Monday, February 03, 2025

Data from Air Accident Show Conflicting Altitude Readings

Associate Press writes about the conflicting data readings from the helicopter-airline collision which had no survivors.

Posted by lamplighter at 06:31 PM | 21 COMMENTS | permalink

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These are the last 10 deadly airline crashes to occur in the US, according to data from the US National Transportation Board and the Flight Safety Foundation's Aviation Safety Network reut.rs/3Ek9gvW

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-- Reuters (@reuters.com) January 30, 2025 at 6:56 AM

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More from the article...

... Investigators also said that about a second before impact, the jet's flight recorder showed a change in its pitch. But they did not say whether that change in angle meant that pilots were trying to perform an evasive maneuver to avoid the crash.

Data from the jet's flight recorder showed its altitude as 325 feet (99 meters), plus or minus 25 feet (7.6 meters), when the crash happened Wednesday night, National Transportation Safety Board officials told reporters. Data in the control tower, though, showed the Black Hawk helicopter at 200 feet (61 meters) at the time.

The roughly 100-foot (30-meter) discrepancy has yet to be explained.

Investigators hope to reconcile the altitude differences with data from the helicopter's black box, which is taking more time to retrieve because it became waterlogged after it plunged into the Potomac River. They also said they plan to refine the tower data, which can be less reliable. ...



#1 | Posted by LampLighter at 2025-02-02 01:43 PM

They also said they plan to refine the tower data, which can be less reliable. ...

I would assume the flight data from the aircraft would be more accurate than radar info from the tower, so I'd guess the collision was at ~325 feet.

Logic dictates that since the aircraft collided, the helicopter was also at ~325 feet.

#2 | Posted by REDIAL at 2025-02-02 01:49 PM

@#2

I do not disagree at this point.

But until the more detailed data arrives, I have another question ...

Did the tower data show the aircraft was also at 200 feet, i.e., at the same altitude the tower thought of the helicopter?

#3 | Posted by LampLighter at 2025-02-02 02:01 PM

Did the tower data show the aircraft was also at 200 feet, i.e., at the same altitude the tower thought of the helicopter?

I saw radar plot images showing the CRJ at 400 feet and the UH-60 at 200 feet and then 2 seconds later showed them both at 300 feet. Tower radar resolution runs in 50 foot increments from what I have read.

#4 | Posted by REDIAL at 2025-02-02 02:08 PM

@#4 ... I saw radar plot images showing the CRJ at 400 feet and the UH-60 at 200 feet and then 2 seconds later showed them both at 300 feet. ...

I have read reports of a last-second maneuver by the aircraft.

What you describe might mean that the aircraft dropped down to the altitude of a rising the helicopter?

It usually takes a while for the black box data to be analyzed and a timeline made.



#5 | Posted by LampLighter at 2025-02-02 02:14 PM


They also said they plan to refine the tower data, which can be less reliable. ...

Just means use the raw data, not the data that DialAgain is talking about below.

Its clutter to worry about "exact" reporting in ft 23,903ft? Does it really matter just say 24.

200 would be 002

I look at these displays using foreflight, its simple.


I would assume the flight data from the aircraft would be more accurate than radar info from the tower, so I'd guess the collision was at ~325 feet.

Same data source. See below.


I saw radar plot images showing the CRJ at 400 feet and the UH-60 at 200 feet and then 2 seconds later showed them both at 300 feet. Tower radar resolution runs in 50 foot increments from what I have read.
#4 | POSTED BY REDIAL

Did you see the video of the incident? does that correspond to the radar plots? Does it look like that is what happened?

Also the "radar" plots might not be from "radar" but the transponder-c/s, with altitude reporting (req to get checked every 2yrs), via barometric pressure.

50ft isn't the issue, its rounding because the display gets cluttered with unimportant information.

If you saw the same "radar" video, you saw a CA detected, don't worry about being exact, just being close sets off alarms.

#6 | Posted by oneironaut at 2025-02-02 02:27 PM

What you describe might mean that the aircraft dropped down to the altitude of a rising the helicopter?

The CRJ was landing, so it was certainly losing altitude.

#7 | Posted by REDIAL at 2025-02-02 02:57 PM

@#7 ... The CRJ was landing, so it was certainly losing altitude. ...

Yup.

But I wonder if there was a sudden decrease in altitude that is not typical of the normal lowering of altitude during a landing?

#8 | Posted by LampLighter at 2025-02-02 03:11 PM

But I wonder if there was a sudden decrease in altitude that is not typical of the normal lowering of altitude during a landing?

I doubt it. Just instrument telemetry update lag is my thought.

#9 | Posted by REDIAL at 2025-02-02 03:27 PM

@#9

I look forward to the detailed analyses of the black boxes.

Until then, too many questions, not enough answers.

#10 | Posted by LampLighter at 2025-02-02 03:38 PM

I look forward to the detailed analyses of the black boxes.

