Sometimes I hear the “boing” sound and then they will announce something like the seatbelt sign is off but other times I just hear the sound. Anyone know what the boing means when they don’t say anything about it?
Also I was on an Airbus A320 and on the ground the engines made some really strange sounds I had never heard before - like a loud wailing/siren/squeaking sound. I thought there was a major problem but we took off normally. What was that noise?
Sometimes the ‘boing’ is a reminder. They tell you about the seatbelt status and ‘boing’ the seatbelt sign is on. A boing might be heard in a little bit later, as in “Hey, look at the status above.” I always considered it a reminder.
Sometimes on the ground, different maneuvering at different gates/airports requires different amounts/types of engine power and you might hear a whine/whir you’ve never heard anywhere else.
Different engines can sound different, too. Even on the same model plane, one might have older GE engines, and one might have newer ones.
The loud engine sound was most likely the pilot starting the engines - they are started with compressed air.
The boing may be a signal from the pilot to the flight attendents. How else can they signal them to come to the cockpit?
These can be signals to the cabin crew.
The “boing” minus the seatbelt announcement is probably a passenger using the flight attendant call button to request some sort of service. I’ve been on flights where the flight attendants organized games and the call buttons were used to “buzz in.”
It makes sense that the boing could be a passenger asking for help. Those engine noises I heard must be from a type of engine I have never encountered before.
I’ve noticed on long-haul flights out of the UK, that “bong bong bong” means “we have reached a safe enough altitude for cabin crew to get up and start doing stuff” - presumably it’s from the pilot to the cabin crew, or from the chief steward, who has been notified in some other way, to the other staff.
But the rest of the time, a single “bong” is a passenger pressing the flight attendant button, or the seatbelt sign going on or off.
What you heard may not have been coming from the engines at all. The A320 specifically makes some weird noises prior to engine start. I’ve always assumed they are auxiliary hydraulic pumps charging the accumulators and other such things. Also, you may have been hearing the ground crew closing the baggage doors. Squeaking noises can often be heard as the doors move down into position and the locking pins engage. There may be a bell or alarm that sounds to signal ground personnel to stand clear from the moving door. These are mostly WAGs, as I’ve never worked around airline-type equipment.
I think I may have asked this before - I hear a horrible grinding sound while still on the ground.
GRRRRRRRRRRRRr RRRRR GRRRRRRRRRRRRRRRRRRRRRRRRRR grrr grr
Lasts maybe a few seconds. Sounds like a SAWZALL with a dull blade cutting metal.
What the heck is that?
Closing the cargo doors.
here’s an old thread I started asking a similar question about that “saws-all” noise.
All aircraft have a dog in the cockpit that bites the pilots if they try to touch any of the controls. The A320 has a backup dog that is normally situated somewhere under the cabin floor. The barking type noises you hear at the start of the flight is the backup dog signalling that he’s ready for the flight.
Or if you prefer,
“Boing” sound-one of the female flight attendants flashed her bra at the pilots?
… eh. Your first link talks about Nijas kicking seals and has no real info about what is up. The second link is broken.
What would cause a transfer of hydrolic pressure from one system to another cause such a racket?
The first link tells you about as much as you will be able to find out without reading the maintenance manual. The PTU is a hydraulic driven pump that supplies pressure from one system to the other. I don’t know exactly why the PTU is operates at the start of each flight in the A320. In the Dash 8, the PTU is tested on the first flight of each day, it makes a “clunk” noise. The A320 PTU operates at the start of each flight and makes a dog barking/saw noise. My WAG is that the A320 PTU is either tested manually after start or it operates automatically after the first engine start in response to the lack of pressure in the other hydraulic system. The sound is definitely the PTU though.
Here’s the second link again, fixed.
Any strange sounds can simply be attributed to gremlins on the wing.
In the US, it more specifically means the airplane has reached 10,000 feet, the 250 knot speed limit no longer applies, and the flight crew has lowered the nose to gain speed while continuing to climb at a slower rate. IOW the plane is now level enough to walk around safely.
It can also mean the seatbelt sign is going back on due to turbulence or impending landing.
A PTU is a hydraulic motor driving a hydraulic pump. If you run the motor using hydraulic system A, for instance, and the pump is in system B, you’ve transferred power to system B. Useful if a pump in system B is defunct.
On a 737, the PTU transfers power from system A to B. On most 737s, the logic that turns on the PTU is: System B engine-driven pump pressure is low AND trailing edge flaps are partway out (in a takeoff position) AND airplane is in the air. So the 737 PTU never comes on when you’re on the ground.
On a 757, it’s a bit different, and if the airline is taxiing with one engine (the left) shut down, the PTU will come on to help with steering the nosewheel.
Why is it noisy? All hydraulic stuff is noisy; fluids travelling at high speed under high pressure, rotating machinery running at thousands of RPM, valves clunking on and off, with attendant water hammer effects; it’d be a miracle if it weren’t noisy.
Another cause of a buzzing, chainsaw noise before takepoff is the trailing edge flaps being extended; they’re operated by a hydraulic motor on a 737 (and a 757, too–on a 757, the leading edge slats are run by a hydraulic motor as well).