Assymetric MDA
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Assymetric MDA
I was having a chat to a Check Captain the other day and he mentioned that when he was doing his check ride with CASA, the FOI had asked him "How much altitude would you add to your MDA/DA if you were assymetric and had to do an approach at XYZ aerodrome?"
I have never heard of any thing like it! I mean with my IREX, CIR and 3 renewals I dont recollect any requirement?
I asked another check captain and he had never heard of it either. Another colleague had some recollection that you were required to make a certain climb performance in the Missed Approach and so if you couldnt make this assymetric you were required to add the corresponding height to the MDA so as to get to the MSA within the specified time/distance.
From where I sit in a light piston twin, flying around remote areas with not a lot of aerodrome options I would expect that if I found myself assymetric I would declare an emergency and land ASAP as best as able under the circumstances.
How do I check up on this as I have not so far located any info in the CAO's or otherwise? I try to make a habit of chasing up any thing which I might need to know.
I have never heard of any thing like it! I mean with my IREX, CIR and 3 renewals I dont recollect any requirement?
I asked another check captain and he had never heard of it either. Another colleague had some recollection that you were required to make a certain climb performance in the Missed Approach and so if you couldnt make this assymetric you were required to add the corresponding height to the MDA so as to get to the MSA within the specified time/distance.
From where I sit in a light piston twin, flying around remote areas with not a lot of aerodrome options I would expect that if I found myself assymetric I would declare an emergency and land ASAP as best as able under the circumstances.
How do I check up on this as I have not so far located any info in the CAO's or otherwise? I try to make a habit of chasing up any thing which I might need to know.
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Unfortunately I don't have my Jepps to hand for references but there are obstacle clearance requirements that must be adhered to (I think it's 100ft for Cat A a/c).
You are also required to maintain a 2.5% gradient during a missed approach.
This obviously doesn't pose a problem for those flying RPT, however in a twin lightie, chances are the engine out climb performance will not be able to meet these requirements. Therefore, to meet the requirements, you are required to add a saftety margin to your MDA/DA.
This has to be done during the flight planning stage by looking at the single engine performance charts taking into account weight, temerature and pressure etc.
You are also required to maintain a 2.5% gradient during a missed approach.
This obviously doesn't pose a problem for those flying RPT, however in a twin lightie, chances are the engine out climb performance will not be able to meet these requirements. Therefore, to meet the requirements, you are required to add a saftety margin to your MDA/DA.
This has to be done during the flight planning stage by looking at the single engine performance charts taking into account weight, temerature and pressure etc.
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G'day Scramjet
Number of problems with this one.
You can easily ascertain the required climb gradient (2.5% as has already been pointed out) and with some research you can find out your aircraft's advertised S/Eng Rate of Climb (Not always completely accurate for a number of GA Types I have flown!!).
Unfortunately, this is where the easy part ends.
You would then need access to the Procedure Designer to see if the Missed Approach Climb Path was obstacle limited and if so by what, at what distance and at what height. After a short course in Procedure Design, you could then make an informed decision regarding an amended minima for the single engine case. You would probably need to make two cases, one for each of Critical and Non-Critical engine failure.
As far as completing this process during preflight planning, good luck!!!
Given that your GA twin has no performance requirements imposed by CAO's upon it other than to be able to maintain a positive climb gradient at 5000' (ISA conditions) in the clean configuration, there may be more pressing questions worthy of your attention. You may, in fact, be trying to find answers to questions that have not been researched.
Should you find yourself in this situation with weather below landing minima, you would proceed to your planned alternate. Should you find yourself in the situation where there is unforecast weather below the landing minima (and yes, I understand that this can happen) then you are indeed in an emrgency situation and I would suggest you find the ground as best you can, as you suggested.
It's not a satisfactory answer but it's the best I came up with over a number of years doing it.
Cheers
Number of problems with this one.
You can easily ascertain the required climb gradient (2.5% as has already been pointed out) and with some research you can find out your aircraft's advertised S/Eng Rate of Climb (Not always completely accurate for a number of GA Types I have flown!!).
Unfortunately, this is where the easy part ends.
You would then need access to the Procedure Designer to see if the Missed Approach Climb Path was obstacle limited and if so by what, at what distance and at what height. After a short course in Procedure Design, you could then make an informed decision regarding an amended minima for the single engine case. You would probably need to make two cases, one for each of Critical and Non-Critical engine failure.
As far as completing this process during preflight planning, good luck!!!
