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-   -   Non-Precision Approaches. What does your airline recommend? (https://www.pprune.org/tech-log/9903-non-precision-approaches-what-does-your-airline-recommend.html)

downfourgreen 27th November 2001 20:32

Non-Precision Approaches. What does your airline recommend?
 
Well folks, one more crash and many fatalities during a non-precision approach and nobody knows when authorities will review that outdated procedure to set up a new safer standard in order to avoid future incidents and accidents during the 21st century :(.
Several airlines still recommend to fly exactly the approach chart profile view and its steps, ROD, etc. and everybody knows how hard and dangerous those techniques are for a low speed single engine airplane and I don’t need to tell you how demanding task is to align an MD-11 or any wide-body airplane just a few miles on final during a rainy and windy night at weather minimuns.
I know that some airlines have strict standard procedures for non-precision arrivals with many recommendation and rules to follow based on profile and constant-rate descents after FAF to the MDA or TCH, runway alignments, etc.
Can someone give me a feedback about those operation criteria, including training, wind and rate of descent limits, RNP, etc., beside the Jepp’s charts with a VNAV profile and VDPs?
Thank you fellows...
DN4GR

"While my guitar gently weeps..." G.Harrison

[ 27 November 2001: Message edited by: downfourgreen ]

Hand Solo 28th November 2001 03:49

Don't know how Jepp charts depict NPAs but in my compnay the objective is to fly a constant 3 degree approach path (or the relevant slope). This generally means not levelling at intermediate step altitudes and possibly delaying the final descent beyond the initial approach fix in order to achieve a continous smooth descent through the FAF down to MDA. Training for NPAs is covered in the initial conversion course and recurrent sims, wind limititations are either the aircrafts limits or the (lower) limits of the Captains nerves! Descent rates for all approaches are restricted to less than 3000fpm when descending below MSA+3000, with type specific restrictions on autopilot descent modes to prevent high rates of descent & long engine spool up times close to the ground. Aircraft should be on the stable on the final approach profile by 1000 Radio or a go-around should be considered. If the aircraft is not stable on the profile by 500 radio a go-around is mandatory. On the Airbus we fly the final approach in track/flight path angle mode with the autopilot engaged in bad weather. The 'non-landing' pilot flies the approach with the 'landing pilot' calling out distance to go and height above or below the profile, plus any other pertinent information. The approach is terminated at the MDA if visual contact is not made. It is not permissilbe to fly level at MDA until the Missed Apporach Point is reached.

411A 28th November 2001 06:49

Dive (within reason) and drive...has worked for me for over thirty years in several heavy jets.
The constant descent idea is OK...but sometimes it just does not work.
Some companies just do NOT get the message.
Training is the KEY.

shakespeare 29th November 2001 11:58

411A.

I could not disagree with you more strongly. One sure fire method of upsetting a assymmetric non-precision approach is to use the "step down method". With every thrust change as the a/c levels off there has to be a corresponding input of rudder and then another pitch down to the next step = more power changes and rudder inputs and so it goes on. I have never seen an unstable approach flying a constant rate descent. Auto-pilot in or out!

JAR OPS requires this method to be taught in recurrent sim sessions, and if performed correctly, it is in my opinion by far the safest and most efficient way to fly a non-precision approach.

Irrespective of whether it has a 3 degree or 4 degree profile, VOR/DME, NDB/DME, constant rate works every time. Interestingly enough, if you take away the DME forcing the lads to use the tear drop procedure from overhead the navaid, they don't need to use step down at all. If it works here it should work on a straight in approach, and it does!

The trouble in many airlines is that pilots have not recieved thorough non-precision approach training, and as a result don't have a good understanding of flying the procedures correctly.

As you said, "TRAINING IS THE KEY".

[ 29 November 2001: Message edited by: shakespeare ]

sabenapilot 29th November 2001 15:49

On aircraft with a FPA (Flight Path Angle) on the autopilot, European JAR-OPS requires that it is used iso the usual V/S mode.

