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Boudreaux Bob
30th Aug 2014, 16:38
A very interesting story of a fellow who made a very wise decision.

If your helicopter has a sudden change in background noise or vibrations, it is time to find a parking place and figure out what is going wrong.

Of real interest in the story is the comment the Ground Crew heard the "Bang" too.


http://www.rotor.org/Portals/1/ROTOR/Story/Nosie.html

https://www.rotor.com/Publications/RotorsupregsupMagazine/CurrentIssue.aspx

Senior Pilot
30th Aug 2014, 22:31
Just to cut and paste the article (in case the link disappears ;) )

I have been flying the UH-1/BH 205 series aircraft for over 40 years and have logged for nine years. It was May 14, 2014, and I was flying an external-load concrete-pouring job for Trans Aero Ltd. at the Copper Mountain Ski resort in Summit County, Colorado. It was the second phase of a job we had poured previously.

The first fuel cycle was uneventful, and after fueling we started to fly the second cycle. On the fourth load, I heard a sound from the rear of the aircraft that sounded like a small bang. There were no indications on the aircraft instruments that something was wrong and the aircraft was handling just fine, so I came into a hover to see if I could figure out what happened.

Initially, I thought something had simply fallen down in the cabin. Then caution prevailed. I decided to not second-guess myself and landed the aircraft back at staging and shut down.

The ground crew radioed and asked if there was a problem. I told them I heard a bang and was trying to figure out what it was. The ground crew said they also heard it but were not sure what it was.

The initial inspection by the mechanic did not reveal any problems, so I decided to check the tail boom section myself. With a flashlight, I found the longeron cracked aft of the tail boom attaching point. The crack was hard to see if you did not know where to look. We grounded the aircraft and trailered it back to home base.

There are a couple of lessons here that we all need to be reminded of. No matter what your experience level, don’t second-guess yourself. If in doubt, get another opinion. I very easily could have continued to fly the aircraft, and there is no doubt in my mind that would have been a stupid and fatal mistake.

I consider myself very lucky about the outcome. I have close to 22,000 hours and more than 12,000 external-load hours, but remember, no matter what your experience level and flying ability,
the aircraft does not care!

http://www.rotor.org/portals/1/rotor/story/noise.png

Ascend Charlie
30th Aug 2014, 22:42
Well spotted!

Usually the strange noise that increases with airspeed is the seat belt buckle flapping against the fuselage after the ground crew left it hanging out. Some expensive panel work follows.

Or the fuel cap on the end of its chain - before it breaks and falls away.:(

dubbleyew eight
31st Aug 2014, 03:58
in indonesia on a surveying trip in the 70's we had been out doing some winching in the huey to give the raaf pilots some tropical experience.

we were winched out and back up on many occasions.

the next morning early the framie was inspecting the structure of the huey.
he was doing the peer up into the tailcone from the aft cockpit.
all was ok and chipper and as he was clipping the inspection port back in place he realised that the torch he used was still on the seat.

how come I could see everything without needing the torch???
it is usually as black as the ace of spades back in there.

off came the panel again.

how come I can see all the rivets???

took a while to work it out.

where the back of the huey fuselage transitions into the tailcone there was a crack that extended so far around the tailcone that there was only about a foot of skin still holding the tailcone in place.

a very fatal accident averted by the sixth sense of a framie.

all RAAF hueys were grounded until checked.

CharlieOneSix
31st Aug 2014, 12:03
On Christmas Eve 1990 one of our Bell 214ST’s was carrying out night shuttle flights in the East Shetland Basin when at 500 feet and 110 knots the crew became aware of a low amplitude vibration with a frequency somewhere between a “buzz” and a “one per rotor revolution”. There was no associated noise, handling problem or flight deck instrument indication to indicate a malfunction of any aircraft systems.

