Posts about: "IFR" [Posts: 98 Page: 4 of 5]¶

Just for illustration, this is how it's done in London (or was some time ago last time I did this sort of work). Accurate compliance with routes is strictly enforced and clearances are SVFR day and night unless this has changed. Almost invariably clearance to enter would state the route/s ie 'H4 H3 Bagshot Mast' (straight through) and no other instruction required - that takes you E -W right through the centre of London and out to the W passing 5 miles S of Heathrow. Right hand rule applies and opposing traffic on the route is always advised.
Usually, only if crossing LHR you'd be cleared to enter via requested route with limit Bedfont/Sipson, sometimes Airport Spur to hold (orbit) and change from Heathrow Special to Tower for the crossing itself. There's a further hold at Twin Taxiways between the runways. Altitudes are shown. Note there is usually unrestricted passage on routes H3 and H10 along the river directly under the approach. This system works seamlessly and with - to date - total safety.
Accepted the aairport we are discussing has more varied runway directions than Heathrow so the situation would be a bit more complex but I can't see why a similar system couldn't be devised - with defined clearance limits, sensible vertical separation and, critically, coherent and specific controller voice procedure.

There's no reason not to make landing traffic aware of helos holding close in if appropriate and indeed that happens, but no way is their visual contact required.
The entire system operates on visual 'separation'. Helos cross visually behind traffic as cleared, but with vertical separation. It's as safe as the system can be made. How else could it work? It requires no controller vectoring and the time and space margins that would be required if radar separation was used would render the slick, efficient visual system cumbrous, unacceptably high end unnecessary workload and probably unworkable.
Please, once again let's stop applying this insular f/w procedural IFR mindset to VFR helo traffic. There seems to be a procedural IFR mental blockage that can't see that 'visual separation' occurs in three dimensions, not just two. Helos are perfectly capable of ensuring visual separation as long as the traffic has been correctly identified and with vertical separation as here even if a mistake is made there is 800ft clear vertically. Also, VFR does NOT mean, as many seem to imagine, blundering about randomly at will, it is often every bit as disciplined and controlled as IFR as Shackman reiterates below, these routes are rigidly enforced to within a hundred metres or so and woe betide the transgressor.

The elephant in the room here is a combintion of a ridiculously hazardous two-dimensional crossing procedure combined with culpably sloppy & imprecise r/t which offers no second slice of cheese, not matters of visual separation. I'm well aware that our transatlantic cousins are sensitive to criticism of their relaxed, easygoing and informal ways in the air but in this case they self-evidently were the direct cause of 70 odd deaths. While they may regard European style as excessively pedantic there's no doubt whatsoever that had European standards applied here this event would have resulted in nothing more serious than a MOR and an Airmiss report.

For those unfamiliar the light grid squares are 1Km so the Sipson and Bedfont reporting/holding points is ony about 500m from the runways.

This describes very effective procedural separation between VFR and IFR traffic.

As you've described it, the only place where the Heathrow system operates using visual separation between helicopters and airline traffic is when crossing the airport behind landing aircraft. That's a very different risk proposition to visual separation away from the airport.

Procedural separation has the same benefits in terms of reducing controller workload.

There's the rub. Easy to achieve when the traffic in question is on a runway, such as "cross 27R behind the landing A380"... not so assured otherwise. I stand to be corrected, but I would be very surprised if helicopters using routes underneath the approach had to report and maintain visual contact with each aircraft in the stream as it passed overhead. Separation is built into the procedures: not delegated to the pilots.

Agreed, but what you are describing is procedural separation with 800ft vertical separation.

Not just procedural separation: rigidly radar monitored procedural separation, no less. This is a very, very different thing to visual separation.

I agree with your underlying point that blanket application of IFR separation criteria would be inappropriate. But there are modes of separation besides the false binary of 'visual' and 'IFR' which can be applied to VFR traffic.

Long answer? No.

Short Answer? "__"

The NW wind results in their CAS being lower if maintaining a desired ground speed, and as LW50 and John Dixson would attest to, the crew would be aiming at generally maintaining speed above ETL, to improve ride and economy, noise, pretty much everything. Civil helos will normally specify a minimum IFR speed to keep tracking tasks of the pilot to a manageable level. The crew in this case are night, VFR, but without SAS or ALTHOLD, helos are a bit more demanding than fixed wing. Flying these helos down in the weeds is why Pilots like Lonewolf and John D got paid the big money and have such extravagant retirement life as of course their Government respects their service that much.

I have struggled to understand why PAT requested visual separation the 2nd time given that it had been approved in the first instance.

