Posts about: "See and Avoid" [Posts: 45 Page: 1 of 3]¶

How did the top many measures that are in place to prevent this not prevent this?

TCAS
ATC
ADS-B
See and Avoid
Filing a flight plan
Not operating in controlled airspace without a transponder
Not operating at a landing altitude for aircraft on final for a well used runway
Announcing an intention to cross a well used approach
Position lights/strobes
Landing lights

Just spitballing, but there's a non-zero chance NVGs were in use in the helicopter.

It sucks that the best part of this is the airplane was a CRJ, not a larger airliner. Most all those passengers would have survived the initial collision and been aware during the fall to the river.

I feel rage.

The military helicopter did have a Mode S transponder, but no ADS-B out. The CRJ had a standard transponder with ADS-B out. In all my data sources, the helicopter is visible but only as an MLAT target, so its position in all the flight tracking feeds (ADSB Exchange and FR24) is inferred via time of arrival difference of the Mode-S signal at various receiver stations in the area (i.e. within 200-300m position precision).

TCAS however can operate off Mode-S signals alone, but as others have pointed out, during the late approach phase of a flight, TCAS RA is inhibited (but the target would have caused a TRAFFIC alert still and shown yellow/red on the TCAS display). The helicopter crew assuring the frequency they have identified them would have led them to believe they were cutting it close but will avoid.

It would have been a luck of the draw situation for the CRJ crew to see and avoid the helicopter. It's very hard to see a couple of light points moving against a sea of ground point lights at night. Assuming the CRJ had its logo light on, their only chance would have been for the helicopter crew to spot them (which they claimed they did?)

what is a \x93non-zero chance\x94? Is it the same as a chance or more like a certainty? Confused by what seems like an American expression.

Crossing runway finals at 200' at a distance that puts you wthin reach of the circling jet- tempting fate. TCAS in TA only, not RA by height, No ADSB In or Out improvement in this regime.

Final hole, see and avoid- target invisibe, sighted AAL3130 on Rwy1 straight in, not enough dissonance in all that to realize you cannot be following that next plane...

The nasty thing about 'see and avoid' is that exactly the stationary situations where relative position/angle does not change is the collision setup. And this over a sea of lights of a big city at night.

Almost astonishing that this hasn't happened earlier

That is part of the safety lectures' I gave ; in VFR ,using the see and avoid concept, the danger is not the one you see but the one you do not see and : : You can fly as safe as you want , the danger will come from someone else which does not ". .
Airliners cockpits are not designed for see and avoid.. not on daylight , so much worse at night where distance of lights is almost impossible to determine

yes me too but above Nevada , not under the Glideslope close to a runway of a major airport at night ..

I have not read many of the earlier posts, so do not know what has been said about ATC’s involvement & whether the helicopter was operating under IFR but, it would appear that the helicopter was operating under VFR & simply being given traffic information, rather than being IFR & being properly separated from other IFR traffic (the AAL a/c in particular). If so, this accident revives the controversy about whether or not you can safely mix dense IFR traffic & VFR traffic in the same airspace. Without knowing the actual cause of this accident - there may be some other cause - it would seem to suggest that the answer to this question is, “NO, you cannot”. I remember giving traffic information to a departing HS125 , from Aberdeen, about a Cessna 150 operating within its projected flight path at up to 5,000 ft. 6 nm west of the airfield ; & being met with the reply from the 125’s pilot, “what do you expect me to do with that info ?” Thinking about it, he had a point. Simply being informed about prospective traffic does not guarantee, in any way , that you are going to be able to see & avoid it. Countless collisions between (mainly light) a/c since; plus this latest tragedy; would seem to prove the point !

