Constellation Antenna

[Fris B. Fairing]

Can anyone please identify the purpose of this antenna fitted to the nose of the early Connies?

http://www.adastron.com/aviation/vault/Connie-antenna.jpg

[DaveReidUK]

Looks more like an ice detector.

[mustafagander]

As I heard it, that odd array is part of a primitive ILS antenna. Probably LLZ.

[PDR1]

Looks more like one of the original mk1 chemtrailing dispenser nozzles - the front rod is a vortex generator to ensure turbulent flow over the dispenser tube to get optimum trail dispersion.

PDR

[Spooky 2]

Can anyone please identify the purpose of this antenna fitted to the nose of the early Connies?

http://www.adastron.com/aviation/vault/Connie-antenna.jpg



I have never seen that on any Connie. Do you have any idea what airline that would have been?

[Fris B. Fairing]

Spooky

Qantas VH-EAD

[DaveReidUK]

The probe/antenna is only visible on early shots of the original Qantas 749 Constellations VH-EAA to EAD:

http://www.aussieairliners.org/l-1049/vh-eaa/1802.106.jpg


Later photos of the same aircraft don't feature it.

I still think it's an ice detector. :O

[Wodrick]

As I heard it, that odd array is part of a primitive ILS antenna. Probably LLZ.
Localizer and Glide Slope are both horizontally polarised, that would be the first antenna I have ever seen that was receiving horizontal polarisation with vertical elements.

[tonytales]

Never have seen its like and never saw any patched holes in any L-749 I worked (multiple operators) where it would have been. Might have been unique to Qantas.
thread drift - Note the two lamps, one clear the other red. They were also on L-1049 until the wx radar was installed. The clear lamp one can understand. it put light on the ground in front of you while taxiing. But what was the red lamp for? Joke was it was a "passing light" you flashed when overtaking another aircraft. Might have been hard for the other aircraft to see it. Never found out its purpose. Anyone know?

[TBM-Legend]

Red passing lights were a feature on many aircraft in that era. My WW2 T-6C had one in the landing light recess in the leading edge of the wing..

https://aviation.stackexchange.com/questions/43450/whats-the-red-light-in-the-left-wing-of-a-n-a-t-6-for/43451

[pithblot]

Could it be part of the Radio Altimeter (not Rad Alt) for Pressure Pattern Nav?

Pressure Pattern Flying, IIRC from conversations with JDW 'George' Washington and 'Slim' Rosier who both knew about these things was....

...long range Nav typically used by Qantas in the mid latitudes and low levels. Think Hobart to Auckland 8,000 - 12000ft. The difference between Departure and Destination QFE was plugged into a formula (other variables being distance, radio altitude and change of latitude, I think) to come up with a constant heading to fly.....the Connie would fly at a constant Radio altitude (thus the altitude would vary) and a single heading was flown to give the maximum tail wind component for the sector.

[DaveReidUK]

Think Hobart to Auckland 8,000 - 12000ft.

the Connie would fly at a constant Radio altitude

I have no idea what that means. How can radio discern your altitude when you're at 8,000 ft plus ?

[JohnMcGhie]

That looks like the TACAN (VOR/DME) or DME antennas found on aircraft such as I used to work on. I am more used to seeing them under one wing, but that looks like the antenna: spacing and size are about right.

It's been a long time...

[Wodrick]

How can radio discern your altitude when you're at 8,000 ft plus ?

Early radio altimeters were not like the modern Doppler type devices but were true radar altimeters, pulse devices which had a much greater range. I only learnt about them at college, never met one in anger.

TACAN - the polarisation would be right, both the bearing part and the distance part being vertical but it's a military aid why have it on a civil aircraft.

[Wunwing]

I have a friend who was a Qantas outstations engineer on these aircraft but he is on holidays right now. However while I wait his return I am wondering is it an Australian DME antenna.
Looking at all the photos that I have of Connies of that era I agree its exclusive to Qantas 749s so it has to be a system that was exclusively Australian. Australia at that time had invented and operated its own DME system. So maybe that's it.

