Wooden Props

[Graham Clark]

A few days ago I was looking at Evra’s wooden prop web site and found a two drawings, one of a prop stopped horizontally at 'quarter to three' and the second at 'ten to four'. The Evra caption says:
IMPORTANT: When the aircraft is parked outside, never leave the propeller in a horizontal position.

I was puzzled, because this manufacturer’s advice is contrary to everything that I have previously heard, and I am trying to determine their reason.

The caption makes no mention of other manufacturers’ wooden propellers, or wooden propellers on aircraft parked inside a hanger. Nor does it mention whether the aircraft is parked for one hour or one year.

So why does Evra differ from the received wisdom?
And why is the received wisdom 'prop must be parked horizontally'?

Before you all say: “Humidity, imbalanced prop”, I must ask how a propeller made of layers of best quality seasoned French beech, bonded by best quality French polywhatsit adhesives, and encased in a French resin-soaked GRP sheath, and then sealed by layers of French paint, is going to take up even a molecule of water vapour. Capillary action? With that water barrier? Even if, water migrates just as well uphill as downhill. So if Evra says ‘park your prop at ten to four’ (which what the drawing says), they must have a reason.

Is this maybe a hangover from WW1 when wooden props were finished in varnish?

It can’t be anything to do with rain water (ice? Snow?) accumulating in the spinner.

The Evra advice is directly contrary to the current practice of many grey-haired aviators. But in spite of asking around, I have not been able to dig out a convincing, answer. None of their answers held water……..

I asked another prop maker. He could not give a suggestion.
I asked on the Flyer Forum. Not a single answer.

Time to debunk an Old Wives' Tale?

[Andrew Leak]

I maybe wrong here, but what I heard is something to do with the spinner and the way water settles inside and then ices up. If you leave the prop it at 10 to 4 the moisture will run out better. Again, I could be wrong about the wooden prop thing so I'm prepared to be shot down!

[Jeremy Liber]

Hi Graham

Interesting question. As you know I always 'park' my prop horizontally based on the 'moisture uptake' theory. I can shed no light on why Evra recommend never leaving the prop horizontal but would be very interested to know why Evra advise as they do.

Have you asked them directly?

Regards

Jeremy

[Mark Miller]

Maybe Evra's thinking is less scientific than is being assumed?

I was in their country of origin the weekend before last, doing the Annual on a G-regd Hornet Moth, and was preparing to tuck the aeroplane away in its little hangar within a hangar. This always bothers me because if the prop were to be sticking up too much, the high blade tip could be broken off on entry.

I turned the prop to fire the impulse, and then backwards to horizontal. At once a couple of Frenchmen scolded me and one tweaked the prop back another 10 degrees or so. As best as I could understand them, it was their belief - carried forward they said from WW1 days - that a horizontal prop will bring the pilot bad luck!

[Nigel Ramsay]

Maybe Evra's thinking is less scientific than is being assumed?carried forward they said from WW1 days - that a horizontal prop will bring the pilot bad luck!

Well there you have it! No more horizontal props in our hangar!

[Richard Boyton]

I suspect that it might be to to do with "live" props and unrelaible mag switches or switches left on

I seem to remember, and at my age that takes something, that rotaries fired when the prop was pulled through the horizontal.

Therefore leaving one in this position was vunerable to a swift amputation if touched, whereas if parked vertical or near so, the engine would not fire if touched

This is how myths arise and live on, but I will check with John Munn at Shuttleworth and report back

Didn't James Mc Cudden get into all sorts of trouble when a mechanic in earlier days of the RFC, when he "touched" a prop, it fired and all sorts of mayhem ensued

BTW, a suitable and now lost toast in RFC Messes was not "Cheers", but "Suck In"...rather appropriate in the flying community ....

[Alan Kilbride]

From a bad experience last week. A horizontal prop took some of the paint of my rudder. Had the prop been vertical, it would have missed. This was of course due a to hangar rash incident. You could say my aircraft put some paint on to a horizontal prop as it was mine some one was putting away.

[Jim Hargrave]

More 'grist for the mill' if I mention an experience I had with an unbalanced prop. Way back I had to put a Turbulent down in a field because of a lowering cloudbase and the onset of rain. When I got the a/c parked up in the corner of the field the heavens opened and I made a quick exit to the nearest farmhouse to dry off and call for a lift home not taking any notice how the prop was sitting.

In the morning it was good enough to fly her out of the field but on start-up it was if there was a lead weight in one blade as the vibration was terrific. Checking everything there was no apparent damage to the prop but we decided to change it for a prop from the sister Turbulent in our syndicate as water was a likely cause.

We changed the prop and everything was again good to go and I flew her out to complete the journey back to home base. Prop was good when dried out.

[DavidMiller]

I've only just come across this thread, hence the late contribution.

Have you ever tried to cross a hangar when it is in pitch darkness?

A horizontal prop is a major hazard, and it is just at eye level!

[Chris Martyr]

GollyGosh David,
Hope there aren't any of them health & safety/risk assessment type johnnies reading this, as they will tell you quite unequivocally that walking across a pitch dark hangar in any circumstances is an absolute no-no , as you should be comfortably ensconced in the pub by that time of day !
Although seriously , whatever angle you leave your prop at , there are far more hazards waiting to get you than just that. E.G. pitot tube in the eye , aileron t/e clonking you on the nose , elevator of a tailwheeler in the shin , elevator of a tricycle in the face , going base over apex over a chock/mainwheel/wheelspat , toolboxes , mousetraps , it doesn't bear thinking about . Oh and a vertical prop on a tailwheeler will be just about right height to damage ones gentlemanly nether regions if you walk into it ! But you might just be lucky and only get your teeth broken when you walk into the spinner
But if you really want to re-open a three year old thread , I really haven't a clue why an Evra prop in a nice dry hangar would benefit from being vertical instead of horizontal . My Chris Lodge will definitely be resting horizontally. Except for when I'm flying it.

[G.Dawes]

I think it goes goes way back in French aviation mythology, and refers to being unlucky during the WW 1
something to do with chance.

[Brian Hope]

When preparing the article on overhauling constant speed props it was pointed out that you should not leave one with a blade vertical if parked outside. Rain will run down the blade and could find its way past the hub/blade seal and cause corrosion inside the hub. It is recommended that they be left horizontal, regardless of whether they are wood or metal.
On fixed pitch wooden props I'd go with the moisture absorption theory from when protective coverings were less effective than they are today. I've always left my prop horizontal and it has never caused me a problem - luck, good management or old wive's tale I don't really care, if it works why risk doing it differently?