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JRBarrett
January 30, 2025, 13:20:00 GMT
permalink Post: 11817229

Quote:

Originally Posted by Someone Somewhere

I was talking about visual separation; I should have been clearer.

Might have helped the CRJ see the helicopter (except a military helicopter probably won't be illuminated anyway)

Military aircraft are required to have standard external lighting when operating in civil airspace. In the zoomed video clip of the collision, you can see the helicopter had a strobe light. But with the relative positions, it probably would have been difficult for the CRJ crew to have seen the Blackhawk - especially since they were probably looking forward to concentrate on the runway.

Subjects Blackhawk (H-60) CRJ Separation (ALL) Visual Separation

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JRBarrett
February 01, 2025, 14:12:00 GMT
permalink Post: 11819054

Quote:

Originally Posted by SASless

Some folks here need to read back through the thread before posting.

The helicopter crew is said to have had NVG's but at this point no information has been provided re their use of NVG's.

The height issue is not the primary issue as the intent of the procedures and ATC instructions was to separate the two aircraft.

Had that separation effort worked there would have been no conflict thus no collision.

It is the failure of the separation and the meeting over the river the two aircraft in the same bit of air that height mattered.

No where in the standard procedure was it intended to have helicopter traffic fly below landing aircraft on RWY 33.

Poll the Pilots here folks....ask them if they would routinely fly 100-200 feet below a crossing aircraft? What do you think the answer would be?

I thank 212 Man for his input reminding me why he was the Teacher's Pet. I depend upon his ability to get into the books to keep me straight.

Now a test question for him.....were you flying the incident airplane doing a Visual Approach to RWY33....would you have tuned up the IAP for that RWY as an additional reference for your approach?

SOP's usually instruct Crews to use ILS data when doing Visual Approaches to runways with that kind of IAP so would that kind of thinking apply in this incident? Would that have been of any benefit considering the existing weather and terrain? Or, would that have been a distraction?

This was not a "Circling Approach" but it was very similar.

The only instrument approach to runway 33 is an RNAV GPS - there is no ILS for that runway. From the final fix IDTEK pilots are to descent visually.

Subjects ATC Circle to Land (Deviate to RWY 33) Night Vision Goggles (NVG) Separation (ALL)

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JRBarrett
February 02, 2025, 03:43:00 GMT
permalink Post: 11819495

Quote:

Originally Posted by Lead Balloon

That's assuming perfect equipment accuracy. My understanding is that the tolerance of e.g. an IFR altimeter in the USA is 75'. If that's correct, one IF aircraft with a 'legal' altimeter indicating 325' could in fact be at 250' and another IFR aircraft with a 'legal' altimeter indicating 175' could in fact be at ... 250'. I'm hoping that the avionics in the aircraft involved in this terrible tragedy were more accurate than that, but I always exercise caution in taking numbers out of avionics and ATC systems as 'gospel truth' to the foot. The altitudes on RADAR displays don't increase and decrease in 1 foot increments; nor do the outputs of aircraft transponders. RADALT is different.

The maximum allowable altimeter error between sea level and 1000 feet is +/- 20 feet, and even a simple stand-alone barometric altimeter has to be able to meet that requirement. The RVSM-certified Air Data Computers on something like a CRJ are typically much more precise than that - more like +/- 5 feet at almost all altitudes. I would assume the air data system on a Blackhawk would be equally precise at low levels.

Subjects ATC Barometric Altimeter Blackhawk (H-60) CRJ IFR

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JRBarrett
February 02, 2025, 04:47:00 GMT
permalink Post: 11819512

Quote:

Originally Posted by Lead Balloon

Thanks JRB. Regulatory reference? I'm not saying you're wrong. But I can't find anything other than the 75'. (The acceptable 'split' between 2 on board altimeters is a different tolerance, I believe.)

