ILS Categories. Do I have the right idea?

[z.khalid]

So this is what I understand so far.

If the visibility is 550 meters atleast / 1800ft, you are allowed to do a CAT 1 approach, where the minimum DH is at least 200 feet AGL.
Less than 550 M but not less than 350 M (1200) you are in for a cat 11 approach where a DH of atleast 100 feet.

Then come category 111
a: RVR 200 meters / 700 ft, and DH of atleast 100 ft.
b: RVR atleast 50 meters (150 ft), and DH atleast 50 ft.
c: auto land

Not just the numbers, but do I have the idea right?
What exactly is different with the different ILS categories except for the decision height? Speeds, etc. all remain the same?
Do you find the DH if you're doing CAT11, or CAT111 on the approach plate itself?
Is it ever possible that your RVR corresponds to a certain category, but your DH is too low for that ILS category?

Thanks guys!

[mad_jock]

mate if you haven't done the course you don't need to know.

Stick to the cat 1 stuff if you do it to mins its well scary (trust me I have done it enough)

Its really not a subject for private flyers.

Unless you are of course a walt flight sim tosser

[z.khalid]

Done with PPL, going on to IR and self studying for now / also flight simmer :E
Explain?

[englishal]

Its really not a subject for private flyers.
WTF not? I have flown G1000 equipped DA40's and 42's with synthetic vision, better equipment than an airliner. Why can't one fly an approach down to minimums as a "private flyer"?

[z.khalid]

englishal,

Thanks for taking my side.
Except you didn't help answer my question. Just sayin' :sad:

[mad_jock]

because you need approval from your CAA.

You also need the aircraft maitained to a differnet standard.

The crew need to do certain training at intervals. An extra day in the sim is normal evey 6 months.

The crew also needs to stay current at it and also the aircraft needs to do so many per month as well.

Unless you are under an audited QA system you haven't a chance in hell of getting approval.

And as wanky as the G1000 is it doesn't have the fail passive systems for CAT II or never mind the fail safe for CAT III a or b.

[achimha]

What exactly is different with the different ILS categories except for the decision height? Speeds, etc. all remain the same?


CAT III approaches are generally flown at half the stall speed :eek:
Speed depends on the aircraft, its configuration and the weather.

Is it ever possible that your RVR corresponds to a certain category, but your DH is too low for that ILS category?

Imagine a thin layer of fog at 150ft AGL. DH is insufficient for CAT I but RVR will be plenty once you pass through the fog.

Everything > CAT I is reserved for the professional world. Flying at CAT I minima in a SEP can be quite scary. Synthetic vision and radar altimeters are good things to have.

[mm_flynn]

With regard to the original question, I don't see any harm in answering ... So here goes.


Yes you are correct on the numbers
Cat II and Cat III require special authorisation of the crew and aircraft. So your personal minimuqms are defined in that approval rather than some generic approach plate.
Cat III requires lots of sophisticated equipment and training (two crew are definitely required and I suspect two turbines to push all the gear as well)
In the US it is actually possible to get cat II in a single crew single piston engine aircraft (I believe it needs radar altimeter appropriate autopilot, flight director and I suspect two separate ILS receivers and displays)
I don't have the authorisation, but I believe the speeds used are similar and the piloting difference starts with the requirement to fly to US ATPL standards and then moves on to other difference once below 100 feet.
Finally, I have been told there are no civil IIIc approaches due to the lack of effective ground guidance to get from the runway to the terminal with no visibility

[z.khalid]

mm_flynn

Thanks very much for the response.
Another question. I been watching videos of ILS approaches and I can't seem to understand why on the Flight Mode Announcement of the PFD it says sometimes "cat 111 single" and sometimes "cat 111 dual".

What exactly do these means?
Thanks!

[Ultranomad]

In addition to all of the above, for CAT II and CAT III you also have to have an ILS-coupled autopilot.

[wiggy]

FWIW I have a very vague and probably thoroughly incorrect recollection that somebody, possibly Alaskan, have approval for hand flown ILSs to CAT II minima using a HUD. :eek:

For the OP: Whilst the videos can make autoland and Low Vis Ops looks like an exercise in button pushing and then sitting back, relaxing and enjoying the flight there is the (obvious?) possibility of failures of ground and/or aircraft equipment that can be very subtle and if gone unnoticed can very rapidly ruin your entire day. Hence the reason the pros have to retrain and requalify for <CAT1 Ops on a regular ( usually annual) basis)

[SFCC]

achimha.....how is a chap supposed to fly an approach at half the stall speed then?:ugh:

[172driver]

Its really not a subject for private flyers.

I'm pleased to see that we have a real sky god amongst us mere mortals. :yuk:

[Genghis the Engineer]

I'm pleased to see that we have a real sky god amongst us mere mortals. :yuk:

I suspect Mad Jock should have had an earlier night and something was keeping him up in a bad mood! However...

A large proportion of professional pilots, or private pilots, will never fly other than a Cat 1 as well - but it does no harm for them to understand what other people are up to even then.

Although perhaps it might have been a better question in Tech Log, it's being answered here, and reasonably so.

G

(Moderator, asking nicely that we don't turn this into a pi$$ing contest please.)

