Is it safe to do a full throttle static run-up with cowling removed?

[kicktireslightfires]

I'm trying to isolate a burning smell (see the end of this thread: https://www.pilotsofamerica.com/community/threads/burning-smell-on-takeoff-any-suggestions.132573/) so think it would be a good idea to pull both the upper and lower cowling on my Cessna 162 and then go do a full throttle static run-up for 60 seconds, then shut down and sniff around and try to smell exactly where the smell is coming from.

I'm assuming it is, but just wanted to double check: is it safe doing a full throttle static run-up with the engine cowling removed? And is there a limit on how many seconds you'd want to do it for? E.g. No longer than 60 seconds?

Thanks in advance!

 

[Salty]

I wouldn't be that worried myself in the 162. But it only takes a minute to remove the whole cowl so I probably would just pull it off after the runup. (with a friend to help with the lower)

 

[EdFred]

Why would you think it wouldn't be safe? Trying to understand your thought process.

 

[Bill]

Why would you think it wouldn't be safe? Trying to understand your thought process.

You're not going to get cooling airflow down between the cylinders when the cowl is off, so I'd think you'd want to limit how long you run at full power. Hopefully one of our A&P guys will chime in.

 

[EdFred]

You're not going to get cooling airflow down between the cylinders when the cowl is off, so I'd think you'd want to limit how long you run at full power. Hopefully one of our A&P guys will chime in.

60 seconds though. On a small engine.

 

[schmookeeg]

Pulling the cowl changes the airflow in the engine, which might hide or move the problem. I concur with the above advice to run it up, THEN decowl it and start sniffing around. But no, you won't hurt anything by running it for 60 seconds decowled.

O-200s sort of do this by the way. I'd give a strong look at the pushrod packings and accessories first. Good luck on the hunt.

 

[idahoflier]

The cowl may be an integral component to producing your smell, so I would leave it on...

 

[Dan Thomas]

You're not going to get cooling airflow down between the cylinders when the cowl is off, so I'd think you'd want to limit how long you run at full power. Hopefully one of our A&P guys will chime in.

That right there. 60 seconds is a long time. Mechanics will run the engine up to 1700 or so to check the mags and pressures and so on, and it doesn't take that long. Full static generates a lot more heat, and without the cowl you don't have the full cooling system.

Power increases by the cube of the RPM, I am told. So from 1700 to 2300 or whatever you get at full static, you've increased the power by more than three times, along with three times more waste heat.

 

[Rushie]

That right there. 60 seconds is a long time. Mechanics will run the engine up to 1700 or so to check the mags and pressures and so on, and it doesn't take that long. Full static generates a lot more heat, and without the cowl you don't have the full cooling system.

Power increases by the cube of the RPM, I am told. So from 1700 to 2300 or whatever you get at full static, you've increased the power by more than three times, along with three times more waste heat.

Hopefully that will make the smell three times stronger.

 

[Dan Thomas]

Hopefully that will make the smell three times stronger.

It might generate some different, more expensive smells.

 

[write-stuff]

It probably depends on the airplane. But the cowling is an important part of the cooling process. I wouldn't suggest running it for any length of time without the cowling.

 

[Clip4]

Hire a mechanic.

 

[scarcherpilot]

I vacation in Myrtle Beach every year and the banner towers down there fly with no cowls on...always assumed it was for better cooling purposes. After I change my oil, I usually pull the plane out and run it for about 30 seconds or so on the ground to make sure oil isn't blowing out anywhere...then move her back into the hangar and put the cowl back on if it is all clear. Hasn't affected anything I can tell yet. But then again, i dont do full throttle, just a low RPM setting like 1100

 

[Jdm]

I like the way you’re thinking about engine cooling. Engines definitely do not receive the proper cooling on the ground, especially with the cowling is off. They make what’s called a “Club test prop” for prolonged ground test runs. I haven’t seen anybody use one in years, but it applies the proper load on the engine and also improves cooling.

The maintenance manual says this: “Avoid prolonged running on the ground. Engine cylinders do not receive enough cooling air flow unless the aircraft is moving forward at high speed.”

