Synchronising propellers
jw²
propeller synchronisation in multi-engine aeroplanes?
I've had scads of experience with synchronising alternators in power
houses and understand this fairly well, but I do not understand by what
mechanism aeroplane propellers could be locked in beat together for
extended periods except by continuous attention by the pilot.
I could perhaps understand that close monitoring of revs could be
managed by electronic demons in modern times, but how was this achieved
in days of yore?
Is it true that the German bombers did not have their propellers in
sync, resulting in a characteristic sound during WW2? Or was that
another war-time story we kids read about at the time?
Thanks
JW²
John Ewing
"jw˛" <nade...@optusnet.com.au> wrote in message
news:465eb554$0$26030$afc3...@news.optusnet.com.au...
> Can someone please enlighten me on the principle and practice of propeller
> synchronisation in multi-engine aeroplanes?
>
> I've had scads of experience with synchronising alternators in power
> houses and understand this fairly well, but I do not understand by what
> mechanism aeroplane propellers could be locked in beat together for
> extended periods except by continuous attention by the pilot.
Same principle as for alternator - by use of a speed governor. You will
probably have heard of the governor manufacturer Woodward - they make
governors for both applications. Prop Sync is simply to remove the
irritation of the noise (low frequency drone or beat frequency) which occurs
when the tips of the props are not in phase. Prop Sync is normally switched
off before takeoff and landing.
Cheers,
John
Stealth Pilot
wrote:
>Can someone please enlighten me on the principle and practice of
>propeller synchronisation in multi-engine aeroplanes?
>
>I've had scads of experience with synchronising alternators in power
>houses and understand this fairly well, but I do not understand by what
>mechanism aeroplane propellers could be locked in beat together for
>extended periods except by continuous attention by the pilot.
>
on the beech queenair the tacho has a little window in it whith a red
and white striped wheel. the wheel turned toward the faster engine.
matt weber
wrote:
>Can someone please enlighten me on the principle and practice of
closed loop servo systems have been around for a long time. (How do
you think autopilots worked before the days of fly by wire?)
The ability to match the speed and relative prop positions is
relatively recent. However large aircraft like the Constellation used
hydromechanical servo systems to get very close. A combination of
tweaking throttle and prop pitch is probably used. My recollection is
the system on the Connie could synch up the R3350 engines to within a
couple of RPM of each other.
These days it is largely electronics, and that has made it pretty
easy.
How good are electronics? Well on some disk drives I used to use, the
two spindles on different drives could be electronically locked, and
kept in the same relative position indefinitely to an angular position
accuracy of better than .01 degrees. Crank position sensors developed
for the automobile industry can give you the position of the crank to
better than 1 degree accuracy without batting an eyelash.
Michael Hoffmann
> Can someone please enlighten me on the principle and practice of
> propeller synchronisation in multi-engine aeroplanes?
Hi,
There was an excellent description on it in rec.aviation.piloting a
couple months back (ironically triggered once again by that moron
mxsmanic), some of the aviation pros there described the various forms.
There's also an excellent book "Advanced Aviation Systems", which
describes them in some detail.
> Is it true that the German bombers did not have their propellers in
> sync, resulting in a characteristic sound during WW2? Or was that
> another war-time story we kids read about at the time?
Never heard that.
Mike
veritas
> Prop Sync is normally switched
> off before takeoff and landing.
'caus (on models I flew) they tend to reduce the power on the fastest
engine :(
veritas
It seems that it may have been true. It was said that it increased the
noise/fear element of the enemy flying overhead.
JD
Makes sense - at maximum take-off power synchronising would have to be done
by reducing rpm on the prop going faster, since the other one(s) is already
going at maximum governed rpm, which implies a reduction in power -
normally very small, but could be significant in a critical situation. Of
course, in theory, all engines are set at the same maximum rpm - but in
practice this is never exactly the same, certainly not with
mechanical/hydraulic governors anyway. Plus the desirability of turning off
any complication that is not really necessary and whose malfunction could
cause safety concerns close to the ground.