This means you simply track the radial inbound and set the published FPA (for instance 3.7%). The plane will then descent on a virtual glideslope towards the runway once its horizontal path intersects with the virtual glidslope.
During the approach you'll see the autopilot will modulate the V/S in function of the (normally deceasing) GS and you'll skim the tops (if any) of the intermediate stepdowns.

When apporaching the MDA, no level flight till the MAP is made; instead the MDA must be considered as a DA and a go-around must be executed! This poses no big problem (for instance a too early immediate left turn), because of the design of the FPA mode, which will make sure the MDA will always be reached very shortly before (0.2NM at the max) or on the MAP itself (at the very latest).

Also note that in this FPA technique no VDP (Visual Descent Point) is to be used by the crew, but rather do they use the normal call outs and procedures as for a precision approach.

Quite clever from Airbus, isn't it?
BTW, does anybody know if you can do this FPA technique on the B737NG or B777 as well?

moggie 30th November 2001 01:00

I have to agree with all of you - except 411A.

What do you fly, 411A, and who for? I for one would hate to be on it with your "dive and drive" approach. The bigger the aeroplane the less safe that style becomes - large adjustments to ROD near the ground are asking for trouble.

Hand Solo's SOP sounds just like the one I spend most of my time teaching pilots for a very big airline and I can tell you that the secret to a safe NPA is a stabilised descent rate and small adjustments - especially if dealing with aeroplanes at the lower-tech end of the market. It's all about situational awareness and mutual monitoring on NPA's and stepped approaches push up the workload, reducing SA and the ability of the Non-Handling Pilot to monitor what is going on.

Yes, a pilot should be able to handle a stepped approach, by why make life difficult.
They always say that the superior pilot uses his superior judgement to avoid getting into positions that require the use of his superior skill.

In addition, the airlines that I train for apply a factor to the MDA to turn it into a DA so that the same decision making and handling methods are used for precision and non-precision approaches. This formalises the procedure that you would have to go through anyway and does not reduce the likelihood of getting in.

downfourgreen 30th November 2001 01:41

A nice debate.
In accordance with FAR and ICAO PANS OPS criteria, an airplane is not authorized to fly below MDA until reaching the required visual reference or begin a missed approach prior to the published missed approach point.
Therefore, based on your opinions I have some doubts and would like some help:
Almost everybody agrees that a constant-rate descent is safer and comfortable than a step down approach, but I’m little confused when, for example, an airplane has to reach a significant high MDA (e.g. 600ft AGL). During a profile descent, the pilots are waiting for visual cues to complete their approach, if the crew complies with JAR-OPS I understood that they should reach MDA at point where the airplane could complete a stabilized approach (3 degree, 800 fpm, at least), and in case of no visual contact or not stabilized they must start a go-around promptly, without stopping at MDA. However, if the MAP is over the VOR, some miles ahead, how and where do the pilots begin the missed approach maneuver? Don’t they need to keep the airplane at MDA until MAP (FAR and ICAO rules)?
How do you define the initial point to start a final descent based on a 3-degree profile angle until MDA when no information is provided on approach chart? Is it only an FMC calculation?
Thanks in advance

FlapsOne 30th November 2001 02:09

In my company (737)- notional 3 degree (adjusted if necessary to make or not below step heights) flown in VS. MDA +50' is then used as Company Decision Alt. If no vis ref at Co DA then go around as if on precision approach.

We do not fly a 737 level at MDA to MAP. The thought of doing that with one donk out is horrifying!

TechFly 30th November 2001 02:21

Tks to everybody for apporting their pilot techniques!

I think Moggie was giving two keywords: Situational Aw. & Monitoring.

As we all know sometimes it is possible to reach the same objective with different ways.

In this case I prefer to adhere for a constant descent (as close as possible to the std 3° angle) trying to figure out the VDP with reference to "Dist. from RWY" vs. "cloud base".

