If the aircraft is in the "Transport Category" Part 29 I think you should be aware of this - both operators and maintainers -
For each pilot compartment --
(a) The compartment and its equipment must allow each pilot to perform his duties without unreasonable concentration or fatigue;
(b) If there is provision for a second pilot, the rotorcraft must be controllable with equal safety from either pilot position. Flight and powerplant controls must be designed to prevent confusion or inadvertent operation when the rotorcraft is piloted from either position;
(c) The vibration and noise characteristics of cockpit appurtenances may not interfere with safe operation;
(d) Inflight leakage of rain or snow that could distract the crew or harm the structure must be prevented.
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as amended by Amdt. 29-3, 33 FR 967, Jan. 26, 1968; Amdt. 29-24, 49 FR 44437, Nov. 6, 1984]
To me that means "Thou shall not leak".
I know the current ECD machines are put into a spray rig to be sure they don't leak. 135 doesn't have to comply but the 145 does.
And you are also required to have a side window in this category.
(a) Nonprecipitation conditions. For nonprecipitation conditions, the following apply:
(1) Each pilot compartment must be arranged to give the pilots a sufficiently extensive, clear, and undistorted view for safe operation.
(2) Each pilot compartment must be free of glare and reflection that could interfere with the pilot's view. If certification for night operation is requested, this must be shown by night flight tests.
(b) Precipitation conditions. For precipitation conditions, the following apply:
(1) Each pilot must have a sufficiently extensive view for safe operation --
(i) In heavy rain at forward speeds up to VH; and
(ii) In the most severe icing condition for which certification is requested.
(2) The first pilot must have a window that --
(i) Is openable under the conditions prescribed in paragraph (b)(1) of this section; and
(ii) Provides the view prescribed in that paragraph.
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as amended by Amdt. 29-3, 33 FR 967, Jan. 26, 1968]
Failure to comply means the aircraft is U/S unless otherwise there is some condition to cover these aspects which is approved.
Go and cover all the windows on your aircraft sometime and fly it purely by reference through the "open" side window!!
PS helimutt - Maybe its just the photo but the rest of that 76 looks like a "bucket of bolts" as well!