2 engine taxi in a 4 engine jet?

[91100 100 set]

Just a question for all the Avro, 747, and A340 people (or anybody else who flies a 4 engine airplane).

When you're taxing around trying to save a little gas, and if you shut down an engine (or two), which ones do you shut off? 1 and 4? 2 and 3? Aside from any system specific requirements (say you need hydraulics from an engine pump on a given engine or whatever), is there any advantage to having the "inboards" or the "outboards" running? I imagine that the outboards might make it a little easier to manuever if you need it, but the inboards might be easier to actually manipulate the levers.

Just curious, thanks...

 

[Bjammin]

The Cathay A-340 guys shut down 2 and 3. I have seen C-130 guys shut down 1 and 4. I'm sure they have reasons for both. I'll tell you the 747 practice after ground school, but i'm sure someone will beat me to it.

 

[FearlessFreep]

747 you start by shutting down #3, then depending on weight shutdown #2. #1 & #4 engines are left running as they power the primary and secondary braking system. The Reserve Brake system is on #2 and additionally there is a electric pump on the #4 hydraulic system. This is only available if neither the air driven or engine driven hydraulic pump on the #4 system are operating. All hydraulic systems on the 74 are separate and cannot be interconnected. This is on the Classic, I don't know about the 744.

 

[AV8OR]

Dc-8

When taxiing on 2 it's #2 & #3. So on start-up, obviously 2 & 3, and after landing and two minutes, shut-down 1 & 4. 2 & 3 for the hydraulics.

 

[4fanman]

Avro

When I was at Mesaba we would occasionally shutdown 1 and 4. 2 and 3 were used for hydraulics and the APU for electrics/packs. This was procedure was prohibited at night. They may have changed procedures since I left.

4fm

 

[146guy]

Why do they prohibit shutting down #1 & #4 at night? When we are operating at higher weights we usually only shut down one motor to prevent using more than 60% N2 (if we have to stop then go again), otherwise you end up waiting two minutes below 60% before shutdown on the BAc.

 

[4fanman]

The night prohibition was due to the fact that if the apu crapped out then you would lose electrics. Now lets see if I remember my systems. When you loose electrics, the standby generator (hydraulic powered) kicks on and when that happens some hydraulic services are shed, mainly the nose-wheel steering. Now there you are at night, getting to choose between staying at emergency power level (battery) with nose-wheel steering, or getting some elecs back without steering. Gotta love British engineering.

NWA was too cheap to get the 2nd battery, so battery starts are not an option on XJ's AVROs.

 

[146guy]

You mean the Garrett 150's crap out from time to time? hahaha Nice job with the systems recall, yeah it's the green hydraulics that run the standby gen and wouldn't you know it, the green runs the nose wheel steering too. Like you said gotta love British engineering! How long did you fly the avro?

 

[LR25]

On the DC-8 you taxi on 2 and 3. Hydraulics on 2 and 3 only.