I'll update when I find my friend

Wunwing

[Fris B. Fairing]

My thanks to Peter Clukey at Lockheed Martin for providing the definitive answer:

It is a Type 308 transmitting antenna for a Rebecca (BABS) homing system. The 649/749 Constellation parts catalog lists the two stub antennas on the nose protrusion as being two separate units, one being a Type 308 Transmitter and the other being a Type 15 Director. See items 42 and 43 on the following diagram.

http://www.adastron.com/aviation/vault/Type 308 Antenna.jpg

The receiving antenna can be seen under the name "Smith" in this image. This type of antenna was common to many other types.

http://www.adastron.com/aviation/vault/VH-EAD-2.jpg

Thanks to all who contributed.

[JohnMcGhie]

My thanks to Peter Clukey at Lockheed Martin for providing the definitive answer:



http://www.adastron.com/aviation/vault/Type 308 Antenna.jpg

The receiving antenna can be seen under the name "Smith" in this image. This type of antenna was common to many other types.

http://www.adastron.com/aviation/vault/VH-EAD-2.jpg

Thanks to all who contributed.

I thought that's what it was, but I remembered "Rebecca" as the Air Force name for them. I worked on Rebecca systems, in the Bristol Freighter and the DC-3, in 1968.

Evil device: the transmitter was a power oscillator (!!) tuned with a motorised Lecher line (go on, get the manuals out and look them both up, you won't find such evil devices anywhere these days...) :)

Packed a wallop: about 250 watts or 1 kW peak, I seem to remember. And "reliability" was not in their lexicon.

[India Four Two]

John,

This what I love about PPRuNe. I keep learning obscure trivia. I had never heard of a Lecher line:

https://en.m.wikipedia.org/wiki/Lecher_lines

How big was the Lecher line equipment? Was it built in or plugged in as test equipment?

[Wunwing]

There appears to be 2 vertically orientated side antennae as well as the nose one. Photos that I have show them on both port and starboard sides of the cockpit.

The question is why did Qantas alone have this device given at the time they were known as Qantas Empire Airways and did nearly everything in lockstep with BOAC. I can't locate any photos of BOAC aircraft with these devices

Wunwing

[Wodrick]

I42 you have read the wiki I expect. In this application they would be used as in the last line, not for measuring wavelength but as a tuned circuit in the oscillator. Not vast ¼ λ at 170 -230 Mhz not a lot and inside the box I would think.
The question is why did Qantas alone have this device given at the time they were known as Qantas Empire Airways and did nearly everything in lockstep with BOAC

That is a good question, must have been some strange Australian reason as, as far as I am concerned it is purely a military aid. I never did it on my training at college, maybe I'm too old I was only licensed in 1972.

[JohnMcGhie]

Hi i42:

The Lecher Line "size" is determined by the frequency at which it operates (around 200 MHz). In this case, "not large", maybe 18" long. It's two rods of metal in parallel with a shorting link that travels the length of them, powered by a servo motor driving a screw.

The whole thing forms a resonant circuit. in this case strapped to the plate of the transmitter valve. The further out the shorting link, the lower the transmitted frequency.

The Lecher line was mounted in the pressurized case that contained the Rebecca, surrounded by the other electronics. There was a lubricated (Vaseline!) rubber seal at one end. The thing was inflated with a bicycle pump!

The entire contraption was about the size of an office waste basket and twice the length. It was so old, not even Wickipedia has a photo of it: this is the later model! (http://www.duxfordradiosociety.org/equiphist/reb-eureka/reb-eureka-hist.html)

[Fris B. Fairing]

Back to the Type 308 transmitting antenna.

Peter Clukey from Lockheed Martin confirms that the 649/749 Parts Catalog states that this feature was unique to Qantas aircraft 2562, 2565, 2572 & 2573 (VH-EAA to VH-EAD).

Earlier I searched for this type of antenna on other operators' Connies but couldn't find any. I then widened the search to look for the companion Rebecca antenna on the side of the nose. I found only one, on BOAC Connie G-ANNT. However this aircraft appears not to have any sort of antenna on the tip of the nose.

http://www.adastron.com/aviation/vault/G-ANNT-2.jpg

While we have solved the original Qantas problem, some may feel that we now have a BOAC problem. I'll leave that to our learned colleagues to ponder.

