Sign in to follow this  
bob34

Position of Hydraulic Switches During Startup

Recommended Posts

Most engine start procedures I've seen and followed have both Engine Hydraulic Pumps ON - and both Electric Hydraulic Pumps OFF

 

m5y74Nm.png?1

 

Then I stumbled on this YouTube video and noticed he has the two left switches OFF and the two right switches On while starting Engine 2.

See it at the 1:30 mark in the video:

 

https://youtu.be/ae20L78imO4?t=1m20s

 

Is he doing it right? Is he doing it wrong? Does it matter? What's the difference?

I thought the engine pumps should always be on to preserve the solenoid life...   perhaps that's trivial.

 

Anyway... the video made me curious.

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Hi Bob;

 

I don't know if what he is doing is right or not. But, there is a channel at YT (https://www.youtube.com/user/My737Channel/featured) from a 737 pilot. I wrote to him some months ago, asking about the 737 startup.

 

This is what he wrote in reply about the hyd pump:

 

"Regarding the hyd

pumps, 1 and 4 (ENG1 and ENG2) remain on at all times (to prolong solenoid

life). 2 and 3 (ELEC2 and ELEC1) are turned on before the engines start, and

off after the engines shutdown."

 

So, I'm using this procedure since then.

 

I hope I could help.

Share this post


Link to post
Share on other sites

 

 


Then I stumbled on this YouTube video and noticed he has the two left switches OFF and the two right switches On while starting Engine 2.
See it at the 1:30 mark in the video:

 

Probably simulating something like the SWA procedures. Those SOPs are usually related to an operator having the older type of 737 at the same time as the NG as well, and carrying the old procedure for commonality.

Share this post


Link to post
Share on other sites

Finger happy pilot... That's gotta make you feel safe doesn't it?!

 

Anyway, it's done for one or two reasons:

1) Fleet commonality, like Kyle said, and/or,

2) Pushback operations are conducted without the Nose Wheel Steering system bypassed.

 

Most <but not all> airlines operating an NG only fleet will have all hydraulic pumps on prior to pushback.

Share this post


Link to post
Share on other sites

Probably simulating something like the SWA procedures. Those SOPs are usually related to an operator having the older type of 737 at the same time as the NG as well, and carrying the old procedure for commonality.

 

 

Finger happy pilot... That's gotta make you feel safe doesn't it?!

 

Anyway, it's done for one or two reasons:

1) Fleet commonality, like Kyle said, and/or,

2) Pushback operations are conducted without the Nose Wheel Steering system bypassed.

 

Most <but not all> airlines operating an NG only fleet will have all hydraulic pumps on prior to pushback.

 

Completely makes sense.... and yeah, the finger happy pilot thinks because he's done it 500 times he won't miss anything.

So to conclude, we put the electric switches ON before engine start rather than after?

Share this post


Link to post
Share on other sites

 

 


So to conclude, we put the electric switches ON before engine start rather than after?

 

That's how Boeing recommends it, so that's what I'd go with.

Share this post


Link to post
Share on other sites

Is he doing it right? Is he doing it wrong?

 

It depends on who he works for.  Different companies, different procedures.  We turn on all four hydraulic pump switches before pushback and start.

 

Edit:  To be exact we only turn on the two electric pumps prior to push and start.  The engine driven pumps are left on all the time unless an abnormal checklist calls for it to be turned off, so they should already be on.

Share this post


Link to post
Share on other sites

Hi guys.

 

Operator specific, during the initial startup we select all hydraulic system on, this helps identify any leaks during the walkaround

 

Prior to pushback a bypass pin is installed to the nosewheel, this isolates the hydraulic system to the nosewheel steering and prevents inadvertent movement of the nosewheel.  We're a little different in that our SOP's instruct us to turn off all SYS A pumps prior to push and start, this adds an additional safety net from unintentional nosewheel movement during pushback.

 

 

Share this post


Link to post
Share on other sites

Hi guys.

 

Operator specific, during the initial startup we select all hydraulic system on, this helps identify any leaks during the walkaround

 

I am always a little bit uncomfortable being in the wheel well when a hydraulic pump is on.  It would be a real mess in there if a line were to break under pressure while you are in there.  We usually have the pumps off during the preflight but occasionally there will be one on if it's windy.  Granted, the odds are extremely slim but I can't help but picture that in my head while I'm in there.

Share this post


Link to post
Share on other sites

I am always a little bit uncomfortable being in the wheel well when a hydraulic pump is on.  It would be a real mess in there if a line were to break under pressure while you are in there.  We usually have the pumps off during the preflight but occasionally there will be one on if it's windy.  Granted, the odds are extremely slim but I can't help but picture that in my head while I'm in there.

 

Joe - what does hydraulic pressure do for you on a windy day? Do the control surfaces stiffen up so the wind isn't pushing them around?

Share this post


Link to post
Share on other sites

Joe - what does hydraulic pressure do for you on a windy day? Do the control surfaces stiffen up so the wind isn't pushing them around?

That and it can help IRS alignment if you were not smart enough to realize before shutdown to do a quick-align.

Share this post


Link to post
Share on other sites
Then I stumbled on this YouTube video and noticed he has the two left switches OFF and the two right switches On while starting Engine 2.

 

 

We're a little different in that our SOP's instruct us to turn off all SYS A pumps prior to push and start, this adds an additional safety net from unintentional nosewheel movement during pushback.

 

So this matches, I would say! B) 

Share this post


Link to post
Share on other sites

So this matches, I would say! B)

 

It matches that one SOP, yes.

 

It may surprise the sim crowd, but airlines do actually operate aircraft differently. This is one of those cases. I think it's entirely superfluous unless the bypass pin is damaged, or missing; or the internals aren't functioning properly. In those cases, follow the alternate procedure. Seems pretty common sense to me, but I'm sure those operators (and the pilots who work there) will provide some justification for what they do.

 

It has some merit, but so does not messing with the switches (forgetting to turn them back on as an example - not incredibly dangerous by itself, but now you're off the ground with a single system running the whole show).

Share this post


Link to post
Share on other sites

I forgot to turn the A pumps on one flight and then wondered why my left side AP would not work. B side was fine. Finally figured out why. D'oh!

Share this post


Link to post
Share on other sites

The 'before taxi' checklist is the last procedural chance to detect incorrect configuration of the hydraulic pumps. Ngx simmers should call for the checklist after all the 'before taxi' items are completed and just prior to calling for taxi approval.

 

The normal checklists are found in the qrh.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this