B-17G IFR instrumentation in 1944/45

[Ken]

Had a nice chat with Grandpa Jim over the holiday weekend at my wife's family get-together. Jim was an aircraft commander in the 401st BG flying the B-17G at the end of the war.

We talked alot about IFR flying then and today. He has a vivid memory of a demonstration pilot coming out to show him the "new" ILS equipment, although Jim has no recollection of them ever using it other than the demo. He thinks the demo was done at his home airfield in England. He also talked about the A-N Radio Range, but says that he can't remember ever seeing it used in Europe.

What he does remember is flying a needle (like an ADF) and descending until free of the clouds and then navigating chimney to chimney back to land at his base.

Jim went on to fly a number of years in the postwar AF and admits that he may be getting his navaids confused with later systems. Does anyone have any hi-res instrument panel shots of a 1944-45 B-17 cockpit so we can confirm exactly what was installed at the time? I suspect Jim would love to see the photos as well to help sort out his memories of that time.

Thanks,
Ken

[RAMC181]

The 401st's home base at Deenethorpe was originally equipped with the RAF SBA (Standard Beam Approach) system, the group's aircraft had the redundant RC-43 Marker Beacon Receiver units adapted for use with SBA.

Sometime after mid-1944 the AAF SCS-51 Instrument Landing System was installed at Deenethorpe.
B-17's with the aircraft part of the system, originally titled RC-103, later renamed the AN/ARN-5, had a distinctive "bull-horn" antenna fitted on the nose, as arrowed below:



Signals from this antenna were fed to the B-733 receiver set, and were displayed to the pilot on a crossing-needle dial on the instrument panel.

The dial can be seen clearly at the following link: http://b17panels.com/images/Littleton/littleton-1.jpg

It's the one above the pilot's wheel, with the blue and yellow segments beneath the "crosshairs".

Hope that helps,
Paul

Last edited by RAMC181 on Tue Jul 07, 2009 9:54 am, edited 1 time in total.

[Ken]

Thanks for the kind reply. The blue and yellow segments are of interest. Even today, the localizer "feather" is shaded half blue and half unshaded. The blue half is on the right, though. When flying a back course approach it is on the left ... some of the old timers would call a back course a "blue left localizer". Wonder why it's on the left in this example.

PS: I think I can just make out the ADF tail on the compass locator card in the extreme left of the photo.

[Second Air Force]

There is a nice article on the SCS-51 system here: http://www.flightglobal.com/pdfarchive/ ... 02170.html

Here are a couple of photos of the ground installation of the Glide Path System that was installed at Fairmont Army Air Field. This system was installed during the B-29 Phase Training effort. First is two views of the shack and antenna array:



And this is the equipment installed in the shack:


Scott

[TonyM]

There is a nice article on the SCS-51 system here: http://www.flightglobal.com/pdfarchive/ ... 02170.html

Here are a couple of photos of the ground installation of the Glide Path System that was installed at Fairmont Army Air Field. This system was installed during the B-29 Phase Training effort. First is two views of the shack and antenna array:



And this is the equipment installed in the shack:


Scott

Scott,

Great Photos! Thanks for posting.

That wheel hub on the radio trailer looks like a great shin killer for the unwary.


TonyM.

[Second Air Force]

Imagine how loud that shack got with the putt-putt running! OSHA would not be impressed with 1940's ingenuity. Also, notice that there is what looks like a larger generator set parked next to the shack. I'm wondering if the transmitter wasn't powered by the external unit and the trailer mounted one was used as a backup.

There was an interesting incident that involved this glide slope transmitter. A 16th Bomb Group B-29B, 42-63613, got off the localizer and hit a good sized tree during an approach. They got the airplane down safely (off-field landing) without further damage, but the tree tore her up pretty good. I've got several photos of the damage somewhere and the incident report.

Scott

[Ken]

Anyone else with a period photo of the B-17 panel or more knowledge of the introduction of ILS ... or who knows why/if the A-N Range was not used in theatre?

[Second Air Force]

I'm still digging, Ken. I'd swear I have a reference that speaks to navaids used by the 8th.