But it's worse than that. The approaches to DCA are only moderately complicated; however, unlike most airports, DCA is surrounded with frustrated people just waiting to call the FAA if you deviate from the published procedure by the slightest amount. Nobody want's to do a rug-dance in the Chief Pilot's office because some Senator's aide gets his/her panties in a wad, or worse, get a violation from the FAA because you flew over someone working for the Secretary of Transportation. I always enjoyed flying in and out of DCA because it was challanging, but I was always on my toes, constantly checking my altitude, position (both visually and via instruments), airspeed, etc. because it is so easy to get your teat in the wringer at DCA.
In this case, the aircraft was flying an approach to one runway with a circle-to-land on RW-33. Ask any pilot; a circle to land in itself ups the work load. The margin for error of any kind at DCA is small and the 5200 foot runway isn't all that long. Even on a simple landing where none of these considerations are an issue, at some point the pilots reduce their "see and avoid" efforts and concentrate their efforts on achieving the proper line up and glide slope, rate of descent, aircraft configuration, flap setting, etc. etc. etc. In other words, the complicated routine required to safely land an airliner these days is already close to task overload even when things are going well. Add in the fact that it's night time at a very busy airport and looking out the window gets shoved pretty far down the "to do" list. But generally speaking, the system works because big busy airports pretty much operate using IFR rules and nearly all the aircraft are under close control. I other words, even on a crystal clear day under VFR flight conditions, someone is keeping a very close eye on the airliners coming and going from major airports. If a pilot makes a mistake and levels off at the wrong altitude, for example, there is a very good chance a controller will catch that error immediately even on a sunny VFR day. And that's a good thing because truth-be-told, when an airliner is seconds from touch down these days, there isn't much "see and avoid" going on. That's just the way it is.

But apparently DCA routinely has all sorts of helo traffic buzzing around under modified VFR flight rules. The pilots are talking to a controller but without being under the same sort of close control which is usually associated with how airliners operate. And they do that night and day, trusting the helo pilots to not make a mistake. But it looks like someone DID make a mistake last night and nobody caught it in time.

See and avoid in airline operations simply does not work. High workload, human factors, visual limitations, high closing speeds simply make it unreliable.

There have been countless similar cases of near misses. Near airports, crossing traffic, especially helicopters is a real issue, as is the totally inappropriate see and avoid principle with commercial traffic. In my view we need a complete rule change and rethink around lack of radar separation between IFR and VFR traffic.

All too frequently ATC allow IFR and VFR far too close on approach and are permitted to just inform the VFR traffic to visually manoeuvre themselves all too close to IFR traffic. The book 'The Naked Pilot' years ago established that see and avoid does not work, simple as that.

Class D airspace whilst not necessarily involved here often causes such issues. Pilot's wrongly believe ATC separates IFR and VFR. Frequently ATC allow conflicts to develop on the basis of law, rather than duty of care. We need to get back to common sense, and that is ATC must stop VFR traffic getting anywhere near airliners on final approach or from crossing the go around track. Either lateral or vertical separation needs to be enforced or repeats of this type of accident will definitely repeat.

Lessons have not been learned previous to this accident. I fear we will see a repeat, and low level near airport ATC separation needs to improve.

We need the industry to wake up and realise, see and avoid is unreliable, and air law does not protect IFR traffic from VFR traffic enough.

the industry, and in Washington the military and the State, knows this, but chooses movement rates and freedom over delays and failure to deliver. Aviation is not zero-harm. This is a risk which is well established as tolerable, the rate of occurrence seems acceptably low overall, and I suspect nothing will change. Those affected should, in my opinion, be enormously compensated, which will not bring loved ones back but will make going on more tolerable, and will enable the status quo to continue, satisfying the commercial, capitalist, military, and executive imperatives. I’m often reminded of the scene in Airplane, which cuts to the made-up TV talk show, ‘Counterpoint’, whose host says (and I may be a word or two off here), ‘I say, they bought their tickets, they knew what they were getting into…. Let them die’. Macabre I know, but feel free to challenge me if you don’t believe that this is a true reflection of our reality.

The object that is on a collision course with you is stationary or nearly stationary in your field of vision, if you can see it at all. It may or may not be moving noticeably against the background. The objects that are obviously moving are highly unlikely to be of any concern. It's been demonstrated through decades of experience with midair collisions that see and avoid simply doesn't work. Where avoiding midair collisions depends on see and avoid, midair collisions will happen. Infrequently of course.