PNF will give the deviations from the published std profile (in terms of ft).

For what is concerning the MAPt I look at it in particular for the separation from obstacle in case of a GA with an engine failure.

Looking for your comments.

Cheers.

Fly safe & enjoy life.

411A 30th November 2001 02:46

FlapsOne, better stick to the UK. If you came to the USA and could NOT fly level at MDA (and not the +50 nonsense)with an engine out, you would FAIL your FAA type ride.
Its called airmanship...and handling ability...and if you ain't got it, don't apply.

Softons_Mum 30th November 2001 04:12

Using the continuous 3 degree descent procedure, u treat the MDA as a DA - if the required visual reference is not there you go around. In terms of if the missed approach point if it is some distance ahead, you continue the tracking as required to reach the missed approach point whilst climbing away, then follow the standard missed approach when reaching the specified point...or as directed by ATC .... ;)

Softons_Mum 30th November 2001 04:18

in terms of 411as method of flying level - it may well be practical (or required - some procedures require a visual level segment after reaching the missed approach fix) - however in many cases it is not practical - why fly level along the MDA to the missed approach point if you know that you cant descend safely to the runway with appropriate rates of descent and speeds when you reach that point? in most companys i would say that it would be viewed very poorly doing greater than 1000fpm below 1000 feet.......

LevelFive 30th November 2001 05:01

DN4GR,
For non-precision approaches – ceiling less than 1,000feet or visibility less than 3 statute miles, the first officer must fly using the autopilot while the captain seeks visual reference with the runway, or the captain can manually fly using the HGS system. FLAPS must be 40 by the final approach fix. Max descent rate 1,200 fpm. Minimum descent rate 1,000 fpm. The captain does the landing. Sim check is get down, drive in and descend as soon as runway is in sight. Wind limits – 70 kts peak gust headwind, max crosswind 35 kts, max tailwind 10/15 kts depending on model.

2daddies 30th November 2001 05:45

411A,
Mate, I promise you that I can fly at MDA + 50 - 0 (and don't give me any of that "I can maintain an altitude to within 10 feet" rubbish - you bloody well CANNOT and you know it!) with one-engine inoperative and without falling into a slanging match about our respective country's standards I'm sure you'll find that if I can pass an Australian Multi-Engine Command Instrument Rating test AND a base-check with my airline I can pass an FAA equivalent - it's what I get paid to do.

My point though is: why dive and drive if you don't have to? It's can be uncomfortable for passengers (descent rates/markedly changing engine note) , it makes speed, energy and configuration management difficult, it places unnecessary power demands on the engines and quite frankly the closer I get to the ground the more reluctant I am to dive towards it - distractions and mistakes happen and if you make an error in a nice constant 3 degree descent chances are you'll have A LOT more time to fix it than if you're driving down to the next step at 3000 fpm (not to mention avoiding triggering the GPWS).

Airmpanship encompasses many elements of flying - but basically don't do something if there's an easier and SAFER way of getting the job done!

[ 30 November 2001: Message edited by: 2daddies ]

[ 30 November 2001: Message edited by: 2daddies ]

411A 30th November 2001 08:14

You missed the point entirely 2daddies.... the FAA wants to see a NP approach flown to the missed approach point, NOT a miss upon reaching MDA. If you cannot do this, level at MDA, with an engine out, it's pink slip time, simple as that. It's called maximum time at MDA to be able to see the runway or approach lights. Diving at 3000 ft/min is certainly not required, 800-1000 generally works fine. If an airline wants to impose additional restrictions, that is up to them, I mentioned the FAA requirement for the rating. Does not necessarly apply to everyday plain vanilla line ops. Those of us trained long ago use the dive&drive method because it works, for us anyway. For the more "junior" guys, new to line ops, the constant descent method may well be better suited. Different strokes for different folks :D

