ILS Categories. Do I have the right idea?
 

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!

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

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

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"?

englishal,

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

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.

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

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.

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

1. Yes you are correct on the numbers
2. 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.
3. 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)
4. 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)
5. 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.
6. 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

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!

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

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)

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

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.)

Hand Flown CAT3
 

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!

A and C
 

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

http://www.davi.ws/avionics/TheAvion...book_Cap_4.pdf

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!

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) 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) :)

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?).

Wiggy
 

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.

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.

.

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.

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?

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.

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.

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

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

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


Infrared Infra-red glideslope FAF Flir IR IFR Magazine

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

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:

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.

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...

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.

Edited to remove non-obvious silliness.

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.

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.

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.

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.

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.

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)

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.