[A and C]

I to seem to remember at least one airline in the USA hand flying CAT3 aproaches using a HUD. I think it was Air Alaska with the B727.

Or may be it is my old brain playing tricks on me!

[wiggy]

According the link below Cat III it is......which means even more :eek: :eek: from me.

http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_4.pdf

[stickandrudderman]

Its really not a subject for private flyers. Its really not a subject for private flyers.
I suspect that what he meant to say was "Not really a subject for the Private Flying section and perhaps this question might be better answered in the GA/bizjet forum where a higher proportion of contributors are likely to be sufficiently well informed as to be able to respond in an appropriate and professional manner " but couldn't be bothered!

[peterh337]

Come on MJ, having a bad day?

The OP had a valid question.

FWIW, I know of somebody who got Cat 2 approval for a twin turboprop (Commander) and that was single pilot, and single autopilot.

The advantage was minimal; IIRC DH drops from 200ft to 150ft which is frankly barely worth the extra effort, but it does mean that when the airport goes officially "CAT2 / low visibility procedures" in the ATIS (e.g. this trip (http://www.peter2000.co.uk/aviation/dortmund/index.html)) you can legally land there, whereas if you landed anyway (which with an autopilot driving the LOC+GS you obviously could, in CAT2 conditions) you would draw an awful lot of "attention". This private pilot, who had unlimited funding, chucked in his aviation career suddenly after climbing all the way to the top of the food chain because, in his words, he got fed up with running an airline.

BTW, Cat 2 is CAT II but not Cat 11 (CAT eleven). CAT 3 is Cat III but not Cat 111 (CAT one hundred and eleven) :)

[Flamin_Squirrel]

I been watching videos of ILS approaches and I can't seem to understand why on the Flight Mode Announcement of the PFD it says sometimes "cat 111 single" and sometimes "cat 111 dual".

I'm not a professional pilot but I can give you the gist. Generally airliners will have at least two autopilots, sometimes three, each with their own air data, inertial reference data inputs, different ILS recievers, difference power sources etc. The idea being that each autopilot is as independent as possible from the other.

Normally only one autopilot will be engaged, but during an autoland in low vis, all autopilots will be engaged to provide redundancy and error checking (look up fail passive/fail operational for more info).

The single/dual displayed on the PFD is indicating that one/two autopilots are in operation respectively (I'm guessing it was a 737 you were watching?).

[A and C]

Thank you it is reassuring to know that the old brain is still working!

I seem to remember doing CAT2 manual landing in the BAe146 with only one autopilot.

[mad_jock]

Guilty as charged of posting coming back from the pub. I would hope that any of us who still maintain there FI and SEP after moving on from full time instructing don't have a Sky god mentality. The fact is that single pilot IFR operations carry far more work load than we have in multicrew ops. I do apologise. What I meant was that the on going training and engineering and also CAA approval would not be avialble to 99.9% of private pilots. Also as well you need to keep currency going with it for both the aircraft and the crew. Its something like 2 approaches a month.

There are a few aircraft that can do CAT II hand flown.

The advanatages of CAT II and CAT III usually come into play when your searching for a suitable diversion and also the drop in RVR's required before the approach ban kicks in. I think most folk that have just beat the appoach ban at 4 miles with droping viz will have made and approach and landed. But your running the risk of having a cork type accident.

The commmon mistake is to bubble up when you get the runway and loose it again. Or the other one is for folk to dive towards the approach lights, this is usually more of an issue with CAT II lighting which is quite powerful and if your not used to it can give you false impression that your over the threshold when you have another half mile to run until you get to the sea of lights which is the Touch down zone.

Alot of companys have a play with CAT II and then discover that the addition expense for the training and engineering is actually way in excess of the cost of canceling flights on the number of times that CAT II would have made a difference anyway.

.

[englishal]

And as wanky as the G1000 is it doesn't have the fail passive systems for CAT II or never mind the fail safe for CAT III a or b.
I thought that you were referring to "You should not fly an ILS to minimums as a private flyer" ;)

I know that the G1000 is not approved for II, III, IIIc ops, but I reckon in an emergency where you have no other option you could do a zero/zero landing with synthetic vision and walk away.

[achimha]

I know that the G1000 is not approved for II, III, IIIc ops, but I reckon in an emergency where you have no other option you could do a zero/zero landing with synthetic vision and walk away.

Would be interesting to know if people have actually done this. Of course with a second licensed pilot on the right seat. Is it really possible to land e.g. a Cessna 172 until full stop with just G1000 synthetic vision?

[mad_jock]

Gawd no and to be honest if I was in the situation of not much fuel coming down an ILS in a SEP on my IMC and everything was cock on, the last thing I would be doing is going around when we got to decision height. Synthetic vision or not I would keep my head down until I was 50ft QFE then look up. You are far better to crash somewhere with the AFS ready to help than having a forced landing and only seeing the ground in the last second. In all likely hood though though the landing would be uneventful as long as you nailed your cross hairs.

Its quite good training to do to be honest, I have done it under the hood in a SEP and also in the sim on my work machine. You just have to stop yourself looking up because as soon as you do you will loose the ILS. Last 20ft flight idle and pitch for the landing attitude and wait for the bang while keeping the localiser tracking spot on. Not pretty but it works.