Scott

[RAMC181]

From the late Roger Freeman's "Mighty Eighth War Manual":

...the SCS-51 initial programme announced on 20th June 1944 concerned installations at 16 airfields:
Bovingdon
Harrington
Chelveston
Cluntoe
Seething
Deopham Green
Wendling
Framlingham
Bassingbourn
Thurleigh
Ridgewell
Deenethorpe
Thorpe Abbots
Bury St Edmunds
Burtonwood
Warton

Later Cluntoe was eliminated and Attlebridge scheduled instead of Deopham Green. It was intended that eventually all bomber stations would have the system but by the end of 1944 only ten ground installations were in place and the original schedule was not met until March 1945.

From early December 1944 8th Air Force maintained a detachment on the Continent equipped with the ground element of SCS-51 for the purpose of marking the front line to ensure positive identification of friendly troops.

All the best,
PB

[B-17 Buff]

Very interesting topic and one I was thinking about again the other day having never really looked into it in depth... I have never been quite sure of the capabilities of the equipment at the time? I understood they used basic ADF equipment but was the ILS equipment used as we use it today for precision approaches? I was under the impression ILS as we know it wasnt really used until the 1950's? Were those beam bar yellow/ blue 'OBS' instruments fitted at the time? DME? For that matter how similar was the ADF/NDB equipment?? Surely they didnt fly holds and non precision approaches quite the same as we do today either? Though in the UK we dont fly ILS back courses unlike you guys and still use NDB's everywhere instead of VOR's or GPS just to make our lifes difficult!!

[Ken]

Podcast on avweb.com in Jim's own words ...

http://www.avweb.com/blogs/insider/AvWe ... ml?type=pf

[Forgotten Field]

Reference Wikipedia's description of the AN/MRN-1
http://en.wikipedia.org/wiki/AN/MRN-1

The aircraft was equipped with the RC-103 radio receiver. The glide path indicator is just like the ones used in modern aircraft (well, modern as in from 1970's) and is shown on the wikipedia page. There were two things the pilot had to use in the cockpit with this system- the indicator, I-101
http://en.wikipedia.org/wiki/File:I-101_Indicator.jpg
The BC 732 frequency selector:
http://www.bwgsurplus.com/catalog/images/bc732.jpg

This system shows up in early 1944 AAF Pilot's Information Files, but I'm sure they trained on it before that time. This system was widely fielded starting in mid-1944. This was the same system used during the Berlin Airlift, with some component updates.

[Taigh Ramey]

For what it is worth the system used in WWII is still operable today in that it was a VHF system that used two receivers one for a localizer and one for glide path. The frequencies used for glide path then are about the same today. Back then you would select seperate You can use the original WWII antenna system for VOR and Glideslope with modern radios. In the antenna on the B-17 pictured above the aft pointing U shape is for localizer and can be used for VOR and the two lateral ones are for the glide slope. From what I understand (no supporting documentation to prove it) there was a blanking issue with the early straight back localizer antenna so they bent the rods slightly outboard for better reception.

The first systems seemed to have separate antennas for glide slope and localizer. The next had the one that was pictured above on the B-17 and then the latest style had the angled localizer rods.

Here is a crude inventory photo of the the antennas in our collection. You can see the early OD green ones without the glide slope on the front. Its hard to see but behind the green antennas is a stand alone glide slope antenna that was used in conjunction with the green one if needed. The three silver antennas across the bottom are the combined antennas with the one on the lower left being an early example. Sorry I don't have the antenna designations handy. As I recall one of the later war/just post war systems was AS-27/ARN-5 but don't quote me. In the upper left is the mostly post war antenna that has the angled localizer/VOR rods.

[seanbart]

The localizer receiver system was the RC-103 using the BC-733 receiver with BC-732 control box and I-101 indicator. The glide slope receiver system was the AN/ARN-5 that used the R-47, R-57, or more common R-89 receiver. The R-89 also used the BC-732 to select the glide slope channel that corresponded to the localizer channel and the I-101 indicator. The RC-103 system used the localizer alone antenna AN-100. The earlier combined localizer and glide slope antenna is indeed the AS-27/ARN-5. The glide slope alone is the AS-61/ARN-5. I wonder if those antennas with the bent elements are the AS-580/ARN-30?

I have been collecting all of the components for a combined RC-103 and AN/ARN-5 system for a couple of years. I have everything except for the receiver and control box mounts. One of these days I'll put it all together and try to get it working with some sort of signal simulator.

[The Inspector]

Didn't the Luftwaffe use A /N as their bomber directional beam? which could have beeen used to distract or misguide allied aircraft?