Oil System Cessna 172 | Aircraft systems

Wet sump oil system of Cessna 172P. Checkride prep. Aircraft systems. 

[@miltonbordignon6465]

this is the best explanation I've seen so far regarding oil systems

[@robertmcdaniel8147]

CFI Greg, this by far the best explanation I've found on this topic. Thank you so much for taking the time and effort to create it!

[@CFIGreg]

Glad it was helpful!

[@johnniewalters3718]

This is by far the simplest and straightforward explanation of the oil system. Thank you so much for sharing this.

[@CFIGreg]

Glad it was helpful!

[@aimeee3469]

This is great work chief! Loved the fact that you actually explain it clearly, and step by step with the use of the POH. A lot of the videos out there do explain the basics, but have been missing out some important/ small parts, such as when does the oil go through the cooler and when does it go through the filter. Will you be able to talk about the electrical system in a c182 if possible please?

[@noahmorris8998]

You're such a great teacher! It would be incredible if you made videos like this for the constant speed prop, landing gear, and pressurization systems too!

[@khimanidarshan3854]

Good job in explaining needed to refresh my memory about the topic very good to found your video

[@kmanniec9128]

Awesome video. Thanks to this, I'm getting sig off tomorrow on my engine routine. Thanks again.

[@CFIGreg]

Glad it helped. Doing my best to pump out more systems videos.

[@Aliveinthesky]

This is insanely well done and simplified thank you

[@CFIGreg]

Glad it helped!

[@nicholassurber7494]

this is an incredible explanation thank you so much for posting

[@CFIGreg]

Glad it was helpful!

[@mosesk4596]

Good video, with one issue.. the oil cooler bypass valve is temperature controlled, acting on oil temperature, not viscosity. It is similar in operation to a cars thermostat. Commonly called a vernatherm.

[@CFIGreg]

That is interesting to hear. I am open to learning new things. Would you mind explaining how the bypass spring can sense temperature? Or maybe send me a link to a source explaining how that would work? I took this information directly from the Cessna POH, along with the service maintenance manual used by A&P mechanics to service the plane.

[@CFIGreg]

I think you may be forgetting one thing, temperature and viscosity are directly related. So I guess one could make the argument that a vernatherm is temperature controlled, but as temperature rises, viscosity decreases, and so does the pressure of the oil. As far as I know, the bypass spring is not sophisticated enough to sense temperature. But if you have a source from Cessna that you can send me explaining otherwise, I would love to see it.

[@mosesk4596]

@@CFIGreg I think you have misread the manuals, look up how a vernatherm works. It is a temperature dependent wax pellet in that vernatherm that controls the spring, just like a cars thermostat. There is nothing viscosity dependent in the loop.

[@CFIGreg]

@@mosesk4596 that’s not quite what I read, i’ll look into it further, and if there’s something I missed, I’ll definitely add it to the video and description, I still encourage you to send me a link. Must be from Cessna/Textron for a 172P model. Must describe exactly what you are describing. Otherwise, I can’t add it to the video because I don’t have any evidence to back up what you are saying. Also, not every plane has a vernatherm, many of them will have viscosity valves which will function only based on viscosity. If you’re able to send me something solid from Cessna, I’d love to see it. I am not an expert on oil systems, but I also cannot make a claim about the 172 oil system based on a quick googling of vernatherms, I need the info to come from the manufacturer in some fashion. If you have a link, please send it my way so I can expand my knowledge. Thanks!

[@mosesk4596]

​@@CFIGreg I'll try and clear it up. The motor in your P model should be a O-320-D2J, doesn't really matter, most all O-320 sub-models are the same in regard to this valve. Lookup the parts catalog on Lycomings site, document PC-O-320-D2J, page 36, figure 19 (Oil Filter Assembly, Oil Cooler and Breather Fittings). The part you are looking for is figure 13, part number 53E22144, "VALVE ASSEMBLY, Temperature control, oil cooler bypass". Notice it says temperature control. You can buy one from many sources, stick it in boiling water and it will retract. It is temperature dependent, viscosity makes no difference, you can test it in water, oil of any weight, heavy oil or grease, or even just "air", you can stick it in an oven, the valve will retract around 200f if it's working. I've done it many times. This is getting way too detailed, we're starting to get into the engineering side here, but I wanted to give you a clear answer you can follow with approved data. The POH does not get into much detail, as a pilot doesn't really need to get into this much detail on how individual parts of the system work. But I checked a P model POH, section 7, it merely states "If the oil is cold, the bypass valve allows the oil to bypass the oil cooler.." then "If the oil is hot..", etc. Specifically mentions temperature with no mention of viscosity. I'm honestly not sure where you came up with it. Aviation is full of weird or outright wrong information that is passed on and on. Remember law of primacy and confirmation bias. Note that the term "Vernatherm" is just a more common word people use for a thermostatic valve. I believe it was the brand name given to this type of valve from the original manufacturer way back in the day. The name has stuck. Hope this helps.

[@aliakgoz1641]

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