Aeronautical Randomness
Answering mail
July 29, 2015

Three and a half years ago, I wrote a blog post about the “barking noise” on the A320.  In that post, I did my best to explain the source of the noise and when the passengers are likely to hear it.

The post was well received.  According to my stats, it has been viewed over 15,000 times.  Passengers hear the noise and search the internet for answers.  My post provides them with useful information.

Yesterday, I received the following email and wanted to share it with all of you.  My reply to this gentleman will appear below.


Message Body:


The problem with you and other plane technicians that have made light of this subject on this and various websites is because you are used to all sorts of strange noises.
I am an ordinary passenger, you know the sort of person you fly from A to B and help pay all your salaries. Let me tell you I was a passenger on an Airbus 319 recently when I experienced the noise you referred to (quite accurately) as a ‘barking dog’ sound for approximately 10 minutes while taxiing to take-off. I have since discovered that this noise emanates from the PTU (a fuel safety device). I and the majority of passengers around me were scared out of our wits. It wasn’t just the noise, it was accompanied by equally horrendous vibrations (all of which were far louder and exaggerated than on your YouTube film on this website). In fact, nobody seems to mention the vibrations on any of the website blogs I have visited. It wasn’t until we landed some hours later that we all breathed a sigh of relief.
Let me inform all pilots,airlines and airline manufacturers reading this that this is a no! no! for passengers (and I am a seasoned flyer). Let me also give you and all other pilots reading this a tip – before you activate your PTU on an Airbus, verbally inform your passengers so at least they know what to expect and let them be assured (if even mistakenly) that all is under control during the flight they are now locked into. If so called ‘fuel safety devices’ cannot be kept to acceptable noise/vibratory levels they should not be used (or allowed by the licensing authorities). As for any engineers reading this, noise is one thing but the accompanying vibrations I experienced could have no end of unknown effects. In my case when the vibration reached its peak a nearby overhead locker flew open ( coincidence?) but fortunately nothing fell out.
I made a complaint to two separate stewards and was told a senior officer would speak to me on arrival at destination. Nobody spoke to me. On arrival I emailed the airline Customer Relations and informed them that unless I had a full explanation as to the cause of the problem and an assurance that the problem had been sorted I would not travel on that plane on my return flight (which I had pre-booked, paid for and was non-cancellable). The reply I received was that they were unable to give me any information …”as this would be a breach of security procedures”. It could be that the noise/horrendous vibrations I experienced was not the norm, in which case why was I not informed? I got the impression that the airline was hiding something. I used another airline for my return flight. I then decided to check Google to see if there was any information out there and to my amazement there was plenty.

I now await with interest comments by others who have experienced the above or are searching the internet as I did.

Dear Sir,

When I read your email, I honestly couldn’t figure out if you were trolling or looking for legitimate information.  Judging from your own words, you intended your comments to be on public display.  Therefore, I’m a little confused why you filled out the “contact form” that emails me directly.

I agree that the noise is loud and concerning.

However, I’m not really sure how I became part of “the problem” by attempting to educate passengers on the source of the noise.  I flew the Airbus over five thousand hours, but I didn’t build it.  You say I’m making light of the subject?  I believe I accurately and articulately described the source of the noise and the situations when you will hear the PTU.  I used a little humor in mentioning it sounds like a large dog… Is that what offended you?  Funny, because you agreed that I “quite accurately” described the noise as a barking dog.

How much did you learn from my post?  You describe the PTU as a fuel safety device.  It’s a HYDRAULIC pump.

The PTU is an automatic device.  It runs during situations described in my post.  Turning it off would be detrimental to safety.  Also, we cannot make an announcement every time it activates.

You say that the majority of the passengers around you were scared out of their wits?  Did you speak to them?  Did you take a poll?  Since you spent so much time conversing with the people around you, did you consider asking a crew member (flight attendant, NOT steward) if the noise was normal?

I have no idea which airline you were flying, nor the situation they experienced.  Maybe there was more to it?  Possibly.  That’s between you and that airline.  My post only addresses the PTU.

I’m just a pilot who flies airliners and attempts to give the public some insight into our profession.  My biggest concern is arriving safely home to my family after every trip.

If you have any further LEGITIMATE questions, please don’t hesitate to contact me.


Since his email was addressed to the entire aviation community, please feel free to leave a comment.


About author

Renewed Pilot

I've endured a roller coaster career in the U.S. Aviation Industry. Currently flying the 737 on my third try with the same legacy carrier, I have also flown for a regional, fractional and start-up carrier. My piloting experience includes the 737, A320, 727, Citation Excel, Citation Bravo, Saab 340 and many light singles and twin engine aircraft. I reside in the suburbs of Nashville, Tennessee.

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There are 6 comments


    I am guessing the pilots were performing a SET out and forgot to switch on the Yellow Pump or probably not required as per their SOP. No offence to anyone but personally I feel passengers knowing too much without the proper context is just a hassle like the passenger knowing its a PTU but not knowing what it is for.

  • Mike says:

    Days like that you wish you could spray just a little of the chemtrail juice inside of the cabin. 😉

    Seriously though, and a little off topic, I would be interesting in a blog post from your perspective comparing and contrasting the Airbus and the 737. I’ve heard it described as “do you want a better airplane, or a better office?” – but I’d love to read your impressions.

