Spraying water into a hot engine

[GlennAB1]

I was referring to the temps involved and the rate of change to get it done. much greater that what occurred here.

You don't understand the word "shock" in "shock cooling"?

 

[PaulS]

Aluminum doesn't behave the same as steel in heat treatment. Overheating aluminum generally softens it and quenching does not generally harden it.

 

[RyanB]

IF I were the administrator, I'd include an engine management course requirement for each CPL/CFI's training.

I'm just amazed how situations like these are dealt with especially on the CFI's behalf. Sure there may not have been anything wrong with the airplane this time, but to think of a CFI thats extremely concerned about something he just witnessed but apparently doesn't care enough to inspect the engine and confirm there is infact no issue before flying home.. each to their own.

 

[GlennAB1]

Tom, what alloy are cast cylinder heads?

 

[Horse]

I think there's many more lessons to be learned here than that. Spraying a hot engine with water to make for an easier start is totally incorrect.

The evidence appears to not agree with you.

 

[Mike Smith]

The evidence appears to not agree with you.

Your n/1 study doesn't prove anything.

 

[PaulS]

The evidence appears to not agree with you.

Bad idea for many reasons, like electrical components, such as alternators magnetos, plug wires, sensors, all generally placed not to get direct hits from water that you soaked. Also not generally too smart to invent your own procedures in aviation, especially when you are student.

 

[GRG55]

During manufacturing processes the case and cylinder heads under go heat treatment much more severe that anything that can happen during usage.

Do they quench those parts by standing back and spraying water from a hose on them Tom?

[and just so there's no confusion, that's a rhetorical question]

 

[Tom-D]

You don't understand the word "shock" in "shock cooling"?

Maybe we can have you explain how shock cooling can happen in this case where the engine is WAY below operating temp.

 

[Tom-D]

Do they quench those parts by standing back and spraying water from a hose on them Tom?

It's a lot more severe than that, and a lot quicker. they are dipped.

 

[Tom-D]

Bad idea for many reasons, like electrical components, such as alternators magnetos, plug wires, sensors, all generally placed not to get direct hits from water that you soaked. Also not generally too smart to invent your own procedures in aviation, especially when you are student.

I wonder why these accessories are not damaged when we wash the engine during annuals?

 

[Tom-D]

Bad idea for many reasons, like electrical components, such as alternators magnetos, plug wires, sensors, all generally placed not to get direct hits from water that you soaked. Also not generally too smart to invent your own procedures in aviation, especially when you are student.

where is the alternator and mags on a Continental 0520?

 

[Tom-D]

As for the OP and his problem, I seriously doubt any damage was done.

me either. much to do about nothing. He was never near the temps required to damage anything in these engines.

many experts here trying to take this thread around the corner and a different direction. as always

 

[Ravioli]

I guess I'm taking the bait.

Why would anyone spray water into the cowling of an airplane? Ever? Even if it was on fire I'd use a chemical fire extinguisher (I've got 1 in the plane and 3 in the hangar)

 

[Stewartb]

A couple of comments. My engines all make "tink" noises when they cool. No water required. When I wash my plane I wash my nose cowl and water gets sprayed on the hot engine. I don't see how that's any more threatening than landing in puddles on tires or on floats when coming off step and pushing water into the prop. I wouldn't advise intentionally water cooling an air cooled engine but wouldn't be too concerned about damage from one incident.

 

[arnoha]

Huh. There was a Horse on one of my motorcycle boards who was permabanned years ago. Horse is a pretty common word, so I assume it's just a coincidence.

Non sequitur. Carry on.

 

[Dr. O]

Bull Sheet. You did nothing to that engine. You would have done nothing to it had you sprayed it as soon as you jumped out.
After 20 or 30 minutes the engine is still hot to the touch of our flesh, but it is not even close to hot in metallurgical terms. The instructor is a nut case. Tell him to prove it and you will have ten metallurgists to call to the stand to show he is an idiot.
My gawd, the motocross bunch pound those high dollar air cooled racing engines through explosions of mud and water, over and over. Then after the semifinals go back out and do it again in the finals. They beat on those engines beyond anything an airplane does and the engine goes racing week after week.

 

[SixPapaCharlie]

I thought "horse" was pflemming. Very first post was an explanation about Pete on the purple board which he then deleted. And now this...

