FJ use of Transponder Mode C

[ShotOne]

In the 80's and 90's I had the pleasure of operating unpressurised turboprops in Scottish airspace. Many of our routes were on Air traffic advisory routes. Air traffic did their best to provide separation from the (then) plentiful fast jet traffic but this was severely hampered by the fact that the big majority of the contacts had no height information. This very much increased the stress and difficulty, especially when there was weather to avoid as well. As a result ATC sometimes had to endure the buttock-clenching experience of watching two contacts merge. Mode C presumably must have been fitted. Was there some operational reason why it was mostly turned off?

[Fox3WheresMyBanana]

Always turned on in my F3 Tornado.
Don't know whether it provided reliable data when either low level or doing combat manoeuvring - maybe that was the problem?

Only had 1 airmiss, due to an airliner cutting the airway corner out of Newcastle into uncontrolled airspace at night, then him taking visual avoiding action into me instead of away. We had a video of the radar to prove who was in error.

[ShotOne]

Tssk, ! How wicked of him to cut the corner into YOUR airspace!

[Fox3WheresMyBanana]

It was free airspace - perfectly happy with that - and turned to give him a wider berth. Then at 7 miles sep. he turned into me and continued climbing into me.

[Onceapilot]

Yes. We even squawked individual codes to help the F3's try and find us at low-level:oh:.

OAP

[TurbineTooHot]

We do and straight after departure get a C check to verify. There may have been a problem with height info at low level perhaps?

And it's not OUR airspace, but if a relatively un-manoeuvrable airliner wants to deviate from the myriad of airways available to save time and cash then the captain takes his/her chances in Class G, and should get all snooty when fighters dare to be in his/her way. Or worse, dare to have the danger areas segregated so the original flight plan must be followed. Danger areas where we also wear C.

Rant off, Happy New Year, safe aviating.

[Fox3WheresMyBanana]

Ah, it's Have_a_go_at_F3's Day. (mods, we need a gallic shrug shoulders icon)

1. If you operate in uncontrolled airspace, know what you are doing. This guy didn't.
2. We didn't build the radar, just tried to get the best out of it.
3. Incomplete radar pictures were common for almost all air defence aircraft at that time, which is why all AD crews were trained immediately for 4-ship leads as anyone might have the best air picture.
4. Never heard of individual IFF codes, but that was nav **** anyway;)

[Dave Wilson]

Mode C goes up the duff anyway. I was on my way to Dublin last month when the East Mids controller asked me if I was really 1500' underground...

[clicker]

Mode S is no better at times. There's a C130 and a Tornado going around with the same 24 bit ident, both in the air at the same time last month.

Wonder if that confused the poor old controllers with the different data coming in.

[ShotOne]

Don't forget, fox3 the airline pilot didn't have any radar picture at all, never mind an incomplete one. It's surely not surprising a fighter pilot in a small light-grey aircraft would be first to spot a big brightly coloured one with rows of lights?

Turbine hot,pleased to hear you did use mode C but I assure you lots didn't. (Lossie jaguars?) Airline traffic use airways as much as possible but not always. Sometimes to save fuel and cash as you say, although you somehow manage make this sound a grubby aspiration (the Queen doesn't buy our fuel). Other times, like my opening post, because there is no airway.

[Just This Once...]

Always flew with Mode C selected, as did everyone else. Short of a switch-pigs or a unserviceability I am not sure why anyone would not have it selected in the UK as our procedures called for it.

I've no idea how anyone who does not have an interrogator can state that 'lots' don't have Mode C active.

[HEDP]

Going back to the OPs point, did all fleets have Mode C in the eighties and nineties?

[trap one]

Only fleet that didn't was the Lightnings.

