January 31, 2025, 20:45:00 GMT
permalink Post: 11818520
I concur with this analysis
While the LC did not do anything unacceptable per se, the second affirmation of the CRJ being in sight would have been due to his concern about the proximity of the approaching aircraft. On this basis and with some benefit of hindsight, if he had been a bit more informative about the location and distance of the heli, this could have been a point of avoidance. Maybe there were some human factor priors were the heli pilots do not like what they deem as overly verbose comms or reassurance/verification calls, who knows.
Secondly, there appears to be an instrumentation issue, pilot error or both in one or both aircraft i.e. 1. no warning or awareness of warnings on a clearly impending incident - I only used TIS when I was flight training in the US some years ago, so again, some speculation. For CRJ, could be they had become accustomed to flying a few feet above helicopters there that they ignored such warnings 2. altitude deviation - could be mechanical, airmanship, wrong QNH etc.
Thirdly, the margins for error in the operating environment as many have commented appear too low, though in general there are low margins anyway when you are close to the ground.
If they [heli crew] were supposed to be following behind the CRJ, why were they getting that close to rwy 33 extended centreline or were they planning to turn once crossed? Was the CRJ centred laterally or did it perhaps slightly overshoot to the right?
I think it's more likely that the heli crew mistook the landing plane for #1 for rwy 01 rather than one taking off in my opinion, which leads me to think they may also have misidentified rwy 33 or the alignment to it at least. The latter may be an easy mistake at night. I would expect that part of the heli crew would have been very familiar with the territory, which makes it even more puzzling. The circling to land also adds a degree of ambiguity as to their understanding of the initial position notification or their expectation of where the landing a/c should be.
Anyway, we'll see when the prelim report comes out. I certainly hope there was a functioning CVR in the chopper.
While the LC did not do anything unacceptable per se, the second affirmation of the CRJ being in sight would have been due to his concern about the proximity of the approaching aircraft. On this basis and with some benefit of hindsight, if he had been a bit more informative about the location and distance of the heli, this could have been a point of avoidance. Maybe there were some human factor priors were the heli pilots do not like what they deem as overly verbose comms or reassurance/verification calls, who knows.
Secondly, there appears to be an instrumentation issue, pilot error or both in one or both aircraft i.e. 1. no warning or awareness of warnings on a clearly impending incident - I only used TIS when I was flight training in the US some years ago, so again, some speculation. For CRJ, could be they had become accustomed to flying a few feet above helicopters there that they ignored such warnings 2. altitude deviation - could be mechanical, airmanship, wrong QNH etc.
Thirdly, the margins for error in the operating environment as many have commented appear too low, though in general there are low margins anyway when you are close to the ground.
If they [heli crew] were supposed to be following behind the CRJ, why were they getting that close to rwy 33 extended centreline or were they planning to turn once crossed? Was the CRJ centred laterally or did it perhaps slightly overshoot to the right?
I think it's more likely that the heli crew mistook the landing plane for #1 for rwy 01 rather than one taking off in my opinion, which leads me to think they may also have misidentified rwy 33 or the alignment to it at least. The latter may be an easy mistake at night. I would expect that part of the heli crew would have been very familiar with the territory, which makes it even more puzzling. The circling to land also adds a degree of ambiguity as to their understanding of the initial position notification or their expectation of where the landing a/c should be.
Anyway, we'll see when the prelim report comes out. I certainly hope there was a functioning CVR in the chopper.
Last edited by my_call; 31st January 2025 at 22:37 .
Subjects
CRJ
QNH
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February 02, 2025, 16:17:00 GMT
permalink Post: 11819892
I assume that the RJ and the helo both definitely had the same pressure setting ( airfield QNH ) set on their altimeters.
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QNH
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February 02, 2025, 17:44:00 GMT
permalink Post: 11819956
Baesd on my experience, the helo crew would most likely have been operating on radalt with QNH on a baro alt as a secondary. However, when we were doing coupled low-level flight overwater, we (RAF SAR) used to set the baralt to match the radalt at 200 ft before descending.
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QNH
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February 03, 2025, 12:18:00 GMT
permalink Post: 11820480
QNH
Do not have the time to read back over 700 posts, apologies if some one has already picked up on this, but as a 30 yr Loadie and having spent thousands of hours on cockpit jump seats
keeping crews awake, reprograming iNS' s spent a lot of time telling crews of various nationalities they had read back the wrong QNH.
