Rarest engine sound? Macchi Mc 72 & Fiat AS.6

[JDK]

For the current Aircrew feature in Aeroplane magazine, illustrator In Bott and I chose the Macchi Mc 72 seaplane racer and world-record setter.



A fascinating aircraft, on any account, and while researching it I came across a WAV file that claims to be the sound of the Mc 72 in flight, and thus the sound of its unique engine and prop setup.

Here: http://www.aviationtrivia.info/documents/MC72.wav

Given that there's never been another engine quite like it coupled to a fixed-pitch contra-prop set in a floatplane which flew for as short a period as this, it's got to be one of the rarest high-power piston aero engine sounds.



A bit more from my blog here: http://vintageaeroplanewriter.blogspot. ... rcrew.html

And a background to the engine and aircraft here:
http://en.wikipedia.org/wiki/Macchi_M.C.72
http://en.wikipedia.org/wiki/Fiat_AS.6

Perhaps the most noteworthy thing about the Mc 72 is that it still holds the piston-power world seaplane air speed record - getting on for eighty years later! Few records of the 1930s still stand in the 21st century.

Hope that's of interest...

Regards,

(* There have of course been faster jet and turbo-prop marine aircraft, but not piston-engined.)

[The Inspector]

Sounds like Godzilla ripping a sheet of canvas!

[JDK]

I'd prefer to say "a bit more than 3,000 tortured Italian stallions"!

[The Inspector]

Is this where I say 'Yo-Adriene' That really is a frightening tone and must have sent chills up every back that was there to hear it in full effect-sort of like hearing the Napier SABRE engine sound track, eerie

[Flagon]

That the airframe survived at all is a miracle.
The file is probably original,it sounds like TWO engines,which is the truth,they where started independently,the beast was a twin,that's why it did not participate in the last Schneider Cup,Raus,Banned.
I've seen the beauty,it's in Vigna di Valle,near Rome.

[JDK]

Nice to see a new face on WIX, welcome!

That the airframe survived at all is a miracle.

Yes, certainly. There were three originally, but two were lost in race accidents, and the sole survivor was retired straight after setting the absolute world speed record.

The file is probably original,it sounds like TWO engines,...

I agree, but I'd like to know it's provenance.

...the beast was a twin,that's why it did not participate in the last Schneider Cup,Raus,Banned.

Welll... The Fiat AS.6 is two coupled engines into one - it's pretty 'Siamesed' so you can see it as one engine, or two. Not that they tried, but you can't run one half of the AS.6 seperately from the other, although each drove one of the props.

Here's a couple of pics of the AS.6 and its join.





That said, AFAIK it wasn't banned from the final Schneider trophy, the problem was it couldn't be readied in time. There were criteria for the Schneider racers, such as staying afloat for a period without sinking (and at least one only just survived the timed period, due to a float leak) but I'm not aware of any engine criteria limitations. Corrections welcome!

Regards,

[Flagon]

JDK,Grazie per il benvenuto !
Well,you could start them independently,not sure the aircraft would fly(think not)but it was done at every startup.
Also,common thinking here is that the aircraft was not late in setup,rather it was not compliant to the rules that specified a SINGLE engined craft.
Ciao.

[Mike]

Wasn't there a piece of film on Pathe of the MC72 starting up?

Wherever did you get the idea of doing a piece on it from, James?

[Mike]

Here's the link to the film, perhaps you'll have more luck than I did in getting it to load

http://www.britishpathe.com/record.php?id=27626

[JDK]

Non e un problemo!

Separate engines - good point on the starting, my assumption was that they were geared together, following Mario Castoldi's statement in L'Ala d'Italia [The Italian Wing] in April 1942 [my shortened translation]:
“The contra rotating propeller has it’s own advantages for high power and speed. The advantages are conspicuously simple, in that they decrease the size of the arc of the propeller, and they are less than an equivalent four blade propeller required to absorb equivalent power, and lowers the tip speed, an important factor in the required high performance.” He went on to add that the separate engine ‘halves’ driving separate propellers “made it difficult to ensure both propellers were turning at equal revolutions, but it was found acceptable within a variation of 2 – 3%.”

Original here:

« La doppia elica ha il suo campo d'azione per potenze molto forti e per le altissime velocità. I vantaggi rispetto all'elica semplice sono cospi­cui, poiché con l'accoppiamento delle eliche, supposta una data forma di pala, si può ottenere il minimo diametro possibile, inferiore a quello dell'elica a quattro pale che assorba ugual potenza. Il sistema è perciò indicato per ridurre la velocità periferica delle pale, condizione indispensabile per avere un rendimento elevato. Questi vantaggi si apprezzano specialmente quando si disponga di motori di potenza di 2000-3000 cavalli o supe­riore (potenze verso le quali la motoristica moder­na si avvia rapidamente) da montare su apparecchi molto veloci.

« Le due eliche dell'M.C.72 erano azionate se­paratamente da due motori accoppiati. Ciò rendeva difficile mantenere costantemente uguale il numero dei giri delle due eliche. Si è constatato però che il rendimento si manteneva ugualmente buono, per le piccole variazioni di giri delle due eliche che al massimo arrivavano al 2 o al 3 %.

http://www.alieuomini.it/pagine/dettagl ... ld,19.html

Still can't find any reference to disqualification at the time of the final Schneider race, but several references to engine problems (not surprising, of course) and the fatal crash of one of the machines killing pilot Monti due to a propeller failure while trying to establish the cause of the backfire[?] engine problems.

Thanks Mike. The story of 'why' this one's interesting, as you know.

The Pathe film doesn't show the engine starting, but does show both props stopping on the taxi in, simultaneously. However the You-Tube film I embedded in my blog post shows the aft prop running at start while the fwd one is starting up, so clearly not geared together as I'd assumed - silly of me, really, on a re-read.

I'd add that reliable data tracking back to original data on the type and history is actually very tricky to find, once you get past the main facts. Yet this is a fascinating and historically important aircraft.

The You-Tube film: http://www.youtube.com/watch?v=2ujmLZVUC-g

Regards,

[carlisle1926]

That engine is amazing. I'm trying to get my head around how they transmitted power from one crankshaft to the other if the engines could be started separately.

[JDK]

No, one engine 'half' turned one prop, while the other half turned the other prop the other way, making a contra-prop setup. Complex, but the simplest solution taking that route.

[JDK]

Quoting Terry Gwinn-Jones in 'Farther and Faster' on the Mc 72:
"Flight testing was being slowed by carburation problems when tragedy struck. Only a month before the race, Monti was killed while practising in one of the new machines.
Nine days before the scheduled race day, Italy and France requested that the British postpone the race for six months as neither was ready to send teams. The Royal Aero Club, invoking the rules, refused to delay the race. Two days later Italy and France advised the Air Ministry that neither would compete."

Again, a complex story, but nothing about a twin-engine type being disqualified. I'd be most interested in any original data suggesting that though.

Ciao!

[oz rb fan]

ive never heard of it being banned.
here is another video of it in flight plus English commentary(though some of the flight and landing seems to one of the earlier macchi seaplanes.
http://www.youtube.com/watch?v=gLRLhZJsCh4&NR=1
one of my favorite planes

[JDK]

Thanks for that. Good old 'Bomberguy'!

The initial film shot after the stills shows the best sequence of the AS.6 engine start, with the aft engine half firing up first and powering the fwd prop, and the other half firing up almost immediately after.

The sound may also be natural and original.

Regards,