Missed Approach Climb gradient and missed approach requirements

[zxccxz]

Missed approach (standard) requirement, taken from pans ops 8168 vol.2 : 2.5%

http://s12.postimage.org/wifrw3lv1/image.jpg

Missed Approach Climb gradient single engine = 2.1% (twin engine)


Question: If you go around single engine and follow the published Missed Approach (2.5% gradient), you will fly below it (2.1%)--> You could hit an obstacle!

Am I missing something?

[aterpster]

You are correct. That's why savvy operators have performance engineers assess the obstacle environment for each authorized runway end and provide one engine inoperative "escape" flight paths, where necessary.

There are other locations where a 1% gradient (or even less) will clear all obstacles on a missed approach.

[G-IZMO]

Looking at the text in the Aerad supplement that reproduces this diagram, it states:

"It must be emphasised that not all aircraft can achieve this gradient with an engine out, at a maximum certified gross weight. This 2.5% gradient is assumed to extend up to a point at which the aircraft can fly level for 6nms to accelerate and clean up."

So in essence, the answer would be that you could hit something.

I looked at a couple of example charts also from Aerad, which has a MISAP towards a big hill. These give tracks to clear the terrain but do not provide % climb gradient required for the MISAP. Therefore it would fall into the 'operator responsibility' per EU Ops.

Trying to find the definition of what calculations are done for max landing weight by our performance service provider. I suspect that it is weight limit for factored LDA, and also the landing climb, but right now I cannot recall if landing climb is done OEI or not. I suspect not, as it'll be weight to achieve the required % per the certification requirements.

Does your FMS provide the climb % gradient available at your landing weight? That gives you a warm feeling of what the aircraft will do with OEI.

[G-IZMO]

Ops 1.510

"For instrument approaches with a missed approach gradient greater than 2,5 % an operator shall verify that the expected landing mass of the aeroplane allows a missed approach with a climb gradient equal to or greater than the applicable missed approach gradient in the one-engine inoperative missed approach configuration and speed (see applicable requirements on certification of large aeroplanes). The use of an alternative method must be approved by the Authority."

[OPEN DES]

We're mixing things here. 2.1% is a certification req as per EASA CS-25.
Operationally we should comply with EU-OPS and PANS OPS doc 8168 which prescribes 2.5% as procedure design gradient unless otherwise noted.
The requirement is always for One Engine Inoperative.
Note that from PANS OPS revision 4 onwards the level acceleration segment (6nm@800ft HAA I believe) has been deleted. This means now that 2.5% gradient must be assured OEI until MSA/go around altitude. I.e OEI acceleration must be delayed...
Some states such as France have, despite having constructed i.a.w. PANS OPS 4/5, catered for a level acceleration segment i.a.w. chart note. E.g. No level accel prior to xxxx ft.


Rgds

[9.G]

The requirement is always for One Engine Inoperative. Any IAP is laid out for normal configuration e.g. all engines operating. It's an operators' responsibility to cater for contingencies. Having said that, a twin on STD ISA can achieve on average 5% climb gradient with MLW but for the acceleration segment has been deleted, following published MA SE till MSA or the MA level off alt. might or might not be possible. :ok:

[OPEN DES]

Yes you're right. What I was getting at is that very few operators consider an OEI routing in missed app. Hence the PDG of 2.5% has to be complied with OEI in these cases.

Atb

[zxccxz]

Thanks guys, really appreciate the responses!
merry xmas :)

[nick14]

As a 737-800 operator we have accounted for all this although its based on an MFRA at roughly 1000 aal. Under the new rules are we now saying that we we have to climb at T/O flap to MSA OEI? That's going to interesting in the summer....

[FlightPathOBN]

original post states EO climb is 2.1%..

2.5% is gross
2.1% is net

all engine....

[Fullblast]

original post states EO climb is 2.1%..

2.5% is gross
2.1% is net

all engine....

So technically you shouldn't have any problem, as long as you go-around at or before minima, if you do after, for whatever reason, it might be a serious problem.

FB

[de facto]

So technically you shouldn't have any problem, as long as you go-around at or before minima, if you do after, for whatever reason, it might be a serious problem.

It might be if you didnt check your go around climb gradient capability in case of engine fail before starting the approach.
If you started an approach with your actual gradient (one engine toga and flaps in GA position) below the required gradient you are not legal and Yes If you need to GA and then lose engine as you do so,you are in serious:mad:

I believe there is a 3.2% balked landing gradient (2engines/twin) that must be statisfied also.(speed VREF,gear down,both engines toga).

[FlightPathOBN]

During actual flight testing of engine out procedures, it was interesting to note just how difficult it is to make the climb and not violate the missed approach surface, especially if you are configured for landing, and near the 140kts CAT C speed....

[italia458]

Any IAP is laid out for normal configuration e.g. all engines operating.

Yes, they say that but it doesn't mean anything. If you can maintain the minimum missed approach climb gradient then that's all that matters. It doesn't matter if you've lost one engine or two engines or you're flying a rocket or you fire a cannonball - the object (whatever it is and whatever happens to be propelling it at the time) will not hit any ground object if it can maintain the minimum missed approach climb gradient.

The only reason a designer will say that it's only laid out for normal operation of the airplane is so that they cover their ass for whatever litigation they might encounter from an incompetent company or pilot who decides to sue because it didn't say on the plate that they should double check their performance if they want to attempt the approach single engine.

[WildCatFromWildBush]

2.1% is minimum certification (CS/FAR/AP-25) value. For instrumental approach according to 8168 you have to have 2.5%. If there are some significant obstacles, ACG should be bigger, than 2.5%. However MDA(H) must be povided for ACG = 2.5% as well as for bigger one. No gross/net flight path definitions for approach path as well as for other flight phases, describes in 8168. "Net" for abnormal (engine-out) only.

[aterpster]

I think we have been through this more than once in other threads.

A departure or missed approach climb gradient is a constant slope.

A OEI takeoff or missed approach path is a "staircase."

Only a performance engineer can determine whether the "staircase" will fall below the constant slope of normal IFR departure or missed approach procedures.