Did one or both crews have it wrong as the reason between the difference between the 2 flight recorders. Apologies again if already discussed.
keeping crews awake, reprograming iNS' s spent a lot of time telling crews of various nationalities they had read back the wrong QNH.
Did one or both crews have it wrong as the reason between the difference between the 2 flight recorders. Apologies again if already discussed.
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QNH
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February 15, 2025, 00:52:00 GMT
permalink Post: 11828325
Barometric altitude is the only reading that all participants can share. Trying to avoid terrain? Radalt makes sense. Trying to comply with a corridor, barometric altitude. If there is a problem that the radalt is way too low for the barometric, that should be a call to the ATC to find out what the reading is at the airport.
Subjects
ATC
QNH
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February 17, 2025, 09:45:00 GMT
permalink Post: 11829754
Facts of life: at one time or another pilots will set incorrect QNH values, altimeters will fail, flights will end up above or below a glideslope, lateral boundaries will be breached, pilots will fail checkrides, radio transmissions will be blocked, visual illusions will occur, air traffic controllers will get distracted. So any procedure that depends on all those things never happening is flawed. We are not living in some utopic la-la-land.
So I wouldn\x92t call the altimeter discussion a distraction per se - not yet, anyway. It\x92s just one tiny fact in a complex picture, but still an important fact nevertheless. It is a concrete example of one (or more) of those, by itself insignificant, real-life deviations from perfection occurring. I expect (hope) that the NTSB will use this issue just to illustrate the point that relevant traffic procedures at KDCA were largely based on wishful thinking.
So I wouldn\x92t call the altimeter discussion a distraction per se - not yet, anyway. It\x92s just one tiny fact in a complex picture, but still an important fact nevertheless. It is a concrete example of one (or more) of those, by itself insignificant, real-life deviations from perfection occurring. I expect (hope) that the NTSB will use this issue just to illustrate the point that relevant traffic procedures at KDCA were largely based on wishful thinking.
Subjects
KDCA
NTSB
QNH
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February 17, 2025, 15:15:00 GMT
permalink Post: 11829963
Just some easily verifiable number crunching:
For a landing aircraft on Rwy33, and assuming:
(1) correct QNH dialed in
(2) perfect centerline following
(3) perfect 3deg PAPI following
baro altitude would be 278 ft exactly above the east bank. And 200 baro altitude would come appr. 1.175 ft from the east bank and over the water.
Very hard to believe that aircrafts were routinely allowed to cross simultaneously this crossing. Statistically, the accident would have happened long ago, or at, the least, have reports filed (even from passengers) and brown underwear.
And btw, even top VIP seems that are considered much more expendable than we originally thought.
For a landing aircraft on Rwy33, and assuming:
(1) correct QNH dialed in
(2) perfect centerline following
(3) perfect 3deg PAPI following
baro altitude would be 278 ft exactly above the east bank. And 200 baro altitude would come appr. 1.175 ft from the east bank and over the water.
Very hard to believe that aircrafts were routinely allowed to cross simultaneously this crossing. Statistically, the accident would have happened long ago, or at, the least, have reports filed (even from passengers) and brown underwear.
And btw, even top VIP seems that are considered much more expendable than we originally thought.
Subjects
QNH
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February 17, 2025, 20:56:00 GMT
permalink Post: 11830154
Just some easily verifiable number crunching:
For a landing aircraft on Rwy33, and assuming:
(1) correct QNH dialed in
(2) perfect centerline following
(3) perfect 3deg PAPI following
baro altitude would be 278 ft exactly above the east bank. And 200 baro altitude would come appr. 1.175 ft from the east bank and over the water.
Very hard to believe that aircrafts were routinely allowed to cross simultaneously this crossing. Statistically, the accident would have happened long ago, or at, the least, have reports filed (even from passengers) and brown underwear.
And btw, even top VIP seems that are considered much more expendable than we originally thought.
For a landing aircraft on Rwy33, and assuming:
(1) correct QNH dialed in
(2) perfect centerline following
(3) perfect 3deg PAPI following
baro altitude would be 278 ft exactly above the east bank. And 200 baro altitude would come appr. 1.175 ft from the east bank and over the water.
Very hard to believe that aircrafts were routinely allowed to cross simultaneously this crossing. Statistically, the accident would have happened long ago, or at, the least, have reports filed (even from passengers) and brown underwear.
And btw, even top VIP seems that are considered much more expendable than we originally thought.