I totally agree with all that has been said about the appalling R/T from the Tower Controller. Even with over 40 years of experience it is extremely challenging to understand all the he says. Not untypical at many US airports.

More to the point is that those two aircraft should not have been there at the same time. If an aircraft is cleared to fly an approach to RW 11 the Low Level Helo route should be closed until the aircraft is on the ground. Whoever or whichever organisation designed that procedure is totally at fault. The situation should NEVER have arisen.

Anyone who believes that "see and avoid" in that airspace AT NIGHT is living on another planet.

Well unlike the Korean accident I think we know what happened here. The solution when it comes wil depend on the level of risk those in authority are prepared to accept in order that business can continue. In my opinion

A minimal response might be to review staffing policies in the tower; if radar equipped it would help to have someone solely responsible for the heli lane situationally aware of inbound traffic to the airport. If more change is acceptable then the heli routes should be examined and probably redesigned and traffic levels at Reagan at least examined.

I can see no reason to close the airport. Yes it is constrained and has short runways but many airports are similar. around the world. London City here is examining whether it can accept Airbus 320 neo aircraft with a 4965 foot runway and steep approaches in a very built up area.

There are wider issues - why do so many controllers sound like disk jockeys in the US whereas here they do their very best to sound calm.

I do believe some changes will come - just as line up and wait was introduced I believe the current clear to land will be replaced by continue approach and then clear to land only where it means that - the runway is clear and I know of no conflict to affect your landing. With this, some clearances still need to be conditional - At KDCA clearance to and 33 might be conditional on 01 traffic. Bit overall it is just clearer - and can be accommodated by most tower controllers given what thy have to deal with AFAICS.

Finally the suitability of see and avoid to night time operations will have to be examined.

I have been watching this thread for a while now and felt compelled to respond, mainly due to some of the comments on here, a proportion of which, come from professionals within our industry which in itself is troubling.

Lets break it down based on what we know so far:

See and Avoid We have years and years and years of evidence about the limitations of see and avoid. It is not and never will be effective mitigation to a collision risk on its own. It needs to be backed up with other barriers such as ACAS etc. The human eye is particularly bad at spotting stationary objects, which would have been the case in this instance with another aircraft on a steady bearing. Those who criticise the aircrew for not keeping a good lookout are being disingenuous. The ability to judge distance at night, is difficult. Those who suggest the helicopter was looking up at the night sky, omit to recognise that the cameras on which you are basing that opinion, were at ground level. The crew of the Helo would have been at a similar altitude, looking at a background of many lights, with other aircraft barely above the horizon. The reports state that the aircrew may have been on NVG. This exacerbates the issue as they narrow your field of view, make depth perception even worse and of course, those I know of, do not display different colours, such as navigation lights. So see and avoid needs to be backed up by other measures and one can also see how VFR at night is fraught with danger.

Procedures - There is nothing inherently wrong with helicopter lanes close to aerodromes as long as the procedures that control such traffic are robust. I do not know what the local procedures state for routes 1 and 4 but I would expect them to include a limitation to ensure that you cannot use route 4/1 if an approach is being made to Rwy 33 or vice versa, an approach cannot be made to Rwy 33 if there is traffic on route 1/4. If such a procedure does no t exist then we could argue negligence. Lets assume one does exist. In that case, I would expect some process to block the route or the approach, using an aide memoire such as a flight strip or other electronic means. The recent crash at Haneda, highlights the need for such a safety barrier.

The Controller - Reports suggest that controller numbers were down to 19, which is woefully inadequate for an operation such as this and I hope the NTSB looks at what actions were taken by the airport to close in the face of staff limitations. We assume from reports, that the controller concerned was working in a combined position, with band-boxed frequencies. Looking at FR24 replays, it was quite busy at the time and we also do not know what level of fatigue the individuals were under. If the procedures above were in force, was a blocking strip forgotten? Was the controller overloaded or distracted? I hope they were not combining Radar and tower!