And for all intents and purposes when I am flying privately in a SEP on my IMC I am exactly the same as a PPL holder.

Its a load of rubbish to train IMC holders to only the recommended mins. You need to get them from the word go to go down to the proper mins. When it hits the fan properly and they are scrabbling to get in they need have seen and know how senstive the G/S and LOC are. I know that there are PPL/IRs out there as well I only use IMC because thats what I am qualified for in SPA SEP's

And to add I have done it in a C172 with steam instruments under the hood with an instructor in the RHS. There is also a certain scottish examinor who has been known to do the same exercise. It actually isn't that hard, the thought of doing it is by far the hardest crutch to over come.

[englishal]

the last thing I would be doing is going around when we got to decision height. Synthetic vision or not I would keep my head down until I was 50ft QFE then look up
When I did my IR test, the examiner made me fly to 50' before looking up. I called decision height, going around (as he hadn't told me to take the hood off) and he told me to continue. He also said "you fly it right to the deck or you will fail...keep those needles centered god damn it" (in jest I presume). At 50' he let me go visual...so yea it is possible and I agree it would be better to land on the airfield *somewhere* than to run out of fuel somewhere else.

We tried something similar with Synthetic vision, but didn't have the balls to land it, but I think it is very possible, especially as you get a momentum marker which shows your flight path. Keep that on the end of the runway and you WILL make the runway. It is dead accurate.

[172driver]

No worries, mad_jock, been there (the pub), done that (post on Pprune straight afterwards)....

[mad_jock]

I wouldn't try it in something with fragile gear eg PA28 but a sprung steel one was fine with me. To be prefectly honest it was annoying that the landing was actually better than the one I usually did in that aircraft looking out the window.

172driver :ok: ta mate

[172driver]

While on the subject of enhanced / synthetic vision, these two links might be of interest (they are about IR enhanced vision):

Aspen IR approach - YouTube

Infrared Infra-red glideslope FAF Flir IR IFR Magazine (http://www.ifr-magazine.com/ifr_infra_red_flir_faf_glideslope.html)

[421C]

but it does mean that when the airport goes officially "CAT2 / low visibility procedures" in the ATIS (e.g. this trip (http://www.peter2000.co.uk/aviation/dortmund/index.html)) you can legally land there


It might be worth qualifying this. An ATIS advising you the airport is operating CAT II LVP does not mean it's illegal to land there. The LVPs refer to ground movements (eg. using the CAT II holding points). The RVR may be varying around the CAT I minima, and the airport wants to be operating CAT II LVP so that a capable aircraft can use CAT II. But, that doesn't mean a CAT I operation is illegal per se. The controlling factors are the CAT I minima wrt RVR as reported by ATC during the approach and the DA.

Of course, if the ATIS 50nm out is reporting CAT II, it certainly is prudent to divert to an alternate with better wx. But RVR can change a lot in 15mins.

brgds
421C

[abgd]

I'm not certain whether these pilots were using synthetic vision or vanilla GPS/maps, and I'm not sure whether the problem was inaccuracy of the GPS or misuse by the operators (well, fairly certain about the latter). It would make me cautious about trying anything too experimental with GPS though:

Mountain Scrapes Beechcraft Bonanza CFIT Controlled Flight Into Terrain - YouTube

[englishal]

I can't watch the YouTube vid on this computer, but I guess this is the one of the morons who decide to go scud running up a valley in the clagg?

If so, then GPS is probably to blame for saving their lives, and the fact that the GPS dB doesn't have trees in it can hardly be blamed on GPS! GPS terrain dB has a certain resolution and is mapped from space, so although it is in general good enough to avoid dying, when you decide to do something really stupid then all bets are off. Not sure where synthetic vision gets its data from but it is damn accurate with regards to runway positions etc....

I don't think they had synthetic vision as this video's been out for a while.

[abgd]

Yes, that's the one. If the video's to be believed, they could have turned round after entering IMC but chose to press on using the GPS anyway. Could be that the valley was already too narrow to do that comfortably.

I think we're both basically saying the same thing, which is that if you use things in a way for which they weren't intended, you can get bitten. I know there are aims to certify landings with synthetic vision, but I believe the vast majority of synthetic vision systems aren't yet designed for this.

In an emergency, of course...

[peterh337]

Is it really possible to land e.g. a Cessna 172 until full stop with just G1000 synthetic vision?

I don't think the terrain database is anywhere near that accurate. The resolution is of the order of 100-200ft.

Obviously it could be improved locally, around each airport, but somebody would have to be paid to do that, and it would be quite a task. There are of the order of 10k airports in the world.

[abgd]

Edited to remove non-obvious silliness.

[FatFlyer]

The CAT 3 single or CAT 3 dual FMA asked about a few posts ago is an airbus rather than Boeing mode. The cat 3 dual refers to a fail operational situation where should 1 autopilot fail below alert height(100 ft in A320 series) the plane will still auto land safely. This is required for ops with no decision height. With only cat 3 single, it is limited to a cat 3a approach (fail passive)which requires visual reference at 50 feet so if the remaining autopilot fails, the pilot can see this and carry out a go around ( or land with sufficient reference)
It is limited to cat 3 single with some system failures eg engine out.