CaptA320 30th November 2001 11:41

411A I agree that in the old days, in fact not so long ago at all the method of flying a NPA was the dive and drive, most of us were trained in this method throughout our initial training. However this has changed as the constant rate of descent procedure has been found to be both safer and more comfortable for pax. When I did my intitial pilot training there was no such thing as CRM...get my point.
The issue here is not if a pilot has the ability to fly MDA+50, despite the fact that most of us had to display that in order to get our ATP tickets, line flying has little to do with an FAA check ride. Major airlines around the world have recognized that the "stablized" approach not only increases situational awareness but also is safer.
The constant rate of descent method is no so widely recognized that Jepps decided to publish on their charts the dme crossing altitudes for the portion beyond the FAF.
The way we train pilots is two fold.
If the chart has the published dme/altitude profile then it is recommended to be used in conjunction with the published gradient which should be converted to FPA.
If the chart does not have published dme altitudes then the crew should calculate the profile of descent by first looking at the VOR (lets say), calculating its displacement from threshold (when on threshlod what should my dme read) then knowing we want to cross the threshold at 50 feet work back to platform altitude based of the gradient.
So if the VOR is 1 mile before the threshold and threshold elevation is 60 and platform altitude for the approach is 2000ft with a gradient of 5 it would be as follows.

At threshold (-1DME) we should be at 110ft at the VOR we should be at 410ft, at 1DME 710ft, at 2DME 1010ft, at 3DME 1310, at 4DME 1610ft, at 5DME 1910, at 5.3DME 2000ft.
Now this profile must be compared with the chart to ensure it complies with any DME/Altitude restrictions, it also complies with the FAF (FAF cannot be less that 5.3DME) and at MDA the pilot must have obviously visual contact to continue.

sabenapilot 30th November 2001 14:49

411A,
you say: the FAA wants to see a NPA flown to the missed approach point, NOT a miss upon reaching MDA.
In other words: If you reach the MDA before your MAP, you have to fly level at MDA till the MAP before starting the missed approach.


First of all:
purely technically speaking (based on European JAR-OPS); after descending to the MDA on a NPA, you do NOT have to stay level at MDA till the MAP! An MDA is nothing more then a MINIMUM, so there is no rule wharsoever preventing you from already starting to climb up again. However, you are correct on that you have to stay on the appraoch track till the MAP. Only then are you allowed to initiate any turn (if the missed approach calls for that of course...)

Second remark:
I do not know what plane you fly, but it clearly is no airbus with FPA (Flight Path Angle), because then you'd know this discussion of yours is purely theoretical...
FPA allows you to fly a continuous descent NPA, skimming all tops of any intermediate stepdowns (when used correctly), and reaching your MDA at any selected point!
If you use your MAP for this selected point, then your MDA is nothing more then a virtual DH and a go around MUST be flown upon reaching the altitude.
If you work out and use a VDP however, then you may indeed continue your approach by flying level to the MAP, but as the subsequent descent from that MDA at MAP is no longer on your smooth and continuous descent profile, you will easily end up with all kinds of unpleasant audio warnings like: SINK RATE, TOO LOW... TERRAIN etc.. Not really something I'd like to hear on a NPA appoach in poor visibility (only RWY lights in sight, no RWY itself for instance...)
BTW- If Airbus stongly advises against any level flight at MDA on a NPA approach for all these reasons, then why try to be sharper then these highly qualified guys?

411A 1st December 2001 01:34

Well sabenapilot, the level flight required at MDA is a REQUIREMENT for the FAA rating, what the airline ops specs says about this (in normal line flying) is quite another. If the individual airline wants to treat an MDA as a DA, that is their option. Seems quite unnecessary to me. And, so is the +50' business added to MDA...more European nonsense. Either you can fly accurately, or you cannot, rather simple really... :rolleyes:

RatherBeFlying 1st December 2001 06:04

In these wonderful days of FMCs, you can project a straight slope back from the screen height at the threshold to stay above all the step-down fixes and convert the MDA to a DH -- just make sure you key it in right and monitor those step-down fixes.