[FlightPathOBN]

Well, one has to remember, that a procedure design, has to take into account all of the worst case factors...
MLW, max bleeds, dirty engine, low end of the CAT approach speed, initiation of missed, pilot/aircraft reaction time...and especially temperature/met conditions.

The plates will likely have one missed approach shown for all CATS as well...

From a design engineer perspective, considering all of the above factors, I find that few twins meet the missed approach climb requirements when EO....

even during actual flight tests of procedures, with an engine at idle to sim EO, it was creative not to violate to missed approach surface (unless you wanted to design an unreasonable DA/MDA...)

If the plates had EO taken into account, you would see some very unreasonable DA/MDA's...if the DA/MDA is near the 200' OCH, ie 250HAT (200' OCH + 50' momentary descent) I would really see little chance of an EO twin not extending into the OCS...

Note the origin (original post) of the missed approach surface..it is NOT end of runway, it is TCH....

[italia458]

Well, one has to remember, that a procedure design, has to take into account all of the worst case factors...
MLW, max bleeds, dirty engine, low end of the CAT approach speed, initiation of missed, pilot/aircraft reaction time...and especially temperature/met conditions.

FlightPath...

Procedure design has nothing to do with how an airplane is flown. As I mentioned in my earlier post, it doesn't matter if the plane is being flown on 1 engine or 8 engines, as long as it can maintain the minimum climb gradient and carries out the proper rate one turns and maintains the airplane within the allocated distances associated with the category, the airplane will be safe!

One quick point before moving on: categories (A, B, C, D, E) are based on indicated airspeeds. You are supposed to fly according to the minima associated with the category in which you're flying the maneuver at. For example: if you're flying a circling procedure at 140 KIAS then you're supposed to adhere to Cat C minima and the circling distance of 1.7NM. But, I think it should be understood that it does not matter what airspeed you fly your maneuver at, if you maintain within the limits prescribed for that category, you will be safe. If you fly 300 KIAS while circling and keep it within 1.3NM then you could go to category A minima and be safe. If you're flying at 140 KIAS while circling but would like some extra room to maneuver, you may go to the category D minima and keep it within 2.3NM instead of the 1.7NM for category C.

I think it needs to be remembered that there is a HUGE difference between procedure design and airplane performance.

As for the determination of procedure design, there are certain factors for wind and imperfect turning that is applied to the flight path to ensure protection up to a certain limit. The worst case is not the low end of the category approach speed, it is the high end. If you're at the high end you will require a greater turning radius thus requiring larger protection limits while maneuvering. I agree that they they add a fudge factor for pilot/aircraft reaction time, and temperature/met conditions such as wind - however, I don't agree any consideration is taken for MLW, max bleeds, dirty engine, etc. Those are all specific airplane performance factors.

[9.G]

a modern twin in EO condition and ISA with MLW will achieve on average 5% MA climb gradient. :ok:

[FlightPathOBN]

a huge difference between a procedure design and performance?

I would think they are directly related.

I have worked out many, many missed approach performance profiles, for all kinds of aircraft, in all kinds of conditions, trying to balance weights, airport altitude, and temperature limitations...

on procedures, you get calls all of the time when the temperatures go up...

9.g..perhaps 5% eventually....I would not count on a 5% climb EO at the missed approach point, and the momentary descent EO is significant...

[italia458]

FlightPath...

Of course a procedure is designed to accommodate aircraft but the point I'm trying to make is that it's incorrect to say that a procedure was designed for an airplane operating on all engines and therefore not designed for an airplane operating OEI.

A procedure is designed with certain performance requirements. If an aircraft can meet those performance requirements then it can safely follow the procedure. It doesn't matter how the aircraft attains that performance!

[FlightPathOBN]

Well, a matter of semantics I suppose. I also understand there is reality, and one reality is that very few pilots would have a level-off section in the EO missed profile...that is again, the worst case scenario...


The FAA is quite clear that the missed approach procedure is all engine, classifies EO as non-normal operations, and leaves engine out procedures to the operator.


There are many airports where there is a missed approach procedure, and EO is specifically not allowed...the aircraft must divert.

Balked operations are completely different....

[737Jock]

During actual flight testing of engine out procedures, it was interesting to note just how difficult it is to make the climb and not violate the missed approach surface, especially if you are configured for landing, and near the 140kts CAT C speed....

5% at 140kts groundspeed is about 710ft/min. This might be a struggle in hot conditions high elevation and high weight.
2,5% is about 355ft/min at 140 kts.

Sorry but I really don't believe that most twins will struggle with 2,5% in reasonable conditions.

Offcourse as a performance engineer you will be presented with the difficult cases, probably the usual suspects. But on most airports I suggest that twins can easily handle 2,5% EO.
I haven't seen anything from our performance calculations LPC NG (A319/A320), that suggests otherwise.

And offcourse there are techniques to create a higher actual gradient: lower flap setting for landing (less drag in missed approach climb config) and a higher approach speed (more energy to start with)

[9.G]

737, the problem is that that 2,5% or whatever is required has to be maintained till MSA or MA level off altitude/level whichever comes first due to the fact that the level off segment has been deleted from the latest PANS OPS version. That puts a limitation on TOGA thrust usage even if the climb gradient is satisfied. So both criterion must be achieved GA climb gradient and duration of TOGA usage to be able to reach the necessary alt/lvl accelerate, clean up and ONLY then reduce thrust. That's where the performance dep. comes in and determines this threshold temp until which following the published GA is OK above which SE dep. must be followed. that's all at or above the mins below the mins (balked landing) the only choice left is to follow SE dep. :ok:

[FlightPathOBN]

737..

Well, that is also the case...most missed approach procedures are along the lines of straight ahead until 2500 or such...I would not get involved unless it didnt really really work, but the people loading up the ac will look at all of these factors for the destination airport anyways...
. As stated before, the criteria does not address EO missed, so one has to rely on 3rd party developers to sort out performance issues.
Think of the public missed...you have 737's out there with 20K engines, all the bleeds, MLW, and its 90 degrees out...then go EO....

