Multi-Engine Runup

[Fearless Tower]

Just curious what the consensus is here - when exercising the props, do you do both props together, or individually?

It seems that some people I have flown (particularly those with large radial engines) say that you should exercise the props together so that you can have a side by side comparison. Others (particularly the light twin guys, but not always) think that is crazy and insist that you should exercise each prop individually.

I'm still a relatively low time multi guy and not sure that I have formulated a firm opinion yet.

What say ye?

 

[Henning]

I do them individually just because I want to know which one I'm hearing if I hear something unusual. It's six of one, half a dozen of the other really though, whatever you want to do. If you hear something wrong, you just have to do another round of checks to figure out which one, and I'm an "efficiency" kind of guy.

 

[poadeleted20]

I'm with Henning -- one at a time, for the reasons he stated.

 

[HPNPilot1200]

I exercise each individually for the same reasons as Henning. It allows you to more quickly isolate and determine which engine may have a potential problem.

 

[bobmrg]

Count me in the one-at-a-time column.

Bob Gardner

 

[TMetzinger]

One at a time, for all the reasons noted earlier.

 

[Let'sgoflying!]

individually.

 

[Dave Siciliano]

+1. My props cycle just a bit differently. I like to compare them to what is normal, and this is more helpful.

Best,

Dave

 

[Ted]

On the Aztec I cycle them together. The 310 has detents that make it difficult to do together (the levers have to be moved slightly inward). As Henning also said, it's six of one half dozen of the other, and doing both together is more efficient.

I know what I expect out of each plane. Both have slight differences one side to the other. If you do your runup the same way every time, you'll notice if it's different from normal. If there actually is a problem (or reason to suspect a problem), then do each one individually. I also cycle mags for both engines at the same time, same reasons.

Think about the point of a run-up. It's really to identify that there aren't any problems. You can do that just fine in a twin with checking both sides together. If there is a problem, you'll take more time to figure out what the problem is (or attempt to), and then probably taxi back and get it fixed.

 

[Teller1900]

We do them separately for several reasons. 1) That's what the book says to do, 2) you can focus more closely on all the parameters for each engine individually, 3) on contaminated surfaces there is less risk of sliding, especially when feathering the engine, and 4) that's what the book says to do.

 

[Greg Bockelman]

3) on contaminated surfaces there is less risk of sliding, especially when feathering the engine, and 4)

I have been on a surface slick enough that if one engine was run up to the proper RPM, there was no way to keep the plane from turning sideways.

 

[bbchien]

One at a time, and at a standstill. I have done it on the roll but it was not terribly willingly. Hard on brakes and tires.

 

[Jim Burns]

One at a time. My props feather at different rates.

 

[Aztec Driver]

One at a time. My props feather at different rates.

Same for me.

 

[gismo]

I do them individually just because I want to know which one I'm hearing if I hear something unusual. It's six of one, half a dozen of the other really though, whatever you want to do. If you hear something wrong, you just have to do another round of checks to figure out which one, and I'm an "efficiency" kind of guy.

I do the props together (and the mag checks for that matter). If one behaves differently than the other and I can't discern what was wrong I'll repeat the process one at a time. Doing both at once makes a difference more obvious, minimizes the time the engines spend sucking up rocks from the ramp, creates less noise for the airport neighbors (and saves me a few seconds). If you do one at a time can you easily detect that one prop is feathering slightly slower? I don't see the point of separate runnups when everything is working which is most of the time, for me efficiency means economizing the normal at the expense of the abnormal, not the other way around.

 

[gprellwitz]

With my whole 10 hours or so in multi, I do them one at a time, for the reasons already given.

 

[Henning]

I do the props together (and the mag checks for that matter). If one behaves differently than the other and I can't discern what was wrong I'll repeat the process one at a time. Doing both at once makes a difference more obvious, minimizes the time the engines spend sucking up rocks from the ramp, creates less noise for the airport neighbors (and saves me a few seconds). If you do one at a time can you easily detect that one prop is feathering slightly slower? I don't see the point of separate runnups when everything is working which is most of the time, for me efficiency means economizing the normal at the expense of the abnormal, not the other way around.

