Aeronautical Charts "FI" identification beacons

[ScottBouch]

Hi all,

What does "FI" stand for?

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/455x136/fi1_65d7c2307acb08257c4e4a966b77f2438d7b24c5.jpg

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/239x180/fi2_167b1bc2d502d75249c2f42977f7e23fa53f0331.jpg

I used to volunteer at Cranfield on the Lightnings there, I recall a green flashing lamp on the roof of a building flashing away Morse code at night; is this the identification beacon referred to here?

This lamp was like an upturned bin, of a translucent green material, with a bright lamp inside. I imagine there may be a few types out there.

I found this online which may be related to the FI notation: https://ppltutor.com/air-law/signals/identification_beacons/ but any advice on this is welcomed!

Cheers, Scott.

[PPRuNeUser0211]

Hi all,

What does "FI" stand for?

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/455x136/fi1_65d7c2307acb08257c4e4a966b77f2438d7b24c5.jpg

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/239x180/fi2_167b1bc2d502d75249c2f42977f7e23fa53f0331.jpg

I used to volunteer at Cranfield on the Lightnings there, I recall a green flashing lamp on the roof of a building flashing away Morse code at night; is this the identification beacon referred to here?

This lamp was like an upturned bin, of a translucent green material, with a bright lamp inside. I imagine there may be a few types out there.

I found this online which may be related to the FI notation: https://ppltutor.com/air-law/signals/identification_beacons/ but any advice on this is welcomed!

Cheers, Scott.

You've got it - night visual ident beacon for the airfield is a large light flashing a Morse ident. A bit like the old letter identifiers that had to be laid out horizontally for daytime VFR. Essentially useless in the 21st century though!

[ScottBouch]

Thank you! Yes, this is of retrospective interest / research!

So the remaining question is can anyone find what the initials "FI" stand for?

I'm tempted to make an obvious assumption here, but am going to put that aside in anticipation of correct confirmation, as we all know what ASSUME stands for!

Many thanks, Scott.

[PPRuNeUser0211]

Thank you! Yes, this is of retrospective interest / research!

So the remaining question is can anyone find what the initials "FI" stand for?

I'm tempted to make an obvious assumption here, but am going to put that aside in anticipation of correct confirmation, as we all know what ASSUME stands for!

Many thanks, Scott.
Could well be F-L, my exaggeration, to describe a flashing light. That's certainly how light houses (those that were flashing not occulting) were annotated, though those included the flash pattern.

[MPN11]

I''m tempted to offer "Fl" with the L in lower case, as in 'flashing'. [oops, beaten to it!] That annotation on charts seems to apply to all locations in UK with the famous "Pundit", regardless of airfield designator ... https://en.wikipedia.org/wiki/Pundit_Beacon

[ShyTorque]

Flashing Ident.

[charliegolf]

Flashing Ident.

Yep. We used to learn that sh1t in the last century, eh Shy?:ok:

CG

[ScottBouch]

Thanks for the info on Pundit Beacons! Every day's a school day.

So it's either FI for Flashing Ident, or Fl for Flashing.

I knew this wouldn't be straightforward!

[ShyTorque]

Yep. We used to learn that sh1t in the last century, eh Shy?:ok:

CG

We did, but it was obviously SO last century.. :cool:

[ORAC]

Doing a bit of digging, and via admiralty charts, it would appear to be an international standard…..

https://en.wikipedia.org/wiki/Light_characteristic


https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/800x465/image_c9225a568bfb729f99347163cdd987657848120c.png

[Professor Plum]

It stands for “F**king Interesting”

There have been many a night where I’ve been tooling around, and decided to look out the front window to see a flashing beacon at an airfield.

“Thats F**king Interesting” thought I.

On landing and checking the charts legend, my suspicions were confirmed.

[ScottBouch]

It stands for “F**king Interesting”

There have been many a night where I’ve been tooling around, and decided to look out the front window to see a flashing beacon at an airfield.

“Thats F**king Interesting” thought I.

On landing and checking the charts legend, my suspicions were confirmed.