My perspective is from RNP procedures, which must take into account the worst case setting for the aircraft, and typically the missed procedure for EO is the straight section, then the all engine missed has the turns...
That is why there are very specific procedures for different variants of the 737 family and many of those will not work with the A320 family.

Get calls all the time, especially from AUS, when the temperatures get high, and they dont want to limit weights...

The EO missed procedures with turns, if needed, would then result in an astronomical DA, temperature limits or weight limits.

[LIN]

Italia458.
I think you have misunderstood something about PANS-OPS.
According to Doc 8168, you cannot choose to operate an aircraft in different CAT (reduced speed during circling in order to use lower minima, etc).
8168 Vol.II states: "An operator may impose a permanent, lower landing mass, and use this for determining V(at) if approved by the state of the operator. The category defined for a given aeroplane shall be a permanent value and thus independent of changing day-to-day operations." (Part I, Section 4, Chapter 1. 1.8.6)
and
"The design of procedures in accordance with PANS-OPS criteria assumes normal operations. It is the responsibility of the operator to provide contingency procedures for abnormal and emergency operations" (Foreword 1.5)
Hope this helps
Regards
LIN

[italia458]

LIN...

According to Doc 8168, you cannot choose to operate an aircraft in different CAT (reduced speed during circling in order to use lower minima, etc).

I have that on my computer at home, I'll have to take a look at it. In Canada I'm not sure that 8168 is a specific document that we need to abide by. Being Canada, our rules are based on ICAO rules but we have the Canadian Aviation Regulations (official document) and the AIM which expands on the rules and provides some ways that you can comply with the CARs and then we also have the ICAO AIP.

I haven't seen a regulation specifically stating how the operating speed needs to be determined with regard to the specific Categories. If anyone can point me to something in a Canadian document that'd be great!

[9.G]

italia458, look at RAC 9.21 :ok:

[italia458]

9.G...

RAC 9.21 states:

"Aircraft that are manoeuvred
within these category speed ranges are to use the appropriate
instrument approach minima for that category."

I'm well aware of that. It doesn't say that I can't operate 5 knots slower than 140 kts so that I can drop from Cat C to Cat B for departure so I don't need 2SM vis for departure!

[FlightPathOBN]

Italia,

I have provided most of the RNP procedures used by Westjet in Canada...
NAVCANADA uses TP308 for the design critieria, which is virtually FAA TERPS.
The CAT references are the same as FAA... including the holding patterns.
Note that the FAA hold patterns are much different that the ICAO hold patterns. http://www.faa.gov/documentLibrary/media/Order/7130.3A.pdf

(in answer to the CAT question, you can always fly a faster CAT than your aircraft, but never a slower CAT...)

TP308 references FAA documents for the following:

Non-precision instrument approach procedures;
Precision instrument approach procedures;
Departure instrument procedures; and
En route instrument procedures.


From TP308 ammendments...http://www.tc.gc.ca/media/documents/ca-publications/ac2005-3.pdf

This amendment brings TP308/GPH209 up to date with FAA Order 8260.3B Terminal Instrument Procedures (TERPs) by incorporating new and revised sections based on TERPs changes 17-19.

From TP308 GPH209
Volume 6, Supplemental Criteria Construction
(1) Document 1 – Flight Management System (FMS) – Added
(a) Former US FAA Order 8260.40
(2) Document 2 – RNAV Departures – Added
(a) Former US FAA Order 8260.44
(3) Document 3 – Terminal Arrival Areas (TAA) – Added
(a) Former US FAA Order 8260.45
(4) Document 4 – Wide Area Augmentation System (WAAS) – Added
(a) Former US FAA Order 8260.50
(5) Document 5 – Required Navigation Performance (RNP) – Added
(a) Former US FAA Order 8260.51
(6) Document 6 – Precision ILS Category II/III (ILS CAT II/III) – Added
(a) Former US FAA Order 8260.61

[italia458]

FlightPath...

I'm aware of TP 308 and of how it relates to other documents. The current document version is Change 5.3, not sure if you have that one.

Can you provide a reference for what you said: "you can always fly a faster CAT than your aircraft, but never a slower CAT"

[9.G]

Doc 8168.

1.3 CATEGORIES OF AIRCRAFT

1.3.1 Aircraft performance has a direct effect on the airspace and visibility required for the various manoeuvres associated with the conduct of instrument approach procedures. The most significant performance factor is aircraft speed.

1.3.2 These categories provides a standardized basis for relating aircraft manoeuvrability to specific instrument approach procedures. For precision approach procedures, the dimensions of the aircraft are also a factor for the calculation of the obstacle clearance height (OCH). For Category DL aircraft, an additional obstacle clearance altitude/height (OCA/H) is provided, when necessary, to take into account the specific dimensions of these aircraft.

1.3.3 The criterion taken into consideration for the classification of aeroplanes by categories is the indicated airspeed at threshold (Vat ), which is equal to the stall speed Vso multiplied by 1.3, or stall speed Vslg multiplied by 1.23 in the landing configuration at the maximum certificated landing mass. If both Vso and Vslg are available, the higher resulting Vat shall be applied.

1.3.4 The landing configuration that is to be taken into consideration shall be defined by the operator or by the aeroplane manufacturer.

1.3.5 Aircraft categories will be referred. to. throughout this document by their letter designations.

1.3.6 Permanent change of category (maximum landing mass).

An operator may impose a permanent lower landing mass, and use of this mass for determining Vat if approved by the State of the Operator. The category defined for a given aeroplane shall be a permanent value and thus independent of changing day-to-day operations.

1.3.7 As indicated in Tables I-4-1-1 and I-4-1-2, a specified range of handling speeds for each category of aircraft has been assumed for use in calculating airspace and obstacle clearance requirements for each procedure.

1.3.8 The instrument approach chart (IAC) will specify the individual categories of aircraft for which the procedure is approved. Normally, procedures will be designed to provide protected airspace and obstacle clearance for aircraft up to and including Category D. However, where airspace requirements are critical, procedures may be restricted to lower speed categories.

