Tenerif... AUSTIN!

[Gabriel]

https://www.youtube.com/watch?v=DjoDn8zQgb8

http://avherald.com/h?article=504bc65b&opt=0

https://twitter.com/jxlars/status/1622010477520764928

I am copying below the comment by some obscure member of some other obscure aviation forum:

At a ground speed of say 120 miles per hour (to make the math easy) an airplane is making 2 miles per minute. That is 1.5 minutes to touchdown. Taking into account the time it takes to position the plane from the hold-short line to the centerline and spool up the engines, accelerate and lift off, it is basically impossible that the departing plane will be airborne in the 1.5 minutes it would take the arriving plane to touch down. So why clear the departing plane to take off with a another plane 3 miles out? Especially in IMC. And let's not even talk about a possible aborted take off, let alone an accident during take off that may leave the pilots of the departing plane unable to contact the tower, and the tower unable to see the departing the plane in these low vis conditions.

2 things here that I don't understand and that I dislike and that are unlike what is done in most of the world.

1- Clearing a plane to take off with another one 1.5 minutes from touchdown, in solid IMC where the pilots of the departing and arriving planes cannot see each other and the tower can see neither.

2- The "in-advance" clearances to land, where a plane is cleared to land with another plane cleared to land or take off on the same runway ahead of them. In most of the world that is illegal, nobody is cleared to occupy a runway unless the runway is already clear and expected to remain clear until the cleared plane occupies it. What you have instead is the delayed clearances, like "expect landing clearance on short final". If the arriving plane did not receive the clearance (which would only be received when it is confirmed that the runway is currently clear and expected to remain clear), then they have to go around.

This is a terrible accident waiting to happen. Something similar happened with that Delta flight 1086 (MD-80) that went off the runway when landing at La Guardia. They lost comm due to equipment damage during the accident and could not tell the tower what happened. Another plane was already cleared to land after them. The tower had no idea of what had happened (due to low visibility). Very fortunately, an airport vehicle in the vicinity saw what happened and told the tower, who in turn told the approaching airplane to go around.

I don't know if I am the only one, but it is SO obvious to me that this practice is as unsafe as it is unnecessary, and there have been a few close calls do to it already (no accident as far as I know). Why wait until an accident happens and somewhere between 150 and 600 persons are died to fix it?

I have seen cases where, in situations like this, the departing pilot said "I will wait until the approaching plane lands". Bravo for them, but it should not take that to avoid a dangerous situation.

[Evan]

Once a ground aircraft proceeds past the CAT III hold-short line, they are entering the protected area and potentially distorting the ILS signal. For that reason alone, no aircraft should be in that protected area during low visibility operations when another aircraft is on final. Am I right?

[Gabriel]

Once a ground aircraft proceeds past the CAT III hold-short line, they are entering the protected area and potentially distorting the ILS signal. For that reason alone, no aircraft should be in that protected area during low visibility operations when another aircraft is on final. Am I right?

Probably, but I don't care. What if it's not an ILS approach but a GPS/WAAS LPV approach?

My concern is having a plane landing on top of another.

[Evan]

Probably, but I don't care. What if it's not an ILS approach but a GPS/WAAS LPV approach?

My concern is having a plane landing on top of another.

That also concerns me but if an airport operation is going to ignore ILS protection rules, why should they care about separation either? You either have a safety culture or you don't.

What really concerns me here is why there is no oversight and enforcement of safety culture at a US commercial airport.

[Gabriel]

Evan, I don't know if you noticed that I am pissed off with LEGAL and STANDARD OPERATION advance clearances, which are up to the standard of the current most strict safety culture in the US.

[Evan]

Evan, I don't know if you noticed that I am pissed off with LEGAL and STANDARD OPERATION advance clearances, which are up to the standard of the current most strict safety culture in the US.

Yes, I agree. It is indicative of a compromised safety culture. But it isn't the only indication. If you actually choose to put safety first, you don't ever put it second.

[Gabriel]

Is the real person behind your screen name the same one than a couple years ago?

[Evan]

Is the real person behind your screen name the same one than a couple years ago?

Maybe I don’t understand what you mean by “in-advance” clearance but in low visibility, late landing clearances should not be happening inside of 3nm if safety is truly the principal concern. The danger is not just of a landing collision. A go-around must also be executed with enough advance to assure a safe separation.

I was pointing out that safety is not the principal concern if you are also moving taxiing aircraft beyond the CatIII hold-short marker and into takeoff position when an arrival is on final in low visibility. The FAA clearly states that this is not allowed.

True safety requires redundancies.

[3WE]

Is the real person behind your screen name the same one than a couple years ago?

