The International Cessna^® 170 Association

I was wondering about what people use for fuel anti-icing in the winter ?
I have read that lycoming engines are approved for low flow prist,@ 0.15%,.. but I cannot find anything
from Continental ?

Anything else people use ??

Thanks John

The Type Certificate Data Sheet specifically prohibits alcohol in Cessna aircraft.

TCM SIL-99-2B states : Under certain ambient conditions of temperature/humidity, water can be supported in the fuel in sufficient quantities to create restrictive ice formation along various segments of fuel system. To alleviate the possibility
of this occurring, it is permissible to add Isopropyl Alcohol to the fuel supply in quantities not to exceed 3
percent of the total.

Diethylene Glycol Monomethyl Ether (DEGMME) conforming to military
specification MIL-DTL-85470B, if approved for use in the aircraft fuel system by the aircraft manufacturer,
may be added for this purpose. The DEGMME compound must be carefully mixed with the fuel in
concentrations not to exceed 0.15 percent by volume.

WARNING: Mixing of the DEGMME compound with the fuel is extremely important because concentration
in excess of that recommended (0.15 percent volume maximum) could have a harmful effect on
engine components. Use only blending equipment and procedures that are recommended by the
manufacturer to obtain proper proportioning.

Therefore, reading between the lines, I'd use Prist not to exceed .15%.

Keep in mind that icing particles are most hazardous in fuel injected aircraft, not carbureted engines such as in 170's.
This is because: 1) the fuel-feed system to our engines first pass thru a gascolator which floats/removes ice particles, and 2) the carb and gascolator are both sitting in a warm-air area of the downdraft cowling system.

In cold weather, be certain to drain sumps AFTER each flight to remove any water from sump areas, lest it freeze and lock the drains.

I was wondering what the 170 guys in Alaska use for fuel anti-icing ?

Also what the cut off temp was for 170 flying was ??

The local flying school here stops flying below -25c.

I use the red bottle of HEET (isopropyl) in Alaska. One bottle in each tank when ice formation is favorable.

My personal temp cut-off is -20°F for flying any single engine airplane and that is probably too cold if something happens and a forced landing has to be made. Below 0°F any injury such as a broken bone or bad cut caused by a forced landing may well be fatal where it would only be an inconvenience in warmer weather.

The airplane itself starts doing weird things below -20°F. The engine might not start at all or catch on fire due to over-priming, if it does start it might run rough no matter what you try, hinges bind up, controls are stiff, hydraulics are sluggish as in the case of hydraulic wheel skis, windows fog up inside and freeze so visibility is restricted, heaters can't keep up and the cockpit temp approaches ambient, passengers complain, and it generally is no fun.

jatkins wrote:...Also what the cut off temp was for 170 flying was ??...

Minus 75-C.

Trivia question: What is the maximum barometric pressure it can fly?

gahorn wrote:

jatkins wrote:...Also what the cut off temp was for 170 flying was ??...

Minus 75-C.

The freezing point of 100ll, I presume? The following link to ConocoPhillips 100LL "marketing specifications" lists the freezing point as -58C (-72.4F).
http://www.phillips66aviation.com/pdfs/COPAvGas1406.pdf

Actually, if standard brake fluid (MIL-H-5606) is used, the limit is -65F. http://kparts.com/beta/?p=research&quer ... ulic_fluid

Miles

Most aircraft list in their limitaions sections of POH or AFM the temperature limits for operations. The 170 does not, but it's fairly common for FAR Part 23 and 25 airplanes to do so. Typical limits of several airplanes I have manuals for (and it seems to have no common thread as far as mfr), are:
Minimum for starting without pre-heat: -40C.
Minimum fuel temp: (dependent on fuel type, but -34C is common.)
Minimum for enroute flight: -75C.

No takers yet on the maximum barometric pressure for flight?

The answer is 31.00 inches of mercury per FAR 91.144. This is a regulation that i had read in the past but never understood. That was until a few months ago on a long cross country. I found the information in the Alaska supplement.
"a. Cold, dry air masses may produce barometric pressures in excess of 31.00 inches of Mercury. Most altimiters do not have an accurate means of being adjusted for altimeter settings of these levels. "

George,

In your above comment, "THE MINIMUM TEMPERATURE FOR STARTING WITHOUT PREHEAT= -40C"---- how in hell do you get the thing to rotate?
I spent four years in Fairbanks, Alaska, sixty years ago. -40c in those days was also -40f, and I dont remember any engines other than jets that we ever even attempted to start without preheat at that temperature. On my Stinson L-5, I used an engine tent, a plumbers fire pot and a can to heat the oil in.

Out here in California our Mogas comes with 5% alcohol already mixed in. Ice wouldn't DARE form in it!

What in the world did they do in the 40s in Alaska prior to 91.144? I believe they flew.

mod cessna wrote:The answer is 31.00 inches of mercury per FAR 91.144. This is a regulation that i had read in the past but never understood. That was until a few months ago on a long cross country. I found the information in the Alaska supplement.
"a. Cold, dry air masses may produce barometric pressures in excess of 31.00 inches of Mercury. Most altimiters do not have an accurate means of being adjusted for altimeter settings of these levels. "

Correctomundo! (And the additonal reason is because assigned altitudes no longer provide adequate separation.)

blueldr wrote:Out here in California our Mogas comes with 5% alcohol already mixed in. Ice wouldn't DARE form in it!

Of course, that would be ethanol and the TCDS absolutely prohibits such alcohol-based fuel. The only alcohol approved for fuel anti-icing is isopropyl. (And BEWARE! that's not the 70% stuff you find on drugstore shelves which contains water and glycerin.)

blueldr wrote:George, In your above comment, "THE MINIMUM TEMPERATURE FOR STARTING WITHOUT PREHEAT= -40C"---- how in hell do you get the thing to rotate?

Answer: Me? I don't. I was just quoting the limitations within the manuals of some aircraft.

Maybe just a nit regarding 91.144, but the way I read it, if the FAA does not issue a NOTAM restricting flight in some way, it's still legal to fly when the pressure is above 31 inches.

So what it means to me is that if I see METARs or forecasts indicating pressures near 31", I should ask Flight Service specifically if there are any NOTAMs restricting flight at my point of departure, destination, or along my route. As long as there are none, I think I'm good to go, and even if there are, I just need to make sure I'm not violating them in any way.

Have I got that right, George?

Nope. Unless a notam is issued providing conditions for certain flights, then ...no person may operate an aircraft...

Here's the rule:
91.144 Temporary restriction on flight operations during abnormally high barometric pressure conditions.
top
(a) Special flight restrictions. When any information indicates that barometric pressure on the route of flight currently exceeds or will exceed 31 inches of mercury, no person may operate an aircraft or initiate a flight contrary to the requirements established by the Administrator and published in a Notice to Airmen issued under this section.

(b) Waivers. The Administrator is authorized to waive any restriction issued under paragraph (a) of this section to permit emergency supply, transport, or medical services to be delivered to isolated communities, where the operation can be conducted with an acceptable level of safety.

George, I must be missing something here. Doesn't the phrase "contrary to the requirements established by the Administrator and published in a Notice to Airmen...." modify the verbs "operate" and "initiate"? In other words, I believe it's saying I may not make a flight contrary to a published NOTAM.

How are you interpreting the "contrary...." phrase?

John