Frozen avgas

[Will.iam]

Yes the frost on the bottom is from the super cooled fuel. Sometimes called hoar’s frost. I get it just about every time i come down quickly from the flt levels especially wjen the humidity is high like here in texas in the summer. 
jet fuel starts to freeze at -56c and jets fly up in the 30,000 to 40,000 where the temp is way colder than what you will be subjected to at 25,000 and rarely after a 5 to 6 hour flight we might be getting close to the fuel temp getting to -54c where we have to start doing something about it either fly faster to get more heat from air friction or descending  to warmer FL’s so with AVgas being -57c it definitely wasn’t the gas freezing. You had water in the fuel that froze. 

[JimMardis]

Thank you very much for posting this experience. I know that many will add comments about what you may have done wrong or what you could have done. All of the information is very useful and helpful and goes to show what could happen. I am new to flying an Acclaim (less than a month). My real job is flying Bombardier Globals. I have been paying attention to what it looks like to be flying unpressurized, using O2 in the 20s. I do admit the thought is scary to me. So I have been developing a Quick Reference Card with Emergency Procedures on it for cases like this. One thing that is not mentioned to do by Mooney is to pull the gascolator ring airborne to dump out any water that might have collected there. I had that happen to me 35 years ago in a C172 that you could drain from the cockpit as well and it immediately cleared up my engine roughness. I believe I will add pulling the Gascolator Ring to my checklist.

Here is a copy of my Emergency QRC I have been working on.


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[James McDiarmid]

Thank you very much for posting this experience. I know that many will add comments about what you may have done wrong or what you could have done. All of the information is very useful and helpful and goes to show what could happen. I am new to flying an Acclaim (less than a month). My real job is flying Bombardier Globals. I have been paying attention to what it looks like to be flying unpressurized, using O2 in the 20s. I do admit the thought is scary to me. So I have been developing a Quick Reference Card with Emergency Procedures on it for cases like this. One thing that is not mentioned to do by Mooney is to pull the gascolator ring airborne to dump out any water that might have collected there. I had that happen to me 35 years ago in a C172 that you could drain from the cockpit as well and it immediately cleared up my engine roughness. I believe I will add pulling the Gascolator Ring to my checklist.

Here is a copy of my Emergency QRC I have been working on.


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Thanks for sharing the checklist Jim! I certainly learned from the incident… my 99% isopropyl alcohol delivery arrived last week


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[LANCECASPER]

5 minutes ago, JimMardis said:

 One thing that is not mentioned to do by Mooney is to pull the gascolator ring airborne to dump out any water that might have collected there. 

On the ground whenever I pull the gascolator in pre-flight I visually check to make sure that it has stopped allowing fuel through. I've seen it a few times over the years when I had to fiddle with it to get it to stop. I would be hesitant to pull it in flight, not knowing for sure if the fuel has stopped.

[JimMardis]

That is a legitimate concern. If we are in an Emergency situation I will try to get the engine going again tho. Another, pic your poison scenario but an excellent point.


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[dkkim73]

5 hours ago, LANCECASPER said:

On the ground whenever I pull the gascolator in pre-flight I visually check to make sure that it has stopped allowing fuel through. I've seen it a few times over the years when I had to fiddle with it to get it to stop. I would be hesitant to pull it in flight, not knowing for sure if the fuel has stopped.

You know, it doesn't have a really positive return feel, does it? I've been in the habit of just draining a bit from each side for a few seconds in the run up area. Someone else mentioned the value of examining the drainage, also. Maybe I should figure out a pan or catch bucket type solution. 

[LANCECASPER]

49 minutes ago, dkkim73 said:

You know, it doesn't have a really positive return feel, does it? I've been in the habit of just draining a bit from each side for a few seconds in the run up area. Someone else mentioned the value of examining the drainage, also. Maybe I should figure out a pan or catch bucket type solution. 

I think someone beat you to it:

https://mooneyspace.com/topic/44958-gascolator-drain-technique/#comment-789299

[LANCECASPER]

On 5/26/2024 at 5:32 PM, James McDiarmid said:

 

Engine Out 4/5/24

Hi all, I had an engine failure 3 weeks ago and I thought I’d share it with you.