[Fris B. Fairing]

PS: That's not a small sharks mouth but a reflection of the GPU. Don't you just love polished aluminium?

[India Four Two]

Fris B,

Your post is a nice segue into a question I was going to ask.

I’m old enough to have seen dipoles on Vampire T 11 wings at Shawbury in the late 60s. I didn’t know what they were at the time but I now know they were Rebecca receiving aerials.

My question is where were the transmitting aerials?

John,

I had read about the pressurized “can” before you posted. Initially I thought it was pressurized from the aircraft’s systems until I read about the tyre valve. Was there a pressure gauge or did you have to apply a gauge to the valve? What pressure did you pump it up to? I presume the pressurization was to prevent arcing at high-altitude.

[Fris B. Fairing]

I42

RAAF Neptunes were fitted with a similar system designed to home on downed airmen. This system was known as SARAH (Search And Rescue And Homing) and featured a Yagi type Rebecca receive antenna on each side of the nose and a single transmit antenna on the belly. Unfortunately I don't know what the belly antenna looked like but surely one of us will know.

[Sevarg]

I 44 the reb was pumped up on pre-flights with a foot pump to 5 psi. There was a pressure gauge on the pump. Yes It was to stop arcing at altitude.

[megan]

Wondering about the purpose of the antenna. Could it have been playing a role in the development of DME, which was invented by Australian James ''Gerry'' Gerrand in the 1944 - 45 period while with the CSIRO? Any ideas? When was DME put in place in Oz, I believe early 1950's?

[Wunwing]

megan.

I'm with you. There must be a reason why the 3 antenna's were only fitted to Qantas 749s and from my view DME is a good reason.

As said in an earlier post, I have a friend who was a 749 out stations engineer and I will ask him but he is away right now. I looking fwd to the answer.

[GAZIN]

The Hermes had Rebecca early on and I think these are the related antenna. This arrangement can be found on several British operated aircraft of the immediate post war period. Including Yorks, Tudors, Hastings and some BOAC Constellations. The Argonaut appears to have a similar set up to the original post, but I haven't found a good close up picture.
In Larry Milberry's excellent Wilf White propliner collection book there is a photograph of BOAC L749 G-ALAK that also appears to have the nose mounted antenna.

https://farm5.staticflickr.com/4508/37644628322_08d48d419f_z.jpg (https://flic.kr/p/ZmwytU)HP81-Rebecca (https://flic.kr/p/ZmwytU) by [url=https://www.flickr.com/photos/60717421@N06/]

[Fris B. Fairing]

GAZIN

Your Hermes setup looks similar to the Qantas Connies apart from the location of the two transmit antennae. There is another antenna under the nose of the Qantas and BOAC Connies illustrated above and I'm wondering if that precluded installing the Rebecca antennae close by. The Qantas nose location was clearly chosen by Lockheed before the aircraft were delivered in 1947. By 1954 they must have come up with a better idea although it's not clear where the transmit antennae were on BOAC's G-ANNT in 1954 (post #22).

[Wunwing]

Fris B.
If you look at your website photos of EAE and EAF which were both ex Air India 649/749s you can see that both aircraft had the similar side antenna but a small arc type nose antenna.

Earlier photos in Air India service had no antennas. So my question still is why Qantas only on the Connies at least?

I found my ex Connie engineer friend and while he remembers the antenna he cant remember what they were.
Wunwing

[Fris B. Fairing]

Wunwing

Good point. Thus it would appear that the original "nipple" type nose antenna gave way to what you call the arc antenna sometime after 1947 when the Qantas Connies were delivered and 1950/51 when Qantas acquired the two Air India aeroplanes.

[megan]

The Qantas nose location was clearly chosen by Lockheed before the aircraft were delivered in 1947EAB at Burbank prior to delivery.

http://www.aussieairliners.org/l-1049/vh-eab/1802.109.jpg