Granted some airlines prefer to paint their own planes, but we always see planes like the one below, protective coating everywhere but the tail.
Why's that?
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3$\begingroup$ I always found it interesting but never asked why, then I stumbled upon the answer, hence this post :) $\endgroup$– user14897Commented Oct 21, 2016 at 21:51
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1$\begingroup$ This thread is referenced here: youtu.be/daEB-vEzoj0 $\endgroup$– E.P.Commented Mar 10, 2022 at 21:20
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2 Answers
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Excerpt from McDonnell Douglas MD-11 by Arthur A C Steffen:
The remaining eight aircraft were delivered bare-metal with a corrosion protection coating, except for the rudder which has to be painted prior to being installed and balanced, and was completed in the full livery in the carrier's modern paint facilities.
The above text is in reference to KLM's first batch of MD-11's.
The paint has to be applied so the manufacturer can balance the rudder after the added weight of the paint.
That extends to other control surfaces and engine cowls.
For the vertical stabilizer, the minimum requirement is the rudder, but if the airline's logo extends to the rudder, then for colors and shapes alignment the whole tail is painted by the manufacturer.
If the fin was repainted and the operator couldn't afford or didn't have time for the re-balancing, we end up with Frankenstein tails:
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2$\begingroup$ Are all other balanced control surfaces then also painted by the manufacturer? $\endgroup$– J WCommented Oct 21, 2016 at 22:23
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$\begingroup$ That explains painting the rudder, but why the entire fin in the process? In addition, it would seem that the rudder would have to be rebalanced every time that the a/c - or at least the rudder and tailfin - are repainted and refinished. $\endgroup$ Commented Oct 21, 2016 at 22:46
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1$\begingroup$ @CarloFelicione This is true, balanced control surfaces do need to be checked for balance after painting. This is the reason why painting balanced control surfaces is excluded from preventive maintenance, while painting the remainder of the aircraft is included. $\endgroup$– J WCommented Oct 21, 2016 at 22:49
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$\begingroup$ I see. Thanks. I wonder how the handle tail logos or complicated paint schemes the blend from the fuselage into the tail and are not separate. $\endgroup$ Commented Oct 21, 2016 at 23:16
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$\begingroup$ What's the point of balancing a rudder in this context? I can't imagine paint adds any significant weight and how it affects the rudder. $\endgroup$– sweberCommented Oct 23, 2016 at 7:58
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All flight controls must be balanced before an aircraft is flown. Painting changes the weight of the control, and therefore the balance. Flutter can result when this does not happen. Many manufacturers paint and balance the rudder, then install as a matter of process economy.
However, it is not true that all flight controls must be removed from every aircraft in order to be balanced. A Boeing 737's rudder can be balanced while installed, so it could be flown unpainted. The rudder could be painted along with the rest of the aircraft, then balanced in place. The A350 apparently is similar.