My wife and I were 2h into a flight from Exeter to Venice in the cruise at FL230 in my 2008 Mooney Acclaim-S. I bought my second Mooney last year - I’d previously owned an ovation 2GX but the allure of flying faster above the weather led me to purchase an Acclaim. During the flight the weather had been pretty good with the exception of the forecast tailwinds in fact being 50-60kt headwinds and consequently slowing our progress. We were in Belgian airspace and I was talking to Brussels control.

OAT was -32C as we surfed through smooth air in the tops of a thin layer of cloud into a 55kt headwind.

As usuaI was flying by the numbers - at best economy…

We were cruising 28.0” MAP 2300 RPM LOP @15.0gph

In retrospect the early indication of an issue was very occasional rough running which started 20 minutes or so before the engine stopped.

Also - oddly EGT/mixture was not ‘stable’ (the mixture seemed to automatically be getting leaner - EGT increasing above 50 degrees LOP - so I was watching it and enriching in). I had never experienced this before.

As a consequence of the LOP mixture instability I decided to run ROP which provided a little more stable EGT-wise until after around 10 mins the engine stopped abruptly.

At this moment I received the low manifold pressure yellow (?red) warning on G1000.

All 6 EGT/CHT immediately dropped to zero and the prop was windmilling. *I subconsciously monitor the sound of the engine during flight and for once it was notably absent.

The airspeed was rapidly decaying so I immediately deactivated the autopilot and pushed the nose down

while simultaneously declaring an emergency.

Brussels control acknowledged the mayday and asked what I needed, I requested vectors to the nearest airport ‘Ostend is 10 miles north of your position’ so I started a descending left turn to the north.

Boost pump selected and left on, I switched fuel tanks.

Brussels control handed me over to Ostend.

I kept the airspeed >100kts as we had a lot of height to lose and didn’t need to stretch the glide.

Blue (prop) and red (mixture) knobs pushed fully in, the magnetos were left selected to ‘both’ and not touched throughout the emergency.

Speedbrakes deployed as still very high.

We crossed the north Belgian coast approximately 8000ft, I was offered but unable to accept an ILS for rwy 08 as engine not producing power - I requested and was approved for a glide approach. Soon after this we became visual with the airport but were still very high so I selected the gear down and flaps to T/O. I created a track on the G1000 extending the centreline of runway 08.

We were very high on initial final approach ?3000ft…

Passing 1000ft I selected full flaps and instantly (?possibly related to attitude change going from 10-33 degrees of flaps) the engine burst back into life. I put the landing lights on, completed final approach checks and made a surprisingly smooth landing on runway 08. We were met and escorted to the GA apron by the fire crew.

The engine sounded normal again until shutdown.

On external inspection… there was no water in the fuel.

But there was around 5mm of ice on the underside of the wings.

There was no visible ice on the leading edges or upper surfaces of wings so I had not been using the TKS deice system.

Also the fuel tank vents were unobstructed.

The oil quantity was ok.

Fuel quantity was also fine - there was approx 30usg remaining per side confirmed visually. We took the train back to Exeter while the aircraft was inspected by a local shop. The engine data from the G1000 revealed FF dropping to zero as the event preceding the engine failure.

The aircraft was inspected 11 days later (such is life in Europe!) - they found some evidence of ‘a few drops of’ water in the gascolator but nothing else amiss. Even though the aircraft was always kept in the hangar I had fully fuelled the aircraft in light rain the evening before the flight and had strained both wing fuel tanks prior to takeoff but I have to admit I omitted to pull the gascolator drain. As you can imagine I researched the subject of freezing avgas in some detail and found several reports of similar incidents affecting piston aircraft that were cruising in the flight levels in very cold conditions.

The Mooney POH refers to this risk and recommends adding anhydrous isopropyl alcohol 99% purity to avgas to make around a 1% solution in order to remove any free water, lower the freezing point of avgas from -57C and prevent these situations happening.

