Report Released on Houston's Southwest Inn Fire

[mfn002]

KHOU 11 News obtains 1st report on deadly Southwest Inn fire that killed 4 Houston firefighters

Although a bit long (100+ pages), the report is a very interesting read. It also reveals that there were issues with the P25 system, mainly involving traffic load, reception and equipment. According to the report, at the height of the incident, the system "bonked", or rejected due to traffic load, over 700 transmissions. There was also a mysterious case of bleedover from another talkgroup that the cause of which the investigation could not determine.

 

[bpckty1]

mfn002 wrote:
"... According to the report, at the height of the incident, the system "bonked", or rejected due to traffic load, over 700 transmissions..."

One of the reasons I've heard from Houston area VFD members the "bonking" is one of the reasons (lack of interior building coverage, cost and local control are others) why their agencies left the trunked system and went to UHF conventional. And, this is before the trunked system (someone described it as Borgnet several years ago) expanded to its great size.

 

[KevinC]

I'm going to bet a large portion of the "bonks" were due to users trying to talk while someone else was already talking.

On their old analog radios 2 users could talk at the same time, you more than likely couldn't understand both of them but as far as each user knew his/her message went through. You basically had 2 losers. On this trunking system 2 users can't key at the same time, so you have 1 winner and 1 loser. I'm quite sure the loser gets frustrated and keeps trying, thereby increasing the number of "bonks".

And I completely understand that in the "heat of battle" bonks aren't good, but if someone else is already talking you're going to get bonks if you try to talk...no way around that...unless you let 2 users talk at the same time...which brings us back to 2 losers.

 

[bpckty1]

Agreed. Been there, have had both happen. Especially when 1/2 of the trunked repeaters (single tower) were down for maintenance on a busy day. But, I have had deep inside the building problems in the Galleria area with my company's STX, but not as bad as one of the building's tenants who had to stand next to a window to make his Nextel phone work while my cell phone and pager worked well inside the building.
;^>

 

[mfn002]

I'm going to bet a large portion of the "bonks" were due to users trying to talk while someone else was already talking.

That's the reason the report gave: too many units trying to talk at the same time.

 

[motorola_otaku]

More telling is what the report doesn't mention once as a potential issue: encryption. For those of you who were hoping this would lead to decryption of the tac channels, I think you are out of luck.

 

[KF5YDR]

Isn't the purpose of trunking to make the system more available?

 

[kayn1n32008]

Isn't the purpose of trunking to make the system more available?

Not really, the purpose of a trunk system is to make a small number of RF channels available to many users. This is because not every user group will be transmitting all the time.

Where I live we have a 20channel EDACS system, with every city department using it. There are probably 100 talk groups that share those 20 frequencies. Where as if each talk group were an RF channel there would be 200+ (2 frequencies needed for a repeater) frequencies needed.


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[KF5YDR]

So does each repeater in a trunked system still operate on only one (pair of) frequencies?

 

[mfn002]

More telling is what the report doesn't mention once as a potential issue: encryption. For those of you who were hoping this would lead to decryption of the tac channels, I think you are out of luck.

Actually, it makes what could be considered a somewhat vague reference to an issue related to encryption. When citing problems with "quick keys", it mentioned that when the situation spun out of control, every HFD firefighter turned their radios to SW TAC 11. This resulted in a whole slew of these "quick key" events as the radios checked in on the channel. Although it's a very, very loose connection at best, it made me think "if they didn't encrypt those channels, the stations would have been able to monitor the situation with a scanner, as opposed to having to use their radios and create those quick key events."

 

[KevinC]

Actually, it makes what could be considered a somewhat vague reference to an issue related to encryption. When citing problems with "quick keys", it mentioned that when the situation spun out of control, every HFD firefighter turned their radios to SW TAC 11. This resulted in a whole slew of these "quick key" events as the radios checked in on the channel. Although it's a very, very loose connection at best, it made me think "if they didn't encrypt those channels, the stations would have been able to monitor the situation with a scanner, as opposed to having to use their radios and create those quick key events."

Switching to a TG doesn't cause a "Quick key", that would be a VERY bad design. The "quick keys" come from people "bumping" the PTT button, like kerchunking a conventional repeater. And numerous ones of these came from units not involved in this incident.

I personally would have to agree with what Assistant Chief Mann said, "The radio system did not cause that roof to fall".

The calls for help were heard over the radio (and recorded), you can't ask for much more than that out of a radio system.

 

[KevinC]

Isn't the purpose of trunking to make the system more available?

You're missing the point. People were trying to talk on the same TG while someone else was already talking...that ain't gonna work.

 

[mfn002]

Switching to a TG doesn't cause a "Quick key", that would be a VERY bad design. The "quick keys" come from people "bumping" the PTT button, like kerchunking a conventional repeater. And numerous ones of these came from units not involved in this incident.

I personally would have to agree with what Assistant Chief Mann said, "The radio system did not cause that roof to fall".

The calls for help were heard over the radio (and recorded), you can't ask for much more than that out of a radio system.

You're right. My memory's not that good. Here's the quote:

It was further learned that some of these "Quick Keys" were the result of members in the department that weren't assigned to the incident. Members across the city had turned on their radios to listen to the incident and at some point, accidentally created a "Quick Key" once their radio was turned to the assigned monitored Talk Group (SW TAC 11).

I think the media is being a little misleading by appearing to lay the blame for the incident entirely on the radio system. In reality, it was, in my opinion, a breakdown in protocol and procedures that created the confusion. The radio system itself functioned perfectly, and it was user error and traffic load that caused most of the problems.

 

[radioman2001]

Another case of all fire ground traffic should be on CONVENTIONAL and ANALOG. As the Chief said the radios didn't make the roof cave in, but it sure added a lot of additional confusion to what sounds like a very bad scene. I see lawsuits whether justified or not coming, just like 911 all over again. Blame the technology not the administration that implemented it.

 

[motorola_otaku]

Another case of all fire ground traffic should be on CONVENTIONAL and ANALOG.

How exactly does that help with channel loading? A talk path is a talk path whether it's a trunking talkgroup or a simplex frequency - only one person can talk at a time. If any one communication issue can be blamed for exacerbating the issue it was too many people trying to communicate too many things on a single talk path - a major issue with the legacy UHF system owing to lack of available tac channels that was carried forward to the new system more or less on the back of "we've always done it this way." Sadly that was also an issue at the "close call" fire at 9343 North Loop back in 2007. Now it has been identified, put in writing, and steps are being taken to remediate it.

 

[nd5y]

So does each repeater in a trunked system still operate on only one (pair of) frequencies?

Yes.