TCAS and options...

[TIMTS]

I fly the police helicopter in St. Maarten, and on a patrol today I had a "situation" I would like to get more info on.

We were hovering behind a hill, about 3nm East and a little West of the extended runway centerline for rwy 27.
On the radio I could hear a Dash-8 getting a clearance to take off from rwy 27, so we stayed below the ridgeline, opposite side of the hill.
The object we were checking out moved over to the other side of the hill...and we had to follow. I waited until I could see the Dash-8 had passed my altitude and was heading south, away from me and climbing...probably 1.5-2nm away.
I then asked tower for permission to enter the departure area, calling traffic departing in sight. Tower gave permission, and we moved to the other side.
The Dash-8 then called tower and said he had traffic on TCAS 100ft below him...which by that time was not entirely true..as he was way higher than that....I was at that time about 300ft msl and 50ft agl.
Tower asked me if I heard the last transmission, and I replied that I had traffic in sight, no factor and that I was way more than 100ft away.
Dash-8 pilot came back and said that it didn't matter, I was 100ft below and within 3nm...he didn't like me being in the valley there..as it didn't leave him with many options.

So..the question of the day is...did I do anything I shouldn't have? I want to learn from this if I did. I waited until I thought the situation was without any risk for anyone, and got ATC clearance...but I realize that doesn't mean much if the other guy don't agree.
Also, how can a helicopter 50ft agl behind a climbing dash-8 leave him without options?

Thanks for any replies...

(we didn't get the bad guy btw)

[Cough]

Flying into Gatwick, we have all sorts of Helis flying around the boundary. Tower always informs us of the presence of the Helis, and I or my Co-Pilot normally try and find them visually and monitor.

I would say that if you had popped you head up earlier/combined with an R/T call, then the visual/mental picture may have helped the Capt, rather than popping up at the last minute and surprising him. If you are behind the ridge, then he won't see your TCAS return till the last minute, hence the fright.

When we know, then we can plan. When we are surprised, the plan element goes out the window, hence the strong reaction.

[Barry Cuda]

From an ATC perspective, are you sure that you were the traffic he was referring to? Could there have been anything else in the vicinity that he may have been referring to? If you are so sure that you were nowhere near him then is this a possibility...?

[Piltdown Man]

I don't think you did anything wrong but has your mode C encoder been recently checked? If it is valid, I think that you should have just generated a "proximate" traffic icon on matey boy's TCAS and then dropped down to "other" as he carried on with the departure. Additionally, below 1,000' agl most TCAS systems are TA only, so what's the panic? I also bet that an RA wasn't generated. And as his rate would have been well in excess of 1,000 fpm, I'd suggest that you should not have been considered to be "threat traffic". Unless his TCAS system is a bit suss. Suggestion for the future when down in the weeds, squawk (subject to approval, if this becomes a regular problem) only mode A. Then, with advice from ATC, you will show up but no RA advice would be isssed.

And the Dash driver sounds like he has bigger problems as well.

[TIMTS]

Thanks for the replies guys.

Yeah..it was only me and him there..so he was talking to me.
The Mode C is current, but I guess it does no harm to have it rechecked.

I will try to make an earlier call next time, but sometimes we need to move on fairly short notice.

We got complaints once from an American Eagle ATR that we were in their flightpath...when we where hovering about 5ft over the water to assist a boat, and they were passing us at 1500ft on climbout. ATC knew we were there and had no complaints.
I will try my best to not be a nuisance to airplanes, but sometimes I just don't understand the reasoning....just trying to learn.

[Miles Magister]

TIMTS,

If you follow this link, select "Safety Information" on the left hand menu then scroll down to ACAS Bulletins. There are 6 of them and all well worth a read. They explain operational situations

http://www.eurocontrol.int/acas/[/URL]

The information displayed to the pilots on a TCAS display often lags the real time situation and if the crews were using their display literally this would give them the, false, impresion that you were a treat when you had infact cleared the area.

It sounds like you are operating professionally and sensibly.

Regards

MM

[Sheep Guts]

Did the lazy Tower Controller give you as Traffic to the Dash? That was the crirtical thing missing in your explanation. If that had been done maybe the Dash wouldnt have gotten a fright. He would have gotten a command to climb with position of you as traffic on his TCAS with the distance and heights you quoted.

This is the major problem with a non radar environment and TCAS. Traffic has to be given by the controller, or you seek the traffic info yourself, or you broadcast your position. I operated in Jamaica for about 3 years, they had the same missgivngs with giving traffic information. If you are not satisfied, and you can see a problem or conflict immenant, broadcast your position to ATC or directly to the traffic concerned. Then its on the tape.

TCAS is very good tool. Used properly its a life saver. Has the Barbados Police considered intalling them in your choppers? I would serious think it a good idea especially military or police machines. Even a TCAD which has much less functions is very good.

I remmember the Owner of the NCB Bank in Jamaica had TCAS in his Global Express ( you expect) and his Augusta Chopper.

All I can say to your bosses, is embrace technology before it embraces you harder!

Sheep

[Piltdown Man]

You are not being a nuisance to others! It appears that some of the ATR drivers are unable to understand the information being presented to them by their TCAS display (assuming that you have a correct Mode C readout). It's them, not you!