Sealing Pressurization Leaks

[Bob Cook]

GJ

Sure picked a lengthy subject..........

What pressure does your AC hold / at what altitude ?

Can you get max differential of 3.5 ?

There are various sources of leaks. Your mechanic can use a gas powered leaf blower to pressurize the cabin on the ground to determine leaks.


Possibilities are (most likely).

1) seals around cables entries at strut roots and in wing empinage.
2) Poor door seal.
3) rivits
4) seals at bottom of cabin floor.
5) bad waste gate seal.

There have been cases where improper solvents were used when repainting causing leaks around window seals.

You need to systematically eliminate items above.

Other problems could be leaks around venturi on upper deck, seals around heat exchangers.

Later models modified the venturi's on the upper deck take-off to improve pressurization. They did make improvements over time.

Feedback on your performance can help to pinpoint problems.

suggest you make a table such as;

altitude mp rpm cabin pressure differential oat for every 1k feet up to 18k ft . You will probably need 31 inches and 2600 rpm above 14k ft to keep maintain max differential.

I spent a yr getting a '74 to meet spec. Need more info before I can become more specific.

fyi

Bob