 

[SkyDog58]

Regardless of whether any damage was done and none may have been done, this much is true.

OP did something to the airplane that as a student pilot he had not received any instruction to do.

OP admits that he did not know the possible consequences of his actions but still seems to want to defend his actions along a "no harm, no foul" mentality.

OP wants to bash the CFI for his overreaction but does not appreciate the fact that many pilots and even some mechanics operate under the same impression (right or wrong does not matter at this point) that the CFI has about shock cooling due to it being a long standing point of contention in GA.

OP needs to put his tail between his legs and run on home to mommy's basement and not come out until he reaches at least an adolescent maturity level.

 

[timwinters]

OP admits that he did not know the possible consequences of his actions but still seems to want to defend his actions along a "no harm, no foul" mentality.

Tom-D's son?

 

[PaulS]

where is the alternator and mags on a Continental 0520?

Don't know, mags probably on top, alternator or generator on the side, wires and connectors too. In the words of the infamous Hillary Clinton, "What difference does it make...."

 

[PaulS]

I wonder why these accessories are not damaged when we wash the engine during annuals?

I wonder why you test run the engine after maintenance then smarty pants, or maybe you don't.

 

[PaulS]

Finally, let's see what this guy says about spraying down engines: https://www.aopa.org/news-and-media/all-news/2015/july/06/how-to-clean-your-engine-compartment

"....
If your goal is to get a more thorough cleaning of the entire engine and compartment prior to inspection or maintenance, we need to take a more disciplined approach. That begins with protecting the vulnerable parts of the engine from damage. There are many different components within an engine cowl that you do not want water or cleaning chemicals coming in contact with:

• Electrical components, connectors, fuses, and bus bars—These items need to be well protected. It’s fairly easy to introduce electrical gremlins by spraying water and chemicals willy-nilly around these components; plus, a strong spray of water can pull a wire or connector out of place.
• Alternators and starters—The electrical components of these are typically vented to assist in cooling. Those vents are excellent paths for water and cleaning agents. There are also sensitive bearings inside to watch out for.
• Vacuum pumps—The typical general aviation dry vacuum pump must remain dry in order to function properly. Lubrication relies on dry carbon from the pump vanes to assist in smooth sliding of the vanes in the hub slots. Normally, the exhaust port on the pump is well protected from water, oil, or other foreign materials. One shot of water up that tube can ruin you day, and it may take some time before the failure surfaces.
• Breather tubes, fuel system vents, fuel injectors, and air intakes—Carefully protect all paths that air is supposed to flow to and from the engine. Filters should be protected as well, because many of them rely on oils that are impregnated into the material to catch dust and dirt.
• Hinges, bushings, and bearings—Your goal may be to remove excess oil from the outside of the crankcase or oil pan, but there are a lot of other components around that need their lubricating grease and oil left intact. So, don’t just spray solvent everywhere possible. Be very targeted in your application.

...."

 

[Horse]

I can't believe I'm the only one who has ever thought to do this. I already had the hose going to wash off mud and it was kind of an obvious thing to do to cool down the engine. Flying in heavy rain is a lot more harsh than what I did. It is colder and being accelerated into the engine by the prop.

Why else would a hose be next to the pumps with instructions how to use it? I bet there are others doing this.

As for my name... Hose was taken. Went with Horse instead. Huh.

 

[ircphoenix]

I can't believe I'm the only one who has ever thought to do this. I already had the hose going to wash off mud and it was kind of an obvious thing to do to cool down the engine. Flying in heavy rain is a lot more harsh than what I did. It is colder and being accelerated into the engine by the prop.

Why else would a hose be next to the pumps with instructions how to use it? I bet there are others doing this.

As for my name... Hose was taken. Went with Horse instead. Huh.

Heavy rain isn't being directed via a hose directly into the cowling. It's being sucked into a hot engine that is continuously producing heat.

Maybe the hose is there for people to wash mud off the wings. Like you did.

Whether or not it DID damage, there is a POTENTIAL for damage. Whether from shock cooling via water (not the hotly debated air shock cooling in flight) or from getting a substantial amount of water into components of the engine which can tolerate SOME moisture, but not a hose pointed at them.

You shouldn't have done what you did. The engine worked after. It's probably not damaged. But that doesn't make what you did OKAY or smart.