Appendix \x91E\x92 of FAR 43, which contains the minimum standards that all altimeters must meet. It includes a table of allowable error at altitudes between sea level and 50,000 feet. Most air data computers on jet aircraft are far more precise than the minimum standards in FAR 43. RVSM certified altimetry systems must meet additional accuracy requirements set forth in Appendix \x91G\x92 of FAR 91 - but that only applies at altitudes between FL290 and FL410.

The Blackhawk air data system would not be RVSM certified as it could not fly high enough to need it, but the CRJ definitely would be. The CRJ has independent dual digital air data computers, and I assume the Blackhawk does as well.

The \x9375 foot\x94 requirement does not come from a specific FAR, but from the Airman\x92s Information Manual (AIM), which states that if the current barometric pressure is set on the ground, that the altimeter should read within 75 feet of the known field elevation at the aircraft\x92s location or the \x93altimeter accuracy should be suspect\x94.

In the US, the altimeters of all civil aircraft that fly under IFR must be tested for required accuracy every 24 months. I assume military aircraft have to meet the same requirement.

FAR 43 Appendix \x91E\x92 is the basic standard for accuracy, but in the case of something like the CRJ, the AMM (Aircraft Maintenance Manual) Chapter 34 will have additional tests to perform which have much more stringent accuracy requirements set forth than FAR 43.

Last edited by JRBarrett; 2nd February 2025 at 04:59 .

Subjects Blackhawk (H-60) CRJ IFR

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JRBarrett
February 03, 2025, 21:44:00 GMT
permalink Post: 11820928

Quote:

Originally Posted by MPN11

That is a question I posed way back. Does DCA Tower have a slaved radar display? Does a non-trained/qualified controller have the authority to use that data in extremis? Personally, as an ATCO, and presented with imminently co-altitude and virtually head-on conflicting traffic, I would have intervened. But then I was always an interventionist Tower controller!

My earlier questions remain unanswered \x85 does DCA Tower have a slaved radar display ?
And thus could Tower have used that data to direct PAT21 out of the way, regardless of qualification or licensing? Or did Tower have a Radar qualification anyway, but didn\x92t use it?

I can\x92t speak for DCA, but my local Class D airport (KELM) has had a radar repeater in the tower cab since the late 1980s, and all the local controllers use it. I would think DCA almost certainly has one. The radar repeater is not used to give vectors to aircraft, but as an aid to the controller\x92s situational awareness.

Subjects ATC ATCO DCA Radar Situational Awareness

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JRBarrett
March 30, 2025, 13:46:00 GMT
permalink Post: 11857344

Quote:

Originally Posted by sunnySA

Not sure that I'm following this focus on ADSB. Unless the PSA CRJ had ADSB-IN, then the absence of ADSB-OUT in the Army helicopter is irrelevant to the accident.

In recent investigations ATSB (Australia) has been pushing the merits of ADSB-IN. NTSB's (and ATSB's) remit is rather broad and can be used to push a particular agenda.

FAA (and CASA) can mandate ADSB-IN in all powered aircraft, and the US (and AU) Governments could easily fund the fitment from the Government coffers. Every billionaire in the Forbes Top 200 Richest People in America could easily afford to fund ADSB fitment. Would certainly improve their Philanthropy scores.

Be interesting to see whether PSA Airlines tick the ADSB-IN option with their next fleet order, or retrofit their fleet with ADSB-IN.

The Collins Proline 4 avionics system found on the CRJ has no provision for ADSB-IN, and knowing how the system works at a low level, I don\x92t think there is any way it could be added. It would probably require the addition of a dedicated display unit such as the Garmin GI-275, which is capable of displaying ADSB-IN when operating in MFD mode.