The first instrument approaches were non-precision approaches. NDBs were new fangled technology and the criteria were designed around the DC-3 -- and still are except that the circling minima were given widened bands as approach speeds increased.

On my very first IFR flight test, as the stopwatch ran out the time on an NDB approach, I lifted my hood at the MAP to find the runway half a mile off to my left after what looked to me like a good tracking of the course -- and passed! I'd really want to know very well the guy who swung the compass before doing an NDB for real -- today you take along a GPS.

411A 1st December 2001 06:12

Yes, and those GPS approaches can be very accurate...why is it that this very useful aid has not found wider acceptance in the EU?

[ 01 December 2001: Message edited by: 411A ]

Hand Solo 1st December 2001 19:50

Because its controlled by the American military and they can't be trusted not to turn it off when we need it. Thats why. Could make life very difficult if they invoked SCATANA mark 2 and shut off the GPS.

BEagle 1st December 2001 20:50

Whereas at DA a decision is made (which will involve the aeroplane descending briefly below DA before go-around is achieved), as we all know, at MDA the aeroplane must not descend further until the appropriate visual references are achieved.

So for those youngsters not trained to fly level at MDA and who therefore treat MDA as DA, an extra factor must be built in to ensure that the aeroplane does not descend below MDA when go-around is initiated. Hence for those who insist on using the DA technique on a non-precision approach, an extra 50 ft at least must be added to MDA to compensate.

Trainig and practice are needed to fly a 'dive and drive' - but commercial pressures rarely allow such luxuries these days.

[ 01 December 2001: Message edited by: BEagle ]

Kingpilot 1st December 2001 21:48

411a-

The Flight safety foundation has done a tremendous amount of work on the CFIT problem and have identified the "dive and drive" technique as contributing to the high risk of NPAs. They recommend a constant rate of descent, even if it lessens the chances of getting in. The FSF is, I believe, US based, so this is not just a European thing. Both you and the FAA need to roll with the times here. If you are interested take a look at www.flightsafety.org for plenty of excellent research into CFIT and Approach and landing accidents. Look for the flightsafety digest from a couple of years back, it is a .pdf download.

411A 1st December 2001 23:40

Kingpilot--
Yes, quite familar with the FSF...who am I to say they are wrong, just that in the past crews were trained dive&drive and I just cannot help thinking that they were/are better trained IMHO.

BEagle--
Yes would agree that if an MDA is treated as a DA, an allowance is needed.
I was involved in training years ago at an asian carrier, and the new F/O's were trained in the aircraft (B707, not an easy acft for the inexperienced) and they had no difficulty with flying level at MDA with an engine inop...but then, fuel was cheaper. They normally received at least 40 landings before being released to the line. With this practice, their handling skills were very good.

fms146 2nd December 2001 00:04

Very interesting reading this debate and it highlights an area of dificulty I had when comming into the Airline environment from GA where NPA's are the rule rather than the exeption...On a dark night in winter flying freight on my own into some god foresaken place in the middle of nowhere I got into the habit of planning a constant rate decent to the MDA..it made life a lot easier I assure you and I felt no need to prove I could fly to within 50 ft of any intermeadiate level.

I know from previous posts that 411A and 2daddies are very experienced training pilots on heavy aircraft..with two very different opinions about how the NPA should be carried out..but just imagine how hard it is on a new FO when he flies captains of differing opinions and you get the "What are you doing" when all you are doing is what the other guy wanted.

Now who am I flying with today...

411A 2nd December 2001 00:16

Well fms146, that can be a real problem.
I have noticed DE Captains joining an airline and then adopting their own procedures (from another carrier)and this drives the F/O's to distraction.
A new Captain should let the F/O follow the airline standard operating procedures when he/she is PF and NOT try to change the plot.

Dan Winterland 2nd December 2001 03:22

The MDA is just that - a minimum. If you fly the constant descent profile in a very heavy aircraft, say a 747, you will bust the minima if you TOGA at MDA. For that reason, my the Jepp plates my company uses all have an extra 50' added to the NPA MDAs.

