Originally Posted by BobZ

on the 73n......the telex 850 provides marginal NR. It has impedance matching issues with a number of airframes....you may find yourself unable to transmit, receive, or both..... with no prior indication.

writing this up will result in a mtc sign off of 'pilot used non delta issued headset.' and it is not fixed.

this difficulty seems to be aggravated if both crew members are using 850s.

once you have to fly a 5hr leg with a pack inop....fl 250 @ 330kias.....you will realize how useless the 850 nr really is...once your head stops pounding.

if you entertain ever being on the 73n......get a state of the art active nr headset.

and unless you think safety is not compromised by being unable to communicate with other crewmembers....use the hot mike switch (if installed) or a mechanical device at least from taxi to toc and again from tod to block in.

the 727 was even louder than the 73n.....my hearing is shot, and I have significant tinnitus. wish this technology had been there when I was in your shoes.

The noise levels in the boeing are hazardous to your hearing and effective function as a crewmember. as an aside....the greatest noticeable impact of using active nr on the 727 was how much less fatigued I was at the end of the day.