JD
Michael Hoffmann
>>> Is it true that the German bombers did not have their propellers in
>>> sync, resulting in a characteristic sound during WW2? Or was that
>>> another war-time story we kids read about at the time?
>>
>> Never heard that.
>
> It seems that it may have been true. It was said that it increased the
> noise/fear element of the enemy flying overhead.
I'd like to read more on that if you have some links.
Googling for various combos of "German aircraft propeller
synchronisation" didn't return much beyond the old prop synching for
firing their guns through them.
Mike
John B
>>> Is it true that the German bombers did not have their propellers in
>>> sync, resulting in a characteristic sound during WW2? Or was that
>>> another war-time story we kids read about at the time?
>>
>> Never heard that.
>
> It seems that it may have been true. It was said that it increased the
> noise/fear element of the enemy flying overhead.
'Tis true. The main effect was to let us know it weren't any of ours.
JohnB
John Ewing
"JD" <j...@spamlesstpgi.com.au> wrote in message
news:465f...@dnews.tpgi.com.au...
Yes, and particularly during takeoff you want each engine to be
independently controlled, so that if one engine fails or has a drop in
performance it does not influence the good engine. If one engine was to
have a decrease in rpm during takeoff, you don't want the other to follow
it!
For those who have worked in the power generation industry an analogy is a
protection system that trips the bus tie circuit breaker if reverse power is
detected on a generator feeding that section of the bus. Principle is the
same - you are isolating the good generator and preventing it contributing
fault current to the defective generator.
John
Stealth Pilot
wrote:
it is true.
the gerries also didnt bother with opposite rotation engines so saw
some precession during some manouvers. the brit wellington pilots used
to take advantage of the difference when evading death by flying tight
manouvers at zero feet over the ocean. the brit machines could turn
either way at full tilt but the gerries often misjudged the precession
effects which would put a wing tip into the water with a fatal
cartwheel resulting and a very relieved wellie crew watching the
splash.
blitzkrieg didnt require elegant aerodynamics.
Stealth Pilot
RT
"Stealth Pilot" <notran...@aeroplanes.com.au> wrote in message
> it is true.
> the gerries also didnt bother with opposite rotation engines so saw
> some precession during some manouvers. the brit wellington pilots used
> to take advantage of the difference when evading death by flying tight
> manouvers at zero feet over the ocean. the brit machines could turn
> either way at full tilt but the gerries often misjudged the precession
> effects which would put a wing tip into the water with a fatal
> cartwheel resulting and a very relieved wellie crew watching the
> splash.
>
> blitzkrieg didnt require elegant aerodynamics.
Cite(s) please
veritas
I'm not much help to you there with a reference. As a small boy (WW2) I
had an interest in aircraft (my dad was in the RAAF) and I never lost
it. I guess I had him tell me about it at some time.
Ric
"jw²" <nade...@optusnet.com.au> wrote in message
news:465eb554$0$26030$afc3...@news.optusnet.com.au...
The B200 I maintain has a prop sync system. One prop is the master prop and
the other is the slave. On the rear of the prop spinner backplate are
"interupters" which pass by a pickup. There is a prop sync box which is full
of strings and mirrors (cone head stuff) which sends a signal to the prop
sync servo on the slave engine. The servo is mounted inline with the
operating cable for the prop governer. When this servo gets the signal from
the box it will adjust the prop governer to increase or decrease the the
prop rpm to match the Master prop. It can only adjust small amounts though,
from memory + - 60rpm. Leaving the prop sync system on whilst the props are
outside the + - can damage the servo mechanism. Our B200's (Pearl Aviation)
have an EO to disable the sync system because they keep breaking.
The pilot has a prop sync indicator, a small black and white wheel, which
rotates towards the fast prop. If the wheel is stationary the props are in
sync. In reality though it is easier to do by ear.