I used to fly with BEagle (in fact checking my logbook, he did 5 of my 6 IRs on that aircraft!) The company policy then was to descend slightly below the notional 3 degree GP and level off to make the MAP at the MDA (legal on all NPAs except SRAs which have lower minima based on the notional 3 degree GP). This is fine if the aircraft can do it, and you stay in currency on that type of approach - we used to have hours allocated for currency training on the aircraft (not the Sim) and had to do one of these approaches every two months. But now I'm flying a much heavier aircraft and rarely flying NPAs - the constant descent and a 50 ft buffer make good sense.

Kingpilot 2nd December 2001 09:21

411a, I still cannot agree with you. IMHO the better trained pilot is the one who has been taught the safest way of doing the approach. Perhaps your method REQUIRES more skill but who is to say that pilots trained in the constant ROD would not be able to fly level at MDA if they were required to do so? It has been said before but I will say it again, a good pilot uses his superior judgement in order to avoid having to demonstrate his superior skill.

411A 2nd December 2001 10:17

Well Kingpilot, you are certainly entitled to your opinion, just as I am to mine.
Those airlines who use MDA=DA+50' and a constant descent certainly have their reasons, although I would not necessarily agree...but hey, that's what makes a debate.
All good fun.
What ever you do, be safe....as those non-precision approaches are not always easy.
Many times there are traps for the unwary.

RedUnderTheBed 2nd December 2001 13:07

Interesting?
First off - using 'dive & drive', steps & level MDAs to MAP etc can be very hairy in a wide-body, the pitch changes are horrendous, even if you're name is Chuck with a 'Y'. Not nice in the sim and even less nice with 200, 300, 400+ trusting souls on board. Piece of cake in a small aircraft with in-line thrust engines though.
2: Treating MDA as a DA or DH is definitely fail material in NZ. The lag of the go around, especially with high by-pass fans, means you sink below MDA! Get out of that one Bloggs!
And, finally, a true story:
Some years ago I was going into Hong Kong when Kai Tak (ah!! the nostalgia) was the joint. The IGS (off-set ILS) was U/S and the favoured approach was a TNDB across HK Harbour AT NIGHT - stirring stuff! Not long after we checked in with HK ATC a United jet called up and when advised of the approach to be flown there was a 'stand-by' followed shortly by a request for vectors to CKS in Taiwan as he "...didn't have that approach in the can."
There was some harrumpphing on my flight deck until it was pointed out that he was probably the most professional pilot in the area that night.
We got in on our TNDB at night OK, but I still wonder... :confused:

2daddies 2nd December 2001 15:21

I get the impression that there may be a touch of confusion arising from the dual discussions of "dive & drive" Vs. "continuous descent" and MDA Vs. DA.

Legally (no matter how you get down to the minima) an MDA is an absolute floor - it MUST NOT be descended below until all criteria for a visual approach/ circling and landing are met, while a DA is just that - an altitude at which a decision MUST be made. Allowances are made for descending below that altitude if the approach is discontinued.

These rules are incontrovertable.

411A, after reading some of your ensuing posts I'm beginning to see your point a little more clearly and I do agree with it to a certain extent - the longest amount of time spent at the minima does give you the best chance of becoming visual and executing a successful landing. But bearing in mind that legally you must remain at the MDA (or above) until both visual AND established inside the circling area, I still fail to see the point of diving to that minima miles from the airport. Why not just create a constant descent to place you at the correct altitude coincident with the circling area (to be maintained until the MAPT)?

fms146, 411A and I clearly do come from different schools on the issue, but I'd like to think that if we worked for the same airline we'd adopt and practice the same procedure - the one which the airline determines for us. Individuality is an asset at certain times, but not when trying to conduct a single-engine non-precision circling approach to an airfield in marginal conditions!