Read the helo CVR was waterlogged when they found it. NTSB preliminary report in 30 days.

#11 | Posted by REDIAL at 2025-02-02 03:52 PM

@#11 ... Read the helo CVR was waterlogged when they found it. ...

Supposedly, they are designed for such an outcome. Idoes, however, take loger to analyze the data should that occur, as you note.


Flight recorder - Specifications
en.wikipedia.org

... The design of today's FDR is governed by the internationally recognized standards and recommended practices relating to flight recorders which are contained in ICAO Annex 6 which makes reference to industry crashworthiness and fire protection specifications such as those to be found in the European Organisation for Civil Aviation Equipment[45] documents EUROCAE ED55, ED56 Fiken A and ED112 (Minimum Operational Performance Specification for Crash Protected Airborne Recorder Systems).

In the United States, the Federal Aviation Administration (FAA) regulates all aspects of US aviation, and cites design requirements in their Technical Standard Order,[46] based on the EUROCAE documents (as do the aviation authorities of many other countries).

Currently, EUROCAE specifies that a recorder must be able to withstand an acceleration of 3400 g (33 km/s2) for 6.5 milliseconds. This is roughly equivalent to an impact velocity of 270 knots (310 mph; 500 km/h) and a deceleration or crushing distance of 45 cm (18 in).[47] Additionally, there are requirements for penetration resistance, static crush, high and low temperature fires, deep sea pressure, sea water immersion, and fluid immersion.

EUROCAE ED-112 (Minimum Operational Performance Specification for Crash Protected Airborne Recorder Systems) defines the minimum specification to be met for all aircraft requiring flight recorders for recording of flight data, cockpit audio, images and CNS / ATM digital messages and used for investigations of accidents or incidents.[48] When issued in March 2003, ED-112 superseded previous ED-55 and ED-56A that were separate specifications for FDR and CVR. FAA TSOs for FDR and CVR reference ED-112 for characteristics common to both types.

In order to facilitate recovery of the recorder from an aircraft accident site, they are required to be coloured bright yellow or orange with reflective surfaces. All are lettered "Flight recorder do not open" on one side in English and "Enregistreur de vol ne pas ouvrir" in French on the other side. To assist recovery from submerged sites they must be equipped with an underwater locator beacon which is automatically activated in the event of an accident. ...




Lots of detail in that article.


#12 | Posted by lamplighter at 2025-02-02 04:38 PM

I look forward to the detailed analyses of the black boxes.
- gaslighter

This is the engineering falesy.

In midair collisions, the data doesnt mean much. The voice recordings in the cockpit of the Helo, may or may not help.

There's a warren buffet axiom that is important in these cases.

Don't overweigh that which can be counted, and under weigh that which cannot.

The details are great but that's not why the mid air happened. It happened because of many factors, all human. And not all of those humans were active participants in the accident. Some of the blame is on whoever thought about putting a Helo route right through an approach path.

#13 | Posted by oneironaut at 2025-02-02 04:55 PM

#13 - I'm so glad people like you aren't at the NTSB.

#14 | Posted by YAV at 2025-02-02 05:43 PM

Supposedly, they are designed for such an outcome.

At least it wasn't salt water and didn't take a month to find it.

#15 | Posted by REDIAL at 2025-02-02 05:59 PM

@#15

Yeah.

The data on current black boxes (even though they are yellow or orange for visibility) seems to be stored on memory chips, not a disk drive.

Those memory chips may need to be removed from the water-corrupted environment of the black-box, and placed into an environment that allows them to be read.

That may be what takes the additional time in occurrences such as this one.



#16 | Posted by LampLighter at 2025-02-02 07:49 PM

and placed into an environment that allows them to be read.

I've seen discussions of de-ionised water baths in that regard.

#17 | Posted by REDIAL at 2025-02-02 07:53 PM

More important than any data from the accident.

The agency's database of those reports contains 30 records of NMAC reports at Reagan National since 1987. Of those, at least 10 involved military aircraft, and at least seven included military helicopters
www.npr.org

Nothing changed.

#18 | Posted by oneironaut at 2025-02-03 06:47 PM

#13 - I'm so glad people like you aren't at the NTSB.
#14 | Posted by YAV

Well you're a liar, so I'll take that under consideration.

I read accident reports for a hobby, makes me a better pilot.

Being safe and understanding accidents isn't difficult.

But it's never just one thing, typically it's a chain of events that create the event.

Relying upon on piece of data to draw a conclusion is what poor thinkers like yourself, dial again, and gaslighter do.

#19 | Posted by oneironaut at 2025-02-03 06:51 PM

I'm just glad that 1Nut has at least one hobby that doesn't involve boa feathers and leather straps!

#20 | Posted by Corky at 2025-02-03 07:09 PM

Mr. 17 plonks thinks yav is a liar. No, yav owns you.

#21 | Posted by Alexandrite at 2025-02-03 07:48 PM

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