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Engine run with top of cowl off?

rjcthree

Well Known Member
I may have to go to another airport to do a prop balance. I hate the idea of removing the full cowl at a remote location. Can a prop balance be done by removing only the top cowl, and is it safe to run the engine with only the bottom cowl installed(fully)?
 
I may have to go to another airport to do a prop balance. I hate the idea of removing the full cowl at a remote location. Can a prop balance be done by removing only the top cowl, and is it safe to run the engine with only the bottom cowl installed(fully)?

Yes and yes.
I've probably balanced more RV props than most, never had a problem leaving the bottom cowl on.
 
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Engine Runs

On some planes the bottom cowl can be a little floppy in the spinner area when the top cowl is removed. In those cases safety wire can be run from the cowl screw holes back to the engine to stiffen up things a bit.


Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
I would never do that. Why would you want it bouncing around, stressing the hinges and bouncing against the back of the spinner?

Carl
 
I do it after every oil change to ck for a possible leak at the filter. No issues rubbing against the spinner or flopping around.
 
Accelerometer and Photocell

6OztKz.jpg
 
On some planes the bottom cowl can be a little floppy in the spinner area when the top cowl is removed. In those cases safety wire can be run from the cowl screw holes back to the engine to stiffen up things a bit.

That's what I do, too. Dozens of times and no problems.
 
Not sure, but wouldn't the loose cowl half rattling in the breeze influence the accuracy of the balance equipment? Not sure what RPMs the tests are done.

Roberta
 
I do it after every oil change to ck for a possible leak at the filter. No issues rubbing against the spinner or flopping around.
Doing ground idle and runups with the top cowl off is one thing. Going flying with it that way it something else entirely.

On most planes, I think I'd be more inclined to try it with both the top and bottom cowl off rather than just the top. Less chance of anything bad happening that way. Of course without a plenum on the engine, I'd expect cylinder temps to be an issue regardless of whether you try it with just the top off or the entire cowl.

Really the best bet is to fly with the entire cowl in place as designed and remove it when you get there. If you're going to a maintenance shop to have the work done, then you're going someplace where fragile cowls being removed is a daily event.
 
It works fine. Have done many prop balances this way. As someone mentioned, do check to make sure the bottom cowling isn't rubbing the spinner. It shouldn't happen, but these are all individually built. :)

Vic
 
Doing ground idle and runups with the top cowl off is one thing. Going flying with it that way it something else entirely...


I didnt get the impression the OP or subsequent replies were discussing flying the airplane with any part of the cowl removed.
 
I didnt get the impression the OP or subsequent replies were discussing flying the airplane with any part of the cowl removed.
True, but while balancing a prop you will go to full throttle to get a complete vibration profile.

The point someone made about vibration readings changing with/without the cowl may be valid... If nothing else a lower cowl vibrating on its own may add noise to the reading.

That all said, when I did my dynamic balance, I did it with top cowl removed, bottom in place, and had no issues. It feels smoother now. :)
 
Leak Check

I do it after every oil change to ck for a possible leak at the filter. No issues rubbing against the spinner or flopping around.

Thread drift, but...

I'm curious why you don't do the leak check before replacing the lower cowl?

Skylor
 
I don't pull the bottom cowl/sump screen for a routine oil change,just at CI time. I can fish a drain hose to my quick drain from the cowl exit so that is why the bottom cowl is still on. I know that may be heresy to some to only pull the sump screen every other oil change!
 
I don't pull the bottom cowl/sump screen for a routine oil change,just at CI time. I can fish a drain hose to my quick drain from the cowl exit so that is why the bottom cowl is still on. I know that may be heresy to some to only pull the sump screen every other oil change!

That sounds to me like you are only doing a visual inspection of the lower engine area once a year.

The few minutes extra to remove the lower cowl every oil change for a good "look-see" down there would seem to be a wise thing to do. :)


PS - per Lycoming, the oil suction screen is a 100 hr item -

Oil Suction and Oil Pressure Screens – At each 100-hour inspection remove suction screen. Inspect
for metal particles; clean and reinstall.
 
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That sounds to me like you are only doing a visual inspection of the lower engine area once a year.

The few minutes extra to remove the lower cowl every oil change for a good "look-see" down there would seem to be a wise thing to do. :)


PS - per Lycoming, the oil suction screen is a 100 hr item -

Oil Suction and Oil Pressure Screens ? At each 100-hour inspection remove suction screen. Inspect
for metal particles; clean and reinstall.

Gil beat me to it. +1.
 
That sounds to me like you are only doing a visual inspection of the lower engine area once a year.

The few minutes extra to remove the lower cowl every oil change for a good "look-see" down there would seem to be a wise thing to do. :)


PS - per Lycoming, the oil suction screen is a 100 hr item -

Oil Suction and Oil Pressure Screens ? At each 100-hour inspection remove suction screen. Inspect
for metal particles; clean and reinstall.

