Increasing tech and decreasing separation.

[KL-666]

Hello Jwocky,

Actually this was a case of trusting automation too little. It was a tcas situation. Then one plane gets a climb and the other gets a descend instruction. A tcas instruction must be followed in any circumstance.

Unfortunately the slightly overloaded ATC just at that moment looked back from another screen, and in his startle he gave the Russians the opposite instruction from what they got from tcas. The Russians chose to follow ATC and now did the same as the DHL plane did (climb or desc).

Since tcas goes before everything else, the Russians were at fault to not trust the automation and let the ATC instruction prevail.

Kind regards, Vincent

[jwocky]

Yeah, I remembered this case only foggy. The question is, they assumed, technology had failed them ... right? So, one problem with technology is, you don't know exactly when it fails, it's not always that all screens go blank, that would be obviously, but what about wrong data? The same of course is true for ATCs. You hear what he says, but is it correct? You simply have to assume, all you get is correct.

[KL-666]

There are levels in which you can trust something. There has never been an issue with PFD instruments, except once when the measurement holes in the body had been taped off. Unreliable airspeed is not a problem. When airspeed gets weird you crosscheck with the other 2 airspeed indicators (other pilot and backup). So one can say that PFD instruments are very reliable. Many accidents happened by not trusting the very reliable PFD instruments. Not the other way around.

Very unreliable is thinking you can feel better than the PFD instruments display (vertigo). And another fallacy is the flight director cross hairs. The FD is not about the correct action to take when you are at low energy, because it just indicates where the planned flight path is. It shows you to go back up to the planned flight path, while you almost stall. If you would have read the PFD instruments you would know better. So the FD should not be followed when in trouble.

Again the PFD instruments are trustworthy and should be used instead of anything else. Training should emphasize that.

Btw, i have also never heard of an incident where TCAS gave wrong instructions. So it is very trustworthy too.

Kind regards, Vincent

[jwocky]

Okay, I agree on PFD plus backups. I don't agree entirely on the TCAS because it's radar based. Means, if you have bad weather ahead, behind it can be anything and there are also a lot of little aircraft which are are radar targets too small to appear clear (the rada echo could be smaller than the suppression granularity). So, in doubt, since the PFD doesn't show other traffic, would you trust TCAS or an ATC?

[IAHM-COL]

would you trust TCAS or an ATC?

Is this an option?

[jwocky]

Well, if TCAS says down and ATC says up, it kind of is?

[KL-666]

Tcas not really radar based,but more like transponder (information) based. Both aircraft must have it installed to let it work. Both aircraft need information of the others alt, speed and heading. Weather between them can not be a problem, unless it distorts the information transport. But in that case it is just like meeting an aircraft without tcas installed. There will be no tcas instruction. But if there is a tcas instruction, it is correct and must be followed. It has never failed.

@iahm-col: As i repeated several times, in aviation it is mandatory to follow tcas before anything else, so there is no option.

Kind regards, Vincent

[jwocky]

Okay!

[IAHM-COL]

@iahm-col: As i repeated several times, in aviation it is mandatory to follow tcas before anything else, so there is no option.

Kind regards, Vincent

That's good. Makes tremendous sense.
(phew!)

I remember in our simulated world when an ATC cleared us to descend like 500 below AGL and we say... no way. not happening. I can only imagine a similar knee-jerk reaction such thing would happen RL. (it was a USA Tour event, arriving to Billings, MT)

[HJ1an]

Well, if TCAS says down and ATC says up, it kind of is?

And the pilots would have to make a decision quickly, at that point it kinda becomes a matter of "pick one and just go with it". Which could be disastrous. Of course, if the lesson is learned, go with the TCAS; but if the TCAS has been previoiusly giving false positives; or not even the TCAS; but the plane itself have been giving false positives, how would that affect decisions?