100 foot ILS minima

[Brian Abraham]

Pruners,
I understand that Cougar, and perhaps other operators, had,or have, approval to use a 100 foot minima on an ILS. Does anybody have details, particularly what special requirements there may have been. Also heard a rumor that approval has since been with drawn. If so for what reason?

Many Thanks, Brian

[Shawn Coyle]

Brian:
Cougar had approval for Category II approaches in the Super Puma Mk II, same as anyone else who had the equipment and the training. At least they did several years ago.
The only place with Cat II ILS for them was at St. John's Newfoundland - a place that really needed it.
Not sure of current status, but will make discreet enquiries.

[John Eacott]

Brian,

Okanagan had approval, via its Ops Manual and Transport Canada, to halve ILS minima for certain approaches. This was raised with CASA at one of the gabfests in Canberra, with positive response from the then Chairman of CASA, and deep promises to put it on the agenda.

12 years later........the silence is deafening :rolleyes:

[Bomber ARIS]

Cat II operations worked very well for MAERSK Helicopters in Denmark............until "some other company" entered the equation, flogging off their Dauphin and dispensing with Cat II training and the associated equipment required to take the Pumas to 100'.

"Cat II capability generates revenue for offshore operators" - Discuss

(The Aberdeen bean counters in question obviously saw no extra revenue in the capability)

[joedirt]

I think the hummingbird guys still have those minimums for their 61's in relation to their lack of alternates :eek:

[Reflex]

As I understand it, Cougar go to Flightsafety at West Palm Beach and due the necessary training for the 100 foot DH.

Flightsafety are running a lecture once a week about the FAA rules and regs concerning "copter ILS" down to 100 foot DH which is open to any of their clients attending training. At least someone is prepared to recognise that all this fancy kit in modern helicopters actually does something - not just makes it look like a fancy poster!

[GLSNightPilot]

In the US, 100' is the defacto minimum altitude, because you can descend to 100' above the TDZE if you have the approach lights in sight, and you can almost always see them from 200' directly above, especially in the dark. I did this the other night on a medevac flight, with home reporting 1/4 mile vis and 100' VV. We got the approach lights in sight at 200', the runway end lights at 100', and landed legally. No special training or authorization is needed for this. Other national regulations may be different.

[212man]

GLSN, I'm curious: 1/4 of a mile is 463m (or 400m if statute) which is below the Cat 1 minimum. What happened to approach bans?

Where does the 100 ft above TDZE bit come in; if you can see the lights you can continue to land, surely? What happens at 100 ft?

I would disagree slightly about being able to see the lights at 200 ft; if the cloud base is solid below 200ft then you simply see nothing. It's quite a sobering thought to be that close to the fround and not be able to see it.

[Bomber ARIS]

US visibilities are give in STATUTE miles

[Mr Toad]

As I recall approved BAH crews at Aberdeen in the 80's could fly to the Cat 2 lower minima provided the aircraft was fully coupled and both pilots were in date and so endorsed on their licenses and the ILS in question was approved for this. This 20 years ago...

I believe the landing minima were 100'/400m RVR and the take off minima were 50' cloudbase and 100m RVR with a useable single engine diversion within 45 mins.

These minima applied to the Chinook where Cat 2 approaches could be practised on the sim (on site in those days). I'm not sure what the other companies were allowed; it was commonplace to us then, so it must surely still be so all over the foggy North Sea with today's much more capable aircraft.

I'm sure somebody will correct me if I'm wrong, but there was nothing difficult about it provided that PF and PNF understood their functions clearly - especially at the bottom! This is where modern CRM and Human Factors have so improved our understanding of two crew operations, especially when regularly practised in a sim.

[212man]

It does require a certain amount of additional investment by the operator (and manufacturer) to operate to Cat 2. Details can be faound in JAR OPS-3 section E and JAR AWO. I asume the FARs will replicate this too but haven't searched.

I would say that in the latest generation of a/c it would be no big deal at all, in fact Cat 3a would not be that big a deal either. I guess it is a question of statistical evidence that X amount of revenue is being lost by N number of missed approaches or Y extra pounds of fuel being carried because of alternate weather criteria. If X is less than the cost in para 1 then why bother?

[GLSNightPilot]

1/4 mile is 402.336 meters, to be precise. What are 'approach bans'? In the US, helicopters may reduce the published visibility on standard instrument approaches by half, but not less than 1/4 mile or RVR 1200 (~366 meters), provided the final approach speed is 90 kts or less. ATC will never refuse an approach request, because it's up to each operator to know what the limits are for his operation, which are in the operations specifications from the FAA. And for non-commercial, Part 91 operations, the pilot is permitted to fly the approach regardless of the reported weather, and land if the in-flight visibility is found to be at or above the legal minimums.