P.S - fms, you flatter me! I'm actually nothing more than an humble FO with strong opinions on the topic, so I can sympathise with you about flying with Captains who like to run to their own rules. Thankfully, there aren't many where I work now! :D

Chimbu chuckles 2nd December 2001 18:20

Seems to me you're all missing a few important points.

1/. Dive and Drive has lost favour for one very important reason. It's a lot less safe than a constant profile. In any aircraft let alone Transport Cat Jets.

2/. If the NPA you are flying is a runway approach you'll fly to the MDA and if not visual go around immediately. WHY? Because 99% of the time the MAP is at the aid and the aid is to close to the runway to make the straight in approach from the MAP. You cannot circle from that minima so there is no reason to hang around. The absolute safest way to fly these types of approach in heavy aircraft is to fly a constant profile to the MDA.

3/. If you're flying an NPA that is not a runway approach you descend to the higher circling minima and at the MAP decide whether you have the criteria to circle. In my opinion there is no good reason to get down early for a better look because what the ceiling/vis etc is 3nm from the MAP is not as relevant as that from the MAP onwards in the piece of sky you will be circling in! Thus a constant profile descent to a point say 2nm before the MAP should be sufficient to level the aircraft, have a look, decide and then GA if not visual. The other risk that this avoids is when you get 'visual' at the edge of the circling area and descend further to stay visual before actually sighting the runway, and then subsequently lose visual reference, requiring a GA from below MDA and possibly offset somewhat towards the edge of 'protected airspace'.

I spent years flying NPAs for real in everything from Islanders to F28s and Bae146s and the dive and drive is only practiced by old and bolds who refuse to change, for no other reason than they perceive their way as the way "real pilots do it", or "that's the way we did it in the good old days". They usually fail to remember that they were in a DC3 or some such.

The NPA I fly most often these days is the Kathmandu VOR/DME and you can bet your ar$e that I have the relevant profile written on the plate, there is simply no safer, more predictable, and for 411a, more professional way of flying that, or any other NPA.

411a the reasons CRM and descent profiles have evolved (among other things) is because the way you 'old guys' did it in the 'good old days' was not the best way it could be done! Certainly not in the equipment that has prevailed in airlines of the last 30+ years! I suspect that you are retired now anyway, there is no way that any airline C&T department would tolerate you diving and driving on your sim checks these days!

Chuck.(C&T Dassault Falcon 200)

Scando 2nd December 2001 21:05

Some time ago I read an article on CFIT. A nice setup for a CFIT is a non prec app in IMC and/or night conditions, into an airport surrounded by high terrain. This setup presents itself on a fairly regular basis in my part of the world.
Dive and drive = multiple level offs = multiple possibilities for level busts = multiple possibilities of CFIT. Stating the obvious: MDA is not the only place you need to level off, failure to do so at any minimum (hard) altitudes during the app can kill you.
When, a few years back, we were retrained for the constant angle/rate approach, instructors had very few problems doing so. They found out that was precisely what most linepilots had been doing all along. It was considered poor airmanship to level off more than absolutely neccessary, so we tried to fly NPA's just touching the minimum altitudes. Which is basically what a constant angle approach is all about.
Treating MDA as your DA in this scenario makes sense. You will touch MDA very close to your DP, and if not contact, go around. 35´ added (in our the procedure) for sink through. By treating the NPA as an ILS, we have made the procedure easier.
Dive and drive works. Constant angle approaches, to me, just seem like a step in the right direction. Safer.
I would really hate to have an engine seizure when level at 200 ft agl, IMC, in a high thrust, landing config.

