quiet noise!!??

hmm...

[quote]Tell bmi that if they single engine taxi on No1 and turn the yellow electric pump on, that should stop the dog barking...:=[/quote[

Now SOP at EZY by the sound of things...no barking on recent late sectors EGAA-EGSS :)

That is exactly what we do and have done since we introduced single engine taxi out.

Having flown in various Airbii (pax) and never having noticed the barking, and never having heard of a PTU, I had a bit of a Google and came across this site/ | Ozten Network Home | Aviation site :)

Two things- It informed me that a PTU does not actually transfer hydraulic fluid, so can anyone enlighten me as to how it works (in layman speak) :confused:

The other thing is that while the site is in, I believe, Turkish, all the articles / info sheets are in English. If I study hard and find a kindered soul who will let me have a go in an A320 simulator, will I be able to fly the thing? :}

Maxbert

Maxbert

In (I hope) laymens terms. a PTU uses hydraulic pressure from 1 system to drive a transfer shaft. The non pressurised system has an impellor in it which thereby pressurises the second system with no fluid transfer between the two systems.

An analogy would be hydro electric power - water under gravity (in this case hydraulic fluid at 3000psi) drives a shaft which turns a turbine (in this case an impellor sitting in the hydraulic line) generating electricity (in this case hydraulic pressure). There is no mixing of input and output sources.

HTH

PTU.
Power Transfer Unit is an hydraulic motor driving an hydraulic pump mounted on a common shaft.
The ones on Airbus are one way only but the ones on the DC10 are called Reversable Motor Pumps and can work either way.
Hope this helps.

TopBunk, dixi, many thanks!

From my reading, Airbus A319 / A320 seem to have such a device, is it not common to all A/C in one form or another?

Maxbert

PTU.
Power Transfer Unit is an hydraulic motor driving an hydraulic pump mounted on a common shaft.
The ones on Airbus are one way only but the ones on the DC10 are called Reversable Motor Pumps and can work either way.
Hope this helps.

PTU and RMP´s are the same thing

Wasn't scraps a boy dog?:E

Wirelock.

The PTU's on the A300 are not reversable.

ie. Green system can power Blue or Yellow but not the other way around.

I'm not sure about the later Airbus types.

On the A320 family the PTU allows the yellow system to power the green and vice versa.

I've said it once, and I've said it a hundred times.................

We need a permanent "Sticky" for "Strange Airbus noises and other things that go bump in the night!":ok:

Moderators please note!:ugh:

Regards,

Old Smokey

I once had a positioning colleague enter the flight deck after landing, asking if everything was alright, because he heard the PTU barking continuously during the whole approach.

Also heard similar comments from cabin crew on a different flight, with a different A319 aircraft.

On both occasions there were absolutely no indications of any hydraulic problems in the flight deck. So the PTU seems to be running a0t times without any indication to the pilots. I haven't seen that explained yet ;)

Dunbar & Ground Star - We certainly don't taxi single engine with the yellow elec pump off! We are not Muppets.:D

why the ptu runs!!
 

The PTU is made up of a variable displacement unit coupled to a fixed displacement unit. The variable displacement unit is connected to the yellow hydraulic system. The fixed displacement unit is connected to the green hydraulic system. Displacement of the variable displacement unit is varied to maintain the required running and breakdown pressure differentials between systems. Displacement of the variable unit is controlled by means of a control which senses the system delta pressure.
The variable displacement unit is at maximum displacement during the power transfer from the Yellow to the Green system. Then it is at minimum displacement during the power transfer from the Green to the Yellow system.
The variable displacement unit includes a hydraulic servo valve and a variable cam. The servo valve gets input from the pressure differential, which starts the PTU.

if the servo valve malfuctions it is possible for the ptu to operate without an ecam indication on the flight deck

hope this helps

some more info

to display the G to Y PTU ECAM indication, it is necessary to have the condition Y sys press

lower than G sys press by more than 200psi. This condition is not required for the display of the Y to G

PTU ECAM indication. So, as soon as the Y EDP is selected off, the PTU starts faster than expected

and therefore the Y sys press has no time to droop the pressure.

This is apparent in the ECAM logic manual