CH-124 Sea King Historical Thread

[Baz]

I looked for an actual historical thread for the Sea King and didn't see one. So then I looked for a historical thread location on the site, and the only one was for the Army. So I'll just drop this here, mods feel free to move.

I've been doing research at Shearwater Aviation Museum on primarily the Sea King (not just the Canadian one), but also the Tracker and the Bonnie. So this is a thread to post some interesting tidbits and ask questions. Feel free to join in.

 

[Baz]

ASW Mission Management

I was looking at the original requirement for the Sea King, which is only about 20 pages long, and saw fully half of a page was for a "computer" to allow the pilot to manage the mission. Interestingly, the computer required didn't exist yet, especially for relative plot (ie screening), tracking, and attacks. As for as I can tell it didn't exist until the mid to late 70s ASN-123 (without proper radar integration), or the mid 80s TANS in the RN HAS Mk 5.

Interesting, it also wasn't really needed at first because the RCN flew the aircraft like the USN. It was primarily an inner screen aircraft (the Tracker's took the outer screen), and was under control of Bonnie's Air Direction Center. As an aside, it's quite impressive that the RCN did 24/7 ops keeping 4 Trackers and 2 Sea Kings plus an H-04S Pedro, airborne. The much larger Essex ASW conversions weren't doing that.

A side note: the first three aircraft were delivered (directly from Sikorsky) without any ASW gear, as it wasn't available. The remainder, built by United Aircraft of Canada, had the same basic fit as the USN SH-3A (ASA-13 "computer" and AQS-10 sonar). They also had some serious personnel problems getting the capability to sea (which they had told the government was extremely important to be done quickly). It feels like if you changed the date on some of the documentation to 50 years later and changed Sea King to Cyclone then it would be the same...

With the lose of the Bonnie and the Trackers at sea, there was a pivot (although doesn't seem to be an explicit one) from the USN model to the RN model, of the helo being independent. It's not clear whether the Sea King got a nav because everyone thought it was a great idea to have a crew like the RN, or there were extra ex-RCAF navs kicking around in, but got a nav they did.

However, they didn't follow the RN in optimizing the back end for the nav's presence. Instead they took surplus Tracker ASN-501s, which were designed for the Tracker role in the cockpit, and stuck an extra console in the back for the nav to use them. Thus was born the procedures for making the 501 go clunk to get the aircraft where it needed to be; the ASN-501 was never optimized for relative nav, dipping, or attacks (although it could have been).

This culminated in a series of mods in the 70s (right as the USN was introducing the ASN-123) which resulted in a radar, new sonar, and side facing console. The radar and sonar were tied to the ASN-501, but not optimized.

TBC

 

[Baz]

Things stayed that way, except for the advanced acoustic trials aircraft (14211, lost at sea), until the early 90s. During this time, the RN introduced the HAS(5), but there doesn't seem to be any consideration that the avionics would be a better fit for Canada (the radar was integrated so better for close control). Two things happened in the early 90s:

Firstly, the Gulf War. Even though it was understood surface surveillance was important, the only thing that was done was to add a GPS. Although that meant your plot could be manually stabilized geographically, it didn't increase the track count to what was required, nor did it integrate the radar. The number of tracks you could plot was limited by how fast the TACCO could make the ASN-501 go clunk.

Secondly, the introduction of HELTAS in 1992. It did have the USN ASN-123, not because of the need for rel vel screening or radar plotting, but because it was determined the ASN-501 could handle the 8 LOFAR / 4 DIFAR plot. It wasn't integrated to the radar in any way, nor was it optimized for a Nav.

In the late 90s it was decided that the entire fleet would be retrofitted with the ASN-123. This is in context of the USN determining that the 123 would be unsupportable after the early 2000s. Again, as seems to be a pattern, the 123 was installed without integration to the radar or sonar, and no "proper" way to conduct the bread and butter of Canadian Sea Kings until then, close fight dual helo tracking and attacking. It was again left to the nav to use procedures to work around the lack of integration and the pilot centric design, even while the ill fated EH-101 replacement was spec'd for something completely different.

Rev H-2(C) software in the early 2000s that the sonar and radar were (crudely) integrated, and some functionality to help with the close fight was added. Some of the functionality the USN enjoyed was never adopted. Notably, the way the USN dealt with the close fight with the co-pilot operating the computer, a ASN-123 specific datalink, was never adopted. Not only did that mean the entire plot could be shared between cockpits, but as well there were 123s in the carriers and frigates (for the SH-2S) so the ships could see what the helo had and pass situational awareness to them.

