Taxiing out with #2 and #4 - 748

[hkhoanguyen 8]

Hi, 

Quote

https://www.youtube.com/watch?v=mOxtGy1rgdQ&t=196s

In this video, I don't understand why they started pushing back and taxiing with only #2 and #4 ? as far as I know, #2 and #4 both provide breaking (normal and alternate) but only #1 provide nose and body steering, #2 does not, how could they steer the plane without ENG #1 ?

Someone could explain me ?

Thanks

Edited January 26, 2019 by hkhoanguyen

[Heffron 29]

I think they had HYD 1 on the electrically powered AUX pump, which provides hydraulic pressure without ENG 1 running.

 

EDIT: I actually watched the video now, so my initial reply is kind of false i guess. I guess the #1 Demand Pump is running on bleed air from either the APU or the 2 running engines. 

Edited January 26, 2019 by Heffron
actually watched quoted video.

[windshearDK 52]

From a real world 744 and 748 pilot he told me that they always taxi using #1 and #4 due to hydraulics etc. here's what he wrote me:

Quote

"“On two engines it’s always the outer 2 (#1 & #4) [that are running] because nose and body gear steering are on hydraulic system 1 and primary brakes are on system 4”

When asking about the -8 he said:

 

Quote

"Same deal. Systems are very similar on the -8”"

I think the PMDG is a bit wobblier to taxi if I taxi on #2 and #3

[vc10man 732]

Great heads up. One question though, can you ask your 744 and 748 friend, when exactly do they start #2 and #3? During the taxi, or nearing the threshold, because it does take a while to spool-up?

[Heffron 29]

But the questions remain, why did they start 2 and 4 instead of 1 and 4? And how is the HYD 1 system being pressurized if eng #1 is not running.

[windshearDK 52]

17 minutes ago, vc10man said:

Great heads up. One question though, can you ask your 744 and 748 friend, when exactly do they start #2 and #3? During the taxi, or nearing the threshold, because it does take a while to spool-up?

Mostly 2 engine taxi is from after landing until the parking position/gate... The instance he was talking about was from parking to deicing... I guess they turn them on as soon as the deicing has been completed

[windshearDK 52]

7 minutes ago, Heffron said:

But the questions remain, why did they start 2 and 4 instead of 1 and 4? And how is the HYD 1 system being pressurized if eng #1 is not running.

Yeah someone sent me that video also asking why... I don't know why. The answers I got was from a pilot flying for Atlas Air Cargo... So various airlines could have different procedures, but the reasoning behind the procedure my friend does is solid I would say... Don't really have to understand why people do things differently.

Another pilot friend of mine flies the 77W/77L and 77F and he didn't know that you have to do step climbs using vnav or FL/CHG as it helps to prevent icing in the fuel systems. This was a Boeing decree even after they updated the fuel filter because of the crash investigation conclusions in the BA crash at LHR where a 772 flamed out on final app.

There are also some 777 pilots that are not aware of the technique of turning on the HYD on the 777 to prevent spill over...

When the logic behind a procedure fits the systems of the aircraft I tend to favor that procedure over what others might or might not do...

[vc10man 732]

Great answers, Boaz. You never stop learning in this Forum even if you are an experienced simmer.

Just as I am watching a very instructive real-world ex-Airtours 757-200 from EGCC-Dalaman. So much know-how to glean there that can then be applied to the cs757-200v3

Edited January 26, 2019 by vc10man

[windshearDK 52]

2 minutes ago, vc10man said:

Great answers, Boaz. You never stop learning in this Forum even if you are an experienced simmer.

And in real life! I learn a lot from my friends but sometimes I can teach them a little too! That's why I love aviation! Always more learning to do!

[vc10man 732]

18 minutes ago, windshearDK said:

And in real life! I learn a lot from my friends but sometimes I can teach them a little too! That's why I love aviation! Always more learning to do!

👍👍

[Heffron 29]

1 hour ago, windshearDK said:

There are also some 777 pilots that are not aware of the technique of turning on the HYD on the 777 to prevent spill over...

Also applies to the 747. Pressurize #4 first and depressurize last to prevent fluid transfer between systems. 

[Patco Lch 1,465]

Do you do the before taxi check list before taxi or after all engines are started in which case it would be the after start check list? I know that sounds like a nonsensical question but being an FS2 Crew user it has left me wondering. Also same question applies to setting TO flaps.(In non icing conditions)? 

[vc10man 732]

I use FS2Crew too, and using only the Button Version, but I have no issues with the Before Taxi Checklist, as well as it being available in the 747-8i checklists

[Patco Lch 1,465]

2 hours ago, vc10man said:

I use FS2Crew too, and using only the Button Version, but I have no issues with the Before Taxi Checklist, as well as it being available in the 747-8i checklists

But if you do a two engine taxi I was wondering if you wait until all engines are started ( at the runway I assume ) before the after start check list and TO flaps are set ? Wonder what the RW procedure is.

[windshearDK 52]

3 hours ago, Heffron said:

Also applies to the 747. Pressurize #4 first and depressurize last to prevent fluid transfer between systems

but you don't have the same 4 hydraulic systems like in the T7... How do you then turn them on to prevent spill?