IPA Winter Ops

[V1VRV2]

Getting some supplies for winter flying up north. Won’t be long before we get freezing temps and snow. We get temps up in Northern NY as low as -30’s. Mooney Ovation POH states up to 3% iso-propyl alcohol can be used in the fuel as antifreeze. Is adding IPA the norm for winter ops? 

[carusoam]

Following the POH is highly admired... 

Don’t be too soon... a good dry alcohol can easily get saturated with water if opened...

Ovation POHs are very current...

PP thoughts only, not a mechanic...

Best regards,

-a-

[neilpilot]

I frequently used IPA during winter ops in my M20E, and somewhat less often in my M20C.  However, that 3% max seems a bit high and I'd consider limiting IPA to 1%.

 

 

[kortopates]

It only takes enough to absorb the bit of water you may have in your wing(s). A pint should be much more than enough! It’s not good for internal seals so I would avoid using it prophylactically, and would wait till you really have reason to need it. I have never found water in my tanks and only rarely used it the last couple decades flying high in the winter.

That said a Mooney went down last winter from water in their tanks after it sat out in the rain with cracked o-rings. The bigger problem was the pilot departed without sumping the tanks after the rains. A 3% solution probably wouldn’t have made any difference there. But my only real point is our first defense should be to keep our tanks dry and then IPA should not be necessary except on rare occasions.


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[neilpilot]

30 minutes ago, kortopates said:

I have never found water in my tanks and only rarely used it the last couple decades flying high in the winter.

There's a real danger in departing toward very cold conditions with relatively warm fuel.  Water that's in solution when the fuel is warm will form fine ice crystals that can blind fuel filters after the fuel cools down.  You might not find water when you sump your aircraft in Memphis, but then head north into a huge in temperatures.

There's even a risk in refueling from a warm supply in an area that's just experienced a severe cold snap.  No water separation but ice crystals forming as cold wing contacts the warm fuel.

[kortopates]

19 minutes ago, neilpilot said:

There's a real danger in departing toward very cold conditions with relatively warm fuel.  Water that's in solution when the fuel is warm will form fine ice crystals that can blind fuel filters after the fuel cools down.  You might not find water when you sump your aircraft in Memphis, but then head north into a huge in temperatures.

There's even a risk in refueling from a warm supply in an area that's just experienced a severe cold snap.  No water separation but ice crystals forming as cold wing contacts the warm fuel.

I know its real, because I see a fair amount of it through my Savvy clients - but I've never seen that bad of a case of it either. But as an avid season pass skier for many years departing the banana belt of southern California for  Mammoth Mountain in our Sierra's and cruising at least at 16.5K well above the freezing level I haven't had a hiccup since I've had my plane hangared after the first couple months and learned about keeping my tanks dry. I really don't believe there is risk of fuel becoming saturated with water unless there is more moisture than just humid air in the tanks.  

AC 20-125 Water in fuel.pdf

Edited August 8, 2020 by kortopates

[kortopates]

@neilpilot I owe you a retraction and an apology. You really encouraged me to dig deeper since I was going by mostly my own experience here yet I know what you said is true, I just didn't believe it was that much of a threat. So I checked in with Mike B, since he's got 50 years flying experience, mostly Turbo, and has probably heard it all. He told me there is a real risk of dissolved (undrainable) water coming out of solution at low temperatures and freezing into ice crystals that can cause engine stoppage. He knows of several emergencies that occurred because of this, although it's definitely not common. Mike says these incidents don't occur in the wintertime as far as he knows. He says the major risk is taking off from a low altitude airport where the temperature and humidity are high and the fuel has become heat-soaked because the aircraft has been sitting in the sun for some hours, then climbing up to the Flight Levels where the OAT is very cold. It takes very hot fuel that can hold a lot more water in a dissolved state (as you pointed out before). The conditions leading to this issue have always been summertime conditions though, not winter. 

