Aircraft Engine Feed Pumps

[airbus eng]

Hi,

Would anyone with line maintenence experience be able to provide me with a ball park figure for the time that an engine feed pump is likely to spend in service on an aircraft. (Are they automatically removed from their cannisters and replaced at minor or major servicing intervals etc)?

Of particular interest would be A330/ A340 engine feed pumps.

Cheers.

[smudgethecat]

Ive never as far as i can recall replaced one due time expired , the only time we seem to replace them is when they start to give problems, niether can i remember ever replacing them on a big hangar check as a matter or routine.

[Blacksheep]

In these days of MSG3 maintenance schedules and mandatory reliability monitoring programmes there are 3 classifications:
1. Hard Life
2. Condition Monitored
3. On Condition
The majority of components, including Fuel Booster Pumps, are generally "On Condition" items and remain in place until they fail. There are very few hard life items in modern aircraft.

[airbus eng]

Ok, in that case, does the pump manufacturer give some kind of pump service life? If an airframe is built to serve around 30 - 35 years, im sure a pump is not designed to match that.

[Hand Shandy]

I`ve always replaced them on condition , although after the TWA incident and all the fuel tank bonding checks that ensued i remember replacing a few that failed insulation resistance checks with pumps that appeared to be OK in service .

[jettison valve]

airbus eng,

On request from FR-HiTemp (many moons ago!), we evaluated an A340-600 pump; I think they called it Mk100 at that time.
After only 2.000FH or so it showed serious signs of cavitation so that a mandatory hard time was on the table; thankfully, that never happened.

In the frame of this excercise, FRH asked us to remove our high-time main pump of the in-service design (Mk1 to Mk4 - can´t remember the exact type) for comparison. Based on our computer systems and the a/c delivery documents, I found a pump that had accumulated around 20.000FHs in a main position. I witnessed the teardown in Titchfield - and, wow, FRH gave me a hard time that I had sent them a young pump (they thought)! I almost had to swear that indeed the pump had served many, many hours pumping fuel.
Sometime during the teardown, their engineers found marks of corrosion at the impeller, convincing them about the true age of the pump. I was saved! ;)

So, to the best of my knowledge:
No scheduled removal of the engine feed / xfer / APU pumps on the A330/A340. The reliability of the FRH pump is really good (GEC-Marconi heritage, if am not wrong) - a lot better designed than the B747 crap!

One more piece of information: The A330 standby pump outboard of the collector cell may rot down standing in a water puddle... Keep an eye on it, as you will not notice its failure under "normal operating conditions"! :*

Cheers,
J.V.

[Vortechs Jenerator]

Quality information/answer. Need more of this on here:ok:

[airbus eng]

Thanks for all of your replies.

It seems common sense that if the pumps are still functioning in good condition 20,000fhs after being fitted, there is no point in replacing them. Interesting story regarding FR HiTemp, I am actaully looking at how you weigh up which technologies to insert into future fuel systems for a university final year project. (I have a s/w model and am doing a case study on engine feed pumps)

Coming from a systems design background, components will always be designed with an expected service life in mind, and I can understand FR Hi Temp's concern in the situation described. However, as Jettison Valve has shown, these are at best a good guide!

[jettison valve]

Let me add something to my previous post:
Concerning the discussed hard time for the Mk100 pump, FRHs and Airbus position was that the witnessed cavitation would "stabilize" over time. I had serious concerns about this - but apparently, they were right.
They did some minor changes to the design which helped for the "second batch", and the older pumps indeed never got so bad that they needed early replacement.

airbus eng,

What you need to take into consideration apart from the component properties, are the effects on aircraft level.
It is my understanding that we don´t care too much about the feed pumps because we have multiple redundancies, and most of the pump failures would become immediately evident (loss of fuel pressure).
For exactly the same pump, fitted in a different environment and without redundancy - for instance as a single pump on a Cessna supposed to fly from Hawaii to New Zealand ;) - I would set up a different maintenance programme!
Your project sounds interesting - do you need any more help? It´s been some time since I left university, but I am still interested in this "scientific stuff"... :ok:

Cheers,
J.V.

P.S.: You´ve run into
http://www.eatonaerospaceltd.com/fuel/Resources/026_2_Type8810boostpumpA330_340.pdf
for more (basic) information about your "patient", havn´t you?? :)

[Blacksheep]

I agree that, although system redundancy allows typical airliner booster pumps to be "On Condition", where there is no redundancy (e.g. the imaginary ETOPs Cessna example) "Condition Monitored" may be more sensible: as it would also be for that standby pump example.

[airbus eng]

Interesting points.

I am indeed looking at the project from an aircraft level perspective and the reason for the study is actually alligned with an integrated wing approach to optimally packaging systems to lead to higher efficiencies. Its a little bit beyond me to be honest and not really my area of interest but useful nonetheless.

I am in possession of the Eaton spec for the A330/40 Boost pump, was useful but did give me everything - which is why i posted in the first place.

[CY333]

I know a guy that broke FOUR pumps trying to get them out.
A supervisor actually and 2 tons of fuel just filled up the place.
It was an A320.
Dont ask me how he did it.
I am still puzzled