You only need 200 feet visibility to see the approach lights at DA, because you're looking straight down at them, or very nearly so. And you can only descend to 100' above the touchdown zone elevation with just the approach lights in sight. In order to land, you must be able to see the runway environment, which includes a laundry list of specific items.

For those with sufficient interest and ambition, the pertinent part of FAR 91 is here (http://tinyurl.com/59ach) .

[212man]

Well, I made it 402.43 but let's not split hairs!

I couldn't open your link but managed to find your comments about minima in Part 97; very interesting. What I found more puzzling was that in Part 91 it prescribes the take off minima as not less than half a mile, for helicopters, which is quite restrictive if you are operating IFR.

I couldn't see any reference to approach bans, but did not have unlimited trawling time. Basically, when operating to ICAO Annex 6 or related rules, you cannot contine an approach below 1000 ft above the touch down elevation if the reported RVR is less than the published minimum. If you have passed that point and it falls, then you may continue (there are expanded bits to that definition, but not really relevant here).

I'm still curious about the additiona reference to 100 ft above TDZE bit, it seems to imply that you can decide to continue below the DA/DH if you can see the approach lights, but can't land from 100 ft if you can't see the required visual references on the airfield. What then? Missed approach? So you go from on instruments, to looking up at DH and 'going visual' (in real clag) commencing a deceleration, then at 100 ft you have to carry out a missed approach; back to instruments, re-adjust the aircraft attitude/power etc. Seems strange. At DH you can either see enough to land, or you can't, is the normal criteria.

Obviously there's always the odd chance you may inadvertently go IMC again below DH and carry out a missed approach (or the runway lights fail, as in the Gerona 757 crash) but normally it's pretty clear cut.

[GLSNightPilot]

The 1/2 mile for helicopter takeoffs only applies to airfields which have no takeoff minima established, or from other locations. Operations specifications often allow takeoff with lower visibility. For instance, we can take off with visibility equal to the landing minimums for any approach to the airport, or with a properly trained and experienced crew, with 'adequate visual reference'. This means, in effect, that I can depart any airport with 1/4 mile visibility in the daytime, and from any lighted runway at night with the same. Heliports, onshore and offshore, require 1/2 mile, and 300' and 1 mile at night.

As for the approach, yes, if you descend to 100' and don't have anything in the runway environment in sight, which includes any of the list of items listed, then it's a missed approach. I have never had that happen, and I've flown many approaches with 1/4 mile visibility reported. At 100', on the GS, you're much less than 1/4 mile from the runway. Note that to fly the approach, only the visibility is required; the ceiling is immaterial at that point. And after the FAF, the approach can be continued even if a new report indicates the visibility to be below minimums, but you still have to have the required visibility to land. This applies to everyone, not just helicopters.

I'm not sure why you can't open the link, because it works for me, but if you start at http://ecfr.gpoaccess.gov/ and then follow the links through Title 14 to Part 91, you'll find it at 91.175, Takeoff and Landing Under IFR. The language is typically convoluted and bureaucratic, but if you assume that anything not specifically prohibited is allowed, and read it a few times, you'll see what I referrred to.

All this is FAA only, and I make no claims whatsoever for any other country.

[IHL]

In Canada Category 1 ILS approaches can be flown by rotorcraft to a 100 DH providing the carrier complies with the following conditions:



(19) Lower than Standard Decision Height
Category 1 Instrument Landing System Approach Minima - Reported Visibility RVR 1200' - Decision Height 100'
Authority to conduct approaches to 100' DH with 1200 RVR is subject to approval of a training program using an approved synthetic training device for the helicopter type to be used. The training device shall be capable of depicting IMC to 100' DH.
The training program shall include:
(a) capabilities and limitations of the ILS and visual aids;
(b) operational characteristics and limitations of the airborne system to be used such as the flight director, automatic approach coupler and systems and devices peculiar to the applicants installation such as missed approach guidance and failure warning systems;
(c) individual crew duties including approach briefing, two pilot challenge and response communication rule, pilot incapacitation procedures and pilot monitored approach procedure with emphasis on need to continually monitor flight instruments until attitude and descent path have been visually assessed; and
(d) training in the synthetic training device shall include effects of wind shear and turbulence, recognition and reaction to malfunctions encountered prior to and after reaching the missed approach point, ILS approaches to landings from 100'/1200 RVR conditions and missed approaches during which practical malfunctions and emergencies are introduced.