Meanwhile, the realization was made that the Gulf War wasn't a one off, as MH saw a continuous string of deployments centered around low intensity surface surveillance, which even with the radar feed to the ASN-123 the back end wasn't optimized for. The SCTF experiment also signaled the death of the HELTAS capability (which 10 years earlier had been considered a must have for transition to a new helicopter) when the 5 remaining CH-124Bs were converted to "troop carriers."

TBC

 

[AmmoTech90]

What do you mean by go clunk?

 

[Baz]

What do you mean by go clunk?

The ASN-501 was an analog computer with mechanical switching. When performing functions, such as position correct or record memory, the switches would actually go "clunk" as you pushed them.

Here's a picture of the control. All the translucent buttons at the bottom have a red light when they are on. They are the ones that go "clunk."

 

[SeaKingTacco]

Baz, have you considered writing this up for Warrior Magazine?

 

[AmmoTech90]

Thank you, that's very interesting. So the pilot had a display that recieved input from the 501 and this showed points the nav had programmed? Was it possible to have multiple points shown? Was that what the dial with 1-17 and MB, PTO for?

Sorry for so many questions.

 

[SeaKingTacco]

I entered the fleet during the change over from 501 to ASN-123 (Baz was one of my instructors). My Sqn still had 501 equipped aircraft, but I was never taught to use the system, nor did I ever fly in those aircraft.

My recollection of the ASN-123 was that, it was relatively intuitive to use for simple ASW, but was a stone cold bitch for surface plot because of the high workload required to create and manually update surface contacts. The Rev 2C software made things a bit better with some short cuts (and very rudimentary radar integration). but you could still easily screw yourself as a TACCO by doing the wrong thing at the wrong time. The classic example was the “last two” function. There was a function whereby if you had a contact (surface or sub-surface) selected and detected a turn, you could select the last two fixes and it would keep the contact tracking relatively accurate- otherwise the ASN-123 would create a course and speed based on a average of the last (I forget the number and gave my copy of the ASN-123 manual to the museum) number of sonar and radar fixes. This is all good until you are in the short strokes of a torpedo attack: you are verifying waterspace; directing your own helo in space; arming a torpedo or possibly vectoring another helo or MPA with a very rudimentary radar. At this moment, you are in an extremely high workload environment and I cannot think of a TACCO who at somepoint, did not hit the wrong button and send his/her target zorching off into the wrong direction at almost supersonic speeds and screw up the attack and the plot.

Fun times…

 

[SeaKingTacco]

We should talk about sea bias, Baz. You taught it really well.

There were so many fun functions built into ASN-123. If you understood them all, you could really make your plot sing and dance.

 

[Baz]

Thank you, that's very interesting. So the pilot had a display that recieved input from the 501 and this showed points the nav had programmed? Was it possible to have multiple points shown? Was that what the dial with 1-17 and MB, PTO for?

Sorry for so many questions.

The was a Bearing and Range only provided to the pilot via the BDHI (Bearing Distance Heading Indicator). It was to the single point selected by "Readout," which could be one of the memories (which was selected by the dial you asked about). The normal memory was one of the points 1-17. PTO was "Point Option", which was the standard reporting point, but it worked in a special way. MB was "Moving Base," which was the provision to keep track of a moving point (like "Mother," your base ship), but was never implemented.

Here's the BDHI:


We (Shearwater Aviation Museum) have created fully functional touchscreen version of both the ASN-501 and ASN-123, with the ASA-13 in progress, for the "Sea King Interactive Display Project." This is why I've been doing the research.

 

[SeaKingTacco]

The BDHI was one of the better functions. It was a workload reducer to put something into the “readout” in the cockpit and then let the pilots figure out how to get there.

That we never figured out how to implement a repeater screen in the cockpit to give the pilots battle SA was one of bigger missed opportunities with the Sea King.

 

[Baz]

Continuing from above...

There are a couple of side notes to the installation of the ASN-123, remembering that this was in the immediate aftermath of the cancellation of the EH-101 in 1993.

First, IMP did propose an "integrated mission system." It was (probably for the best) not considered, as it wasn't well defined and most likely vaporware.

Secondly, the ASN-150, a follow on to the 123, was available by then. It was installed in the SH-60F (the carrier borne replacement for the SH-3G). It retained the ASN-150 data transfer which was based on the 123 version, but was much more capable. Firstly, it had CDU (control data unit) for each of the crew members to do things like tune radios, etc. Secondly, it had two complete displays and keysets, one in the cockpit and one for the second aircrewman. Thirdly, it could overlay graphics and a single video feed. With a radar scan converter feeding the TACCO's display it may have solved many of our surface plot woes.