Given that your GA twin has no performance requirements imposed by CAO's upon it other than to be able to maintain a positive climb gradient at 5000' (ISA conditions) in the clean configuration, there may be more pressing questions worthy of your attention. You may, in fact, be trying to find answers to questions that have not been researched.
Should you find yourself in this situation with weather below landing minima, you would proceed to your planned alternate. Should you find yourself in the situation where there is unforecast weather below the landing minima (and yes, I understand that this can happen) then you are indeed in an emrgency situation and I would suggest you find the ground as best you can, as you suggested.
It's not a satisfactory answer but it's the best I came up with over a number of years doing it.
Cheers
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It's an airmanship thing. You're not "required" to add some feet to your MDA to meet the climb gradient, you're just required to meet the gradient, IF an engine fails, and IF you elect to follow the missed approach.
scramjet,
Don’t know if this applies to your operation, some operators will advocate an increase in performance CAT (eg B->C) for and aircraft for the S/E case which generally will change your MDA and missed approach obstacle clearance requirements, if he is of the older generation he might have been thinking of the old published flap acceleration altitudes.
However I also think the FOI was hinting at the S/E minimum obstacle clearance gradient (2.5%). The 2.5% is nil wind (nett), with a tail wind you would need a higher ROC.
PS Bendy...good post I have learnt something new !
Don’t know if this applies to your operation, some operators will advocate an increase in performance CAT (eg B->C) for and aircraft for the S/E case which generally will change your MDA and missed approach obstacle clearance requirements, if he is of the older generation he might have been thinking of the old published flap acceleration altitudes.
However I also think the FOI was hinting at the S/E minimum obstacle clearance gradient (2.5%). The 2.5% is nil wind (nett), with a tail wind you would need a higher ROC.
PS Bendy...good post I have learnt something new !
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*Lancer* I presume you are very good at predicting when your next engine failure is to occur. You will then have ample warning to work out what to do. You are quite correct, you are not 'required' to do anything. You are not 'required' not to hit the obstacle during your 'unscheduled' one engined overshoot if you fly by yourself. I suppose that you are also quite happy to be in 8/8 cloud and have as much as 100' obstacle clearance even if you can make the 2.5%. I'm sure you explain all that to your passengers before they go on board.
For those of you who think that there is a good reason for this requirement, there is a good article in the current Australian Flying magazine with a very simple formula to work it all out.
For those of you who think that there is a good reason for this requirement, there is a good article in the current Australian Flying magazine with a very simple formula to work it all out.
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AIP ENR 1.5 – 7 para 1.10.1 note 2: “If the missed approach climb gradient cannot be achieved the DA, MDA or RH should be increased, or other action taken to achieve the required obstacle clearance along the specified missed approach flight path.”
Quite clear really……….
However AIP ENR 1.5-2 para 1.6 states “EXCEPT IN AN EMERGENCY, (my capitals) an aircraft must not land or continue an approach below the approved DA, MDA or RH at any aerodrome where any element constituting the meteorological minima is continuously less than that prescribed rof that aerodrome and the particular operation”
Read into that what you will.
Quite clear really……….
However AIP ENR 1.5-2 para 1.6 states “EXCEPT IN AN EMERGENCY, (my capitals) an aircraft must not land or continue an approach below the approved DA, MDA or RH at any aerodrome where any element constituting the meteorological minima is continuously less than that prescribed rof that aerodrome and the particular operation”
Read into that what you will.
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Ok heading to the deepest darkest recesses of my memory here.
We all understand 2.5% is required and in a light twin you aint gonna get it.
Convert 2.5% to the RoC you require
find out what RoC you can make
brush the dust off your whizz wheel
Put what you can do on the outside scale against what you should do on the inside.
Look at the alt you need to climb from MDA to end of missed approach on the inside, it will line up with how many feet you can climb. You should raise your MDA by the shortfall.
Av
We all understand 2.5% is required and in a light twin you aint gonna get it.
Convert 2.5% to the RoC you require
find out what RoC you can make
brush the dust off your whizz wheel
Put what you can do on the outside scale against what you should do on the inside.
Look at the alt you need to climb from MDA to end of missed approach on the inside, it will line up with how many feet you can climb. You should raise your MDA by the shortfall.
Av
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GENTLEMEN!!!!
My first reaction to reading this post was - what the...!! It is VERY clear what is required.
You do NOT commence an approach to the MDA if you are not certain that if, at the MDA and the MAPt, you can climb away at 2.5% gradient TO THE MISSED APPROACH ALTITUDE.
That is all there is to it.
