View Full Version : DME Gauges history?

1st Apr 2010, 14:26
Can anyone assist in advising the history of when DME and its related Gauges came into being plus, when they were started to be used regularly, particularly on civilian airliners?

Spooky 2
1st Apr 2010, 22:46
I'm going to make an educated guess that it was around 1965/66. A UAL DC8 was involved in a mid air over Manhattan and part of the recomendations...I think ,was the addition of DME to the civil airlines of that time.

2nd Apr 2010, 00:04
DME was invented in Australia in the 1950's - I knew one of the gentlemen that was in the group that did it - but I don't know too many more details than that sorry.

Brian Abraham
2nd Apr 2010, 01:10
The story according to wiki Distance measuring equipment - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Distance_measuring_equipment)

2nd Apr 2010, 11:38
What principle did Rebecca work on in a Vampire? IIRC it was a guage similar to a turn and slip except the needle told you left/right and the bottom gave you the distance to go. There were still a couple of Rebecca transmitters in the early sixties.

2nd Apr 2010, 12:07
A little book which was published in 1957 has the following:

"Airliners on routes to Australia, the Far East, South Africa, and South America, are fitted with radar apparatus and screens, equipment called Rebecca. On the ground is more equipment called Eureka.
Radar impulses are sent out by Rebecca, on the aircraft, and these start Eureka working. Eureka then sends back its own radar impulses, which are picked up by the 'plane, on the Rebecca screen. They are usually two letters in Morse, dots and longer dashes. Knowing the code letters of each Eureka beacon, the Radio Officer on board the airliner can identify each. On the screen there is a scale which shows the distance from the Eureka beacon. The direction of the beacon is shown by 'blips' of light which appear on the screen to the right or left of centre. If they remain in the centre, then the aircraft must be heading straight for the beacon.
The most important point about the Rebecca-Eureka system is that Eureka doesn't start to operate until a 'plane with Rebecca on board comes within range, which is usually a maximum of 120 miles. It is automatic, Eureka being 'triggered' by Rebecca. Once an aircraft is within range, Eureka must start operating."

Hmm ... didn't know it was that sophisticated.

2nd Apr 2010, 14:20
.... in November 1945 I witnessed a demonstration of an airborne distance measuring equipment (DME), built by the Combined Research Group at the U.S. Naval Research Laboratory, this time at 1000 mHz and, largely based on work that Hazeltine had been doing on the Mark V IFF, at 950-1150 mHz.

bioSHDPioneerSpeech (http://www.dodingtonfamily.org/bioshdpioneerspeech.htm)

2nd Apr 2010, 21:07
TACAN - Tactical Air Navigation was standard fit on our Vulcans as early as 1963. Did a course on it in '64 at RAF Yatesbury. TACAN comprised a rotating ground antenna, the transmitter of which responded to aircraft interrogations at 1030Mhz or 1090Mhz, can't remember which. The difference was the 60Mhz IF freq for the onboard receiver. The amplitude modulation, by virtue of the rotating antenna, provided a direction component whilst the delay timing gave the distance. The delay timing aspect was DME.

Not sure about the emergence of non-military versions, but RCA were shipping AVQ70's (DME) to the likes of Boeing by at least 1964/5. BOAC had retrofitted additional AVQ70 units to their fleet, making dual installations, by 1968. AVQ75, the GA version, was being shipping in significant numbers by 1968 as well.

Digging deep in the memory banks, but fairly certain that Gee II or III was a predecessor of TACAN. It had a circular CRT display that showed the time between interrogations and ground responses giving distance from the ground station. Triangulation on two ground stations would give you a position fix. This also operated in the "L" band frequency range, possibly also at 1030Mhz and 1090MHz. Gee II and Gee III were 1940's/50's DME kit.