I love that! :)

[ScottBouch]

Doing a bit of digging, and via admiralty charts, it would appear to be an international standard…..

https://en.wikipedia.org/wiki/Light_characteristic


https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/800x465/image_c9225a568bfb729f99347163cdd987657848120c.png

Thank you, so according to that Wiki page, it is Fl for Flashing. Confirming MPN11's original post.

I'm glad I didn't go with my assumption of Flashing Ident! Knew I'd be wrong.

Many thanks all! Questions answered, and a laugh on the way!

Cheers, Scott.

[Andrewgr2]

I seem to recall that in the post war period when there were lots of airfields and relatively little street lighting pilots flying at altitude on clear nights could see dozens of Fl beacons at any one time. Can anyone confirm?

[chevvron]

I seem to recall that in the post war period when there were lots of airfields and relatively little street lighting pilots flying at altitude on clear nights could see dozens of Fl beacons at any one time. Can anyone confirm?
Still happens Fl green for civilan and Fl red for military airfields; these are called 'Ident Beacons' as they flash a 2 letter code in morse.
Seldom used in the UK but an Aerodrome Beacon (ie no ident) flashes either alternate white/green (civil) or alternate white/red (military). If you ever fly over New York in the dark, you will see literally dozens of the white/green ones.
Smaller civil airfields in the UK are allowed to display a flashing white strobe light during their hours of operation but in this case, there must be no other strobe within about a 10nm radius to avoid confusion as there is no ident with this system, it's just for location. Typical examples of these are Fairoaks in Surrey and about 10 miles away, Blackbushe in Hampshire.
One final one, there is a solitary 'lighthouse' which is operated by Trinity House which flashes white. Back in the '30s, many airfields had this, Croydon being one; the last one operating as far as I know is at RAF Cranwell, on the top of the College building some 30 odd miles from the sea but observable from ships off the coast.

[MENELAUS]

I think most US airfields ( O’Hare certainly has ) still have the rotating airfield beacon (white with a horizontal beam….think the closing scenes in Casablanca in the fog ! ). Quite what use their are these days lord knows.

[MPN11]

Nostalgia moment ... at RAF Strubby in the 60's, driving around the airfield to turn off the Pundit when night flying finished [around 0400 on a bad day!]. And if the fog had rolled in from the coast, getting lost on my own airfield!

[NutLoose]

Do they still use the cloud height lights, Odi used to have one next to the gliding club building. one vertical and one that used to run up and down the vertical beam to triangulate the height..

[SASless]

In the United States......

Airport/Heliport Beacons

Airport and heliport beacons have a vertical light distribution to make them most effective from one to ten degrees above the horizon; however, they can be seen well above and below this peak spread. The beacon may be an omnidirectional capacitor-discharge device, or it may rotate at a constant speed which produces the visual effect of flashes at regular intervals. Flashes may be one or two colors alternately. The total number of flashes are:

24 to 30 per minute for beacons marking airports, landmarks, and points on Federal airways.
30 to 45 per minute for beacons marking heliports.

The colors and color combinations of beacons are:

White and Green- Lighted land airport.
*Green alone- Lighted land airport.
White and Yellow- Lighted water airport.
*Yellow alone- Lighted water airport.
Green, Yellow, and White- Lighted heliport.NOTE-

*Green alone or yellow alone is used only in connection with a white-and-green or white-and-yellow beacon display, respectively.


Military airport beacons flash alternately white and green, but are differentiated from civil beacons by dualpeaked (two quick) white flashes between the green flashes.
In Class B, Class C, Class D and Class E surface areas, operation of the airport beacon during the hours of daylight often indicates that the ground visibility is less than 3 miles and/or the ceiling is less than 1,000 feet. ATC clearance in accordance with 14 CFR Part 91 is required for landing, takeoff and flight in the traffic pattern. Pilots should not rely solely on the operation of the airport beacon to indicate if weather conditions are IFR or VFR. At some locations with operating control towers, ATC personnel turn the beacon on or off when controls are in the tower. At many airports the airport beacon is turned on by a photoelectric cell or time clocks and ATC personnel cannot control them. There is no regulatory requirement for daylight operation and it is the pilot's responsibility to comply with proper preflight planning as required by 14 CFR Section 91.103.