Can you be sure that, given the weight, temperature, wind and configuration in the approach, you can bug out to somewhere safe if you don't get in first go?
Lancer, an "airmanship thing?!?". It is beyond airmanship. It is a f
ing requirement!
And lancer, while we are here... "IF you elect to follow the missed approach." Do you design your own procedures as you go? Educate me, tell me what on earth is a better idea than carrying out the published missed approach if one is not visual at the MDA by the MAPt? I'd love to know!
It is NOT just for RPT guys. Jeppesen Terminal procedures applies to ALL IFR ops.
swh...
Change CAT? What nonsense. What operators? Not one that has a firm grip on their AoC. Again, AIP is crystal clear on what determines performance category. Show me where it says you can change CAT from B to C.
Whats that? You can't find it? Thats because it does not exist. Its 1.3 Vs MLW, go see Jepps Terminal. End of story.
You guys should take a little more care before posting bullsh!t where inexperienced guys might read it as 'industry practice.'
FWIW, I have been asked the 'how much do you add' question in my IFR renewals from the word go, from C210 carrying newspapers thru C402, Metro to 146.
If you can't make 2.5% then you work a higher MDA or you divert. Otherwise it is a last ditch option, a big Mayday with all the services.
My first reaction to reading this post was - what the...!! It is VERY clear what is required.
You do NOT commence an approach to the MDA if you are not certain that if, at the MDA and the MAPt, you can climb away at 2.5% gradient TO THE MISSED APPROACH ALTITUDE.
That is all there is to it.
Can you be sure that, given the weight, temperature, wind and configuration in the approach, you can bug out to somewhere safe if you don't get in first go?
Lancer, an "airmanship thing?!?". It is beyond airmanship. It is a f
ing requirement!And lancer, while we are here... "IF you elect to follow the missed approach." Do you design your own procedures as you go? Educate me, tell me what on earth is a better idea than carrying out the published missed approach if one is not visual at the MDA by the MAPt? I'd love to know!
It is NOT just for RPT guys. Jeppesen Terminal procedures applies to ALL IFR ops.
swh...
Change CAT? What nonsense. What operators? Not one that has a firm grip on their AoC. Again, AIP is crystal clear on what determines performance category. Show me where it says you can change CAT from B to C.
Whats that? You can't find it? Thats because it does not exist. Its 1.3 Vs MLW, go see Jepps Terminal. End of story.
You guys should take a little more care before posting bullsh!t where inexperienced guys might read it as 'industry practice.'
FWIW, I have been asked the 'how much do you add' question in my IFR renewals from the word go, from C210 carrying newspapers thru C402, Metro to 146.
If you can't make 2.5% then you work a higher MDA or you divert. Otherwise it is a last ditch option, a big Mayday with all the services.
Last edited by ITCZ; 8th Apr 2004 at 13:11.
Change CAT? What nonsense. What operators? Not one that has a firm grip on their AoC. Again, AIP/Jepp is crystal clear on what determines performance category. Show me where it says you can change CAT from B to C.
2.1.2 An aircraft must fit into and be operated in accordance with the requirement of only one category. An aircraft:
a. may not reduce category because of a reduced operating weight, but
b. must increase category when actual handling speeds are in excess of those for category (based on Vat) detailed in para 2.3
Just pointing out that you can change category in some circumstances.
There may be some types that have Vat of greater than 120 knots in a failure situation.
e.g Flapless landing ?
If we are talking specifically Single Engine, I guess it would not be the case.
There may be some types that have Vat of greater than 120 knots in a failure situation.
e.g Flapless landing ?
If we are talking specifically Single Engine, I guess it would not be the case.
ITCZ,
As Bill has provided with an example of how Vat may change, i.e. a new configuration other than the normal, flapless, partial flap, partial or full anti ice/deice or in icing conditions, failure of one or more AoA meters, Air Data Computer failure and failure of ....it goes on, this can even be without an engine failure.
Some aircraft also require handling speeds above normal speeds in icing conditions.
The most extreme example I can think of in GA applies to the PC12 which can have a Vat in icing conditions of 102 kts (CAT A->CAT B), or 134 kts for failure of the pneumatic deice boots in icing conditions, flaps 0 (i.e. change from CAT A -> CAT C).
Some aircraft operators require a handling speed when circling above 135 kts single engine, even when CAT B two engine, SF340 comes to mind.
Bill has kindly provided a ref for you already for the increase of CAT (JEPP TERM 2.1.2 (B)), and note CASA may permit an operator to reduce its CAT, (JEPP TERM 2.1.3 refers).
