Posts about: "Frequency 134.35" [Posts: 7 Page: 1 of 1]¶

Observations after listening to the KDCA 134.35 audio file:

After LC provides CRJ at Wilson Bridge/1200ft/runway 33 traffic advisory, PAT25 requests visual separation, which LC immediately approves. This is several minutes prior to the collision.

LC is working at least 2 other helos in addition to PAT25.

PAT25 is responding to LC on VHF 134.35. LC is simultaneously transmitting on 119.1 and 134.35 so both PAT25 and the CRJ were hearing all LC transmissions but each was not hearing the others replies.

Immediately prior to the collision when the LC queries if PAT25 has the CRJ in sight and to pass behind the CRJ, the immediate response is “[unclear] has the aircraft in sight, request visual separation” to which the LC immediately responds “approved.” The voice sounded the same as earlier PAT25 transmissions. If so, the non-urgent tone of the reply would indicate that PAT25 had no indication that a collision was imminent and was likely looking at the wrong aircraft.

This endless discussion about UHF/VHF frequencies is a bit disturbing.
Please read the helicopter route chart.
https://aeronav.faa.gov/visual/09-05...-Wash_Heli.pdf
There is a DCA tower frequency dedicated to helicopters: "134.35 (HELI)".
And it looks VHF to me.

Edit: Sorry, didn't see that skwdenyer had already answered

I believe the controller was working two frequencies (duplexed?), probably 119.1 and 134.35, so raw LiveATC recordings would only pick up one side of the conversation.
The two traffic items probably didn't hear each other.

My understanding is the controller communicated on multiple frequencies. One for PAT25 on UHF which was not able to be heard by the CRJ. The second of the “VAS videos” edited the multiple frequency streams together in which you hear the PAT25 responses. This was not as heard by the CRJ crew. They were deprived of that awareness.

Edit: here’s vid.

As I\x92ve wrote earlier, Army Helo was on UHF freq. CT communicates on that freq as noted on the Washington sectional

Ugh, for the umpteenth time, and put it to bed, helo frequency to DCA CT is 257.6. Take another look at the chart, please. Army helicopters in that area communicate with DCA on UHF.

FYI, the PP in PPRUNE stands for Professional Pilots, stick with playing X-Plane in moms basement.

ATCDumbo
I'm all ears, excellent point. This focus on ADSB-OUT, and ADSB-IN is really a furphy in terms of this investigation to determine the facts, the whole facts and nothing but the facts.

If 5342 had ADSB-IN then PAT25 not having or not displaying ADSB-OUT could be relevant depending on 5342's cockpit display, the training of the pilots and their scanning.
5342 didn't have ADSB-IN so move along, move along, nothing to see, these aren't the droids you're looking for.

**Caveat. If the TWR display were using ADS-B for their updates and to generate Collision Alerts then the absence of PAT25 ADSB-OUT could be relevant.
But would the TWR ATC even know (or care) whether PAT-25 was ADSB-OUT capable. TWR ATC involves looking out the windows and judging the relative positions of aircraft.

Note: ATC display systems are not referenced in the NTSB Aviation Investigation Preliminary Report. This seems to be a glaring omission. So perhaps the NTSB are either very dumb or deceitful or both.

To further illustrate the focus on ADSB. Figure 1 Google Earth image with preliminary ADS-B data for flight 5342 and radar data for PAT25.
The ADS-B plots are 1 seconds intervals, the radar data are 4 second interval (as stated during US Congress Q&A).
So the focus is on the whizz bang ADS-B kit rather than what the ATC saw on their display.

There is reference to ATC radios, and 5342 was on frequency 119.1 MHZ and PAT25 was on frequency 134.35 MHZ. The ATC could've had them on the same frequency (changed PAT25 to 119.1 MHZ) but this would be abnormal. ATC Voice Switch systems like Frequentis, SITTI and Rohde & Schwarz typically have a frequency coupling, whereby controller broadcasts on multiple frequencies (2 or more) and voice communications on one frequency are heard on the other. In this case, ATC would broadcast on 119.1 MHZ and 134.55 MHZ and 5342 would hear instructions for aircraft on 134.55 MHZ, and PAT25 would hear instructions for aircraft on 119.1 MHZ.

Yes, visual separation is typically used close to an aerodrome where the ATC is applying visual separation to reduce the standard from 3NM to something less, 2NM, 1NM, or even less, depending on the circumstance which includes weather (included visibility), day / night, workload to monitor the separation, plus other considerations such as equipment.

I just wonder how many of the January Route 4 Helicopter plots crossing RWY 33 Approach (post 1346) were the result of ATC issuing a control instruction to change the track to closer to the shoreline or further over water.

Use of Route 4 during RWY 33 Approaches or RWY 15 Departures is possible providing a clearance limit is imposed prior to assigning relevant traffic, positive control instruction(s) and in the case of 5342, advising them of the relative position of PAT25 and that PAT25 would be maintaining separation from them.

Example for Route 4 southbound would be a clearance limit of Hains Point. Helicopter would be released past this point when there is no conflict (nil traffic) or assigned separation to avoid (pass behind). If there is a in-line stream of arriving traffic then Route 4 may not be available.

Sydney KSA has something similar for one of their helicopter routes - BONDI 5 (yep, named after the beach), delays may occur when RWY 07 is in use for DEP, or RWY 25 is in use for ARR. Further, the route is not available when RWY 16 PRM approaches are being conducted. Sydney KSA helicopter routes are in text form - TRACK TO..., TRACK VIA..., EAST OF..., and the INBOUND routes to Sydney KSA have a clearance limit in the clearance. A map display is very useful however it should be based on route descriptions. Perhaps the committee of 17 knows the history of the helicopter routes in and around DCA.