[BEagle]

Our night cross-country during Jet Provost basic training included a 'pundit crawl'. But in those days there were considerably more RAF aerodromes in existence....

One of the jolly japes played on new lads working in the ATC tower was to "Take a cup of tea over to the chap in the pundit", who was described as having a lonely existence tapping out the ident with his morse key. The poor lads would wander round the pundit trying to find the door until the penny dropped!

[DaveReidUK]

Thanks for the info on Pundit Beacons! Every day's a school day.

So it's either FI for Flashing Ident, or Fl for Flashing.

I knew this wouldn't be straightforward!

Some CAA charts have a legend that shows "FIG" (for green beacons at civil aerodromes) and "FIR" (red beacons at government fields), so the middle initial is almost certainly an uppercase "I" (for Identification) and not a lower case "L".

[chevvron]

Do they still use the cloud height lights, Odi used to have one next to the gliding club building. one vertical and one that used to run up and down the vertical beam to triangulate the height..
I think most units with a met office both military and civil had one of these but they were withdrawn with the change to laser heightfinding.

[DuncanDoenitz]

Why would it be an upper-case "I" for "Identification", when its obviously there solely for the purpose of identification? Why not also "L", for light?

On nautical charts (as per ScottBouch at post #13) all the symbology is relevant in describing the characteristics of the light;
F = abbreviation for fixed (ie a steady light).
Fl (Capital Foxtrot, lower case Lima) = abbreviation for flashing. (a system of digits and characters may follow to define the quantity and duration of cycle).
G = abbreviation for Green; R = Red, and so forth.

Therefore, I suggest; FlR =Flashing Red.

[DaveReidUK]

Why would it be an upper-case "I" for "Identification", when its obviously there solely for the purpose of identification?

At the risk of stating the obvious, stating the obvious is commonplace. :O

[DIBO]

A preserved one https://www.stampe.be/en-gb/verzameling (and then click on the 'The collection' button in the top menu)

[ShyTorque]

I think the “I for ident” is because some, but not all of these lights flashed their station ident in morse code.

Others just flashed on/off without a specific code.

[PPRuNeUser0211]

I think the “I for ident” is because some, but not all of these lights flashed their station ident in morse code.

Others just flashed on/off without a specific code.

In chart sense the correct way of presenting that would be Foxtrot lima (Letters of ident), in the same way that charts present lighthouses. As above with the nautical chart decode, it's not telling you what kind of light it is, but what you expect to see from the light. F being fixed, Fl being Flashing(with code) and Oc being Occulting(with code).

[gunning]

I'm old enought to remember fondly the large green flashing ident light at Heathrow, near the southern perimeter road. I doubt whether that would be of much use nowadays ... I wonder what happened to it, it must have some historical value.

[FantomZorbin]

Station Ident Beacon = Pundit ... but why? Who/what is Pundit?

[DaveReidUK]

I'm old enough to remember fondly the large green flashing ident light at Heathrow, near the southern perimeter road.

It's still there in spirit. :O

https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/298x387/beaconroadroundabout2_8a4f416f5580281d1f38763b070ffb502acfd9 5b.jpg

[MENELAUS]

Station Ident Beacon = Pundit ... but why? Who/what is Pundit?


Google is your friend. Presumably because they transmitted the airfields Pundit code.
A pseudonym no doubt in an attempt to keep it quasi secret. Like “ Tube Alloys “. There’s a whole section on pundit lights. They even had mobile pundit units to deploy them away from airfields as decoys etc.

[MPN11]

Station Ident Beacon = Pundit ... but why? Who/what is Pundit?
FZ, I'm shocked!

https://en.wikipedia.org/wiki/Pundit_Beacon

[chevvron]

I think the “I for ident” is because some, but not all of these lights flashed their station ident in morse code.

Others just flashed on/off without a specific code.
They would flash the same letters as the station code letters which are positioned near the signal square.

