Landing Navigation Aids in bad weather in England during USAF ops WW2.

[Centaurus]

USAF 8th Air Force. During WW2, the USAF operated B17's , Liberators and a host of other types over Europe. English weather being what it was in winter especially, I have often wondered what navigation aids were used by the crews when landing back in England in poor visibility including fog. Was GCA available in those days? The British used the Beam Approach for blind landings although I think that was post war. Did the USAF aircraft use an equivalent of the ILS and to what cloud base and visibility minima could the approach be safely made?

[K.Whyjelly]

From August 1942 the 8AF used the RAF Lorenz blind landing system, usually called SBA (Standard Beam Approach). This was an audio-visual system, having a pair of ground markers, one at the end of the runway in use and the other a couple of miles away on the approach line. The redundant RC-43 Marker Beacon (with it's antenna underneath the fuselage of the B-17, just forward of the tailwheel) was usually used as the receiver.

This was replaced in service by the US SCS-51 Instrument Landing System from mid-1944.
The aircraft component of the system was the RC-103, later redesignated the AN/ARN-5, with the distinctive horned antenna on the nose as seen below.



The glide path was indicated to the pilot via an instrument with two moving needles to show the aircraft's relative position:



The receiver unit for the ARN-5 system was the BC-733:

Radio Receiving Set, BC-733.
JAN Type: BC-733
Nomenclature: Radio Receiving Set
Components: BC-733 Radio Receiver, DM-53 Dynamotor
Weight: 20 Lbs
Size: 13-3/16" x 7" x 4-13/16"
Frequency Range: 108.3-110.3 MHz
Power Input: 12/24 VDC
Number of Channels: 6 Crystal-Controlled Channels - 108.3, 108.7, 109.1, 109.5, 109.9, 110.3 MHz
Channel Spacing: 400 kHz
Part of: BC-733
Description: Radio Receiving Set BC-733 receives localizer signals in 110 MHz
range and displays the aircraft position relative to the glideslope on a crossed-needle meter display.
Valves: 3 x 717A, 12AH7, 2 x 12SR7, 2 x 12SG7, 12SQ7, 12A6

FIDO was also utilised

[safetypee]

Extract from The Journal of Navigation, May 89. Presidential address by Sir John Charnley.
“… the work started in the USA on what was to become the Signal Corps System 51 (SCS51) a short-range radio approach and landing aid operating in the VHF/UHF band, the forerunner of the current Instrument Landing System (ILS).
Because of the concern of the USAF about the restrictions on their bombing operations caused by the European weather, an early model of the SCS 51 was brought to England in 1944 by Major Francis Moseley USAF. Successful demonstrations of blind approaches made to the 8th USAF and British scientists using a pilot interpreted, cross pointer, zero reader instrument in a Liberator aircraft were quickly followed by the building of experimental models of approach couplers, the modification of automatic pilots, and the first use of a mechanical differential analyser to simulate and investigate the interaction of the various elements of an automatic approach system.
In January 1945 automatic approaches were demonstrated in a Boeing 2470 aircraft and a few days later the first automatic blind landing of a large aircraft was made to a runway in complete darkness, any surrounding lights being completely obscured by the enforced ‘black out' of the war.
Immediate interest was generated in the possibility of military operations in worse weather than was then possible and later that year a multi-disciplinary team, the Blind Landing Experimental Unit (BLEU) was formed in the UK containing specialists in the fields of radio guidance, automatic control and aerodynamics to address the interdependent' system' problems. The end of the Second World War was in sight so with commendable foresight the terms of reference of the unit included the development of blind approach and landing aids for civil aircraft as well as military.”

[bvcu]

dont know the details of equipment or dates but pretty sure 'beam approach' was in large scale use by mid war with RAF. Large amount of training flts mainly equipped with oxfords for training crews so would imagine that the USAF would possibly have been using similar equipment if it was in widespread use. Hopefully someone with more knowledge will post !!

[henry crun]

Bee Beamont talks of doing what he called a ground controlled approach to a Fido runway at when he was diverted to Bradwell Bay in 1943.

Presumably that service would have been available to the 8th Air Force if necessary.

[Centaurus]

Thank you all very much indeed for your replies. A fascinating history of bad vis instrument approaches.
Cent.

[old,not bold]

FWIW, the RAF were running Beam Approach courses in 1943, as evidenced by the following page from 1943 in my father's logbook....he had just returned from instructing ab initio pilots in what was Rhodesia and was being brought up to operational speed again...by October he had converted to Wellingtons, then Lancaster III, flown 7.5 operational trips, and was a guest in Stalag Luft III (Belaria).

[4Greens]

They also had FIDO at the master aerodromes. Cant remember the mnemonic but it was a lot of flame either side of the runway and cleared fog. Someone may elucidate.

[spekesoftly]

FIDO

'Fog Intensive Dispersal Of' or 'Fog Investigation and Dispersal Operation'.

[midnight retired]

FIDO

The FIDO system was to become installed at 15 British airfields enabling both RAF and USAAF Commands to operate in what otherwise would have been below minima conditions. It was particularly useful during the Ardennes offensive in the winter of 1944, which occurred during a particularly bad period of intensive fog lying over both Europe and the UK, however the availability of the UK FIDO system enabled over 1000 Allied aircraft to attack the target and return safely.
What the Americans crews made of this typically British Heath Robinson invention I hate to imagine, it is a pity that it wasn't further developed, like the Standard Beam Approach, for the benefit of modern Airliners. Although Health and Safety might have frowned on that one !!