1.3.9 Alternatively, the procedure may specify a maximum IAS for a particular segment without reference to aircraft category. In any case, it is essential that pilots comply with the procedures and information depicted on instrument flight charts and the appropriate flight parameters shown in Tables I-4-1-1 and I-4-1-2 if the aircraft is to remain in the areas developed for obstacle clearance purposes.

[FlightPathOBN]

Here is an FAA reference...

SAFO 12005 (https://docs.google.com/viewer?url=http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2012/SAFO12005.pdf)

[italia458]

9.G...

As stated in a previous comment I don't believe 8168 applies to Canada. Also, 8168 is talking about categories based on Vat which is essentially Vref - the speed to be targeted at 50' above the runway, over the threshold. That is NOT what Canada's rules are based on. Canada's rules for categories are based on your indicated speed at which you are commencing the maneuver at. I thought you knew that as you referenced a Canadian document; RAC 9.21. If you will do a circling approach at 140 kts you will be in cat C. Our Vref speed is in cat B - however we do NOT get to use the circling minima for cat B as we are operating in the speed range of cat C.

Again, I have not seen any rule in Canadian regulations that state we can't change indicated airspeeds while maneuvering to change the category we are in.

[italia458]

FlightPath...

I have never seen such a thing and I don't believe it exists in Canada. I've looked into this before as I used to teach multi-IFR and I'm quite sure Canada doesn't have those rules. It makes sense that the category doesn't change IF you base it on Vref for the MCLW. The way Canada does it is by the indicated speed at which you're operating for the particular maneuver.

I think there's a bit of a problem when you base it on Vref though, as you will be flying significantly faster than that while circling. The aircraft I fly, we circle in cat C, fly to the MAP on a precision or NPA in cat C but our Vref is cat B. The Canadian way seems more restrictive. It's entirely possible we could fly our approaches and circling 5 knots slower so that everything is in cat B though.

[FlightPathOBN]

The CAT certification is by the aircraft manufacturer.

The 8168 final approach CAT is based on the speed of the SEGMENT, FAF to threshold, not crossing the threshold. There are other segment and holding speeds per the CAT.


You can go up a CAT by going faster, if conditions warrant and the regulator allows. Many CAT C aircraft, esp 737 variants, use a CAT D approach speed and minima, IF they are authorized...

[italia458]

FlightPath...

Interesting. But not in Canada. It seems like you're an approach designer - I would assume you understand why it would be good to limit an airplane based on the speed at which they're flying a maneuver or segment in instead of their Vref speed?

I am a little confused as to what you're talking about though since you just mentioned 8168 final approach CAT is based on the speed of the final approach segment but 8168 and your FAA document states that it's based on Vat (Vref).

What does the FAA use for determining category for specified visibility takeoffs?

[FlightPathOBN]

The final segment CAT speed is based on Vref. So for a CAT C aircraft, speed in the final approach segment can range from 140 to 164 kts IAS.

Other segments have minimum speeds as well per CAT..
http://operationsbasednavigation.com/wordpress/wp-content/uploads/2012/12/SC-01-e1356741642998.jpg

To calc RVR:
rho=log(I=ET ) 􀀀 2 log/RVR

MOR =log(0:05)RVRlog(I=ET ) 􀀀 2 logRVR equals 3RVRlog(I=ET ) 􀀀 2 logRVR

Calculate MOR550 corresponding to RVR = 550m using the intensity of the
edge lights.
 Calculate MOR200 corresponding to RVR = 200m using the intensity of the
centre line lights.
 Using Koschmeider’s Law, calculate the actual MOR.
 Compute  such that MOR = MOR550 + (1 􀀀 )MOR200. Then the …nal
value of RVR = 200 + 350. :ok:

[italia458]

FlightPath...

This is from Canada's current TP 308 document - there are 3 pages I've uploaded.

First page shows that all maneuvers are based on airplanes flying by the speeds listed under paragraph 212 - this is applicable all times there are specific restrictions or minima for categories published (ie: spec vis departure, DA, MDA, circling, etc.)

As you know, TAS at altitude will be higher than IAS and that needs to be compensated for. Formulas published in the TP 308 document account for that.

Page 3 shows a very similar chart to the one you posted. This is Canada's guide to developing instrument procedures and this is what we follow. Essentially, protection areas are defined based on these speeds, which provides a margin of safety for aircraft operation.

I will emphasize that aircrews are to abide by the chart on page 1 to determine what category they are in based on their indicated speed at which they are carrying out the maneuver.


https://www.box.com/s/iwreiuzbt040jglkwhra
https://www.box.com/s/3htnrh8n6kvw389n3zw7
https://www.box.com/s/2frpd9y2ipb12lqma4x2

Edit:

What does the FAA use for determining category for specified visibility takeoffs?

I don't think you understood my question. A specified visibility takeoff is a visual climb over the airport for the initial departure, up to a specified altitude so as to clear obstacles. Usually a standard 1/2 departure will also be depicted but with a climb gradient in excess of 200'/NM. If you are unable to meet the required higher climb gradient, you have the option of departing while maintaining visual contact with the center of the aerodrome until a certain altitude that will permit a 200'/NM climb up to the minimum altitude for enroute operations. The required visibility in Canada for such a takeoff is: Cat A (1SM), B (1.5SM), C and D (2SM).

Does the US have such a thing?

[LIN]

Italia458:
I have to give in! You are correct in what you say, but only with regard to Canadian rules! The original question was with regard to Doc 8168, however.
I have just had a short look at TP 308, and I must say that I'm amazed at how much different from DOC 8168 it is. Even basic things like primary and secondary areas are very different, Speeds for categories of aircraft are completely different, etc, etc.
How on earth there can be that great differences in criteria from country to country within the very international world of aviation is beyond me.
I am a PANS-OPS designer, so I do know 8168, but I will certainly not call myself an expert on TP 308 (or TERPS, for that matter).
Why can't we all agree on using one set of rules? Isn't that why we have ICAO?
Regards
LIN

[italia458]

LIN...

