Decent below platform altitude

[mad_jock]

Didn't know if to put this under ATC or Questions but here goes.


On a none prescion approach eg VOR/DME there is a level prescribed for the start of the final approach eg 3000ft then on the plate your FAF is denoted which some call "top of drop" where apon you start decending on profile and you call your altitude v's DME to keep profile

Now recently At MAN we were getting vectored to the VOR/DME and cleared down to below the platform altitude after getting the intercept turn. We did query it but Director at MAN isn't really the place to be discussing such things and as were visual with the papis we didn't push it.

Now I have always been taught to expect the platform height then at the FAF to decend. I have had a look through my notes and found nothing to say to expect anything else.

Can anyone explain the rules about this?

And for the pilots reading i presume we can just fudge a value for when to start decending off the Alt v's DME table or 3*DME or such like. So does that mean we can except a below profile intercept aka same as ILS but we can we accept one from higher and again use 3*DME to fudge a DME to start to decend.


MJ

[Khaosai]

Fit like min,
seems that it happens in most parts of the world. I do not think that there is anything wrong/illegal with starting off at an altitude different from the platform, however in IMC you need to be very careful on where you commence descent. Ideally starting from platform is slightly easier due to having briefed it etc. With the advent of VNAV approaches the machine takes care of any non standard levels. Would suggest to any ATC, if other than an ILS please put us at the published altitude on an NPA. Rgds.

[Spitoon]

First off, as a controller, I'm not aware of any rules that say I have to vector an aircraft to intercept an approach at any particular altitude.

What I want to do is get it onto the approach in a reasonable manner and range and make sure the pilot understands where he or she is on the way there. If it's not an ILS approach I'll take extra care to give an accurate range check as the aircraft intercepts the final approach track or whatever. Whilst I'm vectoring, I'm also responsible for keeping aircraft separated and for the aircraft's terrain clearance.

At pretty much all the airports that I've worked at (as far as I can recall), I've been able to drop aircraft on radar lower than I could clear them procedurally - this is not unreasonable when you think about it I guess. Occasionally a pilot complains but that's usually if I've stuffed up the vectoring and given a really long or really short final!

I would guess that aircraft are vectored onto approaches below the level that would be used if they were under procedural control many hundreds of times a day. If it concerns you for any reason, just tell the controller - every controller I've ever worked with will try to accommodate such requets if given enough warning.

[Chilli Monster]

In a way you've answered your own question.

Platform altitude, and the approach plate, is there for a wholly non radar vectored approach. PANS-OPS criteria are used to write these procedures, and that's what decides what platform altitude is.

However - you were being radar vectored to intercept the final approach course for the VOR/DME approach. The Controller can, 9 times out of 10, bring you lower than platform altitude using his Radar Vectoring chart.

It's then up to you to work out, using the plate, at what point your new descent point will be to continue down the nominal glideslope as printed on the plate.

[benedictus]

Where I work, radar vectors to vor/dme approach, I can only descend to 3500ft using radar, the top of descent for the procedure is 2900ft, so procedurally it is safe to descend to 2900ft for the approach, but because of terrain issues I cannot descent below 3500ft.

The way round it in my book is to get you established inbound a little further out that normal, you call established inbound and I give you descent with th eprocedure, thereby releasing you for descent to 2900ft to commence the procedure.

There was something in CHIRP about this a while back, can't quite remember when and what was said though

[citrusgal]

If you are really worried about it, ask the controller for decent to the platform altitude only, never had a complaint from a controller for doing so and saves having to do the math.

[mad_jock]

I agree normall we could ask for what we like but MAN on SRO it not really an option and quite rightly so. Its not having a go at the peeps i am just trying to get my head round another bit of ....

Its another case of pilots getting taught one thing then ATC thinks things are done different.

Its the whole sim thing of us being taught to say standby and ATC expecting us to tell them the whole story.

MJ

[Phoenix_X]

I've discussed with some ATC controllers around the world (on the ground, not the RT) and most seem to say they are not really aware of platform altitudes.
Chilli Monster, while in essence you are right, there are an increased number of incidents with non-precision approaches, many aircraft descending at the wrong place at the wrong time.
Being vectored to different altitudes than the one expected, could be a contributing factor for future and past incidents.

This is not the first time this comes up, so maybe this should be considered more seriously if we want to reduce non-precision landing incidents.

[Spitoon]

m_j, you say that pilots are taught to expect the platform height then at the FAF to descend. Is this a common practice thing or is it written down somewhere authoritive? I'm thinking of a CAP or ICAO doc.