>
Ned
No question the effect existed as anyone who was in England at the
time will confirm.
But I doubt it was a design feature.
The Stuka sirens OTOH *were* deliberately fitted to strike terror into
the hearts of those (mainly civilians) below an attack. Same tactic
adopted by the US and it's allies in the 2003 Shock and Awe terror
bombing campaign of Baghdad.
Ned
moon
Stealth Pilot <notranspon...@aeroplanes.com.au> wrote:
.............
> the gerries also didnt bother with opposite rotation engines so saw
> some precession during some manouvers. the brit wellington pilots used
> to take advantage of the difference when evading death by flying tight
> manouvers at zero feet over the ocean. the brit machines could turn
> either way at full tilt but the gerries often misjudged the precession
> effects which would put a wing tip into the water with a fatal
> cartwheel resulting and a very relieved wellie crew watching the
> splash.
>
> blitzkrieg didnt require elegant aerodynamics.
>
> Stealth Pilot
What a load of floam-flecked raving lunatic garbage even by your
standards Stealth.
jw²
I had not taken the existence of a governor servo-system in the
pre-electronic control era into account. It seems that in the
pre-electronic control era, the pilot was indeed in the loop, but not to
the extent that it required his constant attention, which was my
sticking point.
Thanks again.
JW²
Peter Fanelli
server.bigpond.net.au:
Don't know about people on the ground but I'm sure such a practice would
send the pilots to the funny farm in short order.
Michael Hoffmann
> it is true.
> the gerries also didnt bother with opposite rotation engines so saw
> some precession during some manouvers. the brit wellington pilots used
> to take advantage of the difference when evading death by flying tight
> manouvers at zero feet over the ocean. the brit machines could turn
> either way at full tilt but the gerries often misjudged the precession
> effects which would put a wing tip into the water with a fatal
> cartwheel resulting and a very relieved wellie crew watching the
> splash.
>
> blitzkrieg didnt require elegant aerodynamics.
Just to be picky: by the time it was the Germans chasing Wellingtons the
Blitz was over, they lost the BoB and the tables had turned. Well
mostly, anyway.
Mike
Michael Hoffmann
> I'm not much help to you there with a reference. As a small boy (WW2) I
> had an interest in aircraft (my dad was in the RAAF) and I never lost
> it. I guess I had him tell me about it at some time.
Well, with all due respect to your dad, that doesn't quite count as an
authoritative engineering or historical based choice. ;)
I read quite a number of books on German WW2 aircraft - from German
sources, many of them by the engineers and pilots who were still alive
then (being a kraut by birth I can read them in the original) - and
never ever stumbled across that tidbit.
Mike
Michael Hoffmann
> My understanding of is that German wartime engine factories preferred
> not to build opposite rotating engines - better manufacturing
> efficiency, they said.
> Therefore pilots of German multi engined aeroplanes compensated for
> crabbing tendencies in flight by running one engine faster than the
> other.
Dimly remember the Hs129 used counter-rotation. Trying to dig up a
source - Wikipedia only has a photo that seems to show the props in a
counter-rotation setup but the article mentions nothing one way or the
other.
Photos of a model here http://www.scaleworkshop.com/workshop/hs129jh_1.htm
...
Aha... googling for "henschel hs 129 counter" returns a number of hits.
Not exactly one of the main-stream aircraft, I admit.
Did the Mossie have counter-rotating props? When I build the 1/32 model
years and years ago, I didn't notice. Should fly into Pt Cook and check
out theirs, if it's in any stage yet to see that.
Mike
Michael Hoffmann
> The Stuka sirens OTOH *were* deliberately fitted to strike terror into
> the hearts of those (mainly civilians) below an attack. Same tactic
> adopted by the US and it's allies in the 2003 Shock and Awe terror
> bombing campaign of Baghdad.
Often wondered how much drag those things added - turning an already
lame duck into a dead duck for the British Spits.