As Bill has provided with an example of how Vat may change, i.e. a new configuration other than the normal, flapless, partial flap, partial or full anti ice/deice or in icing conditions, failure of one or more AoA meters, Air Data Computer failure and failure of ....it goes on, this can even be without an engine failure.
Some aircraft also require handling speeds above normal speeds in icing conditions.
The most extreme example I can think of in GA applies to the PC12 which can have a Vat in icing conditions of 102 kts (CAT A->CAT B), or 134 kts for failure of the pneumatic deice boots in icing conditions, flaps 0 (i.e. change from CAT A -> CAT C).
Some aircraft operators require a handling speed when circling above 135 kts single engine, even when CAT B two engine, SF340 comes to mind.
Bill has kindly provided a ref for you already for the increase of CAT (JEPP TERM 2.1.2 (B)), and note CASA may permit an operator to reduce its CAT, (JEPP TERM 2.1.3 refers).
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ITCZ and I fly, you read to much into what I say...
There are alot of other emergencies apart from engine failures! If you have a blazing fire out on a wing and no fuel left, then taking a chunk OFF the MDA is likely to save your life. It's generally a requirement in passing an airline command check...
This is one of the few cases where the regs are generally ambiguous and airmanship is clear! Act conservatively, within the circumstances to avoid hitting the ground. Adding a margin to the MDA to achieve the gradient is a good thing to do. It's NOT a requirement - you could be in a single!!!
Where is the regulatory protection for that?? You could be in a triple or a quad, and lose 2 engines... regs CAN'T specify what to do in all circumstances, and they DON'T in this case. What you do to mitigate the risks is purely an airmanship response... but you are both correct - its something that should certainly be considered under normal circumstances.
On top of all that, there are painfully few loaded light twins that would even come close to reaching many MSAs on one engine... How do you guarantee what assymetric performance you're going to get in the first place?
Lancer:
There are alot of other emergencies apart from engine failures! If you have a blazing fire out on a wing and no fuel left, then taking a chunk OFF the MDA is likely to save your life. It's generally a requirement in passing an airline command check...
This is one of the few cases where the regs are generally ambiguous and airmanship is clear! Act conservatively, within the circumstances to avoid hitting the ground. Adding a margin to the MDA to achieve the gradient is a good thing to do. It's NOT a requirement - you could be in a single!!!
Where is the regulatory protection for that?? You could be in a triple or a quad, and lose 2 engines... regs CAN'T specify what to do in all circumstances, and they DON'T in this case. What you do to mitigate the risks is purely an airmanship response... but you are both correct - its something that should certainly be considered under normal circumstances. On top of all that, there are painfully few loaded light twins that would even come close to reaching many MSAs on one engine... How do you guarantee what assymetric performance you're going to get in the first place?
Lancer:
Last edited by *Lancer*; 9th Apr 2004 at 00:33.
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No approach or departure procedure can cater for all contingencies. 2.5% is what you’re required to achieve to give you the minimum obstacle clearance of 100FT. How you achieve that is up to you regardless of how many engines available to you at the time. If you have to add extra to your minima, so be it.
As Lancer alluded to, a raging wing fire most definitely constitutes an emergency. I couldn’t imagine ANYONE trying to hang you for busting minima in order to get the aircraft on the ground in that case.
As Lancer alluded to, a raging wing fire most definitely constitutes an emergency. I couldn’t imagine ANYONE trying to hang you for busting minima in order to get the aircraft on the ground in that case.
Like ITCZ I have to say that I am very disappointed that it has taken an IREX and 3 renewals before this 'concept' is being realised by guy's coming through the system these days. It's not entirely your fault Scramjet(although I am surprised), it's say's something about the quality of Pilot being 'manufactured' these days.
Bread and Butter stuff, really.
Bread and Butter stuff, really.
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Lancer, Scramjet asked the question " I was having a chat to a Check Captain the other day and he mentioned that when he was doing his check ride with CASA, the FOI had asked him "How much altitude would you add to your MDA/DA if you were assymetric and had to do an approach at XYZ aerodrome?"
Nothing said about a raging fire on one wing. And why would you be at MDA with no fuel?
I mistakenly thought that you answered the asked question and I commented in that light. If you would like to ask me "where do you go with a raging fire on one wing and no fuel" I would answer "down". In that case I fly by the law of gravity and not CASA.
Nothing said about a raging fire on one wing. And why would you be at MDA with no fuel?
