HorizonGirl From Canada, joined Mar 2005, 781 posts, RR: 17 Posted (8 years 1 month 2 weeks 6 days 21 hours ago) and read 11019 times:
I am sorry if this topic has been previously discussed,
but I did a forum search and nothing turned up. I tried asking this
in an other thread, but it was soon after locked.
My question is why dose the A320 PTU "Bark?"
I know how it works, what it is, and that some people get
quite nervous when they hear it.
But what is it exactly that makes it make those impossible to ignore barks?
Thank you for any help that you may be able to provide.
CactusTECH From , joined Dec 1969, posts, RR: Reply 3, posted (8 years 1 month 6 days 15 hours ago) and read 10611 times:
The PTU is mechanical pump that links the yellow and the green hydraulic systems. It is energized when either system has been turned off( ex: one engine off) it produces a loud high frequency noise when it turns and produces 3000 psi hydraulic pressure for oppsosite system.
Troubleshooter From Germany, joined Feb 2005, 423 posts, RR: 5 Reply 4, posted (8 years 1 month 5 days 23 hours ago) and read 10565 times:
I think, the noise is produced by the fast moving (rotating) mechanical components inside the PTU. This leads to high frequency vibrations which are translated by the attached plumbing and PTU mounts.
All PTUs I know can be recognized by a loud "barking" sound. So I assume the noise is related to the PTU design and not only a A320 specific noise.
Klaus From Germany, joined Jul 2001, 20845 posts, RR: 55 Reply 5, posted (8 years 1 month 5 days 17 hours ago) and read 10547 times:
One forum member has once explained that Airbus explicitly wanted to have the PTU sound clearly audible to make troubleshooting on the ground easier. I don´t know if that´s exactly correct, but it might be an explanation. Newer versions are reported to be somewhat less noticeable (also from earlier threads).
Fadec From United States of America, joined Jun 2004, 45 posts, RR: 0 Reply 6, posted (8 years 1 month 5 days 17 hours ago) and read 10547 times:
The reason it "barks" is because it switches on and off so quickly. As pressure drops it comes on just long enough to build the pressure back to 3000 psi. Once that is done it shuts off until the pressure drops again... in about 5-15 second intervals normally, depending on how good the pressure bleed down rate is on that particular aircraft.
If you lower the flaps for instance the barking will stop and you will hear the pump run continuously (which is also quite loud) until the pressure is built back up after system demand has stopped.
I believe the A320/319 is the only aircraft you can hear the PTU so distinctly during normal operations. The 757/767 ETOPS for instance, it is heard only with a system failure. I've personally only heard it during maint. test's. Most non-ETOPS aircraft don't even have a PTU.
MD11Engineer From Germany, joined Oct 2003, 13328 posts, RR: 64 Reply 9, posted (8 years 1 month 5 days 9 hours ago) and read 10497 times:
All hydraulic pumps make noise, on engine driven pumps it is usually drowned by the engine noise, but did anybody in here ever stick his head into the "B" system compartment of a 727? You´ll need ear protection because of the racket the two electric driven pumps make. The same applies to the R/H wheel well of a MD-11.
F-WWAI From Andorra, joined Dec 1999, 131 posts, RR: 0 Reply 20, posted (8 years 3 weeks 3 days 7 hours ago) and read 10231 times:
the PTU is there to transfer hydraulic power from Green to Yellow or from Yellow to Green hydraulic system, but without exchange of hydraulic fluid.
It's a motor/pump power reversal configuration.
While normal system pressure is 3000 psi, the Power Transfer Unit cuts in when the receiving system pressure falls below 2500 psi. If there is high consumption of hydraulic power on the receiving system, then the PTU operation is continuous.
If there is only system leakage flow, then the PTU barks coming ON and OFF. The ops is normally inhibited on ground when the parking brake is set for standard engine starting at departure. But for any single engine pushback or taxi ops the PTU will wake up.
HorizonGirl From Canada, joined Mar 2005, 781 posts, RR: 17 Reply 21, posted (8 years 2 days 3 hours ago) and read 10073 times:
Thank you so much!!!!!!!!!!
I started this thread and brought up all the old PTU threads
for a school project I was doing on the A320.
I did very well, and I couldn't have done it with out
you all. Special thanks to everyone who gave me extra material and info.
Once again, thank you.
VC-10 From United Kingdom, joined Oct 1999, 3677 posts, RR: 37 Reply 22, posted (8 years 2 days ago) and read 10065 times:
Quoting Klaus (Reply 5): One forum member has once explained that Airbus explicitly wanted to have the PTU sound clearly audible to make troubleshooting on the ground easier. I don´t know if that´s exactly correct, but it might be an explanation. Newer versions are reported to be somewhat less noticeable (also from earlier threads).
It's a novel idea. I would have thought a look at the hyd pressure being generated by the PTU on ECAM would have been a more positive way of trouble shooting