Posts by user "PPRuNeUser134364" [Posts: 7 Total up-votes: 22 Page: 1 of 1]¶

Do you have a lot of time on a 'big junk'? Randomly coming to the hover at night is not like stopping your car at a red light. And not all 'big junks' have auto-hover, particularly free-air hover capability. Even if the Blackhawk does have auto-hover, it may well have limitations and it's not always just a simple case of pressing a button. e.g. is the surface (water or land) suitable for rad alt hold? What are the rad alt height limitations? Is the auto-hover based on doppler? If so, is there a max altitude for its use? The 'big junk' I am familiar with even has a min speed on instruments (not that this was instrument conditions, but it was night which has some similar characteristics).

Despite what some people appear to be suggesting here, in my experience it's not normal just to stop a helicopter to wait for a passing aircraft to fly by.

And maybe even more importantly, why would you stop if you have no reason to suspect that the flightpath isn't clear?

But that isn't the first communication that mentions the CRJ. The heli had previously been told the exact location, altitude, type and which runway the CRJ was positioning for. The heli crew replied that they were visual. It is only later that the controller refers to the CRJ in isolation (with no position) but he is simply querying 'are you still visual with the aircraft that you literally just told me you were visual with?'. There is no need for any night ID skills and even if you don't have a clue what a CRJ looks like, that entire combination of calls still make sense. I agree that if the heli had been made more aware of how proximate the CRJ was then that might have resolved an incorrect SA picture, but the heli had repeatedly told the controller that he was visual. If a procedure is designed that allows a heli to correctly pass under another aircraft by 100-200 feet, at night, is the controller really supposed to be able to judge from the tower whether they are extremely close (as would appear to be the case if they were both on the correct path) or if they were on a collision course?

If that was a hold in the hover, it would likely have been a low hover on a cross runway (or another safe place on the airfield). I would be amazed if Aberdeen asked a heli to hold in the hover, offshore, at height, at night. Aside from the disorientation issues, it isn't a comfortable place for a heli to be in case of a malfunction. If I was coming back to Aberdeen from the North Sea and was asked to hold to the east of Aberdeen, away from the airfield, I would fly a racetrack/orbit.

What do you consider 'so terribly close'?

When the CRJ traffic was first called to the heli, and the heli acknowledged that they were visual, the CRJ looks to have been around 4NM south of the field.

NVGs probably aren't ideal in that environment and I haven't seen any factual statement that they were using them. Even if they were wearing them it doesn't mean they were actively using them (it is usually possible to lift them up out of the way). My only concern would be flying below 200ft, at night, across multiple bridges in an environment where there may be obstructions (not knowing the specifics of that portion of airspace). It may (or may not) have been advantageous to have one person using NVGs for ground collision avoidance, but it's a balancing act that depends on the conditions on the specific night.

I am not a USA airspace expert, and I'm sure there are many rules that I don't know about, but having just read the FAR AIM section on 'pilot-applied visual separation' it reads to me, as an interested foreigner, that the LC can pass responsibility for separation to a pilot if they are visual. The class B separation criteria states:

VFR aircraft must be separated from VFR/IFR aircraft/ helicopter/rotorcraft that weigh more than 19,000 pounds and turbojets by no less than:

1. 1 \xbd miles separation, or
2. 500 feet vertical separation, or
3. Visual separation, as specified in paragraph  7-2-1 , Visual Separation, paragraph  7-4-2 , Vectors for Visual Approach, and paragraph 7-6-7 , Sequencing.

The rules for pilot-applied visual separation state:

1. If the aircraft are on converging courses, inform the other aircraft of the traffic and that visual separation is being applied.
2. Advise the pilots if the radar targets appear likely to merge.

Whilst I agree giving avoidance instructions would possibly be a sensible thing to do, I can't see that explicitly written in the FAR AIM if pilot-applied visual separation has been approved. There may be other sections (or other regulations) that go into more detail that I am not aware of.

Are you sure that they didn't have the traffic on their display?

I know I'm fighting a losing battle but here goes.....

What you are doing wrong is making guesses based on incomplete/inaccurate data that is in the public domain.

Assuming the NTSB figure of 375ft is correct, you still need more info for it to mean anything. Was that the AGL, AMSL or SPS height/altitude?
How accurate are the 'various plots' that indicate the collision occurred mid-river? They may be right; they may not be.
Was the CRJ on final or was it still positioning to final? If it wasn't on final then the trigonometric calculations of what height it should be at might not be correct.
What official evidence is there that the Blackhawk made a 45 degree turn, or could that be a data error in the publicly available information?

In summary what I am saying is that, despite all of the internet sleuths plotting tracking data, none of it is official and it is all subject to various errors. Whilst interesting to form an understanding of the circumstances, it can't be assumed to be accurate to within a few feet (vertically or laterally).

That 1-2 feet error would be a theoretical accuracy. The readout in the cockpit would be subject to significant errors during turns/pitch changes etc; without knowing the exact installation on a Blackhawk, it might also unlock based on the surface conditions. More importantly, the ATC instructions would probably be based on an altimeter setting and not Rad Alt.

How would that have worked in this scenario? Who do you think should have been directed by TCAS to do what? Does the Blackhawk even have TCAS?

Do you honestly think that you've just thought of that and the system designers haven't?

In relation to your earlier response to my previous comment, how can the system tell someone to 'remain level' when that aircraft doesn't have TCAS? I am not sure of the Blackhawk fit, but I would be pretty surprised if it has TCAS fitted.

One of the main reasons that TCAS alerts are inhibited at low altitude is to avoid distraction during the landing phase, in an area that has a high traffic density and a high probably of nuisance alerts. The system would constantly be giving RAs and people would be going around and deviating all over the place. Even if just TAs were left active then it would be going off all the time, and we would be having the same conversation about becoming blase to the warnings as we are about the repetitive conflict alerts that were being given to the LC.

Getting TCAS to give RAs on final is not the solution in my opinion.