Someone Somewhere Page: 2 of 2

Someone Somewhere
March 18, 2025, 00:23:00 GMT
permalink Post: 11849335

Quote:

Originally Posted by safetypee

Dr David Woods PhD

"\x85 to everyone in safety: look at the DCA midair collision given info in urgent action letter from NTSB. Widespread systems issues, total breakdown of proactive safety; repeats history from Herald of Free Enterprise to Challenger, Columbia etc. see my chapters on (Columbia testimony to Congress, RE book 2006 & 2005 Organization at the Limit book). Highlights real issues of multiple sometimes conflicting goals over multiple jurisdictions/perspectives, signals discounted in the face of ongoing production pressures, etc. Also note the reactions to failure. All well understood in 3 books capturing the new look work of the 80's -- 1990 (Reason) / 1994 (Woods etal) /1997 (Reason)."
Yet here we are all over again. All over again.

https://www.linkedin.com/posts/davidwoods3_to-everyone-in-safety-look-at-the-dca-midair-activity-7307401640821563392-I5Ez/?utm_source=share&utm_medium=member_ios&rcm=ACoAAAizWBQBjDn2 SfSP5os0fcB7hU2U_S8Iv3k

..

Frankly, a lot of lessons shown in rail accident reports from the 1800s still haven't fully been learnt outside the rail industry. Aviation is unforgiving of mechanical failures but rail is equally unforgiving of procedural failures.

https://en.wikipedia.org/wiki/Clayton_Tunnel_rail_crash

Quote:

The catastrophe publicised the problem of trains travelling too close together, with signalmen having to appraise the situation too quickly for safety's sake. A simple communication mistake between the two signal boxes caused havoc that Sunday, but the telegraph was also blamed for the tragedy because it did not register without continual pressure on the switch. The signal, too, was also at fault for not returning to "danger" immediately after the train had passed. The accident encouraged the use of the block system (rather than the time interval system ) for the remainder of the railway system.

One other aspect of this accident was that Signalman Killick was working a continuous 24-hour shift that day, rather than the regulation 18 hours to gain a complete day off duty. In his report on the accident Captain Tyler stated that "it was disgraceful that a man in so responsible a position as Signalman Killick should be compelled to work for twenty-four hours at a stretch in order to earn one day of rest a week."

Subjects DCA NTSB

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Someone Somewhere
March 23, 2025, 10:35:00 GMT
permalink Post: 11852551

See the below post 1180 and some earlier ones:

Quote:

Originally Posted by airplanecrazy

Thanks for the suggestion. I am not a GPS expert either, but it is easy to defend error bars of at least 10' horizontal and 15' vertical (based upon both ADS-B quantization and inherent GPS resolution). I have updated the chart below with those error bars below, and I will update it again if an expert gives me better values. Given your feedback, I would change my statement to say that all depicted values near 200' are consistent with the aircraft being at or below 200', and readers should not assume those flights exceeded the limit.

As for your question on the glideslope, I did NOT properly account for the EGM96 correction. The new chart moves the glideslope up 5' to meet the height of the PAPI as measured in Google Earth (18'), which uses EGM96. Is that reasonable? I should also add a couple of feet to account for the height of the PAPI lights themselves. Does anyone know how much I should add? Thanks for the catch.

Helicopters crossing RWY 33 approach via Route 4 for January (updated)

The horizontal boundaries of the route are not precisely defined. Even then, it's not a very steep slope and the horizontal position does not make a huge difference.

75' is plainly inadequate vertical clearance between two aircraft and doubling/tripling that would still be unacceptably close. Separation was surely expected to be achieved horizontally but the enforcement/implementation was lacking.

Subjects ADSB (All) Route 4 Separation (ALL)

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Someone Somewhere
March 26, 2025, 01:47:00 GMT
permalink Post: 11854307

Quote:

Originally Posted by galaxy flyer

Quote:

Originally Posted by layman54

To give an example. I live in the northeast. Some of roads are old and not built to modern standards. In particular sometimes the overpasses have limited clearance. This is unsafe. You could even describe such overpasses as accidents waiting to happen. Nevertheless if you are driving a truck and you don't plan your route properly, you ignore the signs saying no trucks on the expressway, you ignore the signs saying low clearance ahead you disregard the fact that you are about to try to drive under an overpass which is lower than your truck is high and you plow into it at sixty miles an hour then you were negligent. And you don't escape legal liability because the road was badly designed.

