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Death Pencil
5th Aug 2007, 12:01
For an NPA (namely Adelaide Australia 12 VOR) there are 2 MDA's published for a straight in approach. The lower MDA of 470ft requires a 3.6% gradient. The higher MDA of 780ft requires the standard 2.5%.

When flying a multi-engine aircraft (a light one, which will just achieve 2.5%, maybe a little more) which MDA should be used?

Arguments for the lower one; better chance of getting visual (especially in an actual engine failure scenario), there can be an 'escape route' if you need to conduct the missed approach and unable to achieve the gradient (whether an engine has failed prior to or during the missed approach, regardless).

Arguments for the higher; the gradient can't be achieved in the missed approach if an engine fails.... which leads on to another stance....

use the lower one if both engines are operating, the higher if asymmetric. (but what happens if one fails during the missed approach from the lower MDA and the 3.6% cannot be achieved?)

:ugh:

chart:

In some cases, if 2.5% cannot be achieved, there are ways to calculate how much to raise the MDA by to achieve obstacle separation up to the Missed approach altitude... I don't see why that principle would change in this case.

Any references to documents would be appreciated.

:ok:

Bomber Harris
5th Aug 2007, 14:36
DP, i'm afraid MDA's are not like a selection box, which you can't choose the one that suits.
Basically, you MUST assume an engine failure at minimums. Thats the rules to protect you and you passengers. So you have to calculate at your weight, px alt, temperature what your climb gradient is single engine from the performance section of the flight manual. you then use the appropriate minimums.
you may already know this, but in case you don't; unless otherwise stated a GA requires a minimum 2.5 degrees (actually i think it might be 2.4) climb gradient from the MDA for the required terrain separation (which varies dependant on which segment you are in). Aircraft which meet certain weight and passenger carrying capability used commecially must all be able to demonstrate the ability to meet this engine out requirement. Some airports which have restrictive minimums because of terrain are aware that some aircraft way exceed this 2.4 deg climb gradient, so they can offer less restricitve minimums requiring a higher climb gradient
however, i still do fly privately and i am aware that the same rules do not apply. as i tend not to fly when the wx is that bad, i have not had cause to refresh my knowledge on the less restrictive practices in private flying. i know for example that some multi engine aircraft can just about stay level single engine. so there is no requirement to make the 2.4 climb gradient for certification, but you could not use that aircraft bin commercial scheduled operations. we used to class the aircraft as perf A,B,C and D but the terminalology has all changed now i think.
Thats the little i know on the subject. hope it helps

Death Pencil
6th Aug 2007, 06:15
I agree entirely, however have a hard time convincing some.
Is there anywhere which says that you MUST do this? (apart from commen sense :}) Have had a look through Jepps and Australian regulations... no luck.

Piltdown Man
6th Aug 2007, 13:49
So what gradient can you make? You really ought to know the answer to that one. And the second question, what would you if you have an engine failure following a go-around when using the lower MDA? I'll tell you what we would do and that's to follow the non-standard N-1 procedure that you would use following an EFATO (and not the Standard Missed Approach as depicted on the approach chart). The rationale behind this is that the point where you start the go-around (before the start of the runway) will give you a distance bonus vs the take-off scenario. You'll also have the additional bonus of flying speed before the start of the take-off point.

Now which minima you use is your choice but at least you have an argument for using the lower minima.

PM

A-3TWENTY
7th Aug 2007, 07:47
When you fly for an airport with different MDA`s or DA ( Might be an ILS ex.LECO) ,
you have to check your APPROACH CLIMB PERFORMANCE TABLES and check that you can lower the minimums , matching airport elevation with your GW.

It protects you in case of an engine failure on the right momento you start a GA.

Cheers

ITCZ
7th Aug 2007, 13:13
I'll tell you what we would do and that's to follow the non-standard N-1 procedure that you would use following an EFATO (and not the Standard Missed Approach as depicted on the approach chart). The rationale behind this is that the point where you start the go-around (before the start of the runway) will give you a distance bonus vs the take-off scenario. You'll also have the additional bonus of flying speed before the start of the take-off point.

You might try it, but you would not have the protection you thought you had. I'd think a little more carefully about that one, P M.

I take it your N-1 procedure is what my FMS calls an EO SID, or what my operator calls a Special Departure Procedure.

Sure, you have speed and altitude. The one thing you WONT have, which is most important, is an RNP 0.05 nav tolerance and superb tracking guidance on that go-around.

EO SID/SDP are designed for departures off a runway. The EO SID/SDP commences at the departure threshold and is a 'gate' maybe 300m (0.15nm) wide.

It is one thing to go through that 'gate' departing off a 30m-60m wide runway. But it is another thing entirely to accurately place your aircraft within 150m of a ground fix in a single engine go around from a DA or MDA. And you are proposing to do that at or shortly after an engine fails in the go around.

Tricky.

Try it next time you are in the sim, and get the printout. Very few turboprop or jet transport pilots can do that trick in VMC, let alone IMC.

mustafagander
8th Aug 2007, 12:22
An answer to the question posed by Death Pencil in post #1 is inferred in CAO 20.1.7 and 20.1.7b. These refer you to the AFM data. I am only passing familiar with the little a/c but seem to recall landing climb data there somewhere, but is definitely part of RPT ops manuals and they require the PIC to ensure that the a/c planned LW is not above that which allows certified approach climb and landing climb gradients under existing conditions.