411A 3rd December 2001 00:15

Would agree that the constant descent, go-around immediately at MDA+50'.... is generally fine for everyday ops.
However, there are times when you have to be down and dirty at MDA to see the runway.
Go to the alternate...well yes but suppose you ARE at your alternate or your alternate has gone below minimums, and you MUST make the most of your situation. If the "fly level at MDA" until the field is sighted is not practiced in the sim (yes, even with an engine out) and the particular situation demands that this be done before dry tanks...well you would be up the creek without a paddle, or SOL.
Or, take another situation...on approach to the the old HKG airport, IGS trips off (very heavy rain) and the only other approach is the CC NDB. This particular approach requires crossing CC NDB at 1500', descending to (as I recall) 745'msl and then tracking for 10 miles toward Stonecutters NDB where a right 130 degree turn is required toward RW NDB and the runway. If you tried the "constant descent, miss at MDA+50' scenario, you would never see the runway. Extreme case you say, well yes but there are many non-precision approaches where if you do not fly level at MDA....the runway would never be sighted.
This is why the FAA requires level flight at MDA to be demonstrated, and yes, with an engine out. No one said it was always going to be easy at the pointed end.

maxalt 3rd December 2001 05:42


Go to the alternate...well yes but suppose you ARE at your alternate or your alternate has gone below minimums, and you MUST make the most of your situation.
411A, The superior pilot uses his superior judgement in order to never have to demonstrate his superior skills. :D

411A 3rd December 2001 07:29

maxalt---
Your superior judgement....controls the weather, blocked runways, navaid failure, or one of the very many other variables?
Hope you remain so blessed....many others do not have your good fortune.
Better let your Captain do the thinking :D

RedUnderTheBed 3rd December 2001 08:10

411A
Yup - flown that approach at night in a B747; what's the OCL between CC & Stonecutters with all those ships' masts, derricks etc? Doesn't bear thinking about really!
I think the essence of ANY approach, particularly in large aircraft, is that it is stable. A problem with levelling off at MDA and flying to/through the descent point for the runway is losing the stable approach at low level and THEN trying to re-establish it before touch-down, that can be feat,especially when acquiring the runway late, and has lead to heavy landings or worse.
I take the point on contingencies but I think the comment of maxalt calls to mind another tried and true maxim: "The only time you've got too much gas is when you're on fire!"
If everywhere is on minima then have enough gas to land somewhere easy.
:D

moggie 3rd December 2001 12:24

Dan Winterland

We who advocate the stabilised approach are NOT syaing that you should hit TOGA at MDA - quite the reverse. If you read my first post you will see that on of the airlines for which I train pilots calculates it own DA from the MDA plus a factor to allow for the dip below when the TOGA button is hit (or even manual go-around is commenced!!!!!!!!!!). This is typically 50-60' for a B737. Therefore, a state published 610' MDA becomes a company 660' DA (for example). Then if the go-around is coimmenced, you will not go below MDA. This keeps you safe and legal. This airline, by the way, has an enviable safety record and has not had an accident on NPAs in over 40 years.

If you level at MDA (maybe 400' above the threshold) and track to the MAPt, what do you do when you see the runway when you are crossing the threshold 400 up? What you probably do is go around because if the vis/cloudbase were too poor to see before MDA then they are too poor for a circling approach. Nothing has been gained but safety and fuel reserves have been compromised by an unnecessary level off.

411A you say you trained pilots in Asia to "dive and drive". However, we only have to look at the safety record of Korean Airlines and China Airlines to see that this kind of high workload approach is not a great idea.

maxalt 3rd December 2001 16:59

411A, I believe it was Ernie Gann who wrote:


Always keep an out in your back pocket.
Couldn't have put it better myself. ;D

[ 03 December 2001: Message edited by: maxalt ]

TechFly 4th December 2001 02:08

With respect for the MDA flyers I think that 3° descent is the only way to "standardize" the general XX company for a safe and stabilized approach.

This conclusion comes from many years of CRM & studies of pilot technique on NPA.

It is not wrong to use MDA level for a look but it is "recommended" the std 3° calculation (if the Jepp. chart doesn't depict DME/alts).

We can continue speaking a lot about IF .. Then... but the calculation of fuel should include allowances so it not correct, for my part, to generalize the NPA procedure for the last shot.

Cheers.

Fly safe & enjoy life


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