You learn something new every day! I wasn't aware that category speeds were determined in such a different way, especially for Canada's next door neighbour, the good ol' US of A! I personally think that it makes more sense to determine your category based on what you're actually flying the maneuver at that day and not a speed you're supposed to be at when you're 50' AGL. Obviously, as I have said before, it doesn't matter what speed you're flying a maneuver at... if you can keep the airplane within the distance limits for the protection area, you will be safe! - So the FAA and PANS-OPS rules aren't necessarily bad, but I would argue that the faster you go, the more distance you use to maneuver, therefore, having more distance available to you is the safer option.

I just don't think I have enough pull with the FAA or ICAO to make any sort of change like that though! And I am biased as I'm only really familiar with TP 308 and Canadian rules.

Why can't we all agree on using one set of rules? Isn't that why we have ICAO?

I agree! It isn't as if the airplanes flown in Europe, or the USA, or Canada operate under different physics requiring extra/different rules to ensure obstacle clearance. I would say it'd take a heck of a lot of work to get everything down to one ICAO doc that every country that's a part of ICAO uses.... an enormous amount of work!

[FlightPathOBN]

It is similar, in fact is is the same, as Canada uses the FAA criteria, virtually an exact copy...all of that design criteria that you showed is TERPS...not ICAO 8168...

The approach CAT is based on speed of the final segment. In both criteria.
I also dont understand the 50' reference to approach speeds. Neither TERPS nor PANSOPS uses approach speed at 50'...where is that coming from?

You have to have a CAT speed for the maneuvers, to make sure the aircraft stays within the prescribed containment areas.

As an example, circling approaches, the TERPS circling minimum provides 300 feet of obstacle clearance within the circling approach area. The size of this area depends on the category in which the aircraft operates.

Category A 1.3 – mile radius
Category B 1.5 – mile radius
Category C 1.7 – mile radius
Category D 2.3 – mile radius
Category E 4.5 – mile radius

PANSOPS uses a different value for the minimum obstacle clearance, hence the radius values are different, with the ICAO criteria being much more conservative (larger)

The differences in calculations for the approach are simple...PANSOPS uses a level section, while TERPS does not.

The other containment areas concepts are very similar between PANSOPS and TERPS, but again, with more conservative values, PANSOPS creates much larger containment areas.

One must remember that the FAA and Boeing have lead virtually all of the criteria.

Good example is RNP...developed and created by the FAA and very usable with 8260.52....when 'adopted' by ICAO, just try to wade through 9905 with all of the technical and other errors in the document....
why did ICAO decide to change all of the terminology?
There was an ICAO version 8260.52A floating around that was an FAA attempt to harmonize with the ICAO terminology..but..they had already worked up 8260.54A, which has the ICAO terminology...

As for the CAT speed difference, ICAO has higher speeds per CAT, most likely to keep more Airbus variants in a lower CAT, and therefore increase access to airports (many airports have CAT C limits on runways/procedures)

Why ICAO decides to 'adopt' the FAA criteria by modifying it to create virtually the same results, is a matter for the politicians, not engineers.

[9.G]

I'd surely be reading about the differences in determination of approach category when I fly to YVR or YUL, wasn't the case for the past years nor will it change in the near future. I have no desire to argue bout the semantics. Look here: the whole bloody world goes by one single rule and Canada doesn't. Don't think so. Simplest logic is the best approach sometimes. :ok:

[italia458]

FlightPath...

It is similar, in fact is is the same, as Canada uses the FAA criteria, virtually an exact copy...all of that design criteria that you showed is TERPS...not ICAO 8168...

Yes, TP 308 is closest to TERPS but it's not a 100% copy... very close though.

The approach CAT is based on speed of the final segment. In both criteria.
I also dont understand the 50' reference to approach speeds. Neither TERPS nor PANSOPS uses approach speed at 50'...where is that coming from?


PANS-OPS references Vat speed and TERPS references Vref speed - they are essentially the same. Look up the definition of Vref. It's the speed the airplane is to attain at 50' above the runway. On the final segment, usually operators will fly at REF +5 to REF + 10 and do a slow deceleration so as to reach REF at 50' above the runway. Reference FAR 25.125(b)(2).

I understand all the circling requirements and distances, etc.

I think this discussion is about the speeds and categories that are applicable for those speeds - and the determination of the speeds.

It appears the FAA and ICAO use the Vref or Vat speed, respectively, to determine the category that the airplane is to maintain. Canada does not. Canada's rules, as I have referenced, state that the speed at which you are flying the maneuver at will determine what category you are to maintain.

9.G...

Look here: the whole bloody world goes by one single rule and Canada doesn't. Don't think so.

You're in denial, 9.G. I've referenced the applicable documents to show you that Canada doesn't follow the same rules as the FAA and ICAO with regard to this issue.

[FlightPathOBN]

The CAT speeds are minimums per segment...

Sorry, but as a wholly owned subsidiary of the US, Canada just scrapes the name tag off the FAA order...

Dont you remember the other post?

From TP308 GPH209
Volume 6, Supplemental Criteria Construction
(1) Document 1 – Flight Management System (FMS) – Added
(a) Former US FAA Order 8260.40
(2) Document 2 – RNAV Departures – Added
(a) Former US FAA Order 8260.44
(3) Document 3 – Terminal Arrival Areas (TAA) – Added
(a) Former US FAA Order 8260.45
(4) Document 4 – Wide Area Augmentation System (WAAS) – Added
(a) Former US FAA Order 8260.50
(5) Document 5 – Required Navigation Performance (RNP) – Added
(a) Former US FAA Order 8260.51
(6) Document 6 – Precision ILS Category II/III (ILS CAT II/III) – Added
(a) Former US FAA Order 8260.61

[italia458]

FlightPath...

Canada is not a "wholly owned subsidiary of the US". We have VERY similar procedures but they are clearly not the same. Why do you think you're required to take an exam if you want to transfer your license to TC or FAA?

The CAT speeds are minimums per segment...

I understand that! It's written quite clearly in the FAA document you showed me. However, that FAA document DOES NOT apply in Canada!

You seem to refuse to believe or have trouble understanding that Canada does not follow the FAA rules on this issue! I've already showed you the applicable Canadian documents to prove that. What are you unclear about?