[englishal]

I don't think the terrain database is anywhere near that accurate.
Maybe not but the airport facilities (i.e. runway etc..) are dead accurate...even so when you roll over the numbers, you roll over them on the screen.

[silverknapper]

WTF not? I have flown G1000 equipped DA40's and 42's with synthetic vision, better equipment than an airliner

This argument troubles me a great deal. Assuming you are talking about an Efis equipped airliner then no, your G1000 Diamond is most definitely not better equipped. It may look nice, but it runs skin deep in terms of redundancy, certification etc. and Synthetic Vision? Bit of a joke really, but sadly I do see the day when someone believes the marketing crap and has an accident whilst trying to land off it. I fly synth vision equipped G1000 a lot and it's an irritation. I always switch it off, IMHO the horizon is more important to an IFR pilot than anything else. The whole 'have to land somewhere' argument is moot. If its that bad why are you there in the first place. But if I did I would be concentrating on the needles, not where Garmin think the threshold is. I also fly EVS equipped machines with the IR camera. Much better than synth vision for this doomsday scenario. But just as illegal and dangerous.

[peterh337]

Maybe not but the airport facilities (i.e. runway etc..) are dead accurate...even so when you roll over the numbers, you roll over them on the screen.

I wonder how that was achieved. Are you talking of SV i.e. a synthetic view produced from a GPS database, or an image intensifier or an IR camera image?

If the former is spot on, that suggests that somebody put the runways in exactly right. But what about the surrounding terrain? My guess is that somebody spent time on "adjusting" the terrain around specific airports, so the runway actually lines up with the ground next to it :)

This won't have been done worldwide.

But just as illegal and dangerous.

Only if you have the other options :)

Obviously one should not be there in the first place. But SV would be good for the case of e.g. an engine failure above an overcast. I know there are people who would argue one should never fly SE above an overcast unless the cloudbase down below is 1000 / 10000 / 100000 feet or whatever, but that stops much SE flying and is a whole other argument.

[mm_flynn]

I believe the runway/terrain depiction is based on
1- the very very accurately located thresholds (both with respect to Lat Lon and elevation)
2 - a 'normalising' of the terrain data to make sure the terrain elevation matches the threshold points (from 1 above)
3 - a contouring of the runway to match the normalised terrain connecting the two threshold points
4 - colouring the runway to match the published markings

I have never used SV, but despite the cautions from the posters who are commercial operators, I would have thought the ILS crossbars and a momentum vector laid onto a SV view of the runway (less so the surrounding terrain) would provide a very compelling and accurate flight path to precisely the desired DH and localised centreline.

HOWEVER, I would be concerned it is so compelling that people figure, 'I can go another 20 feet, 100 feet, I can actually land Blind!'. Moreover, I don't think there is any objective training of why this is unsafe (vs. a simple statement that it is not legal)

[mad_jock]

Do they use the same model that the EGPWS database uses?

If so there is no way I would trust it to be anything other than a cloud breaker in an emergency.

the touchdown point is generated by survey on the plates as is the other end so it is reasonably easy to set up the runway in a database. Your altitude would be a be suspect on it though. The rest of the surrounding terrian will be inputed in chucks, What fractal resolution they will have used for that I don't know but I would spuspect that it niot very fine because the amount of data goes through the roof very quickly as you reduce/increase (can never remember which way round it is) the fractal length.

The coming down an ILS is a completely different kettle of fish being calibrated and not subject to data errors never mind all the other features of using GPS which quite a few discount to quickly in my opinion.

[englishal]

Synthetic vision actually gives you a tunnel when the approach is activated. You intercept the tunnel (if vectors), stick the momentum marker in the middle of the tunnel, and you will land on the runway. traffic appears on the Synthetic vision too along with any other pertinent info.

It is pretty funky when this if from a GPS LPV approach, and makes you realise what really is possible these days (unfortunately not in Europe for another 20 years).

I'm all for anything to aid situational awareness. My buddy flew into a mountain on an IAP in a Seneca, obviously lost SA and killed 5 people. GUARANTEED if he'd been flying one of these aeroplanes, this would definitely not have happened.

The problem is when that person goes beyond the limit and pushes their luck.....

[mad_jock]

But there is no calibration of the information.

You have no way of knowing if its correct or not.

[mm_flynn]

But there is no calibration of the information.

You have no way of knowing if its correct or not.???
which information?

the 'tunnel' is either going to be generated from an LPV Or VNAV representation from the GPS, or I believe from the ILS data. Either way this is going to be 'right' to well below Cat I DH.

I accept there may be a risk that for some airport the runway placement may be in error (certainly with regard to trying a blind landing). And is, as far as I can see, the main risk with SV.

[mad_jock]

If your using it as signal generator to display an alternative to cross hairs or "wings" for true ILS data fair enough the terrain data cant be trusted unless someone calibrates the ILS using the same info.

If your using it in GPS mode to generate a persudo VORTAC approach then flying it down the boxes with no error flagging or secondary cross check of GPS error you need your head examining.


Although quite whats so hard about getting two needles to form a cross I really don't know.