Mike
Michael Hoffmann
> I don't think that's correct for the he129 of for that matter the
> Ju88. The Junkers Jumo engine was widely used in fighters and it was
> considered inefficient to maintain parallel production lines for
> bombers.
Hs129, not He129 (whatever that was).
Attack plane, designed in a rush with whatever engines were available,
ended up using mostly Rhone (with a ^ over the o) counter-rotating engines.
Mike
Gordon Beaman
>Michael Hoffmann wrote:
>
>>Sam wrote:
>>
>>> My understanding of is that German wartime engine factories preferred
>>> not to build opposite rotating engines - better manufacturing
>>> efficiency, they said.
>>> Therefore pilots of German multi engined aeroplanes compensated for
>>> crabbing tendencies in flight by running one engine faster than the
>>> other.
>>
>>Dimly remember the Hs129 used counter-rotation. Trying to dig up a
>>source - Wikipedia only has a photo that seems to show the props in a
>>counter-rotation setup but the article mentions nothing one way or the
>>other.
>
>I don't think that's correct for the he129 of for that matter the
>Ju88. The Junkers Jumo engine was widely used in fighters and it was
>considered inefficient to maintain parallel production lines for
>bombers.
>The allies had a much greater manufacturing capability and were able
>to produce Merlins of both rotations as required by fighters, 2
>engined fighter/bombers (Mossies etc), and 4 engined heavy
>bombers(Lancasters).
>Sources: Discussions with WW2 pilots and many books read over 55
>years. There are plenty of articles on the Junkers Jumo and RR
>Merlin/Griffin on the web, but I CBA citing them all.
>
>--
>Sam
Sounds like you think that Lancasters require both LH and RH rotating
engines...not correct sir...just RH...
Ned
>
> I read quite a number of books on German WW2 aircraft -
> from German sources,
Mike - try to get hold of some of "Winkle" Brown's excellent books eg
Wings of the Luftwaffe ISBN 0 906393 88 4, Wings of the Weird and
Wonderful Vols 1 - x? and Wings on my Sleeve. Try www.navybooks.com
AFAIK Captain Eric Melrose "Winkle" Brown, CBE, DSC, AFC, FRAeS, RN
holds the record for having flown more aircraft types than any other
pilot in history including 55 different WW2 German varietys.
He also holds the record for having flown most carrier landings - one
of which was a deliberate wheels up - IIRC in a Vampire.
>many of them by the engineers and pilots who were still alive
> then ....
Post WW2 Brown also interrogated Leute like Willy Messerschmitt, Hanna
Reitsch, Kurt Tank, Ernst Heinkel, von Braun usw
>(being a kraut by birth I can read them in the original)
Brown spoke fluent Deutsch having graduated with an MA in German from
Edinburgh Uni
Cheers
Ned
Ned
Thanks Gord - beat me to it.
The Mossie was both engines RH too.
The P-38 Lightning did have counter rotating props.
So did the Me-323 Gigant - as one might expect with six x 14 cyl
engines hauling it into the air.
Cheers
Ned
Coop
<edward_...@bluebottle.com> wrote:
>On Jun 2, 10:39 am, Michael Hoffmann <b...@blather.com> wrote:
>>
>> I read quite a number of books on German WW2 aircraft -
>> from German sources,
>
>Mike - try to get hold of some of "Winkle" Brown's excellent books eg
>Wings of the Luftwaffe ISBN 0 906393 88 4, Wings of the Weird and
>Wonderful Vols 1 - x? and Wings on my Sleeve. Try www.navybooks.com
>
>AFAIK Captain Eric Melrose "Winkle" Brown, CBE, DSC, AFC, FRAeS, RN
>holds the record for having flown more aircraft types than any other
>pilot in history including 55 different WW2 German varietys.
>
>He also holds the record for having flown most carrier landings - one
>of which was a deliberate wheels up - IIRC in a Vampire.
