'Spitfire Paddy' on now
Discussion
|https://thumbsnap.com/g9n4ECkn[/url]Eric Mc said:
What channel is that?
And will it be viewable on a watch gain platform?
Morning Eric. Freeview 84 is PBS America. Some quite interesting stuff on that channel.And will it be viewable on a watch gain platform?
I presume it's already been shown elsewhere before so is probably available to stream somewhere if you hunt. It was a good no-frills documentary about a great but relatively unknown fighter pilot. W/Cdr at 21 and dead before 22 - but like many over-worked aces you could tell the net was closing as he became tired.
The only bit that put my amber light on was when an interviewee said that German bombers sounded different from British ones because they had diesel engines as opposed to in-line ones. I'm sure that's what he said. IIRC German bombers sounded different because their engines weren't synched.
Simpo Two said:
The only bit that put my amber light on was when an interviewee said that German bombers sounded different from British ones because they had diesel engines as opposed to in-line ones. I'm sure that's what he said. IIRC German bombers sounded different because their engines weren't synched.
You can have in-line diesel engines, V12 diesel engines or pretty much anything in-between. I’m confused by the comparison of a fuel type with an engine configuration.Whatever the cause, German bombers did apparently have a distinctive sound, my Mum mentions it whenever the topic ‘Being Bombed’ comes up. In fact it’s what saved her life, her uncle home on leave recognising the sound and ushering the children to safety. Sadly he didn’t make it in time.
Eric Mc said:
As already mentioned, I've always understood that it was due to the throbbing sound the engines made as the Luftwaffe did not normally try to synchonise the RPM levels on their multi-engine aircraft. It's a form of audio resonance effect.
I have a memory that they deliberately desynched them in order to confuse sound detection equipment.Whilst diesel aero-engines did exist they were a tiny minority and irrelevant; the interviewee was perhaps thinking of E-Boats, which were very sensibly diesel-powered.
Simpo Two said:
Eric Mc said:
As already mentioned, I've always understood that it was due to the throbbing sound the engines made as the Luftwaffe did not normally try to synchonise the RPM levels on their multi-engine aircraft. It's a form of audio resonance effect.
I have a memory that they deliberately desynched them in order to confuse sound detection equipment.It was pretty uncomfortable for the flying crews by all accounts, flying in a twin with un-synched props is not pleasant.
I remember my Grandparents talking about the horrible sound it made.....they lived only a few miles east of RAF Northolt during the BofB and Blitz, and my Grandfather was a fire-watcher.
aeropilot said:
I've heard RAF Wellington and Hampden crews did the same thing when they did their early night raids over Germany and the Low Countries in 1940-41 as well.
It was pretty uncomfortable for the flying crews by all accounts, flying in a twin with un-synched props is not pleasant.
I remember my Grandparents talking about the horrible sound it made.....they lived only a few miles east of RAF Northolt during the BofB and Blitz, and my Grandfather was a fire-watcher.
What does un-synching the props actually mean, mechanically? It was pretty uncomfortable for the flying crews by all accounts, flying in a twin with un-synched props is not pleasant.
I remember my Grandparents talking about the horrible sound it made.....they lived only a few miles east of RAF Northolt during the BofB and Blitz, and my Grandfather was a fire-watcher.
Yertis said:
What does un-synching the props actually mean, mechanically?
The distinctive 'wob-wob-wob' beat of unsynched propellers is when the two props turn at similar but different speeds, so the sound and the physical air pressure waves coming off the prop interact and alternately amplify and cancel each other. A bit like a pipe with water hammer or, indeed, the exhaust beats of a Subaru flat-four engine.For the occupants of the plane it creates at best an irritating, perpetual, cyclical noise and at worse it makes for nausea- and headache-inducing vibrations.
Technology would later produce systems that could automatically get the engines not only in sync (turning at the same speed) but in phase (so the prop blades were in the same position as they went round). On WW2 aircraft it had to be done manually by the flight engineer tweaking the prop pitch by ear and by feel. It was relatively easy to do on a twin-engined aircraft but much harder on a four-engined 'heavy'.
Although the Luftwaffe flew out-of-sync as a rule (supposedly to confuse sound detectors), the Ju52 trimotor transport had a pair of 'wing mirrors' on either side of the nose, sized and angled to show the flicker of each of the wing engines' props against the flicker of the nose prop - the crew set cruise speed/power on the nose engine, set the power on the wing engines then tweaked each wing prop until it flickered in the mirror at the same time as the nose prop - then the engines were not only in sync but in phase. But the Ju52 was designed as an airliner so reducing noise and vibration was more of a consideration.
2xChevrons said:
The distinctive 'wob-wob-wob' beat of unsynched propellers is when the two props turn at similar but different speeds, so the sound and the physical air pressure waves coming off the prop interact and alternately amplify and cancel each other. A bit like a pipe with water hammer or, indeed, the exhaust beats of a Subaru flat-four engine.
For the occupants of the plane it creates at best an irritating, perpetual, cyclical noise and at worse it makes for nausea- and headache-inducing vibrations.
Technology would later produce systems that could automatically get the engines not only in sync (turning at the same speed) but in phase (so the prop blades were in the same position as they went round). On WW2 aircraft it had to be done manually by the flight engineer tweaking the prop pitch by ear and by feel. It was relatively easy to do on a twin-engined aircraft but much harder on a four-engined 'heavy'.
