Small holes on the leading edge of horizontal

[motoadve]

Cessna 170B 1953.
I see small holes in the leading edge of the horizontal stab, I think there is 4 of them.
What are those small holes made for?
If installing an abrasion boot , they will all be covered.

[n2582d]

I don't know for certain but my best guess is that they are holes used for alignment pins in the factory's jigs when the parts are formed.

[GAHorn]

I don't know for certain but my best guess is that they are holes used for alignment pins in the factory's jigs when the parts are formed.

Yep, that’s what I’ve always been told. Former Historian (and aircraft engineering consultant) also said this was their purpose.

[cessna170bdriver]

Hmmm… I have always ASSuMEd they were vent holes to reduce condensation inside the surface, but the tooling hole idea makes a LOT more sense.

[n3833v]

I thought some were used to mount longwire antennas.

John

[ghostflyer]

I agree with Miles, I was told to keep them clear of dirt and bugs.

[GAHorn]

I thought some were used to mount longwire antennas.

John

No, ... long wire antennas connected to a ceramic-tower on top of the boot-cowl in front of the windshield, travelled up to the linen/resin post above the windshield, then went aft and passed-through a fitting on top of the rudder and trailed-behind.

HOwever, an ADF “sense” antenna was attached to a “key-slot” cut in the leading edge of the vertical stabilizer.

The small holes were not drain holes or anything other than spigots for assembly-line alignment jigs. (Again, per Cleo and I believe I’ve heard Del Lehman say the same.)