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UTILITY-kuuntelu >> NDB >> Reverse Beacons explained
http://peditio.net/utility/YaBB.pl?num=1193049012

Aiheen aloittaja OH5YW Pvm 22.10.07 - 13:30:11

Aihe: Reverse Beacons explained
Kirjoittaja OH5YW Pvm 22.10.07 - 13:30:11

Jack Woods:

In some parts of Europe, mainly Russia and former Russian controlled
countries and generally restricted to military airfields we sometimes come
across a beacon whose callsign can be transmitted in reverse. As an example
if you have a beacon located as perhaps an outer marker on the approach to
a runway that uses the identification AB it can be sometimes switched to
transmit BA. In many circumstances such as this the beacon is not another
beacon located at the opposite end of the runway but in these circumstances
the beacon is still in the same location and the callsign has just been
changed. Often there is another locator beacon at the other end of the
runway anyway using a different frequency and callsign.

So what is the point in having a beacon whose callsign can be reversed and
why in general are these beacons located only at military or joint
civil/military airfields? The purpose of "reversing" the beacon callsign is
to provide an indication to other aircraft in that area that a system of
what is called "Reverse Runway Operation" is in progress. Reverse Runway
Operation is an operational system used solely by the military where they
carry out landings against the normal operational flow.

Normal operations would be if the current wind is such that runway 25 is
the operational runway and aircraft are normally landing and departing into
wind and that runway has a NDB locator transmitting AB on a certain
frequency. Runway 07 is also equipped with a locator perhaps with the
callsign C on a
different frequency. When Reverse Runway Operations are in progress as part
of military flight training these aircraft would be landing and departing
with the wind behind them, using runway 07 instead of the normal
operational end of runway 25. The operational runway has not effectively
changed, other civil and military traffic would still be using runway 25 so
the locator C
would not have been activated. However the locator for runway 25, in this
example AB would be changed to transmit BA using the same frequency and
transmitter.

The purpose of reversing the locator callsign is to alert other traffic
that military training is taking place and those flights are operating
against the normal flow of air traffic. For both pilots and Air Traffic
controllers
this is an important consideration for sequencing landings on both the
operational and non-operational ends of the runways and even more so when
planning "Go around" clearances to approaching aircraft in the event of
what is termed as a missed approach. The last thing any pilot or controller
needs is two aircraft meeting eyeball to eyeball from opposite directions.

Why do military pilots practice Reverse Runway Operations? Simply because
they are military and can often use such approaches during invasion or
combat, especially when only one end of the runway has perhaps been secured
by ground forces or natural terrain. I think just about every airforce in
the world practices Reverse Runway Operations however it seems to be only
the former Eastern block that decided reversing the beacon callsign would
be an alert system to other aircraft in the area that such operations are
in progress. From a former ATC point of view I personally think this is a
good
idea from a aviation safety point of view and Reverse Runway Operations are
fine if you know that they are occurring.

During my time in Air Traffic Control at Belfast Aldergrove we experienced
military Reverse Runway Operations unfortunately nobody told us until it
was almost too late. About 25 years ago we were operating as normal on
runway 25 or 26 as it was then and all the control tower staff and approach
staff
were concentrating on that end of the runway. We handled a lot of military
aircraft that were supporting the military ground forces here during the
"Troubles" including a large amount of Army and Airforce helicopters. All
this was of course mixed with our normal civil private and commercial
traffic. Normal procedure was if an aircraft requested a runway that was
different to the one in use they made that request to our approach and they
liased not only with the visual control room but also other local traffic
so as no potential conflicts would arise. When an aircraft was being
cleared to land the tower controller would quickly check the far end of the
runway
just in case a vehicle or aircraft had strayed onto that end of the runway.

In the incident we encountered a scheduled passenger flight from London had
been cleared to land on Runway 25, the operational runway, and he responded
by asking did we want him to land on the left or right side of the runway
due to the military aircraft on finals at the other end. We all quickly
turned to look out onto the 07 approach and just coming into view from
behind a hanger low-level was a RAF C130 that we knew absolutely nothing
about. A panic phone call was made downstairs to approach radar to ask what
the heck they were doing and we learned that they also knew nothing about
the C130. They had seen it pop up fairly close in on radar and assumed it
was an RAF helicopter under our control carrying out a regular perimeter
check.

Now you can imagine the panic this caused us having a C130 approaching from
the other end of the runway not talking to anyone so we had no idea what it
was planning on doing! If we instructed our landing scheduled aircraft to
carry out a standard go around there was every chance that this C130 would
do the same and we would have a large pile of scrap metal in the middle of
the airfield along with a hundred or so dead bodies. Now that generates a
large amount of paper work! The only thing we could possibly do was to
instruct our scheduled aircraft to turn immediate north and commence a
climb to the standard go around level while at the same time holding our
breath and praying that the C130 would not try to do something similar. At
the
same time radar was alerted and instructed not to sequence any other
aircraft until we knew for sure what the intentions of the C130 were. We
were also
in phone contact with RAF Operations to try to establish from them what was
happening. RAF Operations were responsible for handling all military fixed
wing aircraft landing with us and as such all military aircraft were
required prior notification to them of their intention to land. In this
case RAF Ops knew a little as we did, this aircraft was not notified to
them and
had also not spoken to them.

With everyone in the dark all we could do was sit back and watch what was
going to happen. The C130 plonked itself down on the runway and stopped
just before the intersection before turning around, backtracking and left
the runway into the area where the Army helicopters were based. It stopped
for
a few moments and kept the engines running while we were able to see a
number of personnel run from the SAS compound that was located there and
climb
onboard. Within a couple of minutes the tail ramp was closed and the
aircraft started to move again and taxi back towards the runway, still not
talking to anyone!

This was causing major problems for us and we tried using the signal lamp
but it ignored all attempts and at the same time we were having to stack
aircraft everywhere that was clear of the approaches because we still had
no idea what this aircraft was for doing. It entered the runway again and
taxied to the intersection before turning around and departing in the
direction it had approached low level. Once out of the ay we were able to
commence normal operations again but all our staff were totally stunned as
to these events.

Over an hour later RAF Ops, contacted us to advise that they had
established the C130 was on a top-secret mission to collect an SAS team and
apparently the crew had been instructed from the highest levels to observe
radio
silence for the complete flight. Later that afternoon we had the television
news switched on and the headlines were the assault on the Iranian Embassy
in London by a SAS team to free hostages that had been held there for a
couple of days. Obviously the radio silence instruction and the use of
Reverse Runway Operations with us was a tactic to ensure that the press did
not get any advance warning that an SAS team was being brought in from
Northern Ireland to assault and enter that building. This was not the first
time the SAS had seriously messed us about operationally but it was the
last as we managed to get a meeting with their commander and RAF Ops so
that we could get some for of prior warning that they had such a mission on
and
normal air safety at the airport would not be compromised.

I hope that this provides some clear explanation of what Reverse Runway
Operations are about, how scary it can be for those not knowing what is
happening and why many former Eastern block civil / military reverse the
callsign of a locator beacon to alert other traffic in the area that such
training is happening. Locators that can be reversed usually carry a note
to that effect in the appropriate country's AIP under the entry for those
particular airfields.