Mike B though has also never added IPA or even the low flow Prist (EGME) to his engine, but stated if he really thought he needed some, it would be his preference to use the Prist rather than IPA because it only takes very little Prist to do the job.

I'll add Mooney says to use IPA, they started out saying 3% was okay in the K's, but later with the Bravo they dropped it to say a max of 1%. Even that is much more than what should be needed for a little water.

Thanks for encouraging me to look into this further.

[V1VRV2]

Might as well add1% IPA. It’s not too expensive or too much weight to carry around a gallon in the baggage compartment and I’ll be covered. Better to er on the side of caution. If I’m in FL in December and head back to NY I might be in that situation. POH says no other additives are approved so Prist is out.

[aviatoreb]

17 hours ago, V1VRV2 said:

Getting some supplies for winter flying up north. Won’t be long before we get freezing temps and snow. We get temps up in Northern NY as low as -30’s. Mooney Ovation POH states up to 3% iso-propyl alcohol can be used in the fuel as antifreeze. Is adding IPA the norm for winter ops? 

Hi V1VRV2 - North Country, NY?  Where are you?  I am at KPTD.

For those that don't know - "North Country" is a phrase used in NY state for those few counties that are mostly the northern tier, rural, Adrondacks and north of the Adirondacks.  Here in KPTD to give an idea it is about 7 hrs drive to NY city and 1:20 to Ottawa Canada - or 25 min to the border.

Yes - I use isopropyl - about 1%. I  buy it in small containers so that it won't sit for a long time since even if you buy the 99.9% stuff you should buy, if it sits - even with the cap closed in its container - for too long it gradually picks up water from the air.

Edited August 9, 2020 by aviatoreb

[aviatoreb]

15 hours ago, kortopates said:

It only takes enough to absorb the bit of water you may have in your wing(s). A pint should be much more than enough! It’s not good for internal seals so I would avoid using it prophylactically, and would wait till you really have reason to need it. I have never found water in my tanks and only rarely used it the last couple decades flying high in the winter.

That said a Mooney went down last winter from water in their tanks after it sat out in the rain with cracked o-rings. The bigger problem was the pilot departed without sumping the tanks after the rains. A 3% solution probably wouldn’t have made any difference there. But my only real point is our first defense should be to keep our tanks dry and then IPA should not be necessary except on rare occasions.


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I agree it is not good for seals.

But I use it in the heat of the winter even for when the airplane is on the ground for a week or two - so prophylactically, since when it is -30F at night in the hangar - I do worry that when I sump that freezing water will prevent me from removing the water.

Anyway yes I use it generally for about 5 or 6 months of the year.  Its not just for flight level flying in the North Country.

[neilpilot]

9 minutes ago, aviatoreb said:

agree it is not good for seals.

Have you actually seen information regarding seal degradation resulting from 1% IPA in fuel?  Or could this be another OWT?

I’m interested because IPA is generally not aggressive toward many elastomers.   Now I see you and others possibly have information  to the contrary.

I used to make large quantities of 95%+ pure IPA and can attest that, unlike ethanol, it wasn’t particularly aggressive to most common elastomers.  If used as a 1% additive in 100LL I’d expect it to be even less of a concern.

[aviatoreb]

3 minutes ago, neilpilot said:

Have you actually seen information regarding seal degradation resulting from 1% IPA in fuel?  Or could this be another OWT?

I’m interested because IPA is generally not aggressive toward many elastomers.   Now I see you and others possibly have information  to the contrary.

I used to make large quantities of 95%+ pure IPA and can attest that, unlike ethanol, it wasn’t particularly aggressive to most common elastomers.  If used as a 1% additive in 100LL I’d expect it to be even less of a concern.

OWT - I know of no specific data that it is bad for the system, the seals or the sealant.  Its just folklore.

I don't know either way but that would be a chronic problem and I use it regularly as I said due to my northerly climate as a matter of safety of flight which is an acute issue that takes precedent over a possible chronic problem that is not even for sure a problem.

[philiplane]

If it's that cold, that you think you need IPA in your fuel, stay home and have a pint of IPA next to a warm fireplace...