A close friend used to fly death pencils and always needed to ensure enough water meth was on board for a G/A prior to an approach into YARM in summer. This required a lot of careful management some days she said.

airbus757
8th Aug 2007, 22:18
This is a symptom of get-home-itis. My advice is not to look for loop-holes when trying to do a flight. There are many ways to twist the rules but in the end you are breaking them. Always fly to the proper minimums and when you can't get in just go to the alternate and have a coffee while the weather gets better. Remember the guys who write the rules did it for a very good reason.

Now having said that, if you are in a situation where there is no choice do whatever it takes to get the plane on the ground.

7

ITCZ
9th Aug 2007, 05:27
Death Pencil, I've had a bit of a think over your question, it is a good one.
If I was in a passenger carrying Cessna 402 or Metro and I had all motors turning happily as I prepared for the approach...

... I would plan to use the lowest MDA available with respect to my all-engines-operating missed approach performance.

If I had suffered and secured an engine failure prior to commencing the approach, I would use a (probably higher) MDA based on my one-inop missed approach performance.

If that MDA was higher than the reported cloud base, then I would be proceeding to an alternate.

This is where your prior preparation and situational awareness kicks in. YPAD details and environment are a little way back in the past for me now, but you have two other aerodromes nearby (YPED and YPPF), but they might be experiencing the same local conditions. YPLC, YWHA, YPAG, The conditions might be better on the other side of the range of hills or the other side of the gulf.

So in a way it comes back to a little bit of alternate planning prior to departure, and a good aide memoir is - Never hold a sh!thole for a sh!thole

Now for the "fun" scenario. You commence the approach with both motors behaving themselves. On the way down to your target MDA, be aware of when you have passed your "single engine" MDA.

If you are not visual at the target MDA, and you commence the missed approach, and one of the motors chooses to quit on you at this point, yep you aint going to make the missed approach gradient. However from studying the chart you know that for the moment there should be a runway beneath you. You can't see it, but that is a nice obstacle free place to be for the moment. You also note from the chart that a 'no circling' zone is displayed from the NE to W quadrants greater than 4 DME. To the W and NW is open ocean.

So you are in a not good place, but you have about a mile or so (translate 30s - 45s) to get the aircraft under control and climbing. I'd then be planning to start a right turn at 15 deg AoB before 3 DME S of AD onto a heading between 220 to 300 and head out over the water. I'd also be conscious that puts me in potential conflict with traffic arriving onto RW05 or overshooting RW23 so I'd be getting on the radio and TELLING the tower my situation and my intended tracking.

Thoughts?

discountinvestigator
9th Aug 2007, 08:43
The design of instrument approach procedures is based on all engines burning and turning. It is the operator's responsibility to ensure that engine-out procedures are provided for the pilots.

In this case, if you can achieve 2.5% after an engine failure, that is what you use. If you happen to fly a 146 around, then use the other figure.

The climb gradients do not start from the Missed Approach Point, they start from the "Start of Climb" point. There is a level segment in between with very reduced obstacle clearance.

Remember what is best practice. You should be following a vertical profile and not diving and driving. Therefore, you need to add your sink allowance into the MDA anyway. Remember to have your own visual descent point if it is not provided for you. Go-around after it unless you want to overrun.

ITCZ
9th Aug 2007, 12:43
Therefore, you need to add your sink allowance into the MDA anyway
Interesting. Not sure what the convention is in Europe, but we Aussies are trained to not 'sink' below an MDA, especially in a circling procedure. Had it hammered into my skull in initial training that you can sink below an RA/DH but not an MDA.:=

Use a rule of thumb such as 1/10th of the RoD to determine the height above MDA where you commence the level off so you don't sink through it. Tolerance in maintaining MDA in our checks is +100FT, -0FT.

Having said that there if it is a database runway approach with a vertical profile, commencing a level off prior to MDA can be counterproductive in the infrequent occasions that the Wx is right at the MDA. you won't bust the MDA but you will immediately put yourself high on approach profile, as you allude to, and very likely not recover the slope within stable approach criteria.

However our friend with the question is flying something with 9 to 19 seats, not 119, and probably jotting down his own vertical profiles on a notepad instead of following a VDI. In which case he might be constructing a profile that gets him to the MDA nicely before the 3deg slope.

RYR-738-JOCKEY
9th Aug 2007, 18:42
Why do people always try to make up their own procedures? Stick to the basics. You've all learnt it at one stage.
Go-around at or above MDA: Do the missed approach procedure. Required climb gradient 2,5% SE. And if there are different MDA's, then check which one's yours for that day. (Weight, pressure altitude++)
Go-around below MDA: Do the contingency procedure (departure), be it straight ahead or an emergency turn procedure. Required climb gradient 2,4% SE. (SID's 3,3%)
K.I.S.S. Keep it simple stupid! Every go-around is a **** up..add an engine failure and some extra workload to figure out where to go next...
Who prepares for the worst anyway? Most guys plan for an early turn-around, or an early check-out, in my world...
There might be cases, where you have to keep several paths in your head at once...but then again, these are normally covered in either specific training/airfield briefs, and you KNOW you gotta prepare.