Not just one. I have his book "Wings on my Sleeve" in my hand- and I
am looking at a picture of a Vampire nose down in its "flexible deck".
The idea was to land aircraft on carriers using a sprung rubber deck
like a trampoline- the cable would stop the aircraft, which would
bounce onto the deck and be hauled off for stowage by a crane. The
first attempt (on a land-based deck) ended with a major crash when the
aircraft failed to respond as predicted to increased power. This was
traced to the increased airflow at the intakes affecting the airflow
over the wing. Brown plowed into the deck and failed to hook the cable
(owing to a hook fault). After they had sorted the problem, he did 40
of these landings on the land setup, and a whole series of them on a
suitable equipped carrier, including with a 30 knot, 18 degree
side-wind.
The concept was proven (no need for undercarriage, so you can carry
more fuel and armaments, and you could fit more in the hangar, but the
disadvantage was that you needed a deck wherever you landed- no
emergency landings on unequipped strips) but was never taken up. He
probably has another record- the most "wheels up" landings of any
pilot!!
Coop
Mitchell Schaeffer
"Ric" <som...@microsoft.com> wrote in message
news:4660120e$0$26030$afc3...@news.optusnet.com.au...
I have always found the black and white eaiser, but thats just me :)
Mitchell
John B
> Well, with all due respect to your dad, that doesn't quite count as an
> authoritative engineering or historical based choice. ;)
Now that is a rather condescending tone. "With all due respect" to you - I
might not have qualifications as an authorative engineer. But historically,
living for four years in Portrsmouth during WW2 the Luftwaffe managed to
bomb us out of 5 houses and I can assure you that I know what that sounds
like!
JohnB
Ric
"John B" <jbot...@bigpond.net.au> wrote in message
news:AR98i.7708$wH4....@news-server.bigpond.net.au...
I think after the first 2 bombings I would be moving to the other side of
the island :0)
>
>
>
>
Ric
"Sam" <sam...@hihat.com> wrote in message
news:2id263p6hh58o14b9...@4ax.com...
> Ned wrote:
> [...]
>
>>> >--
>>> >Sam
>>>
>>> Sounds like you think that Lancasters require both LH and RH rotating
>>> engines...not correct sir...just RH...-
>>
>>Thanks Gord - beat me to it.
>>
>>The Mossie was both engines RH too.
>
>
> engines installed in the mossie were 2в Rolls-Royce Merlin 76/77
> (left/right) liquid-cooled V12 engine, 1,710 hp each. I can't find
> anything authoritative on the web other than
This seems to contradict your info.
http://www.youtube.com/watch?v=Mp0486rsaAM&mode=related&search=
>
> http://www.answers.com/topic/de-havilland-mosquito
>
> and similarly
>
> http://en.wikipedia.org/wiki/De_Havilland_Mosquito
>
> I know that there has been a lot written on the out of synch thing
> with German WW2 aircraft, and I will now try to track some of it down
> again.
>
>>The P-38 Lightning did have counter rotating props.
>>
>>So did the Me-323 Gigant - as one might expect with six x 14 cyl
>>engines hauling it into the air.
>
> --
> Sam
>
> --
> Posted via a free Usenet account from http://www.teranews.com
>
>
veritas
Careful reading of my original comments should show as purposely phrased
so that it would be not be construed as definitive.
Sorry if I gave a contrary impression.
Coop
wrote:
<Chuckle> I think THAT'S authoritative.....
Coop (Still grinning....)
Stealth Pilot
wrote:
Thomas H Hicks. architect I worked with who was an ex ww2 wellington
pilot. scene of the evasions by him and others was the mediterranean.