[flower]

I am aware of Platform heights/altitudes as we do procedural approach training at our airfield. I was taught to descend aircraft when vectoring, to platform height/altitude if possible but if the aircraft is to get a shorter final than that on a procedural approach descend below the platform height/altitude.
To be honest until i arrived here i hadn't used platform heights at any other airfield, but then we didn't do procedural approaches as a rule at them.

[Spiney Norman]

mad_jock.
Speaking as a Manchester Approach ATCO. Personally I always use the platform altitude/height, and the FAP range when vectoring for the VOR/DME approach. The idea being that you get a period of level flight before commencing final descent, and the altitude/height will correspond with what you're expecting from the approach plate. Over the years I've trained a lot of people at Manch and have always taught the same method. However, there's nothing in any of our documentation, MATS pt1 or 2 that says it has to be done this way, so this isn't a criticism of the Director you had the other day who vectored you to an intermediate range and altitude. Interestingly the thing we find more of a problem is when speed control is required to hold final approach spacing, which is often not possible when flying the VOR/DME approach.

Spiney

[mad_jock]

Spit i don't know if it is written anywhere and its proberly isn't. And to be honest there are so many things that we get taught as normal operating procedures during our intial IR and further training which are never documented (or if it is I don't know where) but they have a way of becoming folk law of the way things are done.

In my limited experence its not common for you not to be place at the platform height. Hence my question. And as someone else has pointed out on a nice day on a non-precision approach its not really an issue but on a crap day its an additional work load which we could be really be doing without.

MJ

[ifleeplanes]

From a pilots perspective we brief the approach before top of decent and brief the NPA as it will be flown from the platform altitude.
If we are not given the platform altitude our decent profile from the final altiude given become a guesstimate. Since we also usualy configure the aircraft with regard to the expected FAF and that is expected at a specific altitudeat a specific DME or time point IE for example 2NM before FAF gear down F15 landing checks/1nm MDA set/0.5 nm F30-F40/ FAF decend. If we are not at that point it makes our jobs ALOT more difficult and at a time in flight when we least need it, we are very busy at this point.
Since the majority of incidents of CFIT are within 5 miles of the airfield and often with the aircraft decending at the correct rate, it indicates that the point at which the aircraft started the final decent was incorrect. This can EASILY be due to being given an incorrect platform altitude and thus a guess of the range to start the decent (it so easy to incorrectly estimate decent point when at a high intensity point in the flight when your doing 6 things at once).
If we want to keep things simple and most importantly SAFE then it is in both the pilots and controllers interest to not increase workload at a safty critical stage of flight. PLEASE PUT US AT THE PLATFORM ALTITUDE WE EXPECT. EQUALY IF WE AS PILOTS ARE NOT HAPPY WE HAVE THE FINAL SAY, REQUEST THE PLATFORM ALTITUDE.

[Spitoon]

m_j et al, this is a very intersting debate and, as they say, you learn something every day.

As I say, I was never taught to vector at platform altitude but clearly some other controllers have. Equally, some pilots don't seem too bothered whilst others have been taught to expect it. Neither pilots or controllers can point at a definitive statement but it would seem good practice to descend aircraft to platform altitude when vectoring them to intercept a NPA - I shall certainly do so in future.

[Keygrip]

I did - in an R/T lull - ask a controller this very question when, to my great surprise, he vectored me in for an approach below platform and below MSA.

Response was (words to the effect of) "WE can do what we like when you are radar vectored".

When subsequently asked about comms failure, in IMC, at such low level, the words "angel" and "homesick" were mentioned.

In fairness to Manchester (the English one, not New Hampshire), when doing my initial night rating (as it was called then) training, an approach controller did ask me to fly a radar heading and then, after my acknowledgement, came back with the phrase, "Be advised that in the event of communications failure this track is not terrain safe".

[mad_jock]

I don't think you should completly write it out of your skill set spitoon. And i think it depends on the machine about how much extra work it is. Which is why some pilots have more stronger views about it more than others.

Time permitting give the option of a shorter final with decent below or the platform height or give the heads up before dropping us. If we know about it decending on the down wind or before turning base the PNF has enough time to work it out and also it dosn't come as a surprise later on in a high work load phase of flight. Or if you make yourself a chart up with the DME ranges for the different altitudes you drop us to. eg Decend alt 2200ft, cleared to decend with the procedure recommended at 5.8DME, Contact tower ......

Or i suppose if you all use the same radar vector decent alt get an extra check height put on the plate or a note.

But telling the pilots to expect it early if you require to drop us below platform would certainly be a huge help. And I must admit now I know its not a cert, it won't come as a surprise so the work load won't be as much next time.