However, we got the 123s surplus from the USN (some of them actually came from the LAPD who had bought surplus SH-3s and didn't need ASW gear). They were cheap so that's what we got.

 

[Baz]

The BDHI was one of the better functions. It was a workload reducer to put something into the “readout” in the cockpit and then let the pilots figure out how to get there.

That we never figured out how to implement a repeater screen in the cockpit to give the pilots battle SA was one of bigger missed opportunities with the Sea King.

We did, for both the ASN-123 and ASP. There was an open project for ASP. The powers that be (one of them being the current WComd) wouldn't allow it for "airworthiness" reasons.

Funny thing is, they didn't want the repeater to be a distraction in the cockpit because it "wasn't designed to be flown that way" yet the USN had always flown it with the co-pilot using a computer, and we had started that way with the ASA-13...

 

[SeaKingTacco]

Sorry- did not mean to imply you didn’t figure it out technically. I meant that the system could not implement it.

 

[Baz]

Baz, have you considered writing this up for Warrior Magazine?

Yeah, it's one of the reasons I'm writing it up here. I'll take these notes and give them to Christine and hopefully she can help me mold it into an article.

The other one I've been "working" on is software support to the Sea King...

 

[AmmoTech90]

We (Shearwater Aviation Museum) have created fully functional touchscreen version of both the ASN-501 and ASN-123, with the ASA-13 in progress, for the "Sea King Interactive Display Project." This is why I've been doing the research.

Thanks the answers, and thanks for doing this historical work.

 

[Baz]

Continues from above...

The Sea King in the mid to late 2000s found itself doing a role it wasn't optimized for low intensity surface surveillance), waiting for the Cyclone so not able to do any major mods, and without the transitional piece that HELTAS gave it.

What has always been missing, and was part of the replacement spec from the start, was proper integration of the radar. The separate tactical screen and radar screen makes it difficult to properly fuse the radar picture with the tactical plot. This hampers surface surveillance (and the number of tracks you can hold), and close ASW (because the sensor you use to coordinate with the other helo isn't integrated with the tools you use to deliver the attacks).

As was stated previously, the USN overcame this by linking aircraft and ships together (not to be confused with Hawk Link, on the 60B). The RN had the capability from the 80s with TANS in the HAS(5), which integrated their (much better) radar with the tac plot and had an autotracker for two radar tracks. The Sea King needed either overlaid radar or an radar tracker.

It was decided to develop a low cost and low risk (airworthiness risk; the operational risk, that it might be worse, was accepted) solution for surface surveillance called Augmented Surface Plot (ASP). ASP digitized the radar and displayed it with the plot using off the shelf hardware and in-house software (the radar digitizer was actually a 4 channel USB oscilloscope). It also provided an "autotracker" in the form of AIS (Automatic Identification System). If there was an AIS track over the green radar blob, you didn't track it with radar. Finally, there was an integrated camera to practice EO/IR plot fusion.

The ultimate purpose of ASP was to develop community knowledge on how an integrated system works by giving them something they could deploy with, as there were no resources to do something in Shearwater. Additionally, it would give the community practice in managing software. The appetite for ship's to have an ASP equipped aircraft at times overwhelmed the Wing's ability to learn from it, especially when TCDL (Tactical Common Data Link) was added, which gave the ability to pass the plot and imagery to the ship.

Unfortunately, the ASW interfaces weren't allowed to be included. When it became obvious that the ASN-123 was to expensive to support, and ASP could do the ASW and SAR tasks, V4 ASP software allowed it to include those tasks and the ASN-123 was removed. The aircraft almost had the tools to do both surface surveillance and close ASW; what was still missing was the sonar interface, and an interface to the BDHI for aircraft direction (or even better, a display up front).

The final decision was to not continue with the next versions of ASP, due to the small screen, which would have added extra interfaces including the sonar and BDHI. Instead RCAF Project envisioned large screens for both the TACCO and AESOP, with a digitized sonar, and an MX-15. Although flight tested, this version died when the decision was made to push to the Cyclone regardless of whether it was ready.

 

[Baz]

If anyone is interested I have pictures and flight manual extracts for most of this, including USN and RN Sea Kings.

This history is at the very core of the discussion of what happens if the Cyclone flops...

 

[armrdsoul77]

If anyone is interested I have pictures and flight manual extracts for most of this, including USN and RN Sea Kings.

This history is at the very core of the discussion of what happens if the Cyclone flops...

This is a refresher course so we can bring back the Sea Kings?

 

[Baz]

This is a refresher course so we can bring back the Sea Kings?

There must be enough sitting in museums and bone yards...