[deltahotel]

Cranfield being CD. With my slightly nerdy yachtie head on all maritime lights have a colour (default white), characteristic (Fl, Occ numbers etc) and a period eg Fl (2) 5sec would be two white flashes every 5 seconds.

Airfield ident lights are red (military) and green (civ) and Morse coded to the airfield so I guess that detail is not portrayed on the aeronautical chart.

Coincidentally we had this conversation in the car two days ago:

’Didn’t there used to be a flashing red light at Waddington?’
’Yes, it’s the Pundit flashing a morse ident, probably WA’
’Why’s it called a Pundit?’
’mmmmmmmm’. Goes to google.

[oxenos]

the last one operating as far as I know is at RAF Cranwell, on the top of the College building
Known in my day as (http://nown in my day as) "Wxxxing Willy"

[ShyTorque]

The red one at RAF Newton (located at ground level on the south side of the airfield) was still working for some years after the airfield closed. There’s no sign of it now though. Hopefully it’s gone to a museum because it had been the only “nav aid” at Newton.

[BEagle]

Cranwell's 'Willy' is an aeronautical light house rather than a Pundit.

It seemed much brighter when I was there in 1968 than when I was there a few years later - was the wick turned down?

[MPN11]

Cranwell's 'Willy' is an aeronautical light house rather than a Pundit.
It seemed much brighter when I was there in 1968 than when I was there a few years later - was the wick turned down?Economies strike in unexpected places! Probably got to dim LEDs.

[chevvron]

Some CAA charts have a legend that shows "FIG" (for green beacons at civil aerodromes) and "FIR" (red beacons at government fields), so the middle initial is almost certainly an uppercase "I" (for Identification) and not a lower case "L".
No it's definitely a lower case 'L'.

[chevvron]

Economies strike in unexpected places! Probably got to dim LEDs.
Yes I understand the light output has been reduced. Trenchards 'brats' haven't cleaned the windows recently.

[chevvron]

The red one at RAF Newton (located at ground level on the south side of the airfield) was still working for some years after the airfield closed. There’s no sign of it now though. Hopefully it’s gone to a museum because it had been the only “nav aid” at Newton.
Apart from the CADF/DRDF.

[deltahotel]

The cupola over the RAF College main hall houses the last operational aerial lighthouse in the UK, a legacy from days when RNAS aircraft operated between the east coast and Cranwell (HMS Daedalus).
In the 1920s and 30s, ahead of radio navigation aids, a network of aerial lighthouses had been set up to guide aircraft at night. In the dome is a light, which, in the early days, could be seen as far as thirty miles away as the UK’s most inland lighthouse. The modern light is not so powerful and scans at 15 rpm.

copy and paste from this:

https://www.cranwellian-ian.com/ewExternalFiles/Tour%20Guide%20-%20Chapter%201%20v0.3%20Dec%2019%20%28NXPowerLite%20Copy%29. pdf

[ShyTorque]

Apart from the CADF/DRDF.

I’m well aware of those, having done QGH letdowns (some quite good, some definitely not, as in “I don’t recognise this place, can you see an airfield?”), but I wouldn’t consider them Navaids in the usual, pilot interpreted sense, any more than a ground based radar is.

We could otherwise perhaps include the steam plumes from the power stations on the river Trent bubbling through the cloud layer below and asking for true bearings from other airfields in that area. ;)

[MPN11]

I’m well aware of those, having done QGH letdowns (some quite good, some definitely not, as in “I don’t recognise this place, can you see an airfield?”), but I wouldn’t consider them Navaids in the usual, pilot interpreted sense, any more than a ground based radar is.
Nothing wrong with a decent QGH. I was brought up doing endless QGH letdowns, with simultaneous UHF and VHF. As a trainee, we got so busy my screen controller ended up doing 2/3 high-level UHF [Canberras/JPs] while I was also doing 2/3 low level VHF [Varsities]..

Fun times!

[ShyTorque]

But it depended more on the skill of the controller, rather than the pilot, to make it a good one.