3rd Apr 2010, 09:32
I don't know abou a radar screen with lots of blips. The Vampire's Rebecca looked like a homing needle with distance to go. Next time I am in Duxford I shall look in one of my old Vampires and check. Eureka rings a bell as the ground equipment. There used to be a fair number at airfield boundaries. What I do know was that the homing ariels were mounted on top of the outer wings, backwards for some reason. They used to pick up ice at the slightest pretence and spend the rest of the trip flapping and viabrating away.

henry crun
3rd Apr 2010, 21:25
alisoncc: I'm stretching my memory now but I do not think you have the description of Gee mk3 correct. To say that it was the 1950's DME gives a false impression of its capabilities.

It was displayed on a crt about 3inches in diameter, on this there were two horizontal timebases with blips produced by the various transmitting stations.
Under the display were knobs which moved the blips and the counter numbers in small adjacent windows.
When the blips were lined up one could read off the numbers displayed in the counter windows.

Then, armed with this information one consulted the Gee chart, which showed a mass of numbered parabolic lines.
The numbers from the counter windows were transferred to the lines on the chart, which gave an accurate position. Any reasonably experienced nav could provide a fix in under 30 seconds.

Accuracy did, of course drop away at longer ranges, but quite accurate approaches could be made anywhere over England.
If one was lucky enough to have a Gee line running along homebase runway it was a simple matter for the nav to guide the pilot down the line onto the runway.

4th Apr 2010, 04:40
I'm stretching my memory now but I do not think you have the description of Gee mk3 correct. To say that it was the 1950's DME gives a false impression of its capabilities.

Well I was a TACAN techie. Only vaguely remember running the Gee kit up on one occasion. I think it was for a pre-flight for a trip the aircraft was making to Woodford, and the Gee never came back. I think it looked something like this:


Which is not bad for a picture drawn from memory. :)

I always understood that Rebecca did interrogate a ground station in a like manner to a DME interrogator. Using the signal delay of the response to give distance. And Eureka the ground system had a rotating directional antenna where the amplitude modulation of transmitted responses gave a direction component. So the Rebecca/Eureka system may have actually preceeded TACAN in providing similar functionality.

I think the important aspect of all of this is that most systems evolve, rather than being revolutionary changes.

The Oberon
4th Apr 2010, 05:57
Sorry Alisoncc, but I think your picture shows a Rad Alt 6 indicator, lived above the NBS Ind. 301 at the Nav Rad station on Vulcans and Victors.

4th Apr 2010, 08:16
Win some, lose some. Told you my memory wasn't that good. I did say "I think it looked something like this". :ok:

4th Apr 2010, 10:51
I think that Gee evolved into Decca.. Similar lattice charts where accuracy deteriorated as one got further away from the transmitters. The information could be presented directly on special roller maps but the topography was distorted bordering on impossible at the edge of cover. A mainstay of the RAF SAR, North Sea Helicopters and the fishing fleet and also used in Viet Nam until the advent of GPS. At North Denes Heliport in the early days of gas exploration the single pilot used to radio his Decca readings back to the ops room and they would tell him where he was, which way to go, etc..

4th Apr 2010, 15:32
Following on from my last post.
In the early eighties we pulled S76As back from America and they went into the UK HQ hanger to be fitted out IAW the CAA Regs. When I picked them up from the docks in Antwerp, Le Harve and Southampton they had DME and another thing called Omega. I flew them to the UK and after my company engineering had finished I went down to do their UKCAA C of A.
The DME had been pulled, together with the Omega and had been replaced with Decca Tans. I could understand why Decca Tans was in, it was a company standard, but I could not understand why the DME, which was free, had been pulled. I was told that it had been taken out so that the aircraft's fit was the same as every other company S76 in the UK.
Three months later the Norwegian CAA stipulated the Decca ranges were unacceptable for range chacks in Norwegian airspace, As Norway was high on the IFR diversion list there was a frantic two weeks whilst they refitted all the DMEs thay had taken out.

4th Apr 2010, 15:51
I'm going to have agree with forget's post in which he quoted:

.... in November 1945 I witnessed a demonstration of an airborne distance measuring equipment (DME), built by the Combined Research Group at the U.S. Naval Research Laboratory, this time at 1000 mHz and, largely based on work that Hazeltine had been doing on the Mark V IFF, at 950-1150 mHz.

If you are looking for the true origin of the concept which was eventually employed as a VHF based DME capability you need look no farther than the IFF developed in WWII.