ITCZ
10th Aug 2007, 06:38
RYR, the chap asking the question is not in Europe flying a 737 or an A320. He is in Australia flying a light twin (<5700kg MTOW) as far as we can tell.

KISS? "Make your explanation as simple as possible, but no simpler." Albert Einstein.

Go-around below MDA: Do the contingency procedure (departure), be it straight ahead or an emergency turn procedure. Required climb gradient 2,4% SE. (SID's 3,3%)

Again, I think our poster does not work for an outfit that produces regulated landing weight charts or contingency procedures.

I'd like to ask you the same question I asked Piltdown Man...

If you are flying any NPA in IMC using a VOR or NDB as track reference, please tell me how you accurately place an aircraft right over the departure end of a runway with a ±150m lateral tolerance?

RYR-738-JOCKEY
10th Aug 2007, 10:43
If you are flying any NPA in IMC using a VOR or NDB as track reference, please tell me how you accurately place an aircraft right over the departure end of a runway with a ±150m lateral tolerance?

Well, if you loose an engine below MDA and you follow the EO departure procedure, you are merely starting your "departure" from an earlier point with speed and altitude as a bonus. Now...tracking precisely will always be difficult. Don't forget that these are only procedures to cover you ON PAPER, and not neccessarily in practice.
The 300m gate you're refferring to, will be equally difficult to hit from a EFATO scenario. Anyway, I'm not expecting any skyscrapers 151m left/right of DER. And regardless of your abilities, I would rather be at 1000 ft, 200m right of DER, than at 35ft, 149m form DER and within the corridor.

ITCZ
10th Aug 2007, 12:24
RVR, I'm not trying to pick fights. This is techlog. Off the cuff doesn't belong here. Nor do "answers" that are simplified to the point of being useless, or dangerous.

The 300m gate you're refferring to, will be equally difficult to hit from a EFATO scenario.

No it isn't. They are designed around the abilities of the average airline pilot, with a margin for error.

The 300m window is based on the practical test standard. EFATO tolerances in proficiency checks are based on a maximum 20 degree swing off heading during the EFATO, with the pilot subsequently containing and controlling the heading within 5 degrees of the target.

Given that you had been tracking the centreline of your 30m/45m/60m wide runway, and the earliest liftoff point calculated off your lightest departure weight, 300m is plenty wide enough -- and not for the ace of the base, but for anybody that passed their proficiency check.

Kleenex is for wiping your nose, and toilet paper is for wiping your backside. EO departure procedures are designed for EFATO, not 1 INOP missed approached. They are predicated on a particular starting point that is easy to achieve off the runway but nearly impossible to achieve in a missed approach in the soup.

An EO departure procedure might be an option in some circumstances, but not always. You would have to study the procedure and the terrain before you thought about using it for a situation for which it was not designed.

It is not just a case of starting higher with more energy. Unless you have really taken a look at the specific location, attempting to follow an EO SID affords no more protection than a racetrack pattern that keeps you in the circling area or turning towards the sea/mudflats/etc.

discountinvestigator
10th Aug 2007, 18:32
To clarify the adding sink to MDA comment.

You should be flying a relatively stable angle and not a dive a drive. So that you do not go below MDA, you have to decide to go-around above MDA. Therefore, you have to add an allowance. Most carriers add 50 feet.

Once you get to this new altitude which is a psudo Decision Altitude, then you call for a decision. At this point, you go-around or not.

Carriers that do not adopt this style of non-precision approach and have an accident may well be open to prosecution for not exhibiting the relevant duty of care.

command
11th Aug 2007, 00:37
yeah tough situation. just do the ILS if its working. If its not and i was assy i would prob use the higher MDA.

john_tullamarine
11th Aug 2007, 08:26
Anyway, I'm not expecting any skyscrapers 151m left/right of DER

In many instances, you should be (trees, hills, poles, etc) ... may I suggest that you have some discussions with your ops eng procedures designers .. you might just frighten yourself into a safer attitude to the subject ...

For those runways which have tiger country on the miss, the operator should have predicated the OEI miss on a procedure designed by the ops engineers. If this is different to the letdown miss, one would have negotiated it with the relevant authority .. more commonly, the ops engineers would have dictated a higher minimum to cover the reduced climb capability.

He/she who just ambles on down to minimums without thinking about these things is an accident in the making .. sooner or later ... if one quits at an embarrassing time.

We should keep in mind, particularly for twins, that the impressive AEO performance oft times lulls pilots into a false sense of security ... when, for OEI at critical conditions ... the bird becomes a definite dog ... and the bumpy bits become very frightening ...

Indeed, in some circumstances where one is in a critical situation, and the failure is late in the final approach, the best risk outcome might well be to fly the approach to the runway .. hence the need that many of us see for hand flying skills which are up to the demands of a blind ILS landing .. not overly difficult with practice .. but near impossible without.