[Circuit Clear]

In the 80`s there were Military ATC units that didn`t have SSR or a link from other units.
At Brawdy, the old original AR1 was used until about 1989. It was fantastic at showing in great detail all the moisture, rain, birds and occasional shipping. On a good day, the aircraft picture was superb although any conflicting traffic had to be de-conflicted with either London sector 23 or avoid!
To us, SSR was for sometime in the future and therefore we didn`t have to worry about the legalities surrounding verification, ident, Mode C accuracy etc.

[ShotOne]

"I've no idea how anyone could state...." The clue was several times a day, receiving ATC messages along the lines " ..high speed traffic two o'clock closing rapidly, no height information."

If the passengers could have heard, they'd have walked!

[Lima Juliet]

Fox3

How would you know if your Mode C was "always turned on in [your] Tornado" if it was "Nav **** anyway"? Have you got the longest neck in NATO to see behind your seat on what was selected? :p

By the way - try copying this pic... http://boards.buffalobills.com/images/smilies/shrug2.gif

Shrug it off and don't listen to the nasty boys; they're only jealous! :ok:

LJ

[Lima Juliet]

Oap

The reason why you would be asked to squawk individual codes would be so we didn't barrel into the wrong formation at low level and so we knew that we had the correct one we had briefed to do affil with. Do you remember those days? When within a 60x30 mile box there might be 4-5 four ships or pairs transitting at low level? :sad:

By the way, you couldn't get a weapons solution on an IFF return in the F3, it needed to be an established primary RADAR comtact.

LJ

[N2erk]

F3- "noli bas**rdi carborundum" . airliner driver wuz probably a fighter pilot ex or wannabe. More to the point did you get a fox 1 or did he call fox2!

[Pontius Navigator]

Dim and distant past but was it not mandated to switch Charlie off if you were squawking low level and not receiving a service?

You had not had a Charlie check with the controller he would have been a brave man giving altitude separation based on unverified data.

Just a thought.

[Just This Once...]

"I've no idea how anyone could state...." The clue was several times a day, receiving ATC messages along the lines " ..high speed traffic two o'clock closing rapidly, no height information."

You need to think more about how limited your clue was. Indeed, your question could have been phrased 'in what circumstances do secondary returns omit Mode C height information?' or 'how many primary-only radars provided ATC services in the 80s and early 90s?' rather than your presumption that we deliberately or accidentally omit to select it.

I'm sure an air trafficker of the period will be able to help.

[Wensleydale]

My memory is vague on this one, but bear with me... in the Sentry about 10 years or so ago we had a spate of F3s reporting their Mode C at minus 1,400 feet. (similar to the Dublin story above?). This figure relates to receiving a Mode C response with just the bracket pulses but no height information contained within. The problem to the E-3 was that priority for height display on console was for the Mode C height and therefore we could not get a radar height response on these targets. Requests for information about these responses from the F3 PT was not forthcoming, but we believed that they resulted from Mode C being selected to standby rather than off in the cockpit(??).


Needless to say, the Sentry software was modified to disregard such low MC responses as it would be unlikely for the aircraft to be operating at such a low level (and wanting to be seen on Mode C) so we got radar reported height back onto the displays.

[ShotOne]

Not presuming anything, jto but fwiw it happened a lot so I don't believe it was finger trouble. And why would I rephrase the post to ask about primary radar when the issue is transponder use?

[Pie Man]

Not sure of the position of the radar heads in the airspace you are talking about but I know in some areas primary and secondary radar heads were not co-located so the issue might have been to do with radar cover. Additionally, most of the ATC SSR radar heads were gated, can't remember the figure but I think it was about 7000ft/min (up or down), and if the value was exceeded the mode C was not shown on the screen.

PM

[ShotOne]

That might be part of it, pm. The radar heads, not the 7000 fpm that is, unless they were having a particularly exciting day out! I was intrigued by OAP's comment which perhaps hints the transponder was considered to be helping an opponent??

[Onceapilot]

Well, it would be a shame to miss the chance of a few Fox2's/3's:ok:. We were bombers for Gawds sake :)!

OAP