Midair Collision over Denver • Hacker News Board

Re: Midair Collision over Denver

#201

Post by schoen » Thu, May 13, 2021, 5:15 PM UTC

I remember seeing some Internet post a couple of decades ago where someone asserted that the goal of ATC was to prevent midair collisions and that U.S. ATC had met this goal perfectly, with no midair collisions between aircraft that were under the control of ATC at the time.

I think the claim was qualified in some way like "collision between civilian flights that were both flying an ATC-assigned clearance at the time". (So some kinds of flights and some kinds of airspace don't require ATC clearance, and if one of them were involved in a collision, it wouldn't be ATC's responsibility, in some sense.)

My question at the moment is: is this claim plausible if you qualify or restrict it enough? Do you have to tack on additional conditions?

Is there any useful sense in which this collision was a first for U.S. aviation history?

Re: Midair Collision over Denver

#202

Post by FabHK » Thu, May 13, 2021, 5:19 PM UTC

I wonder how many mid air collisions we would expect to see if see-and-avoid where entirely ineffectual, or pilots would not look outside ever except to land. I have the impression the accident numbers would not be much worse than they are.

In other words, my hypothesis is that the fact that there are few mid-airs is owed to ATC, technology (TCAS, TAS) and “big sky”, rather than vigilant pilots.

Re: Midair Collision over Denver

#203

Post by ericpauley » Thu, May 13, 2021, 5:35 PM UTC

FabHK wrote: post #202

I wonder how many mid air collisions we would expect to see if see-and-avoid where entirely ineffectual, or pilots would not look outside ever except to land. I have the impression the accident numbers would not be much worse than they are. In other words, my hypothesis is that the fact that there are few mid-airs is owed to ATC, technology (TCAS, TAS) and “big sky”, rather than vigilant pilots.

Agreed. It can be hard to spot traffic even if you know where the other plane is! With this in mind ADS-B/TIS-B seems like such an essential tool for GA pilots.

Re: Midair Collision over Denver

#204

Post by bananabreakfast » Thu, May 13, 2021, 5:36 PM UTC

jmpman wrote: post #135

JohnJamesRambo wrote: post #88

Earlier quoted context omitted.

Thank you, I was so confused. I was thinking the pilot a genius for bringing and activating a parachute. Now I see it was just great design. > As of 1 May 2021, CAPS had been activated 122 times, 101 of which saw successful parachute deployment. In those successful deployments, there were 207 survivors and 1 fatality. No fatalities had occurred when the parachute was deployed within the certified speed and altitude p…

21 of 122 failed? That’s a concerning statistic. I’d expect closer to 99% success, not 82%. How many fatalities when the parachute failed to deploy? 100%? If so, then you have almost a 1/5 chance of dying when you engage the parachute?

That is not a correct interpretation of that statistic.

The parachute has never "failed" in any engineering sense. The stat is taking into account all deployments, including those well outside of the deployment envelope, such as not enough altitude or too much velocity. No one can expect any parachute to deploy if you're too close to the ground.

Within the envelope of deployment, the statistic says it has a 100% success rate.

Re: Midair Collision over Denver

#205

Post by elliekelly » Thu, May 13, 2021, 5:38 PM UTC

lbriner wrote: post #191

elliekelly wrote: post #111

Earlier quoted context omitted.

I’ve probably mentioned this book on HN a hundred times but “Black Box Thinking” discusses the aviation culture of avoiding blame and making sure a problem isn’t repeated and how other industries (like medicine) would benefit hugely from a similar approach. It’s really interesting.

I'm not sure how scalable this is in modern penny-pinching times. In the old days, airlines had to prove they were safe to attract business and this involved accepting that certain practices were harmful and they were therefore improved. Once we got to the 1980s, we had so many airlines trying to survive that corners were cut, recommendations were not followed and various accidents were essentially negligent. Now tha…

I agree and it’s somewhat addressed in the book - if you find the premise at all interesting you should definitely read it, even if you’re skeptical of the practicality of implementing the philosophy (for lack of a better word) it’s interesting and the examples are compelling.

Some of the examples are whole-cloth cultural changes of entire industries (usually commercial flight actually, IIRC), but some are small, simple, changes that can be implemented by one or two people and still have a dramatic impact. One of the smaller-scale examples from the book that really stuck out was the attitude & approach of a surgeon in an operating room. When surgeons approach mistakes from the perspective of “okay, this happened, let’s focus on how we fix it” mistakes are reported to the surgeon quickly, the surgeon gets accurate information quickly, and can respond appropriately. Result: more mistakes are reported but the surgeon has fewer complications and better outcomes.

When surgeons approach mistakes by getting angry or assigning blame to the nurse who did X or the resident who did Y those surgeons have fewer (reported) mistakes but worse outcomes. Why? People don’t fess up because they fear the consequences. And when a mistake is identified, people don’t give accurate and complete information because their primary concern is KYA rather than fixing the problem at hand.