Gabriel, I very much disagree that US-style cleared to land had anything to do with this incident.

From the audio tapes, everyone seems informed of the situation except maybe SWA.

Upon further thought, I’m seeing SWA as the biggest bad guy. “Cleared for takeoff, traffic on a 3-mile final” is something I heard a lot at Flyover. The simulation cartoon shows them CRAWLING into position. Whether that’s accurate, or not, the bottom line is the same- they were unusually slow in getting going.

The other thing I heard at flyover was “Traffic, 2.5 mile final, cleared for immediate takeoff”. It SHOULD have worked here with the spacings at the time of TO clearance.

Contributing factor: Chatter at AvHerald about “deicing run ups and maybe ALSO icy taxiway taxi speeds.

Additional factor: I am guessing the controller violated IMC separation…There was a good bit more separation when Flyover was IMC.

Final factor, I agree that ITS may have continued a bit too far.

But for this instance, there isn’t anyone who has FORGOTTEN anything because they were cleared to land early on.

As to your quote: it’s the same old black and white Evan…I mean he has a point…lax safety is lax safety. But I agree he has a new level of getting totally stuck on a single detail that has really low relevance. It’s in the ball park, but WAAAY out in left field….maybe the far corner and facing the wall…not enough fresh O2 in the sterile bubble…Kudos to the FedEx crew for not making a 60-degree bank to avoid SWA /tiny pretend blue font.

[Evan]

After watching the video, it seems to me that the only safety culture at work here was the one of FedEx 767. The tower should not have cleared the SW 737 for departure at that point. The SW 737 should not have accepted the clearance with traffic on 3nm final in low visibility. Only the FedEx 767 recognized the danger, initiated the go-around, instructing the SW 737 to abort. The SW 737 did not follow that instruction or the tower instruction to turn off (perhaps feeling it safer to proceed than to slow down on the runway).

So, are you saying this is SOP, issuing 'in-advance' landing clearance in limited RVR IMC with aircraft still lining up for departure? I can understand late clearances if they come no later than 3nm out AND the runway is actually clear. But otherwise, this entirely defeats the purpose of landing clearances.

[Gabriel]

Gabriel, I very much disagree that US-style cleared to land had anything to do with this incident.

From the audio tapes, everyone seems informed of the situation except maybe SWA.

Answer this 2 questions:
a) What would have happened if the FedEx guys had not initiated the go-around? (which was a distinct possibility given that they were twice confirmed to be cleared to land and were in shitty visibility conditions and were in a CAT-III approach / autoland where they are supposed to be looking mostly/only at the instruments and not out of the window where there is mostly nothing to see due to the terrible vis)
b) What would have happened in this same situation, if they were NOT cleared to land and told to expect a last-second cleared to land? They would have been REQUIRED not to land and to initiate a go-around, unless they got the landing clearance which, under "my" model ("my" actually meaning "most of the world's"), the Tower would have not granted until they had confirmation that the Southwest was either airborne or clear of the runway.

Being "informed and aware", being able to see and avoid, and being cleared to land are all very different animals.

Even if this was a violation (or at least very poor judgement) by ATC, we need layers of swiss cheese to cover the holes in other layers.

Upon further thought, I’m seeing SWA as the biggest bad guy. “Cleared for takeoff, traffic on a 3-mile final” is something I heard a lot at Flyover. The simulation cartoon shows them CRAWLING into position. Whether that’s accurate, or not, the bottom line is the same- they were unusually slow in getting going.

https://www.youtube.com/watch?v=3AbA-v_vOhg&t=75s

Clock it.

The other thing I heard at flyover was “Traffic, 2.5 mile final, cleared for immediate takeoff”. It SHOULD have worked here with the spacings at the time of TO clearance.

Explain to me the spacing and time, how it should have worked, because in my math (as you summarized my quote to a single word there) this was extremely tight even in severe VMC.
You have math that shows otherwise? Good, I want to see it.

Remember it is a 767 in a 3-miles final, not a Cessna 172.

Contributing factor: Chatter at AvHerald about “deicing run ups and maybe ALSO icy taxiway taxi speeds.

No ice in Austin on Saturday. We had A LOT of ice from Tuesday to Thursday but all ice was gone by Friday mid-morning.
Power outages on the other hand seem to survive longer than ice after the bad weather goes away.

[Gabriel]

So, are you saying this is SOP, issuing 'in-advance' landing clearance in limited RVR IMC with aircraft still lining up for departure?

It is SOP (in the US, but not in most of the world) to issue landing clearances when the runway is neither clear nor expected to remain clear, as long as it is expected to be clear by the time the airplane lands. In ILS conditions there are additional requirements, but I am not very familiar with those. I think that the ILS protected are must remain clear when there is an approaching plane past the FAF (which in Austin is 3.3 miles out.