Yeah, like I said, 6 of one, half a dozen of the other, it gets done either way. Just a matter of personal preference. I like keeping the engines at power for the extended time, just makes me feel good, and once the mag check is done (which I do both sides at a time) I bring em back till they're just starting to ramp down off the pipe, then when everything is done, I'll run them smoothly but quickly to full throttle and back to idle while controlling a roll to the hold short line, and I do that together.

 

[Ted]

I do the props together (and the mag checks for that matter). If one behaves differently than the other and I can't discern what was wrong I'll repeat the process one at a time. Doing both at once makes a difference more obvious, minimizes the time the engines spend sucking up rocks from the ramp, creates less noise for the airport neighbors (and saves me a few seconds). If you do one at a time can you easily detect that one prop is feathering slightly slower? I don't see the point of separate runnups when everything is working which is most of the time, for me efficiency means economizing the normal at the expense of the abnormal, not the other way around.

Lance and I pretty much do our runups the same on the Aztec/Baron. Although part of that was that after seeing how he did his, I liked it and adopted it.

Edit: I always did the props and mags together, though.

 

[gismo]

One at a time. My props feather at different rates.

Have you ever wondered why? At one time my left prop was noticeably slower to drop RPM during the check and when I feathered it completely in the air it took about a minute to stop turning compared to 10-15 seconds on the right side. Turned out that the linkage to the governor was a bit loose and the valve wasn't completely closing. If it had gotten any worse it probably wouldn't feather at all. I believe that when properly set up, thre's no reason why both props shouldn't behave the same way.

 

[Ted]

Have you ever wondered why? At one time my left prop was noticeably slower to drop RPM during the check and when I feathered it completely in the air it took about a minute to stop turning compared to 10-15 seconds on the right side. Turned out that the linkage to the governor was a bit loose and the valve wasn't completely closing. If it had gotten any worse it probably wouldn't feather at all. I believe that when properly set up, thre's no reason why both props shouldn't behave the same way.

On the 310 the right and left side do have different rates when doing a feather check. So, I feathered each prop in flight fully to make sure they were both working. Interestingly, no significant difference in feather rate, but that is something good to know and keep an eye on if it gets worse.

 

[Teller1900]

I have been on a surface slick enough that if one engine was run up to the proper RPM, there was no way to keep the plane from turning sideways.

As have I. Harley can attest, Rockland in the winter is an adventure on ice - I've had the plane sliding sideways with both engine at idle. That's when we just push it into a snow bank and say we'll come for it in the spring. But that's also why they suggest we don't feather both engines at the same time on contaminated surfaces.

For the runup on the CT-7s, though, we don't actually increase power above ground idle. It's a long series of feathering/unfeathering to check the long list of accessories bolted to the engine. When you feather that thing, you get a big blast of thrust right as it comes into feather, which is why they don't want us doing both at once. With one at a time we can reduce the amount of total uncontrolled thrust, and you've at least got the other engine available to reverse if you need it to keep from hitting the building, GSE, people, etc.

 

[vontresc]

On the 310 the right and left side do have different rates when doing a feather check. So, I feathered each prop in flight fully to make sure they were both working. Interestingly, no significant difference in feather rate, but that is something good to know and keep an eye on if it gets worse.

So when you did the feather test in the air, did you do them simultaneously or one at a time

 

[Ted]

So when you did the feather test in the air, did you do them simultaneously or one at a time

I was waiting for that. One at a time. The 310 is a crappy glider. So is the Aztec.

 

[Jim Burns]

Have you ever wondered why?

I'm guessing that it is a combination of factors starting with age/wear of interal governor components, same with prop hub components, amount and type of grease in the hub, engine oil pressure, engine time SMOH...

Also, when Hartzell ended up with all the old Hamilton Standard governors, there were many mods performed, oil ports either plugged or drilled, bases and heads swapped, options added/removed.... what a night mare. This was all an attempt to save the old bases and heads, if you wonder why, price a new one!