Re: Midair Collision over Denver

#206

Post by ddoolin » Thu, May 13, 2021, 5:39 PM UTC

sokoloff wrote: post #136

t0mas88 wrote: post #120

Earlier quoted context omitted.

That makes things a lot harder for the Cirrus pilot. Easy to get the lineup slightly wrong with for example some wind correction in from far away. Crazy that ATC had them do this at the same altitude as conflicting traffic with no underlying approach as a safety net. You can ask someone not to go through final, but that's very easy to miss judge from a couple of miles away.

Slightly harder? I'd agree with that. A lot harder? 20 hour student pilots make visual turns from base to final from 3 miles out every day. This is not Top Gun material.

If the sight picture is the usual one for the pilot, sure. I think if you throw a 20-hour pilot at an unfamiliar airport with a different pattern configuration than they're used to (right or left, direct to base, etc), your chances of overshooting can go up a lot. Throw in tight parallels and it's not great.

I train at an airport with parallels with a tight-enough runway separation gap to necessitate a 15-degree offset in both T/O & L on the GA runway. > 100-hour me overshot into the adjacent approach when being cleared direct to base for the "commercial runway" which I've probably only been given once before. Shameful, yes, and a learning experience, but I never overshoot on the adjacent (we also have different TPAs for the parallels, probably for this reason though).

Re: Midair Collision over Denver

#207

Post by mlac » Thu, May 13, 2021, 5:39 PM UTC

schoen wrote: post #201

I remember seeing some Internet post a couple of decades ago where someone asserted that the goal of ATC was to prevent midair collisions and that U.S. ATC had met this goal perfectly , with no midair collisions between aircraft that were under the control of ATC at the time. I think the claim was qualified in some way like "collision between civilian flights that were both flying an ATC-assigned clearance at the tim…

> "The Cirrus descended through 6400 feet about 3nm north of the threshold of runway 17R, but overshot the centerlines of both runways 17R and 17L"

It looks like the Cirrus wasn't flying to what the ATC cleared...

Re: Midair Collision over Denver

#208

Post by dillondoyle » Thu, May 13, 2021, 6:00 PM UTC

cmckn wrote: post #43

I've spent a decent amount of time at Centennial; it's one of the busiest general aviation airports in the country. There's a great restaurant on site that you can watch the runways from. After this incident, the restaurant is probably as close as I'd get to a Cirrus. :)

It's really close to the city too.

I'm sure the chances of a collision outside of the airport is absolutely basically zero, but these small planes fly really low over my house and the downtown area all the time. They get pretty low and close for touring over the big buildings for photos and stuff, see photos on reddit all the time..

Re: Midair Collision over Denver

#209

Post by ssully » Thu, May 13, 2021, 6:04 PM UTC

JohnJamesRambo wrote: post #88

nickcw wrote: post #7

Just in case anyone (like me) is thinking - wait did that aeroplane have a parachute? From: https://en.m.wikipedia.org/wiki/Cirrus_Airframe_Parachute_Sy... The Cirrus Airframe Parachute System (CAPS) is a whole-plane ballistic parachute recovery system designed specifically for Cirrus Aircraft's line of general aviation light aircraft including the SR20, SR22 and SF50. The design became the first of its kind to becom…

Thank you, I was so confused. I was thinking the pilot a genius for bringing and activating a parachute. Now I see it was just great design. > As of 1 May 2021, CAPS had been activated 122 times, 101 of which saw successful parachute deployment. In those successful deployments, there were 207 survivors and 1 fatality. No fatalities had occurred when the parachute was deployed within the certified speed and altitude p…

For those curious about seeing it in action: https://www.youtube.com/watch?v=gBCUQlF3MMU

Re: Midair Collision over Denver

#210

Post by labcomputer » Thu, May 13, 2021, 6:17 PM UTC

throwaway0a5e wrote: post #137

mdip wrote: post #62

Wow, that's incredible. Goes to show that people do walk away from plane crashes with some regularity. My father was a pilot[0]. He sold his plane about 15 years ago (to a group of owners, one of which was a priest, I'm sure there's a joke in there). A few of winters later, he was called out to Romeo Airport; the pilot flying the plane that was formerly his had crashed the aircraft a few miles short of the runway in…

> The weight is so critical that the 7-seat plane can realistically only seat 4-5 adults. I remember being shocked that they had to weigh the paint they applied when he had the plane re-painted. I used to work in general aviation. If my eyes could fly a loop in my skull they would have. Were the occupants required to use the bathroom before flying? That's how much weight you're potentially saving by weighing the pain…

Well... ok, but you usually still need to weigh and check the balance of the control surfaces after painting to ensure that they aren't going to flutter at less than Vmc (post-paint control surface balancing is often explicitly called out in the maintenance manual).

Painting a plane is one of those times that you often strip everything out anyway, so it's a convenient time to check the weight and balance against the logbook.