I won't get into the willie measuring of who did what first but the fact of the matter is that the operational principle/technique predated the 1950s by quite a bit. That being said, development past IFF and TACAN (a UHF based system) into a VFH capability suitable for pairing with VOR navaids was likely as described in the preceeding posts.

5th Apr 2010, 09:17
There were a couple Rebecca systems in use when I left Cosford in 1963. Rebecca 4 was just passing out, it was fitted to the station flight Annie. This used a CRT with a centre trace line where the signals were displayed as blips left and right. Once they were even you were in line and the distance down the trace gave range. This was replaced by Rebecca 8 which was a meter with left right indication and a needle to indicate range. The needle would sweep from 0 to full range when seraching for a Eureka ground station. Once it found a station it stop sweeping and indicated range. Somewhere in this mix was a short range system called BABS (Blind Approach Beacon System?).

TACAN used a 126 channel selection from about 960Mhz to 1024Mz. The two frequencies quoted ealier as 1030Mhz and 1090Mhz were used by IFF transponders, 1030 RX and 1090 Tx.

Gatwick Aviation Museum - Charlwood (http://www.gatwick-aviation-museum.co.uk)

5th Apr 2010, 11:06
This was replaced by Rebecca 8 which was a meter with left right indication and a needle to indicate range

Hooray, somebody agrees with me, I thought for a moment I was dreaming. I saw a BABS van crushed by a Halifax mainwheel wheel once at Aldergrove. The Halifax ended up in the dump as well.

SBA info pulled as to far off thread

Dick Whittingham
5th Apr 2010, 19:33

The Gee I flew with at 2ANS Thorney Is, on Vampire NF10s, was the miniaturised G Mk 3 with a 3in screen The earlier Gee was a big bit of kit. The Rebecca we carried was BABS/Rebecca with a 3in scope with a vertical range line and left and right blips on the line to give L/R info or dot/dash as it was called. The Nav had to read out the data

I don't think this was the SBA. Memory says the SBA/TBA was an mf device that gave audio dot/dsh info like a radio range

Later Rebecca in the Vampire T11 and other aircraft had a range sweeping dial that locked on when it found a ground station and a small L/R needle at the bottom

Subject always to challenge


henry crun
5th Apr 2010, 22:01
Fareastdriver: Dick is right, SBA was an earlier different type of approach aid and had no connection with Babs/Rebecca, or Gee.

5th Apr 2010, 22:25
The Vampire 11 had a Rebecca 8 set, as did the Jet Provost and Hunter. In 'range only' mode, if you were lucky it had a range of about 40 nm; in 'homing' mode about 20....

The control box was a large, clunky thing with large bakelite rotary knobs. One control selected the letter and the other the number of the associated Eureka 7 channel; for example, Cranwell was C4 and Cottesmore D5 (I think). The morse coding rate for the Eur7 was very student friendly - about 1 word per week! You had to check it as it was quite common for the Rebecca to lock onto a different station to the one you'd selected.

Somehow we flew radio navigation exercises using nothing more than Eur7 and UDF, then flew a DME let down at base using this contraption. At least we had the left/right indicator, rather than the CRT screen the guys who flew Pigs had! You went outbound in the 'DME safety lane', then faffed with L/R and the DI to establish the correct inbound approach course....:uhoh: Fortunately we'd all had several sessions in the Link trainer before trying it for real.

The 'swingometer' range needle used to hunt around the dial unless the Rebecca could sniff out a station; once I was just pulling off the target at Pembrey when the needle went clockwise at precisely the same rate as the g-meter's needle normally moved - except that it kept going...:ooh: For a moment I eased off the g as a reflex in case I was overstressing....fortunately I was already climbing. We used to pull out of the dive and immediately check the mirror for the 25 lb bomb smoke - having the distraction of the Rebecca needle moving round the dial out of the corner of your eye was most unwelcome!

