HIRF/HIRTA Avoidance

[EMCMan]

I am conducting a study into HIRF and have a question that has remained open in my mind for years. I know the UK operates the HIRTA scheme and, as far as I have been able to tell, it is unique. However, occossionally I get comments that other nations have equivalent schemes. So, without giving away anything that shouldn't be revealled, can anyone let me know whether HIRTA based on a knowledge of the safe HIRF environment for the aircraft are used outside the UK?

I know that the CAA list a number of HIRTA, apparently do to with Personnel Exposure.

Many thanks in advance to anyone who even reads this!

[B737900er]

Whats HIRF/HIRTA ?

[enicalyth]

EMC what do you mean and where did you look? It is all in my AIRAC Vol 323. For example the first example I found under "A" opened at the page listing a BBC Transmitter at S07 54 W014 23, radius 0.7nm exclusion elevation 2100 ft.

RF is not a mystery and its hazards well understood and documented. Sometimes at a TX site a badly fitting enclosure or door behaves like a slot radiator and a few yards of lab are roped off. Any good technician or undergrad can go through near and far fields, ionising and non-ionising radiation. It is basic stuff for an EMC person surely?

[mrmum]

From the UK IAP ENR 1.1

5.3 Activities of a Dangerous Nature

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.
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.
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.
Airborne Early Warning (AEW) aircraft operate within United Kingdom airspace and due to possible radiation hazards, all aircraft should maintain a minimum separation of 1000 m lateral and 1000 ft vertical from such aircraft. AEW aircraft can be identified as follows:
(a) RAF/NATO/USAF E-3 - a Boeing 707 with a large rotodome mounted on the upper fuselage (E-3 Orbit Areas are listed at ENR 5.3);
(b) USN E-2C - a medium size twin turboprop with a four-finned cantilever tail and a large rotodome mounted on the upper fuselage.

[EMCMan]

Thanks for the responses, but I guess that my question must not have been clear enough. Yes, I know about the HIRF environment and about its potential effects on aircraft. As non-aircrew, I am interested in how it is managed in flight. The UK IAP gives guidance on a number of HIRTA (as mrmum posted), but the effects listed are related to damage to Comms/Nav equipment and possible affects on people... no mention of possible disruption to critical systems. I guess that this means that while you wouldn't hang about in them, you would not worry about flying through them. Is this the case?

[EMCMan]

B737900er - that's either a brilliant succinct answer or a genuine question, can't work out which...

[enicalyth]

Have you read the USN report regarding the station at Harold E Holt specifically set up to study the effects of RF during maintenance. Then there are at least two incidents of disturbance allegedly caused by station Harold E Holt and QFA flights.

[GipsyMagpie]

faa report (http://www.tc.faa.gov/its/worldpac/techrpt/ar99-50.pdf)

The FAA looked at this in 1999 and reasoned that a transport category very rarely came close to exceeding the certification limits whilst operating near a typical American city. This doesn't answer you're question exactly but I would not want to be the guinea pig testing any theory that everything will be done if you fly in front of Fylingdales. Imagine flying towards it and your shiny new Full Authority Digital Engine control goes haywire in sync to the transmission modulation. I might be wrong but I don't think anyone had yet been knocked out of the sky by a HIRTA. But I bet some odd occurences have been so caused (mag plugs in a gearbox with no chips found?)

[EMCMan]

Thanks for the replies.

enicalyth - no i haven't stumbled across that report, do you have a reference?

GM - I have read the report and others and understand where the HIRF certification requirements came from; I know serveral of the guys who travelled the world doing the survey (flying of course!) As you say, annoyances, but no Catastrophic accident due to HIRF in decades - chip detectors can cause fun as can analogue pressure/temperature sensors...

Trying to paraphrase my original question, what awareness do crew have of HIRTAs and what avoidance is taken, when flying in the UK (HIRTAs are listed in the AIP) and outside the UK?

[enicalyth]

HEH ADA272018.PDF refers. It may be transcribed as AD-A272 018

Technical Report 1617 Sept 1993 VLF Harold E Holt RADHAZ Measurements by PM Hansen and J Chavez

Or simply phone Raytheon at Harold E Holt, they are very helpful.

Or I can send a pdf.

There really is no difficulty or secrecy come to that, seek and ye shall find, ask and it will be given unto you.