You did not mention that the emergency system is designed to be idiot resistant. With the gear selector in the up position and the emergency gear switch in the normal mode the gear will drop below 87 kts. When studying the diagrams for the 1968 Arrow that I used to fly, it appeared that the gear would drop with the master switch off as well. I did test the low speed deployment (at a safe altitude) but never tried the master switch test. I don’t have access to the manual any more. I loved that plane. 140 kts @ 9 gallons per hour.
Great video and explanation. The animation borrow of the oil filter was also good. Loved the way you placed the POH section along with the generic diagram of these systems.
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.
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.
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.
@@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.
@@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!
@@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.
I have a 1977 Piper Arrow III. The landing gear was working just fine until the annual inspection. At annual when we tested the emergency down cycle, it worked just fine. We did it three times. After that we had problems with fully retracting the gear. The gear would go up but he hydraulic pump would go on and off every three or four seconds for about 1/2 second, maybe less. The hydraulic pump was going on intermittently. I figured it was a leak somewhere and looked all over for that leak. Could not fine one. The gear cycled down just fine and no hydraulic pump intermittent operation. My mechanic said it may be the pressure switch going bad. He also thought it may be the emergency down mechanism. He also said it might be the pump. I disagree on the pump because it has been in the plane for just a few hundred hours. The mechanic seems to be all over the place with his diagnosis. What do you think? Any suggestions?
@@CFIGreg It is highly likely the gear up check valve leaking or not seating. Your explanation is great. I pulled the pump and sent if off for overhaul. I don't believe the hydraulic fluid has been changed in the pat 40 years.
Hello, I fly the A22L2 and this is the video I needed to fully understand the ignition system and its components, thank you for making this video! greetings from Spain.
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?
I added this to my new playlist for the Arrow. I start my complex rating today. I will be adding more self-GoPro footage to this playlist as I go through the training. Thanks for the great video Greg.
WOW, this is by far the best video that I have seen explaining the Arrow's gear system. I'm a CFI just looking for videos to share with my students for their complex endorsements and this have just moved to the top of the list! THANK YOU!!!
Dude, thank you so much for this excellent explanation. The Arrow POH says virtually nothing about the hydraulic system components beyond providing the diagram seen in the video. We are quizzed on the Arrow landing gear system at our Part 141 school during stage checks, but we’re given poor references from which to learn. One of our “sources” is just a few paragraph-long document written by one of our CFIs (I think? God knows who) in which they vaguely and imprecisely explain the system. This video was very clear and helpful
I have a 1977 Piper turbo arrow III. On two recent short flights I have noticed the gear unsafe light illuminate and it appears that the main gear are sagging into the airstream, but the pump is not activating to fully retract the wheels. Any ideas on the cause?
I’m not really sure what would cause that. I’m not an A&P so my knowledge level of the landing gear is tailored more towards teaching students a basic understanding of how the gear functions. I would do some research and maybe consult an A&P. I’d also like to know the answer, shoot me a message if you find out.
I have that similar issue right now on my Turbo Arrow III. While flying if I did a abrupt push over with the yoke that would be enough for the light to go out. We put it up on jacks and found out which main it was and when we pressed up on the right main the light went off. We have new switches on hand and will replace it at annual this month. Hopefully that's all it is is just a bad switch.
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!