Adding the mandated ADSB-OUT capability to the Proline 4 was a simpler exercise as it mainly required upgrading the TDR-94 transponders and making use of already-available ARINC-429 data from the Air Data Computers, AHRS/IRS and GPS

Subjects ADSB (All) CRJ FAA

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JRBarrett January 30, 2025, 13:20:00 GMT permalink Post: 11817229	Quote: Originally Posted by Someone Somewhere I was talking about visual separation; I should have been clearer. Might have helped the CRJ see the helicopter (except a military helicopter probably won't be illuminated anyway) Military aircraft are required to have standard external lighting when operating in civil airspace. In the zoomed video clip of the collision, you can see the helicopter had a strobe light. But with the relative positions, it probably would have been difficult for the CRJ crew to have seen the Blackhawk - especially since they were probably looking forward to concentrate on the runway. Subjects Blackhawk (H-60) CRJ Separation (ALL) Visual Separation Links are to this post in the relevant subject page so that this post can be seen in context. 1 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
JRBarrett February 01, 2025, 14:12:00 GMT permalink Post: 11819054	Quote: Originally Posted by SASless Some folks here need to read back through the thread before posting. The helicopter crew is said to have had NVG's but at this point no information has been provided re their use of NVG's. The height issue is not the primary issue as the intent of the procedures and ATC instructions was to separate the two aircraft. Had that separation effort worked there would have been no conflict thus no collision. It is the failure of the separation and the meeting over the river the two aircraft in the same bit of air that height mattered. No where in the standard procedure was it intended to have helicopter traffic fly below landing aircraft on RWY 33. Poll the Pilots here folks....ask them if they would routinely fly 100-200 feet below a crossing aircraft? What do you think the answer would be? I thank 212 Man for his input reminding me why he was the Teacher's Pet. I depend upon his ability to get into the books to keep me straight. Now a test question for him.....were you flying the incident airplane doing a Visual Approach to RWY33....would you have tuned up the IAP for that RWY as an additional reference for your approach? SOP's usually instruct Crews to use ILS data when doing Visual Approaches to runways with that kind of IAP so would that kind of thinking apply in this incident? Would that have been of any benefit considering the existing weather and terrain? Or, would that have been a distraction? This was not a "Circling Approach" but it was very similar. The only instrument approach to runway 33 is an RNAV GPS - there is no ILS for that runway. From the final fix IDTEK pilots are to descent visually. Subjects ATC Circle to Land (Deviate to RWY 33) Night Vision Goggles (NVG) 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.
JRBarrett February 02, 2025, 03:43:00 GMT permalink Post: 11819495	Quote: Originally Posted by Lead Balloon That's assuming perfect equipment accuracy. My understanding is that the tolerance of e.g. an IFR altimeter in the USA is 75'. If that's correct, one IF aircraft with a 'legal' altimeter indicating 325' could in fact be at 250' and another IFR aircraft with a 'legal' altimeter indicating 175' could in fact be at ... 250'. I'm hoping that the avionics in the aircraft involved in this terrible tragedy were more accurate than that, but I always exercise caution in taking numbers out of avionics and ATC systems as 'gospel truth' to the foot. The altitudes on RADAR displays don't increase and decrease in 1 foot increments; nor do the outputs of aircraft transponders. RADALT is different. The maximum allowable altimeter error between sea level and 1000 feet is +/- 20 feet, and even a simple stand-alone barometric altimeter has to be able to meet that requirement. The RVSM-certified Air Data Computers on something like a CRJ are typically much more precise than that - more like +/- 5 feet at almost all altitudes. I would assume the air data system on a Blackhawk would be equally precise at low levels. Subjects ATC Barometric Altimeter Blackhawk (H-60) CRJ IFR 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.