[riverrock83]

My understanding is that with current technology (WAAS - so only in the USA), GPS can't be relied upon to be more accurate than +- 7.6 meters at least 95% of the time (that is from the WAAS specification) horizontally and vertically. If you have a large commercial runway 45m wide (which is likely the case if there is an ILS available anyway) then you are still going to hit it. However without some way of determining height (ie a radar altimeter) then landing with your head down simply isn't safe (your guess when to flare is as good as mine!).
I believe WAAS allows GPS to be used for Cat I approaches in the US - but most of us on this forum aren't in the US.

Without the additional checking that WAAS provides you need to have some other way of verifying that your GPS is accurate.
Maybe once EGNOS (http://en.wikipedia.org/wiki/European_Geostationary_Navigation_Overlay_Service)is available it will be different. Until then GPS can only be a secondary navigational source in Europe.
(http://en.wikipedia.org/wiki/European_Geostationary_Navigation_Overlay_Service)

[peterh337]

Until then GPS can only be a secondary navigational source in Europe.

Oh dear here we go again.

:ugh::ugh::ugh:

One thing which is so much better about pprune than Flyer is that the most useful icons are much better placed :)
(http://en.wikipedia.org/wiki/European_Geostationary_Navigation_Overlay_Service)

[mad_jock]

Peter it doesn't change the fact its correct.

And in my experence when your flying in the crap is when the bloody signal drops out.

[maxred]

I honestly looked at the clock and thought, wonder if Peter has read this yet. :)

[mad_jock]

I know and either he has the best GPS installation in europe (which it well might be)

Or he doesn't fly in the crap that I do which is when normally it does give up the ghost.

And thats not even discounting the multiple bawbags around europe with illegal hand jammers and the fact that mutliple completely official agency's can jam with no warning whats so ever

[maxred]

Two weeks ago, 7500 feet over Carlisle, and lost GPS signal, for at least 20 minutes. The best of it was that Carlisle International had asked me to squak, and when I lost the signal, I asked Carlisle to give me a position check re Danger Areas, his reply being we are non radar:confused:

Just as well I knew where I was then, tracking my trusted RNAV:ok:

[englishal]

Although quite whats so hard about getting two needles to form a cross I really don't know.
You get the tunnel IN ADDITION to the regular needles of course.

[mad_jock]

So what do you need a tunnel for then? You either in limits or your not and going around.

All this extra stuff does is just over load the pilot with information and distract them away from the primary instruments.

[stickandrudderman]

People often advocate entering a long runway at half length in order to expedite departure. My own view is that it's foolish to throw away the opportunity to land back on in the event of an engine failure after takeoff, so I always start as far back on the runway as I can as it gives me an extra safety margin.
I like having SV and GPS in my aeroplane because it gives me an extra safety margin, not because I'm a lazy pilot who can't be bothered with situational awareness.

[Denti]

Synthetic vision is a very nice tool. However it can only display database info, not the car on the runway, nor the aircraft that switched off its transponder once it landed. And the database cycle is of course a major issue. Just judging from nearly every european airport there are always several NOTAMS out about new obstacles, work in progress with cranes and so on. Even at a normal update cycle length of 28 days (EGPWS databases do not update that often) there are always numerous obstacles that are not part of the database.

Now, enhanced vision is quite another thing. Costs of course quite a bit more, but then, it can do more too, even in europe you get lower limits with that.

[mad_jock]

enhanced vision is quite another thing

O yes that is an extremely nice bit of kit.

[NazgulAir]

People often advocate entering a long runway at half length in order to expedite departure. My own view is that it's foolish to throw away the opportunity to land back on in the event of an engine failure after takeoff, so I always start as far back on the runway as I can as it gives me an extra safety margin.


Reminds me of my instructor telling me about the three most useless things in aviation:
- the runway behind you
- the air above you
- the fuel in the bowser.

[peterh337]

in my experence when your flying in the crap is when the bloody signal drops out.

Perhaps you should post some pics of your avionics, MJ.

Hang on.... I think I have found it!!!!

http://www.avsim.com/pages/0808/Justflight/5-1%20XJ824%20Instrument%20Panel.jpg

Google is just wonderful.

[mad_jock]

I can't see the BRNAV gps in that pic peter. I don't think it would cause me any problems though. I fact I would love to fly it if its what I think it is.

http://flightsim.com/howto/getreal3/BAEjetstream41panel.jpg

Nope this is the avionics I had most drop outs with. But it didn't really matter because its primary mode is DME/DME cross cuts

[peterh337]

Nice as that looks, it is probably a pre-GPS-era cockpit.

[Piltdown Man]

Not just the numbers, but do I have the idea right?
Basically, yes.

What exactly is different with the different ILS categories except for the decision height? Speeds, etc. all remain the same?
The training, equipment, sometimes wind (due A/P limitations), DH, airport equipment and status, runways slope, RVR just to name a few.

Do you find the DH if you're doing CATII, or CATIII on the approach plate itself?
For CAT II, these are published on the plates we use but CAT III minima are operator specific. These are supplied by your company and come as a result of specific Low Visibility Operations training.