Stealth ( :-P ) Pilot
Michael Hoffmann
> Mike - try to get hold of some of "Winkle" Brown's excellent books eg
> Wings of the Luftwaffe ISBN 0 906393 88 4, Wings of the Weird and
> Wonderful Vols 1 - x? and Wings on my Sleeve. Try www.navybooks.com
>
> AFAIK Captain Eric Melrose "Winkle" Brown, CBE, DSC, AFC, FRAeS, RN
> holds the record for having flown more aircraft types than any other
> pilot in history including 55 different WW2 German varietys.
Ah! Finally :) I will try to get my hands on that.
According to Amazon UK it's out of print, but there's some used ones.
When will we finally get Amazon Aus?! <tap foot>
Mike
Michael Hoffmann
> Careful reading of my original comments should show as purposely phrased
> so that it would be not be construed as definitive.
>
> Sorry if I gave a contrary impression.
I would also like to add that I'm not trying to speak from a position of
authority here - if anything I'm just rather surprised that I'd never
encountered this information in decades of reading books on WW2 aviation.
There *are* a lot of OWTs and Urban Legends in aviation, so my first
reaction is always to be skeptical when I read it on the Net.
Neb was the first provide a source that I can go and read up on.
Mike
Ron
had synchronising and synchrophasing, synchronising the RPM and
synchrophasing the blade angle between the props - to a. stop the beat and
b. further minimise the noise and vibration within the fuselage. How - the
basic hydro mechanical governor on each prop was 'tweaked' by an electronic
signal via an electric motor to adjust each govoernor RPM and align the
blade angles to predetermined angles wrt the master propellor.
Did it work - yes - but .......... occasionally the 'Mechanical Governing'
selection worked better.
A google search found a research paper on said subject of shnchrophasing.
http://www.mecheng.adelaide.edu.au/anvc/publications/public_papers/2006/a06_087.pdf
regards Ron
"jw˛" <nade...@optusnet.com.au> wrote in message
news:465eb554$0$26030$afc3...@news.optusnet.com.au...
> Can someone please enlighten me on the principle and practice of propeller
> synchronisation in multi-engine aeroplanes?
>
> I've had scads of experience with synchronising alternators in power
> houses and understand this fairly well, but I do not understand by what
> mechanism aeroplane propellers could be locked in beat together for
> extended periods except by continuous attention by the pilot.
>
> I could perhaps understand that close monitoring of revs could be managed
> by electronic demons in modern times, but how was this achieved in days of
> yore?
>
> Is it true that the German bombers did not have their propellers in sync,
> resulting in a characteristic sound during WW2? Or was that another
> war-time story we kids read about at the time?
>
> Thanks
>
> JW˛
RT
Mmm - ok - but just what were these Wellingtons being chased by that had
twin engines but were a fighter with such poor performance they couldn't
shoot down the average bomber irrewardless of having both engines turning
the same way? And if you'd forced something down to dot why would you not
stay above it and pepper it at your liesure. Deffenly sounds suss to me
Stealth - and coming from an architect certainly doesn't help :-)
RT
"Ron" <haaN...@iprimus.com.au> wrote in message
news:466006ce$1...@news.iprimus.com.au...
>I flew aeroplanes in the 80s (designed in the 60s - read fat albert) that
>had synchronising and synchrophasing, synchronising the RPM and
>synchrophasing the blade angle between the props - to a. stop the beat and
>b. further minimise the noise and vibration within the fuselage. How - the
>basic hydro mechanical governor on each prop was 'tweaked' by an electronic
>signal via an electric motor to adjust each govoernor RPM and align the
>blade angles to predetermined angles wrt the master propellor.
>
> Did it work - yes - but .......... occasionally the 'Mechanical Governing'
> selection worked better.
>
> A google search found a research paper on said subject of shnchrophasing.
> http://www.mecheng.adelaide.edu.au/anvc/publications/public_papers/2006/a06_087.pdf
>
> news:465eb554$0$26030$afc3...@news.optusnet.com.au...
>> Can someone please enlighten me on the principle and practice of
>> propeller synchronisation in multi-engine aeroplanes?