Phraseology - Others on here have mentioned about phraseology used. First of all, I cannot understand this machismo, that US controllers have to speak fast. Stop it! It is dangerous and you only end up having to repeat yourself. Others have mentioned about using the clock code. The Tower controller may not have the endorsement to use radar procedures and may have been forced to use geographical points. From what I have heard and yes lets wait for the report, it seems that the phraseology used was sub optimal.

Duty of Care - Some of here have spoken about the transfer of responsibility onto the helicopter operator. This is a pet hate of mine, of people hiding behind the rules to abrogate responsibility. Everyone in the system has a duty of care and Air Traffic Controllers, regardless of type of service, have an accountability to do what they can to prevent collisions. That is written into the highest levels of ICAO Annex 11

My condolences to all involved and my thoughts are also with those under investigation, who I feel may have been let down by the system.

'See and avoid' at night over a well lit city is absurd, I agree.

Another iootionto make it safe was suggested elsewhere. Have an either/or arrangement.

If an airliner is on approach to runway 33, Heli Route 4 is closed.
If a helicopter has had approval to fly along Route 4, the approach to Runway 33 is not available.
Simple and straightforward?

Well said and reasoned.

The losses so far in this case are almost defined, except that the unfortunate ATC officer is a victim of nothing more than being human and working within the constraints of a system that he did not design or have responsibility of. He has the most powerful pumpkin in the world defaming him from the normalised position of gross ignorance to such an extent that even Fox news and CNN push back. I would suggest that a suicide watch be placed on this poor individual to protect him from the hurtful comments that exude from the incumbent of the WH. This guy is going through hell, as much or more so than any other person suffering the loss in this mishap.


PS:

Humans may be the frail part of the system but they are also the most resilient parts. We will have moments in the following months to doubt that, history highlights failures not successes.




C ommercial aviation demand outstripping capacity
O ver reliance on "see and avoid" in ATC
M ixture of military and civil traffic in terminal areas
P olitical interference at Federal level
L essons not learned from previous incidents
A TC shortages and chronic understaffing
C omplexity of airspace around major cities
E quipment and technology outdated or inadequate
N ormalisation of deviance
C onvenience chosen over safety
Y our luck runs out

Yes, the CRJ could have not accepted ATC's request to divert to 33. They would have then been set to go around to set up again for Runway 1, the usual runway.

ATC put the CRJ on an intersecting runway, which added complexity to the pattern picture. The helo would have only had to hold for a short time to wait for the CRJ that was diverted to a runway not normally used for commercial air carriers.

Knowing that, they asked the helo to maintain visual separation, placing everything on that crew to see and avoid the CRJ. I have read that they didn't even tell them where to actually look to see the traffic, no bearing, no altitude. The helo likely saw traffic, just not where they were supposed to look. There were plenty incoming and departing Runway 1, which is why the CRJ was asked to divert. Add to that, both aircraft were low and operating over an urban area at night where it is difficult to see other aircraft. Worse even if the helo crew was using NVG.

ATC should have held the helo short, waiting for an unusual approach to a runway not used normally, so to let the CRJ pass. The CRJ crew was already saturated in tasks at the time I have not hear ATC asking them to look out for the helo.

IMO, ATC created a "single point of failure" relying on the helo to see and avoid the CRJ. Had they held the helo, and helos can hover, for even a minute, this doesn't happen. ATC's main purpose is to keep aircraft from occupying the same place at the same time. In this case, they didn't.

I am sure that the helo pilots made]mistakes. But, this appears to be a massive failure of ATC.

See and avoid will always eventually produce midair collisions because physics, geometry, and humans don't permit see and avoid to work flawlessly.

This incident follows the same script as decades of others where ATC verifies that a pilot has the (incorrect) traffic in sight and shortly afterward there is a midair.

See and avoid works well most of the time. It's the rest of the time that needs to be addressed. Normally one tower for fixed wing and another for helo traffic during busy hours at this field. One was apparently released early so the remaining on took on a high workload. That may have been the first hole in the cheese. Stepping back the whole scenario seems to be an accident waiting to happen. The Feds, local authorities or whomever should have dictated a minimum of two tower controllers during these high workload time frames.