Will it hurt anything for a brief run? I doubt it, but why risk it? I’d definitely try to figure out a better way of locating a smell than running your engine at max power intervals. Seriously doubt that’s necessary.

 

[Stewartb]

No danger at all.

 

[Dan Thomas]

Extended ground runs, like engine testing after overhaul, is done with a shroud that takes the place of the upper cowling. It forces the air to take the proper path through the cylinders and around the case.

 

[Juliet Hotel]

There are banner companies that modify their supercubs with a small plenum and fly with no cowling at high power and low airspeed all day long with no cooling issues.
With a small 4 banger, even with no plenum, I wouldn't expect 60 seconds to hurt anything as far as cooling issues go.

 

[kmacht]

Does your 162 have some sort of engine monitor where you can watch CHT and oil temp? As long as you can monitor and keep those under control there is no reason you can't do a 60 second run with no cowling. The risk as mentioned above is overheating the engine due to the air not flowing and cooling the right places on the engine through the baffles. As long as you can monitor engine temps then that shouldn't be a problem. If you can't then I would consider tracking down the smell some other way.

 

[Dan Thomas]

There are banner companies that modify their supercubs with a small plenum and fly with no cowling at high power and low airspeed all day long with no cooling issues.
With a small 4 banger, even with no plenum, I wouldn't expect 60 seconds to hurt anything as far as cooling issues go.

That small plenum takes the place of the cowling. Of course it will have no issues. That appears to be a Supercub, which has a history of poor cooling with the stock cowling. I've dealt with that. That "small plenum" is likely there because it does a better job of cooling, not less. Banner towing is hard work for an engine.

And what is your experience to say that 60 seconds at full power will not hurt anything? Have you ever done it and watched the CHTs skyrocket? Have you ever thought about the sides of those cylinders that are getting little to no airflow? What happens to the oil on them? Small engines or large, none of them appreciate this. Each one is designed for a certain amount of cooling air, and that's in flight. On the ground it's less, and without the cowl it's FAR less.

So many pilots are worried about CHTs and other temp limits, yet will recommend overheating the engine like this for no good reason.

 

[Stewartb]

Lots of airflow from the prop. I have engine monitors and have ground run engines with and without a cowling. A one minute run after a brief warmup shouldn't cause any temp issues. Run an engine at 1200-1500-1800 RPM on the ground with a cowl in place? CHTs stay surprisingly low even after 10-15 minutes.

 

[Jdm]

Forgive me if this has already been asked, but why do you feel that it’s necessary to run full power and smell your engine? I’ve been an A&P since 1987 and have never had to do such a thing. Not saying that I’ve seen it all, just haven’t found myself in that situation. If you’re smelling something it’s probably an oil leak. Clean the engine and check for leaks. I’d also check the firewall, exhaust, and heater ducting if I were working on this airplane.

 

[Juliet Hotel]

So many pilots are worried about CHTs and other temp limits, yet will recommend overheating the engine like this for no good reason.

Slow your roll there chief.
1. I know exactly what the plenum is there for and what it does. I've also pulled lots of banners behind lots of Supercub stock cowls so I also know exactly what they can and can't do in terms of cooling during banner ops.
2. No where did I recommend overheating anything for any reason. I said I would not expect 60 seconds to hurt anything and I still think that. But that is not at all the same as saying yes I recommend you go do this so go do it. That is not what I meant nor what I said. If the OP wants to do it, that's on them. Its a free internet forum and any advice gleaned from it that one may choose to follow is worth exactly as much as they paid for it.

 

[JAWS]

Basic run up, below 2000 RPM and for as little time as possible and not on some turbocharged, fuel injected beast at warp 9 - sure. At full power of any engine - nope.

Airflow is your friend. I have seen some people place the top on and lockwire the ends to the engine. Not my cup of tea, but whatever floats your boat.

 

[Dana]

I wouldn't be worried about cooling during a short run, but... I don't know about the 162, but if it has a one piece nose bowl, how is it supported? On many aircraft the nose bowl is only supported by the cowling, so you'd have to remove the prop to remove the nose bowl and then replace the prop before running it.