MJ

[ifleeplanes]

Decent below the platform on a precision approach is fine. On a NPA it can and has caused problems ie CFIT. For the sake of saving 30 secs on an approach by having a slightly shorter final its just not worth it.

A NPA in good weather is great, but we practice in the good weather for when its not so good. KISS is a great addage.

An example..... the platform is 2500 ft and FAF is 7.5nm. We get decended to 2000 ft now we know its approx 6 nm but today its a 3.6 degree decent...the cabin buzzes us , the wind is gusting, the cloud base is on minimums, expect a late landing clearance.....damn I have miscalculated decended too early/late. Adjust decent to catch it up, now the airspeed is increasing, Flap load limiting trips in since its gusty and we have picked up a few extra knots here too....SINK RATE SINK RATE/ TOO LOW GEAR....Sounds oh so easy sat here in the cold light of day. As always its not one item that leads to an accident but a chain of events, break the chain and it doesnt happen. Easy to break this chain, just put us at the platform take some of the thinking out of the equation.

[mad_jock]

Yep your right ifleeplanes.

It really isn't worth the extra hassel.

[Fox Alpha]

For any others who find this thread hard work to read, I can now reveal that it is all written in secret code. Use the following technique to "break" the code:

For "none precsion" read NON-PRECISION
For "your" read YOU'RE
For "decent" read DESCENT
For "decend" read DESCEND
For "proberly" read PROBABLY
For "its" read IT'S
For "completly" read COMPLETELY
For "hassel" read HASSLE

[ifleeplanes]

Get a life Fox Alpha or a job as an English teacher..

[eightyknots]

ifleeplanes

Why don't you and your illiterate friend Mad_Jock get yourselves on an adult education course and learn how to use the written word in the correct way?......for God's sake.....you people.

[The Greaser]

Please lets stop whinging about grammar and concentrate on the topic.

[eightyknots]

Wouldn't it help if we could all speak the same language though? This country......................unbelievable.

[DFC]

I have no problem joining the final approach track below the platform altitude when being vectored in accordance with the RVA chart.

ATC can only release you to descend with the procedure when you are in a position to continue the approach.

Simple example-

Platform 3000ft

FAF - 9dme/ 3000ft
Stepdown fix - 5dme/ 1500ft
Stepdown fix- 3dme/ 900ft
MAPT - 2dme/ 600ft

ATC vector onto final approach at 8nm and 2000ft then clear you for descent with the procedure.

Answer- descend to 1500ft straight away and be there at or before 5 dme and then continue descent in accordance with the procedure and the ideal constant descent profile.

If a dme/height table is provided, why not delay descent until the appropriate dme - after the one that is above your altitude and at or before the one below your altitude..

There are many approaches round the world where the platform altitude is above the altitude for the FAF.

Regards,

DFC

[ifleeplanes]

Platform and FAF at 2000ft and 6 DME (figures for ease of example). We then expect to start configuring at 8 DME. ATC then put us at 3000ft We are not sure if we are going to get lower, we expect it since thats whats on the plates and thats what we have briefed. We are now approaching 10 DME with a mile before a new decent point of 9 DME for the 'NEW' platform. We rush to configure since we didnt expect this, we miss 9 DME still busy configuring... or should we now start configuring at 11 DME, thinking this is the new platform only to find we are decended to 2000ft. Are both pilots singing from the same hymn sheet? Its a recipe for a rushed approach.

[PPRuNe Radar]

If any of the self appointed spelling police and grammar experts find this, and other threads, too taxing for them ... I can help put you out of your obvious misery by taking any Forums you wish to nominate out of your viewing access, including this one. Just drop me an email and it will be done.

It may or may not be the case in this instance, but PPRuNe is not only used by natural English speakers but by posters from all over the globe. Yet we continually see self appointed 'moderators' jumping on spelling and grammar instead of actually concentrating on debating the topic in hand. All this serves to do is dissuade some people from making posts because they are not confident that their grammar, punctuation, and spelling will meet the ever so high standards which some seem to think are a requirement for being an aviation professional.

This is PPRuNe, an aviation Forum, it is not the Professional English Teachers Forum.

As a Moderator for this particular part of the site, (as well as the rest of it in other capacities), I can state categorically that perfect spelling and grammar is not a pre-requisite for any post made on PPRuNe. We understand that we have many foreign visitors, we understand that we have visitors who are aviation professionals who maybe can't spell but can fly aircraft down to CATIII minimums or set up a flawless radar approach sequence. In short, as long as it is comprehensible to the majority of our readers then we don't mind too much and we certainly won't jump on peoples backs like some posters on this site seem to relish.

