[Morten]

The intensity may be sufficient to detonate electrically initiated explosive devices carried or fitted in aircraft.

I would have thought that any CAPs and similar relies on an EED for initial activation. If they use e.g. the NSI, there are specs regarding 'no fire conditions', which if memory serves right, for the NSI is 1A, 1m, 1W, e.g. the initiator must be able to 'ignore' a 1A current for 1 minute at 1W of power without activating.
Someone brainier than me can work out the transmitted RF required to induce a current >1A for more than 1m in the cabling connected to a typical GA, given the presumed shielding of an airframe (or not in the case of composite stuff and microlights)... for an aircraft which should, unless they are landing or taking off, be at least 500 feet away from the source.

On my XCQ, I flew from Cambridge to Wellesbourne. My planned flight was very close to the Cambridge one. When I asked at Cambridge whether they were aware of any hours of operation, they didn't seem to know anything about it at all - when they then asked an instructor he said they'd never cared much about it...

Morten

[Tim Dawson]

HIRTAs are weird, and they only seem to exist in the UK.

Presumably every other country looks at the risks involved for each emission site and classifies them as restricted or danger areas, or simply doesn't bother to classify them at all (for low/no risk). Maybe it's time they were reviewed.

[Talkdownman]

Maybe it's time they were reviewed.

....along with MATZs, AAIAs and a host of other weird wastes of space...

[Joe Dell]

There's nothing at them anymore. They're decoys. The real sites are not marked. I have it on good authority that the Fylingdales Pyramid is used to grow year round fruit and veg, and sharpen blunt razor blades. http://www.raf.mod.uk/raffylingdales/aboutus/index.cfm

On a more serious note. There are at least three strips inside that particular HIRTA, and KLM 1280 just went through it. 3,000ft below the upper limit.

[Longfinal]

Maybe it's time they were reviewed.

....along with MATZs, AAIAs and a host of other weird wastes of space...

Another vote for this - particularly the number of MATZs around barely used military airfields or for inappropriate ac types. Wittering for the former and Benson for the latter come to mind.

[Talkdownman]

Another vote for this - particularly the number of MATZs around barely used military airfields or for inappropriate ac types. Wittering for the former and Benson for the latter come to mind.

One size cannot possibly fit all...

I understood decades ago that MATZs and the associated penetration procedures was a promotion project for some Flt Louie back waaaay back in the early seventies. Review well overdue, then...

Time for the shredder...

[ianfallon]

With one right next to Hinton (Croughton) I can tell you people fly in it all the time. I do my circuits to the North, but .. !

[segillum]

One HIRTA listed at IAIP ENR 5.3 is about six years out of date. It's "RAMPISHAM HIRTA Upper limit: 2500 ft A circle, 0.7 nm radius centred at ALT 504832N 0023905W".

In the Good Old Days this was a BBC External Services HF transmitter site. It was in a beautiful location on Rampisham Down and those of us in a position to do so often found excuses to visit it ("close supervision of a major asset"). It had twelve 250kW and 500kW transmitters, very impressive antenna arrays and was indeed a HIRTA as far as military aircraft were concerned. Sadly the site was closed and demolished in 2011, much to the sorrow of myself and others.

I've been trying to advise NATS via military and civil channels for some months that the information in the IAIP is well out of date but haven't had so much as an acknowledgment. Oh well.

[gaznav]

With one right next to Hinton (Croughton) I can tell you people fly in it all the time. I do my circuits to the North, but .. !

The HIRTA at Croughton marked on the chart is worst case for an aircraft with FlybyWire or munitions/ejection seats/recocking cartridges. For smaller magneto-engine driven aircraft with cable operated flying controls then the HIRTA is much smaller. You just need access to the classified HIRTA data to know how close is safe.

I fly my circuits to the South or the North depending on where the 'meat bombs' are being dropped by the para aircraft.

Best

Gaz

PS. This is straight from the UK AIP:

5.3.2 High Intensity Radio Transmission Area (HIRTA) - Airspace of defined dimensions within which there is radio energy of an intensity which may cause interference with and on rare occasions damage to communications and navigation equipment.