 

[pfarber]

You're not going to get cooling airflow down between the cylinders when the cowl is off, so I'd think you'd want to limit how long you run at full power. Hopefully one of our A&P guys will chime in.

Cowls have these tiny little holes for airflow to limit drag. Since there is a small amount of air, it has to be used to the fullest cooling potential and guided to the hot parts.

Without a cowl the prop is free to bathe the engine in cooling air much easier.

All you have to do is look on youtube for dozens of post rebuild videos where mechanics run up the engine safely without a cowl. Of course you want to check your gauges for oil temp etc.

Many engine run up test stands have zero baffling for cooling air. The prop will move more than enough air at idle/full speed..... just watch the temps.

 

[Checkout_my_Six]

Ya let er rip....report back what you find. Lol

 

[pfarber]

Ya let er rip....report back what you find. Lol

Absolutely nothing bad happens. Are you under some impression that its not ok?

The only time I would be concerned is if you were running for a long time. How do you think MXs troubleshoot an engine problem if they cannot run it without the cowl to see whats going on?

Don't confuse running for a few minutes without a cowl with trying to do something like an engine break in. Also you are not going to take the baffles off, they are still there to assist with cooling.

 

[JAWS]

Cowls have these tiny little holes for airflow to limit drag. Since there is a small amount of air, it has to be used to the fullest cooling potential and guided to the hot parts.

Without a cowl the prop is free to bathe the engine in cooling air much easier.

All you have to do is look on youtube for dozens of post rebuild videos where mechanics run up the engine safely without a cowl. Of course you want to check your gauges for oil temp etc.

Many engine run up test stands have zero baffling for cooling air. The prop will move more than enough air at idle/full speed..... just watch the temps.

Right. "Engine test run as per Youtube".

 

[Blatham489]

Nobody has mentioned that running with the cowl off beats the hell out of the baffles, wouldn't expect a few short runs would cause problems but don't make a habit of it, eventually you'll start getting little cracks at the attach points.

 

[Dan Thomas]

So many maintenance experts with no maintenance experience or training.

 

[pfarber]

So many maintenance experts with no maintenance experience or training.

I will bet a warm diet cola that just about every P certified MX has run a piston engine without these magical baffles and cowls and nothing bad happens. When doing test runs at ERAU we didn't add anything. For a start up and ops check of 15-20 minutes its just not an issue.

Of course on the internet no one has common sense and the urge to be the smartest in the room (lol google smarts) means that they try and pick apart every worst case scenario, because they miss mommy's soft warm hug and need validation from strangers.

I can remember at least twice in the last 6 months the local A&P running engines without cowls (no need to take off the baffles for the work he was doing) and we are still flying that plane now. I mean by PoA 'google smart' posters that plane should have exploded the second full power was applied.

Oh, wait, out in the real world things like that don't really happen.

If you think you cannot run an engine without the cowls and baffles then how are A&Ps supposed to find the problems? I mean come on... common sense (which evidently is not that common) means that OF COURSE you have to run without a cowl, and sometimes baffles for short periods. Would I do a 30 minute continuous full power run? Evidently the wizards in this thread think that's the only way to run the engine lol

Tell me again how you are going to find that problem when you don't even remove the cowl to see the engine in operation? I'll wait while you try and google the answer.

 

[Dan Thomas]

I will bet a warm diet cola that just about every P certified MX has run a piston engine without these magical baffles and cowls and nothing bad happens. When doing test runs at ERAU we didn't add anything. For a start up and ops check of 15-20 minutes its just not an issue.

Of course on the internet no one has common sense and the urge to be the smartest in the room (lol google smarts) means that they try and pick apart every worst case scenario, because they miss mommy's soft warm hug and need validation from strangers.

I can remember at least twice in the last 6 months the local A&P running engines without cowls (no need to take off the baffles for the work he was doing) and we are still flying that plane now. I mean by PoA 'google smart' posters that plane should have exploded the second full power was applied.

Oh, wait, out in the real world things like that don't really happen.

If you think you cannot run an engine without the cowls and baffles then how are A&Ps supposed to find the problems? I mean come on... common sense (which evidently is not that common) means that OF COURSE you have to run without a cowl, and sometimes baffles for short periods. Would I do a 30 minute continuous full power run? Evidently the wizards in this thread think that's the only way to run the engine lol

Tell me again how you are going to find that problem when you don't even remove the cowl to see the engine in operation? I'll wait while you try and google the answer.