Regardless of specific weather conditions, in-advance landing clearances are issued all the times including in conditions where the tower cannot see the runway or the airplanes (except on radar) and where pilots can see other planes until it is dangerously close. Did you read what I put about Delta 1086?

I can understand late clearances if they come no later than 3nm out AND the runway is actually clear. But otherwise, this entirely defeats the purpose of landing clearances.

That is not practical and not needed. It is perfectly ok to clear a plane to land 1 mile out (or even less) when the departing airplane just lifted off, or the preceding landing airplane just cleared the runway. The pilot knows that they are NOT cleared to land (until they are) and they can and should execute a go-around at any point they feel it would be unsafe to continue the approach without the landing clearance. Pilots routinely go-around 200ft AGL when they reach CAT-I ILS minimums and can't see the runway. That would be about 0.5 miles out.

[Evan]

b) What would have happened in this same situation, if they were NOT cleared to land and told to expect a last-second cleared to land? They would have been REQUIRED not to land and to initiate a go-around

I don't know the class of CAT III involved, but we know minimal DH is either 100ft, 50ft or there is no DH. If we are speculating what might have happened had the 767 continued down to DH of 100ft or 50ft anticipating last second clearance, then gone-around due to lack of clearance, I'm not sure it would have been possible at that point to avoid a collision during the go-around.

But that also leaves no contingency for error or the unexpected. Margins for these things must always factor in.

The 767 initiated a go around from about 150 feet AGL about 1000 feet short of the runway threshold, climbed to 3000 feet MSL overflying the runway

[EDITED]

I was trying to figure this out. They reportedly went around at 150 AGL when 1000ft short of the threshold. The report claims they overflew the runway at 3000 MSL, which would be about 2450 AGL. Using your 120mph suggested ground speed, or 176fps, and assuming the ground distance between the go-around and the time that the two aircraft are vertically aligned is 5600ft (4600ft down the runway, about halfway), that would require about 30 seconds, not factoring in any speed variation. To go from 150 AGL to 2450 AGL in 30 seconds would require a climb rate averaging 4600 fpm, which is about twice the 767's max climb rate, so that reported altitude over the runway must be incorrect.

If the report meant the 767 reached 3000 MSL by the runway end, that would require a climb of 2300ft over a ground distance of 10,000ft, which would translate to about 57 seconds at a ground speed of 120mph and a rate of climb slightly higher than 2300 fpm.

I'd like to know what the actual minimum vertical separation was over the runway. Assuming a max climb of 2000 fpm, I'm guessing it was under 1000ft of vertical separation.

The 767 initiated a go around from about 150 feet AGL about 1000 feet short of the runway threshold, climbed to 3000 feet MSL overflying the runway

No, this is wrong. The 767 was instructed, while overflying the runway, to climb to 3000. We have no reference for its actual altitude when overflying the runway, and the other plane.

Maybe you can help me out there...

[/EDITED]

[Evan]

Best guess on 767 altitudes over the runway based on 120mph constant ground speed and 2100 fpm constant climb rate (neither or which is accurate):

350ft at runway threshold,
1250ft at runway midpoint,
2100ft at runway end.

I don't see how they could be much higher, but they could certainly be lower.

[Gabriel]

I don't know the class of CAT III involved, but we know minimal DH is either 100ft, 50ft or there is no DH. If we are speculating what might have happened had the 767 continued down to DH of 100ft or 50ft anticipating last second clearance, then gone-around due to lack of clearance, I'm not sure it would have been possible at that point to avoid a collision during the go-around.

It would be absolutely possible. The landing plane would be going around from a point just shy of the threshold. The other plane would lift off some 3500 ft down the runway. The going-around plane would be easily 500 ft AGL by then, and still climbing. So even if one was exactly on top of each other they would not crash immediately and it would give time to take other evasive maneuvers (tell the taking-off plane not to exceed 1000 fpm, turn the going-aorund plane away) before the taking-off plane reaches the going-around one in the assumption that the former has a greater climb speed.

Maybe you can help me out there...

Not sure how, I don't have any better data that you do.

If the 767 went around at 150 ft, they were some 0.3 NM short of the runway. That must have been the point of minimum lateral separation. Then the 767 caught up with, and put themselves on top of, the 737 that was accelerating for take-off. Thar was the point of minimum lateral separation but in my estimation, as I said before, by then there must have been at least 500 ft of lateral separation.

500 ft is not a lot, and is not legal, but it will keep the plane from mating with another plane.