Diesel setback??

Mike S · #1 12-02-2008, 08:47 AM

I just got this from AOPA, should be interesting to follow how this plays out.

Big question to me is-----is this a legit concern, or is it just a bit of posturing to place them in a "we told you not to do that" position for legal concerns should a problem arise in the future???

Be sure to click the link it the first paragraph.

N941WR · #2 12-02-2008, 09:04 AM

I really like the comments regarding freezing points.

What about all the turbo props out there that don't go fast enough to have aerodynamic heating of the wings?

What a line of BS!

captainron · #3 12-02-2008, 09:28 AM

Turboprops heat the fuel through a heat exchanger heated by the oil supply before sending the fuel to the burners.
In RV's, though, it always gets down to how much extra weight (and corresponding loss of useful load and performance) you're willing to give up- while usually paying extra for the privilege.

rv6ejguy · #4 12-02-2008, 09:58 AM

Just covering their butts and when the type certificate testing was done, the fuel may well have met different specs from today. Exxon clearly does not want the potential liability from such a minute user. If I remember right, the Thielert does have a fuel heat exchanger but I'll check on that.

Diamond has a lot more to worry about with the Thielert engines really being a disaster for them. We can only hope their new engine design works and lasts a lot better than the Thielert.

Geico266 · #5 12-02-2008, 10:11 AM

Gelling of diesel fuel is a "real" problem. I can attest to the fact that diesel will "thicken" and cloud up forming ice crystals at low temps (under 30F) as I use a diesel truck as my daily driver. Below 0F the ice cryistals can pug filters in a hurry. Even my truck has a fuel filter heater in it to warm the fuel so it will pass though the filter. You can design a system to work with diesel fuel or jet "A" but you need to be fully aware of what can happen with "oil" fuels. Certainly, this is a CYA article, but for very good reasons.

JMHO.

Top_prop · #6 12-02-2008, 06:58 PM

Quote:

Originally Posted by Geico266

Gelling of diesel fuel is a "real" problem. I can attest to the fact that diesel will "thicken" and cloud up forming ice crystals at low temps (under 30F) as I use a diesel truck as my daily driver. Below 0F the ice cryistals can pug filters in a hurry. Even my truck has a fuel filter heater in it to warm the fuel so it will pass though the filter. You can design a system to work with diesel fuel or jet "A" but you need to be fully aware of what can happen with "oil" fuels. Certainly, this is a CYA article, but for very good reasons.

JMHO.

the article was addressing jet fuel only... unless I missed something...

I too drive a diesel daily, have run bio diesel and I also fly turbines exclusively... modern jet fuels are much more than just refined kerosene... they contain additives for everything from controlling water, to lubricating fuel pumps... to controlling biologic growth. I don't think it is a small issue that the article is addressing Jet A and Jet A-1 fuel, which apparently has been certified with the aircraft and the fact that a fuel manufacturer has issued a warning for its use... diesel is not purported to be an approved fuel

JHines · #7 12-02-2008, 07:53 PM

It is more than simply an indemnity. The way it is drafted it looks like the FBO would be in breach for fueling a Diesel aircraft with jet fuel.

Basically guaranteed to scare FBOs off from fueling little Diesel aircraft out of fear of losing their supplier for sales to turbine-powered aircraft.

Andy_RR · #8 12-03-2008, 05:03 AM

The major issue appears to be that JET-A/A1 is not regulated for cetane.

Someone I know, who knows aero diesel engines rather well rang up his contact at Exxon Mobil to ask for the score. Allegedly, there was some surprise and aback taking when it was pointed out to whoever drafted the notice that:

a) turbines have lubricity requirements for fuel pumps etc too, and

b) the Centurion engines have a fuel heat exchanger

The notice appears to be something of a legal CYA, but I suspect that the FAA will need to nail a relatively conservative cetane requirement for JET-A/A1 in concert with a few other interested parties. They have allowed certification of the Thielert through for use on such fuel...

Apparently kerosene fuels will unlikely be less than 30, but that's pretty bad for most diesel engines. The issues surrounding cetane in aero engines are mostly related to cold start and altitude restart, with altitude restart being the big safety bogey.

Just what I've heard, FWIW.

A

JetA4GA · #9 12-03-2008, 05:59 AM

The cetane index is the only grey area which would required the JET-A/JET-A1 standards to be added a min cetane index check; IMHO this added test should not be perceived on the price at the pump. Nevertheless, after over 1.5 Mhours of in service experience using Jet fuels around the world, there is no known service difficulties reported, so...

On the known certified brands, lubricity testing has been done with fuel meeting the minimum jet fuel lubricity specifications (the SMA fuel pump/injectors exceeded 30 000 hours with no issues, i.e. many many times the TBO !).

Gelling: Another invalid concern; With all airworthiness authorities this was evaluated for the engines and airframes wrt the minimum gelling points specifications (if I recall -41?C (-41.8?F) for JET-A and -47?C (-52.6?F) for JET-A1). Further, to define the restart envelope in 2005 we have done engine inflight cold soak/restart testing with the SMA engine (gravity feed on the C182 we used) in Northern Canada with OATs below -35?C using JET-A1. Further, the SMA installations do not return the hot fuel to the thanks but rather work on a firewall forward fuel recirculation. Note also that the Cessna 406 Caravan II and Cessna 208 Caravan are certified to use JET-A up to 30 000 feet (pretty cold there !) and don't have limitations and speeds that could get you to benefit from any Ram Rise (note that where the fuel is in a wing is surrounded by air at temperatures lower than the free stream OAT - because of the lower static pressure which keeps you up there !). So all that Exxon **** is just pure CYA and talk about what they appear not to know. I hope they still know how to make aviation fuels !

The only reason I see why Exxon came out with this is that they are about to barely meet the jet fuel specs using carpy products which they know will not meet the needs of diesel engines, that to likely squize more money on the barrel (they have to make-up the recent losses!).

JetA4GA · #10 12-03-2008, 06:10 AM

Note also that SHELL has been supporting the SMA program wrt Jet Fuel and lubrication oil and, they never raised any issues but rather the opposite;

Also, Exxon seems to be the only one jetfuel maker onthat quest against aero diesels !

When a SHEEL reseller is taking its fuel from the Exxon tank at an airport, will they have to carry over that limitation from Exxon ? I guess not.