In praise of convenience

​Doing a new panel for your Yak?

How about replacing those funky Russian instrument screws with a Phillips head?

An idea whose time has come !

These Russian panel screws have a 120, (rather than the more familiar 100, 90 or 82 degree) countersink, presumably to contact a greater area on the panel and resist backing out under vibration.

On the Russian original, two perpendicular slots on each screw’s head appear to be shallow arcs cut with a milling tool.

You could grind that arc on the tip of a flat screwdriver blade to try and get those original screws to budge - as long as someone hasn’t already chummed up one of the slots first.

Because then, a bit like Trotsky with an Ice Pick through one ear, and only good one left, the prognosis is not good.

History has shown that the Design Bureau got the applied math of the Yak 52 spot on, pretty much throughout - with fastener design included. 

​Indeed, larger diameter domed head screws with flat slots, found on wing structure, are not problematic to remove. Down at the M3.5 and M4 countersunk sizes however, you’ll encounter a lot of these screws where the slotted surface area simply got smeared by the torquing tool, often with a telltale gouge in nearby paintwork.
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(Decoded: a Philips screwdriver was not the right tool to remove those particular Russian screws.)

​Most Flight instruments in the Yak’s panel take M3.5 size while the Russian Tach takes an M4, but screws of both sizes, with these shallow cross-slotted heads, are to be found throughout the cockpit area.

Wherever you see a gauge surrounded by one slotted head screw and three cross heads, leave the slotted one in place.

The Tri-Gauge, Dual Needle Air gauge, Carb Temp and Manifold pressure gauge are like this - they are packaged as cylindrical cans without a front mounting flange. Undo the slotted screw a few turns and, behind the panel, a wedge moving on that thread is releasing a cylindrical clamp ring, held in the panel by the other three screws.

​Instruments like this slide out forward.

There’s no clear logic as to which instruments have flanges and which use this cylindrical clamp - but doesn’t your beautiful new cockpit deserve panel screws that look like they haven’t been butchered by an Ice Pick?

And being able to work on all instruments, modern or original, with just one Phillips screwdriver....?
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Priceless.