[9.G]

The discussion about a straight-in mins is theoretical anyway as they're all the same for all categories. Only the circle to land differ with the IAS. :ok:

[FlightPathOBN]

Aircraft are certified by the manufacturer for the Approach CAT.

Vref is based on several factors, with a baseline. Different weight and flap settings influence the actual value, and many operators will use CAT D for a CAT C aircraft when calculating an approach...
As an example, the Vref CAT C for a 737 is based on 40T LW with flaps 30...

The pilot must calc actual LW and flaps to determine to use the CAT C or CAT D approach...

[Capn Bloggs]

Haven't read the whole thread but:
As an example, the Vref CAT C for a 737 is based on 40T LW with flaps 30...

The pilot must calc actual LW and flaps to determine to use the CAT C or CAT D approach...
That's not what the Australian AIP (ENR 1.5 1.2.1) says at all. The approach CAT is determined by the Vref at MLW in the approach config. You cannot reduce the Cat here because you are light.

[de facto]

As an example, the Vref CAT C for a 737 is based on 40T LW with flaps 30...
How did you/they come up with such a number?,my 737 DOW(no cargo,no pax,no fuel) is around 45T:eek:

On a side note,my airline aircraft that are Categorized as Cat C have always a VREF below 141kts with Flaps 40 NOT 30 and a go around flaps 15 below 160kts...food for thought:E

[BOAC]

Apart from his weights, FPO is surely correct? Any weight above MLW or 'abnormal' config could result in a higher Cat?

[Level Attitude]

I found this thread quite interesting so wanted to add in my (probably
mis-informed) opinion and questions.

I'm looking from the perspective of Light Twin Piston flying in UK, so unsure
if ponts relevent to other countries, jets, more than 2 engines, etc.

If an MEP cannot obtain, or exceed, a 2.5% climb gradient with one engine
inoperative then planing (as far as practicable) should be based on SEP
criteria:

eg:
- No (commercial) departure if cloud base is below 1,000' above
airfield - to allow for visual obstacle clearance in the event of an EFATO.

- Do not descend below 300' above threshold unless you are committed to land:
ie Runway in sight, Runway available, Stable Approach and Landing
clearance received.
This implies that with an engine failure the MAP would be further back, and
hence higher, along the FAT. So if a missed approach was initiated the
2.5% obstacle clearance surface would not be breached even with a climb
gradient of less than 2.5%.

Only time there might be a problem is if you are on an all engine approach
and you lose an engine whilst fairly low on FAT - However your chances here
are still much higher than if you were in a single engine aircraft to
start with.

So if aircraft not capable of 2.5% climb on one engine should you not plan
your approach to a higher Decision Altitude?

[de facto]

Any weight above MLW or 'abnormal' config could result in a higher Cat?

I would think so yes.

[9.G]

Any weight above MLW or 'abnormal' config could result in a higher Cat?-don't think it's the case for a straight in though. :ok:

[FlightPathOBN]

For the 737, Vref rule of thumb was based on 40T and flaps 30.

Then Vref can be est with -1 less/at than 40T and 3 kts above fl30

So at 40T, with flaps 30 equals 40x3-1=119kts as a standard Vref

for 40T at flaps 40 = Vref 30-3 kts or 116kts...

As you increase the weights, with flaps 30 as the ref...you get the actual CAT reference..

Regarding previous comments, I am not sure about ATC ops vs criteria in the US, but in all of the other places, from the IF inbound, if you go missed, you are required to follow the missed approach procedure (which may include descent because of crossing paths) and to harmonize with departures, LAHSO, etc...

[de facto]

Quote:
Any weight above MLW or 'abnormal' config could result in a higher Cat?
-don't think it's the case for a straight in though.

Yes it is,the CAT is based UP to MLW in a specific flaps config.


Flightpath,do you have a doc affirming the fact that flaps 30 was used to establish cat C or D?(what you call the 'ref'erence?).

[FlightPathOBN]

defacto,

You would have to look at your particular variant to see what they used as the reference for Vref CAT...usually I see it as the median weight, not MLW, with flaps 30. This sets the aircraft reference CAT,

Here is what Boeing supplies as the Ref CAT for the aircraft...you would have to back through the calcs to see what weight/flaps, to get that approach speed.
(I think a quick way is the check your QRH, I have one for the 737-700 right here...the Ref CAT from the Boeing table below is 129kts...looking at the QRH, that is a 55T flaps 30 match...


http://www.boeing.com/commercial/airports/faqs/arcandapproachspeeds.pdf

[de facto]

I am not familiar with -700 but by memory a 737-900 has a flaps 30 VREF of 151 kts at MLW.(far from the 141 kts in the table you provided).
A -800 at max landing weight may have a flaps 30 Vref of 147-148 kts.
A -800 would have to be around 58-60 T at flaps 30 to have a VREF of about 142, quite below max LDW..

All aircraft in my airline with max ldw of 66360 kgs are cat D as in your table.

[Capn Bloggs]

Flt Path OBN,

I say again, in Oz, you CANNOT willy-nilly pick your category depending on your weight. The Cat is based on the MLW at landing flap. Nothing else. Is the rest of the world different?

[FlightPathOBN]

defacto, Bloggs,

The aircraft CAT is set by the manufacturer, and that is worldwide, note the table Boeing table from the previous post....

The CAT is NOT based on MLW, nor max flaps, for that ac. The ref CAT also does not include any winds. The manufacturers certainly play with the numbers a bit, but that is their call.

For your edification, I looked it up on the 737-800 QRH.

The Boeing cert table shows the 737-800 approach speed at 142kts....(MLW is 73T)
from the QRH, that is 60T flaps 30.

[clevlandHD]

OBN, the chart you linked on top is for "Aerodrome Reference Code" not approach CAT. The stated approach speed is what gives the Approach CAT.(Ref Jepp Intro-chart glossary, p 2). Jepp is kind enough to seperate TERPS from ICAO CATs. TERPS uses Vref at MLW as ICAO uses Vat (speed at threshold). As for Canada, yes the text says use the actual LW Vref (which might allow to drop one notch) but the example provided is one UP. If you ever dealt with TC, you know there is a lot of "interpretation" and I would not test them on going one notch below. My operator classified each of our types as one, and only one, CAT. Makes sense to me.