Is it ever possible that your RVR corresponds to a certain category, but your DH is too low for that ILS category?
I think you have this arse about face. Assuming you have a "standard" CAT III runway and an appropriately equipped and trained crew, the RVR defines the lowest DH that can be used and by virtue of that, the type of approaches that can be flown. So if the RVR is greater than 550m, a crew could fly a CAT I, II, IIIA or IIIB approach. Drop the RVR by 100m to 500m and a CAT I approach is (generally) no longer possible. Drop the RVR to less than 300m and a CAT III approach has to be flown.

Does that make sense?

PM

[mad_jock]

Certified in 1992 and was the first JAR25 and FAR25 certified turboprop which I think there is a BRNAV requirement with.

Its also certified for CAT II.

[peterh337]

Certified in 1992 means designed several years before that, which is just about pre-GPS.

With INS with DME/DME corrections, GPS was never a priority. Only the most modern airliners have GPS integrated into the INS, and AFAIK they have three of them.

You are living in another age :)

There are numerous ways to end up with crap GPS reception. VHF interference (11th and 13th sub-harmonic of 1575MHz) is a common one (try transmitting for 20-30 secs on 121.2 and see what happens to the GPS satellite signal levels). ELT pi-tank resonance (triggered by VHF transmission anywhere around 121.xx to 122.xx) is another. Crap installations are another :)

So if the RVR is greater than 550m, a crew could fly a CAT I, II, IIIA or IIIB approachI think there is a "story" behind this, too. In UK airspace, a single pilot is limited to 800m for takeoff and landing. With high intensity runway lighting and with an autopilot which can fly the ILS all the way down to the published minima (say 200ft DH) this improves to 550m which is the normal published vis figure on Jepp plates.

That's AIUI, anyway.

Incidentally, I am told the standard answer on an IR test is supposed to be 800m and if you answer with 550m then you fail, because you are not supposed to use the AP.

[mad_jock]

Nope was 90's when it was designed and they all came fitted with GPS of some form even if it was a trimble.

The age I am living in is the age which 95% of the world fleet of aircraft are in.

How many aircraft types have been certifed since 1992? Not many.

Maybe a Q400 driver can tell us what thier box of tricks uses I suspect its DME/DME though.

I know you will never be swayed with your reliance on GPS and the rest of us are dinasours. For me it is a very useful tool in the box which gets treated like any other bit of information in the cockpit. ie it gets cross referenced against something else.

Personally I am quite glad that there are cooler heads out there putting the brakes on ditching all the rest of the gear and putting all our eggs in the one box.

Personally I do think we will get them but it won't be with the current kit.

[Midland Transport]

Just to add 1 more complication. For single pilot operations in the UK the RVR minima is 800m however if you have a coupled AP then the RVR brecomes 550 (or the stated RVR) as was previously stated. However, for the DH if your A/P is approved to 200 ft you should then apply 1.25 times that ie 250 DH. So the resulting combination would be DH 250ft RVR 550M if you used a coupled A/P. A further complication is that some autopilots do not have a state minimum operating height.

[peterh337]

gets cross referenced against something else. I never said it doesn't.

The anti GPS crowd always takes the same tack:

using GPS = sole reliance on GPS

which is bollocks.

For single pilot operations in the UK the RVR minima is 800m however if you have a coupled AP then the RVR brecomes 550 (or the stated RVR) as was previously stated. However, for the DH if your A/P is approved to 200 ft you should then apply 1.25 times that ie 250 DH. So the resulting combination would be DH 250ft RVR 550M if you used a coupled A/P. A further complication is that some autopilots do not have a state minimum operating height. Interesting; thanks :ok:

On the UK CAA IRT one is supposed to add 50ft anyway to the altimeter reading for the DH (I am told) so 200ft is never actually achievable.

Is any of this changing under EASA OPS?

[S-Works]

Blimey all these luxuries. I am lucky to have hot air bleed to warm my feet....

Although we are GPS BRNAV!!

http://i303.photobucket.com/albums/nn151/skyhawkxp/do28/5a3f27fb.jpg

[mad_jock]

I am not anti GPS.

And for certain situations ie above MSA the risk is low enough that its acceptable.

But below that there are so many external factors which effect the quality of of the position that the risk is unacceptable currently especially as there are no warnings when it does go out.

I suppose you could have a tone on a fequency which triggered when the local GPS strayed away outside tolerance from a fixed reference. Which would then flag in the cockpit.

:ok: bose the art of landing an aircraft when you can't feel anything from your knee down.

[mm_flynn]

I am not anti GPS.

And for certain situations ie above MSA the risk is low enough that its acceptable.

But below that there are so many external factors which effect the quality of of the position that the risk is unacceptable currently especially as there are no warnings when it does go out.

I suppose you could have a tone on a fequency which triggered when the local GPS strayed away outside tolerance from a fixed reference. Which would then flag in the cockpit.

:ok: bose the art of landing an aircraft when you can't feel anything from your knee down.

Assuming your GPS is approach approved you probably should get the owner/operator to have it checked out.

You should have RAIM integrity warnings that does give you your desired flag if the GPS position becomes unreliable. Also, it should be exceptionally rare for an approved installation to loose signal coverage - there must be something wrong with your installation or you are operating in known jamming areas.