Another friend who suffered a similar power loss in his TB21 feels it’s more likely due to the fuel servo icing up within the engine and considers that this is less likely to happen when the TKS system is active as some of the prop TKS fluid gets into the engine bay and prevents the tiny nozzles from icing over.

Two fellow European Mooniacs generously gave me a lift from EGTE to EBOS to collect my aircraft yesterday and after adding isopropyl alcohol to the fuel and a thorough ground run-up I flew home to Exeter with no issue.

Freezing avgas/water was not on my radar but is a very real issue… I’ll be straining tanks and gascolator and adding IPA for long/high/cold sectors throughout the year and getting into warmer air as soon as possible if I ever encounter similar symptoms. Having seen the normally unseen underwing ice after landing I’ll also have a lower threshold for switching on the TKS deicing system in very cold conditions.

Anyway - I learned that freezing flight levels can bite…

 

 

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Have you replaced the o-rings on your Acclaim (Newton 300) fuel caps? The Mooney Illustrated Parts Catalog has a note that says they should be replaced "every 5 years or with unusual wear". If they haven't been replaced water can get in.

Here's the kit for each fuel cap: https://www.aircraftspruce.com/catalog/pnpages/05-02218.php

 

 

[James McDiarmid]

Have you replaced the o-rings on your Acclaim (Newton 300) fuel caps? The Mooney Illustrated Parts Catalog has a note that says they should be replaced "every 5 years or with unusual wear". If they haven't been replaced water can get in.
Here's the kit for each fuel cap: https://www.aircraftspruce.com/catalog/pnpages/05-02218.php
 
 

Thanks and Yes - the o-rings were changed back in January when the plane was in for its annual. They have no cracks and no sign of wear. In retrospect think I just took on lots of very ‘wet’ fuel the night before the flight and the dissolved water crystallised out in the cold flight levels. I used to have a home weather station and humidity here varies between 60% and 100% - living in the southwest UK is like living on a pier extending into the Atlantic… ;-)


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[jlunseth]

On 6/3/2024 at 7:29 AM, LANCECASPER said:

On the ground whenever I pull the gascolator in pre-flight I visually check to make sure that it has stopped allowing fuel through. I've seen it a few times over the years when I had to fiddle with it to get it to stop. I would be hesitant to pull it in flight, not knowing for sure if the fuel has stopped.

I used to use the stem on a sump cup to sample fuel from the gascolator. Then one day on a trip out to MT the gascolator jammed open when I did that. I was able to close it by climbing into the aircraft and pulling the ring a couple of times, but I would hate to have it jam open in the air. Wouldn’t know what was happening until too late and it drains both tanks not just one.

I have to say, I don’t fly into the flight levels as much anymore as I did the first few years I had my aircraft. Many of my flights now are Angel Flights and I don’t want to take medically vulnerable passengers up that high. But I have flown in the cold a lot and in the flight levels a lot. Once as cold as -54 dF for a couple of hours. I used to put isopropyl in the tanks but quit doing it because I never had a problem with freezing water in the fuel. Now, if I were to fill up in FL where the fuel is sitting in a nice warm tank and could hold water, and then fly into hard core minus degrees further north I might think about it. But generally, the fuel is already cold on the ground. Not sayin’ don’t add the isopropyl, heck, maybe I will start doing it again, I still have quite a few pints left. But I put in a lot of hours up there with no iso and no freezing either.

[dkkim73]

On 6/2/2024 at 9:58 AM, kortopates said:

It has to be anhydrous. Anhydrous simply means no water in. Rubbing alcohol is 70% isopropyl and 30% water. You're looking for 99% Isopropyl - there is no such thing as 100%. 90% isn't anhydrous either with 10% water. 

Thank you, Paul. That one line about no added water clarifies the terminology! The whole thing also re-rang a bell and I just crawled out of a rabbit hole of vapor phase diagrams and reading about azeotropic distillation. 

[Ibra]

On 5/27/2024 at 12:32 AM, James McDiarmid said:

The Mooney POH refers to this risk and recommends adding anhydrous isopropyl alcohol 99% purity to avgas to make around a 1% solution in order to remove any free water, lower the freezing point of avgas from -57C and prevent these situations happening.