(18) Lower than Standard Take-off - Weather Minima RVR 600 feet
Authority to conduct 600 RVR take-offs shall be subject to approval of a training program using an approved synthetic training device for the type of helicopter to be used and capable of depicting RVR 600' take-off conditions. Training is required for the pilot-in-command only unless the air operator authorizes the second-in-command to conduct 600 RVR take-offs in which case the second-in-command shall complete the same training.
The training program shall include:
(a) take-off alternate requirements;
(b) one engine inoperative performance requirements;
(c) responsibility for obstacle clearance and visibility requirements;
(d) take-off runway requirements;
(e) helicopter equipment requirements;
(f) pilot qualification requirements; and
(g) training in the synthetic training device shall include normal take-offs under RVR 600' conditions and rejected take-offs under RVR 600' conditions including engine failures and system malfunctions.
http://www.tc.gc.ca/CivilAviation/Regserv/Affairs/cars/Part7/Standards/724h.htm#724h_115 (http://)

[rotorspeed]

Very interesting thread, particularly comments from GLS and 212 on when approach lights can be seen from above in very low vis situations.

GLS - if vis is say 100m (330ft) and cloud OVC000, is your experience (if you have any of such conditions!) that the approach lights can be seen from directly above at say 100ft? On the face of it, presumably if the horizontal vis is 330 ft and the cloud is on the deck, the vertical vis should be the same, ie 330ft, yet practice seems to indicate this is definitely not the case, though this may be because we tend to be looking at slant visibility at the bottom of the ILS. Does cloud density tend to increase above the ground in cloud fog? Assuming it is genuine OVC000 and there is no element of vis beneath the cloud, don't see why it necessarily should.

How about ability to see approach lights through cloud/fog in night compared with day - what experience does anyone have of this?

[GLSNightPilot]

Rotorspeed, as for your first question, I'm sorry but I can't answer it. We can't begin an approach with less than 1/4 mile visibility, so that's the lowest I've landed with. With 1/4 mile vis, the approach lights usually become visible at or just over 200', and the REILs and PAPI become visible at or just over 100' - at least that has been my experience.

IME the lights are easier to see at night, without refracted sunlight masking them. If I have to fly an ILS down to minimums, I prefer to do it at night, because I think I have a better chance of landing. Also IME, if you can't keep both needles centered, then keep the localizer centered if you can. If you're a little high on the GS you'll still be able to find the runway if you're over it.

[rotorspeed]

GLS

Thanks. With that 1/4 mile vis example what sort of reported cloud base are you talking about - pretty much on the deck?

[212man]

One area that is easily overlooked when considering low instrument minums is the effect on the Cat A/PC1 performance. If you are making an approach to Cat 2 minimum then it is likely that you will need to reduce the speed considerably by the time you arrive at DA/DH; after all, most Cat A LDPs are at 100 ft or there abouts. However, a balked landing from a Cat approach allows for a descent down to 35 ft agl whilst accelerating to Vtoss, which is more than the ILS procedure would allow for.

On the other hand, keeping the speed up (even down at Vy which could easily be 80 kts) presents all sorts of problems when transitioning from the approach to the landing. This is one problem the fixed wing world do not have.

PS. Thanks GLS for your well written and informative accounts of IFR operations in America.

[GLSNightPilot]

Usually when the visibility is down to 1/4 mile, the vertical visibility is reported as 100'. I'm not certain about the technical details of how this is derived. I don't recall seeing less than that, at least from an ASOS report. In reality, we're talking about pretty much solid fog.

[oryxs]

:D Have to disagree with you there 212man. We regularly do 600RVR 100'DH landings and we don't find the speed (70 - 80)a problem. Just keep the machine off till you have landings speed. Lower approach speed definitely have advantages but will hurt you if something goes wrong and you have to do a missed approach. Remember you have to maintain at least Vmini for your particular machine. The higher speed also gives you good single engine performance if someting happens and you have to do a missed approach.

GLSNightPilot. Have to agree that night time is a better for low visibility approaches, but it does make the landing more difficult, especially if you have to hold off the machine to reduce the speed.:ok:

[rotorque]

It's interesting that we require approval for a DH of a hundred feet, when in Australia our terrain clearance is a minimum of 100 ft for the missed approach ...... on all approaches.

[GLSNightPilot]

Oryxs, I agree with you on all points. I generally start a deceleration at about 100-200', depending on the weather, planning to cross the threshold at or just above Vmin. You then keep the decel going at 25-50 ft until slow enough to touch down. Slowing to landing speed at the DH just scares me to death; I would never do that. I have a mile or more of runway ahead to slow down on, so I'm not worried about that. After all, fixed wing get stopped from much higher speeds. And in the dark, the landing can be tough, especially with really reduced visibility. That's why my practice is to switch controls when the runway is in sight. IMO trying to transition from instruments to visual passing through 100' is just too dangerous. I've had FOs try to kill me doing that, and I won't do it any more. I prefer letting the FO fly the approach while I keep my eyes on him, and then doing the landing myself. But if I fly the approach, I'll give him the controls for the landing if the ceiling is at or near minimums.