Finally, GPS in and of itself is approved (even for Europe) at its basic level as the sole means of navigation to well below MSA. If you have WAAS then it is approved for approaches to ILS like minimums. (obviously it is always good to use the maximum amount of information to crosscheck any piece of magic - new or traditional)

In the US it is even approved for RNP approaches that no other navigation system provides the necessary accuracy and integrity to execute.

[peterh337]

especially as there are no warnings when it does go out.

Say again?

:ugh:

What century are you in, MJ?

[mad_jock]

Yes the known jamming area is called the United Kingdom which they are allowed to jam at any time without NOTAM. There are airborne jammers as well for the war games. Around any of the Mil ranges though out the UK they can and do Jam. Recently they had it brought up in Parliment to get them to stop jamming during a war game because all the fishing boats were getting lost and with the current restrictions it meant that they were looking at not finding there fishing spots on the few days a month they could actually fish.

This isn't just one aircraft its happened in getting on for 36 airframes in my log book. And they are all public transport CofA's.

They will be approached approved but as there are very few GPS approaches in europe I haven't done one in anger. I did submit a form or two for the test ones in the UK but unfortuantely it didn't aid the cause because RAIM dropped and we converted to a visual without getting to the FAF but that could have been the FRA Hawker that was operating in the area for an exercise.

The only warning that comes up on the units is a very small flashing msg light and when you go press it twice it comes up RAIM fail, check your position or something like that. Most folk ignore it because it goes on and off at various points and usually goes away after a few mins.

But I have every expectation that all my experences will be put down to crap aircraft, crap equipment, crap pilots(even though we don't need a GPS to get where we are going). That its no fault of the GPS system and I should get out of the dark ages and put my faith in it when scraping my arse to the deck in 600m and OVC 001.

Peter we have no warnings whats so ever on the primary instruments when it fails.

[englishal]

But below that there are so many external factors which effect the quality of of the position that the risk is unacceptable currently especially as there are no warnings when it does go out.
I think you'll find that GPS is probably the best nav system with regards to warning the pilot when there is no GPS signal!...you get flags, messages, etc...Is yours a certified installation or is it a hand held mounted on the windscreen?

Actually the GPS jamming trials didn't even affect my 430W or Aera, even though I flew slap bang through the area. Mind you I have it properly mounted and IFR certified.

[achimha]

I think you'll find that GPS is probably the best nav system with regards to warning the pilot when there is no GPS signal!...you get flags, messages, etc...Is yours a certified installation or is it a hand held mounted on the windscreen?

I've had spurious issues with a GNS430W ranging from signal degradation to complete loss of signal for some time without a clear pattern. It was eventually traced down to a defective unit. Note that in my IFR certified installation, the loss of signal did not make the CDI show an off flag!

The user interface of the GNS430W is absolutely terrible and its habit to constantly pop up stupid and irrelevant messages that you only see when you press a button trains pilots to not assign any importance to them.

I got my license when GPS was already ubiquitous and always considered the whole VOR/DME stuff to be rather annoying but after my experience with the GNS430W, I see myself tuning VOR/DME stations enroute and perform cross check.

[peterh337]

I see myself tuning VOR/DME stations enroute and perform cross check.

That is only sensible.

Re the CDI flag, that's interesting, and probably intended behaviour. I originally had a KI-525 HSI whose NAV source could be switched (as is traditional) between GPS (from the GPS) or NAV (VOR/LOC according to the frequency selected on the radio). The Invalid flag was never driven by the GPS, AFAIR. Now I have an EHSI (Sandel 3500) and that makes it very obvious if the GPS is not picking up a signal.

Re GPS failures, I've had them too. One off Italy in 2004, halfway between Brindisi and Dubrovnik, at about 1000ft. Lasted a few minutes, and affected all three units. That one was porb99 jamming. One departing from Padova (Italy) in 2006 which lasted from startup for about 30-45 mins, which affected only the one GPS (KLN94) and that one was probably a corrupted constellation table in the GPS, which always takes a while to clean up. I then had a strange Garmin 496 failure in 2010 when a specific DME frequency was selected, without any other GPS being affected, which is not explained by any subharmonic of 1575MHz.

Out of a total flying time of about 1400hrs that is under 0.1% i.e. a 99.9% + availability. And if you predicate GPS approaches on obvious GPS availability, let alone RAIM, you are looking at a 100% reliability. I've never had a GPS malfunction which wasn't totally obvious on the GPS.

In flight, the possible lack of a CDI flag should not bother the pilot because few would (or should) be flying with GPS using a CDI. That is probably how the "old school" started using GPS, and indeed the original non moving map units (Trimble etc) did only that i.e. generating a cross track error which would be viewed on a CDI. Today, nobody should be flying with a GPS in that way. There is only one thing worse and that is plotting the GPS coordinates on a map :) One should be monitoring the GPS moving map as the very primary source of navigation data. That map is the "big picture". And if you lose signal, that is where any error messages will appear.

Admittedly a Garmin 430 has a map too small to be of much use, which is why I don't have a Garmin 430 :) And if I did, I would have it feeding a nice size MFD. I don't consider a single GNS430 sized unit as adequate for IFR.