[FlightPathOBN]

Airport Reference code is the Approach Cat and wingspan, hence the Cat C-III, with the reference speed for approach.

There is only one CAT allowed per aircraft, that is in all of the criteria.

Some States allow the pilot to use a higher CAT, depending on approach conditions.

TERPS/ICAO are design criteria for approach parameters, which include winds, aircraft cert approach speed does not. The approach speeds on final are based on Vref with a max per the CAT, it doesnt say how you get there, and MLW is not part of that...

The Aircraft certification is much different.

[clevlandHD]

You are right, I am wrong about this one (my Jepp paper copy is way too old)

"The Airport Reference Code (ARC) is a coding system developed by the Federal Aviation Administration to relate airport design criteria to the operational and physical characteristics of the airplane types that will operate at a particular airport. (The ARC is part of design standards established in the FAA Advisory Circular 150/5300-13, Airport Design (http://haywardairportnoise.org/%3CI%3Ehttp://www.faa.gov/airports_airtraffic/airports/resources/advisory_circulars/index.cfm?template=Document_Listing&Keyword=150/5300-13&DocumentSelected=1)</I>, June 2008.) The ARC has two components relating to the airport design aircraft. The first component, depicted by a letter, is the "approach category" and is based on aircraft approach speed. The second component, depicted by a Roman numeral, is the airplane "design group" and is based on airplane wingspan."

But you are wrong about how the CAT is established (FAR 97):
(b) Aircraft approach category means a grouping of aircraft based on a speed of VREF, if specified, or if VREF is not specified, 1.3 VS0 at the maximum certificated landing weight. VREF, VS0, and the maximum certificated landing weight are those values as established for the aircraft by the certification authority of the country of registry. The categories are as follows:
(1) Category A: Speed less than 91 knots.
(2) Category B: Speed 91 knots or more but less than 121 knots.
(3) Category C: Speed 121 knots or more but less than 141 knots.
(4) Category D: Speed 141 knots or more but less than 166 knots.
(5) Category E: Speed 166 knots or more.

or ICAO:
While the speed ranges used to determine an aircraft's approach category are identical to 14 CFR 97.3 (ICAO (http://www.skybrary.aero/index.php/ICAO) Doc 8168 PANS-OPS Vol 1, Section 4, Paragraph 1.3.5), the maximum permitted speed for visual maneuvering is significantly higher. The method used for determining the approach category speed is slightly different: VAT = speed at threshold based on 1.3 times VS0 (http://www.skybrary.aero/index.php/Vs0) or 1.23 times Vs1g (http://www.skybrary.aero/index.php/Vs1g) at maximum certificated weight. Additionally, speed ranges are specified for other segments of the approach: (ICAO Doc 8168, Vol 1, Section 4, Table I-4-1-2).

In both cases, CAT is at MLW and there is only one per aircraft(we agree on that!).

[Capn Bloggs]

Flightpath OBN, I'm a bit worried that in your position as an approach designer you seem to have little understanding of how approach categories are determined. It's got nothing to do with the manufacturer. Have you actually read AIP ENR 1.5 1.2.1? Its the Vat at MLW with Landing flap. Period.

[FlightPathOBN]

cleveland...

you had it close, but read the regs very closely...

and I know exactly how each aircraft CAT is determined, and how is is different that the procedure design CAT designation

Boeing and Airbus both specify Vref, for the certification process...and they way they do it is the secret sauce....if it was just Vref at MLW, then what were the flap settings? What about winds?

note: "or if VREF is not specified, 1.3 VS0 at the maximum certificated landing weight."

"VAT = speed at threshold based on 1.3 times VS0 or 1.23 times Vs1g at maximum certificated weight."

The Boeing table illustrates this how this is calculated very well...
From Boeing Airport reference code, D-III ref approach speed. 142 kts
from the 800 QRH MLW 73T
flaps 40 151 kts
flaps 30 158 kts
flaps 15 167 kts

From Boeing Airport reference code, D-III ref approach speed. 142 kts, so if you were designing a procedure for a 737-800...would you use the Boeing data, or the criteria data?

The Airport Reference Code (ARC) is a coding system developed by the Federal Aviation Administration to relate airport design criteria to the operational and physical characteristics of the airplane types that will operate at a particular airport. (The ARC is part of design standards established in the FAA Advisory Circular 150/5300-13A)

The ARC has two components relating to the airport design aircraft. The first component, depicted by a letter, is the "approach category" and is based on aircraft approach speed. The second component, depicted by a Roman numeral, is the airplane "design group" and is based on airplane wingspan.

Here is ICAO definition of Vref:
1.3 times the stalling speed in the stated landing configuration and at the prevailing aircraft weight. This is the speed required as the landing runway threshold is crossed at 50 feet height if calculated aircraft performance is to be achieved.

and then there is the reference stall speed VSR and 1.23 VSR

[clevlandHD]

If you use the Boeing chart, you will notice that the MLW giving that 142 kt is 66.3T. I don't fly the 737, so I can't tell. But the other types I have flown have the MLW as stated on that chart (and matching CAT); why would the 738 be different? Any 738 driver with a MLW higher than 66.3T?

[FlightPathOBN]

from Boeing chart MLW for the 737-800 is 146300, in the US, this is 73.15 tons?
Here is the Vref table from the 800 QRH..

Note flaps/speeds for 73.15T.. where does 142kts fit in with MLW?

http://operationsbasednavigation.com/wordpress/wp-content/uploads/2013/01/SC-06-e1357359001908.jpg

[FlightPathOBN]

If we go back to the original question CAT.
As we can see Boeing has a reference CAT for each aircraft, and the State uses this.

In the example for the 737-800, you CAN, at 50T, flaps 30, have a Vref of 129kts...this does not mean you can use a CAT C approach.