Also I?m fairly certain this crush washer must be replaced each time the screen is removed per Lycoming.

https://m.aircraftspruce.com/pages/ha/washers/an900.php
 
That sounds to me like you are only doing a visual inspection of the lower engine area once a year.

The few minutes extra to remove the lower cowl every oil change for a good "look-see" down there would seem to be a wise thing to do. :)


PS - per Lycoming, the oil suction screen is a 100 hr item -

Oil Suction and Oil Pressure Screens ? At each 100-hour inspection remove suction screen. Inspect
for metal particles; clean and reinstall.

+2
I also don't check the suction screen every oil change, however, I always pull the cowl and do a visual check. I have been able to catch numerous issues early. This is especially important in the first 100+ hours as many bolts/nuts need to be snugged early on as heat does its thing.

Larry
 
I am hesitant to post this as two people that criticized doing a quick oil change without pulling the bottom cowl are very respected posters here and I rarely post. I always have a look see in the engine compartment anytime any part of the engine is uncowled. I can't speak to the two place RV's,but on a RV10 there is a large amount of room between the engine and cowl sides. I can see all the exhaust,control cables,hoses & lines,EGT & CHT probes and all their wiring,as well as all the nose gear and it's suspension. About the only parts not readily visible are the starter and alternator and those are easily inspected with my flexible borescope camera. I would never do an oil change and ignore what things look like in the engine compartment. If you don't have a helper the RV10 lower cowl is a bear to reinstall by yourself. If I said I didn't believe in safety wiring the oil filter,I could see the need for criticism,but this seems a bit excessive. Rant off. Apologies if I offended anyone.
 
I am hesitant to post this as two people that criticized doing a quick oil change without pulling the bottom cowl are very respected posters here and I rarely post. I always have a look see in the engine compartment anytime any part of the engine is uncowled. I can't speak to the two place RV's,but on a RV10 there is a large amount of room between the engine and cowl sides. I can see all the exhaust,control cables,hoses & lines,EGT & CHT probes and all their wiring,as well as all the nose gear and it's suspension. About the only parts not readily visible are the starter and alternator and those are easily inspected with my flexible borescope camera. I would never do an oil change and ignore what things look like in the engine compartment. If you don't have a helper the RV10 lower cowl is a bear to reinstall by yourself. If I said I didn't believe in safety wiring the oil filter,I could see the need for criticism,but this seems a bit excessive. Rant off. Apologies if I offended anyone.

I don't think it's wrong to do an oil change with the bottom cowl on. However, I do advocate doing a visual inspection as often as possible. It only takes a few minutes and will allow the owner to become more intimate with their engine and have a greater likelihood of finding issues before they become ugly problems. Looking at the engine only at annual time, just isn't enough in my opinion, if you are putting on lots of hours in a year.

This is just a philosophy to help stay ahead of problems, it is by no means the only way to do things and each should be comfortable with their own approach.

Consider the number of folks here that have had their top carb screws loosen and didn't find it until the engine ran very poorly. I found loose bolts on my starter (a common problem on Skytec's) that I caught before it fell apart and possibly damaged itself of something else. This is two examples where an unobstructed view of the bottom is necessary. Consider the security of the heim on your throttle arm. If it falls off, you have either no power or way more than you want for landing.

I personally take every opportunity to look at the engine and encourage others to do the same. However, it is just an opinion. Lots of certified planes only get looked at once a year and lots of folks only put on 25 hours in a year. I do over 150.

Also, I don't safety wire my oil filter as I don't see the need. 10's of millions of cars have been produced with this style of oil filter and I have never heard of one falling off that was installed properly. Though I don't criticize anyone for doing it.

Larry
 
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I will never apologize for promoting safety based on my many years of experience, and the experience of others maintaining and operating these airplanes.

Experience shows that things can happen in just the 50 hour intervals that are typical between oil changes, that can quickly become major safety issues if not detected.

Issues with the exhaust system are a good example.

I agree that the exhaust system on the RV-10 is slightly more inspect-able than on the other RV's but much of it still can not be.
This is only one example of many things that should be looked at regularly.

If people want to take a shortcut doing an oil change that is their choice, but I hope others will consider the trade-off. Removing the bottom cowl doesn't take all that much extra time. I can't see how the small amount of time saved is worth risking the consequences of things that can be missed because they weren't seen.
 
I will never apologize for promoting safety based on my many years of experience, and the experience of others maintaining and operating these airplanes.

Experience shows that things can happen in just the 50 hour intervals that are typical between oil changes, that can quickly become major safety issues if not detected.

Issues with the exhaust system are a good example.

I agree that the exhaust system on the RV-10 is slightly more inspect-able than on the other RV's but much of it still can not be.
This is only one example of many things that should be looked at regularly.

If people want to take a shortcut doing an oil change that is their choice, but I hope others will consider the trade-off. Removing the bottom cowl doesn't take all that much extra time. I can't see how the small amount of time saved is worth risking the consequences of things that can be missed because they weren't seen.

Agree 100%, Amen Brutha!
 
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