Think of it like a road with a traffic light (ATC) but you can merge on red if you can see it\x92s clear (helicopter). No rotary pilot I know would knowingly pass that close under/behind a jet transport as the wake could literally be the end of you at 200\x92AGL.
Subjects
ATC
QNH
Radar
Separation (ALL)
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February 18, 2025, 08:00:00 GMT
permalink Post: 11830516
Playing Devil's Advocate for a moment, if the heliroutes are published for the common sense use of participants, not for the protection of air transport, and we further accept that it is not within the purview of ATC to question the discretion of willing users, I'm afraid we can only fall back on this accident being the sole responsibility of the helicopter. Which I guess is is another way of re-stating your last post.
I wouldn't put it past the FAA to pull a stunt like that, read Mary Schiavo's (ex IG of the Dept. of Transportation) book if you want to know how wily they can be. And Jennifer gave them the perfect lay up in the last briefing.
I wouldn't put it past the FAA to pull a stunt like that, read Mary Schiavo's (ex IG of the Dept. of Transportation) book if you want to know how wily they can be. And Jennifer gave them the perfect lay up in the last briefing.
It's way to easy to blame the pilots, over the years there have been incidents due to incorrect QNH settings, were both pilots and ATC have failed to catch the error, in a busy airspace with overworked ATC, late change of runway for airlines, and military helicopters using Night Vision Goggles, altimeter equipment failure/error.
Even the Max 200 ft altitude under the approach to a major US airport is an accident waiting to happen, and whoever approved this to be used during normal operations should be investigated. The CRJ was at around 325 ft on a visual/circling approach when it crashed, does anyone really think it's great airmanship to have a Black Hawk helicopter at 200 ft passing under you?
That's what made the Swiss Cheese model line up perfectly, a planned approved separation of 125 ft was the "best case" scenario.
Subjects
ATC
Accident Waiting to Happen
Blackhawk (H-60)
CRJ
FAA
QNH
Separation (ALL)
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February 19, 2025, 23:16:00 GMT
permalink Post: 11831829
Out of curiosity, I was wondering how “out of the ordinary” the flight path was for PA25 compared to other flights along Route 4. I found 65 such flights in January (there are probably some I missed) and I plotted where they crossed the runway approach. Note that the altitude is binned in 25' chunks, so you should assume that all altitudes just above 200' were actually at 200'. For any aircraft above 200' I DID NOT try to determine if they received clearance from ATC (which is permitted), and you SHOULD NOT assume that they didn't. I also threw in a rough breakout between daylight and night for each crossing. For the two PAT flights well offshore, I did not investigate any special ATC clearances they had. I apologize in advance for any errors as it is a bit tricky to plot and measure these distances.
Added note: The chart shows only crossings collected with ADS-B. I threw out all MLAT collected crossing because of inherent inaccuracy.
Helicopters crossing RWY 33 approach via Route 4 for January
Added note: The chart shows only crossings collected with ADS-B. I threw out all MLAT collected crossing because of inherent inaccuracy.
Helicopters crossing RWY 33 approach via Route 4 for January
Interesting to note that, had PAT25 been at 200 ft and the CRJ just slightly below nominal glideslope, they would have collided too.
And that, had the CRJ been on the glide slope, it would have been way below PAT25 and would not have collided
Last edited by Senior Pilot; 20th February 2025 at 04:17 . Reason: Tidy up
Subjects
ADSB (All)
ATC
CRJ
PAT25
QNH
Route 4
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February 19, 2025, 23:29:00 GMT
permalink Post: 11831848
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QNH
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February 20, 2025, 00:01:00 GMT
permalink Post: 11831866
I used ADS-B reported GEO Altitude as my source and added the EGM96 correction for the lat/long of KDCA. Given that, nothing in the chart is derived from pressure altitude. As an aside, I did take a look at QNH adjusted pressure altitude (to get calibrated altitude) and it was largely in agreement with Geo Altitude. The exceptions were two helicopters N11PP and N22PP, and I don't know if it is something I am doing wrong in my calculations or something wrong with their ADS-B equipment.
Subjects
ADSB (All)
KDCA
QNH
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February 20, 2025, 07:51:00 GMT
permalink Post: 11831998
I used ADS-B reported GEO Altitude as my source and added the EGM96 correction for the lat/long of KDCA. Given that, nothing in the chart is derived from pressure altitude. As an aside, I did take a look at QNH adjusted pressure altitude (to get calibrated altitude) and it was largely in agreement with Geo Altitude. The exceptions were two helicopters N11PP and N22PP, and I don't know if it is something I am doing wrong in my calculations or something wrong with their ADS-B equipment.