 

https://www.totalwine.com/shop/best-india-pale-ales

[aviatoreb]

17 minutes ago, philiplane said:

If it's that cold, that you think you need IPA in your fuel, stay home and have a pint of IPA next to a warm fireplace...

 

https://www.totalwine.com/shop/best-india-pale-ales

Its glorious flying on a crisp winter's day especially when its white and bright and bluebird.  And the airplane performance is amazing.  Its also lovely to go XC skiing, skating on the lake, and...then yes sit by the wood stove and drink an IPA when its all done.

But seriously - the worry is yes if its -30F at night in the hangar then even if its say 10F during the day when I want to fly that if there are ice crystals in the fuel then they will still be there fully frozen.

Not to mention - if you fly when its 40F but you go up to 20,000 ft... it can be pretty cold up there.  I have heard stories of people getting ice crystals and then fuel flow blockage in high altitude flying even in warmer months.

[neilpilot]

2 minutes ago, aviatoreb said:

Not to mention - if you fly when its 40F but you go up to 20,000 ft... it can be pretty cold up there.  I have heard stories of people getting ice crystals and then fuel flow blockage in high altitude flying even in warmer months.

In the event that you loose engine power due to ice crystals, fuel flow can sometimes return as the aircraft descends.  Even if still in freezing temperatures, it's warmer under your cowling so long as the engine is still producing power. 

I'd guess there have been engine out incidents where no mechanical issues have been discovered.  If ice crystals cause fuel blockage, it could later melted and no probably cause is evident.

[MikeOH]

Will IPA (or PRIST) dissolve already present ice crystals, or does it need to be added to the fuel before exposure to sub-zero temps?

[jlunseth]

My experience is the same as Paul’s (Kortopates). I have a 231 that I have flown a fair amount in the flight levels in cold temps. The coldest I recall was -54 F on a trip from Williston to Flying Cloud. It was so cold the heater and defroster could not keep up inside the aircraft, and I logged IMC time even though the weather was CAVU, because there was no way to see out the windows.  I have used IPA from time to time, but have never found it necessary in cold climate flying. That said, if Mike B. says it can actually be a problem, I take that seriously. I buy it in pints at an autosupply store and keep some in the aircraft, I don’t think I would want a whole gallon sitting in the plane.

Usually the problem is self-solving. If it occurs when warm fuel is loaded and then taken to cold temps, that is not a common scenario.  Up here in the frozen north we fly from one cold airport to another cold airport. On occasion I fly from a cold airport (such as KFCM) to a warm airport (such as KGAD enroute to the Bahamas) in the flight levels. However the winds aloft virtually never allowing flying back up high where it is cold.  The 70 knot tailwind you had going south does not help in the other direction. Usually the warm-loaded fuel is long gone by the time I get home, and what is in the aircraft was loaded somewhere cold. That said, I put a pint in each tank when conditions warrant.  

The water-in-fuel scenario that Paul talked about is a somewhat different issue.  Because Mooney fuel caps are recessed, they sit in a well that funnels rainwater towards the tanks. The only thing stopping the water from getting in is good O rings. I have found as much as a pint of brownish water when sumping a Mooney tank, not my aircraft but a J I used to fly years ago. I keep my own seals in good shape, they are checked at annual every year, and I have never seen water in my tanks. For that matter there is a small O ring around the stem for the cap lock, if that goes you can get water in or fuel siphoning out.  The fuel siphoning out can be fairly dramatic looking, it comes spraying out of the cap because of negative pressure. If you don’t think the curved upper surface of the wing creates low pressure contributing to lift you should try that some time.  The 231 has antisiphon valves for this exact reason, they are a pain when fueling but the spraying, the one time it happened to me, is shortlived, just the cup or so of fuel above the anti-siphon plate. Nevertheless, Mooney gas caps are configured to favor water going in, so I always, and I mean always, sump the tanks after every re-fueling or if the aircraft has not been refueled but has sat for a period, especially outdoors. The only time I might skip it is if the plane was filled yesterday, I flew it and know the fuel is good, and then it went into the hangar overnight. It took some work to sump that gunk out of that J tank, and then it happened again the next time I flew it.  Ugh.

