'The Silent Approach'?

Hi all,

I've been reading the Wikipedia article for the bombing of Barcelona during the Spanish civil war. Italian bombers took off from Majorca and could bomb the city with relative impunity as it had no AA or fighter defence. According to the wiki article, a British journalist based in Barcelona at the time claimed that the bombers adopted a silent approach:

"Later in the year, the British journalist John Langdon-Davies - who had been present in Barcelona at the time - published an account of the attacks. He reported that the bombers had glided in at high altitude to avoid being detected by the (pre-radar) acoustic aircraft detection means available, and only restarted their engines after releasing their bomb loads, which he termed the "silent approach" method. The effect of this was that the aircraft were not detected and the alert sounded until after their bombs had exploded on target."

Has anyone ever heard of WW2 era bombers deliberately turning off their engines during a sortie? My gut feeling is that this journalist must be mistaken and due to the technology of the time you would never deliberately cut out an engine over hostile territory as you might not be able to restart it in flight? Be interested to hear others thought's on this.

Browning303 said:

Hi all,

I've been reading the Wikipedia article for the bombing of Barcelona during the Spanish civil war. Italian bombers took off from Majorca and could bomb the city with relative impunity as it had no AA or fighter defence. According to the wiki article, a British journalist based in Barcelona at the time claimed that the bombers adopted a silent approach:

"Later in the year, the British journalist John Langdon-Davies - who had been present in Barcelona at the time - published an account of the attacks. He reported that the bombers had glided in at high altitude to avoid being detected by the (pre-radar) acoustic aircraft detection means available, and only restarted their engines after releasing their bomb loads, which he termed the "silent approach" method. The effect of this was that the aircraft were not detected and the alert sounded until after their bombs had exploded on target."

Has anyone ever heard of WW2 era bombers deliberately turning off their engines during a sortie? My gut feeling is that this journalist must be mistaken and due to the technology of the time you would never deliberately cut out an engine over hostile territory as you might not be able to restart it in flight? Be interested to hear others thought's on this.

Click to expand...

Agree - now they could have throttled back to idle to reduce noise, I think that makes more sense.

I think also that is highly doubtfull that the italian bombers cut their engines to make a silent aproach, much more likely what FLYBOYJ say. I have a couple of books about the bombardement of the republican east coast in the SCW, but don't remember anything about. Will try to search for them (first) and find anything about gliding attacks.

An aircraft's engine when at idle can be remarkably quiet and if it's coming toward you, the Doppler Effect helps muffle any sound even further.

This may have caused the author to believe that the engines were shut off, because it was their quiet idle approach and then the roar of the engines as they were throttling up to pull out/away from the target that may have confused him.

It is only Wiki, in fact Barcelona had both AA and fighter defence and if one had arranged sound locators there why not also some ways to utilize the info they produced, i.e. AA guns and fighters.

This is an acoustic aircraft detection device. In World War 2, before radar was developed, these devices were used to detect approaching enemy aircraft by listening for the sound of their engines. It consists of 4 acoustic horns, a horizontal pair and a vertical pair, connected by rubber tubes to stethoscope type earphones worn by the two technicians left and right. The stereo earphones enabled one technician to determine the direction and the other the elevation of the aircraft.

The weather conditions could be having an effect on the observation. If the prevailing winds at the bombers altitude is away from the observer it could appear to be a silent approach.

Snautzer01 said:

This is an acoustic aircraft detection device. In World War 2, before radar was developed, these devices were used to detect approaching enemy aircraft by listening for the sound of their engines. It consists of 4 acoustic horns, a horizontal pair and a vertical pair, connected by rubber tubes to stethoscope type earphones worn by the two technicians left and right. The stereo earphones enabled one technician to determine the direction and the other the elevation of the aircraft.

View attachment 591390

Click to expand...

Anyone who has the chance to visit the Denge sound mirrors near Dungeness Kent should take the opportunity. A very eerie place.

Denge Sound mirrors

I cannot say regarding Barcelona.

I have been reading the excellent/fascinating/well-researched book "Avro Manchester: The Legend Behind the Lancaster" by Robert Kirby (2015).

