Leaning NA CS plane.. a multi!

[Tantalum]

I've been building multi time in a Duchess... so far I love flying multi's! (@GRG55 the Aztec will be next year, got my first trip planned and I'll report back)

Anyway, my question is two part

(1) when you lean a plane with constant speed props there is no RPM change (obviously).. so, in the absence of a reliable fuel flow gauge do you just lean until you feel it turn rough and then add a little back? Is there some other method?

(2) in a multi.. obviously you won't lean both at once.. but with the noise and vibrations from two engines leaning strictly by feel may even be harder.. any tricks? Trust the EGT gauges?

In the Cirrus I've always used the fuel flow to lean, and in the simple PA-28-161/181 I've done it the old school way of feeling it turn rough

Any tricks for CS/multi?

 

[ja_user]

Don’t you have full flow for a course setting and EGT for fine tuning?

 

[Tantalum]

Don’t you have full flow for a course setting and EGT for fine tuning?

Yes, but is EGT really the best? Not sure how well I trust this 30 year old gauge

 

[ja_user]

The actual temps don’t matter, just that it knows colder from hotter. You’ll be able to tell if the fuel flow and egt aren’t making sense on one engine.

 

[guzziguy]

Leaning till rough WILL result in RPM change in a CS aircraft. Might not be as noticeable as FP, but it's there.

Also, something I've noticed:
my POH states that cruise GPH for my PA28R-180 is about 8 GPH. This fuel flow holds for any altitude except for 10k+ where I can get it down to 7-ish GPH.

I have noticed that when I set my MP/RPM to book settings (based on altitude) and lean accordingly, the resulting FF is nearly always 8 GPH.
I have thus concluded that I can also use FF to help in setting the engine instead of doing the mental math interpolation or checking the performance tables to set the MP/RPM. If nothing else, it is a nice cross-check to confirm I have the engine leaned appropriately.

 

[hindsight2020]

Parallel Lycos in a multi-trainer bruh. Just treat it like a cherokee. Pull to rough then do the hokie pokie, or pull to peak on those one-prober setups, whatevs. It's not a conti, they won't mortar jugs out the cowl just because you gave them the female co-star treatment in a john wayne movie.

 

[Tantalum]

Pull to rough then do the hokie pokie, or pull to peak on those one-prober setups, whatevs

That's basically what I've been doing. But given that there's no fuel flow, no fuel totalizer, and dubious fuel gauges (although they appear accurate) if I do a few longer cross countries on this thing I want to make sure I have the fuel flow as lean as I can reasonably get it

 

[schmookeeg]

Why can't you lean both at once? Once you learn where they end up, just do that in the future. If it's a rental bird I assume there's an annoying split in the levers, but just shape your hand to match the final position

(wait if it's a rental bird, why are you leaning? you might be the first one in a decade to try moving those)

 

[RussR]

(2) in a multi.. obviously you won't lean both at once..

There's no "obviously" about it - I lean both engines at once unless I'm really trying to fine tune something, but even then I'm pulling them both back at once and just fine tuning with whatever finger is on that engine's control.

This is everything from Seminoles to 421s.

In the Seminole, I just lean it until rough, then push it back in a little. It has a single-needle (per engine) EGT gauge, but when I've used that, it ends up being the same as "rough then rich a little".

Actually, on most training flights, we just pull it back about halfway and it's good enough. For those flights, it's more of a "procedural discipline" function, since we're likely to push the mixture back to full rich in a matter of seconds, whether it's for some maneuver or engine failure scenario.

 

[Tantalum]

There's no "obviously" about it - I lean both engines at once unless I'm really trying to fine tune something, but even then I'm pulling them both back at once and just fine tuning with whatever finger is on that engine's control.

This is everything from Seminoles to 421s.

In the Seminole, I just lean it until rough, then push it back in a little. It has a single-needle (per engine) EGT gauge, but when I've used that, it ends up being the same as "rough then rich a little".

Actually, on most training flights, we just pull it back about halfway and it's good enough. For those flights, it's more of a "procedural discipline" function, since we're likely to push the mixture back to full rich in a matter of seconds, whether it's for some maneuver or engine failure scenario.

Thanks, the "pull it about halfway back" thing works locally, but if I'm planning a long cross country that might be cutting it close on VFR reserves (depending on wind) I'd like to be sure I have that leaning dialed in as well as I can.. it sounds like a combination of "pull to rough" and looking at that single EGT gauge are the best ideas. Obviously, without accurate fuel gauges and no totalizer or actual known fuel flow I would heavily pad the endurance on the side of safety

 

[schmookeeg]

Assuming it only has those alcor-style EGT gauges, peak is peak, I'd happily put it ~50 ROP or whatever your intended setting is using that -- actual units of measure not needed

I have found even the Duchess fuel gauges to be reasonable in their accuracy... using, say, a C172 as the benchmark.

 

[GRG55]

There's no "obviously" about it - I lean both engines at once unless I'm really trying to fine tune something, but even then I'm pulling them both back at once and just fine tuning with whatever finger is on that engine's control...

Same here. I "rough" lean both at once and then fine tune individually with the EGT.
As someone else mentioned you get to know where the levers should be.

 

[midwestpa24]

Why can't you lean both at once? Once you learn where they end up, just do that in the future. If it's a rental bird I assume there's an annoying split in the levers, but just shape your hand to match the final position

Just my opinion and way of doing things, but I will rough lean both at once, then fine tune each lever individually. They will usually wind up off a little from each other, as do the throttles and props, but thats fine. Every twin I've ever flown has EGT and fuel flow gauges, and am usually leaning for EGT and comparing fuel flow.

 

[denverpilot]

Don’t you have full flow for a course setting and EGT for fine tuning?

^^^ that.

Yes, but is EGT really the best? Not sure how well I trust this 30 year old gauge

Yes they suck. Unless someone spent real money for an engine analyzer. Rentals, good luck. LOL.

It’s not going to matter much — get close and maybe a smudge rich for mom and the kids.

Unless it’s a turbo. Then a whole new series of problems. LOL

 

[Tantalum]

So I went for a Christmas day flight and did some experimenting with different leaning procedures, my passengers were asleep and I had 40 minutes to kill so figured what the heck

The good old method of leaning until rough then advancing slightly seems the best. It's quick method and the EGT gauges tied out very nicely with where they should be.. but this method seemed more quick and effective than the slow tinkering and watching the EGT gauge

I did the leaning individually and found that rather than hearing any roughness I could readily feel a very slight yaw..

Also, since the Duchess has a 40 gallon and 30 gallon mark in the fuel tank my fuel burn was actually slightly less than I was budgeting for.. temps in both engines were 350/180 cht/oil.. that was good enough proof for me that the engines were as lean as I could reasonably get it

 

[Cervieres]

Yes, but is EGT really the best? Not sure how well I trust this 30 year old gauge

I did some multi in a Twin Commanche that had seen better days. You could tap the EGT gauge and the needle would swing randomly from side to side.

 

[GRG55]

I did some multi in a Twin Commanche that had seen better days. You could tap the EGT gauge and the needle would swing randomly from side to side.

Ah yes, the certified Mark IV calibrated index finger instrument tap. A timeless tradition.
Sometimes I think the Wright brothers would have covered more distance at Kitty Hawk, if they hadn't been preoccupied with doing exactly this.