[Paul_Sengupta]

Surely the comms sats are near the horizon and so the dishes would point towards the horizon like my Sky dish?

Assuming geostationary, then yes, between the horizon (more likely 15 degrees or more) and 28 degrees above the horizon, depending on the position of the satellite. This also puts the beam out towards the azimuth rather than the elevation. But satellite comms are generally at much lower power than the HF "beam towards the horizon" stuff. If they're tracking low earth orbit satellites rather than geostationary then they could be anywhere in the 180 degrees of the sky.

Your Sky dish looks more horizontal than it is actually receiving from by the way, as it's an offset feed and only using part of the parabola. The beam is still probably no more than 27 degrees above the horizon.

[ChrisRowland]

Surely the comms sats are near the horizon and so the dishes would point towards the horizon like my Sky dish?

The dishes are designed with an offset feed and are pointing higher than you would think. The comms satellites are about 35 degrees altitude, about where the sword of Orion is when it's due South, which is at 19:30 today.

[gaznav]

Thanks for the answers guys. So with the dimensions quoted in the IAIP of 2nm and 6,400ft then it is still somewhat odd. If the HIRTA was some form of 'deathray' then you would expect it to be 1.1nm/6,400ft or 2nm/12,060ft?

I did another peak at the MOD Low Flying Handbook (LFH) today and the avoid is no-where near that of 2nm/6,400ft for a small light single with pink bodies inside it. I can't reveal the exact height/ranges but I am quite content with my flying circuits to the South at Hinton at circuit height.

I think we should have a second set of figures for HIRTAs in the UK IAIP for non-complex GA aircraft flying under VFR. That way at least the aircraft commander can make an informed decision due to the aircraft type, the reliance on radio nav aids and human exposure to possible EMR?

Is there any way this could be sorted out for the benefit of all?

Gaz

[tnowak]

Satcom facilities can vary the uplink power required to meet the "mission".
HIRTA restrictions assume the worst case scenario of transmitter(s) outputting max power.
Tony

[AlanB]

In the past, I have had a Garmin 496 totally lock up and I didn't know how to reset the thing, so I was stuck with no GPS for the rest of the flight. It happened twice and I thought it was a problem with the unit. However, it did it in exactly the same position, which just happened to be in the vicinity of the Rampisham HIRTA (BBC World service I believe)....so all I can assume is that the HIRTA caused the lock up. I don't believe I was within the HIRTA, though close to it at the time though, so I'd say that to avoid them is a good idea.

Incidentally, I believe Rampisham is no longer active, even though still being marked on the charts...

[chevvron]

Exhuming an old post a CPL student of mine was criticised on his skill test for not flying through a HIRTA.
My immediate reaction was "well if that's all the examiner can find...." but it opens up further discussion.
One of the reasons we are recommended to avoid is there is a possibility of electrically activated safety devices deploying. I understand there was. Mil rotary flying through Oakhanger and the air bags (or something) went off.
Are there any ballistic chutes that rely on lectrickery? That would spoil yer day.

Happened just before I arrived at Farnborough. A Farnborough Wessex flying near Oakhanger (before HIRTA were notified on charts) and the flotation bags on the mainwheels inflated .
Oakhanger was originally a half circle orientated to the south as it is used for communication via geostationary satellites over the equator, then some dickhead decided to make all HIRTAs circles. Even the Chinooks out of Odiham don't seem to bother about it affecting their FADECs and it never bothered me when I flew through it many times except I found myself actually agreeing with James Chan.

[Dave W]

Minor point: The flotation gear on Wessex and other helicopters isn't radio operated, it is wired. However, in some HIRTA RF environments the wiring could act as an antenna inducing a voltage sufficient to active the EED (electrically explosive device) used to open the burst disk on the gas canister that inflates the bags.

Other EEDs often used in military helicopters include those on engine bay fire extinguishers and hoist cable cutters, the latter of which in particular would spoil your day if you were on the end of the wire!

[chevvron]

Minor point: The flotation gear on Wessex and other helicopters isn't radio operated, it is wired. However, in some HIRTA RF environments the wiring could act as an antenna inducing a voltage sufficient to active the EED (electrically explosive device) used to open the burst disk on the gas canister that inflates the bags.

Thanks- my post edited. Merely repeating what I was told during training.

[Miscellaneous]

There is of course an alternative risk to those being discussed…and that may be from incoming missiles, which are tracked from Hirta, in the St Kilda archipelago





Aye, I know hat, coat…

[chevvron]

There is of course an alternative risk to those being discussed…and that may be from incoming missiles, which are tracked from Hirta, in the St Kilda archipelago





Aye, I know hat, coat…

Tracks missiles fired from Benbecula, so watch out if you pay a visit there

[Miscellaneous]

...if you pay a visit there

Thankfully it's a T shirt I have, thoroughly enjoyed a few days out there based on a boat and kayaking.

Disappointingly we din't see any missiles.

I'd recommend it if getting away from it all is your thing.

[helicopterdcr]

There is a NOTAM for Weybourne on the Norfolk coast until 03/05/17 showing safe distance for cilvilian aircraft of 0.355NM and 1507FT AGL.
For military there is a whole range of distances/heights from 0.108 to 0.714NM and 7FT to 3694FT depending on pulse.

We will just have to wait and see which bits get fried as it is a very popular bit of coastline for overflying

I've not seen any reports of fried aircraft bits yet (I expect their pilots wouldn't wish to comment on the status of their own bits). I've seen aircraft parked on the ground at Weybourne on 2 occasions when flying past in the last couple of weeks when the HIRTA was again apparently active. I called the museum before going there myself and of course the old dear manning the phone knew nothing about any new fangled HIRTA. It's a pity the notam doesn't have an associated phone number to find out wtf is going on.

[Sir Morley Steven]

Do what you have been taught.

Avoid em

Alan

One of my CPL students was criticised by his CPL examiner for NOT flying through. HIRTA.

[ianfallon]

I am quite content with my flying circuits to the South at Hinton at circuit height
Gaz

You fly from Hinton ? I tend to fly circuits on the other side but plenty fly circuits in the HIRRA for sure.