Perhaps, and this is big perhaps, it's a pavlovian response to whenever PAT is advised of other traffic. I listened to the TCAS RA missed approach from the previous day, and once again the response from PAT is "request visual separation". It's highly likely that the pilot requests for visual separation is the only way that this Class B airspace can operate with the mix of IFR vs VFR, and aerodrome traffic vs transits.

I fail to understand why PAT is using UHF, surely this is another slice of cheese.

The use of RWY 33 for arrival makes it easier for the ATC and the aircrew with one less runway crossing after they have landed. To emphasis the point, the following PSA actually requests RWY 33.

This discussion about the visual separation is a moot point.

Using visual separation as the only line of defence at night (and even during daylight) is utter madness. As is having aircraft circle to multiple runways, mixing high density military and civilian traffic, and a multitude of other issues.

Had full IFR separation been applied this accident wouldn\x92t have happened.

IFR separation is not appropriate for VFR traffic. Class B airspace has specific rules for separation of VFR/VFR and VFR/IFR aircraft. The helicopter routes do not appear designed to provide the required separation for VFR helicopters, at least where Route 4 and RWY 33 final approach cross each other. Was the design at fault OR was the daily application at fault? If the design was at fault, it\x92s an FAA DOD problem. I find it hard to believe the FAA didn\x92t address the correct separation distances in the design phase\x97it\x92s pretty clear. The FAA may have planned crossing traffic wouldn\x92t happen or there\x92s a FAA LOA defining how crossing traffic would be controlled, but the FAA didn\x92t say \x93okay, let\x92s go with 150\x92 vertically\x94.

Did the FAA or the Army assume they would always be able to apply visual (NOT VFR) separation. Visual separation does not necessarily mean 500\x92 vertically and 1.5 nm or radar target separation; it means \x93I see you, I miss you\x94. Did the operating plan always direct crews to use visual separation as the default plan? I hope not, but it is only I see it being written.

Conflating VFR and Visual Separation is driving me nuts. Is this an EU thing?
You can be VFR in the Class B and treated exactly like an IFR flight. The clearance requirement from clouds VFR is just "clear of" clouds. You can have clouds three inches over you and five inches under you with each wingtip 3 inches away from them and still be VFR. This is much reduced from C, D, and E because you are under positive control. The helo was let loose to provide their own visual separation, which is a totally separate thing.

To be specific, para 7.9.4b of the handbook, here:
https://www.faa.gov/documentLibrary/...5-24_READY.pdf

As mentioned upthread, if not visually separated then either 500ft or 1.5mi applies.

Correct if this is all wrong, but in the accident sequence if the helo had responded ‘not visual yet, looking’ or words to that effect, then presumably a controller could allow the two to get a bit closer and then advise the conflicting traffic info to the helo again, say at 2.5mi. If helo visual, great —maintain visual separation, responsibly passes to helo.

This is what happened, although the very busy controller failed to re-state the position of the CRJ to direct the eyes of the helo crew onto the CRJ in order that they could actually see and avoid it.

However if not visual at say 2.5mi, well it’s a bit late, but the controller does still retain responsibility for separation and must apply the 500ft/1.5mi standard. Presumably instant vectors away while simultaneously climb to min vectoring altitude. Or the CRJ has to go around. Can of worms in busy airspace— helos and /or jets being dispersed all over the sky.

Much better to do a rules based system and mutually exclude intersecting IFR app/deps and Helo Visual Routes.

I will not speculate specific to the accident. One more point to add about visual sep then you guys can go back to arguing about the accident. Visual separation isn\x92t just applied aircraft to aircraft. The local controller can observe both aircraft, (even if they don\x92t see each other) and apply visual separation. Such as two aircraft that are diverging but radar separation isn\x92t established.

Could someone explain, how Twr ATCO in that particular enviroment, achieve required separation?
He is not radar qualified- so no headings or radar measurment distances applicable.
Where is prescribed what point is 1,5 Nm away from visual app for rwy 33? ( Note : Atco must achive required separation before that point)
or
At what point should be givem climb instruction for He to be 500' above arriving a/c before compromising 1,5Nm. If rate of climb is 1000 ft/min Helicopet need to climb for 40-50 seconds with the speed 180km/h it is 2 Nm or so - it means that instruction to climb should be given no latter than 4Nm from crossing point.
What is possibikity to spot particular aircraft for visual separation at distances more than 4Nm from crosssing points, duting the night and in bussy traffic enviroment?

Yes , I know it is Burund....

