Non-structural access panels on wings or fuselages fasteners pitch

[eVTOL_fan]

Hello all,

I was wondering if there is a standard best practice for the fasteners spacing when designing non-structural composites removable access panels on wings or fuselages (non-pressurized) normally using camlocks or nut plates. I have in mind that this should be bigger than the one used on primary structure (5D-6D)

I also think we want to minimize the number of fasteners so the mechanic wont spend too much time removing/installing the access panel.

Panels I'm designing are oval shaped and pretty small. Size is 8"x7". I'm using NAS1102-8V csk fasteners with FORCETEC nutplates. Also planning to use liquid gasket to seal the panel to skin joint.

 

[SWComposites]

8-10D is probably a good starting point

 

[rb1957]

I don't have my NAS books with me, but NAS1102 are pretty small, no? 3/16" is normally the smallest screw, and most common with tool kits, and you can get away with a 2" pitch.

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

eVTOL_fan… a few thoughts on this subject...

Be careful about the term 'non-structural'. In military aircraft these panels are considered 'lightly loaded, secondary-structure access doors/panels'.

IF these were truly non-structural, then polyethylene film could be taped-over the opening to keep-out the sun, mud and rain.

Also, be very careful about fastener sizes... 3/16 Dia fasteners with various drive mechanisms are considered 'mandatory'... since mechanics have a unique-way of damaging smaller diameter [delicate] removable parts... over many maintenance cycles... no matter-how careful they are. And these are always a pain to replace or repair the door edges/holes from scratches/gouges, nicks, tears etc.

Also... NEVER directly attach these type panels to primary/critical structure. These should always attach to an intermediary structural element to ensure that panel/fastening damage/failures CANNOT-EVER-NEVER transmit damage to the primary structure.

IF weight saving is a premium, then perhaps the new high-tech 'plasteners' [plastic fasteners] should be considered.

Regards, Wil Taylor
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[Ng2020]

Is it a wet wing? If so, seal integrity will be a major factor in determining fastener pitch.
Have a look Niu, I recall there is some guidance on wing access panel design.

 

[eVTOL_fan]

Thank you guys for the great answers, very helpful. Ng2020 isn't a wet wing, it's an electric aircraft.

 

[eVTOL_fan]

WKTaylor,

Interesting those plasteners, do you have any reference, specs, manufacturer etc.?

Thank you