wierd noises on 67 B90

[scubabri]

So we depart out of MKJP and start our climb to 19K and at about 7k I hear this weird noise, kinda sounds like a whining alarm, one that changes pitch up and down, but it's not constant.

I put the plane on auto and ask ATC to maintain 7.5 while we figure out what the hell the noise it. It seems to be coming from the left side.

On a hunch, because it really sounds like an air leak, I dump the cabin pressure and sure enough it stops. I repressurize the cabin and the noise doesn't come back, and after 10 minutes or so we continue our climb with no problems.

The rest of the flight is uneventful.

The flight we took the next day, same thing only this time it starts at about 14K, and instead of dumping cabin pressure, I make the cabin altitude about 9.5 and although it doesn't go away, it seems to no be as bad.

So anyway, the plane is in maintainence, and hopefully they'll figure it out. I don't every have to fly the plane again, but I was wondering if anyone has any idea what the heck the noise was.

It wasn't coming from either of the windows, and mostly seemed to be coming from behind the panel on the left side.

Any ideas?

b

 

[SDdriver]

Cabin leak.

Probably a seal, maybe a door seal. By dumping and re-pressing you probably re-sealed the leak and the noise went away. THat is all that I can think of, unless you have a little animal behind the panel that squeels when you climb cause his ears won't pop..Ha..j/k

Probably a leak somewhere, I would say check the door seal first. I have had 2 fail before.

SD

 

[puddlejumper]

I have had birds build nests up in the blower intake and have noticed strange noises from in there on preflight. I don't think you'd be able to hear them from the cabin at altitude though. You may be able to smell them after they go through the fan!

Seriously though, part of my A/B90 walkaround is to put my ear up to the blower intake and listen for birdies! They really can make a big mess in there.

On the Cheyenne, there's a little hatch covering up the emergency gear extension hand pump. The first time I ever flew it, out of about 6,000' I noticed a distinctive high pitch whine, as you've described. We had maintenance clean up and reseal the weather stripping around the hatch and problem solved! The scary part was that the guy who had flown the plane for 5 months before me had never noticed the squeel! Must be because he had little ones at home. Good luck finding your leak!

-PJ

 

[Gulfstream 200]

has benn a long time since flying King Airs...but id the noise coming from the rear? Is that where the outflow valve is??

 

[scubabri]

You are right, that is where the safety valve is, but this noise was coming from behind the instrument panel on the left side.

 

[KnowledgeSeeker]

On a 67' B-90 the avionics access panel is located right where you are talking about (Left side of nose, just forward of avionics panel). You might want to check the logbooks to see when the last time that panel was opened. Because it can be a popular door to remove and re-install I would take a look at the seal there. Another idea to throw out there...

 

[350DRIVER]

You are right, that is where the safety valve is, but this noise was coming from behind the instrument panel on the left side.

Could be the ghost of a pilot who once flew it and didn't get along with it?


3 5 0

>> sounds like a leak in the pressurization - probably a seal if it is not a ghost.?

 

[eddie]

I don't know much about the kingair, but the Jetstream used to howl from many places. The dv windows would scream and the door changed pitch throughout the flight.

Our mechanics used to put vaseline on the seals to stretch their life. (it worked for about 2 legs)

Good Luck finding the noise!