Originally Posted by joepilot50

Decent tailwind will blow engine #2's exhaust into the inlet on the 737.

When that happens, I do switch back to normal config and opt for 30% N1 when possible.

But I don't outright object to taxiing out or in on the APU bleed. Will give it a shot and if we start to smell exhaust, go to Plan B. But APU bleed taxi is always Plan A in hot temps.

Solution is obviously shut down number 2 if you decide to SET, but depending on which way you turn for the gate, can make your job fun by always electing to shut down #2.

I am not against SET. I have toyed around with it on the NG. Obviously it is no issue on the Max even when heavy( I have set a Max at 170,000 lb. and it was easy on flat ground at least). Only issue with the Max is just timing the other engine given how long it takes to start the LEAP's. When I had that 50 minute taxi in ORD in an NG, it was a pain to SET. Getting it moving from a standstill required ~50% N1 on the running engine and it was slow to accelerate. Can't recall the weight, but it was less than 155,000 lb. as that is my cutoff on whether I SET at all through my playing around. And as stated the CEFA app stated it only saved 100 lb. Didn't really prevent a RTG or diversion. Now again 2000 flights saving 100 lb on taxi adds up for the company. But just looking at my flight, it was nothing.

When the NG is below 140,000 lb. does it seem happy to SET. 140,000-150,000 lb depends on how flat it is. Even taxing on Kilo on the echo echo route can require 35-45% N1 on the running engine to maintain speed.

Originally Posted by joepilot50

Decent tailwind will blow engine #2's exhaust into the inlet on the 737.

Originally Posted by BusBoi

One of my friends is an AA 73 captain and he said there's a lot of cultural opposition to taxi on one, and also they have pretty strict taxi thrust limitations that are hard to work with for the 737NG. At Spirit we used to have a 40% limitation, which was removed around the time I became a captain. Definitely made it easier as sometimes 40% just didn't cut it.

But yea, I've been on AA where we had a 40 minute taxi out and they ran both engines the whole time. That's fuel you could have in your tanks and could make the difference between diverting or not later in the flight.

Originally Posted by Name User

Yeah on 737 the only way I'm running the packs off the APU is if #2 is shut down. I refuse to breathe unfiltered exhaust.

I use 155k as well. SET taxi out on the NG is almost impossible to do even at that weight with the 40% restriction.

Originally Posted by cornerpocket

Don’t even need a tail wind with the APU Inlet directly downstream of #2 exhaust. A tailwind will amplify the odor, though.

Originally Posted by joepilot50

The only time I really notice the fumes from #2 is with the tailwind.

Crosswind/headwind, I can be on the APU bleed with #2 running with no issue most of the time in terms of breathing engine exhaust.

40% restriction no longer exists in the AOM. It just now cautions us not to use excessive thrust in congested areas and look at the 7 pages if SET in the ramp isn't allowed.

Originally Posted by Judge Smails

The other thing is AA needs to upgrade the software to allow for SETWA (Single Engine Taxi Without APU) on the 320's. Single engine taxiing with the APU running doesn't do much to save fuel. We have a cultural problem here when it comes to fuel usage in general with tens of millions of $$ wasted every quarter.

Originally Posted by Name User

The the final straw for me was a DFW chief issuing an F4(?) message telling everyone to not start the APU until cabin temps hit 85*, while sitting in their DFW office that was so cold they had a space heater under their desk.

Originally Posted by Judge Smails

The other thing is AA needs to upgrade the software to allow for SETWA (Single Engine Taxi Without APU) on the 320's. Single engine taxiing with the APU running doesn't do much to save fuel. We have a cultural problem here when it comes to fuel usage in general with tens of millions of $$ wasted every quarter.

Originally Posted by Name User

AOM 5.3.1. There is absolutely a 40% restriction.

It used to be 35/40/45, they then changed it to a blanket <40% in ramp areas. Personally, I'm not going to go over that due to being able to defend my position. You hurt someone the first thing the chief and legal is going to ask is how did you clear the area behind the jet and how can you see behind it? There is no defense IMO.

Have you ever been jet blasted on the ramp? I was blown 50 feet into a blast fence, my glasses and vest blown off, my eyes in pain from the heat, due to a 320 SE taxing out of the ramp..

Originally Posted by joepilot50

Thanks for the reference.

Not a hard limit, just requires coordination with ramp/ground crew before disconnect to verify area behind is clear before going above 40%.

I won't fault you though for treating it yourself as a hard limit as not wanting to trust ground crew or a person with a camera to say what is clear to go above 40%.

Originally Posted by JulesWinfield

Pretty sure it is more involved than a software update.