crossfeed valve check
crossfeed valve check
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Not sure what airplane you are talking about, but crossfeeding is used for feeding from a different tank for an engine out or balancing wings if burn is uneven among other things. 747 classic has bigger tanks on the inboard section of the wing (and center if a big fuel load) so fuel is fed to outboard engines from here when necessary.
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ETOPS
the fuel crossfeed check is done on 737 and I am assuming all twin engine jets as part of a set of procedures to allow a comapany to operate greater than 1 hour single engine flight ( approximately 400 nm 737) up to 2 hours 737-400 and 3 hours 737-800 from a suitable airport for landing. If you lose 1 engine you will need to access the fuel from the other tank and checking the crossfeed valve functions will be a pre requisite to allow the next sector to be operated extended range. The tech log entry records that the check has been made
The most obvious reason on the 737 is to check that in the case of an engine failure you can feed fuel from the dead side to the live engine. If you cannot it is a no go item. Marking this in the TLB is a means of making sure people carry out the check for example on extended overwater flights. In Europe there are not many sectors where this would be critical so my company does not require it. If you are in Russia maybe it is different.
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Thanks, cf. It's obviously the crossfeed is checked to be sure the fuel from any tank can reach the operating engine in critical point, but at what stage does this check is usually done: preflight or inflight?
I don't remember the references but I think it may be concerned long-houl flights especially with prolonged operation in air-masses with very low temperatures which can affect the valves ability to operate.
I don't remember the references but I think it may be concerned long-houl flights especially with prolonged operation in air-masses with very low temperatures which can affect the valves ability to operate.
Last edited by Yury; 10th Nov 2009 at 18:15.
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In my ETOPS experience it was 'required' to be done towards the end of the ETOPS sector which satisfies the 'next sector' ETOPS requirement, but if the a/c has come off an non-ETOPS sector you would have no idea until the engine failed.....
Having found 2 x-feed valves actually seized in BA 737's in my time, I always checked it EVERY flight pre-flight anyway.
Having found 2 x-feed valves actually seized in BA 737's in my time, I always checked it EVERY flight pre-flight anyway.
The crossfeed valve on the 737 is checked for ETOPS in the cold soaked condition - if the initial leg is non-ETOPS (i.e. an overland segment before heading into the ETOPS sector) then it can be done at the end of that leg, otherwise it is done before descent on the previous leg.
The 737 performs this check because it is fitted with a single crossfeed valve. The 767 (which is fitted with two valves) isn't required to perform a check (at least when I was flying ETOPS in Australia).
In the same sense, the 737 runs the APU throughout the ETOPS sector, to guarantee two sources of power after an engine failure - but the 767 doesn't need to, as it has a RAT (Ram Air Turbine).
The 737 performs this check because it is fitted with a single crossfeed valve. The 767 (which is fitted with two valves) isn't required to perform a check (at least when I was flying ETOPS in Australia).
In the same sense, the 737 runs the APU throughout the ETOPS sector, to guarantee two sources of power after an engine failure - but the 767 doesn't need to, as it has a RAT (Ram Air Turbine).
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Embraer 190 has a RAT but must run the APU for ETOPS. Also has the XFEED valve check and was required to have a second electrical system for operating the xfeed valve.
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Originally Posted by cb
The crossfeed valve on the 737 is checked for ETOPS in the cold soaked condition
BOAC - I thought I was agreeing with you! Just explaining why it's normally checked on the previous sector - because that is when it's cold soaked and (presumably) the most likely to freeze up, if it is going to freeze up. 
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I think the answer for Yury is that we have not come up with any regulation requiring its check, but that it is a good idea to check it before an ETOPS sector, preferably on the ground where it can be fixed if required as well as in the last hour of cruise for the next ETOPS sector. Basic airmanship, I would suggest. Also a good idea to give it a quick check after a long leg pre-ETOPS (if you do that). I do not think it is practical to have it checked in the air on the trip before an ETOPS flight UNLESS it is written in the Ops Manual as a check EVERY flight, since I do not know of any crew that will reliably know the a/c is next departing on an ETOPS flight.
The B767 actually has an APU which is certified to start at high altitude and cold soaked. It is checked regularly when maint puts a notice in the tech log to start the APU nn minutes prior to descent.
The fact that the B767 also has a RAT has nothing to do with not running the APU continuously on an ETOPS sector.
As for checking the cross feed valve every sector, we always expected that it would be worn out the one time we needed to use it in anger. Later deliveries came with two cross feed valves, hence no in flight check required.
The fact that the B767 also has a RAT has nothing to do with not running the APU continuously on an ETOPS sector.
As for checking the cross feed valve every sector, we always expected that it would be worn out the one time we needed to use it in anger. Later deliveries came with two cross feed valves, hence no in flight check required.
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My research has been finished on the Australia CASA AIRWORTHINESS DIRECTIVE AD/B767/220.
Requirement: Unless previously accomplished, amend the aeroplane Flight Manual by including a statement to the following effect:This aeroplane should not be operated beyond the single engine cruise range of an
adequate aerodrome whilst on direct fuel feed, unless a satisfactory operational check of the fuel crossfeed valve has been carried out. This check should be performed during the last hour of the previous flight or prior to reaching the above critical phase of the extended range flight after adequate cold soak time at cruise altitude to include temperature effects on valve performance.
adequate aerodrome whilst on direct fuel feed, unless a satisfactory operational check of the fuel crossfeed valve has been carried out. This check should be performed during the last hour of the previous flight or prior to reaching the above critical phase of the extended range flight after adequate cold soak time at cruise altitude to include temperature effects on valve performance.
Last edited by Yury; 11th Nov 2009 at 08:52.
As outlined in our operations manual based on Boeing procedures (AD 2002-19-52 etc.) During climb or cruise set one centre tank fuel pump to off when centre tank fuel quantity reaches 950kg. Open crossfeed valve to minimise imbalance. Set remaining center tank pump to off and close crossfeed valve when MC and Fuel annunciator light iluminates. All dating back to the Thai explosion in BKK. Mod to avoid this being rolled out but procedure still in place.