Slow down, cowboy. Drive across the Cross Bronx Expressway at any time of day in your 13\x926\x94 truck. Damned near every underpass on those few miles and there\x92s a lot of them marked something between 12\x926\x94 and 13\x922\x94. I never noticed it until a trucker mentioned it.

There's two counterpoints there, though. Road safety has a much lower safety target than aviation safety (more a comment on a car-centric world than anything else), and the chance of that accident being fatal (especially fatal to an uninvolved party) are much much lower. I'd also hazard a guess that a number of those bridges have warning systems that trigger some kind of stop signal if approached by an overheight vehicle.

Subjects Accountability/Liability

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Someone Somewhere
March 26, 2025, 02:26:00 GMT
permalink Post: 11854317

Quote:

Originally Posted by galaxy flyer

Surely you jest on overheight warning systems—I’ve never heard of or seen. You around for videos of truck-overpass collisions. As a permit load trucker told me, “you can swerve but you can’t duck”. I looked at the CBE traffic and couldn’t count the number of 13’6” trucks going under12’8” overpasses.

For the extreme option , here's a projection onto a water curtain:

The classic 11'8" bridge of youtube fame has overheight lights. The bridge has since been slightly raised and the warning systems improved but still gets people driving straight through them.

Even the London Underground has frangible fittings to detect taller surface stock trains incorrectly approaching a deep-level tube tunnel, throwing signals to danger and thus raising trainstops, which if passed apply the emergency brakes. The latter is important, because SPADs (Signal Passed At Danger) are still not uncommon.

They're not everywhere. It's a risk analysis based mainly on the inconvenience and cost of the cleanup and closure for the bridge/tunnel, and how many overheight vehicles are actually impacting the obstacle. They also don't work especially well because people assume the overheight warning couldn't possibly apply to them .

There's probably some degree of tolerance involved; e.g. bridge marked at 4.4m, sensors at 4.6m, bridge is actually 4.8m. I'm not sure what the actual standards are.

Subjects: None

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Someone Somewhere
March 29, 2025, 10:29:00 GMT
permalink Post: 11856539

The 'elephant in the room' to me is that there seems to be no actual definition of 'perfectly safe visual separation'. One pilot's reckless disregard might be another's overly cautious .