The bandwidth of Eureka/Rebecca was colossal - about 4-5 MHz if I recall correctly. When the JP5A came in with VOR/DME, it seemed like the space age. This was about 1974! But the wonderful Gnat with its offset TACAN was truly magical! We had non-offset TACAN in the GT6 Hunters at Valley, but all bar 2 of the jets at Brawdy had the old Rebecca. The Mk9s had ADF, but no-one taught us how to use it - we just used to listen to music on it. A chum, Dick 'Whizzbang' was a bit of a culture vulture and had a memorable time rocketing with SNEBs at Pembrey whilst listening to 'Ride of the Valkyries' on BBC Radio 3!

The guys at 45/58 Sqns, RAF Wittering, had some NDB-to-DME approach system. If you were brave enough, you did the initial homing and inbound turn on NDB with the Rebecca turned off (as it interfered with the ADF), then turned the Rebecca on to fly the final approach. I wouldn't fancy doing that in a Cherokee, let alone a Hunter 9!

However, the DME let down was probably a lot easier than the CR DF 'Jet Instrument Approach Chart' I have dated 1954. The CR DF high level descent for RAF Merryfield had an initial overhead approach not below 12000 ft and went out on 115 degM to about 25 miles to 'half initial approach altitude plus 2000', then inbound on 285 degM with a check altitude of 3500 ft - and a min app. alt. of 1350 ft. Bearing in mind the field elevation was 145 ft, this looks like rather a useless procedure. Presumably you made the relevant calls to 'Merryfield Homer' on 104.94 Mc/s (this was long before the days of MHz) and switched to 'Merryfield Tower' on 102.42 Mc/s if you were fortunate enough to become visual!

Dan Winterland
6th Apr 2010, 04:47
That DF procedure was being used as late at 1993 in anger. At EFTS Swinderby, it was our only approach aid - and we used it in anger frequently. For CAT A and B, the range outbound was 11NM, the minima 740' IIRC and although nothing like the ease of modern approaches, we got quite good at it because we flew it quite a lot. The students used to do a limited panel QGH as part of thier IFT - with about 40 hours total time. It was quite a challenge. When I wnet to CFS and had to fly my IRT on the Chippie using such a procedure after being 'dulled down' by hours flown on the Smiths MFS, I found it very difficult!

6th Apr 2010, 11:11
BEagle mentioned Jet Provosts. JP3 below, Rebecca 8 Controller and Indicator marked. 37 and 38.


7th Apr 2010, 15:17
DME in the Hunters in 1956 was used for "Broadcast Control" interceptions when the close control frequency was jammed. For exercise purposes jamming was achieved by an open mike in the engine nacelle of a Lincoln thus making the GCI's instructions unreadable. A very high powered ground transmitter broadcast the target position. However as adjacent aircraft were still able to communicate one of a pair would tune in to a dme station eg Manston, and the other to somewhere else eg Tangmere. The lead called "Hayrake" and his wingman gave the distance. By using a cunning plotting device called the Wilson computer strapped to ones leg the two ranges could then be resolved as a fix and an intercept could be made on the estimated position of the target. It sounds simple but it finally relied on a visual intercept.

Another bit of kit fitted to Meteor F8s was Appendix which enabled homing on a jammer's transmission. Two needles crossed in the centre when you were flying directly towards or away from the target. To establish if it was higher or lower you did the first 90 degress of a slow roll and held it as long as possible when the instrument should indicate left or right, but in this case up or down. I can't remember if it was ever in Hunters.

Oh, the fun and games we day fighter pilots had in those days.

9th Jan 2013, 00:46
One of the inventors passed away recently:

James Gerrand (http://www.smh.com.au/national/obituaries/engineer-exploded-myths-in-many-fields-20130108-2cell.html)

And the airways museum has some good info:

The Australian DME System (http://www.airwaysmuseum.com/Aus%20DME%20p1.htm)

9th Jan 2013, 10:10
The first technician courses on Rebecca 8 were in June 1956.

9th Jan 2013, 19:27
Sorry markis10, but my first experience of the Australian DME "System" was in 1970 flying out of Archer Field, and I thought it was absolute rubbish. It really was a joke. The rest of the world had gone digital, whilst the DCA were extolling the virtues of "VHS tape". :=