AA jet and Military helicopter collide over Potomac 4

Reagan National Airport crash: Military Black Hawk helicopter collides midair with American Airlines jet

An Army Black Hawk helicopter collided midair with an American Airlines flight from Wichita, Kansas, at Reagan National Airport on Wednesday.

www.foxnews.com

 

[Alistair_Heaton]

Sorry to be a bit anal it's not meant to be point scoring.

The transponder data is barometric. They have a 1013.5 mb pressure reference and it's own icing protected port if IFR certified aircraft. The crew can't adjust anything. The data is converted into a local altitude in reference to other aircraft around it by software in the radar display system.

Problems occured close in to radar heads because the antenna can be masked by the aircraft airframe.

It's an extremely good system as is the TCAS.

From memory it's a WW2 British bomber invention. Where the aviation term strangle your parrot comes from. SYP in morse or QSP. Haven't used Q codes in 20 years

 

[Garbage1]

I agree it is not clear that primary ATC surveillance non-cooperative radar was equipped to determine altitude. Military radars are equipped to accurately determine altitude. That said it takes a combination of radars at different frequencies to detect objects at distance, and provide cue to tracking radars for precision tracking and discrimination.

Being a civilian airport, if it is solely heavily relying on transponder data from co-operative targets to determine location of target, then non-cooperative targets are safety risk.

I think this drives home the point, that military aircraft like the Helo VIP Taxi Service should be required to play by all Civilian Air Space Rules when flying so close to civilian airports.

This appears to be a situation where ATC Rules are over ruled by the Military in ATC controlled airspace. This should not be allowed within tightly controlled air space around civilian airports. This was goldtop helo, so it was purchased as VIP transport in Civilian Air Space, thus should have been optioned to operate safely and fully compliant with ATC rules and systems.

Give Regan National to Military and move all Civilian Traffic to Dulles.

Extend public transit system from DC to Dulles.

If ATC solely relying on military aircraft transponder system for information about that crafts location then we have situation where it is easy to spoof or provide inaccurate location information by military aircraft.

 

[Alistair_Heaton]

I am pretty sure the pilots accepting the service have no education about the technicalities are as you have described.

I certainly don't.

 

[DirteJoe]

I think this drives home the point, that military aircraft like the Helo VIP Taxi Service should be required to play by all Civilian Air Space Rules when flying so close to civilian airports.

This appears to be a situation where ATC Rules are over ruled by the Military in ATC controlled airspace. This should not be allowed within tightly controlled air space around civilian airports. This was goldtop helo, so it was purchased as VIP transport in Civilian Air Space, thus should have been optioned to operate safely and fully compliant with ATC rules and systems.

Although I agree military should have to abide by civilian rules around active civilian airports, it's easier said than done. My old local airport routinely had military missions being undertaken that required civilian air laws taking a back seat, due to mattets of national security.

A VIP transport route also falls under the umbrella of national security concerns, depending on whom the pax are. Those flights, training/check rides or live missions, are not something you typically want beinv handled by an ATC controller not in the know for many reasons, hence why they request visual separation to be able to do what they need to, when they need to, where they need to.

I don't have the actual codes/laws in front of me, but part of the FAA's agreement with the DoD on airspace sharing does specifically state civilian controllers are to give priority to military and comply with requests made by the crews operating those flights.
Somewhere in there, although it may be an Airforce only policy, it does state though that a MINIMUM of 500ft separation will be maintained at all times from civilian aircraft.

 

[Alistair_Heaton]

I am not familiar in the altimeter setting in anything other than HPa.

Years and years ago I used QFE or the local airfield altimeter setting to get 1000ft circuit height, don't know how this is termed these days in the USA.

Is there any obvious setting mistakes with a 29.92 altimeter?

1 mB is 26ft

Just wondering if an altimeter setting mistake by the helicopter to try and read zero art ground level might be a factor.

The elevation of where it departed from will also be a factor. Maybe it was at 200ft and they were 200ft above that?

 

[Garbage1]

If S-Mode transponder is where they getting altitude for helo, we already know from jagged S-mode flight path it is not providing reliable data compared to surveillance radar.

Altitude is back end data processing product for radars. Antenna return provides range and angles.

 

[Alistair_Heaton]

I doubt it will be a S mode transponder.

Just a C, possibly encoded so subject to altimeter setting errors.

 

[Garbage1]

Sikorsky: Updated type of Black Hawk in fatal crash passed test on same day

J. Todd Inman, a member of the NTSB, gives a press briefing Thursday on Wednesday night’s fatal crash between an

westfaironline.com

How much variance if altimeter was set that day in Florida, and flown to DC same day?

Apparently it just completed first ever ground runs in Florida that the same day.

If altimeter not an accurate assessment of target altitude, then no way it should be used to determine helo altitude when flying within 100-150' of a plane that is on final approach.

 

[LittleInch]

I doubt it will be a S mode transponder.

Just a C, possibly encoded so subject to altimeter setting errors.

No idea what the difference is but everything I've seen says the helicopter was transmitting in S mode. It was also really shifting doing over 110 kts.

So yes the military can probably ride roughshod over civilian traffic, but in that case there should not have been any traffic using rway 33. All it needed was the helicopter to claim use of route 4 until Outside the air space which would prevent us of 33 for that period. That system was just set up for a disaster.