Although the Luftwaffe flew out-of-sync as a rule (supposedly to confuse sound detectors), the Ju52 trimotor transport had a pair of 'wing mirrors' on either side of the nose, sized and angled to show the flicker of each of the wing engines' props against the flicker of the nose prop - the crew set cruise speed/power on the nose engine, set the power on the wing engines then tweaked each wing prop until it flickered in the mirror at the same time as the nose prop - then the engines were not only in sync but in phase. But the Ju52 was designed as an airliner so reducing noise and vibration was more of a consideration.
For the occupants of the plane it creates at best an irritating, perpetual, cyclical noise and at worse it makes for nausea- and headache-inducing vibrations.
Technology would later produce systems that could automatically get the engines not only in sync (turning at the same speed) but in phase (so the prop blades were in the same position as they went round). On WW2 aircraft it had to be done manually by the flight engineer tweaking the prop pitch by ear and by feel. It was relatively easy to do on a twin-engined aircraft but much harder on a four-engined 'heavy'.
Although the Luftwaffe flew out-of-sync as a rule (supposedly to confuse sound detectors), the Ju52 trimotor transport had a pair of 'wing mirrors' on either side of the nose, sized and angled to show the flicker of each of the wing engines' props against the flicker of the nose prop - the crew set cruise speed/power on the nose engine, set the power on the wing engines then tweaked each wing prop until it flickered in the mirror at the same time as the nose prop - then the engines were not only in sync but in phase. But the Ju52 was designed as an airliner so reducing noise and vibration was more of a consideration.
Another long-term mystery solved.
2xChevrons said:
Yertis said:
What does un-synching the props actually mean, mechanically?
The distinctive 'wob-wob-wob' beat of unsynched propellers is when the two props turn at similar but different speeds, so the sound and the physical air pressure waves coming off the prop interact and alternately amplify and cancel each other. A bit like a pipe with water hammer or, indeed, the exhaust beats of a Subaru flat-four engine.For the occupants of the plane it creates at best an irritating, perpetual, cyclical noise and at worse it makes for nausea- and headache-inducing vibrations.
Technology would later produce systems that could automatically get the engines not only in sync (turning at the same speed) but in phase (so the prop blades were in the same position as they went round). On WW2 aircraft it had to be done manually by the flight engineer tweaking the prop pitch by ear and by feel. It was relatively easy to do on a twin-engined aircraft but much harder on a four-engined 'heavy'.
Although the Luftwaffe flew out-of-sync as a rule (supposedly to confuse sound detectors), the Ju52 trimotor transport had a pair of 'wing mirrors' on either side of the nose, sized and angled to show the flicker of each of the wing engines' props against the flicker of the nose prop - the crew set cruise speed/power on the nose engine, set the power on the wing engines then tweaked each wing prop until it flickered in the mirror at the same time as the nose prop - then the engines were not only in sync but in phase. But the Ju52 was designed as an airliner so reducing noise and vibration was more of a consideration.
Eric Mc said:
Some German aircraft did indeed have diesels, but the vast bulk of them were petrol fueled. I know a version of the Junkers Ju86 had diesels and some of the Blohm und Voss flying boats were also diesel powered.
While as you say the vast majority of German aero engines ran on petrol, they were diesel-like in one regard, in that they all used direct injection, whereas virtually all Allied engines ran carburetors.I've certainly noticed that DI petrol car engines can sound and feel a bit 'diesel like' around idle / low rpm, I have no idea if/how this might have affected the sound of an aero engine in flight though. IMO the Mercedes Gullwing (I6 with direct injection derived from German WW2 aero engines) has a very distinctive low-toned sound to it, but that may just be sui generis.
samoht said:
While as you say the vast majority of German aero engines ran on petrol, they were diesel-like in one regard, in that they all used direct injection, whereas virtually all Allied engines ran carburetors.
I've certainly noticed that DI petrol car engines can sound and feel a bit 'diesel like' around idle / low rpm, I have no idea if/how this might have affected the sound of an aero engine in flight though. IMO the Mercedes Gullwing (I6 with direct injection derived from German WW2 aero engines) has a very distinctive low-toned sound to it, but that may just be sui generis.
The Luftwaffe adopted fuel injection ahead of the RAF, hence when you needed to put your Merlin-engined fighter into a steep dive it was advisable to roll on your back first. I think - but stand to be corrected - that we didn't quite have the engineering skill needed.I've certainly noticed that DI petrol car engines can sound and feel a bit 'diesel like' around idle / low rpm, I have no idea if/how this might have affected the sound of an aero engine in flight though. IMO the Mercedes Gullwing (I6 with direct injection derived from German WW2 aero engines) has a very distinctive low-toned sound to it, but that may just be sui generis.
As for injection making a petrol engine sound like a diesel, I think that's more to with the exhaust and other factors than how the petrol gets into the cylinders. But I agree some of the big V8 Mercs have a lovely growly sound, much better than an over-excited V12 IMHO.
JU-86P high altitude reconnaissance version had Diesel engines.
I too built the Airfix 1/48 Spitfire VB as LO-W ‘Queen Salote of Tonga’.
The aircraft was funded by donations from that island.
An Irishman flying in a English designed & built fighter, funded by a Pacific island, for the Royal Airforce, in 602 ‘City of Glasgow’ Squadron.
I too built the Airfix 1/48 Spitfire VB as LO-W ‘Queen Salote of Tonga’.
The aircraft was funded by donations from that island.
An Irishman flying in a English designed & built fighter, funded by a Pacific island, for the Royal Airforce, in 602 ‘City of Glasgow’ Squadron.
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