JRBarrett February 02, 2025, 04:47:00 GMT permalink Post: 11819512	Quote: Originally Posted by Lead Balloon Thanks JRB. Regulatory reference? I'm not saying you're wrong. But I can't find anything other than the 75'. (The acceptable 'split' between 2 on board altimeters is a different tolerance, I believe.) Appendix \x91E\x92 of FAR 43, which contains the minimum standards that all altimeters must meet. It includes a table of allowable error at altitudes between sea level and 50,000 feet. Most air data computers on jet aircraft are far more precise than the minimum standards in FAR 43. RVSM certified altimetry systems must meet additional accuracy requirements set forth in Appendix \x91G\x92 of FAR 91 - but that only applies at altitudes between FL290 and FL410. The Blackhawk air data system would not be RVSM certified as it could not fly high enough to need it, but the CRJ definitely would be. The CRJ has independent dual digital air data computers, and I assume the Blackhawk does as well. The \x9375 foot\x94 requirement does not come from a specific FAR, but from the Airman\x92s Information Manual (AIM), which states that if the current barometric pressure is set on the ground, that the altimeter should read within 75 feet of the known field elevation at the aircraft\x92s location or the \x93altimeter accuracy should be suspect\x94. In the US, the altimeters of all civil aircraft that fly under IFR must be tested for required accuracy every 24 months. I assume military aircraft have to meet the same requirement. FAR 43 Appendix \x91E\x92 is the basic standard for accuracy, but in the case of something like the CRJ, the AMM (Aircraft Maintenance Manual) Chapter 34 will have additional tests to perform which have much more stringent accuracy requirements set forth than FAR 43. Last edited by JRBarrett; 2nd February 2025 at 04:59 . Subjects Blackhawk (H-60) CRJ IFR Links are to this post in the relevant subject page so that this post can be seen in context. 1 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
JRBarrett February 03, 2025, 21:44:00 GMT permalink Post: 11820928	Quote: Originally Posted by MPN11 That is a question I posed way back. Does DCA Tower have a slaved radar display? Does a non-trained/qualified controller have the authority to use that data in extremis? Personally, as an ATCO, and presented with imminently co-altitude and virtually head-on conflicting traffic, I would have intervened. But then I was always an interventionist Tower controller! My earlier questions remain unanswered \x85 does DCA Tower have a slaved radar display ? And thus could Tower have used that data to direct PAT21 out of the way, regardless of qualification or licensing? Or did Tower have a Radar qualification anyway, but didn\x92t use it? I can\x92t speak for DCA, but my local Class D airport (KELM) has had a radar repeater in the tower cab since the late 1980s, and all the local controllers use it. I would think DCA almost certainly has one. The radar repeater is not used to give vectors to aircraft, but as an aid to the controller\x92s situational awareness. Subjects ATC ATCO DCA Radar Situational Awareness 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.
JRBarrett March 30, 2025, 13:46:00 GMT permalink Post: 11857344	Quote: Originally Posted by sunnySA Not sure that I'm following this focus on ADSB. Unless the PSA CRJ had ADSB-IN, then the absence of ADSB-OUT in the Army helicopter is irrelevant to the accident. In recent investigations ATSB (Australia) has been pushing the merits of ADSB-IN. NTSB's (and ATSB's) remit is rather broad and can be used to push a particular agenda. FAA (and CASA) can mandate ADSB-IN in all powered aircraft, and the US (and AU) Governments could easily fund the fitment from the Government coffers. Every billionaire in the Forbes Top 200 Richest People in America could easily afford to fund ADSB fitment. Would certainly improve their Philanthropy scores. Be interesting to see whether PSA Airlines tick the ADSB-IN option with their next fleet order, or retrofit their fleet with ADSB-IN. The Collins Proline 4 avionics system found on the CRJ has no provision for ADSB-IN, and knowing how the system works at a low level, I don\x92t think there is any way it could be added. It would probably require the addition of a dedicated display unit such as the Garmin GI-275, which is capable of displaying ADSB-IN when operating in MFD mode. Adding the mandated ADSB-OUT capability to the Proline 4 was a simpler exercise as it mainly required upgrading the TDR-94 transponders and making use of already-available ARINC-429 data from the Air Data Computers, AHRS/IRS and GPS Subjects ADSB (All) CRJ FAA Links are to this post in the relevant subject page so that this post can be seen in context. 1 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.

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