  • Arthur says:

    For the past couple years my wife and I have enjoyed a week long Carnival cruise with our kids for our family vacation every summer. Because of this I’ve started following John Heald on FaceBook (Carnival’s senior cruise director/brand ambassador) and he too posts emails like this almost regularly. Our society today has empowered people to think that those in a service/hospitality type job are somehow slaves of the consumer. This guy is just a rude person who doesn’t realize the world doesn’t revolve around him and the crew are much too busy in the cockpit to be on the pa describing every little thing like a sport casters play by play.

  • Eric Auxier says:

    Great post! Yes, the guy strangely starts with a chip on his shoulder, wrongly directed at you. But, of course, his concern is legit. It sounds like on his flight, for whatever reason, the flight crew taxied out on the number 2 engine (perhaps after an air start?) so the PTU ran continuously. This won’t happen if single-engine taxiing on the Number 1. (I know you know this, but I’m stating it for your audience.) It also often tends to kick on unnecessarily during engine shut down at the gate, and if I happen to notice, I’ll shut it off.

    Yes, it’s a head-scratcher as to why Airbus designed such a noisy, disconcerting (to passengers) system in an airliner, and you rightly put the blame on them, not us! Your commenter also unfairly blames us for not explaining the system on every single flight. Frankly, it simply slips our mind, as we don’t hear it up front! When I remember to, I occasionally explain the PTU in my PA briefing before the flight. I describe it, in simple terms, as a “standby hydraulic pump” that often kicks in during certain situations.


  • David Silver says:

    To all who have replied to my post so far I wish to respond in the order in which they occur:-

    BRIAN:I am not a troll and have no connection with the airline industry whatsoever or any other ulterior reason for raising the subject. I have no intention other than to find out whether my experience on a particular aircraft on a particular flight was a norm or not and if it was not a norm I want to see that something is done about it before it becomes a disaster. If it is a norm then I believe that it is disturbing to passengers and its use should be limited.
    I simply ‘Googled’ the internet to see if there was anyone out there that had a similar experience or could throw some light on the matter. No, you did not offend me, I discovered that my experience was not unique and that you were not the only site on which the ‘Barking Dog’ sound was mentioned ( not surprising as the noise sounds like woof! woof! ). To all Pilots reading this I can only say that the first 5 lines of my blog were written jokingly – no offence was intended. I did make one error in that I described the PTU as a ‘fuel SAFETY device’ – this was a typing error. What I read elsewhere (rightly or wrongly) was that it was a ‘fuel SAVING device’. I sent the blog to you Brian because it was not clear to me how to get it on line as I am not used to this sort of thing.
    Regarding other passengers on board – yes!,we were all very concerned and speaking to each other and more importantly the look of relief on most passengers faces on safely landing was plain to see. When the overhead locker flew open on taxiing to take off a Flight ATTENDANT ran down the isle, slammed it shut and ran back to her seat ignoring our verbal concerns.

    Now if I can address the comments to date:

    CHAITANYA: You missed the point of my query (see below).

    MIKE: If you have nothing to add to a serious enquiry take your internet smiley face to bed and keep quiet, there’s a good boy.

    ARTHUR: No, Arthur it is you who is rude. You entirely missed the point of my posting. I wrote my posting because I am truly concerned about the safety of this aircraft (see below).
    What has ‘what you and your wife have been doing the past couple of years’ got to do with this serious discussion (no, I am not being rude!) ? It would appear that you treat your passengers with contempt whereas you should have been taught to treat them with respect. I am trying to get to the bottom of what could be a serious and possibly life threatening occurrence and you are adding nothing to the discussion.

    ERIC: Congratulations, at least you saw the point of my posting.
    What I suggested was that IF the noise was normal then why not make an announcement to the effect that you are putting on the PTU (call it what you like), no need to explain what it does, just reassure the passengers that there will be some noise and they will then accept that all is under control and O.K. – it is the uncertainty that causes the alarm.

    Now to get down to business. From all that I have read on this site to date it seems everyone is agreed that there is some increased ‘noise’ with this type of ‘plane. I am getting the impression that what the above respondents are referring to and what I experienced are two different happenings. Eric made the statement that it ‘slips his mind as he doesn’t hear it up front’. I can assure you that on the aircraft I was on the noise and accompanying vibration shook the aircraft to such an extent that it must have been evident to any pilot cocooned in his/her cabin. The problem is that one cannot describe comparative noise or vibration levels- these have to be experienced. All I can say is that I am a seasoned and regular air traveller and have never had such a frightening experienced. What I found disturbing was the reply received from the airline – not one of you picked up on this! Did their reply make any sense at all to you? I smell stinking fish – is the smell coming from the airline and /or the ‘plane manufacturer? If what I experienced was a one-off why was it not acknowledged as such and attended to? Not one of you commented on the concomitant severe vibrations mentioned – why? Am I to assume you have not experienced it?

    If I could sit in an Airbus and hear what you all dismiss as being the normal noise/vibration then I would be in a position to say ‘yes’ that is what I experienced and you all could dismiss my concern as being exaggerated. On the other hand if I would say ‘no’, the noise/vibration I experienced was ‘X’ times that, maybe someone would sit up and take notice before something serious happens. Alternatively, if others out there in the ether who have had a similar experience to myself, or have some concerns, make this known, maybe this could contribute to addressing the concerns ( which is the whole point of my taking the trouble to post this).

    • David,

      As I said in my original reply, I cannot get involved in correspondence between you and your airline.

      However, what you describe does sound like more than the PTU.

      Best of luck obtaining the information you’re seeking… But, it won’t be from me.

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