[BackPacker]

How do you fly a GPS approach then? I have no IR but I would assume that you would use the CDI/GS (slaved to the GPS) as primary guidance.

If a GPS failure would not throw a flag right there in your face, you might miss it altogether.

[silverknapper]

Peter

It was a while ago but for my IRT we added 50' to the MDA but not to the DA. A practice which is common now in the name of stabilised approaches, non precision. It becomes a 'virtual' DA where one can initiate a GA at this new DA and with any inertia still not bust the MDA.

[peterh337]

How do you fly a GPS approach then? I have no IR but I would assume that you would use the CDI/GS (slaved to the GPS) as primary guidance.

That is true...

I would guess that if you are driving a dumb CDI from a GPS, the CDI flag has to be connected appropriately.

That is an issue in the avionics business; some installers just throw in a GNS430, connecting up the basic wires and that's it.

Normally, of course, you use the autopilot and monitor the approach on the moving map, on which the entire approach is depicted :)

One would not just watch the CDI and not the GPS because, for example, one needs to be sure the GPS is correctly sequencing to/through the approach, with the sensitivity dropping from 5.0nm enroute to 1.0nm by the IAF, to 0.3nm at/past the FAF. This stuff is only on the GPS screen.

It was a while ago but for my IRT we added 50' to the MDA but not to the DA. A practice which is common now in the name of stabilised approaches, non precision. It becomes a 'virtual' DA where one can initiate a GA at this new DA and with any inertia still not bust the MDA.

Interesting... I was told differently: add 50ft to the published ILS DA, but add nothing to the published NP MDA. With the ILS you go missed at the newly calculated DA and climb straight up. With the NPA you fly level from the point where MDA is reached (at an altitude which is between the published MDA and that plus 50ft) all the way to the MAP and then climb. If you bust either figure you fail, and if on the NPA you climb outside that 50ft band (before the MAP) you also fail. I will need to revisit this when I get the plane out of the Annual...

[silverknapper]

At the risk of teaching granny to suck eggs:

There are two ways taught to deal with an MDA.

1. Fly level at MDA until the MAP. You are correct, the examining limit for this method is -0/+50'.
2. My previously mentioned add50' to MDA and treat as a DA. Though this 50' would increase with aircraft weight. Basically you need a margin which would allow you to initiate the GA and not bust your MDA. So you fly a stabilised descent to the Virtual DA then go around. This may be before the MAP, depending on how well you have judged your descent path.

The second method inevitably could lead to you missing out on the last 50' of cloud base, but is much safer than levelling off fully configured. Indeed for commercial operators EU ops made it mandatory.

Of course the basics still apply. MDA is absolutely not to be busted. DA is where the GA must be initiated so in a large enough aircraft this could be busted whilst engines spooled etc. this is ok.

[Denti]

How do you fly a GPS approach then? My aircraft is certified to fly them with both GPS INOP. As long as the RNP is higher or equal to 0.3.

However, GPS approaches are a thing of the past, nowadays it is RNAV or RNP approaches. Same here, down to RNP 0.3 i do not need GPS, helps to have it though of course.

[peterh337]

Is that a joke?

[mm_flynn]

Denti is just having a US pedent wheez. All that is required for a US 'GPS' approach is an approved RNP 0.3 navigation system. It doesn't actually have to be GPS. But for the private flyer I don't believe there is any other option (and I am not sure about any options other than GPS no matter what civil aircraft one flys).

[peterh337]

OK; I dare say you could fly a published "RNAV" approach using any RNAV RNP0.3 nav system, which could (at a stretch) be an FMS driven off an INS which uses DME/DME corrections....

That's because the published plates are entitled "RNAV/GNSS" or similar. One doesn't actually have to fly them with a GPS :)

[Denti]

Actually, im EU based and fly according to EU-OPS. Still legal to do without GPS.

But yes, for the private flyer (outside of those rich enough to afford their own jet) GPS is the only available means currently to fly those approaches.

[madlandrover]

On the UK CAA IRT one is supposed to add 50ft anyway to the altimeter reading for the DH (I am told) so 200ft is never actually achievable.

Not quite - see para 6.1 of AD1-1 in the UK AIP. In short, details of PEC for your aircraft should be in the AFM/POH. In the absence of such data then 50' has been found to be suitable for a wide range of light aircraft. A good example of when not to add 50' is the humble Grumman AA5, where the POH specifies a PEC of 15'. Don't be put off from fighting your corner when you're right ;)

[peterh337]

That's useful - I didn't know that.

My POH shows no PEC (that I can find). I thought the POH does not have to show a PEC if it is below 50ft.

So for the IRT you are supposed to add 50ft (if the POH shows nothing), or the POH PEC (if the POH contains one).

I think adding 50ft is a whole lot simpler than fighting a corner, regardless of whether I am right :)

[madlandrover]

Correct, if no PEC shown then add 50'. If a PEC is shown then use that. Some of the EFIS aircraft I fly are certified as precision altimeters so we add nothing - makes asymmetric go-arounds from a DH of 200' with screens up a good test of flying accuracy. And as it should be done of course. Sadly I'm not very good at giving in when I know I'm right :E