Subjects Separation (ALL) Visual Separation

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Someone Somewhere March 18, 2025, 00:23:00 GMT permalink Post: 11849335	Quote: Originally Posted by safetypee Dr David Woods PhD "\x85 to everyone in safety: look at the DCA midair collision given info in urgent action letter from NTSB. Widespread systems issues, total breakdown of proactive safety; repeats history from Herald of Free Enterprise to Challenger, Columbia etc. see my chapters on (Columbia testimony to Congress, RE book 2006 & 2005 Organization at the Limit book). Highlights real issues of multiple sometimes conflicting goals over multiple jurisdictions/perspectives, signals discounted in the face of ongoing production pressures, etc. Also note the reactions to failure. All well understood in 3 books capturing the new look work of the 80's -- 1990 (Reason) / 1994 (Woods etal) /1997 (Reason)." Yet here we are all over again. All over again. https://www.linkedin.com/posts/davidwoods3_to-everyone-in-safety-look-at-the-dca-midair-activity-7307401640821563392-I5Ez/?utm_source=share&utm_medium=member_ios&rcm=ACoAAAizWBQBjDn2 SfSP5os0fcB7hU2U_S8Iv3k .. Frankly, a lot of lessons shown in rail accident reports from the 1800s still haven't fully been learnt outside the rail industry. Aviation is unforgiving of mechanical failures but rail is equally unforgiving of procedural failures. https://en.wikipedia.org/wiki/Clayton_Tunnel_rail_crash Quote: The catastrophe publicised the problem of trains travelling too close together, with signalmen having to appraise the situation too quickly for safety's sake. A simple communication mistake between the two signal boxes caused havoc that Sunday, but the telegraph was also blamed for the tragedy because it did not register without continual pressure on the switch. The signal, too, was also at fault for not returning to "danger" immediately after the train had passed. The accident encouraged the use of the block system (rather than the time interval system ) for the remainder of the railway system. One other aspect of this accident was that Signalman Killick was working a continuous 24-hour shift that day, rather than the regulation 18 hours to gain a complete day off duty. In his report on the accident Captain Tyler stated that "it was disgraceful that a man in so responsible a position as Signalman Killick should be compelled to work for twenty-four hours at a stretch in order to earn one day of rest a week." Subjects DCA NTSB Links are to this post in the relevant subject page so that this post can be seen in context. 2 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
Someone Somewhere March 23, 2025, 10:35:00 GMT permalink Post: 11852551	See the below post 1180 and some earlier ones: Quote: Originally Posted by airplanecrazy Thanks for the suggestion. I am not a GPS expert either, but it is easy to defend error bars of at least 10' horizontal and 15' vertical (based upon both ADS-B quantization and inherent GPS resolution). I have updated the chart below with those error bars below, and I will update it again if an expert gives me better values. Given your feedback, I would change my statement to say that all depicted values near 200' are consistent with the aircraft being at or below 200', and readers should not assume those flights exceeded the limit. As for your question on the glideslope, I did NOT properly account for the EGM96 correction. The new chart moves the glideslope up 5' to meet the height of the PAPI as measured in Google Earth (18'), which uses EGM96. Is that reasonable? I should also add a couple of feet to account for the height of the PAPI lights themselves. Does anyone know how much I should add? Thanks for the catch. Helicopters crossing RWY 33 approach via Route 4 for January (updated) The horizontal boundaries of the route are not precisely defined. Even then, it's not a very steep slope and the horizontal position does not make a huge difference. 75' is plainly inadequate vertical clearance between two aircraft and doubling/tripling that would still be unacceptably close. Separation was surely expected to be achieved horizontally but the enforcement/implementation was lacking. Subjects ADSB (All) Route 4 Separation (ALL) Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
Someone Somewhere March 26, 2025, 01:47:00 GMT permalink Post: 11854307	Quote: Originally Posted by galaxy flyer Quote: Originally Posted by layman54 To give an example. I live in the northeast. Some of roads are old and not built to modern standards. In particular sometimes the overpasses have limited clearance. This is unsafe. You could even describe such overpasses as accidents waiting to happen. Nevertheless if you are driving a truck and you don't plan your route properly, you ignore the signs saying no trucks on the expressway, you ignore the signs saying low clearance ahead you disregard the fact that you are about to try to drive under an overpass which is lower than your truck is high and you plow into it at sixty miles an hour then you were negligent. And you don't escape legal liability because the road was badly designed. Slow down, cowboy. Drive across the Cross Bronx Expressway at any time of day in your 13\x926\x94 truck. Damned near every underpass on those few miles and there\x92s a lot of them marked something between 12\x926\x94 and 13\x922\x94. I never noticed it until a trucker mentioned it. There's two counterpoints there, though. Road safety has a much lower safety target than aviation safety (more a comment on a car-centric world than anything else), and the chance of that accident being fatal (especially fatal to an uninvolved party) are much much lower. I'd also hazard a guess that a number of those bridges have warning systems that trigger some kind of stop signal if approached by an overheight vehicle. Subjects Accountability/Liability Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
Someone Somewhere March 26, 2025, 02:26:00 GMT permalink Post: 11854317	Quote: Originally Posted by galaxy flyer Surely you jest on overheight warning systems—I’ve never heard of or seen. You around for videos of truck-overpass collisions. As a permit load trucker told me, “you can swerve but you can’t duck”. I looked at the CBE traffic and couldn’t count the number of 13’6” trucks going under12’8” overpasses. For the extreme option , here's a projection onto a water curtain: The classic 11'8" bridge of youtube fame has overheight lights. The bridge has since been slightly raised and the warning systems improved but still gets people driving straight through them. Even the London Underground has frangible fittings to detect taller surface stock trains incorrectly approaching a deep-level tube tunnel, throwing signals to danger and thus raising trainstops, which if passed apply the emergency brakes. The latter is important, because SPADs (Signal Passed At Danger) are still not uncommon. They're not everywhere. It's a risk analysis based mainly on the inconvenience and cost of the cleanup and closure for the bridge/tunnel, and how many overheight vehicles are actually impacting the obstacle. They also don't work especially well because people assume the overheight warning couldn't possibly apply to them . There's probably some degree of tolerance involved; e.g. bridge marked at 4.4m, sensors at 4.6m, bridge is actually 4.8m. I'm not sure what the actual standards are. Subjects: None No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
Someone Somewhere March 29, 2025, 10:29:00 GMT permalink Post: 11856539	The 'elephant in the room' to me is that there seems to be no actual definition of 'perfectly safe visual separation'. One pilot's reckless disregard might be another's overly cautious . Subjects Separation (ALL) Visual Separation Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.

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