I mistakenly thought that you answered the asked question and I commented in that light. If you would like to ask me "where do you go with a raging fire on one wing and no fuel" I would answer "down". In that case I fly by the law of gravity and not CASA.
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Bill and swh.
Swy initially offered "some operators will advocate an increase in performance CAT (eg B->C) for and aircraft for the S/E case"
This is just plain wrong. I can guess that what swh thinks he has been told, is that often (but not always!) a Cat C MDA is higher than the Cat B minima for the same approach plate.
Such thinking indicates a complete ignorance of what the plate is trying to achieve for you.
An IAL procedure is designed to get you in a position to make a successful circle- or final-approach to the desired AD/RWY. It is designed to offer a minimum margin of safety whilst you do so.
It also provides you with a 'way out' if all does not work as you would like - the missed approach. Provided that you heed the limits of the approach design.
I am sure that we would be dismayed if we read about 'some idiot tourist' that died of thirst when their rented 4WD ran out of juice in the Tanami desert, esp if said tourist had no water, no jerrycan of diesel, no epirb or RFDS HF, etc.
We would all shake our heads and say, "its sad, but those people had no business driving in the desert without knowing the precautions they should be taking."
Same with this subject.
Every pilot could expect a question like "what is the design obstacle clearance for the missed approach" in any sort of IFR renewal, ppl to atpl, single engine to six engines! Like a flash we all answer = 100' and 2.5% gradient, Jepp Terminal 3.10.1 (e) Note 2.
In this job, it is not enough to spit this stuff out on request once or twice a year to an ATO/checkie. You are actually supposed to apply this knowledge to your operation.
If you (1) knew the answer to the question above, and (2) also think that your aircraft will not be capable of making the gradient, and (3) you have not done any homework as to how you would get around this problem, then you should NOT be shooting IFR approaches.
I would put you in the same category as the unprepared 4WD tourist above. Has no business being where he/she is.
Blindly accepting 'change CAT to C' is absolute laziness. Unless of course you sat down and worked out that such a CAT C MDA resulted in a gradient of say 1.5%, and that you had also worked out that your aircraft could fly 1.5% or better.
It is not so hard, I just don't understand this inertia in other Pprune posters. For the effort seemingly expended diving into Jepps to rebut my previous post, you could have worked out the gradient your aircraft could fly single engine!
To put something positive here, lets have a look at how you might solve the problem....
Lets say that your flight manual tells you that for the weight and temp you expect at your destination, you will make about half the required 2.5% climb gradient, say 130 fpm at 100 KIAS in the single engine situation [rule of thumb: groundspeed kts x fpm = gradient of climb/descent]
The MDA for the Whup-whup NDB is say, 800'. The missed approach altitude is 2800'.
The guy who designed the NDB approach expects you to climb 2000' from the MAPt to the missed approach altitude.
But now you know your aircraft can only make just a little better than HALF that rate. So why not HALVE the altitude change, and add that to the MDA?
i.e. "My single engine MDA for the Whup-whup NDB is plus 1000', making it 1800' "?
You don't have to calculate this every time. Why not spend 10 minutes to add another rule of thumb to your book of tricks. I can remember off the top of my head that a C402C = 1000m TODR. That is, when I was working 402's in the Topend, if the strip was dry, and the temperature was 34degC or less, I did not need to refer to a P-chart. Less than 1000m, and time to open the book.
Likewise, p5-30 of the Cessna 402C Information Manual says that a fully loaded 402C at MTOW on a 34degC day at 2000' PAlt will climb at 180fpm once you have configured the aircraft for the SE climb, target IAS 104kts.
Thats 1.8% gradient when things are going well for you.
2.5% - 1.8% = 0.7%
0.7 divided by 2.5 = 0.28
Round up to increase the margin of safety.
So, the gradient 1.8% that the book says you can achieve is a factor of 0.3 less than the required 2.5% the MA procedure requires.
0.3 of the 2000' altitude gain at Woop-woop is 600 feet. That is, using single engine climb, you will be 600' short of the missed approach altitude. Add that 600' to the MDA of 800', giving you an MDA of 1400' if you are conducting a single engine approach.
So if BNE Centre reports cloud BKN010 at Woop-woop and you are sweating along with one feathered, your decisions are clearer. Divert, hold if it is lifting, or declare an emergency and shoot the approach, knowing that you are NOT assured of a way out once you descend below 1400'
Now having said all this, I am sure that it will prompt an avalance of posts saying "No, ITCZ has a cr@p way, my sums are easier/better/more accurate...."