 

[Horse]

Well if cold water is bad for a hot engine then that would mean it is worst when the engine is running since that is when it is hottest. Also water being "directed" or "sucked in" that is irrelevant how the water gets in. I've scanned through the POH there is nothing about not flying through rain or not directing water at the engine in any other way.

I take exception to being called not smart.

 

[Ted]

I would think that there's a huge difference between a running engine getting wet (it's still producing heat to minimize rapid cooling) and a stopped engine being sprayed down.

I'll defer to @Ted DuPuis but I can envision real, significant damage being done to a hot, stopped engine if it's thoroughly "sprayed off" shortly after shutting down.

The water flow going through an engine when you're flying is going to be significantly lower than a water hose.

I think it's unlikely you did any immediate damage, but it is possible that you shortened the life of the cylinders or perhaps helped a crack to propagate. There's nothing that will prove you were responsible for this damage, so really there's nothing they can do outside of stop renting the plane to you.

While I understand your reasoning for spraying water into the engine, you really shouldn't do that. Let it cool off on its own.

 

[Horse]

The water flow going through an engine when you're flying is going to be significantly lower than a water hose.

Are you sure? If you step outside into heavy rain you will be drenched completely within a second, whereas with a hose it takes probably 5-10 seconds to get drenched to the same amount. I'm talking heavy rain. I'm sure you've flown through heavy rain before.

 

[ircphoenix]

Well if cold water is bad for a hot engine then that would mean it is worst when the engine is running since that is when it is hottest. Also water being "directed" or "sucked in" that is irrelevant how the water gets in. I've scanned through the POH there is nothing about not flying through rain or not directing water at the engine in any other way.

I take exception to being called not smart.

Because an active engine being run is producing heat to offset the evaporative cooling of water getting on to hot components. The air in the cowling is heated and being actively heated by the engine. Any water being sucked in is being warmed somewhat before hitting the hot engine. Once the water hits the engine, it is warmed and probably flashed off, depending on the exterior temperature of the components. But, again, the cooling effect is offset by the engine being actively producing heat. Versus what you did which is rapidly cooling an engine designed for air cooling, by cooling it with water.

For the record, I didn't say you aren't smart. I said what you did wasn't smart. Smart people do dumb things all the time.

Are you sure? If you step outside into heavy rain you will be drenched completely within a second, whereas with a hose it takes probably 5-10 seconds to get drenched to the same amount. I'm talking heavy rain. I'm sure you've flown through heavy rain before.

Really? Go outside in heavy rain. Run forward with your mouth open. Now have someone spray you in the mouth with a hose. Which one gets more water in your mouth?

 

[Tarheelpilot]

Well if cold water is bad for a hot engine then that would mean it is worst when the engine is running since that is when it is hottest. Also water being "directed" or "sucked in" that is irrelevant how the water gets in. I've scanned through the POH there is nothing about not flying through rain or not directing water at the engine in any other way.

I take exception to being called not smart.

Irc didn't say you were not smart. Irc said what you did was not smart. Smart people do stupid things all the time.
Spraying the engine with water has zero benefit to operations and some potential to damage the engine or an accessory. That decision was not smart.

 

[James331]

I don't agree at all. I didn't ask him to fly I just said "let's start it up and do a run up". If the friggin' engine was cracked like he claimed we'd figure it out pretty quickly before we even took off. He's a younger CFI not much commonsense not much experience. I'm going to guess early 20's. I've been around the block myself a few times.

As for common sense and experience... you're a low time student who just sprayed a hot engine with cold water, a very expensive hot engine which didn't belong to you.


If you've been around the block, you really should have known better, regardless of your lack of aviation experience.

You stop at a gas station with a friend who has a new vett, he goes inside, do you pop the hood and start dumping water on his engine? Of course not.



As far as trouble starting, that's just because you don't know how to start a hot (guessing injected) engine, lots of different tricks to get them to fire up right away, dumping cold water on them ain't one of em'

Also, yes, you could have caused damage that might not be obvious right off the bat, there are thin hot components of a engine, like much of the exhaust system, which even in rain doesn't really get direct contact from cold water.

I very much doubt the CHTs will be 300 degrees after decent and taxi. and a shut down.
besides,, shock cooling has been disproven many times.
If water cooling after shut down will harm any aluminum structure why doesn't it harm that structure while quenching after heat treatment?

I'd wager depending on the OAT, 200f or so, still hot enough I would not wash my engine for a while.