The only time I would consider pulling someone up is if they descend in to 'text speak' on ths gr8 site. C u all l8r :\ :}

[eightyknots]

PPRuNe Radar
You use your awesome powers in a most gentle and humanitarian way.
You're absolutely right of course, I had forgotten that English was the second language of Scottish people. Unbelievable......

[PPRuNe Radar]

Smartarse is the same word in either language :)

[DFC]

ifleeplanes,

I can't understand where you have a problem.

If you were making a long staight-in approach to a runway and for the purposes of the example there was no ATC........would you not make a continuous descent and have the aircraft in the required configuration at the correct point without having to level off?

In your example can you not descend at 9nm and configure the aircraft as you descend? or are you going to fast for the distance remaining i.e. this is not simply about configuration but energy management?

Our ideal approach is to close the taps at TOD and not open them again until required to maintain Vref+ in the landing configuration.

When operating into Heathrow and many other airports, the continuous descent low drag low noise descent it the norm.......platform - what platform? ;)

Regards,

DFC

[ifleeplanes]

I'm not saying it can't be done, it can. I have done it many times. Approaches into LHR are generally to an ILS and demand less attention than a NPA. This is backed up by statistics that show incidents on a NPA are 5 times more likely than on a precision approach.

It isn’t often that we perform (personally) long straight in approaches to an airfield. We also are looking to keep a continuous decent if possible. Where do we start to configure now? Do we do it when we are at 14nm and 4000ft only to find we are now dropped to 3000 ft? Do we do it at 11nm at 3000ft etc etc. I’m not saying it’s impossible, just that it can lead to confusion and thus errors. As proved by this very topic.

A NPA demands more attention and is flown less often than a precision approach. We double brief the approach for a NPA at the TOD, this includes the points that we will reconfigure the aircraft, based on the platform on the plates. By putting us at the platform both pilots are totally in the loop since it has been briefed we know exactly where we stand. Should anything else untoward come up we have more spare capacity to deal with it. If it makes little difference for ATC then why not put us at the briefed platform in the first place.

[DFC]

Would you really hang everything out at 11 miles and 3000ft?

Where does it say in your ops manual that the aircraft is to be in the landing configuration - 1000 agl / 4nm ?

Imagine that Heathrow GS is U/S and you are going to make a LOC approach......are you really going to have a problem with not being placed on the platform or with the speed respriction to 4nm...........are you going to dangle the wheels at 9.5nm and 2500 or at 13nm and 3000ft or are you going to do what you usually do?

What if you were put on the LOC 27L at 7nm and 1500ft? - is it really that hard to see from the chart that one descends at or after 5nm to be at 1410 by 4nm?

Just trying to figure out where the problem is.

Regards,

DFC

[ifleeplanes]

DFC that is exactly one of the things Im saying....I wouldnt want everything hanging out at that kind of distance. Equaly I want a stabilized approach especial on a NPA and in possibly poor weather. The problem is where to configure (whilst keeping everyone in the picture) when your not sure of where everything is going to happen and from what height. I dont see the point in making life difficult for myself when there realy is no need.

The airfield I generaly fly into are far less friendly than LHR, having just a decent point and a MAP, maybe one or two check heights on the way down with high terrain all around. If your going to have one way of operating the NPA procedure for one airfield and another for another it makes life complicated and prone to error.

My ops states that I have to be stabilized by the FAF or 5nm whichever is later.

[mad_jock]

:d On the note of spelling and grammar etc.

Yes i am ****e at both, mainly due to being a dslyexic mechanical engineer in a previous life. And unfortunatly the pprune window dosn't hold a spell and grammar checker and i can't be arsed typing it all in in word then pasting it across.

Peoples minds work in different ways. And it is well proven that dslyexics have an above average ability to conceptually develop a 3D model in there heads and be able to work with it. It seems strange to me that some people can't spot mathamatical series and are not able to develop logical problem solving systems. Who then have to go by past experence all the time instead of being able to think and apply there base knowledge laterally to come up with a solution.

We can't be good at everything and I am quite happy being a fag packet engineer / pilot, than an author.

Some of the best engineers I have worked with spend more time writing up than they do designing and doing the engineering. And quite a few of them design and support the planes we fly everyday.

And a note for DFC, ifeeplanes summed it up earlier with the KISS comment. Why bother with the extra work load and additional risk for 30secs saving in the air. The reason why I asked was because I did see a jump in the work load in what was already a high workload phase of flight. And that was going into a airport which I fly into every other day. If flying into a unfamilar airport in ****e wx with a few things snagged on the tech log. It could make the difference between having to bin the approach and causing havock or the worst case a CFIT and having a standard landing.

MJ