On page 118, a silent approach/attack is described that occurred on 8 April 1941. While attacking Kiel, Germany, W 'Mike' Lewis flying Manchester L7309 pulled power to idle and dove from 15,000 ft, releasing bombs at 9,000 ft, and continued to the deck. It was a tactic that Lewis had practiced, but this was the first real test. The aircraft was lit-up by searchlights and took hits from flak during the dive.

On page 153, the book describes that the British Anti-Aircraft Command had become concerned that German aircraft could be evading detection by shutting-down their engines, feathering their propellers, and gliding to their targets. Manchester Squadron 207 was tasked to undertake a series of silent attacks on Nottingham to test the effectiveness of the tactic. On 4 June 1941, Peter R. Burton-Gyles using Manchester L7377 conducted the first attack. The profile was to initiate a dive from 19,000–18,000 ft upwind of the target with engines stopped and propellers feathered. "Bomb release," which involved dropping a photoflash, was around 12,000 ft, and the aircraft would continue to glide some ways from the target before restarting the engines at 6,000 ft. Of course, one of the Vulture engines refused to restart. The tests were continued to 12 June, and it appears that other aircraft and crews were involved, with Mike Lewis being one. It does not appear the tactic was developed further.

It should be noted that, at the time, neither the Manchester's engines nor its propellers were reliable. The engine may not restart, and if it did, it could also fail. The propellers may not feather, and if they did, they may not unfeather.

WJPearce said:

I cannot say regarding Barcelona.

I have been reading the excellent/fascinating/well-researched book "Avro Manchester: The Legend Behind the Lancaster" by Robert Kirby (2015).

On page 118, a silent approach/attack is described that occurred on 8 April 1941. While attacking Kiel, Germany, W 'Mike' Lewis flying Manchester L7309 pulled power to idle and dove from 15,000 ft, releasing bombs at 9,000 ft, and continued to the deck. It was a tactic that Lewis had practiced, but this was the first real test. The aircraft was lit-up by searchlights and took hits from flak during the dive.

On page 153, the book describes that the British Anti-Aircraft Command had become concerned that German aircraft could be evading detection by shutting-down their engines, feathering their propellers, and gliding to their targets. Manchester Squadron 207 was tasked to undertake a series of silent attacks on Nottingham to test the effectiveness of the tactic. On 4 June 1941, Peter R. Burton-Gyles using Manchester L7377 conducted the first attack. The profile was to initiate a dive from 19,000–18,000 ft upwind of the target with engines stopped and propellers feathered. "Bomb release," which involved dropping a photoflash, was around 12,000 ft, and the aircraft would continue to glide some ways from the target before restarting the engines at 6,000 ft. Of course, one of the Vulture engines refused to restart. The tests were continued to 12 June, and it appears that other aircraft and crews were involved, with Mike Lewis being one. It does not appear the tactic was developed further.

It should be noted that, at the time, neither the Manchester's engines nor its propellers were reliable. The engine may not restart, and if it did, it could also fail. The propellers may not feather, and if they did, they may not unfeather.

Click to expand...

Thanks for sharing that, very interesting and informative.

Diving while attacking has some advantages apart from being a "silent approach" it increases your speed through flack and makes it difficult for gunners to get the correct altitude.

Some experienced pilots of U-2(Po-2) biplane night bombers throttled down engines before to drop bombs. In some books/articles, it is called "shutting down" erroneously.

Dimlee said:

Some experienced pilots of U-2(Po-2) biplane night bombers throttled down engines before to drop bombs. In some books/articles, it is called "shutting down" erroneously.

Click to expand...

Just noticed this Dimlee. Maybe just a miss understanding of terms or translations. Shutting down or closing the throttles on an engine took it to minimum revs or "tick over" it didn't shut down the engine itself.

Browning303 said:

Hi all,

I've been reading the Wikipedia article for the bombing of Barcelona during the Spanish civil war. Italian bombers took off from Majorca and could bomb the city with relative impunity as it had no AA or fighter defence. According to the wiki article, a British journalist based in Barcelona at the time claimed that the bombers adopted a silent approach:

"Later in the year, the British journalist John Langdon-Davies - who had been present in Barcelona at the time - published an account of the attacks. He reported that the bombers had glided in at high altitude to avoid being detected by the (pre-radar) acoustic aircraft detection means available, and only restarted their engines after releasing their bomb loads, which he termed the "silent approach" method. The effect of this was that the aircraft were not detected and the alert sounded until after their bombs had exploded on target."

