Prist Additive Not Recommended

[Colin]

I was following the report of someone ferrying a DA42 and was surprised to see them write about stopping for fuel and having to move to the next airport because the JetA at the first place had Prist additive, which was not recommended.

What are DA42 pilots doing about this? Is it common to have to call ahead to check if all the JetA has the additive already in it?

[gfuller]

I thought prist was recommended and it did not make a difference...

[Colin]

This blog entry:

http://aviationmentor.blogspot.com/2012 ... craft.html

Had this paragraph:

Arriving at Council Bluffs Memorial Airport (KCBF) we discovered the only Jet-A available contained PRIST, something not allowed for the DA42. Oh, bother! A few phone calls and we were headed to nearby Eppley Field (KOMA) where the fine folks at Signature topped off the main tanks with unadulterated Jet-A. Thinking ahead, we called the FBO in Cheyenne and found their Jet-A was premixed with PRIST, too. Several calls later, we decided that our next stop would be need to be Denver Centennial where we would once again visit the nice folks at Signature.

That surprised me. Are you saying that you heard the reverse, that it IS recommended?

[jon1746]

I just asked John @ A&M in Chicago this very question. He did not have a problem with Jet A with Prist.

[galaticsmurf]

We've used prist on occasion in our DA42NG, it's not mentioned in the AFM, but it does appear in the Austro AE300 Manual on page 3-12:

OPERATION WITH ANTI-ICING FUEL ADDITIVE:
The application of the following additive is allowed for an operated engine:
PRIST Hi-Flash max. 150 ppm Any mixture of the different types of additives is not permitted.
PRIST Hi-Flash anti-icing fuel additive is only allowed in operation with Jet A, Jet A-1 (ASTM D 1655) and JP-8 (F34).
If operating the engine with PRIST Hi-Flash anti-icing fuel additive, the specifications of the manufacturer must be adhered to.


[Chris]

This older thread indicates that it's OK to use on the Thielert models.

[carym]

There is another "problem" with the use of PRIST for anti-icing. This may be obvious but it has caused problems with other planes. If you ever use PRIST as a method to prevent icing in the fuel system, you will have to always use PRIST every time you re-fuel. This is because the concentration of PRIST in the fuel system has to remain as prescribed. If you re-fuel without PRIST then the concentration will be lower than needed, and you will not know the concentration so that you will have no idea how much PRIST to add at the next re-fuel to get it up to the correct amount. As I said, this problem has brought down other turbines who re-fueled without PRIST and then re-fueled again with PRIST thinking that it would prevent fuel icing. Because the concentration wasn't high enough, the engine quit when the fuel system iced up.

In general we shouldn't have the icing problem because the fuel system in the DA42 is heated. But, that is not the case for all fuel systems running on JetA fuel.

[gfuller]

the field I am at adds prist as the temp changes, and removes it for the summer months..the trucks have the option to turn the prist pump on or off

[exhibition]

PRIST Hi-Flash max. 150 ppm Any mixture of the different types of additives is not permitted.


The Austro AE300 Operation Manual actually states 1500 ppm just for the sake of completeness.

--

J. Benjamin Leeds
42.118 DA42-NG N153TS
Exhibition Aviation
Sun Valley, Idaho | Seattle, Washington

[Colin]

I always request "JetA, negative Prist." This weekend at KHIO it was fueled positive Prist, but they didn't charge me for it, since it was their mistake.

I googled and re-read some of these posts, so I wasn't worried, but I did wonder if it affected the performance of the engines at all. Does anyone know? Or is the additive in such a small quantity that it doesn't matter in combustion?