When you look through and try to design procedures to meet all of the applicable rules, you find many conflicts. The FAA exempts themselves on the rules when designing procedures, but unless you are able to dig into the 8260 forms, you dont know what they have exempted.
I peruse IAPs of interest to my organization when they are in coordination. There are occasionally Flight Procedures Standards Waivers, but they are relatively few, and must document an equivalent level of safety (provided for in 8260.3B). I know of no "exemptions," though.
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Old 5th Apr 2011, 19:11
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wouldn't then you then be following the OCP gradient exactly that's not a zero ROC


---the operator has to worry about such things as bleeds as that would be detailed performance data...not applicable to the procedure design...only if the expectaion is similar to flying above the NTOFP...a protection that can't be had generically in the IAP criteria-the operator is responsible for assuring that the airplane meets FAR 25 WAT limits ...and that a minimum gradient can be maintained.
one can not have the same luxuries as the gross vs NTOFP--in determining the minims w/o writing expensive special procedures just for an extremely rare WAT limiting case

Last edited by Pugilistic Animus; 5th Apr 2011 at 19:32. Reason: replace DP/SID with IAP bold
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Old 5th Apr 2011, 19:15
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Pugilistic Animus:

You cite FAR 77 surfaces, which are only for the purpose of providing guidance to proponents when they must file under FAR 77. If they fail to do so, the FAA has zero enforcement options. If, however, it is a transmitter tower that requires an FCC license, if the FAA notifies the FCC, then the FCC will not issue a transmitter license.

If it is a building, often the insurance company has the real clout when a proponent either fails to file when required by Part 77, or when the proponent does file but ignores a Determination of Hazard by the FAA.
A proponent with deep pockets can choose to flight a hazard determination under the Part 77 appeals process. That can become quite interesting. It is far more productive for the proponent to enter into negotiations with the regional FAA office to turn a hazard determination into a no hazard determination.

I can't see how TERPS and FAR 25 /121 can be so diverged?
TERPs does not, and cannot, account for OEI surfaces. That would require accounting for the lowest common denominator, which would make TERPs procedures useless for the 99.9% of the time when operations are normal.
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Old 5th Apr 2011, 19:19
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I think it's the converse that applies according to the post in this thread part 121 and 25...account for TERPS limitations...


we are such nerds...
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Old 5th Apr 2011, 19:50
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The FAA the RNP AR procedures designers routinely use climb gradient missed approach procedure, and more than a few to the max of 425 feet per mile. No approval is required because it is permitted by Chapter 4 of 8260.52.
Yes you can, with 'specials', but I have not seen this with public RNP, at least with 3rd party developers, I have noted specific CG on a few plates, but very few. Without waivers, a design based solely on the published criteria would useless...18 degree max bank angle with winds being my favorite.

by 'exemptions' I did mean wavers...sorry 'bout that.

TERPs does not, and cannot, account for OEI surfaces.
Exactly my point throughout this entire thread.

Operator Training Concerning One Engine Inoperative Contingency Planning For IFR Departure Procedures.

FAA has zero enforcement options
Actually, the FAA does have some teeth in these regards..at Palm Springs, several wind turbines were relocated, but yes, you are correct, there is little pro-active enforcement, and with RNP, you are typically outside of the P77 surfaces, so you are on your own.
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Old 5th Apr 2011, 19:54
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but the operator had better meet them gradients OEI...
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