Question about Failure: L ENG PRSOV VALVE

[ck777 2]

Hey All,

 

I was hoping to have  a little help understanding the Failure L ENG PRSOV VALVE, which I just got.  I've been digging around the manuals and the forum but can't seem to find the information.

 

I came across a thread about HPSOV and Kyle made a really good statement about failures, "As far as the failure goes, remember that failures might not always be visible. The cool part of this simulation is that some failures are like icebergs. They might give a little bit of an indication from time to time on the surface (the EICAS or STAT page), but the real "danger" lies deeper. This, over time, may trigger other symptoms/failures."

 

Is this one of those failures that would trigger another symptom/failure?  I'm thinking "yes" since I just got  a BLEED OFF ENGL, even though it's on.  Since I'm flying happily at FL390, what happens now with this kind of indication?  I thought I read somewhere it can effect the reverse thruster of that engine.

 

I looked in the FCOM v2 Air systems chapter but perhaps I'm over looking or thinking this.

 

Any insight and information would be great.

 

Thanks!

C

 

 

 

[ecuflyer 13]

Well, there is no "L ENG PRSOV VALVE" message as such, The only one I can find is the "BLEED PRSOV L" status message. If that is the case then that message is there as any other status messages, mostly for maintenance action and to indicate that if the failure is not corrected, then before the airplane next flight, it has to be dispatched under the provisions of the MEL (minimum equipment list). It does no affect the flight crew or its operation, so technically as a pilot you don't have any action to do about it, or you don't expect any significant difference in operation related to that failure. If the case would be like a reverser would be inoperative because of that particular failure, then it would have had an associated EICAS caution or advisory message, which is not the case; so in short, no, you would not expect any engine reverser problem, they should work normally.

 

On the other hand the "BLEED OFF ENG L" it is an Advisory message and as such it is designed to alert the flight crew about some condition that may affect the operation of the flight, in this case this advisory message does not have any checklist actions associated with it, so it just to alert the flight crew about this particular situation, in this case that there is no bleed air coming from the left side. based on this, there is no action required, but there is something you as a pilot need to keep in mind and play a bit of "what if" scenarios involving possible decision making if you have a second failure...

 

Now if you want to get a little bit deeper about this failures while in flight, in the case of the "BLEED OFF ENG L" advisory message you may want to pull off the associated checklist, even although there is no actions associated, there is still an associated checklist that will tell you a bit more information about this, so you go ahead and select "CHKL", then select "NON NORMAL", then the very first subtopic on the left that says "BLEED OFF"... among other things i don't remember and finally you select "BLEED OFF ENG L". it will tell you this "the engine bleed valve is closed because of a system fault or the engine bleed switch is OFF". You know the bleed switch is not OFF so now you know that the engine bleed valve is closed because of a system fault and now you even now know what fault it that... it is the BLEED PRSOV valve failure.

 

Finally if you are curious and have some time you go next to the MEL and search for "BLEED PRSOV L" and you will learn that it is a status message, you already knew this and the applicable MEL is 36-11-01. You search 36-11-01 and you will learn a lot more about this failure. too long to list about its effects here, but i does not mention anything about the reverse being inoperative. You may have an 'ENG IDLE DISAGREE' message during descent but again that one will have no major effect on your operation.

 

Hope that helps...

 

Cheers

[ck777 2]

Hi Cristian,

 

Thank you for taking the time to explain this in more detail; it's really appreciated and helpful.

 

You are correct, I saw the L ENG PRSOV VALVE on the failures page on the FMC, not the STAT page.

 

Thanks for the info about the MEL, I found the FAA document and will explore that a little more.

 

My big reason to set failures is to dig deeper into the manuals and have a better understanding of the plane.  I was having a little trouble with this one, so thanks for the explanation.

 

Oh, as I was descending I got the HPSOV failure...good fun this plane is!

 

Thanks, C

[ck777 2]

I took a look at the MEL and had a question about it.

 

This might be a silly question, so bare with me.  If I'm cruising along FL390, how would I know that I received the PRSOV.  Does a pilot have access to the MEL(what is below) in the flight deck or would they be communicating with Operations/Maintenance while in the air?

 

 

 

 

M)(O) One valve (PRSOV) and/or the associated controller (PRSOVC) may be inoperative provided:

a)       Associated PRSOV is locked closed,

b)       Opposite engine bleed system operates normally,

c)       Associated engine bleed air switch remains OFF,

d)       Left and right bleed isolation systems operate normally,

e)       Center bleed isolation system operates normally,

f)         Both packs operate normally,

g)       Both outflow valves operate normally,

h)       Airplane remains at or below FL 350,

i)         APU is used as air source for center system hydraulic demand pumps for takeoff and landing, and

j)         Appropriate performance adjustments are applied.

[19dcavscout 39]

I know we carry the MEL (or REL is what we call them) with us at all times. In the event of a system failure that allows us to know what our limitations are. I would imagine a 777 crew would carry this and in your case a descent to FL350 or below is in order.

[mazelda 124]

I cant say for certain but it would be highly unusual for an aircraft to not carry a copy of the MEL

Some aircraft carry both parts,one of which is purely for  engineering  hence the (M) the other is the operational part (O)

They are generally worded quite blandly and can easily be interpritated differently by crews and engineering,and at times by different crews and engineers

[skelsey 765]

This might be a silly question, so bare with me.  If I'm cruising along FL390, how would I know that I received the PRSOV.  Does a pilot have access to the MEL(what is below) in the flight deck or would they be communicating with Operations/Maintenance while in the air?

 

I stand to be corrected: however, my understanding is that the MEL is valid only up until the point of dispatch (which will vary slightly dependent on legislation, but is generally the moment at which the aircraft first moves under its own power for the purpose of flight).

 

After that point, the QRH (Quick Reference Handbook) is what counts (usually (always?) available in paper form in the flight deck, but I believe the 777 Electronic Checklist system takes over most, if not all, of its function).

 

Therefore, if you get BLEED PRSOV L in flight, you look at the QRH (or electronic checklist, if available), not the MEL. In this case, it appears there are no further actions required -- so you do not need to descend to FL350, regardless of what the MEL might say: the QRH has taken over as the controlling document.

 

However, it might well be worth looking at the MEL to determine the impact of the failure on the aircraft's next sector, which may guide some of your decision making.

 

Having said all of the above, especially in the modern world of satellite communications/ACARS etc, most of the time (unless you're somewhere really remote and don't have SATCOM) you would have access to engineering support and advice from home base. Indeed, with the sophisticated systems monitoring in place these days, it's not unheard of for the engineers in Maintrol to know about a fault before the flight crew do!

[ck777 2]

Thanks everyone for your thoughts on this and explaining in more detail!

 

C

[mazelda 124]

Hiya guys

Simon you are on the money with your thoughts as soon as the a/c moves on its own the MEL is no longer applicable unless he/she then taxi's back on stand.

In which case it then does

As I said earlier MEL's are open to interpritation so crews will come back on stand rather than go as per the QRH drills which at time can cause massive problems on outstations for things that can ground an aircraft.that would normally be fine if the QRH was applied