Another friend who suffered a similar power loss in his TB21 feels it’s more likely due to the fuel servo icing up within the engine and considers that this is less likely to happen when the TKS system is active as some of the prop TKS fluid gets into the engine bay and prevents the tiny nozzles from icing over.

Two fellow European Mooniacs generously gave me a lift from EGTE to EBOS to collect my aircraft yesterday and after adding isopropyl alcohol to the fuel and a thorough ground run-up I flew home to Exeter with no issue.

Glad all sorted out to collect aircraft and well done managing it 

Lycoming engines will tolerates 1% alchool (IPA) which is what people use to prevent fuel icing (I know one twin Aztec that went down). Mooney Service Instruction says max 1% for Lycoming altough goes for 3% in POH of some turbo models (M20K maybe as it goes to FL280?), the limit is likely for both engine run and long term integrity of fuel systemo

Not sure how if yours was fuel icing? it happens

https://www.euroga.org/forums/flying/3908-fuel-servo-icing

It could be an induction problem? I had the same in SR22 without propeller TKS de-ice, there is not much one can do, especially no mannual alternate air control...

https://www.euroga.org/forums/flying/4215-in-flight-icing-incident-in-cirrus-sr22t-fiki?page=1

The other thing on restart with powerful turbos, you are unlikely to be able to retart once it completely stopped. I think it needs to get back into "normally aspirated" enveloppe with dense air before it kicks again 

POH recomands fuel pump ON (and using mannual alternate air for induction), I wonder if the pump is for vapour pressure issues rather than frozen fuel servo. However, it will always help to keep fuel flow going 

TKS from propeller helps to prevent engine icing (induction icing or fuel icing that can happen even when clear of clouds without airframe ice), it's alchool isopropyl after all 

 

Edited June 11, 2024 by Ibra

[Pinecone]

On 6/3/2024 at 2:21 PM, dkkim73 said:

You know, it doesn't have a really positive return feel, does it? I've been in the habit of just draining a bit from each side for a few seconds in the run up area. Someone else mentioned the value of examining the drainage, also. Maybe I should figure out a pan or catch bucket type solution. 

Somebody designed a holder for a GATS jar.  You use a small spring clamp to attach it to the nose gear, and it catches the squirt.  My friend printed me one, but found the hole for the GATS jar did not fit, so he modified it.  

There is a guy at the airport is doing a small 3D printing Etsy store.  Maybe I should get him the print file and he can make and sell them.

[Pinecone]

6 hours ago, Ibra said:

TKS from propeller helps to prevent engine icing (induction icing or fuel icing that can happen even when clear of clouds without airframe ice), it's alchool isopropyl after all 

Engine induction maybe, but how does it prevent fuel icing????

And it is mainly ethylene glycol.  And if that gets into the induction and through the engine, it will look like you have an aerobatic smoke system.  Ever see a car blown a head gasket?

[neilpilot]

26 minutes ago, Pinecone said:

Engine induction maybe, but how does it prevent fuel icing????

And it is mainly ethylene glycol.  And if that gets into the induction and through the engine, it will look like you have an aerobatic smoke system.  Ever see a car blown a head gasket?

Agree. Also alcohol introduced into induction air will not help to dissolve ice crystal blockage in fuel system

 

[Ibra]

1 hour ago, Pinecone said:

Engine induction maybe, but how does it prevent fuel icing????

It help with engine sensor icing (if it's fuel servo icing of course)

If the fuel itself that is iced up in the pipes (not just at sensors or servos), well there is not much TKS can do (neither fuel pump or anything else for that matter)

In any case, it's hard to tell if it's an induction icing or servo icing or both? (unless you have oxygen sensors and dig all engine data on-the-fly right before the fan quits), we just throw propeller TKS on whatever ice forms out there in front of windshield, push fuel pump and change tanks, move engine controls and open alternate air: then hope for the best ! 

Edited June 11, 2024 by Ibra

[Ibra]

57 minutes ago, neilpilot said:

Agree. Also alcohol introduced into induction air will not help to dissolve ice crystal blockage in fuel system

Indeed, propeller TKS does not help with fuel blockage in reservoir or gascalator. However, it helps in other places and anyway TKS fluid never hurts an engine !