 

[Alistair_Heaton]

S mode has data piggy backing the octodecimal and basic altimeter info which is the mode C info use by TCAS.

ATC can see if we have miss set the aircraft target values for various things. Such as altitude,speed and heading on the flight director.

How it all works and interacts realistically I have no clue apart from what need to set on the aircraft end of things.

 

[Garbage1]

The S-Mode or C-Mode Transponder would be the device communicating with the cooperative target radar beacon. Radar is a misnomer for that ATC cooperative target communication link.

Sensor data from altimeter would be data bussed to transponder for wireless transmission to tower.

Altitude Sensor takes measurement and CPU furnishes data to transponder for transmission.

Hope that helps clear up things?

 

[Cool_Controls]

My understanding is that military aircraft typically uitilize radio altimeters.

 

[Garbage1]

My understanding is that military aircraft typically uitilize radio altimeters.

That makes much more sense.

From Wikipedia: A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrainpresently beneath an aircraft or spacecraft by timing how long it takes a beam of radio wavesto travel to ground, reflect, and return to the craft. This type of altimeter provides the distance between the antenna and the ground directly below it, in contrast to a barometric altimeterwhich provides the distance above a defined vertical datum, usually mean sea level.

 

[Sym P. le]

Source of flight data collected by adsbexchange.com --> ADS-B or MLAT.

MLAT is derived from multiple receivers receiving Mode S messages from the same aircraft. Mode S is somewhat of a precursor technology to ADS-B and includes the six hexadecimal digit “ICAO” code assigned to the aircraft, but does not include the lat/lon coordinates or other information. We calculate these coordinates for MLAT targets by timing when the signal arrives at the various participating receivers.

From icao.int, more on Mode S or MLAT.

I realize now that I was errant in my previous post claiming that ADS-B data indicated a "scatter shot" flight path for PAT25. In fact, current available data for PAT25 likely comes from adsbexchange.com derivations as they had sufficient coverage to roughly evaluate location info for the area at the time of interest. The derived positioning based on third party equipment cannot be as reliable as ADS-B. It seems to me that the posted video of the radar sweep (though I can't determine the initial source) would be more authoritative on the realtime location (w.r.t. the airfield) and elevation of the two aircraft though the overlay I included earlier is very rough.


View attachment aYQQ9M2_460svh265.mp4

 

[Garbage1]

I see from Symple's post, the helo has accelerated from 74 to 106 kt between data points. 200' altitude at 74 kt, but altitude is blocked by helo icon at 106 kt before collision. Flight path of helo sure looks like end game maneuver similar to a locked-on interceptor guidance system.

 

[Sym P. le]

What I was trying to convey was that the data for PAT25 being tossed around by way of one tracking site is sketchy MLAT derived data. Take it with a grain of salt. It is only good for general information at best. I included a link (here again) to the adsbexchange.com page for the incident so that you could explore the broader context.

If the radar sweep video is legitimate, it would contain reliable information within its own context. Note the background conversation in the video as someone is recording monitor output of the recorded sweep.

 

[Garbage1]

Thanks, I understood the point you were making about sketchy data. But, I couldn't help but notice flight path similarities to interceptors, and the acceleration is consistent with the 200' climb between data points. The link you sent shows 106kt point is 400' altitude. The rapid acceleration could be an error source on what I understand is ATC airport equipment.

I agree true radar tracking should be better, and clearly for radar scope to show collision says radar had both targets at same altitude.

Clearly accuracy of data tracking is not accurate enough. ATC are Controllers Not Monitors of their airspace. IMO they should have informed helo of collision path, and directed helo how to evade. The first ATC question was like 21 seconds before, which may indicate helo was on collision path that early, which refutes the end game turn maybe?

 

[Sym P. le]

Anyone can cobble together an array of reception equipment and claim a degree of accuracy for their derivations. None of that claim has any authority. It is for general interest only. Don't even start to draw conclusions. Even the scattershot plot should tell you of the lack of precision with any parameters. PAT25 was following a disciplined flight assignment. It's not rational to imply any intentions or failures at this juncture.

The first ATC question was like 21 seconds before, ...

One problem with edited net postings is that realtime components get lost. I don't have time to assemble a multi-sourced realtime collection either. I'll wait for the bigger players to weigh in.

 

[TugboatEng]

Two airport workers have now been arrested for recording and releasing the video of the crash. They're doing everything they can to activate the conspiracy theories. These are two that actually deserve pardons.

 

[Garbage1]

The data trace for the CRJ shows a controlled decent down from 400' to 325'. So CRJ data lines up, but that is all collected from ATC controlled systems and requirements for civilian air craft. The helo data trace is based upon whatever data the military wanted to furnish. It is easy too see, that a Continuation of Government Training exercise would script the training mission to match what is expected in a real situation, where they are transporting President or VP or other top official to safety. Part of that plan has to be some sort of spoofing exact location for security reasons, and could involve elevation and speed changes.
My thoughts are based upon trying to determine some of the possible scenarios for the collision. We don't have enough information or confidence in what we have, to make any determinations. Purely just a processor exercise, innannattempt to slow the aging disease.