Field approval for prop

[frfly172]

How hard is it to get afield approval for a three blade composite prop to replace a two blade prop?

 

[Ted]

I've not done it, but when I asked Hartzell about a field approval for new props on my 310 they said they've never seen it happen on a twin. Might be more doable on a single.

There's more involved with prop selection than most realize. Although back in my engine test days we just threw on whichever prop was convenient (nothing flying or certified) to do it right you need to do a vibration survey to make sure you know which realms to avoid, etc.

Rather a shame, since I'd really like to get newer design props. Might gain a little speed, almost certainly reduce noise.

 

[flyingron]

The climate these days at the FSDOs is heavily biased against field approvals as we knew them in the past. It almost takes a DER these days/

 

[Tom-D]

The climate these days at the FSDOs is heavily biased against field approvals as we knew them in the past. It almost takes a DER these days/

Show me any directive supporting that statement.

AC 43-210.

 

[KRyan]

Ron's right, it's not as easy as it used to be, but if you can provide data to the FSDO, the process is easier.
First of all, I'd suggest looking at the Type Certificate Data sheet for the propeller. Near the end of the TCDS is "Note 9" information. This "Note 9" data shows propeller/engine combinations that are vibrationally approved. If the prop/engine combination is present on the Note 9 data, that's one less hurdle you'll have to overcome. Vibration approval is pretty costly to obtain. That's one reason it's hard to get a field approval on a twin, because the Note 9 data is restricted to single engine, tractor aircraft.

Another way to do it is to see if someone has an STC on the same engine on a similar aircraft. If you want to PM me, I'll take a look at what you want to do and see if there is a clear path.

 

[flyingron]

Show me any directive supporting that statement.

AC 43-210.

Order 8900.1. It specifically disclaims field approvals for things that correspond to major alterations though it tells the inspectors not to second guess the DERs too much.

 

[mondtster]

There's more involved with prop selection than most realize. Although back in my engine test days we just threw on whichever prop was convenient (nothing flying or certified) to do it right you need to do a vibration survey to make sure you know which realms to avoid, etc.

Having done a fair amount of vibration testing and surveys on engines, that is the part I would probably worry the most about. The equipment needed to perform the testing would probably be cost prohibitive to acquire to gain a field approval, and I don't know how comfortable I would be with not knowing.

 

[Henning]

I've not done it, but when I asked Hartzell about a field approval for new props on my 310 they said they've never seen it happen on a twin. Might be more doable on a single.

There's more involved with prop selection than most realize. Although back in my engine test days we just threw on whichever prop was convenient (nothing flying or certified) to do it right you need to do a vibration survey to make sure you know which realms to avoid, etc.

Rather a shame, since I'd really like to get newer design props. Might gain a little speed, almost certainly reduce noise.

Doesn't MT have a set of props for you?

 

[Tom-D]

Order 8900.1. It specifically disclaims field approvals for things that correspond to major alterations though it tells the inspectors not to second guess the DERs too much.

The only field approval I have had a problem with is one on a flight control mod.

You give them the right data stated in a way that they can understand and it will get approved.

I simply wish the ASI's still had authority to approve engineering as they did in the distant passed.

 

[frfly172]

I have an mt composite.not happy with customer support or warranty.Had a leading edge separate in flight while IMC MT can't explain what happened and charged full price for an overhaul.also have had the paint separate from prop if I fly in the rain.MT has an attitude last time the paint separated they said I must have taxied in gravel.dont feel comfortable with their prop.

 

[KSMooniac]

I had the same problem with paint shedding on my new MT prop, and it took a lot of griping to get it fixed. First try was a local repaint at an MT service shop/distributor. That shed immediately in the rain, and then MT sent a set of overhauled blades to replace my set. I wasn't happy getting overhauled blades to replace my <100 hour new ones, but that paint has held up better. Their design choice is utterly stupid regarding how they paint... nothing sticks to stainless, especially paint, yet they choose to bodywork the stainless edges and paint over the top instead of simply painting the blades and then installing the stainless leading edges. Leaving an exposed paint edge right where it faces the airstream is a very bad design choice!

 

[Ted]

Having done a fair amount of vibration testing and surveys on engines, that is the part I would probably worry the most about. The equipment needed to perform the testing would probably be cost prohibitive to acquire to gain a field approval, and I don't know how comfortable I would be with not knowing.

I've done enough to be comfortable with certain combinations. Furthermore, the manufacturer does have a good idea about these things.

Doesn't MT have a set of props for you?

I wanted more efficient and quieter, not less efficient, louder, and less reliable.

 

[RotorAndWing]

I wanted more efficient and quieter, not less efficient, louder, and less reliable.

 

[frfly172]

Can't express how unhappy I am with mt props have had prop repainted three times and prop continues to she'd paint. You can always buy a new prop.