Subjects
ADSB (All)
KDCA
QNH
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February 20, 2025, 08:54:00 GMT
permalink Post: 11832026
For Heaven's sake! Altitude, altitude, altitude QNH QNH QNH!
A published glideslope (usually nowadays defined by ILS or GPS) is predicated on HEIGHT above the touchdown point , ie it is a physically fixed plane referenced to the ground. How the altimeter is set is completely irrelevant to an aircraft on the glideslope from that point of view. But this aeroplane was on a visual aproach so altimetry is also irrelevant as it is not constrained by a rigidly defined instrumented glideslope.
While the helilane limit is, technically, predicated on an altitude that's really just semantics in this case as it is over water that is at sea level and as any PPL should know that gives height above sea level with QNH set. Thus to all practical intents and purposes the heli routes are flown at heights, and as the rad alt is an order of magnitide more accutate than a bar-alt pilots will likely set its bug at 200ft and and such a low level as this where bar-alt inaccuracy is very significant will (or should) fly that, despite having set QNH because that's the requirement. That way both aircraft are on the same plane of reference, ie vs. the ground = height.
The graphic above is surprising illustration of how a lateral error of just 200m puts a helo firmly into the acceptable glideslope parameters and surely demonstrates more clearly than anything else we've seen the insanity, even irresponsibility of the design of this piece of airspace. Mind, get 200m off track in the vicinity of Heathrow, let alone crossing it and you'll be ordered out of the system the way you came in with a telephone number to call...
Still no word on why this route couldn't have been designed with a sensible vertical separation above the f/w flightpath, someone must know.
A published glideslope (usually nowadays defined by ILS or GPS) is predicated on HEIGHT above the touchdown point , ie it is a physically fixed plane referenced to the ground. How the altimeter is set is completely irrelevant to an aircraft on the glideslope from that point of view. But this aeroplane was on a visual aproach so altimetry is also irrelevant as it is not constrained by a rigidly defined instrumented glideslope.
While the helilane limit is, technically, predicated on an altitude that's really just semantics in this case as it is over water that is at sea level and as any PPL should know that gives height above sea level with QNH set. Thus to all practical intents and purposes the heli routes are flown at heights, and as the rad alt is an order of magnitide more accutate than a bar-alt pilots will likely set its bug at 200ft and and such a low level as this where bar-alt inaccuracy is very significant will (or should) fly that, despite having set QNH because that's the requirement. That way both aircraft are on the same plane of reference, ie vs. the ground = height.
The graphic above is surprising illustration of how a lateral error of just 200m puts a helo firmly into the acceptable glideslope parameters and surely demonstrates more clearly than anything else we've seen the insanity, even irresponsibility of the design of this piece of airspace. Mind, get 200m off track in the vicinity of Heathrow, let alone crossing it and you'll be ordered out of the system the way you came in with a telephone number to call...
Still no word on why this route couldn't have been designed with a sensible vertical separation above the f/w flightpath, someone must know.
Subjects
QNH
Separation (ALL)
Vertical Separation
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February 21, 2025, 05:17:00 GMT
permalink Post: 11832710
Geometric altitude in ADS-B is GNSS derived and is inherently imprecise - offsets by hundreds of feet are not uncommon. When making these kinds of analyses, you need to use the ADS-B barometric altitude, and correct for the QNH and temperature at that time, using the standard altimetry formulae to obtain AMSL. Aircraft altimeters in order to be serviceable have to indicate correct within +/-60ft of pressure altitude, between 0 and 30'000ft. ADS-B encoding reduces the resolution to 25ft as you've noticed.
Subjects
ADSB (All)
QNH
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July 31, 2025, 08:41:00 GMT
permalink Post: 11931111
What is likely to make a media deal is the wrongly calibrated ( or QNH setting) of the PAT altimeters which might open discussion on the real issue : the initial 100 feet procedural separation
Subjects
ATC
QNH
Separation (ALL)
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July 31, 2025, 22:41:00 GMT
permalink Post: 11931566
My impression was not that they were wrongly calibrated, but that they were simply
bad
. It sounds like the barometric altimeters in the helicopter type in question might not be taking the helicopter's own backwash/downwash into account.
Subjects
ATC
QNH
Separation (ALL)
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