I ran engines without cowls. I did that a lot. I did not do full-power runs for 60 seconds without cowls. If I went to full power it was to determine that the max static RPM was within limits, and that takes about three or four seconds. Just do a one-minute full-power run sometimes and see how long that is.

The fact is that there was considerable engineering involved in designing that cooling system, to get a good pressure differential between the top and bottom of the engine and to ensure that the air was forced down and around the cylinder heads and barrels. Removing the cowl totally defeats that. It does not matter what sort of hurricane is blowing across that engine; it's not being cooled evenly or sufficiently. And, as I pointed out, runup RPM is a low power level, maybe 30 or 35%. Max static, with FP prop, is closer to 80%, and the increased fuel burn generates much more waste heat at that power. With a CS prop you can get 100% and really heat things up.

There are some airplanes that will overheat during a lengthy taxi, with the cowls ON. These things are not meant for extended ground ops.

Sure, some guys do runups at the schools while training as mechanics. But those engines never fly. If they fail due to heat damage it's no big deal.

 

[JAWS]

I ran engines without cowls. I did that a lot. I did not do full-power runs for 60 seconds without cowls. If I went to full power it was to determine that the max static RPM was within limits, and that takes about three or four seconds. Just do a one-minute full-power run sometimes and see how long that is.

The fact is that there was considerable engineering involved in designing that cooling system, to get a good pressure differential between the top and bottom of the engine and to ensure that the air was forced down and around the cylinder heads and barrels. Removing the cowl totally defeats that. It does not matter what sort of hurricane is blowing across that engine; it's not being cooled evenly or sufficiently. And, as I pointed out, runup RPM is a low power level, maybe 30 or 35%. Max static, with FP prop, is closer to 80%, and the increased fuel burn generates much more waste heat at that power. With a CS prop you can get 100% and really heat things up.

There are some airplanes that will overheat during a lengthy taxi, with the cowls ON. These things are not meant for extended ground ops.

Sure, some guys do runups at the schools while training as mechanics. But those engines never fly. If they fail due to heat damage it's no big deal.

View attachment 97676

Yep!

 

[EdFred]

Airboat.

 

[Checkout_my_Six]

Airboat.

Ya ya....those don’t have any cooling baffles or air flow.

 

[EdFred]

Ya ya....those don’t have any cooling baffles or air flow.

Less airflow being in front of the prop than behind it.

 

[Cap'n Jack]

Airboat.

Ya ya....those don’t have any cooling baffles or air flow.

Less airflow being in front of the prop than behind it.

Those seem to have automotive engines now. A 6 L GM seems to be common.
https://levitatorengines.com/engines/
https://marinepowerusa.com/airboat-engines/
https://www.americanairboats.com/projects/2010-16-x-8-airranger/
https://www.diamondbackairboats.com/levitator-performance-airboat-engines/
https://www.airboats.com/product-category/engines/
https://galemarine.com/custom-airboats/

They don't seem to use aircraft engines in Nebraska- I've been closer to them than this but not in a plane.
JAK_8324 by Jack Silver, on Flickr

 

[pfarber]

Every MX has their own views, and many/most are valid. The answer is in the careful application of knowledge.

But a full power run of a few minutes (not 30) without a cowl is not gonna hurt. I did mention watch temps, so its not like you stand there and wait for thing to seize.

Airboats... excellent point. Non certified MX using red tagged parts and still get 1000's of hours out of a motor. The FAA hates them! lol

 

[Stewartb]

Pressure cowls require forward speed to force air into the top and vacuum air out the bottom.

Many hot-rod Cubs (built to fly slow) are known to run hot. One popular solution is a Whirlwind prop. They have more blade pitch near the hub than other props and that helps push air into the cowl.

Most post-maintenance leak checks I see done are with no cowl.

 

[JAWS]

The FAA hates them! lol

Why would the FAA care?

Dan and I seem to like the idea of running with cowls on. Must be a Canadian thing, eh!