B777 - autoland not avail if L Hyd inop

[extricate]

Hi,

I understand that autoland will be disabled in the event of L Hyd down. How about in the event of HYD PRESS PRI L where L PRI HYD switch will be turned off and the L system is now only supported by demand pump, will autoland be available?

I'm asking because for HYD PRESS PRI R, QRH mentions: "The right hydraulic demand pump may not provide sufficient pressure for all systems during the landing phase".

Any idea?

Thanks

[sleeve of wizard]

Can you do an auto land with the LH engine shutdown? Remember the primary pump is engine driven.

[extricate]

Yes, thats why I asked if a demand pump is capable of doing an autoland

[birdspeed]

If I’m not mistaken, if it’s the L Hyd which has failed, there is less elevator authority. As 2 out of 4 elevator PCU’s are powered from the L system.

i could be wrong.

[Papa_Golf]

My understanding is that the right hyd powers more component (normal brakes) than the left one hence the fact that it may not provide sufficient pressure for all systems during the landing phase, as stated in the QRH, and also that on the ground the right demand pump run continously with its selector in the auto position.

Viceversa I don't see an issue with autoland and the left hyd being pressurized by its demand pump only.

[wiggy]

Yes, thats why I asked if a demand pump is capable of doing an autoland

I think "sleeve of wizard" dropped an excellent hint/tip, but I'm not sure if your "yes" is an answer to "Can you do an auto land with the LH engine shutdown?" or an answer to "Remember the primary pump is engine driven."

If Boeing state an autoland is acceptable post an straight forward engine rundown/ shutdown on the T7 then I'd suggest that answers your question...what does your FCOM say on the subject of engine failures?

[extricate]

I think "sleeve of wizard" dropped an excellent hint/tip, but I'm not sure if your "yes" is an answer to "Can you do an auto land with the LH engine shutdown?" or an answer to "Remember the primary pump is engine driven."

If Boeing state an autoland is acceptable post an straight forward engine rundown/ shutdown on the T7 then I'd suggest that answers your question...what does your FCOM say on the subject of engine failures?

Not sure if I mis-understood, my original question assumes left engine is still running, just that Hyd L Pri is down for some reason. By system logic, demand pump will kick in but does that suffice for Autoland? Nothing to do with left engine shutdown

[wiggy]

I understand your original question didn't mention engine "out", but that example was given by "sleeve of wizard" in his/her reply of as a credible, simple situation where you could end up with an intact hydraulic system, no Primary pump, and the system is only being powered by the demand pump.

So moving on from that if you know whether or not single engined autoland is approved of the T7 (answer will be in the QRH and/or FCOM) you'll have your answer to the question you posed in your opening post.

[extricate]

I understand your original question didn't mention engine "out", but that example was given by "sleeve of wizard" in his/her reply of as a credible, simple situation where you could end up with an intact hydraulic system, no Primary pump, and the system is only being powered by the demand pump.

So moving on from that if you know whether or not single engined autoland is approved of the T7 (answer will be in the QRH and/or FCOM) you'll have your answer to the question you posed in your opening post.

Ah ok, i get what you meant now...trying to reverse engineered the problem but it's a little out of context because for the B777, with the L hyd system totally down, autoland cannot be enacted due to the redundancy for hydraulic source in the elevator. The elevator is powered by 2x L Hyd, 1x C Hyd and 1x R Hyd, so without the L hyd, eicas will show "No Autoland" when it self-test.

Now my question is asking what if pri system is down but demand system is in place to supply the left side, will the demand pump be sufficient to support the autoland criteria? I wonder if anybody ran this in the sims and would be willing to share?

[ASRAAMTOO]

Ah ok, i get what you meant now...trying to reverse engineered the problem but it's a little out of context because for the B777, with the L hyd system totally down, autoland cannot be enacted due to the redundancy for hydraulic source in the elevator. The elevator is powered by 2x L Hyd, 1x C Hyd and 1x R Hyd, so without the L hyd, eicas will show "No Autoland" when it self-test.

Now my question is asking what if pri system is down but demand system is in place to supply the left side, will the demand pump be sufficient to support the autoland criteria? I wonder if anybody ran this in the sims and would be willing to share?

So as hinted at in previous posts, IF the left engine failed would you also lose left system hydraulics. If the answer to that is no, then where would the system pressure come from, and following on from that can the 777 autoland single engine?

Edit: To save you looking it up! It can.

[sleeve of wizard]

Boeing issued the following notice of errata in Feb 2018,NNC 13 created separate HYD PRESS PRI L checklist because of changes to the procedure for the HYD PRESS PRI R checklist. Notes were also added to HYD PRESS PRI R checklist to show items that may be inoperative.

The L HYD DEM Pump will be capable of supporting the demand for the flight controls, the note regarding the LH Thrust reverser may be inoperative is caused by the increased demand to actuate the respective reverser, this increased demand could be greater than the supply capability of the demand pump.

NOT ALL PUMPS ARE CREATED EQUAL.