[bushy]

There was a thing called a BABS WAGGON, which consisted of a light English panel van full of electronics and with a rear section that opened up and became a directional antennae. It had a small engine powered generator to provide power so it was totally independent of ground facilities. It could simply be parked at the end of a runway and provide the "beam."

[Fareastdriver]

There was a thing called a BABS WAGGON,

There was one at Aldergrove until about 1950 when it was crushed by a Halifax mainwheel. The Halifax was written off as well.

[shack]

Babs Waggon

I remember carrying out Eureka/Babs approaches at Aldergrove in the mid-late 50s. Happy days on 120.

[Tee Emm]

Back in the early fifties on Lincolns we did Lucero instrument approaches. The navigator operated a Cathode Ray thingie which showed little fuzzy looking signals each side of a base line. Depending on the angle in azimuth of the approach, one signal would get shorter than the other so you turned a few degrees away from the short signal and when both "wings" of the signal were equal length you were tracking to the station. There were no instrument approach charts for Lucero so you were responsible for your own terrain clearance. Pretty shaky stuff if there was significant terrain around. It was like a poor mans DME I guess. We did a lot of practice at Darwin in Australia where it was flat apart from the snouts of the big crocs watching carefully from the mangrove swamps near the airfield...

[Double Zero]

Sometimes even elf 'n safety seem a good idea...

In the words of the Goons, so long as you've got your elf !

DZ

[Shackman]

For further information about the early days of GCA approaches try Arthur C Clarke's "Glide Path". Describes his time at (IIRC) St Mawgan at the latter end of the war developing/improving the first radar talkdowns.

[Juan Tugoh]

The late Group Captain Frank C Griffiths DFC AFC, was involved in the development of Blind Landings during the war, and describes much about the systems and how they were tested in his book "Angel Visits" which is worth a read. His other book "Winged Hours" describes his tour as an SOE pilot on 138 Sqn at Tempsford, including his mission where he was shot down and his subsequent escape along the evasion lines back to the UK.

One detail of the early ILS testing was that they had a Boeing B247D, the only one in Europe at the time. It was flapless and had a very low approach angle which allowed it to land without 'flare out'. In testing they found that the Boeing was very placid and reliable and could land automatically under most conditions. One human aspect of this was that none of the pilots who flew the Boeing could let it land automatically at night without lights - they all switched the lights on at 100 feet or so above the ground.

[Tee Emm]

It could simply be parked at the end of a runway and provide the "beam."

Hopefully the truck was parked in the correct geographical position otherwise a real problem would occur if the beam was off-centre, so to speak..

This happened on a few occasions at Christmas Island (Kirimati) in the South Pacific south of Honolulu. A portable NDB was set up at the airfield to cater for incoming RAF aircraft during the period when Atomic bomb tests were being conducted. The NDB and associated gear was actually on the back of a truck and the driver knew the spot where to set up the NDB. Some weeks later aircraft homing on the NDB got overhead signals Ok but on breaking cloud when the weather was typical tropical rain they were unable to initially locate the airfield which in fact was now about 15 miles away from where the truck was at the time.

Investigation of these incidents found that the truckdriver - a Kirimati local man who had been trained to turn on the NDB and associated petrol motor that ran the generator - one day couldn't be bothered to drive all the way to the airport to set up the NDB as it seemed to work just as well from his village on the other side of the island. Fortunately Christmas Island was flat and no obstacles...

[Iron City]

Instrument Landing System

The ILS as we know it today was developed by the CAA experimental unit in Indianapolis in the 1930s. the VHF localizer and UHF glide slope with marker beacons for along track position was experimented with as was a microwave system (no not that microwave landing system (MLS)) by the Lincoln Laboratory. Problem with that was it needed a klystron to produce the microwaves and they were too valuable to be used for just that (radar and stuff) ILS was standardized on by the CAA and War Department (Had to go all the way to Roosevelt for the signoff)

AN/SCN-51 was the ILS built for the military fitted in a van with numerous copies placed all over the world. A Boeing 247D was used by United Airlines for a lot of the test work in California and other parts of the U.S, may be that airplane that was sent to the UK for an early 1940s version of flight inspection. There is a B-247D in the Smithsonian (Downtown, not Udvar Hazy) painted in United colors that is the ex CAA test airplane that I am told is still full of the flight check equipment for ILS. This airplane may be the ex United airplane.

Good published references are "Blind Landings" by Eric Conroy Johns Hopkins University Press and "Instrument Landing Scrapbook" by Chester Watts Trafford Press. Watts was one of the designers of antennas and other ILS equipment and was in the UK during the war to install, check, and get the systems working and since is a builder of slotted waveguide ILS antennas (anyone heard of end fire glide slope?)

[Mycroft]

In a non-internal method some searchlight intstallations had intructions to assist lost aircraft by illuminating a vertical beam and then pointing towards an airfield. I presume there were sufficient safeguards to prevent the assistance of Germen intruder a/c.