[aviatoreb]

45 minutes ago, neilpilot said:

In the event that you loose engine power due to ice crystals, fuel flow can sometimes return as the aircraft descends.  Even if still in freezing temperatures, it's warmer under your cowling so long as the engine is still producing power. 

I'd guess there have been engine out incidents where no mechanical issues have been discovered.  If ice crystals cause fuel blockage, it could later melted and no probably cause is evident.

I have read of such stories when I was researching the topic about 10 years ago when I decided to add IPA to my winter operations.

I am not confident to rely on a restart as a backup plan but I would certainly hope for a restart if I were in such a situation.

We don't always fly with above freezing temps on the ground, or anyway if the conditions are significantly below zero on the ground defrosting my not occur even if it would if only slightly below freezing.  Plus I worry about ice crystal blockage at intake in the wings - not knowing what I am talking about on this topic fully admitted - can we rely on a blockage occurring just inside the cowl where there may be engine heat?

Edited August 9, 2020 by aviatoreb

[jaylw314]

I think I recall doing a back-of-envelope calculation a while back, that in a 30 gallon gasoline tank, there can be about 2 tablespoons (30 cc) of water held in "solution" (I suppose it's actually more of a colloial suspension).  If you figure that IPA makes a 95% azeotropic solution with water, if you start with 100% IPA, that's 5% by volume of water it grabs.  So you'd need about 600cc of IPA, or basically a quart, if everything mixes perfectly and there are no other variables (and if it actually works that way, which I'm completely uncertain).  That sort of jives with the 3% limit, which would be about a gallon of IPA in a 30 gallon tank. 

[carusoam]

So...

What do we know...

1) Water is soluble in gasoline... a small amount, something on the scale of grams per gallon....

2) The solubility of water increases with temp... or wants to fall out of solution as it gets colder... based on its saturation level...

3) IPA can improve the solubility of water greatly.... molecule for molecule....(sort of)

4) You can get a lot of water to dissolve in gasoline on its own and more with chemical help...

5) As fuel gets sprayed it starts to separate... fuel, water, alcohol... this trio can form a different equilibrium when changing from liquid to vapor state... if the water falls out of solution while the mixture is evaporating... there may be a snow storm occurring inside the fuel system somewhere...

6) If water causes a problem in fuel because cold temperatures make it less soluble... it may be a bad idea to have excess water in the system held in there with alcohol...
 

7) One thing to decrease the level of saturation... but another thing to absorb even more water by changing the solubility of the water...

8) On those really cold days... make sure all the rain water is gone before adding the IPA... 

 

So... the real question is... where do the water molecules fall out of solution, and what do they collect on...?

 

A follow-up thought... if 1% alcohol is good... then 3% must be better...  too many ways for alcohol to not be good... we don’t like it very much in our auto fuel...

Another thought... Alcohol and acrylic windshields And crazed surfaces go together.... alcohols and polymers are not always close friends... hard to know what the side effects can be until the testing is complete...

PP thoughts only, not a chemist...

Best regards,

-a-

[neilpilot]

9 hours ago, carusoam said:

too many ways for alcohol to not be good... we don’t like it very much in our auto fuel.

It's very important to understand that the ~10% ethanol in auto gas is very different from the ~1% IPA additive in 100LL.  Ethanol is generally much more aggressive towards some gasket & seal materials than IPA.  There are many other distinctions that invalidate comparing them as generic "alcohol".

Also PP thoughts, and not a chemist (but I am a ChemE  )

[carusoam]

Go MS engineers!
+1 for ChEs...
extra points awarded for mChEs

+2 for PhD ChEs...
 

Celebrating the varied knowledge base of all MSers!

 

Go MS!

Best regards,

-a-