So shock cooling is a myth eh? Go have a talk with a few DZs and glider tow places. They all have procedures for cooling on decent, ofcourse their decent is much more dramatic than GA Joe in his 172 or Bo, but it's the same large picture.

I agree, if he just sprayed the front of the cowl inlet a little, doubt it did much, if anything. Still, not something I would be doing to my engine and sure as heck not something I would be happy to see someone do to MY airplane.

 

[neilw2]

I'm sure you've flown through heavy rain before.

Yea @Ted DuPuis , have you even flown through heavy rain before? Hehe....

 

[Dan Thomas]

http://www.thefabricator.com/article/aluminumwelding/achieving-t6-designation-for-6061

Solution heat treatment is done by raising the alloy temperature to about 980 degrees F and holding it there for about an hour. The purpose of this is to dissolve all the alloying elements in a solid solution in the aluminum. Then we quench the alloy in water. The purpose of quenching isn't really to strengthen the alloy, although it does somewhat; it is to cool it rapidly enough to prevent the alloying elements from precipitating on cooling.

read the whole article.

each manufacturers have their on processes but none have a alloy that can be changed or cracked by the temps in service or in this case less than 300 degrees to ambient.
we actually weld these cylinders, then normalize at much higher temps than will be found in service.

Heads aren't made from 6061. 6061 is an extruding alloy and will have completely different properties from typical aluminum casting alloys. Many are heated and then cooled slowly to allow the aging process to begin, which hardens them. Quenching aluminum anneals it and leaves it soft, not something we want for a head.

Machinery's Handbook has a lengthy chapter on the whole aluminum heat-treating thing.

The aluminum head will shrink at twice the rate the steel cylinder will, and quenching it could set up extreme stresses.

 

[jesse]

I'm not an engine expert. However I am a flight instructor an do operate a flight school.

The first thing you need to accept in this business is that students do make mistakes. It's your job to do everything you can to prevent those mistakes. You also have to be realistic and accept that "**** happens". The way you handle the situation with a student that makes a mistake is the difference between the end of the relationship or securing a very loyal customer. The problem though is that it's not always that simple. You also don't want someone to kill themselves. You need to really think these things through before you start accusing a customer of anything.

I could completely see how a scenario like this could happen. It's completely realistic for a student at some point in his/her training to get left alone with an airplane. If I've already taught someone how to pump gas, I might watch them once after that, but the third time I'm going to walk away intentionally. You have to let people "solo" even on operations like that on the ground. Just check their work afterwords.

I would say that the majority of students would never do something like this. They would recognize that it's not their airplane, they don't know what is under that cowling, and directing a massive stream of water into something they don't own without permission would be a really irresponsible thing to do. So I do think it's important for you in this scenario to accept the fact that you did something irresponsible. That might sound harsh but I do not intend it that way. I've done irresponsible things in my life too and will do one again. The important thing is whether you own it.

Now remember earlier where I said that it's important for a flight school to remember that "**** happens"? Just because someone made a irresponsible mistake and the damage could be expensive doesn't automatically mean you should burn the relationship with the customer. First off it is possible there isn't any damage. If there is no damage then you're going to cause way more damage by getting emotional and firing the customer. Even if there is damage you might still be better off to let the customer off easy and teach them something to make them safer for life.

If you do decide to get ****ed off and collect money from the customer. First off you will lose their business forever, possibly some of their friends, and anyone they ever would have referred. That alone could easily cost you more than the damage. That isn't your only problem though. You need to invest your time into trying to collect. That could be a lot of time. You could have put that time towards more proactive work building your business. Instead you're wasting it on a reaction that gains you nothing and costs you future business.

Now enters the tricky part about running a flight school. At the end of the day you need to remember that you are creating pilots. You have a morale obligation to think about how to make this into a lesson for the student. Thoughtless mistakes like this in aviation get people killed. Do you want to hear about a fatality some day involving the student? Do you want to not be able to sleep that night because you remember the time where you should have taught them something instead of just thinking about the business? No thanks..not me..I'd do everything I could to turn this into a great training moment.

So I'm a logical person. I'd stick to that for handling this. The moment I saw a student directing a hose of water into the cowling I would obviously ask them to stop. Once stopped I would first try to cool the situation in whatever manner was appropriate for their personality. Often times it'd be some sort of joke and distraction.