Here you go: Read All About It.
https://www.avweb.com/flight-safety/tower-brites/
This explains the different phraseology between a tower using a BRITE to help out vs. the phraseology of tower certified and equipped for full radar separation. It also explains LOAs for airspace. Where I learned to fly at KMLB the tower only owned up to about 1800 feet IIRC and approach had above that. In those pre-BRITE days it helped a lot for handling IFR traffic.
( I sometimes flew a Bell 47 helicopter there and the tower managed to organize it such that I never came close to any airplanes)

Doing commercial stuff (talking UK here) I was often cleared by Approach for a visual join, say, downwind and then handed to Twr. Twr would then deconflicted me from, say, faster traffic on the ILS. If I had the traffic in sight it was "Extend downwind to join Final as #2 behind the 737 currently on a 3 mile Final. Caution wake turbulence. Report Final." If I didn't have the traffic in sight, or was at all unsure, it was something like "Extend downwind. Report when you have that traffic in sight." after which I'd get onwards clearance on from Downwind to Final. Same at at least 5 other UK regional airports, day or night. Clearly, if the weather was poor I'd be on the ILS anyway so Approach did the sequencing under IFR but mostly Twr had the job. But, as people say, other places have other rules but that was what used to happen to me as standard practice several times a day.

FIT I assume?

as active ATCO I can say only this (to addition to what I've already said) - I will never, ever allow any flying object to cross path of another flying object, especially when one of them is landing. This practice of my US colleagues to frequently offload separation duties to the pilots is just not acceptable. As if there is not enough incident contributing factors, they tend to add some of their own. I said (to disbelief of the attendees) at IFATCA conference just after Uberlingen - let's be honest, at the end of the day, it was ATCO who cleared both airplanes to the same level...
It may sound harsh, but after years of struggle for non-punitive environment, some have deduced this as non-punitive environment for any kind of incident (or even accident).
Back to case in DCA - to expect self separation of night VFR and IFR conducting visual approach agreed hasty and under pressure in the area where none of them is capable of sudden change of trajectory is just pouring gasoline to the fire already raging.

I can think of one: you apply IFR separation standards (the minimum in the US is 1.5nm/500\x92?), at least for night operations. If two routes come closer to each other than that in either dimension, e.g. DCA RW33 approach and helicopter route 1, then traffic must be actively kept apart.

If two aircraft are converging on the same runway or look like they are going to occupy it simultaneously, then one of them has to give way. Why should it be any different for a small volume of sky?

Which, put another way, means no visual separation, and I think that's the right answer. I would commend the DCA authorities also to a scheme we had in London where regular users of the routes such as PAT are given a number to call before planned movements to see if it was likely to come off. Another trick that I've seen is to add a suffix to the callsign for aircraft on a priority shout (eg. helimed).

1.5 nm or 500\x92 is separation for IFR/VFR traffic, not IFR separation. So, an IFR aircraft in VMC might only have those separation distances with a VFR, not IFR aircraft.

Point taken but in reality, a low level (<200\x92) helicopter route is unlikely to have IFR traffic on it? Also, the conflict alerting systems now have real meaning to ATC rather than just being annoyances: something *must* be done to avoid a loss of separation. IFR/IFR minima (3nm/500\x92?) are higher for good reasons.

Indeed , as reminder this is the official ICAO definition of class B airspace :
My bold. so in essence not by one of the pilots. But this is ICAO, not FAA .

I agree that is a solution, indeed the obvious one from my European point of view. What I was trying and failing to think of was a route design which guaranteed separation without ATC intervention, which is what I thought meleagertoo was asking for.

However, from a US point of view, this is arguably the solution which was in place on the night. It's just that the means of actively keeping the traffic apart, ie visual separation, failed. I am prepared to accept that FAA-style "visual separation" is slightly more robust than "see and avoid" in that it requires ATC to confirm that the pilot has the specific traffic in sight before relaxing separation minima, but the question for the FAA is whether "slightly more robust" is good enough when airliners are involved, particularly at night given the increased potential for misidentification.

I am not sure the subsequent line of discussion over how Class B requires ATC (not pilots) to separate all traffic is a very productive one. Any separation instruction given by ATC relies upon the pilot executing it, for instance by maintaining the cleared altitude. Here, it relied on the pilot not colliding with the specific traffic he had confirmed visual contact with. So far as the FAA is concerned, that's a sufficient degree of control and differs from the "see and avoid" principle applicable to VFR/VFR in Class C, and VFR/Any in Class D. Again, the question is whether that's appropriate.

That last point gives me an opportunity to make an observation I've been pondering for a while. Many European airport control zones are Class D, where on a strict reading of ICAO, VFR traffic is not required to be separated from IFR. But how many of us know a Class D zone where the controller gives traffic information and lets VFR traffic merge with IFR under see and avoid? In practice, European and especially UK ATC exercise a greater degree of control than is strictly required by the ICAO classification. At least in my experience, US airspace is operated closer to ICAO specifications ("visual separation" nothwithstanding).