The actual aircraft, depending on configuration, will have its own certified MLW.

For approach procedure design, the segment speeds will have winds added...

Some regulators require ground speed for the procedure designs as well...

The 737-800 is a CAT D. Some airlines, will play with the weights and configuration, to get the aircraft to certified by the Boeing/State to CAT C for access, or to limit loading to save landing fees, etc.

[single chime]

just to clarify: 146300 lbs = 66361 kg = 73.15 short ton = 66.3 metric tonne

The Boeing chart give both the imperial/US weight (MLW 146300) and metric weight (MLW 66361kg).

The QRH chart you provide is METRIC. You can't enter your QRH chart with non-metric data.

[FlightPathOBN]

SG..thanks for correcting me...I didnt catch the KG...

[Pjotr Iljitsch]

Good morning all,

I’ve read now pretty much all the threads on pprune regarding gradients, acceleration, flap retraction & thrust reduction during the missed approach OEI & AEO.

I especially enjoyed and learned alot from many posts from tullamarine, aterpster, opendes, flightpathobn, rudddrrudderrat and others. Thank you for that!
Anyway, some questions haven’t been answered jet: Is the 2.4% gradient an average? tullamarine mentioned in one of his posts, that it depends on the source one is referring to and maybe on the understanding or translation of the words…In my case, I would refer to Pans Ops I&II and EASA (as I’m working for a german operator), where it says in the construction part that the gradient is a nominal gradient (tan Z). Therefore I don’t think it’s average?!?
If it’s not average, and it needs to be met during the intermediate and final missed approach phase (because the approach is construced so), that gradient should be calculated (by the pilot) at the missed approach altitude or the defined altitude on the IAC. So what is the sense in LPCNG and AI documentation in computing the gradient at airport pressure level?

In my previous outfit, credo was (a bit simplyfied): - missed approach all engines operating: published, reduce thrust, accelerate and clean up at missed approach altitude, MSA, or published acceleration altitude (e.g. many french airports), whichever comes first.

- missed approach OEI: follow (take off-) engine fail procedure, reduce thrust, accelerate and clean up at missed approach altitude, MSA or published acceleration altitude (e.g. many french airports), whichever comes first.

In my opinion, that was quite solid, as our ops engineers analysed all runways, etc. to develop the engine fail routings…

Hole different story in my new company…they let the pilots the choise between published and EFP, no mention at all of acceleration and thrust reduction altitudes in any books, and so on. Hence imho even more important to know for the pilots the calculation methods and requirements behind all that stuff to be able to determine whether I can fly the approach or not, where to accelerate and to reduce and which go around procedure to follow in case of…
So the 2nd the question: If the IAC says „using XXX minimum, 3.5% required up to 3000ft“, in my opinion, in LPCNG, the gradient should be calculated at 3000ft and consequently thrust reduction and acceleration should be at 3000ft?!?

One last thing, I found that those kind of question appear here on pprune and in other forums evers 4 years or so. Is that a lack of good education ;-)
Thank you all!

[camiloorduz]

Hi, can I was searching for info about how to calculate the relation between the missed approach % and the V/S. It seems you know how to calculate using the Vapp, can you tell me how to do it?.

Much appreciated,

Camilo Orduz.

[poldek77]

Hi, can I was searching for info about how to calculate the relation between the missed approach % and the V/S. It seems you know how to calculate using the Vapp, can you tell me how to do it?.

Much appreciated,

Camilo Orduz.

The simple formula is:
ROD (fpm) = % Gradient X Ground Speed (Knots)

Another way is to find an appropriate conversion table in your OM-C, eg. Jeppesen, Lido...

[john_tullamarine]

The simple formula is: ROD (fpm) = % Gradient X Ground Speed (Knots)

Minor side note for completeness. While the formula cited is used generally and is fine for pragmatic purposes, when one runs the unit conversions, there is around a 1 % error involved. This, normally, is ignored. However, just as well to be aware of the consideration.

Regarding varying the cat, I am rather amazed that folks might want to reduce cat limits with a weight reduction. I was always quite happy to adopt a higher cat on the jets (especially for nastier aerodromes) as that made everything a lot more comfortable ... just meant we didn't get in on occasion. Cost of doing business in my simple view of life.

[70 Mustang]

a third pilot in the flight deck with a sextant, an independent GPS unit, hard copies of relevant regulations and instrument approach constructions for every airport that will be used, a thermos of coffee, a couple of marmite sandwhiches, a slide ruler in his white shirt pocket, along with 6 ink pens and 6 pencils, a spare set of eye glasses and a pair of dice to calculate the chance of success for each takeoff, approach and missed approach. 😀

[ScepticalOptomist]

Regarding varying the cat, I am rather amazed that folks might want to reduce cat limits with a weight reduction. I was always quite happy to adopt a higher cat on the jets (especially for nastier aerodromes) as that made everything a lot more comfortable ... just meant we didn't get in on occasion. Cost of doing business in my simple view of life.

Australian AIP ENR 1.5 Para 1.2 prohibits reducing CATs.

[Chiefttp]

In the USAF, the jet I flew was a Cat D aircraft, however we flew many circling approaches as well as circling No-Flap approaches. When flying a No-Flap approach, if our approach speed exceeded 165 Knots which mandated we use the CAT E minimums on the approach plate. So even though we were a CAT D aircraft we changed our category depending on our approach speed for the maneuver being flown.
As far as missed approaches and the 2.5 degree climb gradient, my airline has “special engine out” procedures for airports whose terrain will not support a “straight out “ missed approach procedure flown at a 2.5 degree climb gradient. In these cases a special engine out procedure is designed to avoid terrain in an engine out scenario. Also we are required in the event of an engine out approach to check our engine out climb gradient. If the gradient exceeds the minimum required for the normal missed approach procedure we can fly the MAP as published on the approach plate. However, if the min climb gradient, engine out, is less than the published MAP procedure ( based on all engines operating) then we have to fly the special engine out procedure in lieu of the published missed approach procedure. We are further required to let ATC know our intentions, as we are told that ATC may not know what our company designed Special eng out procedure is.