Noisy 767 freighter

[gtseraf]

Hello all

We operate a mixed fleet of B767 freighters, BCF and passenger aircraft.

I have found that the freighter/BCF flight deck noise levels are much higher than the pax a/c with 2 packs running.

When more than flap 1 is set, the noise drops considerably. If one pack is turned off the noise level drops also considerably, to a similar noise level experienced in the pax aircraft.

The intensity of the noise varies from aircraft to aircraft, so I do not think it is a specific freighter/pax aircraft difference.

I have heard that some 767 freighter operators fly with 1 pack on only, as SOP, to reduce this noise level.

Anyone have experience in this or any ideas?

The obvious step of writing up this issue has achieved nothing, maintenance stating that this is normal for the aircraft.

[grounded27]

The obvious step of writing up this issue has achieved nothing, maintenance stating that this is normal for the aircraft.

Complain to your company, write a letter to Boeing, better yet file a complaint with the BBB.

[gtseraf]

Thanks for that

very early here, who is BBB???

[Tazpilot]

Our company flys numerous IAI -200BDSF/-300BDSF converted 767s and is in the process of developing a one pack off procedure that will be approved by the conversion team. This has taken 10+ years to happen and is long over due.

Check with your company in the coming months to see if they can get a copy of this update to the IAI manuals.

[zerograv]

We also have one airframe which is freaking noisy when compared with the other aircraft.

Switch OFF the Left Recirculation Fan and see what happens. It greatly reduces the level of noise.

Switch OFF both Recirculation Fans and .... marvelous, all the noise goes away.

We do it mainly on the ground as, once in the air, the noise becomes a bit more bearable.

Hope this helps

PS. The FCOM goes on to say:
"A slight increase in fuel consumption occurs for each fan that is OFF"

[KBPsen]

It's not unusual to have increased noise after converting the cabin into a class E compartment. It's the fiddling with the ducting and added valves that does it.

[gtseraf]

thanks for the input gents.

BTW, the F and BCF models don't have recirc fans.

[Rollout 63]

We discussed the noise problem for years in our company. Even with one pack off some of the planes were still noisy. Finally they installed a hot intercom
and bought active noise reduction headsets from Bose for all aircraft.
Practical, effective and quick solution.

[Wunwing]

Many many years ago as an apprentice I was working on the first major overhaul of a Boeing707 300C. During our work in the airconditioning bay (snakepit for those who have been there) we found a small dead end duct that was not in the parts manual or the engineering manual so it was removed and the system made as per the book.

During the test fligh the airconditioning noise was deafening.So on return a call to Seattle was made where the American voice asked if we'd removed anything from the snake pit??? I turns out that this was a known problem of induced harmonics and it was countered by a tuned pipe, a bit like a pipe on a pipe organ.

I'd suspect this is the same and when the ducting is altered during the cargo conversion its a case of induced harmonics. The fans just change the air movement enough to alter the frequency to a more acceptable range.Pity the poor dogs if they are carried.

Wunwing