Edited June 11, 2024 by Ibra

[Ragsf15e]

On 6/4/2024 at 9:48 PM, James McDiarmid said:

Thanks and Yes - the o-rings were changed back in January when the plane was in for its annual. They have no cracks and no sign of wear. In retrospect think I just took on lots of very ‘wet’ fuel the night before the flight and the dissolved water crystallised out in the cold flight levels. I used to have a home weather station and humidity here varies between 60% and 100% - living in the southwest UK is like living on a pier extending into the Atlantic… ;-)


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Really nice job dealing with that emergency and leading this discussion.  I really hope your wife sees how great you did and agrees to keep flying with you!

[Jim Peace]

Those temp conditions are safest for multi engine jets. Jets usually have fuel temp indications and also fly fast enough to have ram rise friction temp increase to help fuel stay a bit warmer than OAT. Also jets have either fuel heaters or required to use prist etc. 
I would install a fuel temp probe in each tank being that one can have less fuel in it than the other unlike a jet. Also keep in mind if you touch clouds that they can be cooler than the OAT.
 

I notice all the time in jets that as soon as I hit the cloud deck even in level flight that more times than not the TAT can decrease by 5 or 10 degrees C. 
 

nice job getting the plane down. I love that Exeter airport and I have been through Ostend on some ferry flights.  
 

the coldest temp aloft I have experienced nearly -75c was over the equator south of Asia  And some of the warmer ones have been north of Russia. So sometimes what you think should be is not.  Fuel temp gauges would be a must if I flew a lawnmower with wings that high and cold with thinner aluminum than a jet. 
 

https://www.aircraftspruce.com/catalog/eppages/FBprist2.php

[James McDiarmid]

Acclaim N40AU had an almost identical engine out over Oregon a couple of weeks ago - landed safely on a road, checked the aircraft over (the pilot is an A+P/IA) let it thaw out for a few hours and took off again. 

[jlunseth]

On 6/11/2024 at 10:46 AM, Ibra said:

In any case, it's hard to tell if it's an induction icing or servo icing or both? (unless you have oxygen sensors and dig all engine data on-the-fly right before the fan quits), we just throw propeller TKS on whatever ice forms out there in front of windshield, push fuel pump and change tanks, move engine controls and open alternate air: then hope for the best ! 

My experience? Induction icing shows up initially as a persistent decline in MP as the air filter plugs with whatever is causing the blockage. Usually it is caused by flying through ice clouds which you find at high altitudes where the temp is very low so the droplets in the cloud freeze. I suppose snow could cause it also but I have flown through snow several times and not experienced induction icing. General icing I suppose could also cause it but I have not experienced that either, although I have only experienced airframe icing a few times and gotten out of it immediately. I suppose if you have TKS and fly in icing conditions long enough it could happen. Induction icing generally doesn't happen suddenly, it can take a few minutes for the filter to plug badly enough to reduce induction air flow. The 231, for those interested, has both a manual and an automatic system for the door. If I am high and start to see an MP drop that I cannot otherwise explain I operate the door rather than wait for the automatic system.

I can't say I have ever experienced fuel line icing thankfully. I haven't used alcohol for quite awhile, but when I did I used the isopropyl fuel antifreeze you can buy at any auto store. It is cheap. Was recommended to me by very experience Mooney people.

[FlyingDude]

I commend your airmanship.

Just thinking out loud. You said you found 5mm of ice under the wings. What if the tank vents got iced up? Clogged vents prevent the flow of fuel out of the tanks. Just a conjecture. 

[James McDiarmid]

I commend your airmanship.
Just thinking out loud. You said you found 5mm of ice under the wings. What if the tank vents got iced up? Clogged vents prevent the flow of fuel out of the tanks. Just a conjecture. 

Thanks Dude!
I considered that too - the ice under the wings was mainly inboard of the main landing gear and the tank vents had no visible icing or obstructions so I don’t think that was the cause.
I’ve been adding 1-1.5% IPA when flying high in similar conditions since the incident with no further issues.
Merry Xmas!


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