On reducing speed through 100 knots a pronounced lateral cyclical movement was experienced and persisted until the speed fell through 90 knots. At 80 knots the vibration had reduced to negligible amplitude and this speed was maintained whilst a diversion was set up to the Safe Gothia, alongside Brent Bravo some 20 miles away, where Company engineers and a hangar were available. 80 knot winds were forecast for later in the night.

Cracks were found in the fin root structure around the 42 degree gearbox, in both the left hand side skin and the inclined front spar web fitting, known as the Banjo fitting. The crack in the front spar web had progressed across about 80% of the spar width.

After the event I was told that the maintenance crews on the Safe Gothia were so concerned with the lateral movement of the vertical fin in the heavy seas being experienced that they secured ropes either side of the fin to the hangar walls in case the fin fell off as a result of continued motion of the sea perhaps weakening the front spar web further!

AAIB Bulletin September 1991 (http://www.aaib.gov.uk/publications/bulletins/september_1991_/bell_214st__g_bkfn.cfm)

TeeS
31st Aug 2014, 15:11
If I remember correctly C16, the aircraft was initially cleared for one flight back to base with crew only - then there was a re-think, gulp!

Cheers

TeeS

Non-PC Plod
31st Aug 2014, 17:10
1992, Finals into Bessbrook Mill in a Gazelle. About 300m to run, there was a loud thump, also felt through the cockpit floor and the armoured seat.
After landing, and much searching for the elusive .50cal hole, we found the stabilised binos had fallen from the perch they had been hung from!
Sometimes noises are less bad than you think too!

brett s
31st Aug 2014, 20:47
Had a propane cannon fire right under me as I dropped over a hedgerow while spraying a field - couldn't see it from the back side & I forgot it was there while working another area, that'll get your attention!

Had an FE that thought he heard a funny noise coming from the fwd transmission area of a Chinook, we made a precautionary landing in a parking lot. Turned out to be the retaining latch for the upper cabin door that holds it in the open position vibrating, but better safe than sorry for sure.

Boudreaux Bob
31st Aug 2014, 22:59
At the Pratt and Whitney Engine Plant outside West Palm Beach when the S-76 Sim and Training was done out in the middle of the Swamp, landing by one of the Engine Test Cells could be rather invigorating if you did not know what it was or had a momentary lapse of recognition.:oh:

One could get very light in the seat as you sat bolt upright thinking you were going to be very late for Dinner!:uhoh:

1st Sep 2014, 05:10
The Astazou engine in the Gazelle has a very distinctive sound as it is running down and many a raised pulse in the air has been caused by pilots transmitting 'Complete, closing down' on tower with that same distinctive sound in the background as they shut down.

John Eacott
1st Sep 2014, 06:28
I'm sure this has been a previous topic: these photos are the result of a loud and unexpected bang just as the Alouette III rotated on take off from a pipe yard. The driver (airframe) reacted with commendable alacrity on the assumption that the engine had quit, unfortunately without checking the gauges and things on the panel.

The fire extinguisher had come out of its bracket and fallen on the floor :hmm:

http://www.eacott.com.au/gallery/d/6992-1/AL3+crash+01.jpg

http://www.eacott.com.au/gallery/d/6996-1/AL3+crash+03.jpg

Shawn Coyle
2nd Sep 2014, 16:50
Canadian CH-47C (long time ago) was ground taxiing out after major maintenance. The Flight Engineer, known to be a very picky guy was walking up and down the cabin, listening. He suddenly said - Shut Down Now! and front seat crew promptly complied. When all was stopped, they asked -Why?
Response - I heard a noise I didn't like.
Panels opened and a screwdriver was discovered in the upper driveshaft tunnel busily working it's way through the main driveshaft.
Maintenance officer as well as several senior maintenance personnel were in deep, deep trouble as tool control was suppsed to be very strictly complied with.

Boudreaux Bob
2nd Sep 2014, 22:02
Chinook crews developed very callused knuckles from constantly Vib Checking with a bent finger and checking at strategic places. Over time you get very good at sensing vib levels. Nothing scientific at all....just lots of practice.

Sounds like your FE was of that persuasion there Shawn!