KeithB
Well Known Member
I?m on Sec 29-08 ? drilling of Cowl Hinge to Firewall flange and Fuselage Side Skin. I have measured and cut the hinge as described on Sec 29-07 including the pilot hole for alignment, then match drilled the hinge as described in 29-08 steps 5 to 7. However, what I get seems to be very poor alignment of the end-most holes on the hinge ? basically a half hole on each end of the hinge rather than a proper ?edge distance?. I?ve measure this at least 5 times and its all correct.
Picture shows hinge on skin, removed from the firewall.
Possibilities:
1. Maybe this is right ? but the half holes on the hinge ends are really hard to machine countersink and rivet and it just does not seem right.
2. Hinge should be lower. Figure 1 on 29-08 would ?suggest? (not totally clear) that the hinge should line up end-to-end with the Hinge Shim and over the 2nd bottom-most skin hole. However, the rivet diagram on 29-16 would suggest that the bottom hole of the hinge is above the 2nd bottom skin hole (2nd lowest hole is AN426AD3-3.5 vs AN426AD3-4.5 for all the others). This would mean the pilot hole spacing and/or hinge length in Sec 29-07 figure 5 is incorrect.
3. Hinge should be higher. Moving up approx 1/4 inch eliminates the ?end holes? and the rivet length in 29-16 is now logically consistent with the thickness difference at the bottom, but the pilot hole spacing and/or hinge length in Sec 29-07 figure 5 is again incorrect.
My vote is #2 ? lower the hinge and lengthen it by about ? inch to match the Hinge Shim and change the bottom rivet to AN426AD3-4.5.
Any advice from you pioneers out in front?
Picture shows hinge on skin, removed from the firewall.
Possibilities:
1. Maybe this is right ? but the half holes on the hinge ends are really hard to machine countersink and rivet and it just does not seem right.
2. Hinge should be lower. Figure 1 on 29-08 would ?suggest? (not totally clear) that the hinge should line up end-to-end with the Hinge Shim and over the 2nd bottom-most skin hole. However, the rivet diagram on 29-16 would suggest that the bottom hole of the hinge is above the 2nd bottom skin hole (2nd lowest hole is AN426AD3-3.5 vs AN426AD3-4.5 for all the others). This would mean the pilot hole spacing and/or hinge length in Sec 29-07 figure 5 is incorrect.
3. Hinge should be higher. Moving up approx 1/4 inch eliminates the ?end holes? and the rivet length in 29-16 is now logically consistent with the thickness difference at the bottom, but the pilot hole spacing and/or hinge length in Sec 29-07 figure 5 is again incorrect.
My vote is #2 ? lower the hinge and lengthen it by about ? inch to match the Hinge Shim and change the bottom rivet to AN426AD3-4.5.
Any advice from you pioneers out in front?