5.3.2.1 Areas within which there is radio energy of an intensity which could cause interference with and on rare occasions, cause damage to, communications and navigation equipment such as Radio Altimeter, VOR, ILS and Doppler are listed at ENR 5.3. The intensity may be sufficient to detonate electrically initiated explosive devices carried or fitted in aircraft.

5.3.2.2 Only the most significant sources are listed and in some of these areas the intensity of the radio energy may be such that it would be injurious to remain for more than one minute in the immediate vicinity of the energy source. This is especially relevant to helicopter operations and the list contains appropriate warnings; however it would be prudent for helicopter pilots to avoid lingering closer than 100 m to any radar aerial. Pilots approaching oil production platforms on which dish aerials can be observed should, wherever possible, approach from a direction out of the general line-of-shoot of such aerials.

[kanga]

The HIRTA round Blakehill Farm did disappear from the charts quite quickly after the hazard transmitter was shut down. That one may have been one of the more hazardous, as

a. it involved short, very high energy, HF pulses (rather than continuous transmissions like, eg, Rampisham or Croughton). I am no RF engineer, but I would not be surprised to hear that such might have a more marked effect on, eg, jettison mechanisms; and

b. it was on a GA 'choke point' between Brize and Lyneham; and became a VRP for Lyneham until the latter closed

[Joe Dell]

We had a problem with Fylingdales up here a while back. The majority of cars affected were Beamers.


In the early 1990s, a newcomer to the North York Moors beauty spot of Goathland heard that Yorkshire Television was seeking permission to use the village for location shooting of a new series about the trials and tribulations of a 1960s local bobby.


Fearing that the village would end up being ruined, he appealed to his neighbours to oppose the request, but his pleas fell on deaf ears. Most of the residents relished the prospect of the village becoming a tourist honeypot and welcomed the television company with open arms. The newcomer promptly sold up and left but most of his neighbours stayed on and have benefited from Heartbeat, the series that put Goathland firmly on the day-trippers' road map. The village has become a shrine to the show, every other shop a treasury of gifts selling Heartbeat jigsaw puzzles, mugs and Matchbox toys, and badges demanding: "Send Us More Tourists!".


Now, however, some residents feel there could be another reason to leave Goathland: the proximity of RAF Fylingdales, the early-warning station that the British Government has told President Bush he can use as an integral part of his "Son of Star Wars" missile defence scheme.


The jury is out over whether the high-power pulses of electromagnetic radiation emitted by the truncated pyramid poses a risk to human health. Although some scientists believe it could, during a visit to the area last month, the Defence Secretary, Geoff Hoon, claimed that there was "no risk to the health of local people or livestock".


But motorists are already feeling the effects. There have been reports in recent months of visitors to the moorland beauty spot finding themselves stranded because the beams of radar pulsing from Fylingdales have triggered their car alarms and immobilisers, which operate on the same frequency. Drivers of some makes of car and many motorcyclists have been left trapped in the village and had to be towed out of range of the base by rescue services before they could restart their vehicles.


Some locals believe that the situation has got worse following the recent upgrading of the base in the wake of the September 11 terrorist attacks. Frank Doyle, who owns Bazaar, a shop in Skinner Street, Whitby, and makes regular deliveries to the Goathland area in his Mercedes Vito van, says: "It's getting beyond a joke. I've got stuck there three times in less than two weeks and have to keep calling breakdown services to get out of the place

[gaznav]

For Croughton the emitters are VERY close to the dual carriageway A43. I don't see any broken down Beemers or alike. The other thing is that the height is 6400ft (about 1nm) but the circle has a radius of about 2nm - so how can that be? Are EM Waves really that affected by gravity? (Of course not!)

[segillum]

>For Croughton the emitters are VERY close to the dual carriageway A43. I don't see any broken down Beemers or alike. The other thing is that the height is 6400ft (about 1nm) but the circle has a radius of about 2nm - so how can that be? Are EM Waves really that affected by gravity? (Of course not!)<

Croughton chiefly handles satellite uplinks in which most of the RF goes upwards rather than towards the horizon. However it also does some HF, handled by the large log-periodic antennas you see from the A43. These beam RF energy much more towards the horizon. Presumably the dimensions of the HIRTA reflect the effective radiated power (ERP) levels for both modes.

[gaznav]

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

[cotterpot]

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