Once I felt like we were over the emotional part of fact that the situation occurred I would explain that there are lots of components under the cowling that were basically submerged in water. Those components were really hot and now they're not. The cooling occurred rapidly in a way that the engineers of the components may not have anticipated. It's definitely not the same as flying in rain. That involves by far more air than water all while rapidly moving OUT of the cowling.

Since I'm not the guy that designed all of the **** under the cowling I recognize that I'm not an expert. Even if I were there really isn't a soul out there that could say whether that was damaged or reduced life on the engine. Because of that I definitely would not just fire it up, do a runup, and take flight. Remember, we're creating new pilots, and we want them to be safe so that we can sleep at night. I lean heavily towards what is the safest reasonable action. My students will mock me. I need to recognize that and own it.

I would proceed to de-cowl the airplane with the student present. From there our conversation would very depending on their mechanical knowledge. It'd be a great time to really explain how an engine works and point out all of the components. The more a pilot knows about their engine the safer they are.

I would also point out the places where the water could have caused us problems. There are many.

I would give the student a flashlight and send them a hunt looking for cracks. I'd be watching them search.

Hopefully we'd be at home base. If so then we would be doing compression checks. I'd explain how sometimes there are cylinder cracks that you won't find with your eyes but you will find with a compression check.

I would make it very clear to the student that it would never be "OK" to just tear into someone's airplane after an incident like this without their permission. We're doing it because this a great opportunity for them to learn some things and ultimately this is now the work I have to do as a result of the action of their mistake. Therefore they will be helping me

The entire lesson would have shifted from whatever we were doing that day to teaching them everything I can about why you don't want to do what they did all while teaching them more about engines and trying to do it in a way that doesn't make them feel like ****. I personally believe it's unlikely that any damage took place so I'd try to be very positive throughout this.

I believe we wouldn't find any damage. I'd accept the reality that I'll never know whether or not that reduced the life span of a component. For all I know it could cost me dearly next week. Lesson learned. Include discussions about hoses with new students into training. You can't make someone pay for damage you can't prove took place.

What if this student a month later does something similar that implies their thought process hasn't changed? I'd fire the customer. This is the bad part about this business. Sometimes you have to fire people knowing it will damage your business both short and long term. Nobody wins.

 

[Ted]

Are you sure? If you step outside into heavy rain you will be drenched completely within a second, whereas with a hose it takes probably 5-10 seconds to get drenched to the same amount. I'm talking heavy rain. I'm sure you've flown through heavy rain before.

It's not a matter of raw water flow, it's a matter of the amount of water over a particular area. IRC gave the example of standing outside in heavy rain with your mouth open, which is exactly the point. The water hose will give you a very high water volume in a very small area, which is going to cause localized cooling at a much faster rate in that specific location.

Yea @Ted DuPuis , have you even flown through heavy rain before? Hehe....

You mean like days when the regional pilots are crying on the radio about the rain and turbulence, or days when ATC says "Heavy rain stretching from your 9 o'clock to your 3 o'clock. If you need to deviate, there's nowhere to go", or nights when the rain is so heavy that you can't see the runway (just the lights) and have to sit on the runway because it's raining too hard to see where to taxi?

Yeah, done that a time or two.

 

[wilkersk]

If it runs, there's no exhaust leaks, and compression is good, fly it. Why would you "x-ray" something just cause it got sprayed with a water hose? Thats like doing exploratory surgery because you caught a cold.

 

[coloradobluesky]

This, and some other reasons, are why a lot of FBO's dont allow plane washing at all. They dont even have a hose with water available. The CFI should not have let the student wash the plane unsupervised. Who knows what he's going to do? Be cautious.

Same goes with fueling. Be there every step of the way on self service fueling. Don't just tell the student to fill it up and go have a cup of coffee....

 

[Horse]

Really? Go outside in heavy rain. Run forward with your mouth open. Now have someone spray you in the mouth with a hose. Which one gets more water in your mouth?

That makes no sense at all. What is closer to the size of an engine? Your mouth or your body?

 

[Bill]

Really? Go outside in heavy rain. Run forward with your mouth open. Now have someone spray you in the mouth with a hose. Which one gets more water in your mouth?

Go outside in heavy rain, run forward at 150mph[1], then compare.

[1] Actually, due to prop blast, its a lot faster than that.

 

[Checkout_my_Six]

ouch....that hurts Charlie.