Has anyone ever heard of WW2 era bombers deliberately turning off their engines during a sortie? My gut feeling is that this journalist must be mistaken and due to the technology of the time you would never deliberately cut out an engine over hostile territory as you might not be able to restart it in flight? Be interested to hear others thought's on this.

Click to expand...

At last I had been able to look at my books about the bombing of the spanish mediterranean coast during the civil war.

Those attacks reported by Langdon-Davies were concentrated in 3 days in March, with few aircraft each time but several attacks in each day. Reportedly, the aim was mostly to create a panic state in the Coty, albeit in one attack a single bomba hit a lorry loaded with explosives and the subsequent detonation made a great carnage and damage.

Nowhere did it mention that these attacks were made with the engines cut or by a gliding approach, except in the excerpt of the Langdon-Davies book itself (silent approach), but it seems to point that the first attacks were that way but not the last ones.

This would had been very stupid by the italian airmen because half of the attacks were made during daylight, exposing the attackers more time to AA fire and fighter interception, when the italian after action reports quoted in the books usually regarded the AA fire in Barcelona as "intense" and when they used Savioa SM.79 in daylight attacks and SM.81 during the night (as the lower insert square from italian sources day).

In the two books there is only one reference to an attack that could fit in the engines with low revolutions settings with the intent to make a surprise raid, in this case a night attack on the 8 of June 1938 to the Alicante airdrome, quoting "a motori ridotti", presumably from an italian after action report and meaning "with reduced engines".

It could be posible that the italian airmen in the Balearic Islands made attacks with low power settings trying to achive surprise in some attacks but not against a city as defended as Barcelona.

The explanations given by the other members seems much more probable, even that the proper city noise (specially during the day) muted the aproaching planes.

PS: Both pages come from vol 2, the one with the silver front.

.

I have hazy recollections about He 59 float planes attacking Barcelona harbour at nights with engines throttled down during the approach. But my SCW interest was in 70s and early 80s and I gave away most of my notes on the subject in late 90s.

I'm not sure a journalist has the keenest eye -- or ear -- for tactical air attacks. Nor do I think pilots in that era would willfully shut down an engine. Throttling back does reduce noise sig, and that's probably where there journalist went wrong.

Juha3 said:

I have hazy recollections about He 59 float planes attacking Barcelona harbour at nights with engines throttled down during the approach. But my SCW interest was in 70s and early 80s and I gave away most of my notes on the subject in late 90s.

Click to expand...

Hi J Juha3

In those books the main focus (specially in vol. 2) are the attacks made by the italian airmen in the Balearic Islands, with some attacks recorded by the Legión Cóndor and other by the Republican Air Force, none be said abour the He 59s of the AS/88.

In other book about the use of float and seaplanes in the Spanish Civil War, many attacks are credited to the germans in the He 59s (at times using the low revs gliding attack), but in some cases those actions seems at conflict with the other book.

As an example, in the night from November 1st to 2nd (1938), both books recorded that a plane was shot down by AA fire, crashing in Santa Cristina de Aro, with the crew been taken POW with one man slightly wounded.

But they differ in the plane shot down. The float and seaplane book simply said that a Heinkel was shot down with the crew POW, while the one about the bombing of the spanish eastern coast says that plane was a S-81 from the 251ª Escuadrilla, crewed by Angelo Martinoni, Luigi Trois, Luigi Bruno, Pierfranco Saltarelli, Aldo Bonapera and Zeno Carfagna (as quoted from a republican after action report). So much more data in the second book.

In another example, the book about the bombing of the spanish eastern coast says that during the day, on September 13rd 1938, 5 S.79 attacked Barcelona harbour, hitting 4 steamers and one floatting dock, with big explosions and fires, a republican report confirming the sinking of the floating dock.

The book about the float and seaplanes says that 5 He 59 attacked Barcelona harbour in the night 14/15 September 1938 and, guess what?, they leave 4 merchant ships on fire, one floating dock sunk and harbour instalations on fire.