>>
>> I've had scads of experience with synchronising alternators in power
>> houses and understand this fairly well, but I do not understand by what
>> mechanism aeroplane propellers could be locked in beat together for
>> extended periods except by continuous attention by the pilot.
>>
>> I could perhaps understand that close monitoring of revs could be managed
>> by electronic demons in modern times, but how was this achieved in days
>> of yore?
>>
>> Is it true that the German bombers did not have their propellers in sync,
>> resulting in a characteristic sound during WW2? Or was that another
>> war-time story we kids read about at the time?
The synchronisation on the Dash 8s is close to perfect (and I think includes
syncrophasing from idle discussion with one of the maintenance mob some
years ago). Very, very impressive as a difference of even 15 rpm between
engines will give a very obvious beat with period of 4 seconds. The last
few flights on 'em have given (occasionally) a very brief period of beats at
power change but that's it.
As far as the German bombers are concerned, might that have been beats
generated between a/c in the formation rather than from a particular a/c?
In light twins which were about the level of sophistication of the WWII
bombers, the final synchronisation of the engines was/is manual - carefull
tweaking of one rpm (prop) control until the beat becomes slower and slower
and you eventually get a continuous sound. Until you change power
parameters again, of course :-)
Michael Hoffmann
> As far as the German bombers are concerned, might that have been beats
> generated between a/c in the formation rather than from a particular a/c?
>
> In light twins which were about the level of sophistication of the WWII
> bombers, the final synchronisation of the engines was/is manual - carefull
> tweaking of one rpm (prop) control until the beat becomes slower and slower
> and you eventually get a continuous sound. Until you change power
> parameters again, of course :-)
Various googles later, from what little I could find at this time, it
seems that German attack formation would indeed change their
synchronisation for the attack itself, but not the entire flight.
Somebody else here wrote that it would have driven the pilots batty.
They already had the agony of useless to non-existent fighter cover to
deal with (the 109s were off protecting the 110s dontchaknow? or had
just run out of fuel :-P), so they didn't needed their intestines slowly
being shaken well enough to make a Martini envious.
I only have a handful of multi-hours but had to learn synching by the
old "ears and tach" method. For some reason unsynched props made me
sleepy - not the best thing in the left seat. ;)
Mike
John B
"RT" <notr....@nowhere.com.au> wrote in message
news:5cf165F...@mid.individual.net...
It might be generated by numbers of a/c being in formation - but it was also
a characteristic of individual a/c.
> In light twins which were about the level of sophistication of the WWII
> bombers, the final synchronisation of the engines was/is manual - carefull
> tweaking of one rpm (prop) control until the beat becomes slower and
> slower and you eventually get a continuous sound. Until you change power
> parameters again, of course :-)
Post war RAF heavies (4 engines) had manual synchronisation with a visual
aid instrument showing 3 props turning clockwise or anti in reference to
Number 1. An idle pilot or copilot on an 18 hour flight could drive you mad.
JohnB
Ric
> Ric wrote:
>
>>
>>"Sam" <sam...@hihat.com> wrote in message
>>news:2id263p6hh58o14b9...@4ax.com...
>>> Ned wrote:
>>> [...]
>>>
>>>>> >--
>>>>> >Sam
>>>>>
>>>>> Sounds like you think that Lancasters require both LH and RH rotating
>>>>> engines...not correct sir...just RH...-
>>>>
>>>>Thanks Gord - beat me to it.
>>>>
>>>>The Mossie was both engines RH too.
>>>
>>>
>>> That one had me a bit worried, but again that is not correct. The
>>> (left/right) liquid-cooled V12 engine, 1,710 hp each. I can't find
>>> anything authoritative on the web other than
>>
>>This seems to contradict your info.
>>
>>http://www.youtube.com/watch?v=Mp0486rsaAM&mode=related&search=
>
> stoppages and restarts I'm pretty sure they were contra-rotating.