GOOD. At least we will get some solutions being posted, instead of dismissing it as an 'airmanship' thing.
Swy initially offered "some operators will advocate an increase in performance CAT (eg B->C) for and aircraft for the S/E case"
This is just plain wrong. I can guess that what swh thinks he has been told, is that often (but not always!) a Cat C MDA is higher than the Cat B minima for the same approach plate.
Such thinking indicates a complete ignorance of what the plate is trying to achieve for you.
An IAL procedure is designed to get you in a position to make a successful circle- or final-approach to the desired AD/RWY. It is designed to offer a minimum margin of safety whilst you do so.
It also provides you with a 'way out' if all does not work as you would like - the missed approach. Provided that you heed the limits of the approach design.
I am sure that we would be dismayed if we read about 'some idiot tourist' that died of thirst when their rented 4WD ran out of juice in the Tanami desert, esp if said tourist had no water, no jerrycan of diesel, no epirb or RFDS HF, etc.
We would all shake our heads and say, "its sad, but those people had no business driving in the desert without knowing the precautions they should be taking."
Same with this subject.
Every pilot could expect a question like "what is the design obstacle clearance for the missed approach" in any sort of IFR renewal, ppl to atpl, single engine to six engines! Like a flash we all answer = 100' and 2.5% gradient, Jepp Terminal 3.10.1 (e) Note 2.
In this job, it is not enough to spit this stuff out on request once or twice a year to an ATO/checkie. You are actually supposed to apply this knowledge to your operation.
If you (1) knew the answer to the question above, and (2) also think that your aircraft will not be capable of making the gradient, and (3) you have not done any homework as to how you would get around this problem, then you should NOT be shooting IFR approaches.
I would put you in the same category as the unprepared 4WD tourist above. Has no business being where he/she is.
Blindly accepting 'change CAT to C' is absolute laziness. Unless of course you sat down and worked out that such a CAT C MDA resulted in a gradient of say 1.5%, and that you had also worked out that your aircraft could fly 1.5% or better.
It is not so hard, I just don't understand this inertia in other Pprune posters. For the effort seemingly expended diving into Jepps to rebut my previous post, you could have worked out the gradient your aircraft could fly single engine!
To put something positive here, lets have a look at how you might solve the problem....
Lets say that your flight manual tells you that for the weight and temp you expect at your destination, you will make about half the required 2.5% climb gradient, say 130 fpm at 100 KIAS in the single engine situation [rule of thumb: groundspeed kts x fpm = gradient of climb/descent]
The MDA for the Whup-whup NDB is say, 800'. The missed approach altitude is 2800'.
The guy who designed the NDB approach expects you to climb 2000' from the MAPt to the missed approach altitude.
But now you know your aircraft can only make just a little better than HALF that rate. So why not HALVE the altitude change, and add that to the MDA?
i.e. "My single engine MDA for the Whup-whup NDB is plus 1000', making it 1800' "?
You don't have to calculate this every time. Why not spend 10 minutes to add another rule of thumb to your book of tricks. I can remember off the top of my head that a C402C = 1000m TODR. That is, when I was working 402's in the Topend, if the strip was dry, and the temperature was 34degC or less, I did not need to refer to a P-chart. Less than 1000m, and time to open the book.
Likewise, p5-30 of the Cessna 402C Information Manual says that a fully loaded 402C at MTOW on a 34degC day at 2000' PAlt will climb at 180fpm once you have configured the aircraft for the SE climb, target IAS 104kts.
Thats 1.8% gradient when things are going well for you.
2.5% - 1.8% = 0.7%
0.7 divided by 2.5 = 0.28
Round up to increase the margin of safety.
So, the gradient 1.8% that the book says you can achieve is a factor of 0.3 less than the required 2.5% the MA procedure requires.
0.3 of the 2000' altitude gain at Woop-woop is 600 feet. That is, using single engine climb, you will be 600' short of the missed approach altitude. Add that 600' to the MDA of 800', giving you an MDA of 1400' if you are conducting a single engine approach.
So if BNE Centre reports cloud BKN010 at Woop-woop and you are sweating along with one feathered, your decisions are clearer. Divert, hold if it is lifting, or declare an emergency and shoot the approach, knowing that you are NOT assured of a way out once you descend below 1400'
Now having said all this, I am sure that it will prompt an avalance of posts saying "No, ITCZ has a cr@p way, my sums are easier/better/more accurate...."
GOOD. At least we will get some solutions being posted, instead of dismissing it as an 'airmanship' thing.
