View Full Version : Purpose of propellor protection film?
When the Hoffman propellor for my Grob was returned after overhaul, there was a piece of black self adhesive film in the package - "erosion tape". It is to be applied on the leading edges of the inner 30 cm of each blade (the blades are about 65 cm long).
In my experience erosion, wear and dents mainly appear on the outer part of propellor blades.
However, many propellors obviously have some kind of black leading edge cover on the inner part of the blades.
So, I wonder, what is the purpose of these covers and why are not the full "span" of the leading edge covered?
stevef
3rd Jan 2012, 19:42
De-icer boot protection - stone damage will expose the heater mat element.
Labour-intensive to replace, hence the tape.
By inner part do you mean the bit that looks as if it faces back towards the cowling?
If so, bear in mind that this is the bit that is actually the front of the blade. When you fly in the summer, this is the face that gets plastered with flies. In the same way, while the leading edge does get hit hence the use of prop tape, this inner face gets the brunt of impact damage.
At least, that's how I understand it. I've cleaned a lot of props, and the "back" face is always the fly graveyard.
peterh337
3rd Jan 2012, 20:46
many propellors obviously have some kind of black leading edge cover on the inner part of the blades.
It can be the prop heater element, on an electrically deiced prop.
Or it can be a piece of grooved rubber which guides TKS fluid up the prop blade (which is what I have).
The sticky tape, I don't know about.
Huv
I assume you own a Grob 109 if your prop is the blades are only 65 cm long.
This being the case the tape is nothing to do with anti-icing, or protection of the back of the blade.
The black tape is applied to the inner leading edge of the blade. In other words from the hub outwards. Im surprised it wasnt applied by your overhauler.
It is to protect the leading edges from damage.
If you wish to pretect the outer part of the blades a clear tape is used. We merely order Prop Tape from our maintainers. Im afraid I do not know the formal title.
You often see it overlying the black tape.
Do not apply in the winter, or of you so, then make sure it is done in a warm environment, otherwise it will detach in flight!
Nothing is ever applied to cover the rear, black part of the blade, although the previously mentioned black tape will cover a few cm's.
Again, Im surprised none of this was attached during overhaul (ours always is) as applicaton can be rather specialist.
It also affects balancing.
Thanks to all of you. No, there is no heating of the blades.
UV, you are spot on. It is a 109. I guess the overhauler would give us the choice - the black tape is optional. You are also right about clear tape apparently used for the outer half of the blades, but the overhauler didn't send any of that.
I still wonder about black vs white, and why protect inner but not outer part of the blades.
Thanks for the tip about not applying in cold temperatures!
I still wonder about black vs white, and why protect inner but not outer part of the blades.
Most blades have the black tape to help protect the inner part of the blade.
Some operators do not like to cover the rest of the blade with the clear tape as they think it adversely affects the performance, and because it tends to need replacing every few months. Obviously it is travelling much faster than the inner part of the prop! It has to be attached very carefully and NOT around the curved, outer part, of the blade.
I believe in having it there and accepting the very slight reductution in performance, versus the damage which could occur if the prop picks up a large stone.
Its up to you and depends mainly on the types of surface you operate from!
BackPacker
7th Jan 2012, 12:38
Obviously it is travelling much faster than the inner part of the prop!
On the other hand this means that the same stone can do a lot more damage to the outer portion of the blade, so the need for protective tape is much greater there.
huv
I forgot ..if you fly in rain you really should have the tape applied. It can do a lot of damage to the blade.
I find even light rain can remove paint on the G109 prop so we avoid it like the plague.