> Unfortunately strobe effects make it a bit uncertain, but I'm
> convinced.
At the 3:18 mark the stbd engine is motored over with the starter and at the
3:42 mark the port engine is motored over in the same direction. Merely
looking at the stationary blades will tell you that both blades, and
therefore both engines, rotate in the same direction.
RT
"GB" <gb0...@kickindanuts.threefiddy.com> wrote in message
news:1364qlr...@corp.supernews.com...
> "RT" <notr....@nowhere.com.au> wrote in
> news:5cf165F...@mid.individual.net:
>> The synchronisation on the Dash 8s is close to perfect (and I think
>> includes syncrophasing from idle discussion with one of the
>> maintenance mob some years ago).
>
> props is concerned - in the cabin they have some substantial
> acousto-mechanical devices controlled by confusers) but I do know
> that they make quite a big thing of it in the marketing materials
> for the Q series Dash 8s.
>
> POST: a quick dig around turns up this link:
>
> <http://www.q400.com/q400/en/quiet.jsp>
>
> The cabin noise supression seems to be quite distinct from the
> engine/prop control stuff, though I'm guessing that it's maybe
> just a little more complext than the single engine tacho input
> that the diagrams show!
I'm on dial-up so not going to chase up that site, however if they are using
ANS (Active Noise Suppression) I'd be surprised as it's a bit complex and
the level of vibes (albeit in phase!) in the cabin suggests they don't :-)
(On another topic I have pinged you via email as requested)
Gordon Beaman
I remember that the P2V-7 Neptune (as fitted in the RCAF, about 1955)
had this little sync indicator...I believe that the 'slave' engine
would follow the 'master' by 150 rpm for each push of the 'resync
switch'...
away-pits
> On Sat, 02 Jun 2007 07:17:59 GMT, "Mitchell Schaeffer"
>
>
>
>
> >"Ric" <some...@microsoft.com> wrote in message
> >news:4660120e$0$26030$afc3...@news.optusnet.com.au...
>
> >> "jw²" <nadej...@optusnet.com.au> wrote in message
Just to add a bit more research links to this thread ( pedants may
wish to check every type of German Aircraft)
This is an interesting and time consuming link
http://en.wikipedia.org/wiki/List_of_World_War_II_military_aircraft_of_Germany
Given the hammering the German factories took from allied forces (not
wishing to get into war discussions) The logistics and output appear
to me truly amazing (to me) and speaks tomes for the resilience of a
nation led into a horrific nightmare by a madman .
Gordon Beaman
>Ric wrote:
>
>>
>>"Sam" <sam...@hihat.com> wrote in message
>>news:2id263p6hh58o14b9...@4ax.com...
>>> Ned wrote:
>>> [...]
>>>
>>>>> >--
>>>>> >Sam
>>>>>
>>>>> Sounds like you think that Lancasters require both LH and RH rotating
>>>>> engines...not correct sir...just RH...-
>>>>
>>>>Thanks Gord - beat me to it.
>>>>
>>>>The Mossie was both engines RH too.
>>>
>>>
>>> That one had me a bit worried, but again that is not correct. The
>>> engines installed in the mossie were 2× Rolls-Royce Merlin 76/77
>>> (left/right) liquid-cooled V12 engine, 1,710 hp each. I can't find
>>> anything authoritative on the web other than
>>
>>This seems to contradict your info.
>>
>>http://www.youtube.com/watch?v=Mp0486rsaAM&mode=related&search=
>
>At first I was going to concede that you might be right, but after the
>stoppages and restarts I'm pretty sure they were contra-rotating.
>Unfortunately strobe effects make it a bit uncertain, but I'm
>convinced.
>
>--
>Sam
Better get unconvinced then Sam...the one in the clip has both engines
as 'right hand tractors' meaning that they both turn right hand and
they're 'pullers', instead of being 'pushers' as any prop that
'pushes' is (guess what) a pusher (ie: B-36)