Myself feel inclined to give more trust to the book about the bombing of the spanish eastern coast because is more detailed, seems to cross check with republican sources, had a detailed bibliography and was published in 1998, after the author made a very deep revision of one book he wrote in the mid 70s.

The book about the float and seaplanes was first published in 1987, with a second expanded edition (the one I have) in 1991 and lack references or bibliography, so it is possible that this one is based in some way in the original 70s book. But also this book gave account of some attacks that the other book failed to aknowledge, so it is possible that neither is complete or that the original spanish were incompleted or mixed, which could be since both the Legión Cóndor and the italian units had a free hand in conducting operations.

I´m looking forward to look at my copy of The Legion Condor: A history of Luftwaffe in the Spanish Civil War 1936-1939 by Karl Ries and Hans Ring to try to solve some of the differences, tomorrow or on Sunday, wife, daughter and home duties allowing.

Hello Escuadrilla Azul
thanks a lot for the info. My source was probably a book on Legion Condor published in 70s, so probably not necessarily very reliable source.

A good book in English to begin learning on Italian bombing operations during the Spanish Civil War is IMHO Marco Mattioli's SAVOIA-MARCHETTI S.79 SPARVIERO BOMBER UNITS. (Combat Aircraft Book 122)
My short review of it can be find here:
Marco Mattioli's SAVOIA-MARCHETTI S.79 SPARVIERO BOMBER UNITS. (Combat Aircraft Book 122)

Juha3 said:

A good book in English to begin learning on Italian bombing operations during the Spanish Civil War is IMHO Marco Mattioli's SAVOIA-MARCHETTI S.79 SPARVIERO BOMBER UNITS. (Combat Aircraft Book 122)
My short review of it can be find here:
Marco Mattioli's SAVOIA-MARCHETTI S.79 SPARVIERO BOMBER UNITS. (Combat Aircraft Book 122)

Click to expand...

Thanks for the remainder. I searched a copy of this book and it failed to notice the attack on September 13th 1938.

BTW, the Mattioli book and the one about the bombing of the spanish eastern coast by Infiesta differs in some details of the attacks, either in the location (on May 30th 1938 one ship was set on fire, in Barcelona by Mattioli or in Valencia by Infiesta and other sources) or in the day (the reprisal on the republican naval base of Cartagena was either on March 6th 1938 by Mattioli or in March 7th by Infiesta) or in the comanding officer of the attacking force (a bombing of the Valencia harbour at 09:45-09:50 on June 6 was either led by Zigiotti as by Infiesta or by De Prato as by Mattioli, albeit Infiesta claims that a second attack half an hour latter was indeed lead by De Parto). In your review of the Mattioli´s book, you express some doubt as if the republican battleship Jaime I arrived at Cartagena under tow (Mattioli) or by its own power (Wiki). Infiesta says that the battleship arrived to Cartagena by itself.

And so they go for other examples, altough I haven´t searched all the claims.

As usual, the SCW gets murky.

As for the color profiles, the profile 2 in Mattioli as a different colour for the dark band (brown in Mattioli and green in Infiesta) and a different shape and colour for the number 5 (red in Mattioli and white in Infiesta). In Ali d´Italia 9 S.79 by Cesare Gori, the front cover support your
appreciation that the the 3 tone band camo can only be seen from certain views. In this, the two tone in the fuselage are green in the front and rear and light brown-sand in the middle and green at the wing roots and dark brown from the engine nacelles outward. On pages 20 and 21 are two photos of this aircraft (from the same side) and in one the number 5 looks like in a dark colour and in the other is clearly a light colour (almost surely white). Oddly, in the photo of the dark number 5, there are two aircraft with the number 3, so it is possible that there were aircraft with repeated numbers, perhaps trying tp diminish the number of aircraft involved and, therefore, the italian support for Franco.

The aircraft in Mattioli profile 11 (28-14) is also represented in Infiesta. The colours are more or least the same but they differ in the engine cowlings, light grey in Mattioli, light brown in Infiesta. In Ali d´Italia is a photo of this aircraft also (page 19) and the engine cowlings are clearly of a light colour. To me looks like the same underside light grey but I´m not able to discern if they are or not.

Tomorrow will try to post the said colour profiles and photos.